Development of Cement-asphalt Emulsion Mixture for Thailand Road Rehabilitation

Abstract

The cement has been used as a famous stabilizing agent for the road rehabilitation because of its high strength. However, it could lead to premature cracking on the road caused by the hydration reaction and moving traffic load. The moisture from heavy rain and flooding may bring about the pavement damage as it infiltrates and destroys the bottom layer of pavement. An asphalt emulsion has been a well- known agent for pavement stabilizing as well. It is able to increase the adhesion and waterproofing properties. The combination of the asphalt emulsion and the cement has been improved in various efficiencies of pavement. This research aimed to investigate the results of the mixture of cement and asphalt emulsion which was called the cement- asphalt emulsion as a new stabilizing agent. The objectives of this study were to determine the appropriate ratio between the cement and the asphalt emulsion and to determine the performance of cement- asphalt emulsion (CAE) stabilization. The main materials in this study were 1) the pavement recycling material, 2) the clean sand, 3) the Portland cement type I, and 4) the cationic asphalt emulsion (CSS-1). The analyzed ratios of cement-asphalt emulsion mortar were from the compressive strength test and flexural strength test. The proper result of these tests was 4:1 (cement:asphalt emulsion) thanks to the highest strength of the compression and flexibility. This appropriate ratio was then applied in pavement recycling stabilization in comparison with cement stabilization in order to determine the performance of the pavement recycling materials. The seven performance tests included 1) the Unconfined Compressive Strength test (UCS), 2) the Indirect Tensile Strength test (ITS), 3) the Repeated Load Triaxial Deformation test, 4) the water absorption and capillary rise test, 5) the WD-XRF analysis, 6) The XRD analysis, and 7) the Scanning Electron Microscope (SEM). These performance test results indicated that the increasing of the CAE content could enhance the UCS value, the ITS value, and the resilient modulus. Moreover, the CAE additive showed the improving of the tensile strain. Thus, the cracking caused by the traffic might hardly occur or decelerate. According to the micro-surface, the CAE mixture was dense and provided full of hydration reactions while the cement mixture was more porous. It showed that the CAE mixture has strength gain, less water absorption, and less capillary rise. Additionally, a higher ITS ratio and the UCS ratio revealed that the CAE mixture could perform well with excellent resistance from the water damage. In summary, the cement- asphalt emulsion as a stabilized agent is able to solve the road problems consisting of the cracking and the moisture damage, and enhance the strength, the flexibility, the deformation resistance, and the water resistance properties of the pavement recycling stabilization. Therefore, it is recommended that the cement- asphalt emulsion be a stabilizing agent for road rehabilitation and future highway construction industry in Thailand.