The construction sector has undergone significant reforms towards increased sustainability in recent decades. Therefore, there has been a great interest in developing alternative binders for stabilising expansive clay subgrades and improving their mechanical properties while mitigating their swelling and shrinking behaviour. One such alternative binder is vinyl acetate-ethylene (VAE) polymers. However, there are only a few studies on utilising polymers, especially VAE polymers, for clay stabilisation. Specifically, there is a lack of research on using VAE polymer-stabilised clays for road subgrade purposes. This study aims to address this knowledge gap by evaluating the potential of using a VAE solid powder polymer to stabilise expansive clay subgrade through a comprehensive series of mechanical tests as well as physicochemical and microstructural analyses. The results of the experiments provide evidence that the introduction of the polymer considerably improved the mechanical strength and swell and shrinkage behaviour of the expansive clay.

In cold and saline soil areas, concretes usually experience multi-factor erosions, such as freezing- thawing cycles (FTCs), drying-wetting cycles (D-Ws), and salt erosion. To promote green and sustainable development of the construction industry, municipal solid waste incinerator bottom ash (MSWIBA) was adopted as a partial replacement for conventional fine aggregates in concretes. In this study, the coupled effects of the D-Ws and salt erosion (i.e., 5 % NaCl solution and 5 % Na2SO4 2 SO 4 solution) were experimentally conducted to investigate the mechanical and micro- structural properties of ordinary and MSWIBA concretes. The results showed that D-Ws had a negative effect on the mechanical properties of concretes. The depth and width of cracks in concretes increased with the D-Ws raised. During the D-Ws, the influence of salt solution on concretes could be divided into two stages. Initially, the filling effect of salt crystals was beneficial to the development of concrete strength. Subsequently, salt crystals accumulated in concretes caused cracks, and accelerated the deterioration of concrete specimens. Meanwhile, sodium sulphate reacted with hydration products in concretes to produce some expansive substances, the evident diffraction peaks of expansive substances (e.g., gypsum and ettringite) had been clearly observed after D-Ws. Thus, the damage effect of 5 % Na2SO4 2 SO 4 solution (SS) to concrete structure was more serious than that of water (WT) and 5 % NaCl solution (CS). Furthermore, the total porosity of the concrete specimens generally decreased with the MSWIBA substitution rate increased. There was an optimal MSWIBA content for concretes to obtain the excellent mechanical and microstructural properties. In detail, when the substitution rate of MSWIBA was between 0 % and 33.0 %, it had an excellent effect on improving the pore structure of concretes. Specifically, the compressive strength of concretes was larger than 35.0 MPa when the substitution rate of MSWIBA with natural river sand was between 24.8 % and 57.8 %, whereas the substitution rate of MSWIBA should not exceed 33.0 % exposed to D-Ws. This study could provide a significant reference for the sustainable development of concretes in cold and saline soil areas, as well optimization and innovation usage of MSWIBA.