Experimental Study on the Protection of an Asphalt Coating to Reinforcement in Magnesium Oxychloride Cement Concrete

Abstract

To mitigate the corrosion of steel bar in magnesium oxychloride cement concrete (MOCC), an asphalt coating is used for protection. According to the service environment in the Salt Lake area of western Qinghai, China, a solution immersion test on MOCC was performed. The test results showed that, after soaking for 2160 days, the corrosion current density icorr was 7.88 µA/cm2, and RC was 113.51 Ω for group A and icorr is 0.08 µA/cm2 and RC is 842.57 Ω for group B. The time parameters for groups A and B fell in the high-frequency range of 103–105 Hz and low-frequency range of 10−2 to 10−1 Hz. The relative dynamic moduli of the elasticity evaluation parameters ω1 and ω2 were 0.942 and 0.959 and 0.946 and 0.962 for groups A and B, respectively, at 2160 days, exhibiting a downward trend on the whole. Fourier transform infrared spectroscopy and microscopic testing revealed that the corrosion of the chloride solution on asphalt was mainly the corrosion of chloride in the interior of the asphalt and that the invaded salt provided a channel for the water solution to invade into the interior.

Prediction of Water Resistance of Magnesium Oxychloride Cement Concrete Based upon Hybrid-BP Neural Network

“…However, its hydration products, 5Mg(OH) 2 •MgCl 2 •8H 2 O (referred to as phase 5) and 3Mg(OH) 2• MgCl 2 •8H 2 O (phase 3), are prone to hydrolysis in moist environments, and generate Mg(OH) 2 and MgCl 2 , which leads to a loose cement structure and increased porosity that decrease its strength [3,4]. At the same time, it also creates conditions that allow CO 2 to enter the material, where CO 2 reacts with Mg(OH) 2 to produce magnesium chlorocarbonate (2MgCO 3 •Mg(OH) 2 •MgCl 2 •6H 2 O) that causes MOCC to warp and deform [5,6]. Therefore, MOCC's poor water resistance limits its widespread use and is currently an urgent problem that needs to be solved.…”