EVALUATION OF EARLY-AGE JOINT MOVEMENTS OF JPCP AT FIELD

摘要

Concrete pavement receives restrained stresses from early curing and which is restricted or is extended by external circumstance such as gradient of temperature and moisture. These behavior of JPCP(Jointed Plain Concrete Pavement) increase its binding power and tend to induce failure of joints, and which consider the mainly influence of early-age joint opening of concrete slab. In this research, the early-age joint movements and behavior of dowel-bar at JPCP were studied through field tests. The field tests were carried out for 5 days just after concrete placement, for 1 day after 52 and 1 day after 72 days on Chung-Ang Expressway new construction site in Dan-yang on the 28th and 29th of May 2001. The joint movements and dowel-bar behavior were measured by demec gauge, clip gauge, and strain gauge. The results could be summarized as follows; The tensile and compressive behavior of dowel bars for the first 3 days increased rapidly in early-age, and then decreased gradually after the first 3 days period. It was, also, found that dowel-bars behaved under the influence of temperature and moisture to which they were exposed. The joints movement variation with temperature changes as discovered in this research presented fairly good conformity with the prediction from Darter's formula. The results of regression analysis for the data measured during early 5 days showed that the joints of No.4, No.5, No.6, No.10, No.13, and No.15 could be considered as a moving joint. From data analysis on July 20, the joints of No.2, No.9, and No. 10 showed the significant correlations from the minus value of coefficient of regression, which usually present lower C-values. As a result of regression data on August 8, joint movements occurred at all joints. Joint freezing and closure could be judged from the regression analysis using joint opening and total temperature measured at field tests.