Admixtures to Reduce the Permeability of Concrete


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Title: Admixtures to Reduce the Permeability of Concrete

Author(s): Salil K. Roy and Derek 0. Northwood

Publication: Special Publication

Volume: 170


Appears on pages(s): 267-284

Keywords: Admixtures; compressive strength; fly ash; polypropylene fibers; portland cement; silica fume; waterproofing.

Date: 7/1/1997

Water penetration and premature deterioration are widespread problems in reinforced concrete structures, particularly in the tropics. Many different chemical and mineral admixtures have been proposed as possible solutions. This paper examines high quality concretes modified with fly ash, silica fume, polypropylene fibre or certain chemical admixtures so as to reduce the permeability and hence make concrete more durable and watertight. Experiments were conducted at the National University of Singapore using different combinations of these admixtures supplied by four local manufacturers. A total of 39 mixtures were tested for pressure penetration and water absorption as well as compressive strength. The results show significant variation in the penetrability characteristics of the different concretes tested. Most products had some beneficial effect on pressure penetration, but little influence on absorption. One proprietary ingredient tested was found to greatly reduce both pressure penetration and absorption producing a concrete that was virtually completely watertight.