True as far as moisture loss or gain in the ambient air above the concrete. Relative humidity is a function of temperature, (warmer air can hold more moisture so the relative humidity drops when warming air with equal moisture content), thus the warmer air can evaporate and hold the water used for wet curing. Countering this phenomena is the fact that the exhaust of the combustion heaters is made of water and carbon dioxide. If the burlap is kept wet or the water maintained on the curing slab, then the warmer air speeds the strength gain.
Artificially raising the temperature with heaters to cure the concrete can result in increased surface carbonation, a condition that can lead to scaling and an increase in the permeability of the concrete.
