We measured the emission spectra of the CsI(Na) crystal at different exposure times under gamma ray excitation. The experimental results showed that the energy resolution of the CsI(Na) crystal was worse when the crystal surface adsorbed more H2O molecules, and the crystal surface deliquescence decreased the luminescence efficiency of the CsI(Na) crystal. We studied the band structure, density of states, and optical properties changes caused by H2O molecule adsorption on the CsI(Na) (010) surface. The generalized gradient approximation (GGA) was used to describe the exchange and correlation potential between the electrons. Our calculation results showed that the band gap width of the CsI(Na) (010) surface decreased after adsorbing H2O molecules, while three new peaks appeared in the valence band, and the absorption coefficient decreased from 90,000 cm−1 to 65,000 cm−1, and the reflection coefficient decreased from 0.195 to 0.105. Further, the absorption coefficient was reduced by at least 25% because of H2O molecule adsorption, which led to the luminescence degradation of the CsI(Na) crystal.We investigated H The time-dependent photoluminescence and radioluminescence of CsI(Na) single crystals exposed to 50% and 75% relative humidity were investigated by other researchers; the experimental results [2O molecules changed the state and structure of the crystal surface and affected the scintillation characteristics, especially those of the film crystal. Studies [Cesium iodide doped with sodium (CsI(Na)) crystal has been used as a charged particle detection material since the late 1960s  due to ipsulated . Delique results  show tha Studies .2O molecules. The band structure, density of states, and optical properties affect the scintillation performance. In this paper, we measure the pulse height spectra of the CsI(Na) crystal with different air exposure times and different air humidity environments under γ ray excitation and investigate the effect of the CsI(Na) crystal surface absorbing H2O molecules on the scintillation degradation. We use Cambridge sequential total energy package (CASTEP) software to calculate band gap, density of states, and optical properties with the aim of determining the key factors leading to CsI(Na) crystal surface scintillation degradation after the absorption of H2O molecules.All these facts result in the surface structure changes of the CsI(Na) crystals and the degradation of the CsI(Na) surface scintillation after the CsI(Na) crystal surface absorbs H2O molecules are adsorbed on the CsI (010) surface and CsI(Na) (010) surface; those structural models are shown in 2O molecules are adsorbed in addition to Na+ because the hygroscopicity of the CsI(Na) crystal is caused by the doping of Na+ ions that easily adsorb H2O molecules.The crystal structure of the CsI is a cubic crystal system, and its space group is Pm3m. The calculations performed in this investigation were completed by the Cambridge Sequential Total Energy Package (CASTEP) loaded on Materials Studio 8.0 software. CASTEP is an ab initio quantum mechanics package based on density functional theory (DFT), it was originally developed by Cambridge University, UK. Instead of ion potential, the planar wave pseudopotential method is used to expand the electronic wave function. The exchange correlation between electrons is described by local density approximation (LDA) or generalized gradient approximation (GGA). GGA is adequate for large density gradient systems; the optimized configuration is more consistent with reality. The GGA approximate ultra-soft method in the form of PBE (Perdew Burke Ernzerhof) is used to optimize the crystal structure of the CsI and CsI(Na) crystals. All the initial lattice parameters used for calculations came from experiments.−6 eV/atom, and k sampling is a 5 × 5 × 5 k-point mesh in the Brillouin zone. We confirmed the optimal atomic positions when the following criteria were satisfied: 1. the maximum force on the atomic positions is smaller than 0.05 eV/nm; 2. the maximum change in the energy per atom is smaller than 1.0 × 10−5 eV; 3. the maximum displacement is smaller than 0.001 Å; and 4. the maximum stress on the crystal is smaller than 0.02 GPa. We calculated all the properties based on the crystal structure optimization.GGA PBE tends to underestimate the band gaps, so we chose the Heyd–Scuseria–Ernzerh (HSE) ,10,11 hy137Cs- and 60Co-radiate γ rays with energies 662 keV, 1.17 MeV, and 1.33 MeV. The CsI(Na) crystals are coupled to a photomultiplier (PMT) using silicone oil as a coupling agent. The emission peak wavelength of the CsI(Na) crystals is 420 nm, so we chose the photomultiplier  with a 420 nm peak response wavelength, which matched the CsI(Na) crystals well. The photomultiplier tube coupled to the crystals converts the input light to electrical signals, which are then amplified and processed in the tube socket and multichannel analysis unit . We used the spectrum analysis software  to adjust the HV and gain of PMT on the computer to acquire and analyze the detector spectrum. The crystals and PMT were assembled in a lead box for light shading and ray shielding. In our experiments, we used commercial CsI(Na) crystal materials  with 5% mol Na-ion doping concentration and measured the γ ray-excited emission spectra of crystals with the setup shown in 2O molecules, we exposed CsI(Na) crystal to 25% relative humidity air at 15 °C temperature and 85% relative humidity air with different exposure time. 137Cs-662 keV γ ray excitation.In order to investigate the CsI(Na) crystal scintillation degradation caused by the crystal surface adsorbing HThe luminescence efficiency variation of the CsI(Na) scintillators and the luminescence linearity of the crystal under different energy ray excitation tend to affect the detection performance in the actual detection process, and the energy resolution reflects the result of the combined effects of these two factors. Energy resolution characterizes the ability of nuclear radiation detectors to distinguish the full-energy Gaussian peak of γ photons with similar energy and is an important index of a detector. For incident particles with different energy, the smaller the energy resolution value of the detector, the lower the overlap degree of full-energy Gaussian peaks, which indicates the detector has a better ability to distinguish rays in complex multi-radioactive radiation field. 137Cs, and we calibrated the channels with the 60Co γ-ray (1.17 MeV and 1.33 MeV) energy spectrum measured simultaneously. The measurement time of each energy spectrum was 1000 s. The formula used for the energy resolution was FWHM/E.In our experiments, the energy resolution was obtained for the 662 keV photoelectric peak of In our experiments, we used two different sizes of CsI(Na) crystals, Φ50 mm × 29 mm and Φ25 mm × 50 mm. We performed the measurements at room temperature. Firstly, we measured the energy resolution of the CsI(Na) crystal (Φ25 mm × 50 mm) at 25% relative humidity. As can be seen from However, when the CsI(Na) crystal (Φ25 mm × 50 mm) was placed at 85% relative humidity, the experimental results in 2O molecules, the formed “dead” layer affected the luminescence efficiency, which broadened the spectral curves in 2O molecule adsorption caused by the Na diffusion away from the crystal, which left behind “dead “regions with an activator (Na) concentration below the lowest limit for scintillation (0.01%) [We measured the energy resolution of another CsI(Na) crystal with a size of Φ50 mm × 29 mm at 85% relative humidity; the energy resolutions were 12.90%, 14.22%, and 14.19% when the exposure periods were 0 h, 8 h, and 10 h, respectively. The experiment results show the energy resolution worsened with a longer exposure time; this worsening trend was the same as that of the CsI(Na) crystal with the size of Φ25 mm × 50 mm. The scintillation performance of the CsI(Na) crystal decreasing monotonically was reported in the literature [0 = b0 = c0 = 4.827 Å and a0 = b0 = c0 = 4.503 Å, and the angles for all crystals were α = β = γ = 90°. These lattice parameters of the CsI crystal were in good agreement with the results in reference [We optimized the geometry of the CsI and CsI(Na) unit cells to study the electronic structure and optical properties. The optimized lattice parameters for the supercells of the CsI and CsI(Na) were aeference , while t2O molecules was about 0.973 Å, the O–H bond angle was 103.946 degrees, the O–H bond length of gaseous water molecules was 0.97 degrees, and the bond angle was 104 degrees. The surfaces of the CsI (010) and CsI(Na) (010) were optimized geometrically, and it was found that the surface atoms had varying degrees of relaxation. We used a molecule-in-a-box type of calculation to calculate the energy of a single water molecule. The dimensions of the box were a0 = b0 = c0 = 4.827 Å, the same as the lattice parameters of the CsI crystal, and we set a vacuum layer with a size 1.5 times the lattice around the single water molecule to avoid periodic interactions between that molecules. The results for geometric optimization of supercell and gaseous H2O molecules were identical to the theoretical values, which indicates that the selected model is appropriate and the calculation method is feasible [In the model, the optimized O–H key in Hfeasible ,17.2O molecules adsorbing on the CsI and CsI(Na) surface are shown in 2O molecules on the surface of the CsI (010) can be defined by the Formula (1) [2O molecule is adsorbed on the surface of the CsI (010) or CsI(Na) (010), 2O molecule, and The simulation models of Hmula (1) :(1)ΔEads2O molecules. This phenomenon is consistent with the theory that the CsI (010) surface has no deliquescent properties. However, on the CsI(Na) (010) surface that adsorbed H2O molecules, the bond length RO-H and bond angle AH-O-H of the molecules increased, which indicates that the interatomic force of H2O molecules decreased while the activity increased.The calculated results of two models in CsI(Na) crystal is a luminescence efficient scintillation crystal for radiation detection. When an electron in scintillator atoms receives energy from the incident particles which deposit larger energy than its forbidden band width, the electron is excited to the conduction band from the forbidden band. Then, it returns to the ground state and emits photons in the process of deexcitation. Therefore, the band structure and the density of state distribution are closely related to the characteristics of the scintillator after it is stimulated. We calculated the band structure and state density of the CsI and CsI(Na) crystals based on the geometric optimization model.2O molecules. In other words, H2O molecular adsorption influences the band width and the electron density of state distribution, and that in turn affects the electron excitation process.From 2O molecules. As we can see from the TDOS of the CsI(Na) crystal in 2O molecules, and small peaks appeared at −3 eV, −5 eV, and −21 eV; the conduction band and the valence band increased some exciton bands near the Fermi level. Through PDOS analysis, we can see that the conduction band was composed of I’s 5S orbit, Cs’s 5S and 5p, and 2S and 2p orbits of Na. In the valence band, the three new peaks induced by H2O molecules near the Fermi level contributed to the TDOS changes in the CsI(Na) (010) surface that adsorbed H2O molecules.In order to further study the formation of band structures, we calculated the electronic densities of states of the CsI(Na) (010) surface, which can explain the cause of band structure changes in detail. 