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Rubbercrete is made of partially replacing fine aggregate, in normal concrete, with crumb rubber (CR) from scrap tires. Despite several advantages of rubbercrete, one of the most hindering factors on using it in the construction industry is the absence of specific mix design to optimize the mix ingredients. Response surface methodology (RSM) optimization has been incorporated using the design expert to eliminate the difficulty in obtaining the anticipated results. Experimental data of 45 rubbercrete mixtures (from the previous study) have been utilized to develop ANOVA models. These models have also been validated to predict the properties of rubbercrete based on different percentages of CR content and w/c. All models are significant with Prob > F is less than 0.05, and the difference between predicted R-squared and adjustable R-squared is less than 0.2. Also, an experimental validation has been performed for three of the optimized mixtures, and the results have been compared, and the variation in the results have found to be less than 5%. It has been concluded that the optimization can be performed for any target strength with desirability as approximately one by improving the performance, reliability for the product and processes.

An engineered cementitious composite (ECC) is a type of high-performance fibre-reinforced composite developed based on micromechanical principles. To improve the modulus of elasticity and minimise the drying shrinkage in self-compacting (SC) ECC without adversely affecting its ductility, nano-silica (NS) is included in the cementitious composite. Twenty SC-ECC mixtures were proportioned, cast, cured, and tested to determine the fresh and hardened properties by using two variables: polyvinyl alcohol (PVA) fiber and NS particles. Five levels of NS (0%, 1%, 2%, 3%, and 4%) and four levels of PVA (0.5%, 1%, 1.5%, and 2%) were considered. A response surface methodology was used to conduct multi-objective optimisation and develop mix proportions that produce the best response to the compressive strength, modulus of elasticity, and energy absorption. It was found that mixtures with 2% PVA and 1.89% NS produce the most desirable responses.

In the production of sustainable concrete, it is quite essential to develop highly reactive silica rich materials to substitute cement. Sugarcane bagasse ash as one of the agricultural based pozzolan gained less popularity due to its relatively low amorphous silica content after incineration process (

In this research, performance of limestone and oil palm shell (OPS) as the alternative aggregates in fly ash based geopolymer concrete was evaluated based on the fresh and hardened concrete test. Fly ash and oil palm shell were studied due to their abundant availability as industrial and agricultural waste. Experimental works were conducted by replacing the portion of coarse and fine aggregate in concrete with limestone and oil palm shell in various percentages. Evaluation of its performance was done based on slump, compressive strength, and porosity test. Microstructure analysis was added via Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray (EDX) test to support the generated hypothesis. From the fresh properties test, the increasing amount of limestone and OPS have shortened the setting time of fresh geopolymer concrete, even though they presented small variations in the slump's height and diameter results. The availability of Calcium Aluminate Silicate Hydrate (C–A–S–H) structure in limestone based specimen and higher polycondensation rate due to optimum water content in OPS based specimens have stimulated the rapid production of geopolymer gel and improved the strength performance of geopolymer concrete in ambient curing condition. Moderate water absorption from OPS fibers and additional dissolution of Al and Si elements due to formation of C–A–S–H gels from limestone inclusion have presented 10% OPS and 25% limestone as the optimum replacement to river sand and coarse granite aggregate, respectively. In ambient curing, 25% limestone presented a 35.23% higher strength while 10% OPS had 11.01% higher strength than control. An escalation to the curing temperature reduced the efficiency of both aggregates, where only 25% limestone was able to produce specimen with 2.34% higher strength than control A supportive analysis from SEM and EDX has also revealed the existence of poly(sialate), poly(sialate-siloxo), poly(sialate-disiloxo) and sialate link in the geopolymer matrix. From this research, the applications of limestone and oil palm shell in geopolymer concrete have presented a nurturing result, particularly as the alternative aggregates in ambient-cured application.