Low impact steam cure is the highest recommended curing method. Using low impact steam cure, involved covering slabs after they have set up, then using heat during the early phase of the concrete curing cycle, usually the first 16-24 hours.

Temperature affects concrete strength gain, which is accelerated by warm temperatures and retarded by cooler temperatures. Moreover, temperature affects concrete color, i.e., warm temperatures cause lighter colors, while cooler temperatures have a darkening effect. Consequently, variations greater than 5°F in the curing environment should be reduced or eliminated by proper heat distribution, air circulation, and enclosure insulation.

Due to “latent heat of vaporization,” heating concrete by means of steam or vapor is 10 times more efficient than using warm air. Thus, replacing hot air with steam or vapor as a curing medium will reduce heating costs by 90 percent. A longer cover phase and higher curing temperature (up to 140°F) produce higher early strength. Because concrete maintained for a longer period of time at an elevated temperature (between 100°F and 140°F) develops a higher early strength, longer curing duration and/or higher curing temperature would suit concrete products that require high early strengths for secondary processing, shipping or installation.

Using a controller and good heat blankets is the optimal method for smaller shops to employ low impact steam cure techniques. Check out this link for heat blankets from Powerblanket

We cover the top with plastic, then with power blanket electric concrete curing blankets to cure our concrete overnight. We use pretty much standard mix ingredients and a non-chloride accelerator when needed. We strip everything the next day (winter or summer) at an average of 5,000 – 6,000 PSI (50% of ultimate) with no problems such as warpage, plastic shrinkage or map cracking (signs of improper curing).

This will DRASTICALLY improve the quality of slabs at 48 hours and an additional benefit is that heated slabs are preferred when sealing with Counterhard and First SealZ.

Curling – Consider what causes curling:Different moisture loss (or gain) from different parts of the slab (top or bottom) at different times. Slabs on grade lose moisture more rapidly through the top than the bottom; the top of the slab has more of a reduction in volume than the bottom of the slab (because they were poured with conventional concrete with excess water). The slab curls.

How to eliminate it: Pour at a very low water to cement ratio (don’t have any free water to evaporate, its all needed for hydration), cover and heat the slabs (get more of the cement to use the available water rather than having “extra water” that could evaporate leading to curling prior to striping). Get the slabs over 5,000 to 6,000 psi before you strip them (heat them overnight use accelerator if needed). Porosity is directly related to strength. The higher the compressive strength (at exposure to atmosphere less than 100% humidity) the less likely the slab will give off or absorb moisture (change volume).