不同石粉及掺量对高延性工程水泥基复合材料的性能影响

Effect of different stone powder and content on properties of high ductility engineered cementitious composites

本文研究了花岗斑岩石粉(GP)、石灰石粉(LP)、石英石粉(QP)分别以20%、40%、60%、80%、100%等质量取代河砂制备工程水泥基复合材料(Engineeredcementitious composites,ECC)的宏观力学性能、自收缩性能和微观结构性能。力学性能试验结果表明:各拉伸试样峰值应力和极限拉应变随石粉取代率的递增先减小后增大,而抗压强度和抗折强度随石粉取代率的增加而增加,当石粉取代率为100%时,各试样力学性能最优,其中拉伸峰值应力达到4.4 MPa及以上,极限拉应变超过4.2%,抗压强度超过50 MPa,抗折强度超过18MPa,较基准组试样的力学性能有较大程度的提升。自收缩试验结果表明:各试样的自收缩随石粉取代率的增加而变大,当石粉完全取代时,掺GP、LP、QP的自收缩较基准试样分别增加了117.3%、127.3%、119.5%,为此,石粉取代河砂后对基体的稳定性产生了不利影响。微观结构试验结果表明:掺入石粉可以成为水化产物的成核基体并能促进其反应,其中石灰石粉促进效果最好;当各石粉掺量较大时,聚乙烯醇(PVA)纤维在基体中的分散性得到改善,基体和纤维能够共同承受荷载作用与协调变形,充分利用基体和纤维自身的强度。采用Logistic模型对自收缩试验结果进行拟合,得到的ECC自收缩预测模型预测效果较好,表明本模型具有一定的适用性。

The macroscopic mechanical properties,autogenous shrinking properties and microstructural properties of engineered cementitious composites(ECC)prepared from granitic porphyry powder(GP),limestone powder(LP)and quartz powder(QP)with the mass of 20%,40%,60%,80% and 100% instead of river sand were studied.The mechanical property test results show that:The peak stress and ultimate strain of each tensile specimen first decreased and then increased with the increase of stone powder substitution rate,while the uniaxial compressive strength and flexural strength increased with the increase of stone powder substitution rate,when the stone powder substitution rate was 100%,the mechanical properties of each specimen were optimal,and the peak tensile stress reached 4.4 MPa and above,and the ultimate strain exceeded 4.2%,its uniaxial compressive strength is more than 50 MPa,and its flexural strength is more than 18 MPa.Compared with the reference group,the mechanical properties of the specimens were greatly improved.Autogenous shrinkage test results show that:the autogenous shrinkage of each specimen becomes larger with the increase of stone powder substitution rate,when completely substituted,the autogenous shrinkage of doped GP,LP,QP increased 117.3%,127.3%,119.5% respectively compared with the benchmark specimens,for this reason,the stability of the matrix is adversely affected by the replacement of river sand by stone powder.The microscopic test results show that adding stone powder can be used as the nucleation matrix of hydration products and promote the reaction,and the limestone powder has the best promotion effect.When the content of each stone powder is large,the dispersion of polyvinyl alcohol(PVA)fiber in the matrix is improved,and the matrix and fiber can jointly bear the load and coordinate the deformation,making full use of the strength of the matrix and fiber.The logistic model was used to fit the autogenous shrinkage test results,and the obtained ECC self-shrinkage prediction model predicted better,and the validation found that this model has certain applicability.