INVESTIGATION OF THE FORMATION OF NEW COMPOUNDS AT THE COMMENCEMENT OF THE HYDRATION OF CLINKER AND CEMENT

THE INVESTIGATIONS RELATE TO THE FORMATION OF NEW HYDRATE COMPOUNDS IN THE SYSTEM CLINKER-WATER, CEMENT-WATER AND CLINKER-GYPSUM-WATER, BEGINNING IMMEDIATELY AFTER THE ADDITION OF WATER. IN THE HYDRATION OF CLINKER IT WAS SHOWN, IN COMPARISON WITH THE UNHYDRATED CLINKER SURFACE, THAT THE HYDROLYSIS AND HYDRATION COMMENCE WITHIN A VERY SHORT TIME AFTER THE ADDITION OF WATER AND THAT HEXAGONAL PLATELETS OF UP TO ONE MILLIMETER EDGE LENGTH ARE FORMED. BESIDES CALCIUM HYDROXYDE, THESE STRUCTURES CONSIST OF TETRACALCIUM ALUMINATE HYDRATE. IN ADDITION, CUBIC CALCIUM HYDROGARNETS PROBABLY OCCUR. IN THE HYDRATION OF CLINKER AND GYPSEOUS STONE A TOTALLY DIFFERENT PICTURE OF SURFACE CONDITION EMERGED. AFTER A SHORT HYDRATION PERIOD HEXAGONAL COLUMNS CONSISTING OF ETTRINGITE AND OTHER, MAINLY HEXAGONAL, CRYSTALS OF CALCIUM HYDROXIDE ARE TO BE DISTINGUISHED. IN THE PRESENCE OF HEMHYDRATE IN PORTLAND CEMENT C THE FORMATION OF ETTRINGITE CAN BE CLEARLY STUDIED. ETTRINGITE CRYSTALS ARE TO BE DETECTED IN A GEL MATRIX AFTER 30 SECONDS' HYDRATION. THE SIZE OF THE STRUCTURES CONSTITUTING THIS GEL VARIES BETWEEN 80 AND 250 A AND HAS AN AVERAGE VALUE OF 200 A, WHICH IS IN GOOD AGREEMENT WITH THE THEORETICAL VALUE OF 160 A CALCULATED BY POWERS. THIS GEL WAS STILL OBSERVABLE AFTER A HYDRATION TIME OF TWO MINUTES. THE GREATER PART OF THE SURFACE WAS NOW, HOWEVER, COVERED WITH ETTRINGITE CRYSTALS. THE COMPACT HABIT OF THIS COMPOUND IS ATTRIBUTABLE TO THE MAGNITUDE OF THE SULFATE ION CONCENTRATION IN THE DISSOLVED PHASE OF THE CEMENT PASTE. IT WAS POSSIBLE DEFINITELY TO IDENTIFY THE ETTRINGITE BY MEANS OF ELECTRON DIFFRACTION. AFTER A FURTHER TWO MINUTES, I.E., AFTER A HYDRATION TIME OF 4 MINUTES, THE SURFACE CONDITION HAD NOT SIGNIFICANTLY ALTERED, BUT NOW THE GEL FORMATION WAS MORE APPARENT. FIFTEEN MINUTES AFTER THE CEMENT WAS MIXED WITH WATER THE ETTRINGITE CRYSTALS WERE ONLY SPORADICALLY OBSERVED, THE GEL HAD NOW SPREAD OVER THE ENTIRE SURFACE, THE COLUMNAR CRYSTALS BEING EMBEDDED IN IT. SPORADICALLY THESE COLUMNS PROTRUDE FROM THE SURFACE OF THE GRAIN AND OFTEN OCCUR IN CLUSTERS. THE FRESH INFORMATION YIELD BY THESE INVESTIGATION CONFIRM THE OBSERVATIONS MADE YEARS AGO CONCERNING THE HEAT EFFECT OF TWO REACTIONS WHICH CAN NOW BE INTERPRETED IN TERMS OF THE SPONTANEOUS FORMATION OF ETTRINGITE AND THE HYDRATION AND HYDROLYSIS OF THE CALCIUM SILICATES. /AUTHOR/

• Supplemental Notes:
  • Vol19, No 9, PP 402-411
• Authors:
  • Schwiete, H E
  • Niel, E
• Publication Date: 1966-9

Media Info

• Serial:
  • Zement-Kalk-Gips

Subject/Index Terms

• TRT Terms: Calcium compounds; Cement; Chemical compounds; Clinkers; Crystallography; Ettringite; Forming; Gels; Gypsum; Hydrates; Hydration; Hydrolysis; Portland cement; Silicates; Water
• Old TRIS Terms: Compounds
• Subject Areas: Highways; Materials;

Filing Info

• Accession Number: 00212503
• Record Type: Publication
• Files: TRIS
• Created Date: Sep 1 1970 12:00AM