2 parameter for the CsI(Na) (010) surface starts from 2.5 eV, but starts from 1.5 eV after adsorbing H2O molecules, and their optical band gaps were 2.9 eV and 2.1 eV, respectively. These results are in good agreement with the calculated band structure. The first peak value before adsorption was about 6.75 eV and after absorption peak was located at 14 eV. It is worth noting that the energy difference between the 6.75 eV peaks and 14 eV peaks was 7.25 eV. After adsorption, the CsI(Na) (010) surface had two absorption peaks at 6.1 eV and 13.75 eV.2O molecules were shown in 2O molecules were zero. This shows that the relative energy of these photons is transparent. The absorption coefficient of the CsI(Na) (010) surface was 90,000 cm−1, but decreased to 66,000 cm−1 after adsorbing H2O molecules. The movement of the low energy end caused the electronic transition to be accomplished by only absorbing smaller energy, which eventually led to the tendency of the absorption spectrum to be moved to the low energy end (red shift). We can see that the H2O molecular adsorption was greatly reduced by the photon absorption of the CsI(Na) surface, which resulted in the scintillator detection efficiency decrease. Our result is consistent with the experimental results. For 500 nm thick CsI crystal, when it is under long term exposure (24 h), the absorption peak broadens with the band center shifting toward lower wave numbers [2O molecules were adsorbed on the CsI(Na) (010) surface, the red shift of the reflection coefficient peak was observed, and the reflection of the photon was weak; the reflection coefficient decreased from 0.195 to 0.105. From this point of view, the adsorption of H2O molecules decreased the luminous efficiency of the CsI(Na) crystal.The absorption coefficient of a material indicates the light intensity attenuation percentage of the light wave propagating in that medium. In this paper, the calculated absorption coefficient of the CsI(Na) (010) surface that of the CsI(Na) (010) surface adsorbing H numbers . The cal2O molecules on the CsI(Na) (010) surface can affect the luminescence performance of the CsI(Na) crystal and discuss which factors induce crystal property changes resulting in the luminescence reduction, we measured the gamma ray spectra of the CsI(Na) crystal under different exposure conditions to investigate the luminescence efficiency changes after the adsorption of H2O molecules on the CsI(Na) (010) surface and optimized the structure of the CsI(Na) (010) surface to study the band structure, density of states, and optical properties using a first-principle calculation method based on DFT. The experimental results show that the energy resolution worsened with increasing crystal exposure time. This indicates that H2O molecules adsorbing on the CsI(Na) (010) surface caused the luminescence degradation. The calculation results reveal the changes in the band structure and optical properties of the CsI(Na) (010) surface because of H2O molecular adsorption. Our calculation results verify the experimental results and explain the scintillation degradation of CsI(Na) and highlight the importance of surface preparation for CsI(Na) crystal detectors. It is crucial to explore the luminescence efficiency effect caused by H2O molecular adsorption, especially for crystals that readily experience deliquescence such as NaI(Tl), LaBr3(Ce), and SrI(Eu) crystals.In order to explain how adsorbing H


Sulfate erosion is a major cause of concrete durability deteriorations, especially for the service tunnels that suffer sulfate erosion for a long time. Accurately predicting the concrete damage failure under sulfate erosion has been a challenging problem in the evaluation and maintenance of concrete structures. Here we design the dry–wet cycle test of service tunnel concrete under sulfate erosion and analyze the Elastic relative dynamic modulus (Erd) and mass under 35 times cycle periods. Then we develop an autoregressive integrated moving average (ARIMA) prediction model linking damage failure to Erd and mass. The results show that the deterioration of concrete first increased and then decreased with an extension of the dry–wet cycle period. Moreover, based on a finite set of training data, the proposed prediction approach shows high accuracy for the changes of concrete damage failure parameters in or out of the training dataset. The ARIMA method is proven to be feasible and efficient for predicting the concrete damage failure of service tunnels under sulfate erosion for a long time. With the popularization of concrete material, people began to use concrete material for infrastructure construction on a large scale. Concrete has also become the second most utilized building material after water . Because2SO4 and MgSO4 solutions to evaluate the changes in mass, loss of mechanical strength, and linear expansion, which were reflected in the change in concrete length, loss of mass, and compressive strength [Different from sulfate corrosion, sulfate erosion refers to the reaction between a sulfate medium and hydration reactants in concrete to form new hydrates. The newly formed hydrate expands and finally destroys the structure. The most common minerals produced inside sulfate-eroded tunnel concrete are gypsum and ettringite . The evostrength .Although many scholars have focused on concrete sulfate erosion and explored it through experimental methods, the prediction of concrete damage failure for in-service tunnels is limited. The ARIMA model was a time series prediction method proposed by Box Jenkins in 1976 that could be applied to small samples . The ARIIn this article, according to the essence of corrosion, the elasticity relative dynamic modulus (Erd) and the mass of the concrete are taken as the basic indexes of damage and failure of concrete specimens ,25. ServIn this article, the Erd of the concrete is calculated by using the tested propagation velocity to reflect the degree of damage inside the concrete through the correlation between the propagation velocity of ultrasonic pulse in concrete and the degree of damage inside the concrete. A three-dimensional hierarchical analysis method was used to process the relevant data and obtain the improved Erd after optimization. The subsequent damage failure time of the prepared service tunnel concrete specimens was predicted using the ARIMA model after the optimization of experimental data. The prediction results can provide some reference for the damage development and damage degree of concrete in a tunnel.This research is based on a service highway tunnel in Chongqing, China. The highway tunnel fully opened in 2006, and it has a design life of 300 years. However, in 2015 and 2018, there were a lot of disasters. As shown in In The change of the Erd of concrete can reflect the deterioration and compactness of the internal structure. When there are holes and cracks in the concrete, the ultrasonic wave will bypass the defects, resulting in an increase in sound propagation. When the concrete is eroded by sulfate, the porosity and compactness inside the concrete specimen are changed, which causes the change of ultrasonic speed . TherefoThe acoustic parameter oscilloscope adopts a transmitting transducer to continuously transmit ultrasonic waves to the concrete. The ultrasonic nondestructive testing device is the acoustic parameter tester HS-CS4EL  according to the (China Concrete Ultrasonic testing instrument verification regulation for ultrasonic nondestructive testing of concrete (JJG-070-2006)) . The ultThe tunnel sulfate corrosion of the secondary lining part of the core was made into a 50 mm × 100 mm cylindrical test block. Polycarboxylate high-efficiency water reducing agent (SP) was used as the admixture. The concrete strength and design mix ratio are shown in We used a dry–wet cycle experiment to accelerate sulfate erosion. The degradation mechanism of concrete blocks in the accelerated experiment is consistent with that of concrete in service , so it iThe concentration of sulfate suggested by the Chinese standard (Standard test method for long-term performance and durability of ordinary concrete (GB/T 50082-2009)) is 5% for the evaluation of concrete . Table 2As the corrosion aging process inside the concrete is not uniform, there is a difference in the corrosion degree in each direction. In this test, the acoustic velocity in five directions was obtained for each test. We divided the test block into four equal parts and marked it. The circular arc probe was used to measure the transverse sound velocity, and the plane probe was used to measure the longitudinal sound velocity in five directions in total. At present, most acoustic wave tests only measure one direction, and there is a large error, so we use a three-dimensional analytic hierarchy process (TAHP) to improve it by measuring acoustic wave data in multiple directions to correct and reduce the error. The calculation formula is as follows:3); The Chinese standard(Standard test method for long-term performance and durability of ordinary concrete (GB/T 50082-2009)) stipulates that when the Erd is reduced to 60%, it is judged as the failure of concrete specimen . BecauseAn electronic scale with an inductivity of 0.01 g was used to test the mass loss of concrete after each dry–wet cycle. Referring to the experimental method in the Chinese standard (Standard test method for long-term performance and durability of ordinary concrete (GB/T 50082-2009)), when the mass loss of concrete reaches 5%, the concrete is judged to have failed . The calp, d and q, where p is the order of the AR term, q is the order of the MA term, and d is the difference order required to make the time series stable.The ARIMA model is a model established using the difference method to obtain stationary data from non-stationary data in the ARMA model. It includes the AR model, MA model and Difference (I) method. ARIMA has three characteristics: The difference method eliminates the changes on the level of time series, and it is necessary to differentiate the unstable data for the prediction of the ARIMA model. To ensure the effective use of data, the model can extract useful information by a second-order difference at most. Among them, the first-order difference and second-order difference can be expressed mathematically by the equations:k refers to the correlation between the observed data with an interval of k time periods. In the expression of the PACF function, k = 2 is taken. K is the total number of model parameters; N is the number of observations; t and the moment (t − k). The PACF eliminated the influence of other random variables. It simply measured the correlation between time series data and lag value.The test of data stability is an important step in time series analysis. The autocorrelation function (ACF) and partial autocorrelation function (PACF) of the autocorrelation graph are used to test the data stability. ACF is the correlation between the former time series data and the present time series data. It describes the linear relationship between the observed values at the moment p and q of the model. AIC based on the concept of entropy is a standard to measure the optimal fitness of statistical models. It encourages the optimal fitness of data fitting but tries to avoid overfitting. BIC is a basic method in statistical pattern recognition. Both AIC and BIC used the penalty likelihood criterion. Compared with AIC and BIC, BIC imposes a greater penalty on the model. Thus, BIC will obtain a more simplified model.The minimum criterion method of Akagi Information Criterion (AIC) and Bayesian Information Criterion (BIC) was used to determine the order The ARIMA model needs to carry out a residual test to ensure that the order is appropriate. The residual test includes a QQ-plot (quantile-quantile plot) test and a Dubin–Watson test. The QQ-plot test is used to intuitively verify whether a set of data is normally distributed. If the sample data deviates too much from the line, an unreasonable model will be shown. The Dubin–Watson test is the test statistic of the residual autocorrelation of the diagnostic model proposed by Dubin and Waston.The prediction accuracy is evaluated by the mean absolute error (MAE), mean absolute percentage error (MAPE), mean square error (MSE) and root mean square error (RMSE).