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• This study adopted a holistic review of the recycled aggregate research. • A total of 1,639 Journal articles in RA were summarized in a text-mining method. • Mainstream research topics in RAs were analyzed. • Main gaps in existing RA research were identified. • Future RA-based research framework was proposed. Adopting a holistic three-step literature review workflow, a total of 1,639 journal articles were used in this study as the literature sample related to recycled aggregate (RA). This study summarized the existing research topics focusing on RA, gaps of current research, suggestions for promoting RA usage, and research directions for future work. A research framework was also proposed linking the existing research themes into trends in RA research. This review work serves as a foundation work to bridge the gap between scientific research and industry practice, as well as to guide the directions in RA-related academic work using an interdisciplinary approach. [ABSTRACT FROM AUTHOR]

Highlights • The study applied science mapping approach in reviewing construction safety research. • Mainstream keywords such as BIM were identified in existing literature. • Influential journals, scholars, and articles in construction safety were evaluated. • An in-depth qualitative discussion identified existing research topics and limitations. • A research framework was proposed by linking mainstream topics into future research directions. Abstract This study adopted a three-step holistic review approach consisting of bibliometric review, scientometric analysis, and in-depth discussion to gain a deeper understanding of the research development in construction safety. Focusing on a total of 513 journal articles published in Scopus , the influential journals, keywords, scholars, and articles in the domain of construction safety were analyzed. For example, simulation and fall from height related topics, although not with the highest occurrence of being studied, had the highest impact in terms of average citation received per year. It was found that research in the recent 10 years have been extended to the developing countries and regions with a more variety of research topics, such as BIM, and data mining, etc. Articles related to applying BIM in safety management received the highest average normalized citation. A follow-up qualitative discussion targeted three main objectives: summarizing mainstream research topics, identifying existing research gaps, and proposing future research directions. Five main categories were aligned, namely safety climate and safety culture, application of information technologies, worker-oriented safety, safety management program, and hazard recognition and risk assessment. Based on the above, a framework and future research directions were proposed which could serve both the academic community and practical fields in multiple themes within construction safety, including: an adaptable safety climate and safety culture model; prototypes, continuous development, and readiness of applying information technologies in safety management; subgroups factors linked to cognitive models of workers' safety perceptions and behaviors; and artificial intelligence and smart technologies into safety program management. [ABSTRACT FROM AUTHOR]

Highlights • The research adopted multivariate regression analysis for FRP-confined concrete. • A total of 23 statistical models were proposed. • The highest R2 value achieved 99%. • Mixed models could perform superior than the linear regression approach. • Effects of individual independent variables in concrete performance were evaluated. Abstract This study applied newly developed multivariate statistical models to estimating the mechanical properties of recycled aggregate concrete cylinder encased by fiber reinforced polymer (FRP). Two different types of RFPs were applied, namely flax FRP and polyester FRP. Ten independent variables were predefined including the FRP type and cylinder size. It was found that several mixed models outperformed the traditional linear regression approach, based on the accuracy and residual value distribution. Individual factor analysis indicated that the fiber thickness and layer number had more significant impacts on the strength and strain of FRP-encased concrete's transitional point, compared to their impacts at the ultimate state. [ABSTRACT FROM AUTHOR]

Abstract Off-site construction (i.e., OSC) has become an emerging research domain in the recent decade. Through a three-step holistic review approach incorporating bibliometric search, scientometric analysis, and in-depth qualitative discussion, this study contributes to the body of knowledge in OSC by critically reviewing and summarizing: 1) the latest research keywords and main research topics in OSC; 2) the performance of OSC compared to that of conventional construction approach; 3) current research gaps in integrating OSC with other emerging construction concepts; and 4) future research directions in OSC. OSC is a domain that can be extended to cross-disciplinary research from the perspectives of engineering, management, and technology. Existing research have been focusing on many research disciplines, such as structural behaviors and joint connections of prefabricated components, scheduling and planning of off-site activities, as well as performance evaluation of OSC. However, further research is needed in integrating the emerging digital construction technology, integrated project delivery method, lean construction, and issues of sustainability of OSC. There are still limited studies linking OSC to the concept of Design for Manufacturing and Assembly. Future research should also adopt a larger database and allow for comprehensive evaluation of OSC performance. Highlights • The research adopted a three-step holistic review of off-site construction. • Journal articles in OSC from recent ten years were analyzed. • Main OSC research topics were summarized. • Main gaps in existing OSC research were identified. • Research framework in OSC was proposed. [ABSTRACT FROM AUTHOR]

