Compared with the conventional drainage strengthening techniques, the precast concrete segment assembly strengthening method (PCSAM) is regarded as a fast, more economical, and traffic-friendly underwater strengthening method for damaged bridge piers and piles, as the drainage procedure can be omitted. However, this method still has some disadvantages, such as strength loss of the filling material, debonding of the interface due to shrinkage of the filling material, poor connection effects, and poor durability of the segment sleeves. To solve these problems, the PCSAM is improved in this study by using self-stressed anti-washout concrete (SSAWC) as the filling material and by developing a lining concrete segment sleeve (LCSS) by referring to the design theory for shield lining segments. Six specimens are designed and prepared with consideration of the influential factors, such as the self-stress, thickness of the filled concrete, and concrete strength of the LCSS, then the monotonic axial compression test is carried out to investigate the improvements in the axial compression properties of the specimens. Accordingly, extended parametric analyses are performed based on the established numerical models. Finally, the calculation formula for the bearing capacity is proposed based on the analysis results. The results indicate that the SSAWC can provide initial confining compressive stress in the core region of the piers, in addition to increasing the bearing capacity and ductility of the specimens. The improved LCSS segment connection is more reliable and increases the strengthening efficiency. The influence of self-stress on the bearing capacity of the specimens is cubic and the influence of the filled concrete strength on the bearing capacity of the specimens is nonlinear. The calculation formula for predicting the bearing capacity of axially compressed columns possesses good applicability and can be used as a reference for practical engineering. Substructural components, such as piers and piles, are critical to the safety of bridge structures. Due to the low requirements of design codes decades ago, material degradation, and environmental erosion, the existing components generally suffer from delamination of the concrete covers, exposed ribs, and riverbed cutting. These defects are not easy to be detected because the substructure components are almost underwater throughout their life cycle, which limits the function of such bridges, even leading to collapse. Therefore, many conventional strengthening methods and techniques, such as the bonded steel plate method , enlargiA number of undrained strengthening techniques have been developed and applied to practical engineering in the past decade, such as the jacket strengthening method , FRP undBased on the PCSAM, this paper proposes a new undrained strengthening method named the improved precast concrete segments assembly method (IPCSAM), which takes advantage of three theoretical reinforcement techniques, namely the increasing section method, outer sleeve method, and prestressing method. The IPCSAM proposed in this paper not only uses self-stressed anti-washout underwater concrete (SSAWC) as the filling material, but also improves the connection of the segment sleeve, which is referred to as the shield lining segment. The SSAWC, as the filled concrete, can not only cut down the strength loss of the underwater concrete ,11,12, bThe axial compression performance of the strengthened columns is so significant that numerous studies have investigated this topic. Fakharifar  found thThis paper attempts to investigate the strengthening effect of the IPCSAM and the axial compression performance of the strengthened columns. Firstly, the implementation strategy for the IPCSAM is introduced. Then, 6 specimens are prepared by taking account of influential factors, such as self-stress, the thickness of filled concrete, and the concrete strength of the LCSS, while the mechanical properties of the specimens are also studied under axial compression loading. Next, the extended parameter analyses are carried out via numerical simulations. Finally, based on the experimental results and extended parameter analyses, the calculation method for the bearing capacity is established for the components strengthened with the IPCSAM.The use of self-stressed anti-washout underwater concrete (SSAWC) is one of the key strategies for implementing the IPCSAM, because the filling material connects the components and segment sleeves and directly affects the mechanical properties of the strengthened components. Wu and Jiang  developeN normal Portland cement from Fujian Cement Inc. , a fiber-type anti-dispersion agent named SBTNDA, and the HME-III low-alkali concrete expansive agent produced by the Jiangsu Soubotte Company  were chosen. A polycarboxylate superplasticizer was employed in these tests based on experimental results from Khayat 24], the (3)According to the calculation method in , the imp(4)According to , the cal(5)According to the design data for previous bridges, the concrete strength grade of the substructure mostly did not exceed C30, so it was assumed that the concrete strength grade of the columns was not greater than C30. At the same time, the substructures constructed years ago had low reinforcement ratios and there were issues related to bar exposure and corrosion. Therefore, the reinforcement of the columns was ignored.According to the results of the tests and extended numerical analysis, the calculation method used for the axial compression bearing capacity of concrete members strengthened involving the enlarging section method found in , and Xu’N) was proposed as follows:N0, sN, and pN are the bearing capacity of the column and the filled concrete, the bearing capacity improved by the confinement, and the bearing capacity improved by self-stress, respectively.Based on assumption (1), the calculation formula for the axial compression bearing capacity of the strengthened specimens (N0) was proposed as follows:φ is the stability coefficient of members, taking the value according to code 20], were(1)The IPCSAM has good strengthening effects on underwater pier strengthening structures without causing undraining. Compared with the unreinforced column, the axial compression bearing capacity and peak strain of specimens strengthened by the IPCSAM increased by 90–130% and 30–60%, respectively. This indicates that the bearing capacity and ductility of the strengthened specimens were considerably improved;(2)As the filling material, the SSAWC can reduce losses in underwater strength in concrete and can produce expansion and self-stress. The self-stress not only improves the bond strength between the filled concrete and the adjacent member, but also provides a preloading effect on the column, which can improve the strength and ultimate strain of the concrete. Compared with the specimen strengthened by AWC, the bearing capacity of the specimen strengthened by the SSAWC increased by 18% and the strengthening efficiency increased from 0.71 to 0.86;(3)The LCSS improvement caused by the shield lining showed reliable connection performance, which remained in good condition when the specimen was broken. In the test, the LCSS showed good integrity and confinement, which could increase the bearing capacity of a specimen. Compared with the PCSAM, the strengthening efficiency of the specimen strengthened by the IPCSAM increased from 0.65 to 0.71;(4)The strength of the filled concrete, the strength of the LCSS concrete, and the self-stress were the key parameters affecting the bearing capacity of the specimens. With the increase in filled concrete strength, the LCSS strength, self-stress, and bearing capacity increased accordingly;(5)The calculation formula for the bearing capacity of the strengthened components has been proposed. The findings from this study show that the formula has good applicability and provides a theoretical design basis for the application of the IPCSAM.This study sets out to improve the PCSAM with the SSAWC and the LCSS. Initially, the strengthening effects of the above two improvement measures on the bearing capacity of the strengthened specimens were verified using an axial compression test. Then, the extended parameter analyses were performed by establishing the numerical models. Finally, the calculation formula for the axial compression bearing capacity of the strengthened specimens was established. The following conclusions were made:In addition, preparing the specimens requires a large number of steel molds and careful concrete curing, which takes a lot of time. Considering the time needed and the restrictions on research and development funds, only a small number of specimens were tested and a numerical simulation was conducted. As a consequence, the above-mentioned conclusions and remarks are only validated by limited experimental and simulation results. More experimental data and numerical simulations are needed to validate the proposed formulas in the future.


