The limited availability of microbiology services in sub-Saharan Africa impedes accurate diagnosis of bacterial pathogens and understanding of trends in prevalence and antibiotic sensitivities. We aimed to characterize bacteremia among hospitalized children in The Gambia and to identify factors associated with bacteremia and mortality.We prospectively studied children presenting with suspected severe infection to 2 urban hospitals in The Gambia, between January 2013 and September 2015. Demographic and anthropometric data, clinical features, management, and blood culture results were documented. Urine screens for antibiotic activity were performed in a subset of participants.Staphylococcus aureus predominated. Gram-positive organisms were more commonly identified than Gram-negative (P < .01). Antibiotic resistance against first-line antimicrobials (ampicillin and gentamicin) was common among Gram-negative bacteria . Factors significantly associated with bacteremia included the following: gender, hydration status, musculoskeletal examination findings, admission to the Medical Research Council The Gambia at London School of Hygiene & Tropical Medicine hospital, and meeting sepsis criteria. Those associated with increased mortality were presence of a comorbidity, clinical pallor, tachypnea, and altered consciousness. Tachycardia was associated with reduced mortality.Of 411 children enrolled , 79.5% (325 of 409) reported prehospital antibiotic use. Antimicrobial activity by urinary screen for antibiotic activity was detected in 70.8% (n = 80 of 113). Sixty-six bacterial pathogens were identified in 65 (15.8%) participants and The bacteremia rate in children with suspected childhood life-threatening infectious diseases in The Gambia is high. The pattern of pathogen prevalence and antimicrobial resistance has changed over time compared with previous studies illustrating the importance of robust bacterial surveillance programs in resource-limited settings. Child mortality in sub-Saharan Africa (SSA) is high, and the majority of these deaths can be attributed to bacterial infections . PassiveStreptococcus pneumoniae and Haemophilus influenzae were the most common pathogens in the pediatric population. Although predictors of bacteremia have been widely studied in high-income countries ) for non-parametric variables. Cohen’s kappa coefficient was used to measure agreement between reported antibiotic use and urine antimicrobial activity. Fisher’s exact tests and χ Approval for the EUCLIDS study was obtained from the Joint MRCG at LSHTM-Gambia Government Ethics Committee (SCC 1287). A parent/guardian provided written (signed or thumb-printed) informed consent for their child to take part in the study. For parents not literate in English, an impartial witness was present throughout the informed consent discussion, undertaken in one of the local languages, and the impartial witness signed to attest to the completeness of the information given.A total of 411 study participants were recruited, 57.6% (n = 237 of 411) at the EFSTH. Overall, 60.1% (n = 247 of 411) were male with a median age of 29 months . A total of 74.9% (n = 308 of 411) reported up-to-date immunizations. Forty-two (13.3%) had a history of consanguinity, and 37 (9.0%) had a history of a comorbidity including sickle cell disease, cerebral palsy, asthma, congenital hydrocephalus, insulin dependent diabetes mellitus, epilepsy, and congenital and acquired heart diseases. A total of 12.2% (n = 50 of 411) had cigarette smoke exposure at home. A total of 3.4% (n = 14 of 411) had confirmed malaria infection. A total of 15.5% (n = 54 of 349) had severe wasting. A total of 30.2% (n = 124 of 411) were admitted at another healthcare facility before being seen at the study sites. The median duration of symptoms before presentation was 3.9 days , and the median duration of stay at the study sites on admission was 6.5 days .Escherichia coli and S pneumoniae). Gram-positive organisms were more commonly identified than Gram-negative organisms . The most common isolated pathogen was S aureus , which was predominantly responsible for soft tissue and/or bone infections with or without sepsis. Sixty-six bacterial pathogens were identified by blood culture from 65 of 411 (15.8%) study subjects, including 1 polymicrobial blood culture (P = .32). A positive blood culture was found in 16 of 113 (14.2%) participants in whom the screen was performed. There was a trend towards increased bacteremia in patients with a positive urine antibiotic screen (OR = 2.9), but this was nonsignificant .Overall, 79.5% (n = 325 of 409) reported use of antibiotics in the 7 days before recruitment. Urine screens for antibiotic activity were completed on a subset of 113 recruits, 73 (64.6%) of whom reported prehospital antibiotic use in preceding 3 days; 80 (70.8%) had a positive screen for antibiotic activity . There wStaphylococcus and 1 case of S pneumoniae showed resistance to first-line antimicrobials. All Gram-positive organisms were sensitive to ceftriaxone. All  S aureus isolates were methicillin-sensitive.Antibiotic resistance was uncommon among the Gram-positive pathogens for commonly used first-line  and second-line  antimicrobials. Two cases of However, antibiotic resistance was common in Gram-negative pathogens for standard first-line  and second-line  antimicrobials. There was widespread resistance to trimethoprim/sulfamethoxazole in both Gram-positive  and Gram-negative  pathogens see .P < .05) variables, those with highest odds for bacteremia were meeting criteria for sepsis  and bone infection . The significant variables with highest odds for mortality were previous hospitalization , altered consciousness , and need for oxygen therapy .A univariable analysis of clinical findings associated with bacteremia and mortality  and 10.2% had sequelae at time of discharge (n = 42 of 411). The median age (IQR) of study participants who died or had sequelae at time of discharge was 16.3  and 56.0  months, respectively. Factors associated with mortality as analyzed in the multivariable model were a positive history of a comorbidity, clinical pallor, presence of tachypnoea, and altered consciousness. Tachycardia was protective against mortality in the multivariable logistic regression analysis .In this prospective, multicenter study of bacteremia amongst study subjects aged 1 month to 18 years presenting with sepsis or SFI to 2 hospitals in urban Gambia, we found a high prevalence of bacteremia. A total of 15.8% of all participants had an identifiable pathogen on blood culture, higher than that reported in similar studies in SSA , 21–23. We observed patterns of pathogen prevalence that were substantially different from previously published reports, highlighting the need for reassessing contemporary bacterial epidemiology to guide current and future practice. Combined mortality and severe morbidity associated with infection were substantial, affecting 23% of patients.S aureus was the predominant pathogen across all age groups [S pneumoniae predominated. This contrasts with (1) a recent publication from Ghana in which nontyphoidal salmonella accounted for more than half of all invasive bacterial infections in children under 5 years of age [S pneumoniae was the most common pathogen among all age groups [Multivariate analysis identified requirement for antimicrobial therapy on admission and requirement for immediate, aggressive management to prevent mortality as clinical features that predicted presence of bacteremia. Consistent with other recently published studies from SSA, e groups , 31–34, s of age  and (2) e groups .H influenzae type B (Hib) vaccine in The Gambia in 2007, rates of Hib disease have decreased, although there has been some recrudescence in Eastern Gambia [H influenzae sepsis identified in this study, none were serotype B.One major factor that is likely to have contributed to this change in pathogen prevalence is the introduction of the pneumococcal conjugate vaccine (PCV) to the Gambian Expanded Program on Immunisation (EPI), with the 7-valent vaccine (PCV7) being introduced in 2009 followed by PCV13 in 2011. Recent surveillance studies, completed postintroduction of the Gambian PCV program, have shown a substantial reduction in invasive pneumococcal disease of approximately 55% among children aged 2 to 59 months . Althougn Gambia . Of the S aureus disease in SSA, and our findings that 73% of isolates were penicillin resistant, and 2 of 9 were gentamicin resistant, empiric regimens should treat bacteremia caused by S aureus  effectively, for instance, using co-amoxiclav, because early adequate treatment of sepsis is key for improved survival. Although it was reassuring to see that all S aureus isolates were methicillin susceptible, close surveillance for emerging resistance remains crucial.Antibiotic resistance was found predominantly in Gram-negative organisms—a recognized and global concern. These pThe management of severe sepsis should be guided by blood culture and antibiotic sensitivity testing, and this may lead to therapeutic options that include broader spectrum antibiotics such as piperacillin tazobactam. Maintaining informed choices for first- and second-line antibiotic prescribing will require ongoing microbiological surveillance and the development of antimicrobial stewardship strategies.Pneumocystis jirovecii pneumonia.Trimethoprim/sulfamethoxazole is commonly used in The Gambia because of its broad-spectrum antimicrobial efficacy, low cost, and easy availability. However, we found that both Gram-negative and -positive bacteria were highly resistant to this antibiotic on laboratory testing, suggesting that trimethoprim/sulfamethoxazole in The Gambia, and probably elsewhere in SSA , should S aureus, indicating that all such cases need to be treated with antistaphylococcal antibiotics.Bacteremia was significantly more common in dehydrated children. This finding stresses the importance of assessment of hydration status and appropriate fluid resuscitation in suspected sepsis. Soft tissue, joint, and bone infections were associated with The risk of mortality was highest in those with comorbidities, including sickle cell disease or other congenital conditions, and in those with clinical features of pallor, tachypnoea, or altered consciousness. Therefore, the presence of these symptoms should be considered a “red flag”. They are recognizable by nursing and medical staff, and their importance is emphasized in the WHO Emergency Triage Assessment and Treatment (ETAT) guidelines . Sickle S pneumoniae—and the likelihood of contaminants [This study had strengths and limitations. We found high rates of reported prehospital antibiotic usage, confirmed by urinary screen for antibiotic activity in a subset of participants, which has implications for management of patients. This could have significantly affected the yield of positive isolates. Bacterial culture positivity rates may have been affected by storage of inoculated blood culture bottles at EFSTH before processing and the use of suboptimal blood volumes. Children up to age 15 years had blood collected in aerobic pediatric blood culture bottles, which are optimized for lower blood volumes. The storage and volume of blood are factors known to affect both culture yield—particularly for detection of rapidly growing bacteria including aminants . Nonetheaminants , and it In conclusion, the bacteremia rate in Gambian pediatric patients with severe sepsis and SFI was high, despite high rates of prehospital antibiotic use. We observed a changing pattern of pathogen prevalence and antimicrobial resistance from previously published data, as well as subregional differences in prevalent pathogens. Our study highlights the need for structured bacterial surveillance programs in resource-limited settings, however scarce the resources may be.Open Forum Infectious Diseases online. Consisting of data provided by the authors to benefit the reader, the posted materials are not copyedited and are the sole responsibility of the authors, so questions or comments should be addressed to the corresponding author.Supplementary materials are available at ofz332_suppl_supplementary_materialClick here for additional data file.