This research aims to develop an initiative modular unglazed Solar Thermal Facade (STF) concept initially for hot water generation to facilitate the integration of solar energy with buildings. The new STF concept is simple structure, low cost, and aesthetically appealing with easy installation but is expected to achieve the equivalent thermal efficiency as the conventional STFs. It delivered alternative design in terms of material, colour, texture, shape, size, architectural design, installation method, array connection, hypothetical system application, and solar coverage. Two common design variants i.e. (a) the STF cladding system and (b) the prefabricated STF wall system were described respectively for existing and new low-rise building typologies. Interaction of inclination, orientation, and insolation were discussed for the optimum STF position on the building. Four currently available methods for installation of such STF with buildings were summarized and three typical array connection methods were identified. The decentralized connection was recommended for different types of STF hot water systems. It is customary to design for a solar coverage of 50 to 60 percent for water heating in detached houses; in apartment buildings 30 to 40 percent are more commonly assumed. The concept design in this paper hereby illustrates the precedence for the hypothetical function by the creation of new ideas and also forms up the physical structure or operating principle for the investigations in near future. [ABSTRACT FROM AUTHOR]

The emerging sustainable development movement in the construction industry requires the recycling of waste materials to reduce the negative environmental impact of construction activities. In many countries, old concrete, a major waste stream generated from the demolition of obsolete buildings/structures, is being recycled. However, for various reasons, progress toward concrete recycling varies from country to country. This paper discusses the current status of concrete recycling in the U.S. construction industry based on results from a two-part questionnaire survey. The first part of the survey collects information on the recycling practices of surveyed concrete companies. The second part adapts questions from a study conducted in Australia and Japan to examine the awareness, benefits, difficulties, and recommended methods related to concrete recycling. The findings showed that although recycling old concrete is common in the U.S., its application is mostly limited to backfill and pavement base; using waste concrete in new concrete production is not widely applied. There are also similarities and differences in the perceptions of concrete recycling between U.S. concrete companies and their counterparts in Australia and Japan. [ABSTRACT FROM AUTHOR]

Subcontractor safety performance has become increasingly important due to the extensive use of subcontracting in construction and the elevated safety risks. Ensuring subcontractor safety has also become a major challenge of general contractors (GC). While many GCs leave the safety responsibility to individual subcontractors, others take active roles in helping them improve safety performance. To advance the understanding of how an active approach taken by the GC is received by subcontractors, a comparative study was performed to investigate subgroup workers’ perceptions of a safety program implemented by a U.S. GC among all the workers on its jobsites. In this study, a 5-dimension 28-item questionnaire was administered to 350 workers on the GC’s jobsites. The collected information was used to examine differences in workers’ perceptions between selected subgroups, i.e., the GC and its subcontractors as well as high- and low-risk building trades. This research found more positive perceptions of the safety program (i.e., the overall perception and the awareness and acceptance dimensions) among the GC’s workers than those of the subcontractors but no difference in perceptions from high- and low-risk trades. This research also identified differences in workers’ perceptions among other subgroups (e.g., based on age ranges and safety violation records) and drew insights from workers’ feedback to open-ended survey questions. The findings will help contractors better understand and manage their diverse workforce to improve jobsite safety performance. [ABSTRACT FROM AUTHOR]

