Study on the influence mechanism of hydrophobic materials-MPTMS and DMDMOS on the water resistance performance of asphalt mixtures

Abstract

The interfacial adhesion between aggregate and asphalt is a critical factor affecting the water damage resistance performance of asphalt mixtures. To enhance the adhesion between aggregate and asphalt, Methyltrimethoxysilane (MPTMS) and Dimethyldimethoxysilane (DMDMOS) were co-opted to modify the aggregate surface. The interfacial strength between aggregate and asphalt was analyzed by water boiling test and contact angle experiment, and the mechanism of aggregate interfacial modification was investigated by combining SEM, FTIR and MD. The results showed that: hydrophobic treatment of aggregates reduces the water absorption rate of aggregates in a wet environment and significantly improves the water damage resistance of asphalt mixtures; MPTMS and DMDMOS reduced the aggregate surface polarity component, thus improving the match between aggregate and asphalt; The optimal processing environment for aggregates is acidity and 30 minutes. Further mechanistic tests and simulations showed that the reactive Si-O portion of the polymer reacts with the Si-O-C portion of MPTMS and DMDMOS to form hydrophobic clusters on the surface of the polymer, increasing the aggregate surface roughness. The clusters attract asphalt molecules to arrange closely and orderly around them. The intramolecular interactions and molecular angular energy of asphalt molecules are significantly reduced, which improves the stability of the aggregate-asphalt system, and further enhances the bonding energy between the aggregate and the asphalt, thus improving the water damage resistance of asphalt mixtures.