Evaluation on the performance of lightweight cementitious composite enhanced by 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 material 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 synthetic 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 was that it had excellent mechanical properties and bond strength with steel reinforcement compared with traditional foam concrete, which is promising for structural applications. In addition, the early-age shrinkage resistance and durability of CNF-LCC were superior to normal weight concrete and lightweight aggregate concrete. Furthermore, CNFs can produce varying degrees of improvement on these engineering properties due to the modification of microstructure.