A Cooperative Laboratory Study of the Effect ofTesting Environment and Specimen Type ofn Shrinkage of Masonry Unit Concrete
ACI Committees 716 and 213
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Shrinkage of concrete masonry units, an important factor in cracking of walls, has commonly been measured on full-size units by methods which may require from 1 to 3 months to complete. ACI Committees 716 and 213 undertook a cooperative test program in 1958 to evaluate three methods-Reference, Modified British, and Rapid-using whole specimens, face shells, and thin, horizontal slices. The major comparisons required 720 specimens from 10 lots of commercially produced block made of Five aggregates by two different curing methods. The Rapid method was adjudged unsatisfactory because of poor correlation with the results of other methods. The Modified British and Reference methods were found to be in substantial agreement in most instances. Face shell specimens cut longitudinally were found to give shrinkages comparable to those for whole block. The use of face shells cut longitudinally and tested by the Modified British method can result in testing economies of both space and time. A statistical analysis is presented.