Lightweight and low thermal conducted face-centered-cubic cementitious lattice materials (FCLMs)

Abstract

Lightweight and thermal insulative cementitious materials with large porous structures for improving energy efficiency have rapid development currently. However, the design of cementitious materials for energy-efficient building system in terms of low thermal conductivity, excellent mechanical properties and lightweight remains a crucial challenge in construction & building fields. Recently, the polymer-based lattice-inspired structures fabricated by 3D printing technology (3DPT) show a rapid development that achieves a balance of thermal and mechanical properties due to their ordered and large-scale cellular architecture. In this work, a novel category of lattice-inspired cementitious lattice materials was first proposed for applying in the energy-efficient building systems by integrating the 3DPT and traditional casting technology. Taking face-centered cubic (FCC) lattice as an example, the advantages of the proposed fabrication technology and FCLMs are follows: (i) ultralight weight; (ii) enhanced ductility of brittle cementitious materials; (iii) low thermal conductivity. Through the structural and material design, the proposed fabrication technology could effectively overcome the current issues of 3DPT, such as the weakness of interlayer performance and low accuracy (Extrusion-based 3DPT) as well as limited feasible materials (Powder-bed-based 3DPT), in the civil engineering. Statement of Significance: How to design cementitious materials for energy-efficient building system in terms of thermal conductivity, mechanical properties and lightweight requirement remains a crucial challenge in construction & building fields. Inspired by the low thermal conductivity and lightweight structure of metamaterials in the previous researches (Song et al., Materials & Design, 2019. 173: 107773-86; Nicholas et al. Nano letter, 2018. 18: 4755-61), here a novel category of lattice-inspired cementitious materials with ordered porous structures has been proposed for energy-efficient building materials with lightweight, low thermal conductivity and good mechanical properties characteristics. Additionally, recently there is increased interest to use 3D concrete printing technology (3DCPT) to automatically manufacture complicated and customized structure. However, currently, 3DCPT encounters many sticky issues, involving that (i) weak interlayer performance induced by cold joints between layers; (ii) deformation under self-weight due to the low yield stress of fresh mix; (iii) probable shrinkage under the low water/cement ratios typically used in printed mortars; (iv) geometrical instability owing to creating suspended structures. It is not a trivial to directly print cementitious porous materials, and therefore this work also achieved a breakthrough in developing cementitious porous materials combining advanced SLA 3D printing and traditional casting technology for the first time. It is worth mention that compared to Extrusion-based 3DCPT and Powder-bed-based 3DCPT, the advantages of the manufacture technology include that (i) automatically printing 3D complex structure; (ii) Optional cementitious materials; (iii) Good interlayer performances of prepared materials. We expect that the proposed design idea and novel manufacture strategy could serve as the guideline to develop material-structural-functional integrated energy-efficient building materials combining 3D printing technology, advanced structure design and high-performance cementitious materials.