Causes and controls of cracking at bridge deck overlay with very-early strength latex-modified concrete

• VES-LMC has a high risk of thermal cracking in early age.
• Cracking control methods for VES-LMC were suggested.
• A verification program of field application was performed.

Very-early strength latex-modified concrete (hereafter, VES-LMC) was developed by focusing on workability and strength development for early opening to the traffic after three hours of concrete placement. This study was designed to analyze the causes of map and transverse cracking in VES-LMC and to provide control methods for minimizing the occurrence of cracks at a field in Korea. The results are as follow:The map cracks of bridge deck overlays with VES-LMC were caused by initial plastic shrinkage cracking within a few hours after placement, by improper and delayed curing (use of curing compound that was delayed until after tining), and were propagated into visible wider cracks within a week. It was also concluded that the property of VES-LMC with minimal bleed accelerated these plastic shrinkage cracks. This was verified by a nomograph relating air temperature, relative humidity, concrete temperature, and wind speed to evaporation rate. To prevent map cracking of the bridge deck overlay with VES-LMC, the recommendations are to apply curing compound as soon as possible after placement and before tining concrete, and reapply curing compound after tining. The prevention methods should focus on VES-LMC material properties affecting the susceptibility of a concrete overlay to prevent transverse cracking. Recommendations on VES-LMC material properties to reduce cracking included the following: as low early strength concrete as possible; low amount of VES cement; low hydration temperature; minimum cement paste volumes and free shrinkage. A verification program of field application was performed in order to prove the effectiveness of prevention methods of map cracking and transverse cracking. The proposed preventions against map and transverse cracking were verified because no cracks occurred until 3 months after overlay placement.