Tailoring rheological–strength–ductility properties of self-cleaning geopolymer composites with asphalt emulsion

Abstract

Metakaolin based-geopolymer is a promising construction material because of its sustainability and high strength. The frailty in road engineering application of geopolymer lies in its low ductility. Fortunately, a novel ductile fiber-reinforced geopolymer, known as engineered geopolymer composite (EGC)is developed. Nevertheless, its fluidity decreased obviously because of the bridging effect offibers. Asphalt emulsion (AE), as anself-cleaning building material, plays a significant role in improving rheological behavior,which remains understudied in EGC system. Thus, this study investigated the effects of adding PE fibers and AE on the rheological–strength–ductility properties of self-cleaning geopolymer composites as well as the geopolymerization reaction mechanisms. The mechanical test results, indicated that PE fibers dramatically improve ductility, while the strength first increases and then decreases with increasing AE content. The fluidity and rheological test results indicated the ability of AE to balance the ductility–rheological properties. Fourier-transform infrared spectroscopy revealedthat AE had an inhibiting effect on geopolymerization reaction but without a new functional group, and scanning electron microscopy/energy dispersive X-ray spectroscopy results indicatedthat the variation in AE contentchanged the particle size and shape of geopolymer gels and their geopolymerization degree. The nanoparticle size and zeta potential of geopolymers at 28 days quantitatively demonstrated the combined effect of PE fibers and AE on tailoring the rheological–strength–ductility properties. From above micro-scale analysis, a microscopic model illustrating the tailoring mechanism of self-cleaning geopolymer composites through AE addition was proposed, which offers the possibility to not only deeply discusses the role of AE in geopolymers but also unambiguously exhibits a prospective application in road engineering, such as 3D printing, and prefabricated cement concrete pavement.