This paper indicates areas that contribute to the greatest errors in concrete compression testing and presents the results of a testing machine survey carried out by the New Zealand Concrete Research Association. Errors are divided into those related to the testing machine itself and those related to the testing process. The former include errors in indicated load which can occur as a result of infrequent checking particularly in exceptionally flexible machines; errors due to platens including their wear as a result of insufficient thickness and the restraining effect of their spherical seatings. Illustrations are given of the effect of extreme ballseat conditions on concrete specimens; fully locked seatings showing a diagonal shear failure distinct from that given by fully lubricated seatings. Testing errors can arise from defects in the test specimens, the alignment of the specimen in the machine and failure to clean the bearing face before placing the specimen. They can be reduced by allowing the ram to return fully between tests and by the use of load pacers. 67 of the 100 questionnaires used in the survey were returned. Only 15 of the machines covered were commissioned after 1965 when the NZ standard included a requirement for locking under load. The radius of spherical seats ranged from 50 mm to 244 mm. Capacity varied from 40000 lb to 600000 lb with a variety of units (only 3 were SI units). Only 8 machines were entirely manual, load pacers were present on 36 machines; 55 machines were capable of testing 12 in. by 6 in. diameter concrete cylinders. Part 2 of the paper will cover a limited comparative testing program that has been carried out by the NZCRA. /TRRL/

  • Availability:
  • Corporate Authors:

    New Zealand Portland Cement Association

    Securities House, 126 The Terrace, P.O. Box 3644
    Wellington,   New Zealand 
  • Authors:
    • Boult, B F
    • Ball, M E
  • Publication Date: 1976-9


  • English

Media Info

  • Features: Photos; References;
  • Pagination: p. 11-13
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00149902
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Jun 17 1977 12:00AM