INFLUENCE OF SUPERPLASTICIZERS ON THE PERFORMANCE OF GEOPOLYMER CONCRETE DEVELOPED BY A BINARY-WASTE BINDER

Document Type : Original Article

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Structural Engineering Department, Faculty of Engineering, Ain Shams University, Cairo, Egypt

Abstract

Geopolymer Concrete (GPC) has emerged as a sustainable alternative to traditional cement-based concrete owing to its lower carbon footprint and utilization of industrial by-products. However, challenges related to its workability persist, limiting its widespread adoption in structural applications. This study investigates the effect of 4 different types of superplasticizers, three naphthalene-based and one polycarboxylate-based, on the workability and compressive strength of binary waste-based GPC, aiming to improve its fresh-state properties. The reference mix comprised a binder content of 450 kg/m³, consisting of 60% ground granulated blast furnace slag (GGBFS) and 40% waste glass powder (WGP), with a water-to-binder ratio (W/B) of 0.45, a solution modulus (Ms) of 1, and a sodium oxide (Na₂O) content of 9% by binder weight. The superplasticizers were used at a fixed dosage of 2% by weight of the binder. The workability was assessed through slump and slump loss tests. The findings revealed that the initial slump of the developed mixes was similar to the reference mix; however, slump loss results indicated that the admixtures used in this study were ineffective in extending the duration of workability retention of GPC mixes, suggesting poor compatibility with GPC compared to conventional cement-based concrete. Moreover, most of the tested admixtures significantly reduced the compressive strength of the GPC mixes compared to the reference mix; expect for the mix incorporating the naphthalene-based admixture Type G (low-range water reducer), which attained a 28-day CS of 42.9 MPa, closely matching that of the reference mix.

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