THE SPECIFICATION OF CONCRETE STRENGTH. PART III THE DESIGN OF ACCEPTANCE CRITERIA FOR THE STRENGTH OF CONCRETE

THE TYPES OF CRITERIA WHICH ARE AVAILABLE FOR THE JUDGEMENT OF COMPLIANCE WITH SPECIFICATION OF THE RESULTS OF STRENGTH-TESTS ON CONCRETE ARE REVIEWED. ALL ACCEPTANCE JUDGEMENTS INVOLVE A RISK TO THE PRODUCER THAT GOOD CONCRETE MAY BE JUDGED UNACCEPTABLE AND A RISK TO THE CONSUMER THAT POOR CONCRETE MAY NOT BE DETECTED. IN FAIRNESS THE PRODUCER'S RISK MUST BE SET AT A CONSTANT LEVEL REGARD- LESS OF THE AMOUNT OF TESTING, THEREBY GIVING REASONABLE ASSURANCE THAT WHEN MATERIAL OF THE SPECIFIED QUALITY IS PRODUCED IT WILL BE ACCEPTED. THE PROTECTION GIVEN TO THE CONSUMER THEN DEPENDS ON THE AMOUNT OF TESTING AND THE EFFICIENCY OF THE ACCEPTANCE CRITERION. CRITERIA BASED ON A CLASSIFICATION BY ATTRIBUTES ARE GENERALLY THE LEAST EFFICIENT BUT ARE SIMPLE TO OPERATE. THE CRITERION USUALLY TAKES THE FORM 'ACCEPT IF, OUT OF A TOTAL OF N RESULTS, NOT MORE THAN F ARE DEFECTIVE'. THE ALTERNATIVE IS TO USE A VARIABLES CRITERION WHICH TAKES ACCOUNT OF THE VARIABILITY OF THE RESULTS BY USING THEIR ACTUAL MAGNITUDES IN THE FORM 'ACCEPT IF: L IS LESS THAN OR EQUAL TO M(N) - K(N) X S(N) WHERE L IS THE SPECIFIED STRENGTH, M THE AVERAGE AND S THE STANDARD DEVIATION OF N RESULTS AND K(N) IS A FACTOR DEPENDING ON THE SPECIFIED PROPORTION DEFECTIVE, THE PRODUCER'S RISK DESIRED AND THE NUMBER OF TESTS'. IT IS POINTED OUT THAT K(N) IS NOT THE SAME AS THE FACTOR K THAT IS USED IN THE DESIGN OF A CONCRETE MIX. IT IS SUGGESTED THAT THE MOST EFFECTIVE WAY OF JUDGING CONCRETE STRENGTHS WILL BE THROUGH THE USE OF A SERIES OF CRITERIA AT CONSTANT PRODUCER'S RISK WHICH ENABLE UNSATISFACTORY MATERIAL TO BE DETECTED RAPIDLY WITH THE FINAL ACCEPTANCE DELAYED UNTIL 20 OR 30 TESTS HAVE BEEN OBTAINED AND THE CONSUMER'S RISK IS THUS REDUCED TO A REASONABLE LEVEL. /RRL(A)/

  • Supplemental Notes:
    • Rrl Rept Lr 301, 17 PP, 6 FIG, 6 REF
  • Corporate Authors:

    Road Research Laboratory /UK

    ,    
  • Authors:
    • MATHEWS, D H
    • METCALF, J B
  • Publication Date: 1970

Subject/Index Terms

Filing Info

  • Accession Number: 00213119
  • Record Type: Publication
  • Source Agency: Road Research Laboratory /UK
  • Files: TRIS, ATRI
  • Created Date: May 3 1971 12:00AM