Fracture parameters of fly ash geopolymer mortars with carbon black and graphite filler

H Simonova,P Schmid,M Lipowczan,C Mizerova,P Rovnanik

doi:10.1088/1757-899x/1205/1/012019

Abstract

In this study, the effect of carbon black and graphite filler on the crack initiation and fracture parameters of fly ash geopolymer mortar is investigated. The carbon black was added in the amount of 0.5 and 1.0% and graphite powder in the amount of 5 and 10% relative to the fly ash mass. The reference mixture without any filler was also prepared. The fracture characteristics were determined based on the results of the three-point bending test of prismatic specimens provided with an initial central edge notch. The fracture experiments were conducted at the age of 48 days. The vertical force (F), the displacement measured in the middle of the span length (d), and the crack mouth opening displacement (CMOD) were continuously recorded during the test. The records of fracture tests were subsequently evaluated using the effective crack model, work-of-fracture method, and double-K fracture model. The addition of both fine fillers led to a decrease in monitored mechanical fracture parameters in comparison with reference mortar.

Highlights

The incorporation of novel additives and functional fillers into cement-based composites has been frequently studied in recent decades and especially materials with increased electrical conductivity represent a potential for advanced smart applications
The selected mechanical fracture characteristics of geopolymer mortars modified by graphite powder or carbon black as fine conductive fillers obtained by the above-mentioned fracture models are introduced in figures 1 and 2
While the addition of graphite in an amount of 5% caused an increase of compressive strength of about 24%, on the contrary, the addition of 10% of graphite powder caused a decrease of compressive strength of about 42%

Summary

Introduction

The incorporation of novel additives and functional fillers into cement-based composites has been frequently studied in recent decades and especially materials with increased electrical conductivity represent a potential for advanced smart applications. Apart from favourable mechanical and durability performance, research of their electrical properties has shown that increased availability of mobile hydrated cations in the pores of the geopolymeric structure contributes to improved piezoelectric behaviour in comparison to cementitious binders [6, 7]. This phenomenon makes alkaline activated matrix a promising material for the above mentioned self-sensing structural components.

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Conclusion