EFFECT OF ADMIXTURES ON THE COMPOSITION OF THE LIQUID PHASE AND EARLY HYDRATION REACTIONS IN PORTLAND CEMENT PASTES

THE CHEMICAL EFFECTS OF VARIOUS ADMIXTURES HAVE BEEN STUDIED BY AN EXAMINATION OF THE COMPOSITION OF THE LIQUID PHASE WITH RESPECT TO ALKALINITY, CALCIUM, AND SULPHATE IN DIFFERENT PORTLAND CEMENT PASTES WITH WATER/CEMENT RATIOS IN THE RANGE 0.5-2.0 AT DIFFERENT PERIODS OF HYDRATION VARYING FROM 2 MINUTES TO 7 DAYS. IT IS SHOWN THAT DIFFERENT ADMIXTURES INDUCE DIVERSE CHANGES IN THE SOLUTION COMPOSITION AND IN THE HYDRATION REACTIONS OF CEMENT. THE ALKALINITY OF THE SOLUTION INCREASES WITH ALKALI SALT ADMIXTURES, BECAUSE OF REACTION WITH CEMENT CONSTITUENTS, AND THIS MAY ENHANCE THE CORROSION-INHIBITING ACTION OF THESE PARTICULAR COMPOUNDS. WITH SUCROSE AND CALCIUM LIGNOSULPHONATE ADMIXTURES, THE CALCIUM CONCENTRATION INCREASES AS WELL AS THE ALKALINITY TO SOME EXTENT, POSSIBLY RESULTING IN A RETARDING INFLUENCE, AND THE TIME FOR WHICH SULPHATE IS PRESENT IN SOLUTION BECOMES PROLONGED OWING TO RETARDATION OF THE REACTION OF SULPHATE WITH CEMENT CONSTITUENTS. THE ACCELERATING ACTION OF A CALCIUM CHLORIDE ADMIXTURE ON CEMENT HYDRATION IS MAINLY ATTRIBUTED TO THE FACT THAT IT PRODUCES A HIGH CALCIUM CONCENTRATION DURING THE EARLY PERIOD OF HYDRATION OF CEMENT AND REDUCES THE ALKALINITY THROUGHOUT, THUS PROMOTING INCREASED HYDRATION OF THE CALCIUM SILICATE CONSTITUENTS OF CEMENT. /RRL/A/

• Supplemental Notes:
  • Topic Ii, REPT II/1, PP 5-29, 12 FIG, 2 TAB, 26 REF
• Authors:
  • Roberts, M H
• Conference:
  • Intl Symp Admix Mortar & Concr /Belg/
• Publication Date: 1967

Subject/Index Terms

• TRT Terms: Calcium chloride; Cement additives; Corrosion resistance; Hydration; Liquids; Pastes; pH value; Phase transitions; Portland cement; Sulfates; Water cement ratio
• Old TRIS Terms: Liquid phases
• Subject Areas: Highways; Materials;

Filing Info

• Accession Number: 00212848
• Record Type: Publication
• Source Agency: Road Research Laboratory /UK
• Files: TRIS
• Created Date: Jun 1 1970 12:00AM