Simulated shrinkage cracking in the presence of alkali resistant glass fibers

Early-age cracks on concrete surfaces are one of the main routes through which aggressive agents penetrate into the concrete and threaten the long-term durability of structures. A test method capable of simulating early-age shrinkage cracks in 2-D cement paste samples under low-pressure condition is presented. The method is capable of characterizing evaporation parameters in two distinct stages of drying while monitoring sequential formation of shrinkage cracks. Using a gravimetric approach, the mass loss of the specimen is monitored continuously throughout the test as the sample is subjected to low pressure environment. Formation of microcracks are documented simultaneously using digital time lapse photography. The mass loss data is used in conjunction with specimen, size, and thickness to compute the evaporation rate from the surface. These results are used in turn using a diffusion based model to compute the effective moisture diffusivity as a function of fiber dosages. Effects of AR-glass fibers on evaporation parameters and shrinkage cracks are studied. Image analysis results indicate significant effects of fiber on controlling early-age shrinkage cracks.