(1) The concrete samples we used were drilled from an in-service tunnel that had been eroded for some time. The prepared concrete specimens were numbered B1 and B2. They were drilled from different parts of the tunnel. Their internal erosion is different, so B1 and B2 are two completely independent concrete specimens. Then, we put them into the designed sulfate solution. The sulfate corrosion was accelerated by dry–wet cycles. The cycle period is 24 h, of which 16 h is the soaking period. We put it into the soaking box with 2% and 10% sodium sulfate solution to ensure that the concrete specimens were fully soaked. The temperature was set at 20 °C, and the relative humidity was 95%. After soaking for 16 h, the concrete specimens were taken out and put into the electric air drying box for drying, and the drying temperature was set at 60 °C.(2) Then, we took the specimens out and placed them in a ventilated place to cool to room temperature. The four directions and axial directions from the concrete test block’s side were taken for ultrasonic nondestructive testing. The first wave method was used to measure the longitudinal ultrasonic speed of the concrete specimen during the ultrasonic nondestructive testing. To ensure the accuracy of experimental data and reduce the systematic errors generated in the instrument, experimental environment and first-wave pickup, the plexiglass test block with the same size as the specimen was used as the calibration test block during the test in this experiment . When anThe acoustic coupling phenomenon will affect the transmission of ultrasonic waves in the detected object and affect the detection result. Therefore, a coupling agent (honey was used in this paper) was used on the inspection surface to enhance the penetration ability of ultrasonic wave .(3) Repeat steps (1) and (2) for a cycle after the single measurement. It is not until the completion of 35 cycles that it can be found that the concrete test block has produced significant erosion and cracks on the macro level.(4) We used the AHP method to process ultrasonic nondestructive testing data, the processed Erd data and the MASS data into the computer, Erd database and mass database input ARIMA model. The ARIMA-Erd prediction model and ARIMA-Mass prediction model were constructed and run. Finally, the output variables of the prediction model were obtained. The superiority and statistical significance of the model were analyzed by AIC, BIC, ACF and PACF.(5) MAE, MAPE, MSE and RMSE were used to evaluate the prediction accuracy of the experimental results, and the results obtained by the output variables after the model was established were analyzed and discussed.The mass was measured 35 times in the experiment, with the first 30 times for analysis and the last 5 times for predictive testing.In The combined ultrasonic speed of 35 dry–wet cycles tests were obtained, and the Erd were calculated.2SO4 solution. The corrosion of B2 was relatively slow, and the internal expansion product accumulation rate was also slow. When the specimen B1 was immersed in 10% Na2SO4, the change of ultrasonic speed was the most obvious.In Because of the different sulfate concentrations, the amount of sulfate ions in the solution that entered the concrete in the same time was different. The Erd of specimen B2 decreased in the first three cycles of drying and wetting. This was because the concentration of B2 erosion solution was low, and the generation rate of internal expansion products was less than the damage of the specimen in the soaking and drying cycles. Therefore, the Erd decreased accordingly. With the increase in the number of dry–wet cycles, the internal expansion product accumulated. The accumulated amount was greater than the damage amount of the soaking–drying cycles. After the descending stage, B1 and B2 showed an obvious upward trend due to the continuous accumulation of expansion products. After the 24th dry–wet cycle, the expansion products were generated in large quantities to produce an expansive force, and the internal compactness of concrete decreases. A large number of expansion products will also produce micro-cracks in the specimens, which will promote the degradation of concrete, resulting in the decline of Erd of B1 and B2.p and q values of B1 and B2 ARIMA models were obtained by AIC and BIC ordering methods.In order to ensure that the order of the ARIMA model was consistent, ACF and PACF graphs were used to test the stationarity of the model again. After the difference of the model, it can be seen that the ACF autocorrelation functions tend to be 0 in the end. The number of sharp red sites in the PACF figure is greatly reduced, and the value is also decreasing. It proves that the model has become a stationary time series after the difference, and effective data has been input into the model.By comparing the mass prediction and the Erd prediction, it can be found that the final trailing of the mass prediction tends to be 0. The Erd still tends to be slow after the difference. According to the stationary analysis, the mass prediction is selected as the better model for damage failure prediction.In order to check whether the ARIMA model conforms to the application of prediction, the residual test is carried out.P-value of the late sites did not significantly exceed the expected value, they were close to the expected value. Therefore, the analysis model was reasonable. The D-W test shows that the D-W value of the two models is close to 2, so this model does not belong to the autocorrelation model.In P-value of these sites should be consistent with the expected value. In the upper right corner of the graph are the sites with high significance, which are potential candidate sites associated with traits. These points are located above the diagonal; that is, the observed P-value of the site exceeds the expected value. This indicates that the effect of these sites exceeds the random effect, which, in turn, indicates that these sites are significantly correlated with the traits. This also means that the mass prediction represents a better model choice.When selecting mass prediction and relative motion prediction, it can be seen that the lower-left corners of the QQ-plots of mass prediction are the sites with low significance; that is, the sites that are not associated with traits are determined. The observed p and q are all less than 2; thus, the ARIMA model is a low-order model. It shows that the mass prediction model has an obvious trend of change. Therefore, the fluctuation of B1 in the mass prediction is small, and finally, it is transformed into a quasi-linear line. When the Erd prediction model adopts the first-order difference, the values of p and q are 5, and then the ARIMA model is a high-order model. This indicates that the change trend of Erd is not obvious, and there is obvious oscillation. Therefore, according to the previous experimental training data, the forecast curve is oscillating at the beginning and then smoothing out at the end.Through the exercise of the previous experimental training data, the prediction curves of B1 and B2 were compared. It can be found that for both the mass prediction and the Erd prediction of B1 within 30 times, the Erd loss value of the specimen is 60% (mass loss is 5%). At this point, the sulfate attacks the concrete to the point of damage and failure. However, the prediction curve of B2 is slow, and the failure times of sulfate erosion loss are about 70 times. This is due to the different sulfate concentrations of B1 and B2, the erosion rate of B1 is obviously greater than that of B2, and the predicted failure times of B2 are also greater than that of B1.According to the prediction results, the mass loss of B1 is predicted to reach 5% after the 59th dry–wet cycle to reach damage failure, and the mass is only 403.3 g. The Erd of elasticity decreased to less than 60% after the 53rd dry–wet cycle and reached loss failure, with a time span of 6 times. The mass prediction of B2 stops after the 103rd dry–wet cycle, and the mass loss reaches 5% to reach the loss failure. The Erd stops after the 101rd dry–wet cycle and drops below 60% to reach the loss failure. The time span is two times. Therefore, it can be mutually verified that the optimization effect of the model is good, and the prediction results are accurate. The difference in damage failure time between the two methods is not big.Based on the mass of the ARIMA time series and the accuracy of the Erd prediction model were compared. The results of mass prediction and Erd prediction are given in According to The reason is that in the case of a small number of samples, the variation trend of mass loss prediction is simple and presents less volatility. The variation trend of Erd loss prediction is complex and has high volatility, which requires the development of a large number of optimized control parameters and a relatively large training database.This paper introduces in detail the method of sulfate erosion loss failure of in-service tunnels combined with mass nondestructive testing, ultrasonic nondestructive testing and the ARIMA computer learning model. According to the proposed method, the study of sulfate erosion loss failure of concrete in-service tunnels can be divided into three stages. The first stage is to retain the corrosion inside the concrete of the service tunnel and conduct the dry–wet cycle sulfate erosion acceleration experiment. In the second stage, ultrasonic nondestructive testing and mass nondestructive testing are used to obtain the mass data and Erd data of concrete specimens, and the mass database and Erd database are established. In the third stage, ARIMA is used to establish the mass loss failure model and Erd loss failure model.In this study, interesting results about sulfate loss failure of in-service tunnels are given:1. Through the mass nondestructive testing and ultrasonic nondestructive testing of concrete specimens, we found that, with the increase in dry–wet cycles, the mass loss rate of the specimen showed a trend of decreasing slowly and then increasing rapidly after leveling off. The Erd decreases in the early stage due to the damage of the soaking–drying cycle, and increases rapidly in the later stage, then decreases slowly after leveling off.2. Through the ARIMA model stability, residual test, MSE, MAE, RMSE and MAPE and other judgment basis, we can confirm that the ARIMA model can accurately predict the failure time of sulfate erosion of concrete in an in-service tunnel.3. The proposed methods of computer learning and nondestructive testing can serve as prototypes for future practical applications. It has reference significance to judge the timely protection of the secondary lining of the tunnel in service and whether it needs to be dismantled.


