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. / Master of Science

As was stated before, the purpose of this problem was to find out the effect of freezing on mortar at different hours after mixing. This was a continuation of the work done by G.H. Harris in 1945. It was hoped that by using different materials, steel molds, and by molding, freezing and testing the specimens as accurately as was possible to do so with the equipment available the peculiar results obtained by Harris could either be verified or disproved. The results obtained by this problem were very irregular but did show a slight trend and did not show the great difference in strength over a short period of time as was shown by Harris’s results. To get a definite answer a large number of samples should be run for each different time of set before freezing. A large variety of materials should be used and it is also believed that test cylinders 6”x12” would give better results. / Master of Science