Waste tire rubber constitute a serious worldwide problem due to the lack of landfills and the health hazards associated with these landfills. In addition to the environmental motivation for providing a means of recycling large quantities of waste tire rubbers, the use of tire rubber particles provides a new type of concrete that has unique mechanical and fracture criteria. This paper presents the results of recent experimental investigations on rubber concrete. Chipped and crumbed tire rubber particles were used to replace coarse and fine aggregate with different volume replacement levels. The mechanical and fracture properties of rubber concrete were examined. Quasi-brittle fracture mechanics models are used to determine the effect of incorporating tire rubber particles on the fracture performance of rubber concrete. Finally, some microstructural features of rubber concrete are also reported. It is concluded that the choice of the optimal replacement ratio of the tire rubber particles can yield concretes...

Numerous regulations have been imposed worldwide by governments and environmental organizations in order to reduce the negative environmental impact resulting from large numbers of solid waste landfills. Recycling of industrial by-products is a step toward sustainable waste management. By utilizing ceramic waste powder (CWP) as a partial cement replacement, the construction industry can play a significant role in energy conservation and limit future generations of ${\mathrm{CO}}_2$ . This paper examines the feasibility of producing self-compacting concrete (SCC) mixtures yielding acceptable fresh and hardened concrete characteristics with the inclusion of high-volume CWP as partial replacement of cement. The fresh properties of the new SCC are evaluated through various tests (i.e., slump flow, J-ring, column segregation, V-funnel, and L-box). The investigations show a slight reduction in the slump flow but with an enhancement of the other fresh properties. In addition, the use of CWP slightly reduces compressive strength. It is shown that it is possible to produce SCC with acceptable properties incorporating high-volume CWP.

Incorporating solid waste materials in concrete has three advantages – the immediate environmental benefit of recycling a material from landfills, reducing the negative impact of cement production and preserving natural resources. Ceramic waste powder (CWP), produced during the process of polishing ceramic tiles, is dumped in landfills and can cause soil, air and groundwater pollution leading to serious environmental problems. CWP is mainly composed of silicon dioxide and aluminium oxide (>80%), making it a good candidate in concrete manufacturing. This study investigated the use of CWP in producing conventional (CV) concrete and self-compacting concrete (SCC). CWP was used as a partial cement replacement: by 10, 20, 30 and 40% in CV mixtures and by 28 and 57% in SCC mixtures. Fresh properties, compressive strength development and durability characteristics of the different concretes showed that CWP could be successfully used as a partial cement replacement. The optimum replacement for CV mixtures was found to depend on the concrete strength grade. For the 25 MPa mixture, the optimum replacement level was 10–30%, while it was 20 or 30% for the 50 MPa mixture. For SCC mixtures, as far as strength is concerned, a 28% replacement level can be used while, for fresh and durability characteristics, both 28 and 57% are acceptable.

This study assesses the effect of mix design parameters on the fresh and hardened properties, cost, and carbon footprint of geopolymer mortar made with desert dune fines (DDF) and blast furnace slag (BFS). Taguchi method was employed in designing the experiments. Four factors were considered, each having three levels, leading to a total of nine geopolymer mortar mixes. The factors comprised the DDF replacement percentage, alkali-activator solution to binder ratio (AAS/B), sodium silicate-to-sodium hydroxide ratio (SS/SH), and sodium hydroxide (SH) molarity. Ten performance criteria were evaluated, including the flowability, final setting time, hardened density, 1, 7, and 28-day compressive strengths, water absorption, sorptivity, cost, and carbon footprint. ANOVA was carried out to estimate the contribution of each factor towards the response criteria. Further, TOPSIS analysis was utilized to optimize the mixture proportions of DDF-BFS blended geopolymer mortar. Experimental results showed that up to 25% DDF replacement enhanced the density, strength, and durability of the geopolymers with minor impact on the flowability and setting time. Higher replacement percentages had a detrimental impact on the performance but could still be utilized in specific mortar construction applications. The other factors had more limited contributions to the performance, evidenced by the ANOVA. TOPSIS method revealed the optimum mix to be made with DDF replacement of 25%, AAS/B of 0.5, SS/SH of 1.5, and SH molarity of 10 M. Different multivariable regression models were also developed to predict the fresh and hardened properties of the DDF-BFS geopolymer mortars using the mix design parameters.