Antimicrobial stewardship programmes (ASPs) in hospitals are predominantly led by specific ASP physicians and pharmacists. Limited studies have been conducted to appreciate non-ASP-trained hospital pharmacists’ perspectives on their roles in antimicrobial stewardship. Focus group discussions (FGDs) were conducted with 74 pharmacists, purposively sampled from the 3 largest acute-care public hospitals in Singapore, to explore facilitators and barriers faced by them in antimicrobial stewardship. Applied thematic analysis was conducted and codes were categorised using the social–ecological model (SEM). At the intrapersonal level, pharmacists identified themselves as reviewers for drug safety before dispensing, confining to a restricted advisory role due to lack of clinical knowledge, experience, and empowerment to contribute actively to physicians’ prescribing decisions. At the interpersonal level, pharmacists expressed difficulties conveying their opinions and recommendations on antibiotic therapy to physicians despite frequent communications, but they assumed critical roles as educators for patients and their caregivers on proper antibiotic use. At the organisational level, in-house antibiotic guidelines supported pharmacists’ antibiotic interventions and recommendations. At the community level, pharmacists were motivated to improve low public awareness and knowledge on antibiotic use and antimicrobial resistance. These findings provide important insights into the gaps to be addressed in order to harness the untapped potential of hospital pharmacists and fully engage them in antimicrobial stewardship. Antimicrobial resistance (AMR) is a rising public health threat with new resistant bacteria emerging more rapidly than novel antibiotics being developed, threatening the effectiveness of existing antibiotic treatment options ,2. StudiASPs have increased appropriate antibiotic prescribing and reduced the length of hospital stay without compromising patient safety, providing valuable clinical and economic benefits ,8. HowevPharmacists are well versed in the pharmacology of antibiotics and are expected to review prescriptions and advise physicians on the most appropriate antibiotic choice and regimen . In its Hospital pharmacists have traditionally assumed responsibilities in the governance of medications such as prior authorisation for restricted drugs and provision of audit and feedback to prescribing physicians. However, their perceived role in antimicrobial stewardship has been predominantly advisory in nature and focused on the assurance of drug safety . The rolWhilst many established hospital ASPs include infectious disease (ID) pharmacists, these dedicated ASP pharmacists are by far few in number. Other hospital pharmacists remain an untapped resource for antimicrobial stewardship activities. This study aims to identify facilitators and barriers to non-ASP hospital pharmacists’ participation in antimicrobial stewardship and explore challenges faced in influencing optimal antibiotic use in the three largest acute-care hospitals in Singapore. An in-depth understanding of these factors can influence the development and implementation of interventions to empower hospital pharmacists to play more significant roles in antimicrobial stewardship.Focus group discussions (FGDs) were conducted with non-ASP hospital pharmacists purposively sampled from 1200-bed National University Hospital (NUH), 1700-bed Tan Tock Seng Hospital (TTSH), and 1785-bed Singapore General Hospital (SGH) in Singapore between November 2018 and April 2019.In each of the hospitals, there are 5–10 ASP and 70–80 non-ASP inpatient hospital pharmacists. Non-ASP hospital pharmacists are responsible for dispensing, counselling, supply, and evaluation of medication use. In general, non-ASP pharmacists review the appropriateness of medication use pertaining to the indications, dosing, and administration, and intervene on inappropriate orders. Additionally, the more experienced non-ASP pharmacists join ward rounds with physicians and optimise pharmacotherapy for patients . Since 2Non-ASP hospital pharmacists were invited to participate in the FGDs via invitation letters sent through the pharmacy department in each hospital. Interested pharmacists contacted the study team, who would then purposively select eligible participants into the study to ensure good representation with maximum variation. Participants were subsequently grouped into the respective FGDs based on their seniority and institution to minimise social desirability bias. This was also to ensure that participants were able to freely share their views and opinions during the FGDs.To achieve maximum variation, four FGDs of 4–8 hospital pharmacists who have practised for at least one year in their respective institutions were conducted in each hospital; for each institution, 1–2 FGDs of junior pharmacists, 1–2 of senior pharmacists, and 1 of principal/clinical/specialist pharmacists were conducted. Junior pharmacists were defined as pharmacists with ≤4 years of hospital experience, while senior pharmacists were pharmacists with >4 years of experience. Principal/clinical/specialist pharmacists were pharmacists with specialised training in specific clinical specialties (but not in ASP) who had ≥8 years of experience and spent >50% of their time in direct patient care.Informed consent was taken prior to the commencement of each FGD. Two Research Assistants  trained in qualitative data collection techniques were present as a facilitator and a note-taker during each FGD session. The FGDs were conducted in a closed-door meeting room within the respective hospital premises. To protect their identities, study participants chose their own pseudonyms and were addressed by those chosen pseudonyms during the FGDs. FGDs were audio recorded and lasted approximately 1.5–2 h.A semi-structured interview guide was developed based on existing literature and piloted with ASP pharmacists who understood the roles of non-ASP pharmacists to ensure the topic guide was comprehensive ,19,20. TAll FGDs were transcribed verbatim and reviewed for accuracy by a third study team member. A preliminary codebook was subsequently developed using the interview guide questions and after data familiarisation with the first few transcripts. Three coders coded a randomly selected transcript, and inter-coder reliability was then ascertained by comparing and resolving any discrepancies in the coding process. Data saturation was also discussed. The process was repeated to arrive at the final codebook which was used to code the remaining transcripts. Codes were organised according to the social–ecological model (SEM) , using QIn total, 12 FGDs comprising of 74 non-ASP inpatient hospital pharmacists were conducted . All parFacilitators and barriers faced by hospital pharmacists during antimicrobial stewardship were categorised into the intrapersonal, interpersonal, organisational, and community levels, and summarised in At the intrapersonal level, pharmacists described their roles and responsibilities in antimicrobial stewardship. They emphasised their priorities and shared their clinical experiences and knowledge of antibiotic prescribing, as well as their empowerment to intervene on antibiotic prescribing decisions by physicians.Most pharmacists described their roles in the review of antibiotic orders, and their responsibilities in ensuring the correct dosage and appropriateness of antibiotics. At times, they would suggest the de-escalation of antibiotic therapy. Senior pharmacists mentioned being more involved in discussions with the medical team during antibiotic prescribing, as compared with junior pharmacists.“So when we review the antibiotics, we will check the appropriateness and the duration and all sorts, and when is the best time to oralise or maybe de-escalate the antibiotic. So it depends on the situation, if it’s empiric then we would check whether is it appropriate … we would check the culture to see whether is there any need to change to a more targeted therapy.”“I think sometimes if we round with the physicians then we will discuss upon initiation. What antibiotics to start and also… and later on what antibiotics to de-escalate to.”“As long as the dose is safe for the patient, and the duration is not outrightly wrong, we will generally, let it go.”When intervening on an antibiotic order, most pharmacists prioritised safety over the appropriateness of the antibiotic. When antibiotics prescribed by physicians were not the most appropriate, as long as the prescriptions were within safety limits, pharmacists would allow the antibiotics to be dispensed.“… I think we would [only] really do something if safety… is an issue. We just make sure everything is safe and appropriate, then I think it’s okay.”“Oh I mean certain consultants, they have their own preferred combination of antibiotics [sometimes]… So as long as it is not going to cause major harm… Then we may still go ahead with the antibiotics.”Whilst the majority of pharmacists were confident in their pharmacology knowledge, they often felt incompetent to refute the medical team’s decision. Without knowledge and training in clinical diagnosis, pharmacists felt that it was difficult to determine the antibiotic needs of patients based solely on microbiological results without holistic consideration of patients’ clinical conditions.