The objective of this study was to investigate the physico-chemical properties of concrete made with recycled brick-concrete aggregate, which was the mixture from waste concrete and waste clay brick in a 7:3 ratio. Specifically, this paper investigated the mechanical properties, freeze-thaw resistance, and distribution of water-soluble chloride ions of concrete containing RBCA and fly ash (FA) against combined freeze-thaw and sodium chloride attack. Concrete containing RBCA replacement of natural coarse aggregate and fly ash replacement of Portland cement was subjected to 45 freeze-thaw cycles containing sodium chloride solution. It was discovered that the mechanical properties and freeze-thaw resistance to sodium chloride attack gradually decreased with increasing RBCA content. At the same time, a replacement level of 15% FA by weight resulted in significant improvements in compressive strength and resistance to combined freeze-thaw and chloride attack. Furthermore, using a replacement of 30% FA by weight markedly improved the resistance to chloride ion penetration of concrete due to the lowest water-soluble chloride content. As industrial growth and urbanization continue, the cumulative amount of construction solid waste grows rapidly. In the last five years, the utilization rate of construction solid waste in Japan, the Netherlands, Germany, and Denmark has reached 80% or more, whereas, in China, the utilization rate is only around 47.7% . As a reIn general, recycled aggregate degrades the performance of concrete, as demonstrated by a significant number of scholars ,5,6,7. T2, and then ITZ is enhanced. Finally, concrete performance was enhanced wholly because the permeability of the constituent materials determined the permeability of concrete. Kou et al. [In real environments, structural failure is not only caused by inadequate strength but also caused by a combination between mechanical and durability of deleterious issues. Concrete durability was adversely influenced by many physical effects, including wear of frictional surface, cracking on account of pore solution crystallization, faced with the atrocious circumstance in temperature , and detrimental chemical effects, including lixiviating of the cement paste because of acidic solutions  and expau et al.  stated tu et al.  extracteu et al. ,27 also A good deal of research on the mechanical properties and durability of concrete made with waste concrete aggregates may exist. However, research regarding the deterioration of concrete composed of recycled brick-concrete aggregate (RBCA) is limited in the literature and mainly focuses on the mechanical properties ,29,30,31As a result, in this study, the recycled brick–concrete aggregate (RBCA) was made from waste concrete and waste clay bricks in a ratio of 7:3. Mechanical properties and durability (frost resistance and permeability) of concrete with RBCA were investigated, and the influence of RBCA and FA under the combined action of cyclic freeze-thaw and chloride attack. Furthermore, the phase compositions of recycled concrete were determined using microscopy and X-ray diffraction.An amount of 42.5R Ordinary Portland cement (OPC), in conformity with Chinese standard GB175-2007 , which rClassification of particle size was based on standard ASTM C125. Washed river sand in the range of 4.75 mm (No. 4) and 0.15 mm (No. 100) was used as the fine aggregate. Crushed limestone in the range of 31.5 mm  was used as supplementary cementitious material.3, and a sand ratio of 0.34. There were two different percentages of RBCA . The RBCA was made of waste concrete and waste clay bricks in a ratio of 7:3. There were three different percentages of FA . The actual concrete mix proportions are exhibited in Concrete was manufactured with a water-binder ratio of 0.4, the binder material of 450 kg/mThe preparation process of specimens complied with the standard ASMT C192. Add coarse aggregate, partial water, and the solution of the polycarboxylate superplasticizer into the mixer. Then, start the mixer and add cementitious material, fine aggregate, and remaining water. Mix in the mixer for 3 min, rest for 3 min, and mix for another 2 min to mix them evenly. Prismatic specimens 100 mm × 100 mm × 400 mm and cube specimens 100 mm in size were cast in plastic molds, removed after about 24 h, and cured for 28 days at 20 ± 2 °C with a relative humidity of at least 95%. Prismatic specimens were used to assess frost resistance, while cube specimens tested compressive strength. Axial compressive strength tests were performed in conformity to ASMT C39, and test results were determined to be the mean values of every 3 specimens.2) to ensure chlorine penetrates from the reserved erosion surface when immersed in saline solution (MLR is the mass loss rate (%); 0m is the initial mass (g); nm is the mass of a concrete prismatic specimen that underwent n freeze-thaw cycles (g). RDEM in % is the relative dynamic elastic modulus of concrete; f0 is the initial transverse frequency (Hz); nf is the transverse frequency of a prismatic concrete specimen that underwent n freeze-thaw cycles (Hz).The rapid freeze-thaw process was in accordance with ASTM C666. Prismatic specimens of 100 mm × 100 mm × 400 mm were cured for 28 days before being immersed at 1 mm depth in water for 7 days. Five surfaces were sealed with epoxy resin glue  and (4), respectively. The silver ion of AgNO3 solution reacted with the chloride ion to form silver chloride, and then excess silver ion interacted with chromate ion of K2CrO4 solution to form peach precipitation. Chloride ion content was measured by recording the consumption of the AgNO3 solution. The water-soluble chloride content (WSCC) was calculated via Equation (5).WSCC is the water-soluble chloride content of concrete (%); CAgNO3 in 0.02 mol/L is the concentration of AgNO3 prepared; V is the AgNO3’s consumption of titrations (mL); V′ is the amount of distilled water was used to dissolve the powdery sample.The sampling diagram is depicted in The compressive strength of concrete with different recycled aggregate content at 28 days depicted in Some differences emerged, by comparison, the values of the R80 and R100 series in Trends on the strength curve of concrete with different mix ratios exhibited the same . When thAs shown in The MLR increased as the number of freeze-thaw cycles and the amount of RBCA in the concrete grew, and its value directly represented the extent of concrete spalling. In the case of R100, the MLR of concrete containing 0, 15%, and 30% FA had increased to 6.4%, 5.6%, and 6.2% of their initial value in the sequence, respectively, whereas in the case of R80, the counterpart values were 6%, 5.1%, and 5.7%, respectively. According to the results, 15% FA reduced MLR to a minimum of 5.1% after 45 freeze-thaw cycles in a 3.0% NaCl solution. Additionally, the MLR of concrete without FA was somewhat greater than concrete containing 30% FA.In the instance of the R100 series, RDEM grew as fly ash content increased, while the R80 series curves pattern remained consistent. The vertical distance between two curves in concrete without FA b shows tThe surface WSCC value was larger than the interior value, which stabilized at a depth of 30–40 mm. That was due to a superficial sample in contact with the solution directly. In the early stage, chloride ion penetration in the concrete specimens was dominated by capillary absorption, and the penetration rate was fast . The difSEM microscopy was used to examine the microstructure of concrete containing RBCA. After undergoing a 3%NS-45FT treatment , the conDifferences in microstructure were also detected see a–d, withAfter 45 freeze-thaw cycles, concrete specimens containing 80% RBCA had a denser matrix than those containing 100%, but specimens containing 15% FA were inferior to those containing 30% FA. This suggested that concrete with 15% FA was more susceptible to chloride attack, whereas concrete with 30% FA exhibited stronger chloride ion penetration resistance. Generally, microscopic characteristics matched macroscopic examination results (WSCC test).2, originating from sand, was the most prominent, followed by Ca(OH)2, AFt (3CaO·Al2O3 CaSO4·32H2O), and Friedel’s salt . The presence of Friedel’s salt in the XRD graph suggested that the chloride salt had penetrated the matrix and reacted with the AFm phase [2 phase to form C-S-H, a reaction that appeared to be related to the chloride ion’s physical adsorption capacity [X-ray Diffraction (XRD) patterns were used to determine the phase composition of concrete containing RBCA that was subjected to sodium chloride solutions during freezing-thawing cycles. As presented in Fm phase ,41. Morecapacity ,43,44.The replacement of virgin aggregates with RBCA composed of 30% recycled brick aggregate and 70% recycled concrete aggregate led to a decrease in 28 days compressive strength. The R80 series concrete had a margin of increase of 2.2–7.9% than that of R100 series concrete. The best dosage of FA in combination with recycled aggregate was discovered to be 15%;When the RBCA content increased from 80% to 100%, concrete specimens were susceptible to more damage based on the increased MLR and sharper reduction in RDEM. The concrete MLR was lowest with 15% FA, while RDEM loss was lowest with 30% FA. The addition of 15% FA improved the resistance of concrete following 3% NS-45FT, while the RDMA of various RBCA concrete varied according to the amount of FA;All WSCC followed the same trend, decreasing within 30 mm of the sodium chloride-eroded surface, recovering slightly, and reaching a constant value in the area beyond 30 mm. The chloride penetration resistance of concrete containing 30% FA was the best, owing to the concrete’s low WSCC value.Concrete containing RBCA and FA were evaluated comprehensively after being subjected to a combined 3% sodium chloride solution and 45 freeze-thaw cycle regime (3%NS-45FT). Based on the compressive strength, mass loss rate (MLR), relative dynamic elastic modulus (RDEM), water-soluble chloride content (WSCC), SEM, and XRD, the following conclusions can be made:


Polymer composites have been identified as the most innovative and selective materials known in the 21st century. Presently, polymer concrete composites (PCC) made from industrial or agricultural waste are becoming more popular as the demand for high-strength concrete for various applications is increasing. Polymer concrete composites not only provide high strength properties but also provide specific characteristics, such as high durability, decreased drying shrinkage, reduced permeability, and chemical or heat resistance. This paper provides a detailed review of the utilization of polymer composites in the construction industry based on the circular economy model. This paper provides an updated and detailed report on the effects of polymer composites in concrete as supplementary cementitious materials and a comprehensive analysis of the existing literature on their utilization and the production of polymer composites. A detailed review of a variety of polymers, their qualities, performance, and classification, and various polymer composite production methods is given to select the best polymer composite materials for specific applications. PCCs have become a promising alternative for the reuse of waste materials due to their exceptional performance. Based on the findings of the studies evaluated, it can be concluded that more research is needed to provide a foundation for a regulatory structure for the acceptance of polymer composites. The growing climate challenges and the scarcity of new natural resources in construction projects have moved the research momentum towards sustainability. The concept of a ‘circular economy’ (CE) has become one of the effective ways of achieving long-term sustainability ,2,3. TheTypical concrete has some drawbacks, such as utilization of natural resources in an excessive quantity, low compressive properties at an early age, and environmental hazards ,14,15. GPolymer concrete is a construction material made from a monomer/aggregate product that has been polymerized. The aggregates are bound together by the polymer matrix monomer, and the produced composite is known as concrete. The idea of polymer concrete started in the late 1950s. These materials were designed to be used as a substitute for cement