Prof. Adil Alaoui
Bowen Hall 307
Prof. Alaoui in visiting from the
University Abdelmalek Essaâdi
Faculty of Science and Technology
Resistance of Concrete to Marine Salt
Prof. Adil Alaoui, Abdelmalek Essaidi University, Tangier, Morocco
in collaboration with Prof. George Scherer and Dr. Sulapha Peethamparan, Princeton University
A great deal of new construction is occurring in Morocco along the sea shore, where marine salts can cause corrosion of reinforcement, leading to loss of strength of concrete structures. We propose to examine the performance of concretes, based on local Moroccan materials, upon exposure to salts. Our goals are to predict their service life and, if possible, to identify methods to improve their durability.
When concrete is exposed to marine salts, several reactions occur. Chlorides can adsorb on the hydrated phases, which have high surface areas. More importantly, the ions can stimulate the conversion of monosulfo-aluminate into Friedel’s salt, 3CaO·Al2O3·CaCl2·10H2O. This causes expansion of the cement paste that may be great enough to cause cracking. Whereas adsorption consumes chloride and delays corrosion, cracking from the formation of Friedel’s salt enhances the diffusivity of salt and thereby facilitates corrosion. The greatest damage occurs when the steel reinforcement in concrete rusts. Ordinarily, the steel in concrete is protected by an oxide layer, owing to the high pH (~13) of the water in the pores of the paste. However, chloride ions destabilize the oxide, leading to formation of rust; the rust has a larger volume than the steel it replaces, so it causes expansion and cracking of the concrete. To delay this process for as long as possible, we must reduce the rate of penetration of chlorides.
We will evaluate the transport properties of cement pastes before and after exposure to marine salts using 1H NMR (in the Chemistry Department at Princeton) to measure diffusivity of water. The liquid permeability will be measured using the beam-bending method for cement paste and the thermal expansion method for concrete (both in Prof. Scherer’s lab). We will look for changes in permeability (caused by microcracking) following exposure to salts and/or cycles of wetting and drying. Steady-state chloride diffusivity will be measured directly in a diffusion cell that will be constructed for this study.
SCIENTIFIC PUBLICATIONS (last 5 years)
1.Plastic densification in silica aerogel,T. WOIGNIER, A. HAFIDI ALAOUI, I. BEURROIES, J. PHALIPPOU, Euro. Phys. Journal, 6 (1999) 267.
2.Stress intensity factor in silica alcogels and aerogels, A. HAFIDI ALAOUI, T. WOIGNIER, F.PERNOT, J. PHALIPPOU, J. Non-Cryst. Solids.265 (2000) 29.
3.Mechanical properties of porous glasses,T. WOIGNIER, F. DESPETIS, A. HAFIDI ALAOUI, P. ETIENNE,J. PHALIPPOU, J. Sol-Gel Science and Technology 19,(2000) 163
4.Evolution of textural properties of solid network shape and size of silica gels during drying, Ph dieudonné, A.Hafidi. Alaoui, P.Delord, J.Phalippou, Article accepté au journal of Sol-Gel Science and Technology,(2002)
5.Silica dissolution-redeposition in gels and aerogels, Ph dieudonné, P.Delord, S. CALAS, A.H. Alaoui, J.Phalippou, Article accepté au journal of Sol-Gel Science and Technology,(2002)
6.M. ZAHER, A. HAFIDI ALAOUI et al, " Etude géomécanique d’un matériau granulaire", Revue de Mécanique Appliquée et Théorique, volume 1, n°3, pp. 165-170, Octobre 2002.
7.Large scale porous structure in gels : relationship with their mechanical properties, T. WOIGNIER, M. LAMY, A.H.AlAOUI,P. DIEUDONNE, I BEURROIES, J. PRIMERA, J. Sol-Gel Sci. Techn.26,143-147, 2003
8.Mechanical behaviour of highly porous glasses” T WOIGNIER, L.DUFFOURS, A.ALAOUI, A.FAIVRE, S.CALAS, J.PHALIPPOU, J Non Cryst. Solids 316,160-166 (2003)
9.Mechanical properties of gels : from alcogels and aerogels to glasses,T. Woignier, J. Phalippou, F. Despetis, P.Etienne, A. Alaoui, L. Duffours,Sol-Gel Technology Vol. 1 Chap. 18 Kluwer Academic Press Ed. SAKKA. (2004)
PUBLICATIONS IN THE FIELD OF CIVIL ENGINEERING
10.M. ZAHER, A. HAFIDI ALAOUI, H. EZBAKHE, J. PHALIPPOU, et T. WOIGNIER, " Identification structurale du tout-venant de carrière "Makay-radio"", Revue Marocaine de Génie Civil (2004).
11.M. ZAHER, A. HAFIDI ALAOUI, H. EZBAKHE, J. PHALIPPOU, et T. WOIGNIER, " Estimation du CaCO3 présent dans le tout-venant de carrière "Makay-radio" par MEB et par les analyses thermochimiques et thermiques", Revue Marocaine de Génie Civil (2004).
12.M. ZAHER, A. HAFIDI ALAOUI, H. EZBAKHE, J. PHALIPPOU, et T. WOIGNIER, « Caractérisation Structurale d’un matériau granulaire de carrière : le Makay-radio », International Journal Physical & Chemical News, best Edition, volume 22, pp 10-13, March 2005.