Mathematical modelling of the composition of a high-strength composite concrete containing blended carbonate additive

A new high-strength concrete has been developed on the basis of the utilization of the blended carbonates as an active additive (BCA). The main technological features are the preliminary mechanical-chemical activation of this natural mineral product and the stage method of production. A three-parameter polynomial model has been developed for determining the amount of the main formulation components - Portland cement, BCA and water/cement ratio by evaluation of their influence on the changes of the compressive strength for one-year time period of the hardening. The experimental plan contains 27 tests. The regression equations have been calculated for five ages. The obtained regression coefficients reflecting the trend and the effect of the three factors on the output data during the investigated period have been analyzed. The compressive strength depending on two factors has been plotted for the ages of 28 and 365 days, the value of the third factor being constant. They are important for the construction practice and they display the whole spectrum of possibilities for variation of the formulation parameters, achieving at the same time the specified design strength. Key words: high-strength composite concrete, blended carbonate additive, polynomial model, regression, compressive strength