“From a pharmacist point of view I think we can dose better, I mean our knowledge now is still restricted to dosing, I think with regards to wound examination everything I don’t think we know anything much also.”“So because it has to do with diagnostics, when it has to do with [something] like diagnostics. We, we don’t have a say. We can’t review the chest X-ray and just say the patient has no pneumonia, because we are not clinically trained to do that.”When in doubt, junior pharmacists would consult their seniors, and if discrepancies arose, they would escalate to ASP pharmacists.“If we [are] still stuck then we will check with our colleagues whoever that has more experience in that area, whether they [have] seen this before and if still unable to [resolve], then maybe we will ask those seniors [in] ASP or ICU pharmacist.”Some pharmacists felt that it was necessary to be confident of their recommendations after thorough checks, before suggesting an intervention to the medical team, especially since they had not clinically attended to the patients.“To make recommendations, [it depends on] how complex the case is. So if [it] is so complex, I don’t want [to make] any recommendations, I’m not confident also. Sometimes, for us it’s also a bit of a snapshot.”Moreover, pharmacists lacked confidence that their interventions would improve patient outcomes and expressed concerns over medical liabilities.“If they really heed our advice and patient deteriorates… then whose responsibility [would it be]. This is a very big concern actually.”In many FGDs, junior pharmacists mentioned that they had intervened actively on antibiotic orders at the start of their careers. However, due to multiple failed attempts at changing physicians’ prescribing habits, they had reduced interventions on the appropriateness of antibiotics and instead, focused on ensuring drug safety.“So if we know that this particular team is always doing this thing, then in the future if I see the same thing happen, I won’t… I will know that… I may still try but won’t try so hard.”“Yes, in a way, because there are some consultants that you know that no matter what you say they are not going to change their mind. Then you don’t bother saying anymore.”As such, many pharmacists shared that their contributions towards antimicrobial stewardship were very limited.“There…there’s very limited, things we can do. Because… Firstly, we’re not able to prescribe and secondly, uh, they [physicians] can use reasons like “I think the patient is clinically unwell”. Yes. So…there’s no way that you could actually… argue back.”At the interpersonal level, pharmacists shared their experiences and perceptions of working with physicians during antibiotic prescribing and educating patients and caregivers.Across all institutions, pharmacists shared that they were commonly consulted by physicians on antibiotic dosing and frequency for patients with impaired renal function, dosing suggestions for antibiotics that require therapeutic drug monitoring, and antibiotic choices for patients with multiple drug allergies.“It’s culture directed, they don’t know what to choose, or [only] if the person is penicillin allergic, or a lot of allergies, only then they will ask you. Most of the time, if it’s a clear cut situation, then they will make a decision on their own.”Frequently, pharmacists felt that their concerns about inappropriate use of antibiotics could not be explicitly communicated to prescribing physicians, and their suggestions were often ignored, as they were not formally part of the clinical decision-making process for antibiotic prescribing.“I do think sometimes there’s a psychological barrier to communicate with the team… I guess there’s a need for us to actually really speak up… [like] our idea[s] and our concerns and communicate not just with HO [House Officer], MO [Medical Officer], [but] try to move up and because sometimes we are afraid to actually voice out our concern”“Like for example the surgical disciplines, they tend to start antibiotics without any strong indication. Or they will just put an IDC [indwelling catheter] and then they will start ciprofloxacin, sometimes at the wrong doses. But [if] you ask them to off, [they will reply] no, it’s the consultant’s decision.”Some pharmacists emphasised that it was particularly difficult to intervene on antibiotic choices for senior physicians, as they might favour the use of certain antibiotics based on their past clinical experiences and/or personal preferences. Most of their recommendations were usually overridden by the decision of the senior physician in the primary medical team.“I mean I guess there [are] always certain teams or physicians who probably have their own rationale or mindset in terms of like why would they still prefer to use certain choices. I mean they probably have certain experience in the past.”“…so when we do the interventions, or we can, we talk to the junior doctors about that, uh they will say follow the consultants, so they will follow the consultants past experience…”This was despite the fact that physicians might not have the best knowledge on the appropriate use of antibiotics.“I think one very common one is [that] younger doctors might not know the concept of ESBL [extended-spectrum beta-lactamase] like some bacteria that is resistant to. So the panel will reflect this sensitive to Augmentin bu-, but we’re usually taught that the preferred one is the carbapenems. Then the doctor will question and say “It’s sensitive so why shouldn’t I use it?”However, the pharmacists also mentioned that barriers to effective interventions could be mitigated by joining the medical rounds with physicians and participating in discussions at the initiation of antibiotics.“Usually we review them when the doctor orders the antibiotic. In terms of indication, the drug doses. And, in doubt, we clarify with the team regarding the use. Sometimes if we round with the physicians, then we will discuss upon initiation.”Overwhelmingly, hospital pharmacists felt that physicians tended to accept the antibiotic recommendations from ASP pharmacists or infectious disease physicians more than theirs, despite them providing the same recommendations.“Even if it’s just for prophylaxis…I do not know a lot about the surgical stuff, I do not have a very good solid reason to tell them “hey you must stop now…” And partly what we say does not carry the same weight as what the ASP [says].”“I mean if the intervention comes from a ID consultant. Then all the more [it] would [be] accept[ed] compared to [the intervention] coming from [a] pharmacist right?”“So what I recommended wasn’t wrong, It’s just that it needs to come out from a person that [is] more trustable.”Most pharmacists interacted with patients and their caregivers when preparing patients for discharge. The pharmacist would educate patients or their caregivers on the purpose of the antibiotics and their proper use. They played the role of educators by clarifying patients’ and caregivers’ doubts and misconceptions and would emphasise the need to complete the entire course of antibiotics. Pharmacists expressed that patients and caregivers were usually trusting and accepting of the medical team’s decision to prescribe the antibiotics, as well as the pharmacists’ explanation.“So, we just tell them the general condition may have a lot of different [coughing] kinds of bugs. So, each antibiotic targets a different kind, so that’s why they need…more than one type. But they will generally accept the…our justification and counselling.”“[During] dispensing, it will usually be the oral antibiotic, so just telling them how to use it. Or sometimes they will ask you simple questions like whether this antibiotic is considered strong, will it have a lot side effects, so it’s just to kind of educate them on what is it, and why is it important for you to take [that] you need to finish the course.”At the organisational level, pharmacists discussed various facilitators and barriers to their contributions to antimicrobial stewardship in their daily clinical work.The lack of manpower, time constraints, and competing priorities were the main barriers to antimicrobial stewardship. With a heavy workload in a fast-paced working environment, non-ASP pharmacists were less likely to negotiate with physicians on the appropriate antibiotic therapy.“Sometimes it’s just in our culture because everything is so fast and you know [name of institution] is very busy. So we don’t have the time to just stop and listen [to the physicians’ rationales].”Furthermore, as antimicrobial stewardship was not a key performance indicator for non-ASP pharmacists, it was low in priority.