Penetrability of chloride ions in concrete protected by an acrylic painting

Abstract

In order do decrease the penetrability of chloride ions in concrete the use of paintings based on polymers can be a good solution. The use of acrylic paintings is recommended because they have good resistance to ultraviolet radiation. It is important to quantify the decrease of chloride ions penetrability obtained by the use of this kind of paintings. The durability of the polymeric paintings is another aspect that needs to be analysed. In this study an acrylic painting was used to protect the concrete and decrease the penetrability of chloride ions. The concrete used was a C12/15, with a cement content of 280 kg/m3 and a water-cement ratio of 0.60. The acrylic painting was applied in concrete specimens 28 days after casting. In order to have a better protection we applied two coats separated by 5 hours. The penetrability of chloride ions was measured following the ASTM standard C 1202 – 94. Before the penetrability tests, some specimens were exposed to UV radiation. The exposition to the light occurred by cycles consisting of alternating periods of 8 hours of UV radiation at 60 ºC and 16 hours without UV radiation at 50 ºC. Three kinds of exposition were made consisting on 5, 10 and 15 cycles. The results showed always a high penetrability of chloride ions. This occurred because a poor concrete was used. The protection by an acrylic painting decreases the penetrability of chloride ions. The charge passed decreased about 32 %. However, is not possible to achieve low chloride ions penetrability only with the use of acrylic paintings. It is necessary also the use of a good concrete with low porosity. After the exposition to the UV radiation the penetrability of chlorides ions did not increase. It seems that the UV radiation does not affect the properties of the acrylic painting.