Watertightness, cracking resistance, and self-healing of asphalt concrete used as a water barrier in dams

The coefficient of permeability of hydraulic asphalt concrete is in the range [10.sup.-8] -[10.sup.-10] cm/s. Laboratory test results show that triaxial specimens in axial compression can undergo axial strains up to 18% without any significant increase in permeability until approaching the compressive strength. For temperatures between 5 and 20 °C and strain rates between 2 x [10.sup.-3] %/s and 5 x [10.sup.-3] %/s, conventional hydraulic asphalt concrete can tolerate 1%-3% tensile strains before cracking in direct tension tests and strains up to 3%-4% in bending. At 20 °C the tensile and bending strains at cracking are 2-4 times higher than those at 0 °C, and at -20 °C they are approximately 0.2% and 0.8%, respectively. Asphalt concrete possesses pronounced crack self-healing properties. In the experiments, the crack leakage rate dropped 1-4 orders of magnitude within a few hours and the cracked specimens regained 55% of the intact tensile strength after only 1 day of self-healing. In summary, the comprehensive series of laboratory tests documents that asphalt concrete has characteristics that make the material extremely well suited for use in impervious barriers in dams, and the test results reported herein can be of great use in barrier design.