Concrete is an integral part of any structure as almost all structures are built with concrete and steel. From mixing to placing and setting to hardening, every stage of concreting is required to be dealt with care. Hardening is the process of gaining strength. It is the last stage of concreting after which the formworks (shuttering plates) are removed. Though hardening continues for years but more than 90% of strength is gained within 28 days of concreting. However, there are several factors upon which hardening of concrete depend. These factors as follows:
- The concrete of higher grade achieves strength faster than the concrete of lower grade due to its higher cement content. In simple words concrete of proportion 1:1½:3 will harden faster than concrete of proportion 1:2:4.
- Similarly higher grade of cement achieves strength faster than the lower grade of cement. This means Ordinary Portland Cement of 53 grade will achieve strength faster than that of 43 grade.
- Type of cement also affects the strength development of concrete. For example, Rapid hardening cement gains strength in shorter period of time than Ordinary Portland Cement whereas Low heat cement takes more time.
- If concreting is done at higher temperature then concrete will gain strength in shorter period of time. For this reason concrete takes more time to harden if done in winters.
- Size of the structural member also affects the hardening process. In other words if the structural member is large then it will harden faster and vice-versa.