Furthermore, identification of different mix ratios of concrete were successfully demonstrated in this paper. In conclusion, the EM sensor is capable of detecting moisture content non-destructively and could be a potential technique for maintenance and quality control of the building performance.Concrete failure will lead to serious safety concerns in the performance of a building structure. It is one of the biggest challenges for engineers to inspect and maintain the quality of concrete throughout the service years in order to prevent structural deterioration. To date, a lot of research is ongoing to develop different instruments to inspect concrete quality. Detection of moisture ingress is important in the structural monitoring of concrete. This paper presents a novel sensing technique using a smart antenna for the non-destructive evaluation of moisture content and deterioration inspection in concrete blocks. Two different standard concrete samples  were investigated in this research. An electromagnetic (EM) sensor was designed and embedded inside the concrete to detect the moisture content within the structure. In addition, CST microwave studio was used to validate the theoretical model of the EM sensor against the test data. The results demonstrated that the EM sensor at 2.45 GHz is capable of detecting the moisture content in the concrete with linear regression of R Concrete structures play an important role in structural health of buildings, bridges, and so forth. . It is nExtensive research studies have reported that moisture content within the concrete structures is a key point for structural health monitoring ,8. The mIn recent years, numerous studies specialized in the structural health monitoring (SHM) investigating new smart material-based methods to replace the conventional techniques . These sHence, this research paper aims to develop a smart sensing technology by using electromagnetic wave techniques for the determination of moisture content and therefore deterioration in concrete structures. A microstrip patch antenna developed to generate EM signals and continuous data monitoring was performed by transmitting information to the data acquisition system. The smart sensor is embedded inside the concrete structure for real-time monitoring. A model for determination of moisture content and deterioration of concrete is successfully developed and implemented. Furthermore, theoretical model of signal transmitting of electromagnetic wave was validated by using CST microwave simulation software. This smart sensor can be easily applied to determine moisture content of concrete in real time and user-friendly approach.11) and transmission coefficient (S21) [Dielectric constant (ε′) is defined as a quantity measuring the ability of a material to store electrical energy in an electric field. The changing moisture content of concrete will vary the dielectric constant due to the polarization of water inside the concrete sample.Dielectric loss (ε″) is defined as loss of electromagnetic energy propagating inside the concrete structure due to the rotation and oscillation between the water molecules thus resulting in friction.Moisture content inside concrete structures can be studied from the data of their interactions with microwaves. This interaction can be revealed in the form of a unique signal spectrum called as reflection coefficient (Snt (S21) . Permittnt (S21) . DielectChanges of moisture content inside the concrete structure will alter its permittivity and yielding a unique spectrum when it comes in contact with microwave . Hence, CST Microwave Studio was used to design a patch type sensor that resonates at 2.45 GHz frequency for this investigation. The designed sensor was proposed under consideration of the desired resonant frequency, dielectric medium of the patch antenna and size consideration for overall rectangular patch antenna. The width (W) of the patch is calculated by Equation (1):The length (L) of the patch is calculated by Equation (2):A small square size of 60 mm × 60 mm ground was incorporated in the patch antenna. The substrate size has the similar size to the ground. Up to date research, there are different methods of feeding to the microstrip patch antenna such as inset feed method, fed with a quarter-wavelength transmission line, coaxial cable, coupled feeds and aperture feeds. In this research, we aim to produce a remarkable small size, simple fabrication and easy integration antenna. With the benefits of minimal dependence on substrate thickness and unipolar configuration, quarter-wavelength transmission feed line was selected for the patch antenna.Once the sensor is designed and a desired performance is obtained, the next step was to fabricate it. EAGLE  was used prior to moving to the actual fabrication of the antenna. EAGLE is a PCB (Printed Circuit Board) design software, which is developed by CadSoft . A preliminary cubes structure for testing was made from two different standards . The size of the block is 150 × 300 × 300 mm there were no reinforcement bars. The composition of the concrete structures is provided in An electronic weight balance was placed under the concrete block throughout the experiments. The weight before and after the test are recorded to measure the weight of moisture content in the concrete block. Equation (3) was used to evaluate the water content measurement throughout the experiments.A printed circuit board (smart sensor) transmitted signal of 2.45 GHz was designed at Liverpool John Moores University and fabricated at Sensor City Liverpool Limited. The smart sensor is embedded within the concrete structure as shown in 11) were detected from the patch antenna connected to the VNA. All the results were recorded throughout the experiments to quantify the moisture content lost.The experimental setup for this investigation is shown in A continuous monitoring was implemented using VNA for attenuation of the electromagnetic wave propagation in the concrete and weight of water content by electronic weight balance. All the experimental results are recorded by using designed LabVIEW Program in the interval of 5 min for 48 h. Three repeatability test for each of the samples were performed. Root means square (RMS) error was calculated and was found to be >95% for the repetition.Numerical simulation was conducted by using CST simulation package in order to stimulate the resonant frequency for the microstrip patch antenna. The simulation results were set at range of 1.8 GHz–3.0 GHz and were validated against the experimental results.Signal spectrum generated from the smart sensor inside the MS 26-1-8:2010 concrete is illustrated in 2 = 0.7286. The results show a fair correlation in the region of 2.43 GHz. Further investigation was carried on for the area of interest around 4.16 GHz, which is the second harmonic wave of the designed 2.45 GHz antenna sensor as show in 2 = 0.9587 can be observed compare to 2.43 GHz. Hence, it is concluded that the designed microstrip patch antenna can accurately monitor the moisture content of the concrete and hence deterioration monitoring of concrete structures.(1)Designed of 2.45 GHz patch antenna is well validated between experiment and simulation.(2)Self-printed 2.45 GHz patch antenna successfully detected moisture content in two concrete blocks that were made based on two different standards .(3)Detection of moisture content in Malaysia MS 26-1-8:2010 and Europe EN 206-1-2013 concrete blocks is well correlated at linear regression of 0.9228 and 0.9587 respectively.The EM sensor showed high potential to be used for moisture loss evaluation in concrete structures. The following conclusions can be drawn:The future investigation is to implement the full sensing system, namely circuitries of RF signal generator inside the concrete by self-generated energy for data transmission for moisture detection.


