Cement-stabilized recycled aggregate base course under coupled wet-dry cycles and repeated loading

Abstract

Long term performance is a major concern when recycled materials are incorporated in geotechnical and pavement applications. The current study evaluates the effects of combined wet-dry cycles and repeated mechanical loading on a cement-stabilized base course material made from recycled crushed concrete aggregate (80% by weight) and cement. The experimental program is divided into three phases, each consisting of mechanical loading on two types of specimens: (i) samples which were first exposed to wet and dry cycles in accordance with ASTM D559 procedure, and (ii) samples without prior exposure to wet and dry cycles. Phase I experiments involved monotonic loading tests under compression and flexure to evaluate the strength properties. In Phase II, a total of 108 cylindrical specimens were tested in cyclic compressive loading using a sinusoidal waveform up to 20, 200, 2000, 20000, 200000, and 2000000 cycles at three different stress ratios (0.5, 0.7 and 0.9). The residual compressive strengths and the accumulated plastic deformations were determined at the end of each cyclic regime. Phase III included a flexural fatigue testing program on 39 beam specimens. It was found that the specimens subjected to wet-dry cycles suffered significantly higher damage in terms of plastic deformation, loss of residual strength, and degradation of flexural fatigue strength compared to specimens not exposed to wet-dry cycles. These are important considerations in highway reconstruction projects in which recycled aggregates are considered as alternative materials for pavement foundations.