| Asphalt concrete core wall is the impervious body of earth rock dam, which is usually paved by layers, and the layer thickness is about 25cm.The thickness of asphalt concrete core mall is generally between 0.5m and 1.2m. The core wall joint surface is always the focus of attention. and it is also regarded as the weak part of impervious body. During the construction process. due to the objective factors of temperature, rainfall,coring and something like that, the remperature of the core wall will decrease,which is below the standard requirements of 70℃,and the joint surface must be heated to continue the construction; Owing to the viscidity of asphalt material, vibration grinding wheel、 will be stained with a part of hot material. Nowadays,the engineering circles usually use the method of diesel spraying to prevent sticking, but diesel is organic solvent, which will pollute the core level and even affect the bonding between layers.and the cost is relatively high. Experimental research shows that sprinkling water to core levels can significantly improve the anti-sticking and has no pollution. Therefore, it is necessary to study how to ensure the quality of asphalt concrete core wall with diferent construction factors.This paper is based on the existing research experience and research results of the darm asphalt concrete core wall engineering Zhong Ye. and used the equipment of Xi’an University of technology impervious research institution to simulate the level temperatures of 130℃.40℃、20℃ and -3.5℃ and the level temperatures of 80℃ and 70℃C, 60℃C and 50 ℃with the method of water spraying, which formed 8 different working conditions.The gas permeability, splitting and bending tests were conducted to study its effect on core wall innerkayer bonding quality. Several conclusions are drawn as follows:1. When the temperature was -3.5℃ the layer was not heated and only made the 160℃(?). asphalt mixture above stand for 30min, and the seepage resistance and mechanical(?)perties of the joint surface did not change much. The layers were in good condition.2. During the siimulation of the construction process of the core wall, after spraying water(?) the surface, the compaction machine almost hardly touched the asphalt mixture, and the(?)-adhesion effect was ovious. The 160℃ hot material above was stand for 30min,and the seepage resistance and mechanical properties of the joint surface were not much different than that of the non-bonding surface. The layers were in good condition.3. During the process of simulating the construction of the core wall, the layer was not heated and only made the 160℃ hot asphalt mixture above stand for 30min, and the bending strength and the bending strain of the asphalt concrete were less than that of the non joint surface; The combination of strength and strain decreased with the decrease of temperature level, and when the temperature was 40℃, strength and strain decreased by about 10%.It seemed small ,and the temperature can be regarded as the minimum allowed temperature without heating level.4. During the process of simulating the core wall construction, the bending strength and bending strain of the asphalt concrete on the joint surface was less than that of the non-joint surface, which met the quality requirements; A combination of strength and strain of the surface will decrease with the decrease of temperature level, and when the temperature is 75℃,strength decreased by about 5%, strain decreased by about 10%. The range was small, and the temperature can be regarded as the minimum allowed temperature without heating level. The measure does not affect the bonding quality of the core wall, and can be used in similar projects.5. Conclusions of this paper were drawn from the simulation of the construction process of the core wall under the conditions of the asphalt of grade 70 and oilstone ratio of 6.9. In the actual projects, the large volume of the asphalt mixture and its slow cooling make the heat preservation effect better, or using higher grade of asphalt and greater aggregate ratio will make the level temperature allowed lower without heating and better engineering effect. |