Demolished concrete, as one main form of construction and demolition wastes, has been widely studied of being utilized as recycled aggregates (RAs) in new concrete production. However, existing studies of applying RAs have been limited to the mechanical and durability issues of cementitious composites containing RAs. There has not been sufficient research of adopting RAs in cementitious products to also address the environmental sustainability. On the other hand, existing research utilizing cementitious products (e.g., concrete pavement) for air purification purpose have not adequately considered RA usage. Aiming to address the two sustainable objectives (i.e., waste diversion and air purification) simultaneously in concrete mix, this research adopted a two-step approach. Firstly, we studied and identified the optimal mix design of pervious concrete containing TiO 2 -soaked recycled coarse aggregates (RCAs) in order to achieve the higher compressive strength; secondly, we investigated the photocatalytic performance of pervious concrete containing RCAs coated with TiO 2 photocatalysts. The photocatalytic performance of pervious concrete was also tested by applying a 10-min heavy rainwater wash. Experimental test results revealed that the internal voids of adhered mortar enabled RCAs to absorb more TiO 2 particles. The NO degradation rate of TiO 2 -soaked RCAs increased from 71.4% to 80.6% when RCAs' size decreased from 15-20 mm to 5–10 mm. The orthogonal experimental investigation indicated that water-to-binder ratio had the most significant effect on concrete compressive strength, followed by ratio of RCAs to binder, and replacement ratio of RCAs to natural aggregates. The optimized mix design for pervious concrete containing RCAs was identified to achieve highest strength (i.e., water-to-binder ratio at 0.35, coarse aggregate-to-binder ratio of 3 by mass, fly ash replacement rate to Portland cement at 5%, and 50% replacement ratio of RCAs to NCAs). The concentration of TiO 2 solution at 0.3% was identified as the optimal ratio to achieve the highest NO degradation rate at 70% before rainwater wash. The NO degradation rates of pervious concrete still reached nearly 50% after 10-min heavy rainwater wash, indicating that pervious concrete using RCAs coated with TiO 2 could largely maintain its photocatalytic capacity. This study addresses two main social and environmental issues in developing countries (e.g., China), namely overwhelming amount of construction & demolition wastes being generated, and air pollution. It leads to the cleaner production in concrete pavement construction by achieving the optimization between waste reuse, air purification, and engineering properties of porous concrete. • The research used recycled aggregates (RAs) in pervious concrete for air purification purpose. • RAs could absorb more nano photocatalysts. • The study identified the optimized mix design to achieve highest pervious concrete strength. • The optimal concentration of TiO 2 solution was identified at 0.3% to achieve the highest NO degradation rate at 70%. • Previous concrete showed a more durable photocatalytic performance after rain wash. [ABSTRACT FROM AUTHOR]

• Adopt a bibliometric analysis to review environmental performance of OSC. • Explore the mainstream research in OSC field. • Identify limitations of current studies in OSC practice. • Highlight future research agenda for OSC. During the recent decades, off-site construction (OSC) has gained a rapid growth worldwide. It has been reported that OSC, as an alternative construction method, has a variety of benefits. However, there is lack of critical review of the building performance (e.g. energy consumption and carbon emissions) of off-site built facilities. Life cycle approach and bibliometric analysis are adopted in this study to review existing research on the environmental performance of off-site built facilities. The results show that most existing studies chose to employ LCA method to systematically analyse carbon emissions and energy consumption of prefabricated residential buildings by using sub-assembly components as functional units. The detailed investigation of volumetric construction and building operational stage are rare. The sensitivity of thermal property caused by offsite manufacturing and onsite assembly in comparison to the traditional cast-in-situ method remains unexplored. It is encouraged to cover various environmental impacts in building performance assessment, to develop a sustainability rating system applied in OSC, to adopt Internet-of-Things in OSC monitoring by using real-time data, and to establish an indicator system for the evaluation of OSC performance. The findings of this study can facilitate the understanding of status quo and shed lights on future research direction in OSC. [ABSTRACT FROM AUTHOR]

Adopting Building Information Modelling (BIM) in Building Performance Analysis (BPA) is becoming an emerging research area in the application of information technology in the Architecture, Engineering, and Construction (AEC) industry. To investigate the current state of research in the adoption of BIM in BPA, this study performed a holistic review consisting of a bibliometric analysis of existing literature, content analysis of selected studies, as well as follow-up qualitative discussion in BIM integration with BPA. The bibliometric analysis identified 60 relevant studies; the content analysis of these studies revealed the research focuses of BIM-enabled BPA, including interoperability, semantics, and sustainability rating systems; the qualitative discussion further highlighted the learning process throughout project delivery stages and addressed the potential gap between 'as-designed' building performance and 'as-built' performance. Overall, this study contributes to existing research by identifying key input attributes and workflow in BPA, reviewing the state-of-the-art research on BIM integration with BPA, and investigating the major research areas, namely, interoperability issues in BIM-enabled BPA within the context of life-cycle BPA. Unlabelled Image • Reviews the state-of-the-art in the BIM-enabled BPA using bibliometric analysis • Defines the workflow of Building Performance Analysis in building design • Investigates issues of interoperability, semantics, and sustainability rating systems • Identifies key research problems in BIM integration with BPA [ABSTRACT FROM AUTHOR]

