Effect Of Early Curing Methods On The Mechanical Properties And Durability Of Concrete

Appropriate curing can improve concrete durability significantly, especially the early age curing of concrete is the key to the later properties of concrete. Actually in the practical construction, the curing of concrete is paid no more attention. There are some deficiencies for the current study on the concrete curing, because most of the studies have targeted the curing after concrete hardening, lacking of study of practical construction under harsh environment. For the lack of existing research, this paper has combined the curing time and curing condition together. Curing time is fixed to be the duration of hardening and the curing condition is set to be familiar with the practical construction under the harsh environment, such as wind curing, high temperature curing and light with wind curing. Comparing with the natural curing inside room, the effects of the curing methods under harsh condition on the properties of concrete have been studied in this paper. By the study of early curing time and curing methods, it is useful to provide information for the curing specification's update.As for mortar, it is indicated that curing methods before hardening are significant for compressive strength of 28d, and coated curing before hardening is the best among these three curing methods, thus the light with wind curing before hardening is the worst. Coated curing before hardening is significant for mortar with mineral admixture. The 28d compressive strength of mortar with 10% fly ash with coated curing before hardening is up to 42.0MPa which is slightly larger than that of mortar with no mineral admixture. The sensibility of coated curing before hardening to compressive strength increases as the amount of mineral admixture increases. The 28d compressive strength of mortar with 50% fly ash increases by 200% compared to the 3d's. The water absorption of coated curing before hardening is the least.As for the mechanical properties and durability of concrete, curing methods before hardening are not significant for concrete curing in water after the form removal, but it is very significant for that of concrete curing inside room after the form removal. Curing methods before hardening are more significant for C30 concrete than C60 concrete. The water absorption of concrete with wind curing before hardening is the largest among these three curing methods, and the water absorption of concrete with coated curing before hardening is the least. The compressive strength and the durability of concrete increase with the sequence of the curing methods before hardening: wind curing, inside room curing and coated curing.The shrinkage of concrete increases as the ratio of"water to binder"increases. Adding mineral admixture can reduce the shrinkage especially can play a role in balancing the later shrinkage. The shrinkage increases as the temperature increases and the relative humidity decreases. The effect of relative humidity on shrinkage is more sensible than that of temperature.The surface properties of concrete depend on the combined effects of surface pores and cracks. The surface porosity of C30 concrete is more than surface cracks, as for C60 concrete, the result is totally opposite. The coated curing before the form removal can extraordinarily reduce the inside extension of surface cracks in the concrete. The curing methods before hardening can affect the hydration degree of cement on the surface and inside. The coated curing before the form removal is benefit for hydration degree both of the surface and inside. The wind curing before the form removal can prevent the hydration degree of the surface concrete, thus the high temperature curing before the form removal can prevent the hydration degree of the inside concrete.