Investigations on the Long-Term Durability of Hydrophobic Treatments on Concrete

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Title: Investigations on the Long-Term Durability of Hydrophobic Treatments on Concrete

Author(s): M. Raupach and L. Wolff

Publication: Special Publication

Volume: 212

Issue:

Appears on pages(s): 409-426

Keywords: concrete; durability; hydrophobic teatment

Date: 6/1/2003

Abstract:
Supplementary hydrophobic treatments of the concrete surface can be a durable and potent method to lower the moisture content of the concrete and to improve its durability by inhibiting the migration of aggressive substances as well as slowing down the corrosion process. At the Institute for Building Materials Research in Aachen, ibac, comparative tests have been carried out on the efficiency and long-term durability of different hydrophobic agents on different types of concrete. The effectiveness and durability of the hydrophobic treatment was monitored using a sensor called multiring-electrode, which indicates the variation of humidity of the concrete in different depths by measurement of its electrolytic resistivity. The results hsow that the applied dosage on the specimens influenced the durability and efficiency of the hydrophobic treatment most significant. Other factors like active content, type of active agent or penetration depth have only a subordinate influence. The results showed also that a drying tendency of the specimen was only ob- served on the specimens weathered artificially in the VENUS test facility. Short rain periods of some minutes per day as simulated in the VENUS testing facility do not result in a high moisture content of the specimens. In contrast, a drying behaviour was observed also under a relative humidity of 95%. Long rain periods of several hours per day and a typical autumn weather with drizzle lead to a rising moisture content of the naturally weathered specimens even with an applied hydrophobic treatment.