in specific construction applications. Polymer concrete was first used for construction cladding and other applications. It was widely adopted as a repair material afterward due to its fast cure time, superior bonding properties, ability to reinforce steel, improved strength, and toughness ,25. Poly2 emissions. The accessibility of raw materials, the performance of the system, and the latest synthesis results all support the use of the polymer concrete model for the development of sustainable infrastructure materials. Reports have been published on a variety of curing methods, such as ambient temperature curing, elevated temperature curing, and water curing. The earlier studies have shown that after one day of soaking at room temperature, polymer concrete reaches about 70% to 75% of its strength. Normal concrete normally produces a 20% strength gain after one day of curing [Waste materials from steel industries are also rich in calcium and silica resources, which are important for the production of various calcium silicates and also mineralogical forms of calcium silicate. Rice husk and bagasse are examples of biomass waste that can be turned into ashes, which contain around 80–90% amorphous silica. For polymer concrete applications, this amorphous type of silica can save money. It is a known fact that waste materials such as fly ash from power stations have excellent pozzolanic characteristics and are being replaced by 30% in cement manufacturing. Moreover, fly ash in amounts up to 100% is being used as a building material owing to a process called geo-polymerization. The synergistic strategy to reuse industrial waste will serve as a model for developing building materials that reduce COf curing ,40. In pf curing . Composif curing ,44,45,46Review the potential advantages of polymer concrete composites for the climate, then present a summary of the most important results concerning their mechanical properties, such as compressive, flexural, and splitting tensile strength.Examine the durability performance of polymer-modified concrete under a variety of adverse climatic conditions, and study its structural properties based on research findings.Collect data from earlier studies that used SCMs and industrial byproducts to partially replace conventional concrete for a better comparative analysis of their mechanical properties and then propose rankings that will help with the selection of SCM products for sustainable concrete production.This review study aims to:Agricultural, municipal, and industrial wastes are used as supplementary cementitious materials in making polymer concrete. The physical and chemical properties of the used waste materials were comprehensively studied and analyzed in terms of their pozzolanic properties for potential use in sustainable concrete ,48.50) [Many researchers have investigated the incorporation of the industrial waste (IW)-I product rice husk ash as a cement substitution or as a fine aggregate (sand) in concrete structure projects ,52,53,5450) . Convers50) .2/g in comparison with a RHA particle size of 95 2/g. Another research study reported the highest compressive strength of 51.8 MPa with a RHA particle size of 11.5 Detailed studies have shown that the size of the particle, its specific surface area, the W/C ratio, and the cement substitution level influence the cementitious properties of RHA. Similarly, it was reported that the impact of the specific surface area of RHA quite often overwhelms that of the particle size ,60,61. Gr manner . Compare50, BET SSA, and SiO2. The experiment was performed at a cement replacement rate of 20% RHA and a w/c ratio of 0.5, and higher modification ratios were applied using the abovementioned formulas. The findings show that RHA’s pozzolanic contribution changes with the average particle size, the grinding time, the w/c ratio, the SSA, and the cement substitution dosages of RHA, as displayed in For analysis, the experimental results provided by Zunino and Lopez  were useFurthermore, the optimum pozzolanic output was observed at a 30% substitution level of cement with an average particle size of 14.467 er study . AdditioFor all median-size particles, researchers  measured actions ,62,64,65Moreover, close attention should be paid to the production line and molecular structure together with the other concrete/cement additives used in RHAC to increase RHA’s pozzolanic efficiency in concrete ,66. The 3S  and C2S  differs with the type of cement and the quantity of Jamil et al.  revealedoduction . The stuThe usage of RHA as a SCM in the production of concrete can result in negative effects, such as decreased flowability, a high-water demand, flow blockages, and increased requirements for superplasticizers. A significant reduction in the concrete’s strength at a high level of RHA, low chloride permeability, and the ASR mechanism in alkaline solution are also stated. All such crucial consequences can be minimized by a thorough study of rice husk ash and the RHAC design phase and the use of suitable RHA content in concrete applications.The industrial waste (IW)-II product silica fume (SF) has also been used for numerous construction purposes and utilized as a cement additive and filler material and for curing purposes ,75,76,77The incorporation of the industrial waste (IW)-III product fly ash as a cementitious material in concrete and in different applications has been studied by several researchers ,89,90,91The adverse effects of high-volume fly ash concrete (HVFAC) include increased setting times, low strength at initial stages, project delays, cold weather concreting issues, and low resistance to sodium silicate salt carbonation . To prevThe industrial waste (IW)-IV product ground-granulated blast furnace slag (GGBFS) is used in geopolymer concrete (GPC) and alkaline-activated slag (AAS)-based cement production ,99,100. 2CO3 and H2SO4 are the benefits of using waste glass (WG) [The industrial waste (IW)-V product waste glass (WG) can be used as a SCM or a filler in a variety of applications, including ultra-lightweight fiber-reinforced concrete (ULFRC) and burned bricks ,113,114.ass (WG) ,120. Theass (WG) ,121,122.ass (WG) . ThroughAn activation process is required to avoid a gradual increase in or low strength at initial stages and to intensify the cementing properties of SCMs in the production of green concrete. Among other benefits, it will gain long-term durability at early or later stages . The act2SO4), sodium silicate (Na2SiO3), and acids 2, K2SO4, TiO2, calcium formate) are a few chemical activators that have been reported in prior studies and used in sustainable and green concrete. Chemical activators may be incorporated into a milling process or coupled with temperature-monitored activation to lessen the overall cost of materials [2SO4 addition produced greater strength in comparison with simple activation [To enable the reactivity of the concrete materials, temperature activation tends to refer to temperatures above room temperature. Air and water are common activation channels used during activation driven by temperature. Activation mediated by a SCM requires the utilization of a SCM to intensify pozzolanic effects. Glass particles activated at a high temperature (50 °C) generate pozzolanic actions that also depend upon their composition . The paraterials . For exativation .2 content, less alkali, an unreactive carbon footprint, a good grindability index, a smaller particle diameter, higher strength, and the development of microstructural features [3 by sonication increased the hydration rate, setting period, and compressive strength of SCCs. Intake of colloidal nano-silica achieved a decrease in the initial and final setting times and sometimes increased the CS. Quicklime (CaO) was suggested for high-volume fly-ash-based applications in another study because it provides a significant benefit to both the initial and older-age strength of concrete [Chemical activation has such benefits as a decline in the setting period, strength at early ages, a reduction in material costs, excessive SiOfeatures ,131,132.features ,134. Thefeatures  confirmeconcrete . The intconcrete . Lithiumconcrete .2, and GGBFSS. Bernal et al. [SCM-controlled activation was used to increase the bond strength, limit the setting time, attain initial and final-age strength, and lower the bond strength ,142,143.l et al.  proposedl et al. ,125.2CO3, which was derived from the results in terms of CS. In fly-ash binders, they also found that the SiO2/Na2O ratio and its pH tend to play a key role in cement-based matrix activation and binder strength creation. De Vargas et al. [2/Na2O played an important role in the creation of a geopolymer concrete with FA in terms of improved CS, composition, and microstructure. If the CS concentration rises, the molar concentration rises as well, resulting in longer curing or heat curing times. The inclusion of 5% silica fume to replace the slag in AAS pastes enhanced the compressive strength up to a temperature of 800 °C for SCM-controlled activation [The output of mechanical activation depends upon the activation type used according to a study conducted by Kumar et al. . Their as et al.  found thtivation . Due to tivation .In AAS blends for SCM-controlled activation, adding 5% SF as a substitute for slag increased the compressive strength up to a temperature of 800 °C . BecauseThe polymer concrete production process varies as it depends entirely on the composite materials to be used as well as the target strength. The authors of  proposedThe performance of particle packing by a granular inspection of all structural members is one of the evaluation techniques that can be used in green concrete ,153. OthThe slump test is used to determine how compacted concrete behaves in a cone when subjected to gravitational force. This test is also a measure of the strength of the fresh concrete. Bentz et al.  suggesteConversely, Keertana and Gobhiga  found thThe increased water absorption and high specific surface area of RHA material resulted in a reduction in slump . This coThe amount of time it takes to transport, place, and compact concrete is known as the setting time . It was Based on the shape and quantity of FA used during concrete construction, researchers  found a The strength properties and workability of a RHA-blended concrete mix were improved with the incorporation of up to 30% RHA as a cement replacement according to a study by Ikpong and Okpala . The ini3; sand content, 40%; normal SCM content, 500 kg/m3; UPFA content, between 30% and 40%; and a suitable amount of superplasticizer. Generally, proper consideration should be given to ensure that the SCC is capable of keeping its desired fresh properties, such as flowability, permeability, prevention of segregation, reasonable viscosity, and the ability to flow under its weight by using an aggregate of small size.Fresh properties of SCC produced with ultra-pulverized fly ash (UPFA) have also been examined and should satisfy the following criteria: slump test, 240 to 270 mm; slump flow, 600 to 750 mm; and L-box test, 35 to 80 m/s, as recommended by Xie et al. . When thRHA generated by unregulated burning could be used in new residential building projects according to . ConcretWorkability refers to the ability to handle, place, compact, and finish a concrete mix . The add3, 400 kg/m3, and 450 kg/m3, the flow values were found to be 670–880 mm, 670–740 mm, and 670–780, respectively.Hot weather conditions influence the characteristics of fresh cement pastes and concrete . Similar3 was developed to prevent a rapid initial concrete setting time and a substantial strength reduction [A waste solid within the range 0.37 to 0.41 with a cement content of <400 kg/meduction . The woreduction . The numeduction . It is aeduction . Likewis2, 80 N/mm2, and 79 N/mm2) by incorporating SF, RHA, and SF with nano silica [2 after curing for 28 days. The inclusion of lime in HVFAC and a binder in geopolymers is used to attain their CS efficiently [For a better comparative analysis, the compressive strength (CS) observed in various green concretes by various authors is presented in o silica ,204. SF iciently . Due to iciently ,204. Theiciently . Variousiciently . Likewisiciently . Chindapiciently  documenticiently ,223,224.2 with cement + RHA + Nano A + PPO by the quaternary method. This result is supported by