Influence of Maximum Aggregate Size on Compressive Strength of Concrete Exposed to Evaporation Immediately After Casting

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Title: Influence of Maximum Aggregate Size on Compressive Strength of Concrete Exposed to Evaporation Immediately After Casting

Author(s): Dan Ravina

Publication: Journal Proceedings

Volume: 70

Issue: 8

Appears on pages(s): 582-588

Keywords: aggregate size; aggregates: compressive strength; concretes; cracking (fracturing) : evaporation; fresh concretes: hot weather construction: microcracking: plastic shrinkage: research; tensile stress.

Date: 8/1/1973

Abstract:
The influence of maximum aggregate size on the compressive strength of concrete and microconcrete (sieved mortar), exposed to evaporation immediately after casting, was studied. The main variants were: (a) maximum aggregate size 1/4 in. (19.05 mm), 1/2 in. (12.5 mm), 3/8 in. (9.6 mm), 3/16 in. (4.8 mm); (b) time of exposure to evaporation- 0, 45, 90 and 300 min. Concrete and air temperature in the first 24 hr 30 C (86 F); initial rate of evaporation about I kg/m2/hr (0.2 Ib/sq ft/hr). It was found that the aggregate restrains the plastic shrinkage associated with drying. The resulting tensile stresses impair the properties of the concrete, as internal cracking and reduction in strength were observed. The larger the maximum aggregate size or aggregate content, the higher the internal cracking and the loss of strength after 5 hr exposure to evaporation: 21, 12 and 5 percent, for concretes with maximum aggregate size of 3/4, 1/2 and 3/8 in., respectively.