PURPOSES : The purpose of this study is to verify the effectiveness of the developed ultra-thin-continuously reinforced concrete partition (UT-CRCP) overlay method through a comparative analysis of the early-behavior of the UT-CRCP with a 100 mm cutting overlay of the existing JPCP. METHODS : This study aims to minimize the vulnerability of the existing JPCP (joint section behavior) by overlaying the continuous reinforcement form to constrain joint behavior. For this purpose, the early-behavior of the JPCP section was measured and the early-behavior of the UT-CRCP section was compared with that of the cutting overlay of the same section. The testbed was constructed for comparative analysis of the two types of pavements and the early behavior was measured using the pure environmental loads, i.e., situations where there was no traffic load. For the UT-CRCP, which is a comparative test group, UT-CRCP was constructed approximately one year after the JPCP was constructed by milling the top of the existing JPCP by 100 mm. RESULTS : 1) UT-CRCP was shown to effectively reduce the amount of crack width change on the surface by 17 %, compared to JPCP, by placing reinforcement inside the pavement. 2) The restricting effect of the UT-CRCP was analyzed by comparing the strain generated by the cross-section depth for the two pavement types. As a result, the restricting rate by depth (20, 80, 120, and 280 mm) was 68.4 %, 80.2 %, 89.2 %, and 26.7 %, respectively. 3) We reviewed the comprehensive gauge restricting rate at depths of 80 mm and 120 mm (80.2 % and 89.2 %, respectively) and the absolute value of behavior that is located at the ±20 mm of the interface of JPCP and UT-CRCP. Thus, it was possible to estimate that both layers of pavements exhibit the same behavior (tied) at the interface between the two pavement layers. CONCLUSIONS : In this study, the early behavior of the BCO concept UT-CRCP overlay technique was analyzed and quantitatively presented to overcome the limitations of JPCP with relatively weak point behavior and to increase the commonality of aged concrete pavement to the performance of the new pavement.

In Korea, concrete pavements were first applied to highways in 1981 and as a result of continued increase in length over the past years, 2,592 km of concrete pavement network is currently in service, of which 1,399 km(54%) of concrete pavements is 10 years or older, and 233km(9%) is 20 years or older. The length of concrete pavement sections nationwide has been steadily on the rise every year (EXTRI, 2017). Approximately 54% of current concrete pavement highway network will reach the service life limit in 2025 which means around 660 billion won is needed for future pavement repair project (EXTRI, 2017). Given that concrete pavements beyond design life still have a remaining service life, it is economically advantageous to repair them before reconstruction. Asphalt overlays are a major repair method for older concrete pavements. Depending on the concrete pavement condition, thickness and mixture of asphalt overlays are determined. Service life of asphalt overlays varies by the presence, time and size of cracks in existing concrete pavements and reflecting crack at joints. Temperature change of concrete pavement is among the major reaction parameters of reflecting crack. Reflecting crack develops when asphalt bottom-up cracking by longitudinal shrinkage and expansion due to temperature change of the concrete base layer, top-down cracking by temperature difference between top and bottom of concrete, and shear stress by traffic loading are combined (Baek, 2010). Crack and joint behaviors of concrete pavement vary between the base layer and the concrete surface of composite pavement system, and different conductivity by mixture and thickness of asphalt overlay leads to temperature change of concrete base course. This study measured temperatures of each layer of diverse composite pavements in place on site and analyzed differences in temperature change of concrete base layer depending on mixture and thickness of asphalt overlays. Overlay thickness parameters were 5cm and 10cm, two values most widely used, while mixture parameters were SMA and porous asphalt. Based on temperature change of concrete surface, this study also evaluated the difference of temperature change in concrete base layer with an asphalt overlay on top. Findings from this study are expected to be utilized for studies on mechanism and modeling of reflecting crack in old concrete pavements with asphalt overlays.

PURPOSES : So far, aged cement concrete pavement on express highways has been rehabilitated mainly with asphalt concrete inlay. However, potholes were the major problem, and they shortened the life of the inlay mainly owing to the poor drainage of water once it infiltrated the interface of the concrete and asphalt. The purpose of this study is to compare the performance and economic efficiency of asphalt overlay and inlayMETHODS: Overlay and inlay were compared through accelerated pavement testing, and a life-cycle cost analysis was conducted in this study using the CA4PRS program.RESULTS and CONCLUSIONS : It was found from accelerated pavement testing that the overlay exhibited reflective crack resistance that was more than twice as effective as that of inlay. The total cost (construction cost + user cost) within the analysis period (20 years) of the overlay was 37% lower than that of the inlay.

More than sixty percent of highways in Korea were constructed with concrete pavement to carry the heavy traffic loads due to the economic development of this country. The service life of some pavements are close to the end, therefore, they requires the maintenances, rehabilitations and reconstructions to improve their structural performances.According to the similarity of material properties to the concrete pavement, bonded concrete overlay isa good rehabilitation technique used steadily in Korea. However, it is recently reported that the bonded concrete overlays in some highways expose the early distresses and it is assumed that the poor bonding is a cause of this problem. Additionally, the poor bonding of bonded concrete overlay is caused by the bond strength that is less than the bond strength criterion. The pre-investigation of various concrete overlays is conducted in laboratory to determine the possible influence factors reducing the bond strength and it indicates that there are two possible factors affecting the bond strength: the concrete overlay types and the substrate conditions. The study investigates the vulnerable factor between the two factors based on theevaluation of the in-situ bond strength data of bonded concrete overlay gathered from some highways in Korea. The bond strength data is collected from two different application areas: the new constructionand the rehabilitation projects. The new construction and the rehabilitation projects used Latex-modified Concrete (LMC) and Ultra-rapid Hardening Latex-modified concrete (URH-LMC), respectively as the concrete overlay. The evaluation of in-situ bond strength is to determine the percentage of unacceptable bond strength in each projectto study the effect of different types of concrete overlay. Moreover, the percentage of bonding failure modes having the bond strengths less than the criterion is also measured to study the effect of substrate condition.As a result, substrate condition is the vulnerable factor affecting the poor bonding and causing the early distresses in bonded concrete overlay.