早期受冻环境下含矿粉水泥砂浆抗冻性能研究

Study of anti-frostproperty of cement mortar added with slag in case of early frost

研究了不同掺量矿粉及与硅灰复配对不同的早期受冻环境下水泥砂浆的强度、水化产物及其微观形貌的影响。结果表明:在添加复合防冻剂的情况下,预养护2 h以上的试块进行-15℃受冻8 h,试件3 d强度发展几乎不受影响,与标养3 d的强度相差不大。预养护2 h,进行-15℃受冻8、10、12 h,复掺时矿粉10%硅灰8%时早期抗冻效果最佳。通过3 d龄期试件的微观形貌和孔隙观测,可发现矿粉的加入使孔隙率有一定程度的降低,但是相比于未掺加组变化不是很大;当矿粉与硅灰复掺时,孔隙率和最可几孔径均有较大幅度的降低,8%硅灰+10%矿粉10 h受冻组的最可几孔径为32.29 nm,相比于未掺加组的151.04 nm,有很大程度的改善。说明了矿粉与硅灰的复掺能促进早期水化产物的形成,降低有害孔的含量,优化孔隙分布及孔径的大小,使试件能够有效抵抗早期受冻的破坏。

Only mineral powder and silica fume were added into cement-based material, the mechanical properties and microstructure changes of cement mortar was studied in case of early frost.The result indicate with mixture specimen under the standard curing condition maintenance for 2 hours and then to 15 degrees below zero 8 hours, the 3 days compressive strength is nearly the same with the cement paste curing in standard environment for 3 days.When only mineral powder was mixed, the dosage of 15% is the best and the strength was better, keep the cement mortar under the standard curing condition for 2 hours and then to 15 degrees below zero 8 hours. When 8%silica fume and 10% mineral powder was added, the early antifreeze effect is the best.The microstructure and pore distribution of cement mortar with different proportion and different cold environment were observed, the results show that the added of mineral powder leaded to a certain degree of lower porosity, while the change is not obvious.When silica fume and mineral powder were mixed together, the porosity and most probable aperture all decreased much, the block without active mineral admixture is 151.04 nm when froze for 8 hour,while 8% silica flame and 10% mineral powder was 32.29 nm,proving that the the pore structure improvedgreatly. Indicating that the addition of mineral powder and silica flame reduced the content of macroporous,increased the content of harmless pore, while harmless pore could resist early frost heaving stress, proving that reasonable pore structure could improve the early frost resistance ability of cementitious material.