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This paper studies the fresh and mechanical properties of high-strength concrete (HSC) by incorporating recycled concrete aggregates (RCA) of varying sizes and concentrations. The recycled aggregate concrete (RAC) was prepared by partially replacing RCA with natural coarse aggregate (NCA) at 0%, 15%, 30%, and 45%, with aggregate sizes ranging from 5 to 12 and 12–20-mm. Fresh concrete properties, such as slump, Kelly ball, compacting factor, K-slump, and fresh density, were tested to determine the influence of RCA size and concentration. In addition, the mechanical properties were studied through the execution of compressive, split-tensile, and stress-strain tests. The test results revealed that increasing the RCA concentration declines the fresh and hardened properties of HSC. In the fresh concrete experimentation, the 12–20 mm aggregate size RAC mixes exhibited greater workability than the 5–12 mm aggregate mixes. On the contrary, 5–12 mm aggregate mixes RAC had higher compressive and split-tensile strength and a higher modulus of elasticity than 12–20 mm aggregate mixes concrete. When it comes to sustainability, the study found that the smaller size range of RAC produces inferior embodied CO2 (eCO2) and provides a cost-effective and sustainable solution for the construction industry.

This research aims to assess the rheological and mechanical characteristics of Self-compacting concrete (SCC) incorporating waste tire rubber aggregates (WRTA) as an interim substitute for coarse aggregates. However, the standard experimental modeling approach has significant obstacles when it comes to overcoming the nonlinearity and environmental susceptibility of concrete parts. Therefore, linear regression (LR) and extreme gradient boosting (XGBoost) were used as two standard single machine learning (ML) models to predict the aforementioned rubberized SCC features. In this study, conventional coarse aggregates were supplanted with WRTA at 0%, 5%, 10%, and 20% to uncover the optimal proportion of coarse aggregates substituting rubber. To find the optimum amount of WRTA to use as a substitute, the study follows the impacts of rubber on the self-compacting rubberized concrete's (SCRC) rheological and mechanical characteristics. The consequences on fresh properties were investigated by the slump flow, J-ring, and V-funnel tests, while compressive and splitting tensile strengths tests were conducted to assess mechanical properties. Increasing WRTA test outputs indicated a deterioration in workability and hardened qualities. While a 10% swapping ratio is deemed feasible for producing SCRC, optimal results were achieved by reducing environmental impacts and efficiently managing a significant volume of rubber tire waste with a 5% substitution of rubber within the coarse aggregates. The research findings indicated a noticeable decrease in fresh properties as the WRTA content increased. Notably, after 28 days, a 10% WRTA substitution led to a 34% reduction in compressive strength and a 28% decrease in splitting tensile strength, satisfying ACI standards. Furthermore, XGBoost demonstrated superior predictive performance with the highest R2 values, outperforming the LR model and affirming its efficacy in delivering more accurate predictions.

This paper focuses on the investigation of fresh, mechanical, and durability properties of concrete with the influence of fly ash and polypropylene fiber. In this study, cement was partially replaced by 15 % and 30 % fly ash content in weight, whereas polypropylene fiber was incorporated in concrete mixes at 0.06 %, 0.12 %, and 0.18 % by volume. Twelve concrete mix proportions were developed, and slump, density, ball penetration, and compacting factor tests were conducted to examine the fresh concrete properties. Besides, mechanical characteristics, including the uniaxial compressive and splitting tensile strength of concrete, were evaluated at 7, 28, and 90 days. Further tests of concrete durability, including rapid chloride permeability test, sorptivity, and water penetration, were performed at 90 days. The results exhibited that the incorporation of fly ash developed fresh concrete properties, while polypropylene fiber decreased the fresh characteristics of concrete. Furthermore, the combination of fly ash and polypropylene fiber in concrete was substantially attained to improve the mechanical and durability characteristics compared to the control mix. Mix proportion of 15 % fly ash and 0.12 % polypropylene fiber exhibited a pronounced influence on compressive strength, chloride permeability, sorptivity, and water penetration compared to other concrete mixtures.

