PREDICTION OF CONCRETE STRENGTH FROM THE CALCULATED POROSITY OF THE HARDENED CEMENT PAST

IT IS GENERALLY ACCEPTED THAT WHILE ORDINARY TYPE I CEMENT COMBINES WITH ONLY APPROXIMATELY 23 PERCENT WATER (BY WEIGHT), AT LEAST 38 PERCENT WATER IS NEEDED FOR COMPLETE HYDRATION, AND APPROXIMATELY 48 PERCENT WATER IS NEEDED FOR PROPER MIXING AND PLACING OF THE CONCRETE. THIS EXCESS WATER, TOGETHER WITH ANY ENTRAPPED OR ENTRAINED AIR, REMAINS IN THE CEMENT PASTE DURING THE MIXING AND HARDENING PROCESS AND CONTRIBUTES TO THE OVERALL POROSITY OF THE CEMENT PASTE AND THE CONCRETE. IT IS ALSO ACCEPTED THAT THE VOIDS CREATED BY THE EXCESS WATER AND AIR REDUCE THE STRENGTH OF THE RESULTING CONCRETE. THEREFORE, VARYING THE POROSITY OF THE PASTE FOR A GIVEN WATER-CEMENT RATIO WILL VARY THE CONCRETE STRENGTH. THE ACI RECOMMENDED PRACTICE FOR SELECTING PROPORTIONS FOR CONCRETE TAKES THE FOREGOING INTO ACCOUNT IN DEVELOPING RECOMMENDED MIX PROPORTIONS FOR GIVEN CONDITIONS. A SIMPLIFICATION OF THE PROCEDURE FOR DETERMINING THESE MIX PROPORTIONS IS DEVELOPED, BASED ON THE CALCULATED POROSITY OF THE HARDENED CEMENT PASTE, AND PRESENTED IN GRAPHICAL AND NOMOGRAPHIC FORM. A SPECIFIED STRENGTH IS SHOWN TO BE OBTAINABLE FOR A RANGE OF AIR CONTENTS AND WATER CONTENTS OR WATER-CEMENT RATIOS.

• Authors:
  • Sandstedt, C E
  • Ledbetter, W B
  • Gallaway, B M
• Publication Date: 1973-2

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 115-6
• Serial:
  • Am Concrete Inst Journal & Proceedings
  • Volume: 70
  • Issue Number: 2

Subject/Index Terms

• TRT Terms: Air entrained concrete; Air entraining cement; Compressive strength; Graphics; Mix design; Nomographs; Porosity; Void ratios; Water cement ratio
• Uncontrolled Terms: Graphical analysis
• Old TRIS Terms: Void
• Subject Areas: Highways; Materials;

Filing Info

• Accession Number: 00214249
• Record Type: Publication
• Files: TRIS
• Created Date: Aug 20 1973 12:00AM