SELF-PROTECTED UNDER WATER CONCRETE'S WASH-OUT RESISTANCE

Abstract

Under water concrete constructions faces the problem of washout, which gradually results in erosion and material loss. To overcome this, by altering the water characteristics in conjunction with the use of an underwater protective agent, a ‘Self Protected under water concrete’ (SPUC) was developed. Various tests were conducted to assess compressive strength and washout rates. An experimental program involving 20 concrete mixes was conducted to examine the behavior of concrete when placed under water. The study utilized four tests: non-dispersion test (US Army Corps CRD C61), slump, slump flow (SF), and pH value test. The experiments focused on five parameters: UPA concentration, water-to-cement (W/C) ratio, superplasticizer (SP) content, fine aggregate (FA) ratio, and water environment. Results indicated that increasing UPA concentration reduced washout. Mass loss was higher with increased W/C ratio or SP content, while it decreased with a higher fine aggregate ratio. Seawater showed greater resistance to washout compared to freshwater. The pH test results aligned with those from the CRD C61 test, though freshwater specimens had higher pH values due to its higher alkalinity. A correlation was found between mass loss and pH changes for both UPA and UPA-free mixtures. Based on these findings, it is recommended that guidelines for SPUC proportions be incorporated into technical standards.