Proportioning with Ground Limestone and Mineral Filler-Utilzation of Crushed Stone Mineral Filler (Microfines) in Ready Mixed Concrete (PDF)

Utilzation of Crushed Stone Mineral Filler (Microfines) in Ready Mixed Concrete (PDF)

Pdf Summary

The document discusses the utilization of crushed stone mineral filler, specifically #10 screenings, in ready-mixed concrete as presented at the ACI Fall Convention in Denver by Teck L. Chua from Vulcan Materials Company. #10 screenings are a type of aggregate with at least 65% passing through a #200 sieve (75 microns), and they commonly serve as a "wet" mineral filler blended with manufactured sand. The presentation explores the engineering properties of this material, covering its compressive and flexural strength, and shrinkage characteristics, as well as how it can be proportioned and adjusted in batch plants for concrete quality assurance.<br /><br />Research from the International Center for Aggregates Research (ICAR) involving 10 sources of #10 screenings with different geologies across the U.S. is highlighted. The findings indicate that each source fails the ASTM C 33 sand gradation band, but can be utilized effectively in concrete mix proportioning when combined with natural sand. Emphasis is placed on understanding the particle shape which varies depending on the geology and crusher type employed, suggesting a blending with natural sand for the best results.<br /><br />The document also outlines cost incentives and practical operational adjustments for batching, such as ensuring proper aggregate bin slope and managing moisture levels to prevent flow issues. For instance, #10 screenings require a 45-degree bin slope due to a higher angle of repose than natural sand. An "Air Cannon" may be used to fluidize the material when needed.<br /><br />Buyer caution is advised, noting that not all #10 screenings may be suitable due to clay content, particularly smectite clays detectable by measuring the Methylene Blue Value (MBV). Despite these concerns, with appropriate proportions and batch adjustments, #10 screenings can be effectively used in concrete mixtures.

Keywords

crushed stone

mineral filler

#10 screenings

ready-mixed concrete

ACI Fall Convention

compressive strength

flexural strength

concrete mix proportioning

particle shape

Methylene Blue Value