Strength, Durability and Creep of Fly-Ash Concrete: Part IIby Robert L. Day, Univ of Calgary, Canada,
Abstract: Tests on sulphate durability of various plain and fly ash mortars soaked in pH-controlled sulphate solutions were performed. The performance of several types of ash have been examined, including those described in a previous paper. The sulphate-expansion results indicate that care must be taken when choosing the type of fly ash for applications where sulphate durability is critical. The shrinkage and creep behaviour of plain and fly-ash concretes (30% and 50% replacement levels by volume) under saturated and drying conditions is also reported. Two design grades of concrete were manufactured and tested: (a) a 'high' strength, 45 MPa, non air-entrained mix, and (b) a 'low' strength 25 MPa air-entrained mix. All specimens were loaded when they achieved the same nominal strengths (rather than loading at a given age) - 40 MPa for the high-strength mixes and 20 MPa for the low-strength mixes. In these tests the time-dependent behaviour of concretes made with three different fly ashes, as well as appropriate plain control mixes, was examined. In general fly ash concretes showed reduced shrinkage and creep when compared to control concretes although the degree of improvement depended upon the type of fly ash used.
Subject Headings: Fly ash | Concrete | Strength of materials | Material durability | Shrinkage (material) | Creep
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