Bacteria-based self-healing concrete is a construction material used to repair cracks in concrete, in which the bacterial spores are immobilized by bacteria carriers. However, the currently available bacteria carriers are not always suitable due to a complicated procedure or high cost. To develop a more suitable bacteria carrier as well as improve the anti-crack capability of self-healing concrete, in this study we evaluate the feasibility of using rubber particles as a novel bacteria carrier in self-healing concrete. Two types of self-healing concrete are prepared with rubber particles of different sizes to quantify the crack-healing effect. In addition, the fluidity and mechanical properties of the self-healing rubber concrete are compared with those of plain concrete and normal rubber concrete. The experimental results show that the self-healing rubber concrete with a particle size of 1~3 mm has a better healing capacity than the self-healing rubber concrete with a particle size of 0.2~0.4 mm, and the width value of the completely healed crack is 0.86 mm. The self-healing rubber concrete has a higher slump than the plain concrete and normal rubber concrete. According to the strength tests, the compressive strengths of the self-healing rubber concrete are low early on but they exceed those of the corresponding normal rubber concrete at 28 days. Moreover, the self-healing rubber concrete has higher splitting tensile strengths than the plain concrete and a better anti-crack capability. The results of a comparison to the other two representative bacterial carriers indicate that rubber particles have potential to be a widely used bacteria carrier for practical engineering applications in self-healing concrete. Concrete is a widely used construction material as it has a high compressive strength and good durability. However, a major concern with concrete is that it is vulnerable to cracking under the influence of temperature fluctuations and external load due to its low tensile strength and poor deformation ability ,2. The cThe bacteria-based self-healing of concrete cracks is based on Microbial Induced Calcite Precipitate (MICP), which involves the application of mineral-producing bacteria to precipitate calcium carbonate onto the crack face in the concrete ,13. The Due to the harsh environment inside the concrete, the bacterial spores must be protected from squeezing and high alkalinity by a bacteria carrier to ensure that the bacteria have space to grow and a mineralized environment . A rangeScrap rubber tires are a major form of environmental solid waste that are dangerous not only due to being a potential environmental threat, but also because they constitute a fire hazard and provide a breeding ground for rats, mice, and mosquitoes ,22. One A ureolytic-type bacterium, Sporosarcina pasteurii ATCC11859, was used in this study. It was cultured in a sterilized liquid medium containing 20 g/L of yeast extract, 10 g/L of ammonium sulfate, and 17.5 g/L of Tris regent. After cultivation in a shaker for 24 h at a temperature of 30 °C and a rotational speed of 220 rpm, the bacteria reached a stable growth period. Then, the bacterial suspension was centrifuged at 4000 rpm for 30 min to separate the bacterial cells from the cultivation solution. The supernatant was dispensed with and the remaining bacterial cells were re-suspended in 9 g/L of NaCl solution. The re-suspended bacterial solution was placed in an oven at 30 °C for 14 days, during which time the bacteria remained in starvation. After that, almost all bacterial cells turned into bacterial spores. This was confirmed by microscopic observation of the re-suspension solution as shown in Concrete specimens were prepared with ordinary Portland cement , tap water, local natural sand (distributed within 0~5 mm), and coarse aggregate . We adopted two rubber particle sizes (1~3 mm and 0.2~0.4 mm) in this study, whose particles size distributions were displayed in 3 of concrete and that there was sufficient SA solution to disperse the spores under the premise that the amount of rubber particles could be determined.The bacterial spore suspension was prepared according to the method described in The mixture of the three substances was stirred and then dried in a cool and ventilated place until the SA had completely solidified.Before preparing the self-healing concrete, the spore-containing rubber particles were coated with cement  by a stirring method. Thus, the cement can protect SA from directly contacting with free water and slow down the dissolution of SA in the fresh concrete.When manufacturing the self-healing concrete specimens, the nutrients for bacterial growth (yeast extract and ammonium sulfate) and the necessities for bacterial mineralization  were mixed into the tap water, which was added to the concrete mixture following the coarse aggregate, cement, rubber particles and sand.Five types of concrete were prepared in this study: two types of self-healing rubber concrete, each with a different rubber particle size (1~3 mm (SRC-L) and 0.2~0.4 mm (SRC-S)), plain concrete (C), and two types of normal rubber concrete (RC-L and RC-S). The latter three types of concrete were used as contrasts of the self-healing concretes’ properties. The water-to-cement ratio of these mixtures was 0.54. Note that the rubber particles replaced 10% of the volume of the sand in the normal rubber concretes and the self-healing rubber concretes to effectively decrease the brittleness of the concrete and not reduce the strength of the concrete too much at the same time . The mixTo determine the effects of rubber particles and SA on bacterial spore growth, six bottles of 100 mL of fresh liquid medium were prepared then separately inoculated with: 1 mL of bacterial spore suspension (I); 1 mL of bacterial spore suspension and 1 mL of SA solution (II); 1 mL of bacterial spore suspension and 2.2 g of sterilized rubber particles (III); 1 mL of bacterial spore suspension and 2.2 g of unsterilized rubber particles (IV); 2.2 g of sterilized spore-containing rubber particles (V); and 2.2 g of unsterilized spore-containing rubber particles (VI). All media were cultured in a shaker at a temperature of 30 °C and a rotational speed of 220 rpm for four days. The urease activities in the media were detected using a conductivity method  to estimThree prismatic specimens (100 mm × 100 mm × 300 mm) were prepared to observe the capacity of each type of concrete to self-heal cracks. The cracks were created at the concrete age of 7 days using a three-point bending method see a. The spAfter the cracks were created, the concrete specimens were placed in a water box for crack healing at a temperature of 20 °C, as shown in The slump of fresh concrete, the compressive strength of concrete, and the splitting tensile strength of concrete were investigated according to the Code for Hydraulic Concrete in China (SL 352-2006).F and F0 are the compressive strength at the age of 28 days of the specimens with and without precompression, respectively, in MPa.Three cubic specimens (150 mm × 150 mm × 150 mm) of each type of concrete were pre-compressed to their maximum strengths at the age of 7 days. These specimens with many cracks were placed under the self-healing incubation conditions for 21 days. Afterward, their compressive strengths were determined again. The strength regain of each type of concrete is expressed as the average of three specimens, which was calculated by Equation (1).d0 is the average initial crack width and dt is the average width measured at the healing time of all 10 measurement points.To quantify the crack-healing capacity, 10 measurement points were selected and averaged along with the length of each crack in the microscopic image. The crack widths at the measurement points were measured. The crack healing percentage was determined as follows:The slumps of the five types of concrete are shown in The compressive strengths of the five types of concrete at different ages are plotted in The splitting tensile strengths of the five types of concrete at different ages are plotted in The test results have proved that the self-healing concrete using rubber particles to immobilize bacterial spores can produce precipitations in the cracks to repair them. The working mechanism of the self-healing rubber concrete is displayed in protect the bacterial spores from squeezing and high alkalinity in the concrete;provide spaces for bacterial growth and mineralization; andreduce the brittleness of the concrete and improving the anti-crack capability of the concrete.In the self-healing concrete, the role of the rubber particles is to:wrap the bacterial spores in the pores of the rubber particles;slowly dissolve and release the bacterial spores when cracks appear; andimprove the bonding of rubber particles and cement.The role of the SA is to:3 concrete is only 8.26 US$ , which is lower than the price of the other two bacterial carriers. Moreover, the anti-crack capability of the concrete can be improved by the rubber particle method, as shown in A comparison between rubber particles and two other representative bacterial carriers is exhibited in The method for immobilizing bacterial spores with rubber particles was feasible and the maximum values of the widths of completely healed cracks after 28 days of healing were 0.86 mm in the SRC-L concrete and 0.52 mm in the SRC-S concrete.The healing capacity of the SRC-L concrete was better than that of the SRC-S concrete because larger rubber particles can provide larger spaces for bacteria to grow and mineralize, avoiding bacteria death due to squeezing in the concrete.The compressive strength of the self-healing concrete was low at early ages due to the negative effect of the nutrients in the concrete on cement hydration, but exceeded the compressive strength of the corresponding normal rubber concrete at 28 days because calcites were produced within the pores of the concrete matrix.The splitting tensile strength of the self-healing concrete was higher than that of the plain concrete, resulting from SA improving the bonding between rubber particles and cement. In addition, the rubber particles can enhance the anti-crack capability of the concrete.The immobilization of bacterial spores using rubber particles has the advantages of a simple procedure, materials savings, and low cost, and provides a more suitable method for engineering applications of self-healing concrete.This paper investigated the feasibility of using rubber particles as a novel bacterial carrier in self-healing concrete. Two types of self-healing concrete were prepared with different rubber particle sizes, whose healing capacities were evaluated. The properties of the self-healing rubber concrete, including the slump, the compressive strength, and the splitting tensile strength, were compared with those of plain concrete and normal rubber concrete. The following conclusions can be drawn:Even through there are some problems with self-healing rubber concrete that need to be solved, such as the distribution of bacterial carriers in the concrete, the most suitable rubber particle size, and the protective effect of rubber particles on bacterial spores in the long term, the use of rubber particles remains an innovative and promising method for the immobilization of bacterial spores in self-healing concrete.


