Straw characteristics and mechanical straw building materials: a review

To develop green thermal insulation materials made of straw to replace high energy consumption and high pollution materials, such as asbestos and polystyrene, this paper reviews the relevant characteristics of straw as a thermal insulation filler and the research progress of mechanical straw building materials (i.e., the straw filler is placed in the interlayer and fasted by friction or gravity). Research studies on straw combustion, moisture absorption, and heat transfer mechanisms are reviewed. Additionally, the research status of three kinds of mechanical straw building materials, namely straw bales/laminated wallboards, beetle elytron plate walls, and mixed straw fillers, is also explained. This assessment shows that straw thermal insulation fillers have good fire safety and thermal insulation performance. The straw bale/laminated wallboard system is mature, with rich varieties and practical applications, while beetle elytron plate walls and mixed straw fillers are still in the development stage. Although there are many related research results, more reports on the heat transfer mechanism, material selection, and application forms are needed, which is an important direction for future systematic research. Actively promoting the application of green mechanical straw-filled sandwich structures in more fields will produce good social and economic benefits.