Abstract This study aimed to address the gap in research regarding the application of integrated design and construction (IDC) project delivery into off-site construction Projects (OSC) within China. A questionnaire survey was designed and delivered to reach Chinese professionals in Architecture, Engineering, and Construction (AEC) disciplines to assess their risk perceptions. Risk was considered in terms of probability and severity. Two main research hypotheses were proposed that AEC professionals' perceptions towards applying IDC in OSC projects would be affected by their experience in OSC or in IDC. Based on a total of 112 valid questionnaire responses, statistical analyses were conducted, including the relative importance index analysis, internal consistency analysis involving Cronbach's Alpha, the one-way analysis of variance, and post-hoc tests. It was indicated that AEC practitioners' experience in both OSC and IDC did affect their perceptions towards the risks. It was further identified that compared to professionals' OSC experience, their experience or knowledge in IDC played a more significant role in affecting their risk perceptions. Those with little experience in OSC or IDC tended to perceive risks with a higher degree of significance. This study contributes to the body of knowledge in terms of integrating OSC with IDC, by addressing the research question of whether the experience level in OSC and in IDC would impact AEC professionals' risk perceptions. Future research could continue this study by adopting empirical case studies to evaluate risks when applying IDC in OSC projects. Highlights • The research focuses on adopting IDC (i.e., integrated design and construction) in OSC (i.e., off-site construction). • Design experience of architects and engineers in OSC was considered most critical risk factor. • Professionals' experience in IDC and in OSC affected their risk perceptions. IDC experience was found more influential in affecting risk perceptions compared to OSC experience. • Those with less experience in OSC or in IDC tended to perceive risks with higher degrees of significance. [ABSTRACT FROM AUTHOR]

• Optimization of mixing approaches of FCRA; • Optimum water content of coarse aggregate of FCRA: semi-dry; • Potential to improve environmental sustainability by the reuse of waste construction materials. Recycling construction wastes as aggregates to replace natural sources to produce concrete has attracted the attention of many researchers and is necessary for sustainable development. The water content of recycled coarse aggregate (RCA) and the concrete mixing approach in preparing fair-faced concrete incorporating recycled aggregates (FCRA) were optimized in this study. The results showed that the slump flow of FCRA exceeds 600 mm and that the 28-d compressive strength reaches approximately 40 MPa, which can meet the requirements of Chinese standards. Compared with concrete prepared with absolute dry RCA and with saturated surface dry RCA, the concrete prepared with semidry RCA better maintains its workability. The adverse effect on the compressive strength of concrete is weakened, which helps improve the structural performance of the ITZ of recycled aggregate concrete (RC). The concrete mixing approach has a significant influence on the physical and mechanical properties of FCRA. Compared with the ordinary mixing method, the 28-d strength of the concrete obtained by the cement stone wrapping approach is increased by 13.33%, and the surface pore area is reduced by 42.6%. Cement stone wrapping in two-stage mixing greatly improves the concrete performance, effectively satisfying the requirements for FCRA. [ABSTRACT FROM AUTHOR]

Abstract In literature, studies on recycled aggregate concrete (RAC) with recycled aggregates (RAs) originated from clay brick waste are rare, which is mainly attributed to the much lower compressive strength of the RAC with recycled clay brick aggregates (RAC-RCBA) when comparing with its normal aggregate concrete (NAC) counterpart. Nowadays it is well known that fiber reinforced polymer (FRP) composites as lateral confining materials can improve the strength and ductility of NAC significantly. In this study, FRP confining materials were used to improve the compressive strength and ductility of the RAC-RCBA. Compared with conventional synthetic glass or carbon FRP composites, polyester FRP (PFRP) and Polyvinyl chloride (PVC) are much cheaper and show much larger tensile deformation capacity. Therefore, this study investigated the axial compressive behavior of PFRP and PVC hybrid tube encased RAC-RCBA (i.e., shortened as PFRP-PVC-RAC-RCBA) structure. This PFRP-PVC-RAC-RCBA system consisted of an RAC-RCBA core, encased by a PVC tube directly and the PVC tube was further confined with a PFRP tube (i.e. PFRP tube-PVC-RAC-RCBA specimen) or PFRP strips (i.e. PFRP strip-PVC-RAC-RCBA) at the outermost layer. Uniaxial compression tests were performed on 33 PFRP-PVC-RAC-RCBA and 39 unconfined RAC-RCBA specimens to evaluate and compare the axial compressive behavior of PVC tube encased RAC-RCBA, PFRP tube encased RAC-RCBA, PFRP tube-PVC-RAC-RCBA and PFRP strip-PVC-RAC-RCBA columns. The tested variables included the number of PFRP layers (3-, 6- and 9-layer), the type of PFRP confinement (in the configuration of tube or strips) and the spacing of the PFRP strips (25 and 50 mm). The tested results demonstrated that the PFRP-PVC hybrid confining system enhanced the compressive strength and axial and lateral deformations of the RAC-RCBA pronouncedly, e.g. the increase in strength ranged from 4.5% to 39.6%. The enhancement in strength and deformations was increased with a thicker PFRP tube or strip. Both the PFRP tube-PVC-RAC-RCBA and PFRP strip-PVC-RAC-RCBA showed the similar axial compressive stress-stain behaviors. In addition, the comparison of PFRP tube-PVC-RAC-RCBA with the glass/carbon FRP tube-RAC-RCBA indicated that the GFRP and CFRP tube confinement resulted in much larger enhancement in ultimate compressive strength of RAC-RCBA due to the much larger tensile modulus and strength of these G/CFRP composites. However, PFRP-PVC tube confinement led to much larger axial deformation of the RAC-RCBA compared with the G/CFRP tube confinement due to the much larger tensile strain of the PFRP and PVC material. Furthermore, design-oriented compressive stress-strain models were developed for PFRP-PVC-RAC-RCBA specimens. [ABSTRACT FROM AUTHOR]

