Evaluations of Asphalt-Based Sealant Used in Concrete Caulking: Rheology, Adhesion Properties, and Microstructures

A concrete expansion joint can be damaged due to certain conditions. The performances in terms of temperature sensitivity and adhesion of used sealant materials in concrete caulking have strong relations to the joint service life. In this work, a composite-modified asphalt-based sealant (AS-M) with added styrene-butadiene-styrene (SBS), crumb rubber (CR), and tackifier resin (TR) modifiers was prepared, and its microstructure, high-temperature viscoelasticity, low-temperature crack resistance, and adhesion properties were evaluated, with two commercial finished sealants (AS-A and AS-B) as a reference. Specifically, Fourier transform infrared spectroscopy (FTIR) was used to analyze the chemical compositions of asphalt sealants, and the results showed that the physical blending and chemical reactions coexisted in the self-prepared sealant. A good compatibility and continuous structure for each sealant could be observed by fluorescence microscopy (FM). A dynamic shear rheometer (DSR) experiment was conducted to characterize the viscoelastic properties at high temperatures. The self-prepared sealant obtained the highest complex modulus, phase angle, and deformation resistance ability; the composite modifiers showed an outstanding modified effect. The glass transition temperature (Tg) was measured by dynamic mechanical analysis (DMA) testing. The Tg value of the self-prepared sealant was similar to that of the commercial sealant with SBS modifiers, whereas the stress relaxation modulus at a low temperature of the self-prepared sealant was the lowest, indicating that the combination of the modifiers made it obtain a better stress relaxation ability at low temperatures. The self-prepared sealant possessed the best interface adhesive capacity between sealant and aggregate based on surface free energy theory. The experimental results showed that the asphalt sealant modified by SBS/CR/TR has excellent performances in various properties and can be used for concrete caulking. (C) 2022 American Society of Civil Engineers.