DEVELOPMENT OF A DEVICE FOR CONTINUOUS AUTOMATIC MONITORING OF CONSOLIDATION OF FRESH CONCRETE

Quality of portland cement concrete can be increased if water/cement ratios are reduced; however, this increase is only achieved if concrete is adequately consolidated. This study was conducted to develop a device to permit continuous automatic monitoring of the degree of consolidation during pavement construction. A literature search identified several candidate techniques, the most feasible being a nuclear backscatter technique to measure concrete density. A prototype instrument was developed with a 500 mCi source of Cesium137 and a sodium iodide/photomultiplier sensing unit. The sensor head is located 1 inch (25.4 mm) above the concrete. It is moved back and forth across the width of the pavement by a traversing mechanism mounted to the back of a slip-form paver. Density is recorded on chart paper. The CMD (Consolidation Monitoring Device) is capable of sensing and displaying changes in density while traversing over the pavement surface at 17 fpm (0.086 m/s). It can duplicate core density measurements within a plus or minus 2-1/4 pcf (plus or minus 36 kg/cu m) confidence range (95% confidence limits). /FHWA/

• Corporate Authors:

  Rexnord, Incorporated

  Corporate Research & Development Group, 5101 W Beloit Road
  Milwaukee, WI  United States  53214
• Authors:
  • Lee, P L
  • Eggert, G J
• Publication Date: 1978-3

Media Info

• Pagination: 100 p.

Subject/Index Terms

• TRT Terms: Backscattering; Consolidations; Density; Development; Measuring instruments; Nuclear phenomena; Nuclear powered ships; Portland cement concrete; Research
• Uncontrolled Terms: Cesium; Research and development
• Subject Areas: Highways; Materials; Research;

Filing Info

• Accession Number: 00179514
• Record Type: Publication
• Source Agency: National Technical Information Service
• Report/Paper Numbers: FHWA-RD-78- 27, FCP 34F3-222
• Contract Numbers: DOT-FH-11-8588
• Files: TRIS
• Created Date: Aug 27 1978 12:00AM