When Should I Use High Early Strength Cement?

(When Should I Use High Early Strength Cement?)

When should I use high early strength cement

High early-strength concrete has become increasingly popular in the construction industry for rigid pavement maintenance and precast concrete due to its advantages in time and cost reduction, as well as its construction efficiency. Typically, these mixes use admixtures that accelerate the early hydration of concrete, such as setting accelerators and hardening accelerators, which can reduce the initial setting period of the mix. However, the mechanism of these admixtures on the early hydration of concrete paste has not been clearly evaluated.

Step 1: The hydration behavior of a cement paste containing 2.0 % KBr and 3.0 % Ca(HCOO)2 was investigated at 23 and 50 degC curing temperature using XRD analysis and Fe-SEM. The results showed that the addition of KBr and Ca(HCOO)2 could greatly increase the early hydration of cement paste and promote the early formation of C3S, resulting in an enhanced compressive strength of the paste.

Moreover, the addition of KBr and Ca(HCOO)2 significantly decreased the initial and final setting time of the cement paste when the curing temperature was increased from 23 degC to 50 degC. This was mainly due to the dissolution of KBr and Ca(HCOO)2 into the hydrate layers of the cement paste.

The addition of KBr and Ca(HCOO)2 not only accelerated the hydration of C3S but also greatly increased the ettringite formation, which favors the concrete’s early strength improvement. In particular, the diffraction-peak intensities of the hydrated particles (C3S and CH) in a sample cured at 23 degC after 2, 4, 8, and 24 h of curing were much higher than those in the samples cured under lower temperatures.

(When Should I Use High Early Strength Cement?)