Packing of aggregates : An alternative tool to determine the optimal aggregate mix

Concrete mix designs include a number of subdesigns of, for example, the aggregate mix. The aggregates are usually selected and combined according to simple mix design rules, which requires each of the aggregates to be graded. This procedure limits the use of natural aggregate grades and does not always lead to the best quality of concrete. The selection and combination of the aggregates has a dominating influence on the quality and price of the concrete and should receive more thorough attention. An alternative mix design may often lead to a better and cheaper concrete. An alternative approach for the aggregate selection and combination is to aim for the aggregate mix that has the lowest void content or the maximal packing degree. This will lead to the lowest cement consumption, porosity, and shrinkage and thus the concrete with the highest performance and the lowest price. This paper presents a model that has been used for more than 5 years on a large number of industrial projects. The model is verified by comparison with more than 800 test results from different sources as being reliable for large ranges of materials.