CMA

12 Figure 2. Water absorption of reference and modified concrete specimens as a function of the depth of the surface tested after 24 hours contact time with water Plot of absorbed water (after 24 hours contact time with water) as a function of the depth of the tested surface are not linear. Very low water absorption is observed with the top surface of the concrete specimens. The “internal surfaces” which is 5 or 10 mm deep, are somewhat showing higher water penetration. Water absorption of “internal surfaces” deeper than 10 mm are decreasing again, and stays somewhat constant till the deepest tested “internal surface”. The increase water absorption of the “5 mm deep internal surface” is more pronounced when the silane emulsion is used as integral water repellent. It was suggested earlier than droplets of silane can somewhat migrate into a fresh mortar (or concrete in this study) to enrich the surface, but this will at the same time deplete a layer within the mortar or concrete specimens [13]. Curing of concrete specimens under water may have induced somewhat some migration of the integral water repellent to the surface or into the water, leading to this decreased resistance to water penetration of the “top” concrete layers. Absorption of salty water In order to assess the potential benefit of adding integral water repellent based on microencapsulated silicone resin on the reduction of chloride ingress, absorption of salty water was assessed as well. The absorption of salty water by reference and modified concrete specimens was conducted in accordance with JIS A 6909: 2014 “Water Permeability Test B Method”. The sodium chloride concentration was 10 weight %. The same testing device as described earlier (see picture 1) was used but absorption of saltwater was measured after 72 hours contact time with water. The cylindrical φ100 x 200mm concrete specimens were cut with a concrete cutter to remove layers of 5 mm and 50 mm of concrete from the top surface such as to be able to measure water absorption of the “inside surfaces” which are 5 and 50 mm deep. Table 5 shows the results of the saltwater absorption. Table 5. Absorption of salty water by reference and modified concrete specimens (measured at 5 and 50 mm depth) after 72 hours contact time with salty water It can be seen that absorption of salty water is significantly reduced when either the silane emulsion or the microencapsulated silicone resin is used as integral water repellents. Water exclusion (which is the reduction of water penetration, as compared to the reference concrete specimens) indicates a reduction of water penetration by almost a factor of 2. Both integral water repellents were confirmed to have the ability to significantly decrease the absorption of salty water up to the depth of 50 mm. Compressive strength of concrete The compressive strength of reference and modified concrete specimens are given in Table 6. Specimens modified with the microencapsulated silicone resin (MIC-RES) show higher compressive strength than the reference, unmodified concrete specimens. 0 5 10 15 20 25 30 35 40 45 50 55 0.00 0.50 1.00 1.50 2.00 2.50 Polished depth (mm) Water permea ti on (ml) Control MIC-RES (0.2%) MIC-RES (0.5%) MIC-RES (0.7%) SIL-EM (0.5%) Specimens Depth mm Absorption of salty water (ml) Water exclusion (%) Control 5 2.08 - 50 2.23 - MIC-RES (0.5%) 5 1.00 48 50 1.22 54 SIL-EM (0.5%) 5 1.18 57 50 1.08 49