Analysis of Drying Processes in Mortars with and without Shrinkage Reducing Admixtures

摘要

Shrinkage Reducing Admixtures (SRAs) are increasingly being used in concrete as a method to minimize shrinkage and restrained shrinkage cracking. SRAs reduce shrinkage by decreasing the surface tension of the pore solution; however, SRAs also impact the fluid viscosity, contact angle and density. Consequently, the absorption and desorption processes of cementitious systems containing SRA are altered. This paper describes experimental measurements of drying in cementitious mortar samples with and without SRAs, focusing on three components. First, solution properties (surface tension, viscosity, and contact angle) were measured at different temperatures. Second, the vapor desorption curves were measured and the non-linear moisture diffusion coefficient was quantified at different relative humidity (degrees of saturation). Third, neutron radiography measurements were performed to visualize and quantify the effect of the presence of SRA in solution on the moisture profiles and drying front generated during the early stages of the drying process. The results will be discussed in terms of theoretical observations in an effort to place the modeling of moisture and shrinkage gradients in concrete on a more fundamental footing.