椰子纤维MPC复合水泥基材料受压性能试验研究

(1.广州大学 土木工程学院,广东 广州 510006; 2.广州大学工程抗震研究中心,广东 广州 510006)

桥梁加固; 抗压性能; 磷酸镁水泥; 椰子纤维; 养护龄期; 能量吸收

Experimental study on compressive performance of coconut fiber MPC composite cement-based materials
WU Hui1, HUANG Min1, ZHANG Liwen1, XIE Zhujian2, ZHANG Junping2

(1.School of Civil Engineering, Guangzhou University, Guangzhou 510006, China; 2.Earthquake Engineering Research and Test Center, Guangzhou University, Guangzhou 510006, China)

bridge reinforcement; compressive properties; magnesium phosphate cement; coir fiber; curing age; energy absorption

DOI: 10.15986/j.1006-7930.2022.02.013

备注

磷酸镁水泥(Magnesium Phosphate Cement,简称MPC)是一种早期强度高、凝结硬化快、干缩变形小、粘结能力强的胶凝材料,可用于高架桥、机场跑道和市政主干道的快速修补等方面.然而,MPC存在韧性差、抗裂性能差的缺点,严重限制了MPC在实际修复工程中的应用.经前期研究发现,在MPC中掺入椰子纤维(Coconut Fiber,简称CF)能有效提高其抗裂性能,然而,CF对MPC力学性能的影响规律和作用机理尚未清晰,因此,需要对椰子纤维加固磷酸镁水泥(Coir Fiber Reinforced Magnesium Phosphate Cement,简称CF-MPC)这一新型生态复合材料进行系列研究.本文主要研究不同体积掺量(1%、2%、3%、4%)CF在不同养护龄期(7 d、28 d)下对MPC静态受压性能的影响.首先,通过静态压缩试验分析了椰子纤维掺量和养护龄期对CF-MPC试件的破坏形态、抗压强度、应力-应变曲线和能量吸收性能的影响规律; 其次,通过扫描电子显微镜(Scanning Electron Microscope,简称SEM)和X射线衍射(X-ray diffraction,简称XRD)分析,测试了不同CF掺量在不同养护龄期下,CF-MPC微观结构和水化组分的变化规律,从本质上探明了CF对上述宏观力学性能的影响机理.结果表明:在7 d、28 d两个养护龄期下,CF掺量对MPC静态抗压性能的影响相似.当CF掺量高于1%时,MPC脆性明显降低,且CF掺量为2%时,试件破坏形态由脆性变为一定的延性; CF-MPC试件抗压强度、弹性模量和割线模量随椰子纤维掺量的增加而略有降低,但随龄期的增长而增大; 能量吸收随着CF掺量的增加及龄期的增长均呈增大趋势,且当CF掺量为4%、龄期为28 d时能量吸收达到最大; 微观分析中,随着CF掺量的增长,主要水化产物六水磷酸钾镁(MgKPO4·6H2O,简称MKP)逐渐减少,而随着龄期的增长MKP逐渐增加.
Magnesium phosphate cement(MPC)is a kind of cementing material with high early strength, quick setting and hardening, small drying and shrinkage deformation, and strong bonding ability, which can be used for rapid repair of viaducts, airport runways, and municipal main roads. However, some of its defects, e.g., the low toughness and poor crack resistance, become obstacle to further applications. Previous study has shown that the anti-cracking performance of MPC can be significantly improved by adding appropriate amount of coconut fiber(CF). However, the effect law and action mechanism of CF on the mechanical behavior of the MPC are not yet clear. Thus, it is necessary to carry out a systematic study on coconut fibre reinforced magnesium phosphate cement(CF-MPC), which is a new ecological composite material. In this paper, the effects of different CF volume dosages(1%, 2%, 3%, 4%)at different curing ages(7 d, 28 d)on the static compression performance of MPC has been studied. Firstly, a uniaxial static compression test was conducted to analyze the influence of CF dosage and curing age on the failure mode, compressive strength, stress-strain curve, and energy absorption performance of CF-MPC. Secondly, the microstructure and hydration components of CF-MPC with different CF dosage at different curing ages were tested and analyzed by means of scanning electron microscope(SEM)and X-ray diffraction(XRD), and the influence mechanism of CF on the macroscopic mechanical properties of MPC was revealed. The results showed that the effects of CF dosage on MPC static compression performance at the curing ages of 7 d and 28 d were similar. When CF dosage was higher than 1%, the brittleness of MPC was significantly reduced, and when CF dosage was 2%, the failure mode of the specimen changed from brittleness to a certain ductility. The compressive strength, elastic modulus and secant modulus of CF-MPC specimens decreased slightly with the increase of coconut fiber content, but increased with the increase of age. Energy absorption increased with the increase of CF dosage and curing age, and reached the maximum when CF dosage was 4% and curing age was 28 d. In microscopic analysis, the main hydration product, potassium magnesium phosphate hexahydrate(MKP), gradually decreased with the increase of CF dosage, while MKP gradually increased with the growth of curing age.