偏高岭土对低热硅酸盐水泥水化性能的影响

采用不同掺量偏高岭土取代水泥配制低热硅酸盐水泥净浆和砂浆,测试了不同净浆的凝结时间,采用微量热仪测试了净浆的水化放热速率和放热量,测试了砂浆抗压强度和抗折强度发展,采用XRD分析了净浆物相组成.结果表明,偏高岭土缩短了低热硅酸盐水泥初凝和终凝时间,缩短了胶凝材料体系的水化诱导期,并使加速期和减速期提前,但并未提高7 d水化放热量,其对早期水化的促进作用随掺量提高而更显著.掺量在10%以内时,偏高岭土促进砂浆强度发展,14 d时促进作用最为显著,但掺量不宜超过15%.偏高岭土未改变低热硅酸盐水泥水化物相种类,但可明显降低产物中氢氧化钙的含量,其火山灰反应在28 d后仍在进行。

Influence of metakaolin on hydration performance of low heat Portland cement

Metakaolin(MK)was used to partially replace low heat Portland cement(PLH)to prepare pastes and mortars.The setting time of the pastes was tested while the hydration heat was measured by calorimeter.The compressive and flexural strength of the mortars were determined and the phase composition of the hardened pastes was analyzed by XRD.The results show that the application of MK reduces the initial and final setting time of PLH.The induction period of PLH hydration is reduced and the acceleration and deceleration periods are moved in advance by MK.However,the hydration heat at 7 d is not increased.The higher the replacement level of MK,the better promotion effect on the early hydration process.The strength of the mortar is increased by MK when the dosage is no higher than 10%,especially at the age 14 d.The replacement level should not be higher than 15%.The content of CH in PLH hydrates is decreased by MK,but the phase type keeps invariant.The pozzolanic reaction of MK in PLH proceeds after 28 d.