“For ID [Infectious Diseases department],of course that would be their KPIs [Key Performance Indicators]. But let’s say if you have a lot of things on mind, … your main job is just to, like for pharmacist, would just be dispensing, reviewing orders. How much details can you go into? Dwelling into drug resistance that would be my last line.”In-house antibiotic guidelines were perceived by most participants as being useful in supporting their interventions and antibiotic recommendations. Some pharmacists felt that physicians tended to be more receptive when their recommendations were based on guidelines, as they were evidence-based and approved by infectious disease physicians.“Easier to back up actually. Like you can tell them [physicians] as for [name of hospital] guidelines recommend to use this antibiotics, if you have this, this, this… They [are] a bit more receptive cause it’s guided by our institution.”However, physicians’ compliance with the hospital guidelines varied between clinical departments.“There is varying compliance with the guidelines. Also because the different departments deal with very different kind of patients. So that, the practice is still quite mixed.”Antibiotic computerised decision support systems (CDSSs) were available in two study institutions (TTSH and SGH). In general, hospital pharmacists who had the experience of using an antibiotic CDSS felt that whilst CDSS could guide antibiotic prescribing, the algorithms were non-exhaustive and might not address all patient situations, such as patients with multiple antibiotic allergies. Furthermore, one participant shared that human judgment was still required for antibiotic prescribing decisions.“Even though the ARUS-C  says or whatever guideline ARUS-C sets, it’s not like we have to follow it 100% so… I mean it’s useful for juniors or someone who’s not familiar. But if [for] someone that was experienced, it’s good to rely on the critical thinking rather than just follow the guidelines.”At the community level, hospital pharmacists perceived that the general public had poor awareness of AMR and knowledge on antibiotic use.Pharmacists mentioned the need to instil public awareness of AMR, which might help improve patients’ compliance with antibiotics. Educating and enhancing the public’s understanding of AMR and the use of antibiotics would reduce the pressure on the medical team to prescribe antibiotics due to patient demands.“I think layman education… very important. If there is [knowledge] there is less, less request then less pressure to prescribe.”“[For] patients, will be [public] education, the more they know about their condition, the more they understand, and maybe they won’t feel that I must have antibiotics.”Pharmacists cited instances when patients expected antibiotics even though their medical conditions did not require them, and how their demands resulted in unnecessary antibiotics prescribed. Moreover, hospital pharmacists were concerned about patients’ compliance with antibiotics due to their lack of awareness and threat of AMR.“I mean we have patients who come in for minor surgery and … they expect antibiotic and they make a fuss at the counter and ask for antibiotic and because there’s a fuss, I have to get the doctor, okay can you just give some antibiotic.”“So some of them, I have patients before who ask for standby antibiotics on discharge to bring home, because they, and I don’t know whether they know how to use it appropriately but sometimes the team, they cannot turn the patient down also.”Despite the challenges faced, non-ASP hospital pharmacists continued to recognise the important role they play in antimicrobial stewardship and had suggested leveraging their ongoing roles in medication reviews to opportunistically ensure the optimisation of antibiotics.“I think we do play a role in optimising the dosage of the antibiotic. I know we don’t get to tell them “you know you shouldn’t use the antibiotic”, but once the antibiotic is started, we can be the one that optimise the dose to make sure that when we are giving a therapeutic dose, treat it well, [not] to develop resistance, in that sense. [So yes], I think we can play a part in educating the doctors so when we call to intervene [we can make them aware].”Furthermore, the pharmacists advocated the use of institutional guidelines to facilitate their antimicrobial stewardship efforts.“[With] institutional guidelines in place. It is easier for people to follow. Especially good educational tools for junior doctors on the ground, also easier for pharmacists to use it as a back-up when they are discussing with the doctors.”Finally, non-ASP pharmacists suggested more on-the-job training to better equip them to enhance their contributions to antimicrobial stewardship.“But what we can do as of now I think is quite limited… You [will] need probably more training as well to know. When you can de-escalate because sometimes you are not [as] clinically, that well trained like doctors. We don’t have [the] physical exam skills, we don’t know how to see if the patient is toxic, maybe our choice or our decision to escalate or de-escalate may not be appropriate a lot of times. So maybe we need more training to see, see the appropriateness in escalation.”Our study provided deeper insights into the challenges faced by non-ASP hospital pharmacists in antimicrobial stewardship and identified facilitators and barriers to their greater involvement in antimicrobial stewardship in the three largest acute-care hospitals in Singapore. Similar to many developed countries worldwide, these hospitals have established ASP teams with dedicated ASP pharmacists for antimicrobial stewardship . HoweverAt the intrapersonal level, hospital pharmacists identified themselves as reviewers for drug safety before dispensing antibiotics, confining themselves to a restricted advisory role to the prescribing physician. This observation corroborated findings from other studies, which similarly identified that pharmacists were viewed as drug advisors rather than integral contributors to antibiotic decision-making, and their interventions on antibiotic prescribing often went unnoticed . As suchPharmacist-led rounds have been shown to improve patient care and also provide the mechanism for hospital pharmacists to be formally involved in antibiotic decisions. A study in Australia  reported a significant decrease in the use of restricted antibiotics and an increase in intravenous-to-oral conversion of antibiotics; the medical team’s compliance to the pharmacists’ interventions was as high as 81.5% . A systeThe involvement of hospital pharmacists in antimicrobial stewardship was observed to be limited by knowledge deficiencies in clinical medicine and microbiology. Studies have suggested the use of advanced electronic medical records and mobile applications to help pharmacists keep up-to-date with hospital-specific antibiograms and guidelines, and the latest clinical knowledge ,32,33. FAt the interpersonal level, despite frequent communications with physicians, pharmacists felt that the physicians did not trust their antibiotic recommendations. Strong rapport and collaboration between physicians and pharmacists are well recognised as important factors for ensuring the success of ASPs ,34. ThroTo ensure patients’ compliance with dispensed antibiotics, hospital pharmacists educate patients and caregivers on the purpose and appropriate use of antibiotics. In so doing, hospital pharmacists have subconsciously served as antibiotic stewards, increasing patients’ adherence to antibiotic use. A previous trial in Australia reported that involving community pharmacists in verbal patient education helped to improve antibiotic knowledge significantly and provided a personal touch for patients to understand the significance of antimicrobial resistance . This coAt the organisational level, hospital pharmacists found hospital-specific antibiotic guidelines to be useful but had mixed reactions to antibiotic CDSSs. That was despite the reported benefits of antibiotic CDSSs on optimising antibiotic utilisation and resulting in better clinical outcomes for patients ,41. HoweIn the community, hospital pharmacists can play an active role in public education on AMR and the appropriate use of antibiotics, as well as professional education of community/retail pharmacists on the local epidemiology and antibiotic susceptibility patterns. Some studies suggested the lack of comprehensive knowledge among community pharmacists on antimicrobial use and AMR . TherefoOur study is limited to the perspective of hospital pharmacists in Singapore, a developed country with well-established ASPs in acute hospitals . NonetheOur findings reflected several significant themes on hospital pharmacists’ perspectives on their roles in antimicrobial stewardship. Barriers included low self-efficacy due to the perceived lack of clinical knowledge and experience, lack of recognition as joint antibiotic decision-makers, time constraints, and competing work demands. Facilitators included the natural inclination towards checking for medication safety and educating patients and caregivers on antibiotic use. Formalising the role of hospital pharmacists as antibiotic stewards and providing them with the required resources and training will capitalise on their untapped potential to enhance ASPs and further optimise antibiotic use in hospitals.


