Effect of Water-Binder Ratio and Complex Organic-Mineral Additive on Properties of Concrete for Marine Hydrotechnical Constructions

Abstract

Large-scale construction of marine structures in the coastal and offshore areas of Vietnam requires the development of new compositions of hydrotechnical concrete and innovative technologies for the preparation of concrete mixes, as well as their transportation to the place of placement. A preliminary composition of heavy concrete was determined and its properties were studied. The effect of the water-binder ratio (W/B) and the effect of using the developed complex organo-mineral modifying additive consisting of fly ash (FA) of Vung Ang TPP, microsilica SF-90 (SF90) and polycarboxylate superplasticizer SR 5000F (SP) on the concrete properties. To process the obtained results, the method of mathematical planning of the experiment with the construction of a four-factor plan was used. As a result of the studies conducted, first-order regression equations were obtained depending on the objective functions - the mobility of the concrete mixture on the cone sediment, the compressive strength of concrete and the deformations of concrete on input factors - x1 (W/B), x2 (amount of SP), x3 (amount of FA) and x4 (amount of SF90). From the obtained regression equations, it follows that the water-binder ratio, as well as the content of superplasticizer, fly ash and microsilica in the composition of the additive have a significant impact on the mobility of concrete mixtures. When reducing W/B and the amount of FA, as well as the increase in the amount of SF90 (x4) concrete compressive strength in 28 days also increases. The result of this study showed the relative deformation of concrete also increases with an increase in the content of FA and reducing W/B and the amount of SF90. At the same time, the effect of the water-binder relationship is most pronounced. It can be assumed that, in the composition of the developed modifying additive, the particles FA and SF90 played the role of a kind of “sliding bearings” between the grains of cement, with which you can control the dispersion of cement and finely dispersed mineral grains in the concrete mixture, and hence its mobility and persistence construction sites in the coastal areas of Vietnam. In addition, SF90, containing 91.65% of amorphous silica, binds free calcium hydroxide to less soluble low-basic calcium silicate silicates, compresses the structure of concrete and increases its compressive strength.