Compressive Strength and Thermal Conductivity of Fly Ash Geopolymer Concrete Incorporated with Lightweight Aggregate, Expanded Clay Aggregate and Foaming Agent

doi:10.37358/rc.70.19.11.7695

Abstract

This paper investigates the effect of incorporation of lightweight aggregate and foam in the preparation of lightweight aggregate geopolymer concrete (LWAGC) and lightweight aggregate foamed geopolymer concrete (LWAFGC). The geopolymer paste was formed by alkali activation of Class F fly ash in mixture of sodium silicate and sodium hydroxide solution. LWAGC was incorporated with expanded clay lightweight aggregate and river sand while hydrogen peroxide was added as foaming agent for LWAFGC. Results showed that LWAGC and LWAFGC achieved an excellent 28-day compressive strength of 60 MPa and 20 MPa, respectively. The bulk densities were 1815 kg/m3 for LWAGC and 1593 kg/m3 for LWAFGC. Even so, low thermal conductivity of 0.12 W/mK and 0.09 W/mK were reported. It was concluded that the joint effect of lightweight aggregate and foam produced geopolymer concrete with good mechanical strength while having excellent thermal insulating properties. The geopolymer concretes possessed high strength-to-density ratio to be regarded as lightweight high-performance structures. Keywords: Lightweight Concrete; Geopolymer; Expanded Clay Aggregate; Foam

Highlights

This paper investigates the effect of incorporation of lightweight aggregate and foam in the preparation of lightweight aggregate geopolymer concrete (LWAGC) and lightweight aggregate foamed geopolymer concrete (LWAFGC)
LWAGC was incorporated with expanded clay lightweight aggregate and river sand while hydrogen peroxide was added as foaming agent for LWAFGC
Sodium aluminosilicate hydrate (NASH) is formed in Si- and Al-rich precursor materials while heterogeneous matrix of NASH, calcium aluminosilicate hydrate (CASH) and/or calcium silicate hydrate (CSH) is formed in geopolymer based on high calcium precursor material [7, 8]

Summary

Introduction

This paper investigates the effect of incorporation of lightweight aggregate and foam in the preparation of lightweight aggregate geopolymer concrete (LWAGC) and lightweight aggregate foamed geopolymer concrete (LWAFGC). It was concluded that the joint effect of lightweight aggregate and foam produced geopolymer concrete with good mechanical strength while having excellent thermal insulating properties. The advantages of lightweight concretes are high strength to weight ratio, superior thermal insulation and acoustic properties. They are mostly used in construction of pavements, bridge and roof deck, partition and wall panels, masonry block and bricks and precast concrete units [1013]. Class I defines structural lightweight concrete with density in the range of 1440 -1840 kg/m3, a minimum compressive strength of 17 MPa and thermal conductivity (TC) between 0.4 -0.7 W/ mK. The presence of lightweight aggregate and foaming agent in geopolymer matrix introduces pores which affect markedly the density, porosity, mechanical strength and thermal conductivity of geopolymers

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Conclusion