Effect of Mill-Rejected Granular Cement Grains on Healing Concrete Cracks.

Feseha Sahile Asrat,Tewodros Tekeste Ghebrab

doi:10.3390/ma13040840

Feseha Sahile Asrat, Tewodros Tekeste Ghebrab

Open Access

https://doi.org/10.3390/ma13040840

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Abstract

The effect of mill-rejected granular cement (MRGC) on enabling concrete to autogenously heal its cracks was investigated. The crack-healing efficiency of concrete containing 5%, 10%, 15%, and 20% wt. of MRGC as a replacement for natural fine aggregate was investigated at the age of 28 days. Concrete specimens were induced with artificial cracks and placed in water or air at 20 ± 2 °C to cure and heal the cracks for an additional 28 days. Compressive, flexural, and tensile strengths and water permeability tests were carried out to evaluate crack-healing by evaluating the strength to regain and the reduction in water permeability of concrete. For the air-cured specimens, the gain in compressive strength was between 45% and 79%, the flexural strength was between 74% and 87%, and the tensile strength was between 75% and 84% of the reference specimens for the MRGC content was between 0% and 20%, respectively. For the water-cured specimens, the gain in compressive strength was between 54% and 92%, the flexural strength was between 76% and 94%, the tensile strength was between 83% and 96% of the reference specimens for the MRGC content between 0% and 20%. The water permeability coefficients of the concrete specimens cured in water after cracking decreased by one order of magnitude, while those of the specimens cured in the air increased by the same order of magnitude. The crack-healing efficiency of concrete could be enhanced by increasing the MRGC content of concrete and hydration water.

Highlights

Cement concrete is a man-made composite rock composed of coarse aggregate, fine aggregate, and cement paste
The results indicate that the workability of concrete decreases with the increase in mill-rejected granular cement (MRGC) content
The following conclusions could be made based on the results from the experimental study on the crack-healing effect of mill-rejected granular cement when used as a partial replacement for a fine aggregate

Summary

Introduction

Cement concrete is a man-made composite rock composed of coarse aggregate, fine aggregate, and cement paste. The conventional cement concrete referred to as concrete uses ordinary Portland cement (OPC) paste to bind the aggregates and fill the voids between them. Cement paste plays a vital role in the properties and performance of concrete. When OPC is mixed with water, a chemical reaction (hydration) takes place and gives off various products. Calcium silicate hydrate (C-S-H) is a predominant cement hydration product responsible for the cementitious property of cement paste. The strength of concrete could be defined as the bond strength between the C-S-H gel and the aggregates

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