another study that used OPC + 20% of FA + 1.5% of steel fibers + a water-reducing admixture. Later on, they used cement + FA + RHA with the ternary method. Walczak et al. [Many articles on the flexural behavior of green concrete can be found in the literature, as shown in k et al.  observed2O3 (NA). These synergistic interactions also activated the superior properties of the steel fiber mortar. The prestressed steel-fiber-reinforced concrete in beams attained the second highest flexural strength, which showed a similar pattern. This means that the addition of fibers strengthens the energy absorption efficiency of structural members and increases their overall flexural strength. The flexural properties of concrete can be improved by using various fibers, such as reinforced fibers, polypropylene fibers, and nano-Al2O3, as reported in several studies [The highest flexural strength was achieved using a steel fiber mortar made with polypropylene fibers, RHA, and nano-alumina. Polypropylene fibers increased the compressive strength of the mortar paste by creating a bridging effect, increasing the fracture energy and thus the flexural qualities of the mortar. Conversely, the capacity of the concrete matrix to load the fibers was improved by nano-Al studies ,212,213.Authors have reported that shrinkage is increased with increasing brick dust content because brick dust can absorb water . It was The authors of  reportedThe need for pre-wetted LWAs in HVFAC was proposed by Barrett et al.  to triggThe use of quaternary cement mixtures  was suggested by Serdar et al.  to achieBased on research, it has been proven that the addition of fly ash causes a decline in creep because of the increase in the modulus of elasticity, which also leads to a reduction in the volume of the paste in the concrete . For cemTo prevent shrinkage, Yang et al.  proposedMoreover, it was observed that an improved pozzolanic and pore refinement effect produces a significant reduction in the water absorption and void ratio with an increment in the waste glass powder addition . A studyIn addition, when the polymeric percentage of concrete is increased, impact on water absorption and porosity has also been discussed ,251,252,Considering the different curing conditions, the compressive strength of the cement mortars made from different combinations of PC, GGBS and PFA at different curing ages. It shows that with the increase in duration of curing time, the CS increase with the increase of GGBS and PFA content for mortar development  and are The replacement of rice husk ash in concrete improves its resistance to chloride attacks . It was SF shows superior resistance to chloride ion attacks (40% and 14.3% higher than that of RHA). Both were replaced at similar percentages (5% and 10%) with a w/c ratio of 0.6 and tested after 3 days of curing . A decreHPC was prepared with combined mix proportions of 25% RHA and 10% SF . The res2 and alkaline content), the percentage of SCM, the form of the alkali–aggregate interaction, the amount, and the cement’s fineness [Siddique and Bennacer  reportedfineness . SCMs mifineness .2O) < 3 kg/m3 were observed in another study. Their findings were verified in another study that showed that RHA created by controlled incineration had a stronger ASR inhibitory action similar to that of the remaining RHA induced by uncontrolled burning [However, contrary findings on this RHA effect on ASR in concrete have been documented in another study . To cont burning . A reducMoreover, it was observed that SF is more useful for controlling the expansion of ASR in mortar as compared with RHA . A partiectively ,123,268.ectively . FA and ectively . In conc2CO3. The authors also mentioned that the color scheme of the glass had no major effect on the ASR and the thermal stability [Researchers  found thtability . They suThe author of  studied At <300 °C, SF had a significant impact on excess CS. In SFC using 10% SF as a cement substitute, the strength retention was 84.1%, 85.2%, 68.8%, and 26.8% at temperatures of 100, 200, 300, and 400 °C. At 6 percent of cement replacement, the strength quality was higher than the average values of 84.1 percent, 85.2 percent, 68.8 percent, and 26.8 percent . The los2 at a replacement percentage of 70% with OPC at a 400 °C temperature in the development of HVFAC. It was lower in comparison with the 67 N/mm2 and 52 N/mm2 for SF content in stimulated alkali paste as observed by the author under similar temperature conditions [Rashad et al.  observednditions . In addtnditions . At temp2 to 24.9 N/mm2. At the same temperature, control samples showed a 54.7 percent reduction in CS. The disparity in microstructure in both the HSC and control specimens was linked to the degradation of HSC, which incorporates 9 percent SF by weight of cement. A negligible reduction in CS at 100 and 400 °C and a serious decline at 400 °C (approximately between 55 and 80 percent) was reported. The authors of [2 and about an 11 percent decrease in volume under a high temperature of 800 °C in comparison with untreated control specimens. The increase in CS was due to its low water absorption, the availability of a significant amount of void space, and possibly the solid content ratio.At an elevated temperature (800 °C), HSC produced with SF at 15.4 percent and FA with a cement replacement of 38.5 percent showed a significant reduction in CS of 74.4 percent from 97.3 N/mmthors of  confirmethors of  claimed 2SiO3 to KOH was 2.5 and in the case of the FA/activator ratio 2.5 was recommended. Both the polymerization reaction and sintering are responsible for an improvement in the strength of GPs at high temperatures. Another research study [2 in the GP-blended cement paste, melting of the glass fibers, and greater incoherence in the mortar and sand were all linked to a loss of strength.For fire safety and performance improvement in GPC, the FA/activator ratio was found to be the most significant factor. The desired ratio of Nach study  confirmech study  recordedAccording to , incinerWhen GGBS is used as a sand substitute in an alkali-activated slag (AAS) mortar, researchers  demonstrConcrete made of fine glass waste as a sand replacement was given the highest CS in comparison with coarse WGC and WGC containing a mixture of both fine and coarse particles . The bes2SO4, 20% of the cement be replaced by RHA. The acid attack resilience was directly related to the ratio of (SiO2 + Al2O3 + Fe2O3)/CaO. RHA’s increased resistance was also attributed to its dense microstructure, its structural and pozzolanic effects, and the existence of Al2O3. A 25% RHA cement substitution with 0.1H2SO4 resulted in a strength increase [In binary cementitious products, RHA has a higher resistance to a sulfate threat than FA. Despite this, the RHA mortar’s strength improved by 7% after 90 days of immersion in a 5% solution of sodium sulfate and a 20% cement alternative, which compares favorably to 0% for FA  In compaincrease .2, 53.5 N/mm2, 56 N/mm2, and 61.5 N/mm2 to a better Blaine fineness of 3000 cm3/g, 3900 cm3/g, 4800 cm3/g, and 9300 cm3/g, respectively [4) and ferric oxide inside the concrete structure [3A) content has been used [The immunity of FA and SF to several chemicals  has been investigated . The autectively . The opttructure . Chemicaeen used .3S and C2S is attributed to the creation of portlandite, which promotes the penetration of sulfate when extracted and produces spacious ingredients (gypsum and ettringite). Similarly, GGBS outperformed FA in terms of resistance to a MgSO4 attack due to its higher CS2 content [3 or CaSO4 [The chemical susceptibility of GGBS in the presence of lime is determined by its high toxicity, the amount of Ca in the cement matrix, and its dispersion within that sample . GGBS ou content . In conc content . Moreoveor CaSO4 . Compareor CaSO4 . Despiteor CaSO4  claimed or CaSO4 . Glass for CaSO4 .According to Ganjian and Pouya , when ex2 emissions and using substitutes in cement production, can help in polymer-modified concrete. Two institutes of international repute (Heidelberg Cement and RWTH) have developed an ecofriendly concrete concept using olives and basalt. Using carbonized minerals for the development of construction materials will be helpful. Two institutes, Heidelberg Cement and Aachen University-RWTH, are supported by the Potsdam Institute for Advanced Sustainability Studies (IASS) and the Dutch start-up Green Minerals for this research [Materials produced by following an environmentally friendly ideology, such as reducing COresearch . Figure A major challenge in the development of polymer concrete composites is ensuring compliance with regulatory standards. Other challenges include minimum clinker concentrations, the chemical characteristics of cement, the insufficiency of the data available in the literature over the last 20 years, and the diversity of polymer concrete applications. Therefore, more research is required for a better understanding of polymer concrete’s behavior . As a reRegulations and inexpensive technology for the efficient development and manufacturing of polymer concrete and relevant information are needed to support and understand the introduction of new standards and regulations . To raisSimilarly, innovative and economical activators are needed to promote the long-term advancement and production of PCC. Characterization methods that are both cheap and economical are also desired, particularly in developing economies where funding for research and development is limited. Construction firms, academic institutions, and research centers should be paid to pioneer the manufacture and use of polymer concrete composites in their construction projects. Moreover, new research hubs should also be established to support the continued advancement of polymer concrete materials and construction methods. Domestic production techniques should be supported in order to generate low-cost green composite materials and decrease dependency on costly technology. One of the most productive, economical, novel, and sustainable strategies to boost the effectiveness of concrete buildings is to use waste materials as well as alternative composites, e.g., SCMs and coarse aggregates, in polymer concrete production.Polymer concrete composites are made from different types of industrial, municipal, and agricultural wastes. Polymer concrete composites are identical to normal concretes; however, they are made entirely of polymer matrices rather than cement and contain two co-binders, namely mineral cement and a high proportion of polymer. Owing to variations in the development goals, capabilities, and ability levels of the local construction industry, the strategies adopted in each country to promote the use of polymer concrete in buildings will be different. Polymer concrete composites, which incorporate waste products and modern, substitute materials such as SCMs and aggregates, constitute one of the most effective, inexpensive, advanced, and ecofriendly ways to improve the quality of concrete buildings. Polymer concrete composites can be used in large-scale construction projects all over the world. Proper measures and cooperation between building organizations are actively needed to promote the concept of sustainable concrete in construction. Besides this, more demonstration projects, as well as further research and development, are needed to develop environmentally friendly material binders to minimize the need for OPC. For the building industry, polymer concrete is strongly advised due to its natural, technological, and economic advantages.Moreover, future research should focus on the following. Guidelines for the advancement of resources for polymers that endorse industrial waste could be developed for use across the world. Based on the sources of raw material and the mineralogical nature of industrial materials, a precise model framework for polymer concrete could be established. Due to the disproportionate emission of carbon during the cement manufacturing process, the contribution to global warming of cement factories still alarms environmentalists. As a result, supplemental industrial or agricultural wastes can be used as a raw material to minimize energy consumption. Under the circular economy model, industrially focused polymer design parameters could be defined to establish region-specific and raw resource materials.