These aspects led to rigorous research for suitable raw materials. Taking into account that these raw materials must have a sustainable character and also a low impact on environmental pollution, the replacement of the conventional components of concrete by residual waste can lead to these targets. This paper’s aim is to analyze the density, compressive strength and the thermal conductivity of nine concrete compositions with various rates of waste: four mixes with 10%, 20%, 40% and 60% chopped PET bottles aggregates and 10% fly ash as cement partial substitution; a mix with 60% waste polystyrene of 4–8 mm and 10% fly ash; a mix with 20% waste polystyrene of 4–8 mm, 10% waste polystyrene of 0–4 mm and 10% fly ash; a mix with 50% waste polystyrene of 4–8 mm, 20% waste polystyrene of 0–4 mm and 20% fly ash two mixes with 10% fly ash and 10% and 40% waste sawdust, respectively. Using 60% PET aggregates, 60% polystyrene granules of 4–8 mm, or 20% polystyrene of 0–4 mm together with 50% polystyrene of 4–8 mm led to the obtainment of lightweight concrete, with a density lower than 2000 kg/m3. These mixes also registered the best results from a thermal conductivity point of view, after the concrete mix with 40% saw dust. Regarding compressive strength, the mix with 10% PET obtained a result very close to the reference mix, while those with 20% PET, 40% PET, 30% polystyrene, and 10% saw dust, respectively, registered values between 22 MPa and 25 MPa, values appropriate for structural uses.The continuous growth of the concrete industry requires an increased quantity of cement and natural aggregates year after year, and it is responsible for a major part of the global CO Energy consumption in the world is increasing and, therefore, a need for taking into consideration the ongoing energy crisis and the impact it has on the environment is present. In terms of energy demand, the built environment is a net consumer of energy, demanding over 36% of the global energy, and upwards to 50% of raw materials worldwide. In terms of the environmental impact, buildings are responsible for over 39% of the global greenhouse gas emissions .2 and 1 ton of concrete produces 0.108 tons CO2. According to experts, the concrete industry is responsible for 7 to 9% of the global greenhouse gas emissions [It is estimated that: 1 ton of Portland cement produces 0.96 tons of COmissions .The use of wastes as an aggregate substitution in construction materials represents a great alternative, especially in cement based concretes, due to large scale use in the construction industry. By using waste materials, such as chopped PET bottles, granular polystyrene, and waste wood, as aggregates in the concrete mixture, an ecological and performant concrete can be obtained, such as lightweight concrete, that can be used to reduce the weight of buildings. Another significant advantage of this type of concrete mixture is the valorification of waste materials that can produce a negative impact on the environment.2 emissions, by decreasing the produced quantity of cement, and by natural aggregates’ use in a concrete mix.The purpose of this paper is to investigate the density, compressive strength and thermal conductivity of various concrete mixes using waste as aggregates and cement substitutions. The study implied the development of ten concrete mixes, which included a reference concrete mix made with conventional components only (river aggregates and cement), and nine concrete compositions with waste materials as aggregates and cement partial replacements, as follows: four mixes with 10%, 20%, 40% and 60% chopped PET bottles aggregates and 10% fly ash as cement partial substitution; a mix with 60% waste polystyrene of 4–8 mm and 10% fly ash; a mix with 20% waste polystyrene of 4–8 mm, 10% waste polystyrene of 0–4 mm and 10% fly ash; a mix with 50% waste polystyrene of 4–8 mm, 20% waste polystyrene of 0–4 mm and 20% fly ash two mixes with 10% fly ash and 10% and 40% waste sawdust, respectively. Using the waste materials mentioned can contribute significantly to reducing waste quantity and COIf waste, such as chopped PET, granular polystyrene, and waste sawdust, are to be used as aggregates in the composition of concrete, then the pollution and impact of the construction sector on the environment will decrease, these facts represent a great advantage both in terms of recycling and reducing the consumption of natural ingredients, such as sand.There are various recent studies on the use of waste chopped polyethylene terephthalate, granular polystyrene, and waste wood (sawdust) in the composition of the concrete mixture by replacing natural aggregates ,9,10,11.Furthermore, by investigating the mechanical properties of the concrete with waste chopped PET bottles, granular polystyrene, and waste wood as a substitution in the concrete mix, researchers obtained results that highlight the fact that the mechanical properties of fresh and hardened concrete are being influenced by the ratio of the replaced material in the concrete mix ,19,20,21In terms of research trends, scientist have analyzed the incorporation of various materials into concrete in order to reduce the required raw materials, ranging from crushed recovered concrete and ceramics, vegetal byproducts and even plastics. Some examples of such studies are presented in The use of PET and polystyrene in concrete mixtures, both in structural or lightweight concrete, was analyzed in a number of studies with the aim to reduce the waste in the world and reduce the quantity of required raw materials. The analyzed properties of these concretes include—but are not limited to—compressive strength, density, tensile strength, elasticity modulus, flexural strength, durability, thermal properties and fire resistance.In their study on concrete with polystyrene with a ratio ranging from 20% to 80% of the total volume and a resin mixture of 0.5%, 1%, and 1.5% of the total weight, Kaya and Kar concluded that, as the added components percentage increase, the porosity of the concrete increases and the mechanical properties, such as density, tensile strength, compressive strength, and thermal conductivity, decrease .In their research, Saikia and Brito performed an experimental investigation on specimens for compressive strength, split tensile strength, and flexural strength, observing that an increase in the concentration of the PET ratio as aggregate in the mixture leads to a decrease in the compressive strength, split tensile strength and flexural strength of the concrete .The study published by Rahmani et al. investigated the mechanical properties of cubic and cylindrical concrete specimens with 5% to 15% substitution of sand with particles of PET and different water to cement ratios. The experimental study revealed that the compressive and flexural strength initially tend to increase, however, they tend to decrease after a period of time. Moreover, the experiments highlighted that the samples containing PET particles have a lower density, splitting tensile strength, modulus of elasticity, and workability .Jahidul et al. carried out an experimental investigation on the properties of PET aggregate concrete by replacing between 0 and 50% of the volume of coarse aggregates, observing that this type of concrete provided better workability than regular concrete while using a similar w/c ratio, the density of the PET concrete was reduced by 4 to 10%, thus reducing the self-weight of the structural element. The optimal substitution ratio was 20%, this percentage ensuring comparable compressive strength with natural aggregate concrete .Maldonado-Bandala et al. observed similar results regarding mechanical parameters such as density and compressive strength—that these parameters decrease as the ratio of polystyrene increases—but the experiment revealed that the corrosion protection of the concrete with polystyrene is greatly superior to conventional concrete .Studies performed by Sayadi et al. revealed that adding expanded polystyrene into the concrete mixture translates to a decrease in thermal parameters such as thermal conductivity and fire resistance .Sawdust, as a byproduct of the wood industry, has been researched and implemented in various forms since the 20th century in regions such as the United State of America, Asia  and Europe (Germany and the UK). The possible applications of this material are significant, as highlighted by the fact that this material, in various forms and adaptations, has been used for building elements such as walls and floors .Sales et al. analyzed the incorporation of untreated wood shavings into concrete to obtain lightweight concrete. The study highlighted that, through the introduction of sawdust into the concrete mixture, some key parameters were improved: the thermal conductivity of the concrete was improved and the mass density was reduced. At the same time, the sawdust presented a good adherence to the concrete matrix and the structure of the mixture was homogeneous .Sofi et al. investigated the compressive strength of concrete samples with a volume of added sawdust ranging from 0% to 15% in the concrete mix at two curing periods, at 7 and 28 days. The results obtained after the curing periods show that the compressive strength is higher for concrete samples with a lower substitution percentage of sawdust .The implementation of sawdust in concrete has not reached the level of widespread adoption due to the limitations of sawdust, which has low compressive strength. At the same time, the advantages of concrete with sawdust  justify the increasing interest in this type of material.Fly ash is a byproduct of burning coal in power plants in the form of ultrafine solid residue. In numerous developed and developing countries, such as US, China and India, where coal is used, it is one of the largest solid wastes. Fly ash has been implemented as an additive in concrete since the mid-20th century as a replacement for some raw materials such as cement or as a mixture with a clinker .The analysis performed by multiple researchers highlights the increase in interest towards ecological concrete and its potential to reduce the carbon footprint buildings impose on the environment. Even though some mechanical parameters are not as high with the substitution of natural aggregates, these types of walls can be applied in nonstructural elements.The cement used in the concrete mixture is Portland cement type CEM II 45.2 R produced in Romania following the EN 197-1 standard, this fact is evidenced both from the producer’s multiple declarations of conformity, performance certificates and through independent tests conducted on a cement sample. The cement has the following components: Portland clinker maximum dosage 94%, limestone 6–20%, and auxiliary components 0–5% ,36.3, specific surface area of 520 m2/kg, particle size ranging from 0.01 to 400 µm and, as main chemical components, O2 (43.3%), Si (30.8%), Al (19.2%) and Fe (3.05%) [The fly ash used as a replacement for the cement, which is released with the exhaust fuel gases, presented in  (3.05%) ,38.The aggregates used in the composition of the concrete can be classified into:3, and absorption of 1%, and two sorts of river stone (sort I 4–8 mm and sort II 8-16 mm) with a specific gravity of 2.62, bulk density 1400 kg/m3, and absorption of 0.9%, presented in Natural aggregates such as sand with a specific gravity of 2.68, bulk density 1700 kg/m3 [Chopped PET from bottles (having dimensions between 0–4 mm), resulting from cutting discarded polyethylene terephthalate (PET) bottles. After the cutting of the material it was sieved in order to obtain the desired particle dimensions. This waste material presents high stability and nonreactivity with substances. The unit weight of the chopped PET was determined