Towards Sustainable Composite Building Material: Integrating Lime with Slag for reduced mortar Thermal Conductivity

Sule Adeniyi Olaniyan

doi:10.24018/ejers.2020.5.4.855

Abstract

Lime Based Mortar became very popular due to its outstanding features of flexibility, permeability and low carbon emissions. However, lime’s characteristic delayed setting, late hardening time, low mechanical strength, among others, overshadowed significance of its outstanding features, thereby putting its overall use into decline, particularly, with the 19th century Portland Cement discovery. This study therefore aims at reviving lime usage through a sustainable lime composite, by integrating an industrial by-product, Ground Granulated Blast Furnace Slag (slag) with lime, in form of lime-slag mortar, with a view to reducing the mortar thermal conductivity. The methodology involved mortars with the same Binder/Aggregate (B/A) mix ratio (1:3) using five separate volumetric compositions of ‘slag-lime’ binders (i.e. 1:1, 1:2, 1:3, 2:1 and 3:1). Physical properties of the mortars involving their Water/Binder (W/B) ratios, Air Contents and Bulk Densities were recorded. Comparative evaluations of the compositions in hardened state, involving thermal conductivities were carried out at specific intervals through a twelve-month curing period. These were partly monitored through assessments of the composites’ microstructural behaviours over a six-month period. Results of the investigation show that addition of slag to mortars facilitate slightly larger pores with increased porosities. However, these effects are minimal (i.e. from 23.42% to 25.37% porosity) when slag content is at equal volumetric content with lime. A general reduction (not in a linear trend) in the thermal conductivities of the mortar with increasing slag content was observed, cumulating in 25% decrease in the composites having thrice volumetric content of slag, relative to lime. Composite’s reduced thermal conductivity would be of utmost importance in construction especially, where material’s limited thermal conductivity property is of utmost importance.

Highlights

In the recent years, rapid urbanization had played a major role in degrading the urban environment through construction processes
Climate change and global warming are associated with CO2 emission and Green House Gases (GHG) for which the current global level needs to be cut by about 50% by 2050 [3]
Efforts must be directed at exploring alternative methods, and search for new technical standards, towards development of sustainable building materials [9]-[11]

Summary

Introduction

Rapid urbanization had played a major role in degrading the urban environment through construction processes. While a considerable part of this energy is commonly used to control internal microclimate conditions, other part is used to extract raw materials, transport them, make building components and, to dispose of them. Interventions in this important productive sector through promotion of low-impact building techniques and materials should be encouraged, to address the global challenge [6]-[8]. Efforts must be directed at exploring alternative methods, and search for new technical standards, towards development of sustainable building materials [9]-[11]. One major step in this direction is revival of a partially abandoned age-long environmentally sustainable building material, lime mortar

Objectives

Methods

Findings

Conclusion