The results of this investigation may serve as the basis for some conclusions with regard to the curing of Portland cement concrete. Some of the more important conclusions are as follows

l. A concrete, if it may be classed as such, consisting of fine aggregate, cement, and water, is not subject to the extreme effects of freezing as is a true concrete containing a coarse aggregate. 2. Maximum loss of strength, which is evidently long-enduring is suffered by concrete frozen in an extremely green stage when frost enters mortar paste. 3. Freezing may be harmful at any time within the first week. However, in most cases a recovery is indicated. 4. Steam curing, if not carefully controlled at optimum conditions, will result in loss of strength in a concrete. 5. The expansion and drying which occur at the temperatures in the steam chamber apparently are the cause of harmful results in steam.curing.

It must be borne in mind that the limitations of data gathered make these conclusions more indicative than conclusive. There is still much room.for further research at this institution along the line of both problems presented herein.