Performance Study of Aluminum Sulphate and Calcium Bromide Modified Cementitious Repair Mortar

Abstract

Airport runway repair materials often exhibit insufficient frost resistance, leading to repeated repairs. This issue arises because such materials typically depend on high volumes of sulphoaluminate cement (SAC) to achieve rapid hardening, which compromises their frost resistance. Although ordinary portland cement blended with mineral admixtures offers good frost resistance, it suffers from prolonged setting time and low early strength, restricting its application in rapid repairs. This study aims to overcome these limitations by accelerating setting and enhancing early strength while maintaining frost resistance. The effects of a single addition of alkali-free liquid accelerator (LAA) and combining LAA with calcium bromide ( CaBr 2 ) on the properties of repair mortar were investigated. The results show that both additions significantly shorten setting time, reduce flowability, and increase the hydration heat evolution rate as well as early strength. Microstructural analyses (scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, mercury intrusion porosimetry) reveal that the incorporation of LAA and CaBr 2 accelerates the hydration process, optimizes the pore structure, and generates more hydration products. These factors account for the repair mortar’s high mechanical properties and good frost resistance. This study proposes an effective strategy to improve the early strength and freeze–thaw resistance of cement-based repair materials in cold regions.