The Effect of Curing Duration on Restrained Shrinkage Cracking of Concrete Containing Macro Polymeric Fibers

The positive influence of longer duration of wet curing in improving the mechanical and durability properties of concrete is fairly well established. However, it is increasingly becoming apparent that longer duration of wet curing, unfavorably affects the drying shrinkage characteristics of concrete, resulting in both increased amount of shrinkage and also increased cracking potential under restrained conditions. Various types of fibers have been developed and used to enhance the durability of concrete structures by controlling the restrained shrinkage cracking. However, the influence of longer duration of wet curing on the age at cracking and crack characteristics of concrete containing macro polymeric fibers has not been previously determined. In this research, the effects of three different curing durations on strength characteristics and free and restrained drying shrinkage performance of mixes with and without macro polymeric fibers were studied. The results show that drying shrinkage and cracking potential of the control mixes increased with longer duration of wet curing, confirming the trend reported by recent literature. Interestingly the mixes containing fibers also showed the same trend and both the amount of free shrinkage and the restrained shrinkage potential increased with increased duration of wet curing. With regards to crack widths, the results show that with longer wet curing, the width of the single crack for the control mixes increased significantly while the cumulative width of the multiple cracks of the mixes with polymeric fibers increased only modestly.