Intensified Pozzolanic Reaction on Kaolinite Clay-Based Mortar

Yang-Hee Kwon,Juhyuk Moon,Sung-Gul Hong,Sung-Hoon Kang

doi:10.3390/app7050522

Yang-Hee Kwon, Juhyuk Moon + Show 2 more

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https://doi.org/10.3390/app7050522

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Abstract

The objective of this study is to develop and characterize kaolinite clay-based structural mortar. The pozzolanic reaction induced from two mineral additives, i.e., calcium hydroxide and silica fume (SF), and the physical filling effect from SF, were found to be effective on the enhancement of structural properties. Based on several preliminary experiments, 7:3 ratio of kaolinite clay/calcium hydroxide was selected as a basic binder. Then, the amount of SF was chosen as 0%, 7.5%, and 15% of the total binder to consider both the chemical and physical effects. The results showed that compressive strengths of samples with 7.5% and 15% SF are significantly increased by approximately 200% and 350%, respectively, at 28 days compared to the sample without SF. However, based on the results of the sample with 15% SF, it is found that excessive addition of SF causes long-term strength loss, possibly owing to micro cracks. With the careful consideration on this long-term behavior, this suggested new mix design can be further extended to develop sustainable structural materials using natural minerals or waste materials with nonbinding properties.

Highlights

Concrete is one of the most widely used construction materials in the world with a consumption of almost 10 billion tons per year [1]
As a result of extensive research activities focusing on the development of eco-friendly construction materials, several promising alternatives have been proposed for low CO2 -embedded construction materials
The interesting result is that the cumulative hydration heat of SF_15 was only 5% higher than that of SF_7.5, silica fume (SF) content in SF_15 was almost twice than that in SF_7.5. This result reveals that the excessive addition of SF has no chemical effect on the hydration reaction

Summary

Introduction

Concrete is one of the most widely used construction materials in the world with a consumption of almost 10 billion tons per year [1] It has numerous advantages as a structural material, such as convenience for making the shape of a structure, structural soundness, and good durability. As a result of extensive research activities focusing on the development of eco-friendly construction materials, several promising alternatives have been proposed for low CO2 -embedded construction materials These include high-volume fly ash [5,6] or slag [7] concrete, geopolymer concrete [8], and sustainable cement mixtures having CO2 -sequestrated minerals [9], or fillers such as limestone or quartz powder [10,11,12,13]. Along with the environmental and economic benefits as replacements for OPC, these materials have other advantages, such as improving mechanical properties and durability [19]

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