experimentally and has a value of 433 kg/m3 ;Granular polystyrene (with dimensions 0–4 mm and 4–8 mm), which can be reused in the shape of granules, resulting from shredding, cutting or thermal treatment;3 [Waste wood/sawdust (with dimensions 0–4 mm), is a byproduct resulting from the wood industry. The collected sawdust was air dried and afterwards sieved, in order to imitate the size of the natural aggregates. Sawdust in terms of chemical composition is comprised of carbon (60.8%), hydrogen (5.2%), oxygen (33.8%), and nitrogen (0.9%). The primary components of dry wood are cellulose, lignin, hemicelluloses, and small amounts (5–10%) of extraneous materials. The unit weight of the sawdust was determined experimentally and has a value of 168 kg/m3 ,40.Waste aggregates, evidenced by 3, river gravel with 4–8 mm in diameter 384 kg/m3, river gravel with 8-16 mm in diameter 559 kg/m3, cement 360 kg/m3, water 180 l/m3 and a 1% superplasticizer additive of the cement mass.The concrete mixture without any substitutions was made according to the following recipe: sand 803 kg/mIn order to conduct the experiments and determine the mechanical parameters and the advantages and disadvantages of the partial substitution of the natural aggregate with either chopped PET, granular polystyrene, or waste wood (sawdust), nine types of different concrete mixtures were considered, with the mixing proportions and the quantities of the used materials presented in The concrete mixture realization process involved adding the materials and water in the two-blade mixer, the mixing process was finished after 30–40 min.Samples S1 to S4 also contain fly ash, which replaced 10% of the cement, and from 10% to 60% chopped PET replacing the same mass volume of cement.In the concrete mix using waste granular polystyrene, three samples in which 10% of cement was replaced with fly ash, and the substitution of natural aggregates used were replaced by 60% of the sort I aggregate mass 4–8 mm were replaced with granular polystyrene 4–8 mm, resulting the concrete sample notated S5.Following this, the concrete mixture was changed once again by replacing two natural aggregates in order to create sample S6, as follows: 90% of the sand was used, the remaining 10% being substituted by 10% of the sand mass with granular polystyrene 0-4 mm in volume, and, as a secondary substitution, only 80% of the original sort I, with a size of the granules of 4–8 mm, 20% from the sort I mass was replaced with granular polystyrene 4–8 mm in volume and a further substitution of 10% of the cement was made with fly ash.For the concrete sample S7, another modification in the concrete mixture was made, in which 20% of the cement was replaced with fly ash and two more natural aggregates were partially replaced with granular polystyrene, replacing 20% of the sand mass with granular polystyrene 0–4 mm in volume and 50% of the sort I mass 4–8 mm was replaced by 50% granular polystyrene 4–8 mm in volume.The last two samples, S8 and S9, were realized by further modifying the mixture: 10% of the cement was replaced with fly ash in both concrete samples and a percentage of the sand was replaced with its corresponding volume of sawdust. In the case of sample S8 only 10% of the sand was replaced and in the case of sample S9, 40% of the sand mass was replaced with the same volume of sawdust.Following the mixing process, the concrete mixtures were poured into cubic shapes with the side length of 150 mm, The concrete samples in cubic shapes were made for the experiment of the compressive strength and density investigation; the rectangular prismatic concrete samples (plate concrete samples) were made for the experiment of the heat transfer coefficient investigation.After the preparation, the concrete samples were left for curing for 28 days in laboratory conditions at a controlled temperature.Experimental investigation on the density of the concrete samples was carried out according to the EN12390-7 standard  on tree The mass of the specimens was measured after the curing period, according to the EN12390-7 standard 35.The density can be calculated with the formula:The preparing and keeping of the concrete samples were performed respecting the indications of EN 12390-2 standard . FollowiThe compressive strength was determined according to EN 12390-3 standard  on tree 2·s constant at the beginning is applied on the area of the concrete sample without shock, after applying the first load force to the specimen, the load was increased continuously at a constant rate ±10% until the specimen reached the maximum load failure.In the testing procedure presented in The experimental determination of the concrete density is presented in 2·s constant force is applied at the beginning on the surface area of the concrete sample without shock. After applying the first load force to the specimen, the load was increased continuously at a constant rate of ±10% until the specimen reached the maximum load failure. The uncertainty of the obtained results was calculated for the compressive strength on the studied specimens and it resulted in a minimum of 0.3% and a maximum value of 1.35%.In the testing procedure presented in The variation of compressive strength presented in In A first analysis was performed by comparing the density versus compressive strength of concretes in which one natural aggregate was replaced with the same waste used in the concrete mixture, in this case, the natural aggregate sand was substituted with waste chopped PET.By comparing the obtained results The second analysis was carried out on the concrete samples, substituting the natural aggregates with granular polystyrene. The results presented in A final analysis on the mechanical properties for the concrete with different waste substitution at the same percentage as the waste replacement is presented in Results from The thermal properties were determined using an experimental device, developed at IUSTI Laboratory, which is based on the hot plane method with temperature measurements on both sides of the sample. The characterization is carried out at room temperature. A scheme of the experimental device is shown in The concrete sample is heated in the front face by a heating sole (hot plane)  consistiTo achieve these measurements, the concrete sample was first positioned in the thermal device , and thed = e2/ata = k/ρCpPVC, corresponding to the ratio of the samples upon the sample’s holder (PVC) effusivities.x = b/bA transient thermal model  was used to calculate the theoretical thermogram of the rear face, by convolution of the thermogram of the front face of the sample. This theoretical thermogram is a function of the following parameters:The effusivity is given by:These parameters were then identified by a least squares method, minimizing the gap between the theoretical and experimental thermograms, over range duration around the diffusive time.The thermal diffusivity a;The thermal effusivity b;The thermal conductivity The thermal capacity The appropriate following parameters are then extracted.The error of the thermocouples measurements (standard deviation: 0.005°C);p, i.e.,: error on the thickness e: 1%; error on the PVC effusivity bPVC: 10% and density error ρ: 4%.The error due to the considered known parameters for determining a, b, k, ρ, and CThe uncertainties calculation were carried out taking into account:PVC is around (518 ± 10%) Jm−2K−1s−0.5, which corresponds to values given by the manufacturer.First, a calibration was achieved to determine the sample holder (PVC) thermal diffusivity and effusivity. It was found that bFor each sample, the same process was applied in order to determine the various thermal parameters. In From the thermal conductivity measurements, one can observe that the values of thermal conductivity are lower than the thermal conductivity of the standard concrete (S0). This result is consistent with the results found in the literature, since the thermal conductivity of the added waste is below the concrete one. Furthermore, reducing the thermal conductivity of concrete would provide better insulation for the building.Following the measurements, In order to illustrate the effect of the addition of waste on the global behavior of the concrete, another figure was created, The first one corresponds to concrete formed by the addition of a high concentration of waste, typically higher or equal to 50% ; the thermal conductivity was approximately reduced by almost 25%, while the compressive strength was reduced by 45–60%. One can consider that this zone is rather characterized by a constant thermal conductivity.The second zone gathers a moderate concentration of waste , showing that the compressive strength is rather constant (a reduction of around 25%) whereas the thermal conductivity ratio is reduced by between approximately 5 and 20%. This zone will be considered as a zone with a constant compressive strength.Finally, the third zone, corresponding to the low concentration of waste, behaves mechanically as the standard concrete, the only noticeable difference being the lower thermal conductivity.From These results fall into accordance with the results found in the literature and infer the fact that, depending on the type of application, the appropriate concentration of waste aggregate can provide significant advantages in comparison to regular concrete. For example, through adding a low concentration of waste materials, the mechanical properties of the newly formed concrete are similar to those of the regular concrete, being good for the structural elements of buildings or, through adding an increased quantity of waste materials, the mixture provides a lower material conductivity, helping insulate the building and preventing heat loss ,27,28,29The experimental study investigated the use of waste materials as a partial substitution of aggregates and cement in manufacturing concrete, and analyzed the mechanical properties via the compressive strength, density variations, and the thermal properties via the thermal conductivity parameter.Three zones of behaviors were highlighted, the first one, corresponding to high waste concentration, leads approximately to a constant reduction in the thermal conductivity. The second, characterized by moderate waste concentration, behaves as a constant compressive strength. In addition, finally, the third one, defined by very low waste concentration, induces only a very small reduction of the thermal conductivity with the compressive strength approximately the same as standard concrete.By analyzing the compressive strength of the concrete with waste aggregates substitution, the study highlighted that the concrete can be used as a structural material such as self-sustained walls for low waste concentration, the differences in mechanical properties being negligible. On the other hand, high concentrations of waste aggregate in the concrete lead to a decrease in thermal conductivity, providing good solution for nonstructural walls with an increased insulation capacity in comparison to regular concrete walls, preventing heat loss.One of the most important key factors is that, through reusing the waste and not using conventional aggregates, the carbon footprint of the building is reduced, this being a significant factor in the development of the construction sector in the future.The studies revealed that a 10% replacement of the cement with fly ash and a 10% replacement of the sand with chopped PET had minimal impact on the properties of concrete, but on an environmental scale, if concrete were to have a portion of the natural aggregates replaced, this would have a significant impact both in terms of the reduction in necessary materials and in terms of pollution, as the waste materials would be given a new purpose.


