Influence of anti washout admixtures and coarse aggregate types on self-flowing underwater concrete properties

One of the main problems of conventional concrete under water is the high percentage of material loss due to the washout of cement paste. This research presents the influence of anti washout admixture (AWA) and coarse aggregate types on various properties of self-flowing underwater concrete. AWA is water soluble organic polymer, which increases the cohesion of concrete, in a way that significantly reduces the washout of the finer particles, i.e., the cementitious material and sand from fresh concrete when it is placed underwater. The work involves three groups with the total number of twenty-four self-flowing underwater underwater-concrete mixes. The test program was designed and arranged to consider the effect of four different parameters as follows; AWA (0.0, 0.2, 0.3, 0.4 and 0.5%) by weight of cement, cement contents (450, 500 and 550 kg/m³), type aggregates (steel slag, crashed dolomite, gravel) and fine materials (content and type). All concrete mix contains high-range water reducing 4% by weight of cement. The fine to coarse aggregate was 1: 1. The concrete mixtures were tested for slump flow, blocking Ratio, GTM screen stability, air content, weight loss method that is the plunge test CRDC61 which is widely used in North America, and compressive strength. Compressive strengths were evaluated at 7 and 28 days’ age for under-water casting as well as air casting conditions. Test results indicated that the use of an AWA facilitates the production of self-flowing underwater concrete with the added benefit of lower washout loss.