A major ready mix concrete company had been producing concrete with a cement content of 275kg/m3 to produce an average strength of 25.6MPa with a CoV of 10.9%. The aggregates were produced by primary jaw crusher, secondary cone crusher and shaped by a hammer mill as the tertiary crusher. With the introduction of pumpable mixes, it was found that the aggregate supplied was not suitable due to poor particle shape and sharpness of both the coarse and fine aggregate.
The aggregate producer installed a Barmac VSI in place of the hammer mill to produce a more cubical product. After extensive tests a mix design for the nominal 21MPa mix was now using 255kg/m3 giving an average strength of 24.8MPa with a CoV of 9.4%. This represents a direct cement saving of 7.3% and more confidence in the consistency of the final product.
Using a coarse aggregate containing cubical aggregate offers a significant compressive strength advantage over a poorly shaped aggregate. This will reduce the cement content required by the ready mix producer to obtain a specific compressive strength, reducing their costs.