超轻质工程水泥基复合材料的制备与力学性能

Preparation and mechanical properties of ultra-lightweight engineered cementitious composites

摘要:

为解决超轻质工程水泥基复合材料（ultra-lightweight engineered cementitious composites,ULECC）存在的强度较低和材料成本较高的问题,在微观力学设计理论的指导下,开发出一种兼顾强度和经济性可持续的ULECC。采用粉煤灰漂珠（fly ash cenosphere,FAC）和空心玻璃微珠（hollow glass microsphere,HGM）两种轻质填料,加入纤维素丝（cellulose filaments,CF）进行纳米增强,同时讨论水胶比的影响。共设计了5种配合比,其中3种可被归为ULECC。结果表明:提出的ULECC仅添加1%的PE纤维即可实现密度低至1 296 kg/m³,强度达41.9 MPa,拉应变达10.28%；水胶比是影响ULECC力学性能的重要因素,随着水胶比的减小,ULECC抗压强度、初裂强度和抗拉强度均逐渐增大,延性先减小后增大。SEM微观结构表明,掺入轻质填料会增大孔隙率,降低基体断裂韧性,使得延性显著上升。与传统工程水泥基复合材料（ECC）相比, ULECC在不过多损伤强度的前提下,提供了具有竞争力的变形能力,大大提高了可持续性,降低了材料成本。

Abstract:

To address the issues of low strength and high material costs associated with ultra-lightweight engineered cementitious composites (ULECC), a sustainable ULECC that balances strength and cost has been developed based on micro-mechanical design theory. Two types of lightweight fillers were used: fly ash cenospheres (FAC) and hollow glass microspheres (HGM), along with cellulose filaments (CF) for nano-enhancement. The influence of the water-binder ratio was also examined. A total of five different mix ratios were designed, three of which can be classified as ULECC. The results indicate that the proposed ULECC, with only 1% PE fiber addition, achieves a density as low as 1 296 kg/m³, a strength of 41.9 MPa, and a tensile strain of 10.28%. The water-binder ratio is a key factor affecting ULECC′s mechanical properties. As this ratio decreases, the compressive strength, initial cracking strength, and tensile strength of ULECC gradually increase, while ductility first decreases and then increases. Scanning electron microscopy (SEM) analysis shows that incorporating lightweight fillers increases porosity and reduces the matrix′s fracture toughness, leading to a significant rise in ductility. Compared to traditional engineered cementitious composites (ECC), ULECC provides competitive deformation capability without excessive damage strength, which greatly improves sustainability and reduces material costs.