P = .033) and respiratory rates  decreased, but blood pressure  and vasogenic medications did not change after ketamine infusion. Continuous ketamine was not a significant risk factor for mortality . Continous ketamine could be used in PICU without hemodynamic instability. Further studies in randomized controlled design about the effects of continuous ketamine infusion on hemodynamic changes, sedation, and mortality are required.We investigated the hemodynamic and mortality effects of continuous ketamine infusion in critically ill pediatric patients. We conducted a retrospective cohort study in a tertiary pediatric intensive care unit (PICU). Patients who used continuous sedative from 2015 to 2017 for 24 hours or more were included. We compared blood pressure, heart and respiratory rates, vasogenic medications, and sedation and pain scores for 12 hours before and after initiation of continuous ketamine. The mortality rates for continuous ketamine and Non-ketamine groups were compared by multivariate logistic regression. A total of 240 patients used continuous sedation, and 82 used continuous ketamine. The median infusion rate of ketamine was 8.1 mcg/kg/min, and the median duration was 6 days. Heart rates (138 vs. 135 beat/minute,  Pediatric patients in intensive care units (ICUs) are frequently treated with sedatives and analgesics because critical care is a stressful, painful experience . One stuKetamine is a noncompetitive antagonist of N-methyl-D-aspartate (NMDA) receptor that has analgesic and antihyperalgesic properties. It is an ideal anesthetic because it dose-dependently produces analgesia, amnesia, unconsciousness, and akinesia . CriticaIn this retrospective cohort study, we screened and reviewed all consecutive admissions from January 2015 to December 2017 to a pediatric intensive care unit (PICU) of a tertiary hospital. The PICU was a 15-bed, combined medical-surgical unit. Patients with congenital heart disease or organ transplantation were admitted to other dedicated units immediately post operation. In the PICU under study, opioid-based analgosedatives were used as an initial sedative for most mechanically ventilated patients according to analgesia-first sedation suggested in the guideline for pain, agitation, and delirium management . ContinuData on eligible patients and the use of sedatives were supplied by a licensed medical records officer from the electronic medical record (EMR). Data on continuous medication which were recorded in EMR sheets included medication name, infusion rate and dose, start and finish times, change of dose, and time of change. Among the PICU-admission cohort, records for patients with a history of continuous medication or with sedative orders for more than 2 consecutive days were reviewed. Patients’ charts and prescriptions were reviewed by researchers who were pediatric intensive care physicians and pharmacists. Patients who had ketamine as a continuous sedative were put in a Ketamine group, and patients who had any sedative other than ketamine as a continuous sedative were put in a Non-ketamine group.Medication changes to control blood pressure were reviewed by ICU pharmacists for the periods 12 hours before and after the start of continuous ketamine medication. Data were collected on addition, deletion, or dose change in intravenous or oral antihypertensives or vasopressors  to evaluate hemodynamic changes which required treatment modification. Data on changes in sedative medications were collected 12 hours before and after the start of continuous ketamine infusion. Vasoactive-inotropic score (VIS) was calculated to compare the dose of vasopressor , and antVital signs were recorded in EMRs hourly except in unstable and critical situations. We collected systolic, diastolic, and mean blood pressure values; heart rates; and respiratory rates 12 hours before and after the start of continuous ketamine infusion. For each, we used the mean value over 12 hours for comparisons. For sedation and pain evaluation, the Richmond Agitation-Sedation Scale (RASS) and Face Pain Scale (FPS) or Face-Leg-Activity-Cry-Consolability (FLACC) scores were measured at least every 8 hours and at other frequencies according to clinical changes. We collected the RASS and FPS or FLACC scores 12 hours before and after the start of continuous ketamine infusion and used the mean values over 12 hours for comparison.Descriptive statistics were used for age, sex, underlying disease, use of vasopressors or mechanical ventilation, duration of mechanical ventilation, pre-ICU hospital stay, ICU and hospital lengths of stay, predicted mortality, and actual mortality. Parameters were compared between the Ketamine and Non-ketamine groups by Mann-Whitney test. Paired tests were used to compare parameters between pre-ketamine infusion and post-ketamine infusion. We compared systolic, diastolic, and mean blood pressures; heart rates; and respiratory rates by paired t-test; and antihypertensive and vasopressor use by McNemer test. We compared RASS, pain-control scores, and the doses of other sedatives between pre and post ketamine infusion by Wilcoxon signed-rank test. To evaluate risk factors associated with mortality, we conducted multivariate linear regression tests using age; sex; use of mechanical ventilation or vasopressor; use of continuous ketamine, fentanyl, benzodiazepine, or dexmedetomidine; pre-ICU hospital days; predicted mortality at admission; and underlying oncologic or cardiac disease.The study protocol was reviewed and approved by the Institutional Review Board of Samsung Medical Center (IRB No. 2018-02-010). The Institutional Review Board waived the need for informed consent for this study.P = .008). Although underlying disease was not significantly different between groups, oncologic disease was more common in the Ketamine group (32.9% vs. 15.8%), and cardiac disease was more common in the Non-ketamine group (19.5% vs. 32.3%). Application of mechanical ventilation was similar between the Ketamine and Non-ketamine groups . Dexmedetomidine was more commonly used in the Ketamine group , and the number of sedatives used was higher in the Ketamine group . The Ketamine group, compared to the Non-ketamine group, had longer pre-ICU hospital stay , duration of mechanical ventilation , ICU length of stay , and hospital length of stay . The mean predicted mortality of total study population was 15.4%, and actual mortality was 18.7% 945/240). The standard mortality ratio was 1.21 . Median predicted mortality derived from severity score at admission was higher in the Ketamine group , as was crude mortality   . The staMedian ketamine infusion rate was 8.1 mcg/kg/min , and median duration of continuous infusion was 6 days  in Ketamine group. Among 82 patients of Ketamine group, ketamine was the first sedative drug for 24 (29.2%), the second for 27 (32.9%), the third for 29 (35.4%) and the fourth for 2 (2.4%). In the Ketamine group, 10 patients (12.2%) received only ketamine as a continuous sedative.P = .033) and respiratory rate  decreased after initiation of continuous ketamine infusion. Blood pressure (BP) did not change significantly, but VIS  slightly increased after continuous ketamine infusion (P = 0.06) and fentanyl dose increased  after continuous ketamine infusion  . Sex andMultivariate linear regression included parameters of age; sex; use of mechanical ventilation, vasopressor; continuous ketamine, fentanyl, benzodiazepine, or dexmedetomidine; pre-ICU hospital days; predicted mortality at admission; and underlying oncologic disease.In this study, we showed that continuous ketamine infusion with or without other sedatives did not change blood pressure significantly with an increase in median VIS 3.4. After starting continuous ketamine, patients were more sedated, although opioid administration also increased. We did not find that continuous ketamine infusion significantly affected mortality rate in the severity-adjusted analysis.Ketamine administration is reported to increase catecholamine concentration in serum and cerebrospinal fluid and to increase sympathetic activity and blood pressure –18. KetaP = .416), and opioid use decreased after ketamine (0.81 mg/kg/hr) initiation [P = .10) after continuous ketamine in our study since pain scores of the patients were already low before continuous ketamine.Our results showed a significant decrease in RASS score after ketamine infusion. This result might have been caused by an additional sedative effect of ketamine or by increased fentanyl dose. Ketamine was given to patients who required deeper sedation. Therefore, we hypothesize that an increase in mean fentanyl dose was not associated with ketamine infusion but with patient condition. In a previous study of 36 critically ill adult patients, the proportion of time that patients were at their goal RASS was not significantly different for 72 hours before or after ketamine initiation  than Non-ketamine group (0.80). Since the severity scoring reflects only the initial condition at admission, we adjusted more confounding factors, including the proportion of oncological disease numbers of sedatives used, and pre-ICU hospital days. In adjusted analyses, differences in mortality between the two groups were not statistically significant. In a meta-analysis, all-cause mortality with ketamine infusion in combination with midazolam was not different from the use of propofol, benzodiazepine, or alpha agonist . We did P value of 0.05 for mortality outcome. Second, there are many differences between the two groups. We could not adjust for all mortality risk factors in the Ketamine group due to the retrospective nature of the study. However, we think that the mortality risk for continuous ketamine infusion might decrease if we adjusted for more risk factors when we consider the high severity of the Ketamine group. Third, adverse drug reactions such as salivation or hallucination before and after continuous ketamine infusion were not evaluated due to unsatisfactory records. Forth, we could not evaluate the dose-response of ketamine on the clinical parameters and mortality.Our study has some limitations. First, this was a single-center study. We recruited as many feasible cases as possible, but we found that our study showed a 65% power with a two-sided Despite the limitations, our study had the largest number of patients who used continuous ketamine among reported studies. This was the first study to show changes in vital signs after initiation of continuous ketamine infusion and compare mortality with continuous ketamine sedation in PICU patients.Continuous ketamine infusion could be used without hemodynamic instability in PICU patients. Further studies in randomized controlled design about the effects of continuous ketamine infusion on hemodynamic changes, sedation, and mortality are required.S1 FigCC: correlation coefficient.(DOCX)Click here for additional data file.


