Fracture Properties of Geopolymer Concrete Based on Metakaolin, Fly Ash and Rice Rusk Ash

Geopolymers are exclusively mineral nature and are considered an alternative to materials based on Portland clinker, whose production accounts for about 5% of anthropogenic CO2 emissions in the world. The geopolymer cement concrete (GCC) may be prepared from natural oxide-aluminosilicates such as metakaolin (MK), or synthetic, such as fly ash (FA) together with active silica contained in the rice husk ash (RHA). The fracture properties of the Portland cement concrete (PCC) with 25 MPa and 50 MPa, and of three different geopolymeric concretes with the same strength Classes were determined for comparative analysis. The aim of this study is to provide support to begin the use of geopolymers in the reinforced concrete precasting Industry. Three-point bending tests of notched beams with a/d (notch depth/beam depth) of 0.5 from RILEM TC80-FMT Recommendations were used to determine the critical values of K, G, R and J-integral for crack propagation under mode I. The results showed that the geopolymeric concretes exhibit similar mechanical behavior and fracture properties higher that those determined in PCC for the same strength class.

地质聚合物（Geopolymers）完全属于矿物类材料，被视为硅酸盐水泥熟料基材料的替代方案——这类熟料的生产占全球人为二氧化碳排放量的约5%。地质聚合物水泥混凝土（Geopolymer Cement Concrete, GCC）可由天然铝硅酸盐氧化物原料（如偏高岭石（metakaolin, MK））或合成原料（如粉煤灰（fly ash, FA））与稻壳灰（rice husk ash, RHA）中所含的活性二氧化硅共同制备。本研究针对强度等级分别为25 MPa与50 MPa的硅酸盐水泥混凝土（Portland Cement Concrete, PCC），以及三种强度等级与之匹配的不同地质聚合物混凝土，测定其断裂性能以开展对比分析。本研究的目标是为钢筋混凝土预制行业推广地质聚合物的应用提供支撑。依据RILEM TC80-FMT建议，采用a/d（切口深度/梁深度）为0.5的带切口梁三点弯曲试验，测定I型裂纹扩展下的K、G、R及J积分临界值。结果表明，相同强度等级下，地质聚合物混凝土展现出与硅酸盐水泥混凝土相近的力学性能，且断裂性能更优。