Silane coupling agent (SCA), a kind of organic solvent, was introduced to improve the performance of coral coarse aggregates and enhance the interfacial adhesion between the inorganic coral aggregate and the cement paste of coral concrete. The crushing indicator and water absorption of the coral aggregates over various dipping times were measured, and the slump, interface microhardness, and compressive strength of coral concrete tested. The microscopic appearances of the coral concrete before and after modification were analyzed based on SEM images. The experimental results indicate that SCA can effectively reduce the crushing indicator and water absorption of coral coarse aggregates, and the modification performance becomes better over time. SCA facilitates the generation of chemical forces between the coral aggregates and cement mortars, improves adhesion between the aggregates and mortars, augments the microhardness of the interface, and increases the compressive strength. According to the microscopic appearance of the treated and untreated coral aggregate interfaces, the aggregates and the mortars are in closer combination after modification.  As countries attach greater importance to their maritime rights and interests, they have enhanced the development and construction of marine resources and have vigorously promoted reef engineering. It is impractical to use conventional building materials  for reef construction. This is especially true for distant-water reef construction, as it takes a considerably long time and huge costs to complete the complex transport of construction aggregate from inland to the distant water. Besides, construction aggregate requires a large space for storage. Moreover, it has been found that construction aggregate has poor environmental suitability. Obtaining materials from local sources on a reef is expected to significantly lower the level of difficulty and reduce the cost of reef construction. For instance, natural coral can be used as aggregate, a component of concrete. During World War II, coral was used as concrete aggregate in construction ,2. ThereAt present, manufacturers generally increase the strength of coral concrete with gelling materials, admixtures, and additives, specifically by increasing the cement content or mark, adding high-activity mineral admixtures, or reducing the water–cement ratio with a high dose of water-reducing agent. However, there is limited research on achieving a higher coral concrete strength by improving coral aggregate performance through surface modification. Further, there are no reports on coral aggregate surface modification with silane coupling agent (SCA).3, as shown in SCA is a type of organosilicon containing two kinds of chemical groups in its molecules. It is represented by the general formula YSiX3 can react with the reactive groups chemically combined with both organic materials  and inorganic materials  at the same time, and is often used for surface treatment of inorganic and organic material interfaces. SCA can be utilized to realize chemical bonding between inorganic and organic material interfaces, which significantly improves the strength and aging-resistant performance of composite material interfaces and thereby raises the physical and mechanical performance and durability of the composite materials to a considerably higher level [Because of its special structure, YSiXer level .SCA is usually applied to concrete preparation as an organic aggregate modifier to ensure tight bonding between organic aggregates and inorganic gelling materials, e.g., by modifying the rubber particles in rubber concrete. Dong et al.  treated It is effective to perform surface treatment of rubber with SCA to enhance the adhesion between rubber aggregate and mortar and improve mechanical performance of rubber concrete ,15,16. SSCAs build the “bridge” connecting organic and inorganic materials. They are often applied to polymer concrete modification to improve the adhesion between organic adhesive and inorganic aggregate in polymer concrete, such as resin concrete and pitch concrete. Mani  used polSCAs can also be used to enhance the adhesion between two kinds of inorganic materials. Many researchers have employed SCAs to combine different inorganic materials  and obtained desirable outcomes. Luo et al.  applied From the above-mentioned studies, it can be seen that SCAs are effective in the adhesion of inorganic materials. Coral aggregate modification with SCA, theoretically, can improve the strength of coral concrete. In addition, despite some studies on inorganic material modification, there is a lack of analysis on the modification of coral aggregates in coral concrete. Few studies have addressed coral concrete surface treated with the organic materials. In this paper, an organic surfactant, SCA, was used for surface modification by soaking coral aggregates. Then, a comparison was made between the coral aggregates before and after modification to analyze the changes in coral aggregate and concrete performance. According to relevant standards, the water absorption and crushing indicator of coral coarse aggregates were tested. An assessment of the slump, compressive strength, and flexural strength of coral concrete was conducted. The microhardness testing system was adopted to test the hardness of the interface between aggregate and mortar. At the same time, a characteristic and microscopic analysis of the interface was performed through SEM. Combining the experimental phenomena, this paper probed into the effect of SCA on coral aggregates from the physical and chemical perspectives.Ordinary Portland cement (P.O 42.5R), in compliance with China National Standards GB 175-2007, was used . This waThe coral aggregates in this study were collected from an oceanic island in China. The coral coarse aggregates were screened with an electric sieve shaker and were in the range from 4.75 mm to 19 mm. In this study, fine coral aggregates (particle size ≤ 2.36 mm) after screening were used as samples, as shown in 2-CH(O)CH2-O(CH2)3Si(OCH3)3, see The SCA KH-560 :The arithmetic mean value of three measured values was adopted as the test result.The coral aggregates are efficient in water absorption and thus have a strong influence on the flowability and workability of concrete. The saturated surface dry water absorption of coarse coral aggregates was tested according to the GB/T 14685-2011 standard . An apprmW indicates the water absorption of the coarse coral aggregate, %; G0 represents the sample mass in the saturated surface dry state, g; and G1 expresses the dried sample mass, g.The water absorption of the samples can be calculated according to Equation (2) (accurate to 0.1%):The arithmetic mean value of three measured values was adopted as the test result.The coral concrete slump test was performed according to GB/T 50080-2002 . The welThe hardness of the interface between the aggregate and cement stone is a direct reflection of the combination of the aggregate and cement stone. An HV-1000 semi-automatic microhardness testing system  was employed to test the hardness of the interface between the coral aggregate and cement stone before and after modification. The load value selected in the experiment was 50 g, and the load time was 15 s.The sample was collected from the interface between the coral aggregate and cement stone in the sample concrete block after 28 days of standard curing; it was then soaked in absolute ethanol for 1 day to prevent hydration. It was cut into a 40 mm × 40 mm × 10 mm sample and dried to a constant weight; then, the top and bottom surfaces were polished. The contact surface between the aggregate and cement stone was set as the zero-point to measure the internal aggregate and the basal body of the cement stone every 20 μm (220 μm in length). The measurement of each test point was repeated 3–5 times and the mean value of the measured values was considered the microhardness value of the test point.The compressive strength test was conducted with a microcomputer-controlled electro-hydraulic servo universal testing machine according to GB/T 50081-2002 . A TYEH-In the property measurement, 3 samples were selected for testing each time. When the 3 data points differed by no more than 15%, the average value was taken. When 2 of the 3 data differed by more than 15%, the data were considered invalid, and the sample was reprocessed and tested.A scanning electron microscope was employed to observe the microscopic structures of