Muscle energy techniques are applied to reduce pain and increase range of motion. These are applied to a variety of pathological conditions and on asymptomatic subjects. There is however limited knowledge on their effectiveness and which protocol may be the most beneficial.The aim of this review is to determine the efficacy of muscle energy techniques (MET) in symptomatic and asymptomatic subjects.Systematic Review.A literature search was performed using the following database: Cochrane Library, MEDLINE, NLM Pubmed and ScienceDirect. Studies regarding MET in asymptomatic and symptomatic patients were considered for investigation. The main outcomes took into account range of motion, chronic and acute pain and trigger points. Two trained investigators independently screened eligible studies according to the eligibility criteria, extracted data and assessed risk of bias. Randomized control trials (RCT’s) were analyzed for quality using the PEDro scale.A total of 26 studies were considered eligible and included in the quantitative synthesis: 14 regarding symptomatic patients and 12 regarding asymptomatic subjects. Quality assessment of the studies through the PEDro scale observed a “moderate to high” quality of the included records.MET are an effective treatment for reducing chronic and acute pain of the lower back. MET are also effective in treating chronic neck pain and chronic lateral epicondylitis. MET can be applied to increase range of motion of a joint when a functional limitation is present. Other techniques seem to be more appropriate compared to MET for trigger points. Muscle energy techniques (MET) were originally developed by two osteopathic physicians, Fred Mitchell, Sr. and Fred Mitchell, Jr., to treat soft tissue, mobilize joints, stretch tight muscles and fascia, reduce pain and to improve circulation and lymphatic drainage , 2. MET Many studies have applied MET in patients with acute and chronic low back pain (LBP) –10, lateMET protocols developed differ in paradigms, such as in the number of repetitions, strength of contraction, duration of stretch phase and duration of relaxation phase , 17, 19.This systematic review aims to determine if muscle energy technique may be effective on pain or may increase range of motion of a joint and if such techniques are applied using different protocols. The PRISMA  statement was adopted . StudiesStudies that met the following criteria were included or excluded in this systematic review.This review includes studies that have applied MET in both asymptomatic subjects and symptomatic patients. In particular, RCT’s analyzing patients who have been treated for their condition using MET and which include a control group, were selected for the symptomatic population. Studies that do not have a control group or a comparator were not considered for inclusion. RCT’s, pretest-posttest and quasi-experimental studies analyzing the effect of MET were also included for the asymptomatic subjects. Reviews, systematic reviews and meta-analysis were not considered.All the analyzed participants were adults to whom a MET had been applied. Children were not considered for analysis.The interventions that applied MET in both asymptomatic and symptomatic participants described in the eligible studies will be included in this review. For the asymptomatic participants the interventions aimed to increase range of motion and reduce tenderness when present. For symptomatic participants the interventions aimed to reduce either acute or chronic pain. According to the nature of the variables of each study, pain was measured through different means.Comparators were control groups for the symptomatic population and control groups or other interventions for the asymptomatic participants.The primary outcomes were changes in range of motion (ROM) and pressure pain thresholds (PPT) after the MET application in the asymptomatic participants and change in the pain and disability indexes after the MET application in the symptomatic population. PPT, the pain indexes and disability indexes, for this review varied across studies. Another outcome that was analyzed across the review for both asymptomatic and symptomatic participants was the MET protocol used. Each protocol will be considered in terms of number of contractions, seconds which the contraction is applied to the targeted joint, the contraction force applied, the relaxation phase and the stretch, if applicable.The literature search was conducted on the following databases: Cochrane Library, MEDLINE, NLM Pubmed, and ScienceDirect. Due to the extensive nature and variety of topics covered by the search, there was no limit to the search period, however the search ended on June 2018. The search strategy was conducted using the following keywords: muscle, energy, technique and MET. These keywords were used as follows: muscle AND energy AND technique OR MET.After the initial title screening, inclusion and exclusion criteria above described were applied for abstract selection. The inclusion criteria were: (1) studies had to be peer-reviewed, (2) studies had to be performed on adult subjects, (3) studies had to clearly specify the MET procedure used, (4) studies had to report an objective outcome and (5) studies concerning symptomatic patients had to be RCT’s. The exclusion criteria were: (1) Non-English manuscripts, (2) studies performed on children, (3) non-RCT’s studies, (4) studies that did not specify a MET procedure. Following the inclusion of the selected manuscripts, these were divided into two groups: those applying MET on asymptomatic participants and those applying MET on symptomatic participants. Duplicate records, abstracts and unpublished materials were removed. Full-text copies of the retrieved records were screened for the same criteria. If the full text copy was not retrievable through database or electronic search, the corresponding authors of the studies were contacted. If no response was received or the authors were not able to provide a copy of the selected manuscript, the article was excluded from the investigation. Reference lists of relevant publications were also screened.Selection was conducted independently by two reviewers. Any disagreement was resolved through negotiation. All of the identified records from each database were combined into a single End Note file  and subsequently screened for relevance using title and abstract. The full text of relevant studies was retrieved and assessed for eligibility against the inclusion criteria set above. The PRISMA flow diagram Fig.  illustraThe methodological quality of the randomized controlled trials was assessed using the PEDro scale. The PEDro scale is a 10-item tool designed to reliably assess the quality of physical therapy-based RCT’s, based on a 10-item checklist , where tThe studies included in the qualitative synthesis were classified according to the screened population (asymptomatic vs RCT’s). For each group, descriptive statistics were performed for the main variables and other presented indexes using STATISTICA for Windows .A total number of 1921 manuscripts were initially identified after the first search strategy in the four databases. After the application of the inclusion and exclusion criteria on each article’s title and abstract, 71 records were considered eligible, 18 records were removed as duplicates and 53 records were screened as full-text. Of the 53 records screened, 27 were removed due to non-MET studies, non-English manuscripts, missing data, not meeting the inclusion criteria or not being RCT’s. A final number of 26 original studies were included in the in the qualitative synthesis . The overall PEDro risk of bias score of all the included studies was 6.4/10. The lowest scores for the included studies were achieved in item 6 (blinding of therapist) and item 7 (blinding of assessors) for scores of 1.4/10 and 2.9/10, respectively. A breakdown of PEDro scores for each trial is shown in Table Of the twelve included studies, ten investigated the effects of MET on joint ROM , 37, 41,All of the above protocols were applied on the restricted side of a targeted joint in the asymptomatic subjects. Different procedures for applying MET were presented by different authors. Ballantyne et al.  applied Fryer et al.  investigp < 0.001) after a six-week intervention and decreased forward scapular position when compared to a control group which did not receive any intervention . The scapular position was measured with the participant with the shoulders touching a wall. The perpendicular distance from the wall to the anterior portion of the acromion was the calculated forward scapular position. A similar protocol of Laudner et al. [Laudner et al.  applied r et al.  was usedr et al.  and was Moore et al.  applied The study performed by Shadmehr et al.  applied Two primary protocol types are implemented in the use of MET: the Greenman and Chaitow. The Greenman protocol consists of four contractions of seven to 10 s each performed at 40% of the patient’s maximal force with a three-second relaxation phase between contractions. The Chaitow Protocol consists of three contractions of seven to 10 s each performed at 40% of the patient’s