Performance of lightweight cementitious composite incorporating carbon nanofibers

Cellular concrete is a type of lightweight concrete traditionally applied in building industry for its thermal and acoustic insulation properties. However, in recent years, there is a surge in interest in potential applications of cellular concrete as a structural component due to its low self-weight, saving in raw materials and sustainability. Cellular concrete can be broadly divided into aerated concrete and foam concrete based on the pore-formation approaches. However, foam concrete is preferred to aerated concrete for structural applications due to better bubble size distribution, non-autoclaved curing process and no limitations in the dimensions of components. The main challenge for foam concrete is to have high-performance pore walls to provide required mechanical properties, shrinkage resistance, and durability under reduced density. In this paper, an ultrahigh performance concrete (UHPC) produced by a low water/cement ratio, optimum particle grading and incorporating carbon nanofibers (CNFs) was used as a base mix. It was then blended with homogeneous micro-foam bubbles to produce a lightweight cementitious composite (CNF-LCC) with 1500 ± 50 kg/m³ density for structural use. The novelty of CNF-LCC is that it has excellent mechanical properties and bond strength with steel reinforcement compared with traditional foam concrete, which is promising for structural applications. In addition, other engineering properties including early-age shrinkage resistance and durability of CNF-LCC are superior to normal weight concrete and lightweight aggregate concrete. Furthermore, CNFs can produce varying degrees of improvement on these engineering properties due to modification of its microstructure.