Covenham Reservoir Wave Wall--A Full-Scale Experiment on the Weathering of Concrete


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Title: Covenham Reservoir Wave Wall--A Full-Scale Experiment on the Weathering of Concrete

Author(s): J. W. Figg, A. F. Bravery, and W. H. Harrison

Publication: Special Publication

Volume: 100


Appears on pages(s): 469-492

Keywords: air entrainment; cement content; concrete durability; erosion; long-time study; reservoirs; sands; vegetation; walls; water-cement ratio; water-reducing agents; weathering; Materials Research

Date: 4/1/1987

A full-scale prospective durability experiment was established in the spring of 1970 at Covenham, Lincolnshire, England, when five different concrete mixes were used to construct portions of the wave wall of a 88 Ha inland reservoir. The reservoir is approximately 1.0 x 0.9 km in plan, and the maximum water depth is 14 m. The concave face unreinforced wave wall at the top of the embankment faces southwest into the prevailing wind and is subject to wave action in winter. Variables tested were a, increased sand proportion, b, air entrainment, c, increased cement content, and d, use of a lignosulfonate-based water-reducing admixture. The standard concrete mix used for the rest of the reservoir was used as a control. The alternate bay method of construction used for the wave wall insured adequate replication for both test and control concretes. To date, all mixes have performed well, although weathering differences began to show at 4 to 6 years when the alkalinity of the concrete surfaces had been reduced sufficiently by carbonation to allow growth of microorganisms, particularly lichens. Yellow lichen species were most prominent at first, but subsequently were overtaken by grey/green lichens. After 10 years of exposure, all the modified concrete mixes showed less weathering effects than the control mix with least improvement given by the air-entrained concrete a and the mix containing a higher sand percentage b. Increasing the cement content c gave a significant improvement, but the best performance has been obtained with the concrete d batched with a lignofulfonate-based water-reducing admixture.