The brittleness and low fracture toughness of autoclaved aerated concrete (AAC) could be improved by fibres, but the deterioration of its thermal insulation performance are commonly observed. In this study, different combinations of recycled wood fibre and rubber powder were added in AAC to improve its performance and reduce the negative environmental impacts of solid waste. In addition to the fluidity of slurry, the physical, mechanical and thermal properties of AAC were systematically investigated, together with the phase components and microstructure images. AAC with relative high mechanical strengths and excellent thermal insulation performances could be obtained because of the reinforcement of wood fibre and the gas introduced by rubber powder. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed that the positive effects of wood fibre and rubber powder were the results of physical interactions.

Introduction

Recently, energy conservation with respect to buildings has become a growing concern (Ko
cí et al., 2013). In China, 20.6% of the total energy and 19.0% of the total carbon emission have been consumed by building in 2016 (China Building Energy Saving Technic Association, 2019). A series of energy codes for buildings has implemented to effectively reduce building energy consumption. To achieve the goal of 65% building energy conservation, the internal-external insulation measure and wall materials with good thermal insulation performance are adopted (Wang et al., 2019). Autoclaved aerated concrete (AAC) has been reported to be the only wall material meets the Chinese national standard requirement of the energy conservation for buildings (He et al., 2018). AAC is usually the mixture of quartz powder (or fly ash), cement, lime, gypsum, water and small quantities of aluminum powder, which is hardened and strengthened under pressurized steam (Israngkura Na Ayudhya, 2016; Schreiner et al., 2018). Compared with ordinary concrete, AAC has the more excellent thermal insulation properties and the lower density (Asadi et al., 2018; Ma et al., 2016; Yuan et al., 2017). However, AAC products also have some drawbacks, such as high brittleness and low mechanical strength, which limits their commercial applications (Cong et al., 2016; Ferretti et al., 2015; Koudelka et al., 2015). Moreover, recent trends have focused on utilizing industrial wastes to produce highperformance AAC, that is, AAC with high volume stability, high mechanical strength, and excellent thermal insulation properties (El-Didamony et al., 2019). Studies have shown that adding fibre was a simple and effective way to obtain AAC with relatively high volume stability and mechanical strength (Bonakdar et al., 2013; Laukaitis et al., 2012; Pehlivanlı et al., 2016).