VARIATIONS IN CEMENT

CEMENT PRODUCERS WORK WITH BASIC NATURAL INGREDIENTS WHICH WILL VARY WIDELY SO THAT IT IS NATURAL THAT VARIATIONS OCCUR IN THE FINISHED CEMENT PRODUCED. THE EFFECTS OF CEMENT QUALITY ARE APPARENT IN CONCRETE, BOTH IN THE FRESH AND IN THE HARDENED STATE. RATE OF HARDENING, TIME OF SET, FALSE SET, EXCESSIVE BLEEDING, FINENESS AND OTHER CHARACTERISTICS HAVE A BEARING ON PLACEABILITY AND WORKABILITY. GYPSUM IS USED ALMOST UNIVERSALLY TO RETARD THE QUICK-SETTING CHARACTERISTICS OF PORTLAND CEMENT. BYT GYPSUM CAN REVERSE ITS ROLE AS A RETARDER WHEN EXCESSIVE AMOUNTS ARE GROUND IN WITH THE CEMENT CLINKER. CEMENT STORAGE CONDITIONS HAVE A BEARING ON SETTING TIME. FALSE SETTING CAN BE AGGRAVATED BY UNUSUALLY SHORT MIXING TIME. ALTHOUGH FALSE SETTING CAN BE ALLEVIATED BY CONTINUED MIXING OR VIBRATION OF THE CONCRETE TOGETHER WITH THE ADDITION OF WATER, THE RESULTING CONCRETE OFTEN EXHIBITS LOW STRENGTHS, INCREASED CRACKING, ERRATIC AIR CONTENT, LOWERED DURABILITY, AND POORLY FORMED AND FINISHED SURFACES. A NUMBER OF FACTORS AFFECTING THE AMOUNT AND RATE OF BLEEDING EXPERIENCED WITH THE CONCRETE MIX ARE DISCUSSED. BRAND OF CEMENT CAN HAVE A NOTICEABLE BEARING ON THE AMOUNT OF AIR ENTRAINED ON A GIVEN QUANTITY OF AN AIR- ENTRAINING MIXTURE. ALTHOUGH CEMENT ACCOUNTS FOR ONLY ABOUT TEN PERCENT OF CONCRETE BY VOLUME, IT TYPICALLY CONSTITUTES 25 TO 30 PERCENT OF THE COST OF THE CONCRETE MIXTURE. CONCRETE IS MOST OFTEN JUDGED BY THE STRENGTH IT DEVELOPS AND SINCE THE CEMENT IS ONE OF THE MOST IMPORTANT FACTORS DETERMINING STRENGTH DEVELOPMENT, IT FOLLOWS THAT THE QUANTITY AND QUALITY OF CEMENT HAVE AN IMPORTANT BEARING ON THE ECONOMICS AND THE ACCEPTABILITY OF CONCRETE.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/05490219
• Supplemental Notes:
  • Vol 12, No 11, PP 427-429, 1 FIG, 2 TAB
• Publication Date: 1967-11

Media Info

• Serial:
  • CONCRETE CONSTRUCTION
  • Publisher: CEMENT & CONCRETE ASSOCIATION OF NEW ZEALAND
  • ISSN: 0549-0219

Subject/Index Terms

• TRT Terms: Admixtures; Air entrainment; Bleeding; Cement; Concrete; Concrete curing; Concrete hardening; Concrete placing; Consistency; Economics; Fineness; Gypsum; Hardness; Industries; Physical properties; Portland cement; Quality control; Raw materials
• Uncontrolled Terms: Concrete properties; Quality
• Old TRIS Terms: Concrete consistency
• Subject Areas: Economics; Highways; Materials;

Filing Info

• Accession Number: 00212557
• Record Type: Publication
• Files: TRIS
• Created Date: May 1 1994 12:00AM