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

Fly ash-based eco-friendly geopolymer concrete: A critical review of the long-term durability properties

The past and future of sustainable concrete: A critical review and new strategies on cement-based materials

Geopolymer concretes (GPCs) can be produced by chemical activation of industrial by-products and processed natural minerals that contain aluminosilicate. There have been a few demonstrative constructions built using of GPCs as a greener alternative choice to Portland cement concrete (PCC); unfortunately, there is no standard or specification of guidelines for the design of GPC mixtures. This is partially because of so many variables affecting GPC manufacture, such as the property of raw materials, type and dosage of activator and curing scheme. Despite the fact of convention of building industry, the lack of proper mixture design method limits the wide acceptance of GPC in industry. In this paper, a review on currently reported mixture design methods of GPC prepared with slag and fly ash is presented. The various methods are classified into three categories: target strength method, performance-based method, and statistical factorial model method. The difference in the procedures, advantages and disadvantages among those methods are discussed. It is recommended that a proper design method should be chosen according to actual production situation and performance requirement of GPC.

Chi Fang

Papers

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

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

Experimental study on the compressive and flexural behaviour of recycled aggregate concrete modified with silica fume and fibres

Combination effects of rubber and silica fume on the fracture behaviour of steel-fibre recycled aggregate concrete

Study on the optimum initial curing condition for fly ash and GGBS based geopolymer recycled aggregate concrete