Effect Of Mineral Admixtures Properties Of Cement-based Materials Under Constant Lowtemperature

In winter construction,concrete is susceptible to low temperatures,often causing irreparable damage;at the same time durability is also largely lost.Replacing part of the concrete with fly ash and silica fume can not only promote the recycling of industrial waste,but also improve the performance of concrete.This has become a common method in engineering.However,the application of this method in negative temperature concrete is relatively rare,especially under constant negative temperature conditions.In this paper,the effects of the type and amount of admixture on the strength,durability and pore structure of cement-based materials under different constant and negative temperature curing conditions were investigated.The test results show that the freezing temperature has a great influence on the performance of the cement-based material,and its strength and gas permeation resistance decrease with the decrease of the freezing temperature.Especially at-20 °C,the performance growth is slow or even decreases with the increase of age,and construction work should be avoided under too low negative temperature.Silica fume admixture has a good effect on improving the early strength,gas permeability and pore distribution of cement-based materials under constant temperature and negative temperature curing conditions.Gas permeability and pore distribution are optimized with increasing dosage,but the strength change with the increase of the dosage is not significant;while the performance of the fly ash admixture on the cement-based material has a certain degree of deterioration with the increase of the dosage,and the appropriate dosage should be carefully determined before use.