研究了早期受冻环境下粉煤灰单掺以及与硅灰复掺情况下水泥砂浆试件的力学性能及其微观形貌的变化。结果表明，同配合比试件在标准养护条件下预养护2h再在-15℃受冻8h时，其3d抗压强度与标准养护3d的抗压强度相差不大。在单掺粉煤灰15％时，2 h标养后冻8 h的3 d强度达到标养的78．9％；粉煤灰掺入15％硅灰8％时的2 h标养受冻8 h的3 d强度能达到标养的81．0％，复掺后强度有所提高。粉煤灰等掺合料掺入有利于降低总孔隙率，而最可几孔径下降幅度较大，未掺加8 h受冻时为50．39 nm，而在8％硅灰20％粉煤灰受冻8 h时为11．06 nm，说明粉煤灰的加入降低了大孔含量，增加无害孔含量，而无害孔可以抵抗早期冻胀应力，合理的孔结构有利于提高水泥基材料的早期抗冻性。%Only fly ash and mixed with silica fume were added into cement-based material,the mechanical properties and microstruc-ture 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 15%fly ash was mixed,keep the cement mortar under the standard cu-ring condition for 2 hours and then to 15 degrees below zero 8 hours,the 3 days strength raised to 78.9%of standard curing cement mor-tar. The strength was improved when fly ash and silica fume were all mixed,when 15% fly ash and 8%silica fume were mixed,keep the cement mortar under the standard curing condition for 2 hours and then to 15 degrees below zero 8 hours,the 3 days strength raised to 78.9%of standard curing cement mortar.Compared with the blocks which were not added mineral admixture,the porosity of the groups added were all reduced,while the most probable aperture declined much,the block without active mineral admixture was 50. 39 nm when froze for 8 hour,while 8%silica fume and 20% fly ash was 11.06 nm,indicatingthat the addition of fly ash and silica fume 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.
展开▼
