Effect of Admixtures on the Performance of Anti-washout Concrete

Pouring underwater concrete has always been a challenge. It involves the use of a variety of techniques and equipment. Anti-washout concrete was introduced more than two decades ago to allow casting concrete underwater. This paper aims at investigating the effects of various mineral and chemical admixtures on the properties of underwater concrete. Performance-enhancing admixtures are used herein to produce quality concrete that can be used in the construction of submerged structures like harbors, bridges and other maritime projects as an alternative to the traditional methods. Concrete mixes were prepared involving different combinations of polypropylene fibers, nonionic cellulose ethers, high range water reducer, silica fume, fly ash, natural zeolite, limestone, and bentonite powder. Viscosity modifying agents and super-plasticizers were optimized to clearly study the effects of mineral admixtures. Each mix was poured from the surface of water and traveled 400 mm into the molds. The concrete was compacted under its own weight and no compaction energy was induced to examine the effect of flowability on self-compacting properties and washout loss. Fresh and hardened testing was conducted to examine durability, flowability, and washout resistance of concrete. The results suggest that adding rheology modifying admixture nonionic cellulose ethers (0.7–1.0%) combined with a dosage of the high range water reducer (5–11%) and maintaining a silica fume percentage of (12%) can result in a concrete mix that has good flowability and washout resistance. This is the first-time natural zeolite has been tested in anti-washout concrete. Results reveal that using a combination of silica fume along with natural zeolite can result in a relatively high-quality anti-washout concrete strength.