Title:
Use of Hydrophobic Agents as Concrete Admixtures
Author(s):
G. Moriconi and F. Tittarelli
Publication:
Symposium Paper
Volume:
212
Issue:
Appears on pages(s):
279-288
Keywords:
concrete admixture compatibility; hydrophobic admixture; water absorption
DOI:
10.14359/12691
Date:
6/1/2003
Abstract:
The environmental attack on reinforced concrete structures can he reduced by preventing water penetration into the 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. The 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. The simultaneous presence of either plasticizing or air-entraining admixtures does not negatively affect the effectiveness of the hydrophobic agent even if different ways of addition are used. An appreciable increase in the cement paste porosity, related to an ex- pected reduction in mechanical strength, is observed only for cement paste with the highest w/c (0.50).