Pre-microcracking of cement-treated bases to reduce reflective cracks on asphalt pavements: A comprehensive review

Shrinkage-induced cracking in cement-treated base (CTB) contributes to reflective cracks in semi-rigid pavement. Potential solutions include using low-shrinkage CTB materials with enhanced cracking resistance or implementing pre-microcracking to mitigate shrinkage. This paper provides a comprehensive review of pre-microcracking methods, including laboratory- and field-based techniques, approaches for evaluating pre-microcracking severity, and their effects on CTB mechanical properties, self-healing capability, shrinkage behavior, crack resistance, and reflective cracking in asphalt pavements. Four pre-microcracking methods have been identified in the laboratory, including compression, vibration, vibro-compression, and impaction, while vibratory rolling is commonly employed in the pavement field. Existing studies suggest that pre-microcracking should be conducted after two days of curing to reduce the CTB modulus of elasticity by approximately 40%. The damage rate due to pre-microcracking had a significant impact on strength recovery, whereas its timing strongly affected the density of induced microcracks. The pre-microcracking mechanism by vibration and the self-healing capability of CTB after pre-microcracking are explored. More importantly, pre-microcracking has been demonstrated to mitigate shrinkage effects and enhance CTB cracking resistance. Furthermore, this review highlights the potential for primary research to improve the effectiveness of pre-microcracking solutions, such as determining optimal strength thresholds for pre-microcracking and evaluating the feasibility of pre-microcracking in CTB incorporating waste materials that could help reduce shrinkage, improve cracking resistance, and facilitate self-healing mechanisms.