Quality characteristics of fine aggregates and controlling their effects on concrete

For the aggregate producer, the concrete aggregates are end products, while, for the concrete manufacturer, the aggregates are raw materials to be used for mix designs and successfull concrete production. The aim of this study was to identify which fine aggregate characteristics are important, and additionally to relate the extent of the effect that the aggregate has on the concrete as compared against the effect of the changes in mix design. The testing programme contained six different mix design in which 21 fine aggregate products were studied in 215 castings. The mix designs consisted of two cements amounts (300 or 350 kg/m 3 ) corresponding to low and high paste volumes, with three admixture possibilities : non admixture, superplasticizer or air-entraining agent. The result of the experiments show that the effect of the fine aggregate characteristics on the flow value was greater thant the effect of the cement amount. A program for predicting the interaction between the fine aggregate and concrete was developed. The Bayesian method was used for statistical processing, and non-parametric non-linear Gaussian process models were applied for the interaction models. The program includes four concrete properties : flow value, air%, bleeding and compressive strength. The moste important fine aggregate characteristics in the models are : shape and particle porosity related semi-coarse fraction parameters (flow value and air%), flakiness and Los Angeles value of the semi-coarse fraction (compressive strength) and particle porosity of the semi-coarse and surface area of the fines fractions (bleeding). As an example of the model predictions, six different fine aggregate combinations were modelled : two gravel products representing past and future gravel types and four crushed rock products representing different strength qualitites and shape characteristics.