maximal force with a three-second relaxation phase followed by a 30 s stretch applied at the palpated barrier of restriction. Schenk and colleagues  applied The goal of the prescriptions for MET in the studies evaluated in this review were variable. Of the fourteen included studies, seven investigated the effects of MET on chronic pain , 40, 42,The number of sessions for a typical MET prescription varied considerably. The range of those evaluated in this review is one to eighteen. Of the included studies, four applied MET within a single session , 14, 39,2 and TENS for 10 min 50–100 Hz), revealing that MET was the most beneficial treatment to manage pain and increase ROM. The Visual Analog Scale (VAS) used to assess pain decreased five points compared to baseline in the MET group and three points for the conventional therapy. The Oswestry Disability Index (ODI) also decreased 18% after six treatments in the MET group and 13% in the conventional therapy group. Ulger et al. [p < 0.001) and the ODI  compared to spinal mobilization .Two of the retrieved records regarding chronic pain investigated the effects of MET on LBP. The study by Bindra et al.  applied r et al.  aimed top < 0.0001, exercise intervention: pre 34.50 ± 5.92 compared post 22.80 ± 6.79, p < 0.01), reported VAS pain , and forward head posture . The sample had been compared to an exercise intervention, which revealed a significant difference between the two groups in all measures .Three of the retrieved records regarding chronic pain investigated the effects of MET on CNP. Sakshi and colleagues  investigp < 0.001 NDI: pre 17.25 compared to post 8.03, p < 0.001) compared to the stretching group  (Intragroup difference VAS p = 0.020 and NDI p = 0.024). Cassidy et al. [Phadke et al.  comparedy et al.  comparedy et al.  comprisep < 0.05) after the MET protocol  compared to the static stretching protocol . The protocol was applied for eighteen sessions over a period of 4 weeks.One of the studies included in this review investigated the effects of MET in patients with a history of at least a month of plantar fasciitis and compared the effects with those from static stretching. The MET protocol used by Tanwar et al.  compriseKüçükşen et al.  analyzedp = .495, VAS MET: 7.39 ± 1.07 compared to corticosteroid injection 7.17 ± 1.07, p = .330, DASH MET: 46.73 ± 11.88 compared to corticosteroid injection 45.63 ± 10.40, p = .666). At the six-week evaluation, all measurements improved in both the corticosteroid injection group and the MET group, however the values for the corticosteroid group were significantly greater than those of the MET group . At 26 and 52 weeks, the MET group scored significantly better in all measurements. The corticosteroid group at 26 and 52 weeks had the tendency to relapse . No patients in the MET group reported side effects from the treatment, whereas three participants out of forty-one experienced side effects in the corticosteroid injection group.The study assessed pain-free grip strength, reported VAS values and the “Disabilities of the Arm, Shoulder and Hand questionnaire (DASH)”, respectively. The grip strength of the affected side was presented as a ratio of the maximum grip strength of the unaffected side. The measurements were performed at baseline, 6, 26, and 52 weeks after the treatments  in the MET group (pre 45 vs post 7 with a mean decrease of 83%) compared to the control group . Another study by Selkow and colleagues [p = .04) whereas it increased in the control group treated with a sham therapy from 1.4 to 3.5.Only two studies analyzed the effects of MET on acute pain. Wilson et al.  evaluateAll of the studies analyzing MET and myofascial trigger points applied the techniques to the upper trapezius. All patients were tested for active trigger points, defined as a tender nodule in a taut band that referred pain beyond the area of contact. The patients were treated if suffering from non-specific neck pain, defined as non-articular or non-systemic or had painful symptoms in the upper trapezius.Nagrale et al.  comparedp < 0.01; mean ROM contralateral flexion: pre 39.8 ± 4.6° compared to post 45.2 ± 4.7°, p < 0.01; mean ROM ipsilateral rotation: pre 70.4 ± 5.7° compared to post 73.4 ± 5.1°, p < 0.01. Ischemic compression: pain thresholds pre 1.7 ± 0.3 kg/cm2 compared to post 2.9 ± 0.4 kg/cm2, p < 0.01; mean ROM contralateral flexion: pre 39.8 ± 5.1° compared to post 46.8 ± 5.4°, p < 0.01, mean ROM ipsilateral rotation: pre 71.2 ± 5.7° compared to post 76.5 ± 6.7°, p < 0.01). However, the improvements measured a week after the treatment seem to have been better maintained in the ischemic compression group compared to the MET group.A similar study design implemented by Oliveira-Campelo et al.  compriseSadria et al.  comparedThe last included study in this review analyzed the effects of MET on latent trigger points  comparinp = 0.855. Kyphosis angle in relaxed sitting: MET increase from baseline 5.16 ± 3.90°; Exercise intervention increase from baseline 5.18 ± 4.25°, p = 0.935. Muscle strength: MET increase from baseline 26.76 ± 22.65 N; Exercise intervention increase from baseline 27.28 ± 16.50 N, p = 0.175).Of the retrieved records, only one study analyzed other types of dysfunctions than those described above. The study of Kamali et al.  applied A summary of the MET procedures is shown in Table The aim of this review was to understand the efficacy of MET on pain and joint range of motion, and to understand the differences between the different MET protocols in symptomatic and asymptomatic subjects. The quality assessment showed a “moderate to high” quality level of the included RCT’s.The analyzed protocols for the asymptomatic subjects, comprised three or four contractions  ranging from three to 10 s in duration (mode and median: 5 s) with contraction forces ranging from 25 to 75% of the patient’s maximal force (mode and median: 40%), a relaxation phase ranged between 0 and 5 seconds (mode and median: 3 s) and the stretch phase, which was not applied in 10 of the 14 protocols.The only protocol directly comparing MET with and without a stretch was that of Smith et al. , in whicIn symptomatic patients, the protocols comprised three to six contractions (mode and median: 4 contractions) extending in the range of 5 to 10 s, (mode and median: 8 s) with contraction forces ranging from 20 to 75% of the patient’s maximal force (mode and median: 20%), a relaxation phase between 0 and 10 s (mode and median: 3 s) and a stretch phase that was not present in 9 of 14 protocols. When reported, the stretch phase ranged between 20 to 30 s (mode and median: 30 s).The range of contraction forces for MET protocols suggested by Chaitow  ranges bThe results of the studies assessing the effects of MET on chronic LBP all showed decreases of the pain and disability indexes (VAS and ODI). In particular, Bindra et al.  comparedOnly two studies analyzed acute LBP , 8 havinIn regards to CNP, MET were compared to an exercise intervention, a stretching intervention and a mobilization intervention. In all three studies pertaining to CNP, pain and disability indexes were analyzed and showed that MET were the superior treatment compared to the other interventions for reduction in pain and disability. The study intervention periods range between 2 and 8 treatments.The only study evaluating plantar fasciitis advocated an increase in ROM in parallel with decreased pain scores after the manipulative treatment . UnfortuKüçükşen and colleagues analyzed the effects of MET and corticosteroid injection after six, 26 and 52 weeks. Interestingly, the early phase of the treatment following the injection of corticosteroids was more beneficial in reducing pain and increasing pain free grip strength. However, the authors demonstrated a relapse after 26 and 52 weeks in the injection group, whereas a continuous reduction in elbow pain was shown in the MET group from 6 to 52 weeks.Four studies evaluated the effects of MET on myofascial trigger points , 38, 39 There was a large heterogeneity in the MET protocols utilized. Of the 26 included studies, only 15 provided a full description of the treatment protocol . Therefore, it is difficult to generally state which protocol is the most beneficial.Future studies evaluating MET effectiveness are encouraged in order to identify which procedure may be more beneficial when treating different musculoskeletal disorders.MET are effective in improving reported pain, disability and joint range of motion in both asymptomatic subjects and symptomatic patients. The studies evaluated in this review have provided evidence that MET are specifically effective for alleviating chronic pain of the lower back and neck and chronic lateral epicondylitis. There is also evidence supporting MET as a beneficial therapy for reducing acute lower back pain and improving the related disability indexes. However, further evidence is needed to confirm MET as an effective treatment for plantar fasciitis and other musculoskeletal disorders. A definitive protocol for MET application, due to the heterogeneity of the results, could not be identified, and a future evaluation of the parameters of MET prescription is suggested.


