Influence of Calcined Clay Reactivity on the Mechanical Properties and Chloride Diffusion Resistance of Limestone Calcined Clay Cement (LC3) Concrete

Quang Dieu Nguyen,Arnaud Castel,Sumaiya Afroz

doi:10.3390/jmse8050301

Quang Dieu Nguyen, Arnaud Castel + Show 1 more

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https://doi.org/10.3390/jmse8050301

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Abstract

Calcined clay plays an important role in the performance of limestone calcined clay cement (LC3) concrete. In this study, the performance of two different types of calcined clay produced from different calcination processes were investigated in chloride environment. The characteristics of the calcined clays, including mineral composition, chemical composition, particle size distribution, specific surface area and particle morphology, were evaluated. Based on the reactivity of the calcined clays, the compressive strength of concretes after up to 28 days of curing was adopted as the best measure to determine the appropriate replacement levels of Portland cement by LC3 to satisfy standards requirements for concrete in chloride environments. The chloride bulk diffusion test was conducted to investigate the performance of LC3 concretes in comparison with reference Portland cement concrete. Similar chloride diffusion resistance could be achieved by using the two different calcined clays in LC3 concrete. The performance of both LC3 concretes was much better than that of reference concrete. However, the Portland cement substitution rate for each calcined clay was governed by the compressive strength standard requirements.

Highlights

Concrete and other cementitious materials play a decisive role in the global economy and human society
SiO2 constituted around 70wt.% in flash calcined clay whilst it presented at about 48wt.% in rotary kiln calcined clay according to X-ray fluorescence (XRF) analysis
The two calcined clays used in this study present very different reactivity but achieved the same level of chloride diffusion resistance by using appropriate replacement rates, which may be attributed to the similar phase assemblage in the two LC3 concretes

Summary

Introduction

Concrete and other cementitious materials play a decisive role in the global economy and human society. An increasing number of bridges have to be utilised beyond their design life of 50 years, which leads to additional cost to keep these structures serviceable [6]. All of these things result in high cost to society, mostly due to chloride-induced reinforcement corrosion of concrete structures [7]. When the chloride content at the steel depth reaches the so-called chloride threshold, reinforcement is depassivated and the corrosion propagation stage starts leading to a time-dependent steel cross section reduction, expansive corrosion products formation, and subsequently concrete cracking, as well as spalling of marine structures (Figure 1)

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