Research On The Field Investigation And Early-age Damage Causes Of Bilayer Reinforcement CRCP’s Transverse Joints

As China’s highway transportation increasingly shows the characteristics of large-scale,heavy-duty vehicles and large traffic flow,higher requirements are placed on carrying capacity of pavement structure,so bilayer reinforcement CRCP came into being.Based on the National Natural Science Foundation of China and the Science and Technology plan project of Wuhan Urban Construction Committee,the weak links of the bilayer reinforcement CRCP structure,transverse joints including expansion joints and construction joints and the causes of early-age damage of transverse joints were investigated.First of all,systematic field investigation and analysis of bilayer reinforcement CRCP’s transverse joints on test sections were launched.It is found that the early-age damage of bilayer reinforcement CRCP transverse joints accounts for a large proportion,especially expansion joints,and the early-age damage of expansion joints is more serious.According to the statistics of transverse cracks within 20 meters’ range of transverse joints,the average crack spacing at the expansion joints is greater than that at the construction joints.After the traffic is opened,the transverse cracks increase.Secondly,field test of the test section of bilayer reinforcement CRCP’s transverse joints was launched.The test results show that the maximum stress of the reinforcement at the expansion joint is far lower than the standard yield strength of the reinforcement.In the case of no vehicle load,the concrete stress at the transverse construction joints gradually decreases with the deepening of the pavement thickness.The longitudinal reinforcement bears the tensile stress of concrete.With the increase of dynamic vehicle weight,the concrete stress value of slab bottom increases significantly.The amount of concrete stress change caused by vehicle speed is small.And once again,the temperature gradient on both sides of the bilayer reinforcement CRCP transverse joint was determined.Determining the non-linear temperature curve under concrete pavement’s built-in curling by Maturity theory and using the NOLA method to calculate the equivalent temperature gradient,the real temperature gradient and absolute temperature gradient of the panel were obtained.The calculated results show that the temperature gradients on both sides of the joints differ greatly.Finally,according to the simulation model calibrated by the actual test data,the influence of temperature load on the transverse joints of bilayer reinforcement CRCP was analyzed.It was showed that the built-in curling tended to cause uneven warping of the concrete pavement on both sides of the transverse construction joint.The restraint of concrete and longitudinal steel bars can effectively reduce the early-age damage of joint concrete.In the construction of new and old panels,attention should be paid to ensure the uniformity of the construction environment and maintenance cycle of new panels as much as possible.