![]() As it continues to set, it holds sand and stone in suspension to eventually form hardened concrete. When blended, this liquid surrounds the aggregate particles and guides them through formwork between rebar and blockouts. Paste is cementitious materials, water, air and admixtures. The two most important for this discussion are aggregates and paste.Īggregates simply are the total amount of sand and stone in the mix. But there’s still an opportunity to optimize gradation by choosing the best coarse aggregate blend and by choosing the optimal coarse/fine proportions.” Less is best with pasteĬoncrete is defined by its individual materials such as fine and coarse aggregates, water and cementitious materials. ![]() Maybe they only have two aggregate bins, so they are limited to one stone and one sand. Terry Harris, director of technical services at GCP Applied Technologies, added: “Some producers are hesitant to look at combined aggregate gradation. Spending a little more on sand and stone blends to optimize gradations may result in overall decrease in costs of a cubic yard of concrete that could exceed that initial aggregate investment.” “Think about it in terms of price per cubic yard or price per finished structure. “Producers need to look beyond price per ton of aggregates,” said Paul Ramsburg, district manager at Sika USA. This additional analysis results in better fresh concrete workability and overall product quality while potentially saving money. However, instead of analyzing the traditional binary blends of fine and coarse aggregates discreetly, producers should go a step further and analyze the gradation of all aggregates together or – in other words – combined aggregate gradation. This one characteristic can control a product’s durability and sustainability while having a significant impact on the cost per yard. They must be clean, durable and free from deleterious material and supplied in gradations that fall within the parameters of the applicable standard, which typically is ASTM C33 – Standard Specification for Concrete Aggregates or AASHTO equivalents M80 and M6.Īggregate gradation significantly influences concrete quality. These natural particles are the backbone of every good, quality mix. These are all good considerations, but the mix component that occupies more than 70% of the concrete volume often is overlooked. When looking to make improvements on concrete mix design, it is natural to first gravitate to the water-to-cementitious materials ratio, cementitious materials type and amount, admixtures and air content. Size and shape of aggregate go a long way in defining what type of concrete will come from mix design
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