Antibiotics are miracles of science and critical for many surgical procedures. However, the emergence of multidrug resistant pathogens resulting from inappropriate antibiotic use is a threat to modern medicine. This study aimed to determine the appropriateness of antibiotic use, cost, consumption and impact of an antibiotic stewardship intervention round in a surgical ward setting.Baseline antibiotic utilisation was determined with a retrospective cross-sectional study in two surgical wards in a tertiary academic hospital in South Africa where medical records of 264 patients who received antibiotics were reviewed. In the second stage of the study, records of 212 patients who received antibiotics were reviewed during a weekly antibiotic stewardship intervention round. The volume of antibiotics consumed was determined using defined daily doses (DDDs)/1000 patients’ days, and the appropriateness of the antibiotic prescription for treatment was also determined using a quality-of-use algorithm.There was a reduction in the volume of antibiotic consumption from a total 739.30 DDDs/1000 to 564.93 DDDs/1000 patient days, with reduction in inappropriate antibiotic use from 35% to 26% from baseline to antibiotic stewardship programme stages, respectively. There was an overall increase in culture targeted therapy in both wards in the antibiotic stewardship programme stage.The implementation of an antibiotic stewardship programme led to a reduction in antibiotic consumption and improvement in appropriate use of antibiotics. A United Kingdom (UK) study predicted that if left unchecked, ABR will claim an extra 10 million lives annually causing the global economy a loss of over US$ 100 trillion by 2050.3 Hence, the urgent need for implementation of successful antibiotic stewardship programmes (ASP) to slow down resistance to antibiotics and conserve last line treatments.Antibiotics are a precious resource whose discovery has transformed modern medicine by playing a critical role in the fight against infectious diseases and decreasing mortality caused by bacterial infections.4 therefore, surgeons need to use antibiotics prudently. Despite advancements in prevention and control of infections, surgical site infections (SSIs) have remained leading cause for mortality and morbidity.5 Patients with SSIs are more likely to be readmitted with a higher risk of death, than those without these infections, they also require longer hospitalisation and incur considerable increases in healthcare costs.5 Optimising antimicrobial use before, during or after surgical procedures is critical in addressing ABR, simultaneously reducing the burden of infection globally.6 This requires a systematic approach by way of antibiotic stewardship to optimise rational antibiotic use. A limited number of studies have been conducted to determine the appropriateness of antibiotic therapy in surgical settings, especially in developing countries.7 Hence, the need to involve surgeons in ASPs. An Egyptian study demonstrated that engaging with surgeons with interests in rational antibiotic prescribing to educate their colleagues, can improve optimal antibiotic use for surgical prophylaxis in hospitals.8Many surgical conditions like diverticulitis, appendicitis and cholecystitis are infectious in nature, and often treated with antibiotics,9Antimicrobial stewardship has been described as:C]oordinated interventions designed to improve and measure the appropriate use of antimicrobial agents by promoting the selection of the optimal antimicrobial drug regimen including dosing, duration of therapy, and route of administration. (p. 323)[9 The main aim of ASPs are to ensure that patients receive appropriate antibiotic therapy, improve clinical response, with reduced adverse outcomes.10 Antibiotic resistance is a direct function of antibiotic use, as the volume of antibiotics consumed increases, so do the chances of developing resistance by bacteria as a survival mechanism.11 Over-consumption of antibiotics is a major driver of ABR,14 therefore, appropriate consumption in an ASP helps improve management of antibiotic utilisation.15 Apart from reducing the emergence of resistance, ASPs are also associated with reductions in drug acquisition cost, toxicities and infections caused by pathogenic bacteria such as Clostridioides difficile.16 To help address the effects of ABR and optimise antibiotic use, the South African Antibiotic Stewardship Programme (SAASP) has published a pocket guide to help prescribers.17An ASP involves several strategies with different approaches, which when properly implemented will improve patient outomes.18 An initial implementation of ASPs in South African public and private hospitals led to a reduction of antibiotic consumption,21 and also resulted in antibiotic cost reduction.20 However, they were implemented in medical ward settings and did not specifically address ASPs in surgical wards. This study aims to determine the appropriateness of antibiotic use, cost, consumption and impact of an antibiotic stewardship round in a surgical ward setting.A survey to assess the level of implementation of ASP across continents has shown that in Africa only 14% of hospitals had such programmes in place, compared to 53% in Asia.Charlotte Maxeke Johannesburg Academic Hospital is a tertiary academic teaching hospital of the University of the Witwatersrand, providing a wide range of specialist care and serves as a referral hospital for many hospitals in the Gauteng province and all over Africa. The study was conducted in the vascular (395) and general/gastroenterology (396) surgical wards of this hospital.The study was conducted in two stages as follows.n = 264) in the study wards from February 2016 to May 2016. The variables assessed included: age, gender, diagnosis, indication for surgery, types of antibiotic used, indication, dosage, route of administration, allergy, nature of specimen collected for culture and sensitivity, and biomarker results. These biomarkers included: procalcitonin and C-reactive protein to guide and monitor antibiotic therapy. Results from the National Health Laboratory Services (NHLS) database were used to complement pathology results obtained from patient records. The total volume of antibiotics consumed was determined using defined daily doses (DDDs)/1000 patient days.23 The number of DDDs for each antibiotic was determined by converting the total amount of that antibiotic used over a given duration into grams and the result was divided by the standard World Health Organization (WHO) DDD value of that antibiotic in grams. The appropriateness of antibiotics used for therapeutic purposes was determined using a guideline developed by Gyssens et al.24 The appropriateness of surgical prophylaxis was determined based on the recommendations of the SAASP,17 and Essential Medicines Lists for South Africa.25 Each prescription was compared to what should be the best practice according to these guidelines and assessed against the Gyssens’ categories to determine whether they were appropriate or not . An independent sample p = 0.01). The average length of hospital stays (LOS) was significantly increased in the ASP stage (p = 0.01). In the baseline stage, amoxicillin/clavulanic acid was the most frequently used antibiotic (53%), followed by piperacillin/tazobactam (16%); while in the ASP stage, although still the most used agent, the frequency of amoxicillin/clavulanic reduced to 34%, while piperacillin/tazobactam increased to 26%  compared to the baseline stage (15.3%). The request of superficial swabs for culture in the vascular ward reduced from 22.7% in the baseline stage to 11.2% in the ASP stage.The intravenous route of administration was the most utilised route in both stages, where 89% and 84% of all drugs were administered intravenously in the baseline stage and the ASP stage, respectively. There was a higher number of culture targeted therapies prescribed in both wards in the ASP stage compared to the baseline stage see . MacroliIn the baseline stage, 443 antibiotic prescriptions were ordered for therapeutic purposes, of which 35% were inappropriate based on the algorithm used, whilst in the ASP stage, 442 antibiotic prescriptions were ordered of which 26% were inappropriate. In both stages, the main reasons for inappropriate prescriptions were the use of more broad-spectrum (Gyssens’ category IVd) and more expensive agents (Gyssens’ category IVc), where narrow spectrum and less expensive agents were available. Overall, 64% and 59% of the antibiotic use for prophylactic indications in the baseline and ASP stages, respectively, was inappropriate . AmoxiciPseudomonas aeruginosa compared to the baseline stage (A reduction (24%) in the total volume of antibiotic consumption was observed after implementation of the antibiotic stewardship round by 174.37 DDD/1000 patient days. The trend of the total monthly antibiotic consumption in the two stages is shown in ne stage . Consump11 Inappropriate use of antibiotics includes use of antibiotics at suboptimal doses, incorrect route of administration or poor adherence to prescribed drugs.26 It also involves the use of antibiotics without a defined bacterial/fungal infection or an indication for prophylaxis,26 and the use of last resort agents, while there are effective first and second line antibiotics.27This ASP intervention study was conducted in a surgery setting of a South African academic hospital with an antibiotic stewardship team led by an infectious diseases specialist. Over-consumption and inappropriate use of antibiotics are major drivers of ABR with consequent additional hospital costs.A baseline stage was used to describe the current standard of antibiotic usage in each of the wards. Both the baseline and ASP ward round targeted all patients on antibiotics. A wide range of surgical cases were admitted in the general ward. The cases included obstructed hernias, intestinal obstruction and cutaneous abscesses, perforated peptic ulcer diseases, and oesophageal carcinomas. Others are: lower gastrointestinal bleeding, rectal carcinomas, acute cholangitis, cholecystitis, pyogenic liver abscesses, primary liver cell carcinomas, peri-pancreatic sepsis, appendicitis, and overwhelming