Physico-mechanical characteristics and durability of calcium aluminate blended cement subject to different aggressive media

Abstract

Three mixes were prepared from calcium aluminate cement (CAC) and 20 mass% water-cooled (WCS) slag or air-cooled slag (ACS). The pastes were prepared with the required water of standard consistency, cured under tap water until time of testing (1, 3, 7 and 28days). The durability of calcium aluminate blended cement was investigated by immersing the samples under tap water for 7days (zero time), and then immersed in 5% sodium chloride, 5% magnesium sulphate and 5% ammonium sulphate as aggressive media. Compressive strength, bulk density and apparent porosity were measured. X-ray diffraction analysis and scanning electron microscopy were studied to reveal their mineralogical and microstructural features. Compressive strength of neat CAC pastes are lower than those of CAC–WCS and CAC–ACS blends. Compressive strength of CAC pastes immersed in 5% NaCl, 5% MgSO4 or 5% (NH4)2SO4 increases with curing time up to 90days and then shows a slightly decrease up to 120days immersion time. The presence of Cl− or SO42− ions activates the hydration rate of CAC, CAC–WCS and CAC–ACS. The SEM micrographs of CAC–WCS and CAC–WCS indicate the presence of the thin flaky-plate like morphology of C2ASH8 and thin fibrous particles of C–S–H I,II, which reflects closed and compact texture.