Modeling heat and moisture transport in steam-cured mortar: Application to AASHTO Type VI beams

Abstract

During steam curing of concrete, temperature and moisture gradients are developed, which are difficult to measure experimentally and can adversely affect the durability of concrete. In this research, a model of cement hydration coupled to moisture and heat transport was used to simulate the process of steam curing of mortars with water-to-cement (w/c) ratios by mass of 0.30 and 0.45, considering natural convection boundary conditions in mortar and concrete specimens of AASHTO Type VI beams. The primary variables of the model were moisture content, temperature, and degree of hydration. Moisture content profiles of mortar specimens (40 mm in diameter and 50 mm in height) were measured by magnetic resonance imaging. The degree of hydration was obtained by mass-based measurements of loss on ignition to 1000 °C. The results indicate that the model correctly simulates the moisture distribution and degree of hydration in mortar specimens. Application of the model to the steam curing of an AASHTO Type VI beam indicates temperature differences (between the surface and the center) higher than 20 °C during the cooling stage, and internal temperatures higher than 70 °C that may compromise the durability of the concrete.

Seawater as Alkali Activator in Fly Ash Based Geopolymer

“…As a comparison, OPC based mortar was made by mixing cement and water or seawater with a water-cement ratio (w/c) of 0.5 (Figure 4) and paste to sand ratio of 1:2 to form a slurry. The hardened mortar is removed from the mold for a curing process by immersing the entire surface of the sample in water for 28 days to prevent the sample from cracking during the curing process due to an exothermic reaction (Hernández-Bautista, et al, 2017). 3 which confirms that the salt has alkaline compounds which can increase the basicity of the mortar.…”