Laboratory investigations of controlled low-strength material

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Du, Lianxiang

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This report presents the results of experimental studies on the properties of controlled low-strength material (CLSM) and the corresponding test methods for evaluating the characteristics of this material. A wide range of CLSM mixtures were included in this study. Fresh properties of CLSM were evaluated. The use of bottom ash, foundry sand, and high-carbon fly ash was found to increase water demand to achieve the desired flow in CLSM. Bottom ash tended to increase bleeding, whereas foundry sand decreased bleeding tendencies. Two methods were used to evaluate the setting and hardening of fresh CLSM mixtures, and their mechanisms were evaluated. New methods were developed to measure the segregation and subsidence of fresh CLSM mixtures. The hardened properties of CLSM, including compressive strength, excavatability, California Bearing Ratio, resilient modulus, water permeability, triaxial shear strength, and drying shrinkage were studied. Predictive models were proposed for the strength development of CLSM mixtures. Modifications to ASTM D 4832 were proposed to make it a more appropriate method for measuring of the compressive strength of CLSM. The effects of alternative capping materials, including neoprene pads, gypsum and sulfur, were studied. In addition, factors affecting the strength gain of CLSM mixtures, including curing temperature and humidity, were examined. The resistance of CLSM mixtures to freezing and thawing was evaluated using modified version of ASTM D 560. Higher air contents and compressive strengths were found to improve the durability of CLSM mixtures exposed to freezing-and-thawing cycles. Although CLSM was found less corrosive than soil, the potential formation of galvanic cells may be a concern to pipeline engineers. Factors influencing the corrosion behaviors of ductile-iron samples were identified. For coupled and uncoupled corrosion conditions, different contributing factors and mechanisms were identified.



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