Geopolymer binder and recycled aggregates are considered as the two important sustainable ingredients in concrete production. Ground granulated blast furnace slag (GGBS) and fly ash combination based geopolymeric recycled aggregates concretes (GRAC) were prepared as a substitution of normal concrete in order to reduce the consumption of ordinary Portland cement and natural aggregates as well as to make use of demolished waste concrete. The aim of this study is to investigate the combined effects of GGBS and fly ash considering water-binder (W/B) ratio on the fresh and hardened properties of alkali activated GRAC. The slump, setting time, compressive strength, stress-strain relation, elastic modulus, Poisson's ratio, toughness and failure mode of alkali activated GGBS and fly ash based GRAC containing 100% recycled coarse aggregates were experimentally examined. In addition, the hydration mechanisms were studied by XRD and SEM. Finally, the failure mechanism of this kind of novel green concrete subjected to compression was revealed. The results show that GGBS and fly ash exhibits a superior synergetic effect on the performance of GRAC, i.e. fly ash and GGBS are mainly responsible for the workability and mechanical properties, respectively. GGBS/fly ash ratio has a significant influence on the fresh and hardened properties of GRAC. Moreover, the effect of W/B ratio on GRAC strongly depends on the GGBS/fly ash ratio. GGBS content at less than 25% was found to slightly influence the consistency and compressive strength of GRAC. The combination of 50% GGBS and 50% fly ash with a 0.5 W/B ratio could provide excellent mechanical performance and workability for GRAC.

Effects of combined usage of GGBS and fly ash on workability and mechanical properties of alkali activated geopolymer concrete with recycled aggregate

Properties and utilizations of waste tire rubber in concrete: A review

Concrete is a composite material that is widely used in the construction industry due to its excellent mechanical and physical properties. Despite these benefits, concrete possesses several disadvantages including negative environmental impacts and mechanical durability (e.g., shrinkage, frost attack, and corrosion). To date, upgrading of concrete's properties to overcome such drawbacks has been one of the most challenging, but attractive, research topics for many researchers in this research field. As one of the effective means to meet such demand, the use of natural zeolites in the production of concrete has been made preferably to acquire the excellent performance along with improvement in terms of structure, durability, and mechanical properties. This review was designed to provide a comprehensive insight into the construction-related applications of natural zeolite. To this end, we discussed the structural and fundamental properties of natural zeolites and their applications to concrete production as natural pozzolans, internal curing agents, and lightweight aggregates. Also, through critical analysis of various researches made previously, we aim to offer a better understanding on the effect of zeolites' addition upon the performance of concrete in terms of workability, strength, durability, and permeability. Additionally, we describe the present challenges and future perspectives in the use of natural zeolites for concrete production.

Zijian Li

Papers

Effects of the addition of silica fume and rubber particles on the compressive behaviour of recycled aggregate concrete with steel fibres