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

Use of geopolymer concrete for a cleaner and sustainable environment – A review of mechanical properties and microstructure

A critical review of geopolymer properties for structural fire-resistance applications

Mechanical and thermal properties of fly ash based geopolymers

A laboratory investigation of steel to fly ash-based geopolymer paste bonding behavior after exposure to elevated temperatures

Loess, which primarily consists of wind-transported silt and clay particles, is widely distributed around the world, including the central Asia, central Europe, the northwestern and central United States, Alaska, and South America. The metastable structure of natural loess has resulted in construction delays and catastrophic failures. To explore the potential applications of soil improvement with green materials, this paper presents an experimental study of applying fly ash–based geopolymers for the loess stabilization. Two different precursors are employed to the investigation. It is found that potassium hydroxide renders a higher unconfined compressive strength than sodium hydroxide to the samples when the same fly ash/loess ratio is applied. This agrees with the results of the mechanical properties of the two different geopolymers. With an increasing fly ash/loess ratio, the compressive strength and Young’s modulus increase. The microstructural characterization unveils that a compact and stable...

Feasibility Study of Loess Stabilization with Fly Ash–Based Geopolymer

Aiming to solve the problems caused by the construction and demolition waste and the depletion of natural aggregates, in the present study, both the coarse recycled aggregates and the fine recycled aggregates are used to produce new green concrete with a fly ash–based geopolymer. The mechanical study shows that the reduction rates of the compressive strength, Young’s modulus, and the Poisson’s ratio of the geopolymeric recycled aggregate concrete (GRAC) specimens increase with the increase of the water/cement (w/c) ratio. The Young’s modulus is much more vulnerable to the increase of the w/c ratio than the compressive strength. These significant changes to the GRAC samples could be attributable to the deteriorated properties rendered to the geopolymer by the increase of the w/c ratio. When the minimum ratio of w/c is applied, the fly ash–based geopolymer renders better mechanical properties to the concrete specimens than the ordinary portland cement. With the aid of scanning electron microscopy an...

Fenghong Fan

Papers

Mechanical and thermal properties of fly ash based geopolymers

Feasibility Study of Loess Stabilization with Fly Ash–Based Geopolymer

Experimental Study of the Geopolymeric Recycled Aggregate Concrete