【摘要】 为了研究不同羟乙基甲基纤维素(HEMC)对水泥砂浆性能的影响差异,本工作选用了三种HEMC制备改性水泥砂浆,分别为高、低取代度和聚丙烯酰胺(PAAm)改性HEMC,并从砂浆物理力学性能和孔隙率及孔径分布等角度进行了比较。结果表明,HEMC的掺加可使新拌砂浆保水率和稠度提高,同时使砂浆的拉伸粘结强度提高,但使抗压和抗折强度下降。取代度和PAAm改性对砂浆保水率和抗折强度的影响不大。相较于低取代度HEMC,高取代度HEMC改性砂浆具有更高的稠度和较高的拉伸粘结强度以及干燥收缩率。PAAm改性使HEMC改性砂浆稠度大幅下降,拉伸粘结强度降低。压汞法测试结果表明:纤维素醚的加入使砂浆中小孔减少,但却引入了相当数量的微米级大孔,增大了孔隙率,但不同HEMC改性砂浆之间的差异不显著。更多还原

【Abstract】 In order to study the influence of different hydroxyethyl methyl celluloses(HEMCs) on the properties of cement mortar, three kinds of HEMCs were used to prepare modified cement mortar in this paper. Those HEMCs are high, low substitution degree and polyacrylamide(PAAm) modified HEMC. The influence of the HEMCs on cement mortar was compared from the mechanical properties, porosity and pore size distribution. The results show that the addition of HEMCs can improve the water retention rate and consistence of fresh cement mortar, increase the tensile bond strength, but decrease the compressive strength and flexural strength. The substitution degree and PAAm have minor influence on the water retention rate and flexural strength. Compared to HEMC with low substitution degree, HEMC with higher substitution degree have higher consistence, tensile bond strength and dry shrinkage rate. PAAm significantly decreases the consistence of HEMC-modified cement paste and decreases the tensile bond strength too. The result of mercury intrusion porosimeter(MIP) shows that the small pores of mortar are reduced by the addition of HEMCs, meanwhile a considerable number of micro-sized macropores are introduced, and the porosity of cement mortar also are increased; but no significant difference observed among the HEMC-modified mortars.更多还原