Utilization of Treated Agricultural Residue Ash as Sodium Silicate in Alkali Activated Slag Systems.

Feraidon F Ataie

doi:10.3390/ma14020329

Abstract

This study investigated the influence of rice straw ash (RSA), rice husk ash (RHA), and silica fume (SF) on alkali activated slag (AAS) systems. RSA, RHA, and SF were treated with sodium hydroxide to improve their reactivity in AAS systems. Although addition of SF in AAS systems increased compressive strength, samples containing RSA or RHA had higher compressive strength than those having SF. Treated RSA or RHA further increased compressive strength of AAS samples. It was shown that samples containing treated ash samples had similar compressive strength to those made with sodium silica activator. Therefore, it is suggested that treated ash samples could be used as alternative sources of silica for AAS. Drying shrinkage of AAS samples increased considerably when treated RSA or RHA were used as partial replacement of slag. This could be attributed to higher silica modulus (SiO2/Na2O) ratio of samples containing treated ash, which in turn would lead to a finer pore size structure compared to control samples. However, SF significantly reduced drying shrinkage of AAS. This could be because SF reduces the permeability and porosity of AAS samples.

Highlights

Concrete is the most used substance in the world after water [1]
This study investigated the impact of Rice Straw Ash (RSA), Rice Husk Ash (RHA), and silica fume (SF) on the compressive strength, heat of hydration, and drying shrinkage of alkali activated slag systems
Kinetics to investigate the impact of rice straw ash (RSA), rice husk ash (RHA), and SF on hydration kinetics of alkali activated slag

Summary

Introduction

The production of portland cement, which is an essential ingredient of concrete, is an energy intensive process. This process is responsible for approximately 8% of the global carbon dioxide (CO2 ) emission [2,3]. Most of this CO2 emission comes from calcination of limestone during the portland cement production process [1,2]. Increasing the efficiency of cement production process, improving the efficiency of cement in concrete, facilitating the partial replacement of cement in concrete, increasing concrete durability, and using alternative cementitious materials are among the plausible strategies to reduce the carbon footprint of concrete [1,4].

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