Influence of low calcium fly ash on the durability of high strength concrete in marine environment

摘要

Marine environment is one of the most hostile environments on the earth for any constructionrnmaterials, and concrete is also not excluded. One of the major concerns for concrete structuresrnin marine environment is the problem with durability. In fact, durability is the key factor in therndesign of marine concrete structures. Since durability of concrete is increased with increase inrnconcrete's compressive strength, always high strength concrete is only the designer's choicernfor marine structures. Available findings showed that by incorporating certain amount of flyrnash into high strength concrete as a partial substitute for cement, the durability of the highrnstrength concrete was improved significantly. This paper presents a laboratory study on therninfluence of mineral admixture, fly ash, on the strength and durability performance of superrnplasticized high strength concrete. The concrete specimens were assessed based on short termrntesting techniques which are recommended by the Concrete Institute of Australia for thernpurpose of designing and controlling the concrete in marine environments. These includerncompressive strength, water absorption test, apparent volume of permeable voids test, andrnwater sorptivity test. Measurements were carried out on specimens at 28 days' and 45 days'rnage after curing at room temperature. In general, the results showed that fly ash improved thernoverall performance of high strength concretes, but at different rates depending on thernamount of fly ash admixture and the design grade of specimens. Fly ash required a relativelyrnlonger time to get its beneficial effect, but in the long term, the mineral admixture increasedrnthe concrete compressive strength substantially but relatively lesser improvements on waterrnabsorption and sorptivity