Abstract

An unusual variety of concrete deterioration was encountered. The distress was due to concrete exposure, during a decade of service, to poorly drained calcium-absorptive acidic soil, and ground water having a negative Langlier saturation index. The calcium loss was due to a mechanism akin to ion-exchange or chromatographic phenomena. The deterioration resulted in the essential depletion of calcium of the portland cement paste, which left relatively pure silica gel. The attack was accelerated because the concrete was very porous in areas, a result of the manufacturing process used to make the concrete conduit.

Steps to prolong concrete service life in similar environments include use of dense and low-permeable concrete, limestone aggregate, and limestone fill. This type of aggressive environment can be identified in the field by use of kits that measure calcium-absorption characteristics of soils, and pH.

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