CURRENT FIELD RESEARCH PROGRAM ON SHOTCRETE

The field work is described and a preliminary evaluation is presented here of a comprehensive research program (conducted in an underground station of the Washington, D.C. subway) designed to evaluate the practical aspects of the behavior of conventional and experimental shotcretes (regulated-set shotcrete and steel fiber shotcrete). The project was planned to demonstrate the practicality of the experimental shotcrete for routine construction by using the normal crews and equipment available to the contractor. It was also intended to develop information on the experimental shotcrete for potential users. The need for a control of a conventional shotcrete led to inclusion of research on conventional shotcrete. Coarse aggregate mixes of regulated set shotcrete and steel fiber shotcrete were shot successfully in the dry-mix process by a civil engineering contractor using on-site crews and equipment. The results of rebound tests showed that the rate of rebound for about the first 0.5 inch was more than five times the rate of rebound for the remainder of the layer. There was a greater percentage of coarse particles in the rebound than in the wall. A high percentage of steel fibers rebounded. A homemade long nozzle consisting of a single water ring about 14 feet behind the tip of the hose appeared to provide more uniform mixing than other nozzles. At the end of a few hours the compressive strength of reg-set shotcrete was 3 to 10 times the compressive strength of conventional shotcrete. After 29 days the compressive strengths of conventional and reg-set shotcrete were generally greater than 5,000 psi but the compressive strength of the steel fiber shotcretes was somewhat less. However, the ratio of flexural strength to compressive strength was much higher for steel fiber shotcrete. The steel fiber shotcrete exhibited considerable post-crack resistance.

Media Info

  • Features: References;
  • Pagination: p. 330-350

Subject/Index Terms

Filing Info

  • Accession Number: 00263684
  • Record Type: Publication
  • Report/Paper Numbers: SP-45 Conf. Proc
  • Contract Numbers: H0111881
  • Files: TRIS
  • Created Date: Dec 19 1981 12:00AM