The aim of this paper is to study experimentally the effect of marble powder and green sand as partial substitute for fine aggregate on the strength and durability of M40 grade concrete. The use of metakaolin as a pozzolanic admixture by using as binder replacement is also studied to assess the properties with respect to fresh and hardened state. Several formulations were prepared with constant water-binder ratio 0.4 and varying percentages of marble powder and green sand. The results indicated that the properties of concrete were much enhanced by extent incorporation of marble powder and green sand as fine aggregate and metakaolin for cement when compared to normal concrete. The microscopic studies also confirmed the viability of using green sand and marble powder as fine aggregates. Recent decades have witnessed the rapid demand for river sand as fine aggregate which is one of the most essential ingredients in the production of concrete . Modern Previous research works have previously investigated the effects of using foundry sand ,18,19 anHence the value of the present study lies on the fulfilling of the practical design requirements such as strength and durability of concrete mixes manufactured using replacements of fine aggregate by both marble powder and green sand. In addition the synergistic effect of marble powder and green sand together with a pozzolanic admixture (metakaolin) on the concrete properties addressed in detail thereby not only saving the exhaustion of natural aggregates but also reducing the efficiency of using industrial wastes as fine aggregate replacements.The main objective of this research is to investigate the feasibility of using marble powder and green sand as fine aggregate in concrete production. The effect of metakaolin replacement in cement is also investigated. The mechanical properties of the hardened concrete made of green sand and marble powder were studied at various ages. The microstructure and hydration products were also investigated to assess the impact of using green sand on marble powder as partial replacement for fine aggregate.Ordinary Portland cement (OPC) 43 grade conforming to Indian standard BIS 8112-1989  is used The concrete mixes were manufactured in the proportion of 1:2.08:3.57 corresponding for Binder: Fine aggregate: Coarse aggregate, as per BIS 10262-2009  referrinThe fresh state properties of the concrete mixes were determined using slump test conforming to IS1199-1959 and the hardened state properties were analyzed by conducting compressive strength on 150 mm concrete cube specimens, flexural strength test on 100 mm × 100 mm × 500 mm prism specimens and split tensile strength test on 150 mm diameter × 300 mm height cylindrical specimens at several ages conforming to BIS516-1959 . Impact The workability of the concrete mixesis conducted as shown in The flexural strength development of the concrete mixes at various ages of 14, 28, 56 and 90 days are shown in The splitting tensile strength test  setup on cylinder specimen is shown in The impact strength apparatus and specimens at failure is shown in The water absorption values of the concrete mixes with and without the fine aggregate replacement are provided in The XRD studies  done to The morphology of the concrete mixes as obtained from the Scanning Electron Microscope Equipment  and resu2 values are also shown in With the help of the experimental data, graphs were plotted between split tensile strength and flexural strength of concrete mixes at various ages. The linear relationship between split tensile strength and flexural strength is obtained through the predicted equation and their corresponding regression coefficient RThis study mainly aims at utilizing marble powder and green sand as partial substitute for fine aggregate and metakaolin for cement. From the experimental results obtained the following conclusions can be withdrawn.The workability of the concrete was very much influenced due to the addition of green sand and marble powder. The relative decrease in the workability was achieved due to the increase in amount of water required by the aggregates and the normal sand. Moreover decrease in the workability may also be caused due agglomeration and compounding effect exhibited by the metakaolin particles.An increase in the compressive strength of all the mixes occurred at various ages. The filler effect and the pozzolanic reaction of metakaolin with calcium hydrate also contributed to the increase in the strength of the concrete. This enables the use of marble and green sand as construction materials by minimizing the utilization of the river sand as fine aggregate and the reduced production of cement by replacing with metakaolin.The flexural strength of the concrete mixes was enhanced due to the fine aggregate replacement and metakaolin replacement. The use of marble powder and green sand within 15% was found to be optimum to increase the flexural strength of the concrete when used in combination with metakaolin as cement substitute.The splitting tensile of the concrete was also improved up to 15% beyond which the decrease in the reduction in the split tensile strength was observed. This shows that using 15% green sand and marble powder was found to be adequate as far as the strength parameters are concerned.The impact strength of the concrete was much enhanced for the concrete containing metakaolin as cement replacement and marble powder and green sand as fine aggregate replacement that proved to be efficient in absorbing the impact energy acting on the concrete.The use of marble powder and green sand as fine aggregate replacement created a favorable effect on reducing the porosity of the concrete. The reduction in the water absorption caused a decrease in the voids and is responsible for the improvement in the mechanical strength and impermeability properties of concrete. The addition of metakaolin caused stronger bonding of the cement paste and strengthens the adherence of the cement and the aggregates by the formation of CSH gel which is also responsible for the reduction in the porosity values.The X-ray diffraction studies also showed the minimal presence of calcium hydroxide that confirmed the consumption of calcium hydroxide in the hydration reaction which is responsible for the dense microstructure of the concrete by the addition of CSH gel. The reduced calcium hydroxide peaks inherits the formation of CSH gel that is responsible for the improved strength and durability of the concrete.The SEM images of the concrete also showed reduction in the voids in the concrete and the well distributed CSH gel that effectively bonded the fine aggregates with the cement matrix. The SEM micrographs are coherent for the obtained mechanical properties and the morphology of concrete mix and shows that the marble powder and green sand in combination with metakaolin can be used for making good quality concrete with higher strength.2 values indicate the conformity of the interrelationship between the variables.The prediction models obtained from the experimental data showed the relationship between various strength parameters of the concrete and the obtained RThe final conclusion can be withdrawn that when green sand and marble powder are used as fine aggregate replacement and metakaolin as partial substitute for cement the concrete mixture with high strength properties compared to that of the normal concrete can be obtained. The incorporation of these powdered fine aggregates instead of normal river sand proves to be beneficial to obtain concrete with higher strength. Moreover this type of concrete produced is also environment friendly and economically feasible by large utilization of the waste marble powder and green sand.