the coral aggregates and coral concrete before and after modification, especially the interface between the aggregates and mortar before and after modification.In concrete application, SCA is mainly used for modification by means of surface pretreatment or directly mixing the agents with concrete. Surface pretreatment means using SCA to modify the aggregate surface, and the direct method indicates mixing SCA directly into resins or other organic gelling materials and aggregate. The surface pretreatment method was adopted in this study to perform surface treatment and modification of coral aggregates. First, the coral coarse aggregates were impregnated for some time, and then they were heated and dried until solidification.2O:C2H5OH = 5:45:50 and with the hydrolysis time of 20 min [2O:C2H5OH = 5:45:50 for 20 min.To facilitate dispersion of SCA on the coral aggregate surface, the silane coupling agent should be hydrolyzed in advance in a solvent prepared with water and alcohol, such as ethanol, isopropanol, and so on. Many researchers have engaged in studies on hydrolysis techniques. Liang used the silane coupling agent KH-550 for aggregate surface modification and proposed the corresponding hydrolysis technique in the hydrolysis proportion of KH-550:Hf 20 min . Based o2O and C2H5OH were mixed and stirred evenly in the proportion of 45:50. Then, an appropriate amount of SCA KH-560 equal to roughly 5% of the total volume was added to the solution. The mixture was hydrolyzed at room temperature for 20 min. After hydrolysis, the prepared coral coarse aggregates were added and soaked in the modification solution for 1, 5, 12, and 24 h respectively. During the process, no aggregates should be stacked together, and the top of the aggregates should be 10 mm away from the surface of the solution. The impregnated coral coarse aggregates were heated and dried for 4 h.First, HThe saturated surface dry water absorption and crushing indicator of the coral coarse aggregates before and after being soaked with SCA were determined to explore the agent’s impacts on the water absorption and crushing indicator of the coral coarse aggregates at different time points, as shown in It can be seen from After heating and drying, part of the hydrogen bonds forms covalent bonds through dehydration and generates a firm mesh membrane to block the pores in the coral aggregates. The pore size distribution range is about 10–100 μm. In the process, the pores in the coral aggregates are bonded and closed. As a result, the aggregate strength was increased. However, this is only applicable to the tiny pores, but not the larger ones. Hence, only a limited improvement in the strength will be made. Coral coarse aggregates have a lower water absorption because SCA has hydrolyzable alkoxyl on one end, which can cover the coral aggregate surface by physical adsorption or form chemical bonds on the coral aggregate surface so that the organic groups on the other end of SCA can be exposed to the cement paste , as showThe organic groups enlarge the contact angle of the coral aggregate surface and impair the hydrophobicity of the coral aggregates. Meanwhile, these organic groups, to a certain degree, can affect water absorption of the coral aggregates. However, because SCA does not completely block the pores of the coral aggregates but improves their hydrophilic performance, the water absorption only drops slightly ,31.As shown in 1, A2, A3, and A4, respectively.Under the same mix proportion, the performance of common concrete, unmodified coral concrete, and coral concrete under different modification conditions was studied. See A slump test of the concrete mixed with the coral aggregates before and after being soaked in SCA solution was carried out to analyze the impacts of SCA and the soaking time on the slump condition of the coral aggregate concrete, as shown in It can be seen from According to The cement mortars for placement contain many hydroxyl groups that may form hydrogen bonds with the free silanol groups and then form chemical bonds through dehydration of the hydrogen bonds as the cement paste is hydrated and dried continuously, as shown in With the chemical bonds, the coarse coral aggregates and the cement paste can be closely bound together. In addition to the hydrophilic interaction with these inorganic groups, SCA is also likely to bring about polymerization of organic groups. After superimposed polymerization of organic groups, SCA forms chemical bonds with the hydroxyl groups in the cement paste, as shown in The concrete cube mixed with the coral aggregates before and after being soaked in SCA solution was tested to probe into the impacts of SCA and soaking time on the compressive strength of coral concrete. The comparison with ordinary concrete was also made, as shown in It can be observed that the modified coral concrete outperforms that without modification in terms of compressive strength. It can be concluded that SCA can significantly improve the compressive strength of coral concrete. As the time of modification continues, the compressive strength of the coral concrete gradually increases. After being soaked for 24 h, the compressive strength of the concrete containing coral aggregates reaches its peak, i.e., 51.1 MPa, 32.04% higher than that without modification, a value similar to that of ordinary concrete. There are two reasons for the improvement in the compressive strength of the modified coral aggregates with the SCA. First, SCA increased the strength of the interface between the coral aggregates and cement stone. Second, it enhanced the coral aggregate strength. The interface between the aggregates and cement stone is the weakest part of the concrete. Under external forces, the interface is most likely to be damaged and have crevices, which will further cause damage to other weak parts in the concrete and result in larger cracks or penetrating fissures. Therefore, the interface strength has a considerable influence on the compressive strength of the concrete . The intThe micro-structural cement paste and cement interface of the coral concrete before and after modification are shown in Due to the large porosity of coral aggregate, the mechanical properties of coral concrete are relatively low. The article deals with the research ideas of surface coating treatment of metal materials and uses surface treatment agent (KH-560) to surface treatment of coral aggregate inorganic materials to enhance the performance of coral aggregate.In this paper, coral coarse aggregates and coral concrete were strengthened by soaking the aggregates in SCA solution. SCA was effective in improving the coral coarse aggregate strength and reducing the crushing indicator of the coral aggregates. Meanwhile, through surface absorption and chemical bonding, plenty of hydrophobic groups of SCA were distributed on the coral aggregate surface, increasing the contact angle on the coral aggregate surface, impairing the hydrophilic performance of the coral aggregates, and partly reducing its water absorption. The modified coral aggregates have lower water absorption, leading to an increase in water content for cement hydration and a higher slump of the coral concrete. SCA, based on chemical bonding, can effectively and closely combine the coral aggregates and cement paste, increase the microhardness of the aggregate surface, and improve the compressive strength of the coral concrete. Specifically, after the aggregates are soaked in the agent for 24 h, the compressive strength of the modified coral concrete increases by 35%. From the microscopic appearance of the interface between mortars and aggregates of the coral concrete before and after modification, it can be seen that there are smaller differences between the adhesion of the modified aggregate interface to water and the cohesion of water, while a denser aggregate interface can be observed.Based on this research, the impact of SCA surface-modified coral aggregates on the durability as well as the dynamic mechanical properties of coral concrete can be further studied. At the same time, the improvement of SCA composition, the compounding of multiple materials, and the modification and optimization of the surface can be further studied to better the performance of the material. This result helps to enhance the mechanical properties and durability of coral concrete and promotes the application of coral concrete in engineering construction infrastructure, permanent facilities, and protective facilities.