Developments in the Built Environment (Mar 2024)
Repair interface crack resistance mechanism: A case of magnesium phosphate cement overlay repair cement concrete pavement surface
Abstract
Cement concrete pavements are continuously impacted by environment and vehicle loads, resulting in corner cracking, pockmarked surface and other distresses. It emerges a hot topic: reinforcement and repair. In recent years, magnesium phosphate cement (MPC) has been widely praised as a rapid repair material on cement concrete pavement. In this study, the crack resistance of a composite structure with MPC mortar overlay upon Portland cement concrete was investigated. First of all, the crack mouth opening displacement (CMOD) and double-K fracture parameters for different ratios of the precast notched crack length to height of composite specimen were obtained in the prenotched double-layered three-point bending beam (DLTPB) tests. The results showed that the peak force decreased with the decreasing ligament length. An exponential relationship between the fracture parameters to different ratios of the precast notched crack length to the height was observed. For the non-linear elastic fracture mechanics (non-LEFM) evaluation, MPC mortar overlay was beneficial for the flexural tensile performance and crack resistance of the composite structure. Results showed the agreement between experimental and theoretical CMODs. The crack initiation and propagation in DLTPB test was effectively determined by digital image correlation (DIC) method. It was found that MPC mortar overlay extended the fracture process zone (FPZ) as the crack propagated at the repair interface. The non-LEFM behaviors of composite MPC-concrete specimens were evaluated and capable of obviously similar with traditional cement-based materials. The elastic modulus measured by nano-indentation and the microscopic mechanism analyzed by SEM showed that the complex contact situation did not weaken the interface performance. However, the unique performance advantages of composite structure relied on not only the good performance of the MPC mortar overlay but also the strong bonding at repair interface. The results showed that the excellent interfacial mechanical properties assist to improve the crack resistance and prevent the cracks between concrete and MPC mortar from rapid propagation. It reflected that the MPC mortar overlay can hinder the crack propagation from the cement concrete.
