Evaluation of Nanotechnology Additive on Tack Coat Moisture Resistance and Bond Strength

摘要

This study evaluated the laboratory bond strength and moisture susceptibility of a nanotechnology (derived from organosilane) modified emulsion against a control CSS emulsion. This additive is designed to convert the surface of the treated material (untreated aggregate, soil, or HMA) from a water loving (hydrophilic) surface to a water repelling (hydrophobic) surface while providing equivalent bond strength compared to an unmodified emulsion with a higher residual AC content. Two-layer slabs were produced in the laboratory with the following variables: emulsion type, surface type (new HMA or milled), and application rate (three different rates). Cores were obtained from each slab to evaluate the effect of the critical variables using a monotonic shear bond strength test. The results of the bond strength evaluation showed the modified emulsion provided equivalent bond strength to a control emulsion with 3 times the residual AC content. Additionally, an experimental evaluation was conducted to assess the moisture susceptibility of the tack coat materials. Additional slabs were fabricated at the optimum application rate for each surface type and emulsion application. The AASHTO T283 procedure was utilized to condition these specimens with one or two freeze-thaw cycles prior to determining their bond strength. The results of this evaluation were mixed. The data suggested moisture damage was occurring in the new HMA surface specimens, but not in the specimens with a milled surface interface. For the new HMA specimens, the control and nanotechnology modified emulsions had equivalent resistance to moisture damage as freeze-thaw cycles were applied to the specimens.