CMA

9 Table 1. Raw materials used for the preparation of concrete specimens Symbol Raw materials Density (g/cm3) W Tap water 1 C Portland cement 3.16 FU Calcium carbonate 2.71 S Fine aggregate 2.61 G1 Coarse aggregate (crushed stone 2015) 2.61 G2 Coarse aggregate (crushed stone 1505) 2.61 AD1 Water reducing agent 1.05 AD2 Air entraining agent 1.05 The concrete specimens were prepared according to JIS A 1132. After filling the concrete into the mold, specimens were cured 1 day after which specimens were removed from the molds. Specimens were then cured under water at 20°C±20°C for 28 days. Specimens used for the measurements of compressive strength were cured under water immersion at 20°C±2°C for 7 days. The formulation of concrete specimens is shown in Table 2 Table 2. Formulation of concrete specimens. IWR stands for integral water repellent W/C S/ (S+G) IWR Unit kg/m3 (%) (%) (%) vs cement weight W C S G AD Control 51.8 43 0 183 366 725 991 2.93 MIC-RES 51.8 43 0.2 183 366 725 991 2.93 MIC-RES 51.8 43 0.5 183 366 725 991 2.93 MIC-RES 51.8 43 0.7 183 366 725 991 2.93 SIL-EM 51.8 43 0.5 183 366 725 991 2.93 W: Water, C: Cement, S: Fine aggregate, G: Coarse aggregate, AD: air-entraining and water-reducing admixture Previous studies have reported that suppressing the moisture that enters concrete is effective in extending the life of concrete structures, maintaining their aesthetic appearance and preventing frost damage [3]. Many researches explored technologies which could extend the service life of concrete [4]. Impregnation of concrete surface with alkylalkoxysilane was proved to minimize penetration of water and intrusion of chloride into treated concrete, delaying the ingress of chloride and therefore increased the predicted service life [5]. In the last 10-15 years, emulsion or powder of silane, siloxane or silicone resin-based additives started to be used as “integral water repellent” in mortar and concrete [6-7]. This is now an established technology, of which benefits are well accepted [8-9]. This document describes the utilization of a new integral water repellent based on a microencapsulated silicone resin in concrete. Previous studies were focusing on the impact of this additive in mortar or fiber cement boards, so cement-based material with no aggregates. This study explores the benefit of adding a new additive (DOWSIL™ IE 6686 Water Repellent), in particular related to the reduction of chloride ingress in modified concrete. For the sake of clarity, the additive DOWSIL™ IE 6686 will be referred as MIC-RES in this document. A silane emulsion was used as a reference for a general water repellent and will be referred as SIL-EM in this document. Most of the durability studies published in literature are assessing the deterioration of concrete after selection of one selected deterioration mechanism (whether chloride ingress, freeze thaw cycles, carbonatation). Effect of combining 2 or several deterioration mechanisms starts to be studied. For example, chloride ingress can be accelerated considerably by freeze thaw cycles-induced damages [10]. Understanding the impact of an additive during freeze thaw cycles is therefore important in the context of controlling chloride ingress as well. Material AND METHODS Preparation of concrete specimens The raw materials used for the preparation of the concrete specimens are listed in table 1.