Abstract: Green concrete products, such as building products, are placed on pallets. Those pallets are transported to a kiln for curing and from the kiln after cure by an overhead crane. Pallets are lowered into and removed from open top kilns layer by layer being supported by movable support ledges, for example rotatable toggles, at each layer position which permit vertical entry and removal of the pallet layers. Three kiln compartments permit continuous production, one being filled, one being emptied and the third curing a load of pallet layers.

Abstract: A system for curing concrete products resident in a kiln, in particularly for producing high strength building blocks from relatively dry green concrete, controls temperature and humidity in the kiln as a function of time in the curing cycle from a water pool heated by underwater grates near the upper water surface. Heated air and air/CO.sub.2 mixture also is circulated in the kiln during relevant portions of the curing cycle. Accelerated evaporation from the water well is induced by ruffling the water surface with the circulated air with enough intensity that the grates are uncovered to quickly evaporate water films wetting the grate surfaces. A baffle structure thus directs circulating air into the water surface. Individual grates are heated at critical times during the heating cycle in a manner to control temperature of different zones within the kiln by means of circulating hot liquids, such as oil.