Study of Hydration and Microstructure of Mortar Containing Coral Sand Powder Blended with SCMs.

Xingxing Li,Ying Ma,Xiaodong Shen,Ya Zhong,Yuwei Li

doi:10.3390/ma13194248

Abstract

The utilization of coral waste is an economical way of using concrete in coastal and offshore constructions. Coral waste with more than 96% CaCO3 can be ground to fines and combined with supplementary cementitious materials (SCMs) such as fly ash, silica fume, granulated blast furnace slag in replacing Portland cement to promote the properties of cement concrete. The effects of coral sand powder (CSP) compared to limestone powder (LSP) blended with SCMs on hydration and microstructure of mortar were investigated. The result shows CSP has higher activity than LSP when participating in the chemical reaction. The chemical effect among CSP, SCMs, and ordinary Portland cement (OPC) results in the appearance of the third hydration peak, facilitating the production of carboaluminate. CSP-SCMs mortar has smaller interconnected pores on account of the porous character of CSP as well as the filler and chemical effect. The dilution effect of CSP leads to the reduction of compressive strength of OPC-CSP and OPC-CSP-SCMs mortars. The synergic effects of CSP with slag and silica fume facilitate the development of compressive strength and lead to a compacted isolation and transfer zone (ITZ) in mortar.

Highlights

The development of oceanic economy accelerates oceanic constructions in the modern marine industry
We aim to reveal the synergic effect between coral sand powder and supplementary cementitious materials (SCMs) in Portland cement
The initial peak is related to the dissolution of cement and the hydration of C3 A with water, calcium, and sulfate ions to form ettringite [27,28]

Summary

Introduction

The development of oceanic economy accelerates oceanic constructions in the modern marine industry. There is a lack of locally available sources of raw materials including cement, aggregate, pure water, and even rebar for oceanic construction [1]. It requires ships and longer transportation time to transport raw materials to marine engineering from other places. It is expensive and difficult for coastal and offshore construction to use conventional construction materials. In oceanic construction and engineering, the deposits of coralline algae and debris of marine creatures are produced during dredging, which is regarded as solid waste material to occupy land and island space [2]. Research results show that coral concrete has lower compressive strength, higher porosity, larger shrinkage, and poor corrosion resistance compared to conventional cement concrete [5,6,7,9,10,11,12]

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