超高韧性磷酸镁水泥基复合材料压缩力学性能研究

Study on Mechanical Properties of Ultra-high Toughness Magnesium Phosphate Cement-based Composites Under Compression

磷酸镁水泥(Magnesium phosphate cement,MPC)是一种具有凝结时间短、早期强度高、粘结性能好等诸多优点的新型无机胶凝材料,但材料本身具有脆性性质,应变能力低。工程水泥基复合材料(Engineered cementitious composites,ECC)是通过在水泥基复合材料中添加高性能纤维制备而成。通过纤维增韧技术,可以制备出同时具备MPC和ECC优良特性的超高韧性磷酸镁水泥基复合材料(Ultra-high toughness magnesium phosphate cement-based composites,UHTMC)。本工作通过拉伸试验证实了UHTMC具有优异的拉伸力学性能、应变硬化和多缝开裂特征。通过试件的轴心抗压强度、极限压应变、受压弹性模量和泊松比分析了粉煤灰(Fly ash,FA)替代量(0%、15%、30%和45%)和养护龄期(14 d和28 d)对UHTMC压缩力学性能的影响规律。结果表明,UHTMC试件表现出良好的压缩韧性,随着粉煤灰替代量的增加和养护龄期的延长,试件的轴心抗压强度和受压弹性模量升高,但极限压应变降低,泊松比变化较小。通过对UHTMC的轴心受压应力-应变全曲线进行分析,提出和建立了轴心受压本构关系模型。最后,从微观层面上分析了粉煤灰替代量和养护龄期影响UHTMC宏观压缩力学性能的机理。

Magnesium phosphate cement(MPC)is a new type of inorganic cementitious material with many advantages such as short setting time,high early strength and good bonding performance.However,MPC-based composite materials have brittle properties and low strain capacity.Engineered cementitious composites(ECC)is prepared by using high-performance fibers to improve the toughness of cement-based composites.Through fiber toughening technology,ultra-high toughness magnesium phosphate cement-based composites(UHTMC)with excellent properties of MPC and ECC can be prepared.Here,through the axial tensile test,it is confirmed that the UHTMC has excellent tensile performance,strain hardening and obvious multi-cracking behavior.The effects of fly ash(FA)(substitution amounts:0%,15%,30%and 45%)and curing ages(14 d and 28 d)on the mechanical properties of UHTMC under compression were analyzed by the axial compressive strength,ultimate compressive strain,compressive elastic modulus and Poisson’s ratio of the specimens.The results show that the UHTMC specimens exhibit good compressive toughness.With the increase of FA substitution amount and curing age,the axial compressive strength and compressive elastic modulus also increase,but the ultimate compressive strain decreases,and the Poisson’s ratio changes little.Through the axial compression stress-strain curve of UHTMC,the constitutive relation model of axial compression is proposed and established.Finally,the influence mechanism of FA substitution amount and curing age on the macroscopic mechanical properties of UHTMC under compression was analyzed at the micro level.