Abstract
Chloride transport in different types of high alumina cement (HAC) mortar was investigated in this study. Three HAC cement types were used, ranging from 52.0 to 81.1% of aluminum oxides in clinker. For the development of the strength, the setting time of fresh mortar was measured immediately after mixing and the mortar compressive strength was cured in a wet chamber at 25 ± 2°C and then measured at 1–91 days. Simultaneously, to assess the rate of chloride transport in terms of diffusivity, the chloride profile was performed by an exposure test in this study, which was supported by further experimentation including an examination of the pore structure, chloride binding, and chemical composition (X-ray diffraction) analysis. As a result, it was found that an increase in the Al2O3 content in the HAC clinker resulted in an increase in the diffusion coefficient and concentration of surface chloride due to increased binding of chloride. However, types of HAC did not affect the pore distribution in the cement matrix, except for macro pores.
Highlights
High alumina cement (HAC), mainly consisting of aluminum oxide (Al2O3) from about 50 to 85% in cement clinker, could be often used for a special application, due to both high resistance to aggressive chemical ions and rapid development of strength within 24 hours [1,2,3,4]
The ionic transport in different types of HAC mortar was investigated by the chloride profile, which was supported by further experimentation including an examination of the pores structure, chloride binding capacity, and chemical microscopic analysis (X-ray diffraction analysis)
Detailed experimental results and conclusion derived from the study are given as follows: (1) An increase in the Al2O3 in the HAC clinker resulted in an increase in the setting time, and, the gap between initial and final sets was increased, due to increased CA2 formation
Summary
High alumina cement (HAC), mainly consisting of aluminum oxide (Al2O3) from about 50 to 85% in cement clinker, could be often used for a special application, due to both high resistance to aggressive chemical ions (i.e., sewer concrete) and rapid development of strength within 24 hours [1,2,3,4]. It is intuitively supported that the high portion of aluminum oxide in HAC, which is related to formation of CA-type hydration, for example, C3A, to remove free chlorides from the concrete pore solution, might be preferred to enhance resistance to chloride-induced corrosion of steel in concrete [10]. The corrosion resistance of HAC in terms of critical chloride concentration for the onset of corrosion was increased up to 2.4%, whilst OPC concrete ranged from 0.2% to 1.0% for the chloride threshold [10] When it comes to the corrosion-free service life of structures, the rate of chloride transport in HAC concrete, is of no concern to date. Three different HAC types were used containing 52.0, 67.3, and 81.1% of aluminum oxides in HAC clinker
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