The main objectives of this study are to develop a non-destructive test method for evaluating delamination defects in concrete by the Impact-echo test using multi-channel elastic wave data and to verify the validity of the proposed method by experimental studies in the laboratory. First, prototype equipment using an eight-channel linear sensor array was developed to perform elastic wave measurements on the surface of the concrete. In this study, three concrete slab specimens (1500 mm (width) by 1500 mm (length) by 300 mm (thickness)), with simulated delamination defects of various lateral dimensions and depth, were designed and constructed in the laboratory. Multi-channel elastic wave signals measured on the three concrete specimens were converted to the frequency-phase velocity image by using the phase-shift method. A data processing method was proposed to extract the dominant propagating waves and non-propagating waves from the dispersion images. The dominant wave modes were used to evaluate delamination defects in concrete. It was demonstrated that the surface wave velocity values were useful for characterizing the shallow delamination defects in concrete. In addition, the peak frequency of non-propagating wave modes extracted from the dispersion images gives information on the lateral dimensions and depths of the delamination defects. This study also discussed the feasibility of combined use of the results from propagating and non-propagating wave modes to better understand the information on delamination defects in concrete. As will be discussed, the multi-channel elastic wave measurements enable more accurate, consistent, and rapid measurements and data processing for evaluation of delamination defects in concrete than the single-channel sensing method. A delamination defect in concrete is a subsurface fracture plane that is caused by corrosion of embedded reinforcing steels in concrete b,c. The The impact-echo test has been proven to be an effective evaluation of delamination defects in plate-like concrete elements ,6,7. HowThere are many kinds of research devoted to improving the conventional IE testing of concrete. Some researchers proposed a method to evaluate the pressure (P) wave velocity of concrete for determining the thickness of concrete by using the spectral analysis of surface waves (SASW) test . In the The primary purpose of this research is to develop an advanced IE test method for evaluating delamination defects in concrete using multi-channel elastic wave signal analysis. First, prototype equipment, supporting eight-channel elastic wave measurements, was developed and used to evaluate delamination defects in concrete specimens in the laboratory. Second, a signal processing method was proposed to extract important wave modes for the evaluation of delamination in the IE test. Third, the validity of the prototype equipment and data interpretation method was verified by comparison of experimental results. As will be discussed, the multi-channel elastic wave measurements enable more accurate, consistent, and rapid measurements and data processing for the evaluation of delamination defects in concrete compared to the single channel-sensing method.s) and normalized wave number (ξ = hk/π) domain. The dynamic response of concrete over delamination defects is generally measured by a sensor located closed to the impact source (about 30 to 50 mm). The Fourier transform of the time signal shows peaks at certain frequencies, which are interpreted as dominant non-propagating wave modes (or resonance modes).There have been many prior researches that used dispersive behavior of elastic waves for non-destructive evaluation (NDE) of various structural elements ,13,14,15P waves between the top and bottom surfaces of a solid plate. The resonance frequency of the thickness stretch mode is the cut-off frequency of the first symmetric Lamb mode [fsZGV1). The S1-ZGV frequency can be used to determine the thickness, h, of a crack-free plate when P wave, pC, the velocity of concrete is known byβ is a correction factor that depends on Poisson’s ratio of concrete [Sf1 and Sfb2. In this study, concrete with relatively deep delamination with a depth of 250 mm was also characterized by an analysis of the S1-ZGV mode. Given SfZGV1 and pC, the depth of the relatively deep delamination can be estimated reliably using Equation (3). In contrast, relatively shallow delamination defects could be characterized by flexural vibration modes. Flexural vibration modes can be interpreted as non-propagating waves as a consequence of multiple reflections of Lamb waves at delamination [Two sets of resonance modes associated with Lamb waves in a plate are generally used to detect and characterize delamination defects in concrete using IE testing, which includes the thickness stretch mode and the flexural vibration mode . The freamb mode . Howeveramb mode ,20. The concrete , and is concrete ,22,23. Nmination . It was nditions . The ana defects . 3), river sand (701 kg/m3), crushed coarse aggregate (1049 kg/m3), and water (165 kg/m3). The mixture was designed to have a minimum 28-day compressive strength of 35 MPa. The concrete slabs were water-cured for seven days after casting. The actual measured 28-day strength was higher than the design with a value of 37.5 MPa. The assembled concrete slabs were designed to contain simulated delamination defects using double-layered thin film with a thickness of 50 µm of various sizes and at two different depths  × 1500 mm (width) × 300 mm (depth) see , which ipths see : shallow2)) [Prototype equipment for multi-channel elastic wave measurements on the surface of the concrete slab, shown in 2)) . A sensoThe prototype equipment was used to measure dynamic responses of test regions on the three concrete specimens. Each measurement using the eight-channel sensor array covers a test line of 200 mm long. In this study, the sensor array was kept parallel to the vertical axis with the middle of the sensor at each test point, which is presented as a black solid circle in r =  at the minima of first dominant time wave signals. j represents the type of windowed signals , t is time, The windowed space and time domain signals, t method  as folloA resulting dispersion curve, A resulting dispersion curve, dS1ZGV) (see ZGV) see . A deep c) seem to be in an acceptable level  resulted in the low peak frequency values equal to about 2.1 kHz, 4.1 kHz, 2.1 kHz, and 2.6 kHz, respectively. These values were lower than that of the thickness stretch mode measured on the solid concrete. As seen in R, as the frequency increases from zero to infinity. In this study, the surface wave velocity of concrete was evaluated by averaging the phase velocity of A0 Lamb mode in a frequency range from 10 kHz to 15 kHz. Resulting surface wave velocity over delamination defects are summarized in Theoretically, the phase velocity of A0 Lamb wave mode gradually increases from zero to the surface wave velocity, Vi is the index of experimental data, N is the number of data, a0 = 3.3, a1 = 2026, a2 = 2492, a3 = 6494, a4 = −45.91, b0 = 291.9, b1 = 3378, b2 = 3337, b3 = 6714, and b4 = 1. dA0) by the analysis of the A0 Lamb wave mode. The estimation error (edA0) increases as the lateral dimension decreases. In particular, the estimated depth of DL2 with a relatively smaller width (150 mm) was significantly overestimated compared to the as-built size, with an estimation error of 112%. Therefore, lateral dimensions should be sufficiently large (at least 300 mm) to obtain relatively accurate depth estimation by the A0 Lamb wave mode analysis. In addition, the depth of shallow delamination defects was estimated by finding an optimum analytic model that results in the least RMSE (root mean square error) compared to the experimental curve as follows,Based on the observations in the previous sections, delamination defects in concrete were visualized by mapping the three critical parameters, which include surface wave velocity, peak frequency, and depth of delamination defects. The three delamination maps were constructed based on 100 by 100 grid points. The data values between the measured data points  were obtained by interpolation using the ‘kriging algorithm’. The maps were created by a commercially available mapping program, Surfer .t-test. This statistical result indicates that surface wave velocity could be a useful parameter to identify the concrete with shallow delamination defects from solid concrete. However, no significant difference was found between Group 1 and Group 2. Still, it should be noted that there are several reasons explaining the decrease in the surface wave velocity of concrete  in actual concrete structures [Furthermore, a statistical analysis was performed to confirm the effectivity of the surface wave velocity values as critical parameters for evaluating delamination defects in concrete. Test regions on the three concrete specimens were classified into three groups: ‘Group 1’ over solid concrete, ‘Group 2’ over shallow delamination defects, and ‘Group 3’ over deep delamination defects. The surface wave velocity data in the three groups follow the normal distribution, which was checked by the Kolmogorov-Smirnov (K-S) test . Table 2ructures . Therefot-tests, there is a significant difference between the means of Group 1 and 3 and Group 1 and 2 at the 5% significance level.It is of interest to engineers in infrastructure management agencies to estimate the depth of delamination defects and the thickness of concrete structures. (1)dS1ZGV or edA0, of the depth of delamination defects from the S1 ZGV Lamb mode and A0 Lamb mode, respectively: lateral dimensions should be at least 300 mm to obtain relatively accurate depth estimation from the two important wave modes. According to experiences of the authors from the laboratory and field tests, the test method using the S1 ZGV Lamb mode can be applicable to the delamination defects with a depth greater than 150 mm; and the analysis of A0 Lamb wave mode to the shallow delamination defects with a depth less than 100 mm.The depths of the delamination defects in concrete slab specimens were estimated by the two important wave modes: non-propagating waves (S1 ZGV Lamb mode) and propagating waves (A0 Lamb wave mode). The dominant non-propagating waves were effective for relatively deep delamination (250 mm in this study), while the propagating waves are valid for relatively shallow delamination (50 mm in this study). The estimated depths of delamination defects have a good agreement with the as-built depths in the simulated concrete slabs in this study. Test results show that the size of delamination defects have a great influence on the estimation errors, e(2)c) ranging from 4.6% to 13% without regard to the size of delamination defects considered in this study.It was demonstrated that the non-propagating waves associated with flexural vibration modes over relatively shallow delamination defects in concrete are effective for estimating the lateral dimensions of the defects. The estimated lateral dimension of the shallow delamination defects  in the concrete slab specimens in this study show a good agreement with the as-built sizes, with the estimation errors (e(3)Delamination defects in concrete slab specimens were visualized by mapping the three critical parameters, which include surface wave velocity, peak frequency, and depth of delamination defects. The delamination maps were effective for visualizing the areal extents and depths of delamination defects in concrete, which gives a way of estimating the damage volume in concrete.(4)There are two important benefits of using the multi-channel elastic wave measurements for the evaluation of delamination defects in concrete. First, it enables us to simultaneously extract two important wave modes (A0 and S1 ZGV Lamb wave mode). Second, the fusion of data from two important wave modes could result in a more accurate and consistent evaluation of delamination defects in concrete.(5)The results in this study were obtained from concrete slab specimens with simulated delamination defects in the laboratory. More studies are still needed to obtain more general conclusions of the feasibility of multi-channel elastic wave measurements.Delamination defects in concrete slab specimens were evaluated by analyzing multi-channel elastic wave signals. In this study, a prototype eight-channel sensing device was developed for elastic wave measurements on the surface of concrete. Multi-channel elastic wave signals were converted to a frequency-phase velocity image by the phase-shift method. A data processing method was proposed to extract the two useful wave modes (A0 and S1 zero group velocity Lamb wave modes) from the dispersion image. The wave modes were used to characterize the depth and lateral dimensions of delamination defects in concrete. The validity of the data interpretation method was verified by comparison analysis between as-built and estimated results measured from concrete slab specimens with simulated delamination defects of various sizes and depths in the laboratory. The specific conclusions obtained from this study are summarized as follows: