This study focuses on the issue of hot mix asphalt patch repairs, the performance of which is greatly reduced by repair edge disintegration. This is caused by low interface temperatures which result in poor repair bonding between fill material and host pavement. Twenty-four pothole repairs, 45 mm in depth, comprising 12 static and 12 dynamic repairs heated for 10 min 15 s and 21 min 49 s, respectively have been investigated. Dynamic heating has been completed using an experimental infrared heater. Temperatures were measured at 11 locations on the repair interfaces during the pouring and compaction of the fill mix. Volumetric of asphalt mixtures were also investigated. The results demonstrated that for static repairs, the lowest maximum temperatures were located at corners and on vertical repair boundaries. It was found that high thermal contact resistance in these interfaces dramatically affect the temperature levels. However, the figures improved in dynamically heated repairs. Comparing dynamically heated repairs of 10 min 15 s and 21 min 49 s with static repairs, showed average corner temperatures increase 10.85-24.45°C and 29.51-36.73°C, respectively, with accompanying increases in vertical interface temperatures 34.97°C and 46.41°C, respectively. ARTICLE HISTORY

The performance of hot-mix asphalt patch repair is greatly reduced due to inferior compaction at the interface. It is known that the faster loss of temperature at the interface is one of the primary reasons for inferior compaction. A novel controlled pothole repair system (CPRS) has been developed as part of this study. The CPRS uses infrared heating technology with enhanced features compared to many existing infrared systems. In parallel, a three-dimensional finite-element thermal model capable of modelling the loss of temperature during the patch repair process has been developed. The first part of the paper presents the functionality of CPRS, including experimental results to demonstrate various features of the system. In the second part, the numerical results are compared against experimentally measured values from a patch repair in a controlled laboratory condition. The tests are done to measure the influence of no preheating and preheating of the existing surface on the temperature loss. The results showed more than 80% agreement between simulation and actual measurements. It is also shown that preheating of the existing surface can significantly reduce temperature loss at the interface, thus allowing more time for repair and the possibility of achieving better compaction.

Traditional repair methods tend to suffer from inadequate net interface heating because the combined effect of placing hot fill mix in a cold, old pavement leads to inadequate net temperature levels. The outcome of this is low durability and limited life. In contrast, the outcome of placing hot mix in a controlled, preheated host pavement is substantial increased working life. To understand repair heating, this study ran heat transfer finite-element models for the cases of (1) hot mix asphalt (HMA) placed in an ambient temperature pothole, (2) the heated pothole recess, and (3) HMA placed in the preheated pothole recess. The air-pavement-heater system model comprises a host pavement with two pothole repairs or, in the case of the second thermal model, with one empty pothole excavation, and an infrared heating element plate. For calibration purposes, experimental work of simulated repairs undertaken in previous research was used. The air-pavement-heater system setup followed an optimum pothole preheating method also determined in previous research. Thermal models were validated with previous experimental work. It was concluded that the models generate reasonable transient temperature profiles within the dynamically heated pothole excavation, at the interface of the repairs, and inside the host pavement.

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h i g h l i g h t s Thermal segregation is developed in patching in both winter and summer seasons. Long haulage time of HMA progresses thermal segregation. Poor insulation measures of HMA during transportation raises thermal segregation.