低温条件下矿物掺合料对混凝土强度发展及抗冻临界强度的影响

Study on the Strength Development of Low-temperature Concrete with Mineral Admixture

目的为了推广矿物掺合料在冬期施工中的应用。研究了不同掺量矿物掺合料的混凝土在低温条件下的强度发展情况。及其对抗冻临界强度的影响．方法采用恒低温一次冻结法和自然变低温多次冻结法。测试各种掺量的混凝土在不同龄期的强度值、抗冻临界强度值及在低温条件下达到该值的时间．结果复掺复合外加剂和适宜掺量矿物掺合料的混凝土，在低温条件下能够防止早期受冻，强度发展满足冬期施工要求．粉煤灰掺量不宜超过15％，硅灰掺量不宜超过5％，双掺粉煤灰10％和硅灰4％取代水泥时，效果更显著．结论结合复合外加剂，单掺粉煤灰10％～15％和硅灰5％，低温7d强度可达到设计强度的50％，低温7d转正温7d强度达到设计强度；双掺粉煤灰10％和硅灰4％取代水泥。低温7d强度达到设计强度的60％。低温7d转正温7d强度超过设计强度。恒低温条件下28h达到抗冻临界强度3．5MPa。变低温条件下34h达到抗冻临界强度4．1MPa，均满足规范要求．

This paper aims to research the strength development and the resistant freezing critical strength of concrete with mineral admixture under low- temperature, and ascertain the replacement ratio of cement.Using once artificial freezing and repetitious natural freezing method, comparing with concrete mixed without mineral admixture, studied the strength development of concrete. The results show that concrete mixed with proper mineral admixture and compound chemical can get perfect strength development, especially for fly ash of 10 %, silica fume of 4 %. The strength of - 7 d can reach 50-60 % of the designed strength of 28 d, and the strength of - 7 d ＋ 7 d can reach or exceed the designed strength of 28 d. At the same time, reaching the resistant freezing critical strength of 3.5 MPa in 28 h under the temperature of - 10 ℃ and reaching 4.1 MPa in 34 h under the temperature of 5 - 15 ℃.