Comparative XRD analysis ettringite originating from pozzolan and from portland cement

✍ Scribed by Rafael Talero

• Book ID: 103001226
• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 479 KB
• Volume: 26
• Category: Article
• ISSN: 0008-8846
• DOI: 10.1016/0008-8846(96)00092-0

✦ Synopsis

7 .'he ettringite is often formed when concrete is attacked by sulphatic waters. In this investigation, a semi-quantitative analysis and study of the ettringite (28 = 9.08") in the solid phase of the Fratini test was made by XRD. The cements P-1 (14.11% CA) P-31 (7.6% C,A) and PY-6 (0.00% C,A), five pozzolans, D,O,A,C and M and five mixed cements PUZC 70/30, PYd/D, 0, A, C or M, respectively, were used. These PUZC were mixed with gypsum in proportions to give 7.0% or 2 1 .O% SO,. Identical analysis and study was made of the corresponding mixtures of each pozzolan plus Ca(OH), and gypsum.

The experimental results have demonstrated that 1. The formation rate of ettringite from pozzolan, is notably higher than the formation rate of ettringite from OPC. 2. The topochemical mechanism of the etrringite formation can proceed when ALL the necessary reactive materials, including the "reactive alumina," A&O,, [or better perhaps, "aluminate anion" or "amorphous alumina" (tetra-or penta-coordinated alumina)], are in the solution.