CMA

8 Lecomte Jean Paul Dow Performance Silicone, Belgium Sakae Ushijima, Taro Minato, Ryusei Oka, Katsuhiko Taniguchi Technical Research Institute, Asunaro Aoki Construction Co Limited, Japan Hideyuki Mori Dow Toray Co Limited, Japan Micro-Encapsulated Integral Water Repellent For Cementitious Materials ABSTRACT This paper describes the use of a new integral water repellent for cementitious materials based on a microencapsulated silicone resin. The impact of the new additive on water uptake, resistance to freeze thaw cycles and mechanical properties of concrete is given. Effectiveness of the additive as integral water repellent at different depth within the concrete samples have been evaluated INTRODUCTION The porous structure of construction materials based on Ordinary Portland Cement leads to high sensitivity to capillary water absorption. Sodium or calcium chloride are water soluble salts which can be found in deicing salts or in sea water and which can be transported by water into cement-based, porous construction materials, such as concrete. Ingress of chloride into concrete is therefore triggered by the absorption of chloride containing water. After evaporation of water, the salts remain inside the pore system, leading to increasing concentration of chloride as a function of exposure time [1a]. Ingress of chloride ions into concrete can continue by further absorption of chloride rich water or by diffusion of chloride ions from high to low concentration regions. Deterioration of steel reinforced concrete can be accelerated by the ingress of chloride ions. As corroded steel occupies more space than the original steel, it leads to cracking of cement matrix, spalling or delamination of the concrete cover [1b]. Controlling chloride ingress and therefore chloride- induced corrosion is key to extend service life of reinforced concrete exposed to deicing salt or close to sea shore. Predicted service life is directly linked with the probability for the chloride ions to reach the reinforcement with concentration reaching 0.7% Cl-/cement, which could therefore initiate the start of the corrosion process [2]. Reduction of water ingress and chloride ingress is then of primary interest to delay degradation of concrete and corrosion of reinforcement steel bars.