REPORT ON EXPERIMENTS ON EXTENSIBILITY OF CONCRETE

A STUDY WAS CONDUCTED TO FIND OUT WHAT HAPPEN TO SURFACES UNDER VARIOUS CONDITIONS AND ATTEMPT TO FIND MEANS OF INCREASING EXTENSIBILITY. THE MAIN FACTORS EXAMINED WERE CURING CONDITIONS AND THE EFFECT OF MESH REINFORCEMENT. PRIOR TO THE EXTENSIBILITY RESEARCH, A STUDY WAS MADE OF THE EFFECT OF CHANGE OF MOISTURE CONDITIONS AND TEMPERATURE UPON CONTRACTION AND EXPANSION AND THE WARPING AND PULLING OF BEAMS BY CHANGE OF CONDITION OF THEIR SURFACES. VALUES OF CONTRACTION AND EXPANSION WERE MEASURED AND EVIDENCE OF SURFACE CHECKING DUE TO DIFFERENCE OF CONDITION OF SURFACE. TESTS WERE MADE ON REINFORCED CONCRETE BEAMS UNDER THE USUAL LABORATORY PROCESS IN WHICH LOADS PROGRESSIVELY INCREASED TO RUPTURE, AND ALSO ON BEAMS UNDER REPEATED LOADS PRODUCING A FATIGUE ACTION. OBSERVATIONS WERE MADE TO EXTENSIONS AND DEFLECTIONS. THE FOLLOWING CONCLUSIONS ARE MADE: (1) THE GROSS CONTRACTION OF CONCRETE DUE TO SHRINKAGE DEPENDS UPON CURING AND SUBSEQUENT EXPOSURE, UPON THE QUALITY AND QUANTITY OF THE CEMENT AND OTHER FACTORS TO BE EVALUATED IN EACH CASE, (2) THE EXTENSIBILITY OF CONCRETE SURFACES BEFORE FISSURES APPEARS, DEPENDING AS IT DOES ON SEVERAL FACTORS, SHOWS MICROSCOPIC FISSURES 0.001%, AND FOR FISSURES VISIBLE TO THE NAKED EYE, 0.018%, AND (3) THE COMPARISON OF SURFACE CONDITIONS WITH RESPECT TO DEVELOPMENT OF FISSURES IN BEAMS STORED INSIDE A SHED AND EXPOSED TO THE WEATHER IS PRESENTED IN A TABLE. A COMPARISON OF THE EFFECTS OF PROGRESSIVE AND FATIGUE LOADING SHOWED THAT THE ULTIMATE EXTENSIBILITY WAS REACHED AT APPROXIMATELY THE SAME ELONGATION OF THE CONCRETE SURFACE WHETHER THIS ELONGATION RESULTED FROM SINGLE MAXIMUM LOAD ONCE APPLIED OR A SMALLER LOAD APPLIED A NUMBER OF TIMES. THE APPEARANCE OF FINE MICROSCOPIC CRACKS DOES NOT SEEM TO BE POSTPONED BY A MESH REINFORCEMENT BUT IN THE CASE OF FISSURES VISIBLE TO THE NAKED EYE, THE APPEARANCE OF THE FISSURES SEEMED TO BE POSTPONED. MESH REINFORCEMENT SEEMS TO AMELIORATE THE CONDITIONS OF THE SURFACE THAT ARISE FROM DEFECTIVE CURING.

  • Supplemental Notes:
    • Vol 5, Pt 1, PP 112-118, 1 FIG, 3 TAB
  • Authors:
    • Hatt, W K
  • Publication Date: 1926

Media Info

  • Monograph Title: Proceedings of the Fifth Annual Meeting of the Highway Research Board Held at Washington, D.C. December 3-4, 1925. Part I: Reports of Research Committees and of Special Investigations
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00209249
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Nov 9 1970 12:00AM