Economical Mixtures to Reduce Both Thermal and Autogenous Shrinkage Contributions to Early-Age Cracking

To be submitted to ACI Materials Journa

Accepted by Cement and Concrete Composites (2007). X-Ray Absorption Studies of Drying of Cementitious Tile Adhesive Mortars Abstract

X-ray absorption measurements have been applied to studying film formation at the exposed surface during the drying of cementitious tile adhesive mortars as a function of ingredients and mixture proportions. Preliminary observations suggested that in addition to a drying front, concurrently, a densification front is observed proceeding from the exterior of the specimens inward. Due to the extremely high viscosity of the pore “solution ” in these mortars, an analysis based on Stokes equation actually suggests that some of the smaller cement particles will be “carried ” along with the drying pore solution to the top surface of the specimen where they are sequentially deposited. To verify this hypothesis, further experiments were conducted using either a coarse cement or a fine limestone as a total replacement for the commonly used cement. The x-ray absorption results are further supported by concurrent mass loss measurements on equivalent specimens for each experiment and by particle size distribution analysis of the final dried limestone/silica sand system as a function of depth