Kajian Karbonasi pada Beton Mutu Tinggi Memadat Mandiri

The rapid development of infrastructure in Indonesia has increased the demand for construction materials such as concrete. One modern innovation is high-strength self-compacting concrete (SCC), which can flow and compact without external vibration. However, SCC still faces durability challenges, particularly carbonation, which can reduce the pH of concrete and trigger reinforcement corrosion. This study aims to evaluate the effect of carbonation on the compressive strength and pH reduction of SCC and to determine the effectiveness of metakaolin as a pozzolanic additive in slowing down the carbonation rate. The experimental method used cylindrical specimens with a diameter of 75 mm and a height of 150 mm, incorporating metakaolin at substitution levels of 10%, 12.5%, 15%, 17.5%, and 20%. Accelerated carbonation testing was conducted by immersing the samples in a 4% carbonate solution for 15, 37, and 51 days, followed by phenolphthalein spray tests. The results showed that a 15% metakaolin substitution yielded the best performance, reducing the carbonation rate by up to 44.41% compared to normal concrete, with a carbonation coefficient under normal atmospheric conditions of 3.71 mm/year½. While the addition of metakaolin reduced fresh concrete workability, it still met the SCC requirements as outlined in EFNARC 2002. This study confirms that metakaolin enhances the durability of SCC against carbonation.