post-splenectomy sepsis. In the vascular ward, the cases included acute and chronic vascular ischemic diseases, diabetic foot diseases, stab injuries, and many other vascular conditions.29 The patients in the ASP stage had a higher mean age compared to those in the baseline stage which may have clinical implications in that older patients may have a higher risk of having other comorbidities, complications or severity of disease. Previous studies in surgical settings conducted in Malaysia and Jordan reported average ages of between 43 and 51 years,30 respectively, which is similar to those reported in this study. Although many ASPs have reported a reduction in LOS during interventions,31 in contrast, this study showed an increase in LOS. The average LOS of patients in the baseline and ASP stages were 8.33 ± 7.58 and 13.44 ± 11.83 days, respectively. This may be because of the fact that this study was conducted in a surgical setting and older patients were admitted during the ASP stage compared to baseline stage. Another reason for an increased LOS in the ASP stage was an increase in the prevalence of Pseudomonas aeruginosa in the ASP stage, which was statistically significant (p = 0.01) compared to the baseline stage. Despite an increase in LOS in this study, there was a reduction in antibiotic consumption and duration of antibiotic therapy (DoT) in the ASP stage. During ASP rounds, it was found that many patients  stayed longer on admission waiting for surgical procedures. As most of them did not have infections, it was unnecessary for them to be on antibiotics so these were stopped during ward rounds. The number of laboratory tests per patient may be driven by an increased length of stay where more tests are ordered with a longer LOS.The demographic characteristics of the patients show that more male patients were admitted to the surgical wards in both stages of the study, which is mirrored in other studies conducted in other countries.32 and the WHO has recommended the use of DDDs,18 defined as ‘the average maintenance dose of the drug when used for its primary indication in adults’.33 Expressing antibiotic consumption by DDDs/1000 patient days enables comparison between hospitals33 and clinical settings, as was implemented in this study. A key finding in this study was lower antibiotic consumption in the ASP stage. The ASP programmes in South African public and private hospitals have also reported reductions in antibiotic consumption,21 as well as in developed countries.35Globally there is no standard metric for quantifying antibiotic consumption across all clinical settings,36 This is higher than what is observed in the current study (26% – 35%), possibly because those studies were conducted in the ICU setting where higher antibiotic consumption is more likely. Studies in other developing countries such as India and Malaysia have also shown a high percentage (39% – 42%) of inappropriate antibiotic usage.29 However, this is not limited to developing countries, a Swiss study using Gyssens’ algorithm found a total of 32% of all prescriptions to be inappropriate which was high (37%) in patients who received antibiotics as treatment compared to those who received it for prophylaxis (17%).37 In the Netherlands, 16% – 29% of all antibiotic prescriptions were judged inappropriate using Gyssens’ algorithm, and this was mostly because of unjustified prescriptions.39The use of antibiotics when there is no indication for their use, such as to treat clean wounds and using it for prolonged duration or failure to de-escalate to narrow spectrum when the results of culture are available, are considered inappropriate. To encourage appropriate antibiotic use it was emphasised during rounds that antibiotics should only be used empirically when there is clear indication, and effort should be made to collect appropriate specimens for culture before starting empiric treatment and should be reviewed when the culture results are available. There were discussions during the rounds on what is considered appropriate such as prescribing antibiotics at the right dose via the right route of delivery. It was previously reported that both public and private Intensive Care Units (ICUs) across South Africa had a high percentage of inappropriate use of antibiotics of 44% and 61% in public and private ICUs, respectively.25 Augmentin and cefazolin are prescribed prophylactically in theatre at doses of 1.2 g bd and 1 g tds, respectively, but are then often continued unnecessarily for days on the wards.Surgical prophylaxis is an area of concern with respect to appropriate antibiotic usage. A high proportion of inappropriate antibiotic utilisation was seen in prophylactic usage in the baseline (65%) and ASP (62%) stages of this study, based on the wrong choice of agents, while 7.3% and 6.6% were inappropriate based on a duration of more than the recommended 24 h, respectively. Of the antibiotics prescribed, amoxicillin/clavulanic acid was the most frequently used prophylactic agent in both stages. The use of amoxicillin/clavulanic acid is not recommended for surgical prophylaxis by the SAASP and Standard Treatment Guidelines and Essential Medicines Lists for South Africa for most of the procedures conducted on patients at the time of this study.7 A study in a Jordanian cardiac surgery centre, found that up to 98% of surgical prophylaxis was inappropriate based on wrong antibiotic choice, while 59% was inappropriate with a duration of more than 48 hr as recommended by the guideline.30 A study in a private surgical setting in India found that 32% of surgical prophylaxis was inappropriate because of choice of agents, while 37% was inappropriate on account of prolonged duration of prophylaxis.40 Appropriate surgical prophylaxis reduces the risk of potential contamination during surgery, thus lowering the chance of SSIs.41 On the other hand, inappropriate surgical prophylaxis is associated with drug-related adverse events and Clostridioides difficile infections at the individual level, and increases the risk of developing resistant pathogens and healthcare costs at the community level.42Inappropriate use of prophylaxis has been found to be even higher in surgical settings of other developing countries; a Malaysian study found 66% of prophylaxis to be inappropriate, with 35% because of inappropriate duration and 16% as a result of wrong choice.43 A short DoT reduces the risk of developing resistance, adverse events and cost, and is recommended in all patients except in situations where there is difficulty in achieving source control, sepsis, and in immunocompromised individuals.A lower mean DoT for therapeutic purposes was found in the ASP stage of 3.96 ± 2.04 days compared to 4.74 ± 4.58 days in the baseline stage. A short DoT with an antibiotic is recommended by the World Society of Emergency Surgery in the management of intra-abdominal infections.45 The compliance rate may have been better if surgical consultants participated more actively in the rounds. In this study, it was found that Gyssens’ algorithm is a useful and reliable tool in determining appropriateness of antibiotic prescriptions and can be recommended to be used in future studies. In the authors’ opinion, the incorporation of antibiotic stewardship rotations and inclusion of short courses on appropriate antibiotic use in the management of surgical infections in the curriculum of South African surgery-related residency programmes will go a long way in ensuring optimal rational antibiotic usage and reducing the burden of SSIs. These results have clinical implications in that the level of inappropriate antibiotic usage for surgical prophylaxis in baseline and ASP is high, mostly because of incorrect agents being prescribed and for a prolonged duration of prophylaxis. This may increase rates of resistance, chances of acquiring SSIs and additional costs to the patients. The high rate of inappropriate surgical prophylaxis in the ASP stage was most likely on account of the majority of antibiotics being started in the operating theatre, whereas this intervention was conducted in the wards. Possible measures to improve appropriate antibiotic use for surgical prophylaxis could include adherence to national guidelines and educational programmes targeting theatre staff and surgeons on rational antibiotic usage.The programme was well accepted in the wards with no resistance from the surgeons or ward staff. During the programme, a 71% compliance rate to the recommendations was recorded and although this is a favourable outcome considering the short duration of the study, it is lower than that reported in other studies.21 Although the ASP ward round in this study showed a lower volume of antibiotic consumption and inappropriate antibiotic use compared to the baseline stage, which are important drivers of resistance, it was not possible to say this would lead to a reduction in ABR, because the study was conducted over a short period of time. Data collection was challenging because of lack of electronic patient records as well as monitoring the implementation of recommendations made during the antibiotic stewardship rounds.A limitation of this study is that it was conducted at two different time points and therefore it was not possible to determine if there was a significant impact of the ASP ward rounds on inappropriate antibiotic usage. Another limitation is that it was conducted in only two surgical wards of an academic hospital and this makes it difficult to generalise the findings. It may be problematic to replicate this study in many non-teaching hospitals in South Africa and across the African continent, because of the shortage of ASP experts outside of the academic setting. The Netcare model in which non-specialist pharmacists successfully drove the ASP in a South African group of private hospitals is an alternative option.Introduction of a weekly ASP round in two surgical wards of a tertiary South African hospital showed a lower level of antibiotic consumption, improvement in the appropriate use of antibiotics and a reduction in the duration of antibiotic therapy. Hospitals in developing countries are encouraged to optimise the use of antibiotics by implementing ASP programmes.