Influence of Low Temperature on Concrete Properties

摘要

The aim of this article is to show the negative effect of the reduced ripening temperature on the increase in compressive strength.Laboratory tests were performed on a concrete mix with a vv/c ratio of 0.54.The samples were reformed for 2,5,8 hours at +18°C,and then were frozen once to-3°C and-8°C for 24 hours.After this time,the samples matured at +18°C.The greater the early strength,the lower the drop in compressive strength with a single freeze.The greatest decrease in strength was noted for concrete maturing 2 hours and once frozen to-8°C is 52.3%.The greatest impact on durability drops is: freezing temperature,pre-ripening time,type of cement used.Additionally,the methods of protecting concrete against the influence of negative temperatures are described.Laboratory tests carried out indicate a negative effect of the reduced temperature on the increase of compressive strength.The largest decrease in compressive strength in relation to the reference concrete was noted for concrete made of cement CEMII/BV 32.5R maturing for 2 hours in water at +18°C and once frozen in air to-8°C,a fall of 52.3 %.After analysing the test results,it was found that the drop in compression strength depends on the type of cement,the level of freezing temperature and the time of initial maturation.It was found that the lower the freezing temperature and the shorter the pre-ripening time,the greater the drop in compressive strength.The influence of negative temperatures on young concrete is harmful in every case,although this harmfulness has a different degree.It is therefore necessary to protect young concrete against this type of weather conditions.Concrete works under conditions of reduced temperatures are only possible if contractors take appropriate measures to enable binding and hardening of the concrete mix,e.g.by providing thermal protection,so that the young concrete in the element does not freeze.The reduced air temperatures have a negative effect on the setting and hardening of the concrete.The lower the ambient temperature of the concrete structure being made,the lower the concrete temperature and the younger the maturing process of the concrete is slower.