Determination of Test Methods to Quantify the Effects of Organic and Inorganic Constituents in Silica Sand Used for Construction

Details

• Creators:
  Ferraro, Christopher C. ; Riding, Kyle A. ; Patel, Ashish D. ; Gordillo, José Ignacio Dávila ; Mueller, Timothy K.
• Corporate Creators:
  University of Florida, Gainesville. Engineering School of Sustainable Infrastructure and Environment (ESSIE)
• Contributors:
  Shoucair, John
• Corporate Contributors:
  Florida. Department of Transportation
• Subject/TRT Terms:
  AASHTO T 21 AASHTO T 71 Cement Construction Data Analysis Fine Aggregates Hydration Impurities Isothermal Conduction Calorimetry Modified Walkley-Black Organic Impurities Organic Materials Performance Measurement Sand Silica Sands Testing

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• Publication/ Report Number:
  BED31-977-30
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States ; Florida
• Edition:
  Final Report: June, 2024 - July, 2026
• Corporate Publisher:
  Florida. Department of Transportation
• Abstract:
  Florida-produced fine aggregates are generally of suitable quality, and deleterious effects associated with organic matter are uncommon. However, naturally occurring organic constituents can affect cement hydration and early-age strength development depending on their concentration, composition, and interaction with cementitious phases. The sands evaluated in this study contained relatively low organic contents, making establishment of a universal organic-content threshold impractical. FDOT currently uses AASHTO T 21 as the primary screening method for potentially deleterious organic impurities and requires AASHTO T 71 testing when screening results indicate concern. This framework should be maintained. AASHTO T 21 provides effective statewide screening, while AASHTO T 71 provides performance-based confirmation. However, AASHTO T 21 is qualitative, and AASHTO T 71 requires extended testing that can delay aggregate acceptance decisions. Neither elemental analysis nor the Modified Walkley-Black method demonstrated sufficient precision, consistency, or correlation with AASHTO T 21 to support statewide acceptance criteria. However, MWB may be used to establish mine-specific organic-carbon baselines, and isothermal calorimetry may be used to establish mine-specific hydration-response baselines. Deviations from these baselines may indicate the need for additional evaluation, including AASHTO T 71 testing. Organic-carbon contents below approximately 0.015% did not measurably affect hydration or compressive strength. Alkaline washing reduced measured organic content and increased pH but did not consistently improve strength. The ASTM C109 hand-tamped consolidation procedure is recommended for AASHTO T 71 mortar cube fabrication. Trace inorganic constituents, including phosphorus, did not produce measurable strength effects.
• Format:
  PDF
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:0a813c4e9f317787956027423c0c1f2603719c5d7f9a58213a4e95bce6e10ef3165b6e381a1aaadd04cbd77e22a02044a1bed566b1f4b1aeded002d81a1695a5
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/92909/dot_92909_DS1.pdf
• File Type:
  [PDF - 2.48 MB ]