Physicomechanical properties of nano-silica effect on geopolymer composites

Hisham Mustafa Mohamed Khater

doi:10.34118/jbms.v3i1.20

Abstract

Addition of Nano-SiO2 (NS) to geopolymer composites has been studied through measurement of compressive strengths, Fourier Transformer Infra-Red (FTIR) and X-ray diffraction (XRD) analysis. Alumino–silicate materials are coarse aggregate included waste concrete and demolished walls with its cementing binder, cement kiln dust (CKD) used and can possess a pronouncing activation for the geopolymer reaction resulting from the high alkali contents within. Materials prepared at water/binder ratios in a range of 0.30: 0.40 under curing of 40 oC and 100% R.H, while the used activator is sodium hydroxide in the ratio of 2 wt. %. First, CKD is added in the ratio from 10 up to 50 wt., %, and the demolished walls was varied depending on the used CKD content, while using constant ratio of waste concrete (40 wt., %). Second step, depending on the optimum CKD ratio resulted from the first one (40 wt. %), so the control geopolymer mix composed of CKD, demolished walls and waste concrete in the ratio (40:20:40, wt %). NS partially replaced waste concrete by 1 up to 8%. Results indicated that, compressive strengths of geopolymer mixes incorporating NS were obviously higher than those control one, especially at early ages and specially with 3%NS.

Highlights

In this new century, the Nano-structured material technology developing at an astonishing speed and will be applied extensively with many materials
As the need for the development of alternative eco-friendly building materials, alkali-activated binders has been promoted by the growth of the building industry, the increased performance requirements placed upon materials, and the higher sustainability criteria applied in construction
The aim of this paper is to study the effect of nano-silica addition on the physico-mechanical characteristics of the resulting geopolymer materials produced from construction and demolition wastes producing cementless materials that can be applied in many building applications

Summary

Introduction

The Nano-structured material technology developing at an astonishing speed and will be applied extensively with many materials. As known C–S–H gel in cement is a common building material where its main hydrate product is a natural Nano-structured material (Taylor, 1993; Richardson, 2000; Zhang et al, 2000). Whilst the addition of Nano-materials in cement and concrete can lead to an extra improvements in the nanostructure of hydrated building materials (Aiu and Huang, 2006). As the need for the development of alternative eco-friendly building materials, alkali-activated binders has been promoted by the growth of the building industry, the increased performance requirements placed upon materials, and the higher sustainability criteria applied in construction. Alkali-activated binders offers an attractive partial or complete substitution of Portland cement in the production of mortars and concretes, offering comparable performance and cost (Duxson et al, 2007-a) while reducing greenhouse gas emissions (Duxson et al, 2007-b). In the activation of aluminosilicate precursors; the most relevant characteristics related to the alkali activator are: the type of alkaline salt (usually silicate or hydroxide) (Van Jaarsveld and Van Deventer, 1999; Phair and Van Deventer, 2001; Fernández-Jiménez and Palomo, 2005); the method of addition of the alkaline component (as a solution or in solid-state) (Yang et al, 2008; Yang and Song, 2009; Hajimohammadi 2008) and the dosage of the alkali

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