Use of Hydrophobic Agents as Concrete Admixtures

Abstract

Environmental-induced degradation of reinforced concrete structures can be reduced by preventing water penetration into concrete pores using hydrophobic agents as concrete admixtures. In order to point out problems related to their practical use, the effectiveness of hydrophobic admixture on cement pastes with different w/c, and in the presence of other commonly used chemical admixtures, was studied. Capillary water absorption and the contact angle between water drops and the cement paste surface were evaluated. Changes in the cement paste porosity due to the hydrophobic admixture were studied by porosimetric analysis. Results obtained show that the hydrophobic admixture is able to reduce the prolonged capillary water absorption in all cement pastes by about 70%, regardless of how it is added. The hydrophobic agent appears even more effective during the initial phase of water absorption, especially with increasing w/c.