Potential of NaCl solution as mixing water in siliceous minerals modified calcium aluminate cement

Abstract

Given the advantages of calcium aluminate cement (CAC) in specific marine engineering, selecting materials directly from the sea when mixing CAC can cut down the construction costs and reduce the ecological pollution to the sea. However, the investigation of using seawater as the mixing water of CAC is still trekking with difficult on account of the strength reduction. In this regard, this paper evaluated the possibility of using NaCl solution as mixing water and diatomite as SCMs to modify CAC. Silica fume (SF) and the corrosion by immersion in NaCl solution is employed as the reference. The strength, mass, and length changes of CAC mortars at both 20 °C and 40 °C were tested, and the phase assemblages and morphology were characterized by XRD, TG-DSC and SEM. Results reveal that using NaCl solution as the mixing water is beneficial to the later strength development of CAC, which promotes the formation of C2ASH8 in CAC pastes and exhibits no strength retraction even at 40 °C. The strength of the diatomite/SF modified CAC mortars mixing with NaCl solution is all higher than that immersed in NaCl solution. By contrast, the cooperation effect of diatomite and NaCl solution can significantly increase the strength of CAC, especially at 20 °C. And diatomite favors strength development of CAC mortars, while SF contributes to a better mass and length stability.