Highlights • This study investigated the relationships among multiple mechanical properties of SCRAC. • Different replacement ratios of SSP had significant impacts on properties of SCRAC. • SSP improved filling ability and passing ability of SCC, but adversely affected segregation resistance. • The 10% replacement ratio of SSP was found achieving both superior mechanical properties and better durability. Abstract This study introduced both steel slag and recycled aggregate aiming to improve the sustainability performance of self-compacting concrete (SCC). The study focused on investigating the effects of steel slag powder on the properties of self-compacting concrete with recycled aggregate (SCRAC). Recycled aggregates were used to replace 30% of natural coarse aggregates by volume. The effects of various replacement ratios of steel slag powder (SSP) to Portland cement (i.e., 10%, 20%, 30%, 40%, and 50%) on the workability, mechanical properties, and durability of SCRAC were studied. The results showed that SSP improved filling ability and passing ability of SCC, but adversely affected the segregation resistance. It was found that 10% replacement ratio of SSP to ordinary Portland cement (OPC) in SCRAC showed superior mechanical properties and higher durability performance in resisting chloride penetration and carbonation. [ABSTRACT FROM AUTHOR]

• A systematic review on situation awareness in construction safety was conducted. • The roles of digital technology in enhancing situation awareness were analyzed. • Theoretical advances and issues of situation awareness for construction safety. • Technology-based situation awareness enhancement mechanisms. The dynamics of construction processes pose significant challenges for workers to perceive, understand, and anticipate hazards on sites. Maintaining an adequate level of situation awareness (SA) is critical for safety. Recent years have seen increasing research interests in SA and digital technology (DT) in the construction safety field. However, there lacks a systematic review that elucidates the impacts of DT on workers' cognitive processes involved in hazard identification. To fill the research gap, the paper aims to conceptualize the role of SA and DT in construction safety management and provide a theoretical basis for the future development of technology-enabled situation-aware construction safety management systems. This study employed a five-step systematic review approach with a scientometric analysis to provide an unbiased and comprehensive overview of research concerning SA in construction safety. The results suggested that current research on the cognitive processes related to hazard identification has been fragmented and has caused theoretical confusion. There is a need to develop a cognitive framework for hazard identification. Four specific research directions were recommended: (1) develop and validate a real-time SA measurement, (2) identify SA information requirements, (3) develop a cognitive model of hazard identification, and (4) develop a technology-enhanced SA system. By synthesizing the current literature, this review paper identified and analyzed the theoretical roles of SA and DT in worker hazard identification, shedding light on the potential for developing a technology-enabled situation-aware construction safety management system. It also offered a valuable perspective to review and re-design safety management practices. [ABSTRACT FROM AUTHOR]

• The study investigated the effectiveness of VR-driven immersive safety training. • Both process and outcome-based data were collected for empirical analyses. • VR-based training outperformed the traditional safety training. • Embodied cognition theory was applied in the VR-based safety training. • VR-based education motivates individual trainees through multiple bodily sensory engagements. The emerging digital technologies such as virtual reality (VR) provide an alternative platform for construction safety training. In order to explore how digital-driven technologies affect the effectiveness of safety training, there is a need to empirically test the differences in performance between digital 3D/VR safety training and traditional 2D/paper approach. This research conducted a performance evaluation that emphasises both the training process and learning outcomes of trainees based on researchers' self-developed immersive construction safety training platform. Data related to physiological indicators such as skin resistance were collected to measure safety performance before and after the training. The detailed measurement indicators included nine categories (e.g., immersion, inspiration) to form a holistic list of evaluation dimensions. The findings revealed that VR-driven immersive safety training outperformed the traditional way for trainees in terms of both process and outcome-based indicators. Results confirmed that safety training was no longer constrained by understanding or memorizing 2D information (texts and images). Instead, trainees experienced a stronger sense of embodied cognition through the immersive experience and multi-sensory engagement by interacting with the VR-driven system. By engaging the theory of embodied cognition, this research provides both the empirical evidence and in-depth analysis of how immersive virtual safety training outperforms traditional training in terms of both training process and outcomes. [ABSTRACT FROM AUTHOR]

