A Study on the Effects of Plastic Shrinkage Cracking of Shotcrete Mixes Applied over a Dry Clay Base While Exposed to the Sun and Wind

Abstract

Thin concrete shells used as concrete liners over dry clay dikes suffer from plastic shrinkage cracking for two main reasons: the dry clay base absorbs some of the water in the concrete from below, and high heat coupled with low humidity and wind evaporate some of the water in the concrete from above. This project has the main objective of testing and determining which of three different shotcrete mixes generate the least amount of plastic shrinkage cracking when applied over a dry clay base while exposed to the sun and wind. A high w/c ratio was used to force plastic shrinkage cracking to form. Besides the control mix, a mix with polypropylene reinforcing fibers and another mix with fly ash partially substituting the Portland cement were used. The clay base in this experiment simulates a clay dike that will have a shotcrete liner applied over it to mitigate erosion and flora growth. Key Terms - Fiber Reinforced Concrete, Fly Ash, Plastic Shrinkage Cracking, Shotcrete.