早期CO_(2)养护与Nano-TiO_(2)协同作用下低热水泥基浆体的力学性能

Mechanical Properties of Low-heat Portland Cement-based Paste upon Early CO_(2)Curing and Nano-TiO_(2)Synergistic Effect

为探究早期CO_(2)养护和纳米TiO_(2)(nano-TiO_(2),NT)协同作用对低热硅酸盐水泥(low-heat portland cement, LHPC)力学性能的影响规律,测试了不同CO_(2)养护时间和NT掺量下LHPC的抗折、抗压强度,并结合扫描电镜、热重分析等测试结果分析其对力学性能的协同作用机制。结果表明:仅考虑掺入NT或CO_(2)养护,NT掺量或CO_(2)养护时间均存在最佳范围。CO_(2)养护与NT协同作用下,CO_(2)养护24 h内,LHPC浆体在14 d和28 d龄期的抗压、抗折强度分别在NT掺量为1%~1.5%和1.5%~2%时提升幅度大,这归因于试样中水化硅酸钙凝胶(C-S-H)、钙矾石(AFt)和CaCO_(3)质量增加,长径比较小的纤维状C-S-H细化了大于50 nm的孔径。而CO_(2)养护超过24 h、NT掺量大于2%时,试样中孔隙数量增加、较大长径比的晶须状文石和微观裂缝的产生降低了力学性能。综合力学强度和经济性,建议CO_(2)养护时间为12 h, NT掺量为1%。研究结果为提升LHPC早期力学性能提供一定的参考依据。

To explore the roles of the synergistic effects of CO_(2)curing and nano-TiO_(2)(NT)on the mechanical properties of low-heat portland cement(LHPC),the flexural and compressive strengths of LHPC were tested during various CO_(2)curing times and NT dosages.The influence mechanisms were analyzed using testing methods such as scanning electron microscopy and thermogravimetric analysis.The results indicate that there is an optimal range for both NT dosage and CO_(2)curing time when only considering the addition of NT or CO_(2)for curing.Under the synergistic effect of CO_(2)curing and NT curing,the compressive strength and flexural strength of LHPC pastes at 14 d and 28 d ages increased significantly when the NT content was 1%~1.5%and 1.5%~2%,respectively,within 24 h of CO_(2)curing.This is due to the increase in the mass of calcium silicate hydrated gel(C-S-H),ettringite(AFt)and CaCO_(3) in the samples.The fibrous C-S-H with a small aspect ratio refined the pore size of more than 50 nm.When CO_(2)curing exceeds 24 hours and NT content is greater than 2%,the number of pores in the sample increases,and the generation of whisker like aragonite with larger aspect ratios and micro cracks reduces the mechanical properties.Considering the comprehensive mechanical strength and economy,it is recommended that the CO_(2)curing time be 12 hours and the NT dosage be 1%.The research results provide a certain reference basis for improving the early mechanical properties of LHPC.