• The study adopted immersive virtual reality to gauge safety performance. • The immersive experiments covered hazard recognition, analysis, and reaction. • Task mode and time pressure were adopted as two independent variables. • Double tasking mode increased individuals' cognitive load. • Time pressure is a double-edged sward for task performance. Digital technologies such as Virtual Reality (VR) are gaining momentum in its use to implement and deepen construction health and safety education. In this study, researchers first developed a VR-driven immersive system incorporating real construction site hazard scenarios. Immersive experiments were then conducted by recruiting 40 individuals in construction-related disciplines. Experimental data were collected to evaluate the effects of tasking mode and time pressure on individuals' cognitive load in performing virtual site tasks. The self-evaluation method and task performance-based data were adopted as the complementary ways to measure individuals' cognitive load in completing given tasks. Compared to the single tasking mode of solely focusing on site hazard recognition, analysis, and reaction, the added secondary task was found significantly increasing individuals' cognitive load and lowering task performance. Time pressure could be a double-edged effect depending on the task feature. Recommendations were provided for real site safety management in balancing employees' wellbeing and site productivity. The current study extends prior research on enhancing construction health and safety where the main focus has been on hazard detection but now incorporates also hazard analysis and reaction. It also leads to more future research such as measuring individuals' cognitive load in a real site environment. [ABSTRACT FROM AUTHOR]

• Samples containing 6% bone ash cured for 28 days had the best compressive strength. • Multivariate regression models were used for strength prediction and analysis. • Non-linear and mixed models performed better than linear models. • The best-fit statistical models were identified for the compressive strength prediction at the highest R2 value of 97%. • The effects of individual independent variables in predicting the strength of stabilized lateritic soil indicated that bone ash content had the most significant effects. Substantial amount of time, financial resources and energy are required to obtain experimental data on the compressive strength of building components. Application of multivariate regression models in predicting the strength of stabilized lateritic soil has the potential of reducing the time and cost of construction projects in Nigeria. This study is aimed at developing multivariate models for predicting the strength of lateritic soils stabilized with bone ash for sustainable construction. Different percentages of bone ash were used to stabilize lateritic soil. The lateritic brick samples obtained were cured at different temperatures and ages. The samples were tested to obtain their compressive strength. Multivariate and non-linear models were used to predict the compressive strength of the lateritic bricks. A mixed model with R2 of 97% was identified as the best-fit statistical model. The usefulness of the models is limited to the range of variables used but for a more universal application, wider ranges of variables can be explored. This model has practical application for the prediction of compressive strength of stabilized lateritic soil for sustainable housing construction in Nigeria. [ABSTRACT FROM AUTHOR]

• Nano-particles were used to improve recycled aggregate concrete (RAC) properties. • Effect of replacement ratios of recycled aggregates on RAC properties was studied. • Effect of dosages of nano-particles on RAC properties was studied. • Effect of mixing method of nano-particles on RAC properties was studied. In this study, different nano-particles were used to modify recycled aggregates concrete (RAC) containing recycled clay brick aggregates (RCBAs) to improve the RAC properties. Two stages of experimental works were performed. In the first stage, various nano-particle mixtures produced by different mixing methods, i.e. the use of surfactant and ultrasonication, were examined by optical microscope to evaluate the dispersion of the nano-particles in water liquid. The nano-particles modified cement mortar specimens were further evaluated by flexural tensile test to check how these mixing methods affect the properties of the nano-particle modified cement mortar. In the second experimental stage, the effects of four replacement ratios of recycled aggregates, three type of nano-particles, two mixing methods of RAC, additional surfactant and ultrasonication process used in the mix of nano-particle liquid, and the dosages of the nano-particles on the workability, compressive and split tensile properties of the nano-particle modified RAC were investigated. [ABSTRACT FROM AUTHOR]