The utilization of waste fly ash and natural jute fiber has drawn attention to producing sustainable concrete. However, there is a lack of studies to analyze the synergistic effect of jute fiber and fly ash on the properties of concrete. Hence, the aim of this study is to investigate the combined effect of fly ash concentration and the different sizes of jute fiber on the fresh, hardened, and non-destructive testing properties of concrete. Concerning the purpose, the concrete mixes were prepared with 0.2 % and 0.4 % jute fiber incorporating 0 %, 5 %, 10 %, and 15 % replacement of cement by fly ash in concrete. For the assessment of properties, slump, density, and compacting factor test was conducted at the fresh state of concrete, whereas mechanical properties such as compressive, splitting tensile, and flexure strength test were conducted at 7 and 28 days. In addition, the non-destructive test (NDT) was also carried out to predict the destructive compressive strength by rebound hammer at 28 days. The microstructure property of optimum mix concrete was analyzed by scanning electron microscopy (SEM). It is observed that the incorporation of jute fiber decreased the slump, density, and compacting factor but increased the compressive, splitting tensile, and flexure strength, whereas the fly ash improved both fresh and hardened properties. Compared to the standard mix, fly ash-based JFRC mixtures have compressive strength improvements varying from 1.7 % to 25.9 %. The 10 % fly ash and 0.2 % volume of jute fiber exhibited a maximum of 11.64 % and 10.72 % splitting tensile and flexural strength enhancement at 28 days, respecting the control mix. In addition, the NDT strength assessment obtained 5.5 % less than destructive strength on average. From the SEM point of view, it is obtained that the 10 % fly ash with 0.2 % jute fiber composition matrix exhibits a better bonding interface and the cracking resistance nature of the concrete mix.

The incorporation of waste materials generated in many industries has been actively advocated for in the construction industry, since they have the capacity to lessen the pollution on dumpsites, mitigate environmental resource consumption, and establish a sustainable environment. This research has been conducted to determine the influence of different rice husk ash (RHA) concentrations on the fresh and mechanical properties of high-strength concrete. RHA was employed to partially replace the cement at 5%, 10%, 15%, and 20% by weight. Fresh properties, such as slump, compacting factor, density, and surface absorption, were determined. In contrast, its mechanical properties, such as compressive strength, splitting tensile strength and flexural strength, were assessed after 7, 28, and 60 days. In addition, the microstructural evaluation, initial surface absorption test, = environmental impact, and cost–benefit analysis were evaluated. The results show that the incorporation of RHA reduces the workability of fresh mixes, while enhancing their compressive, splitting, and flexural strength up to 7.16%, 7.03%, and 3.82%, respectively. Moreover, incorporating 10% of RHA provides the highest compressive strength, splitting tensile, and flexural strength, with an improved initial surface absorption and microstructural evaluation and greater eco-strength efficiencies. Finally, a relatively lower CO2-eq (equivalent to kg CO2) per MPa for RHA concrete indicates the significant positive impact due to the reduced Global Warming Potential (GWP). Thus, the current findings demonstrated that RHA can be used in the concrete industry as a possible revenue source for developing sustainable concretes with high performance.

This research work is devoted to the experimental investigation of both rheological and mechanical properties of self-compacting concrete (SCC) produced with waste galvanized copper wire fiber and rice husk ash (RHA). In the study, three different volume fractions of 0.5 p to 0.75 percent, 1 percent of scrap copper wire fiber as reinforcing material, and 2 percent RHA as cement replacement were used. To evaluate the fresh characteristics of SCC, the slump flow, J-ring, and V-funnel experiments were conducted for this investigation. Compressive strength, splitting tensile strength, and flexural strength of the concrete were conducted to assess the hardened properties. The test was carried out to compare each characteristic of plain SCC with this modified SCC mixture, containing RHA as pozzolanic materials and copper fiber as reinforcing material. Incorporating copper fiber in the SCC leads to a drop in fresh properties compared to plain SCC but remains within an acceptable range. On the other hand, the inclusion of 2% RHA makes the SCC more viscous. Although adding 2% RHA and 1% copper wire in SCC provide the highest strength, this mix has an unacceptable passing ability. The SCC mix prepared with 2% RHA and 0.75% copper fiber is suggested to be optimum in terms of the overall performance. According to this study, adding metallic fiber reinforcement like copper wire and mineral admixture like RHA can improve the mechanical properties of SCC up to a certain level.