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Kinetic and morphological differentiation of Ettringites in plain and blended Portland cements using Metakaolin and the ASTM C 452-68 test. Part I: kinetic differentiation

Materiales de Construccion. 2008;58(292):45-66

 

Journal Homepage

Journal Title: Materiales de Construccion

ISSN: 0465-2746 (Print); 1988-3226 (Online)

Publisher: Consejo Superior de Investigaciones Científicas

LCC Subject Category: Technology: Electrical engineering. Electronics. Nuclear engineering: Materials of engineering and construction. Mechanics of materials

Country of publisher: Spain

Language of fulltext: Spanish, English

Full-text formats available: PDF, HTML, XML

 

AUTHORS


Talero, R.

EDITORIAL INFORMATION

Double blind peer review

Editorial Board

Instructions for authors

Time From Submission to Publication: 48 weeks

 

Abstract | Full Text

In this first part of the study, the results obtained in prior research with XRD and SEM, as well as the Le Chatelier-Ansttet test were confirmed with the ASTM C 452-68 test. To this end, 20%, 30% and 40% metakaolin (MK) was added to ten Portland cements, six OPCs and four SRPCs. Both the ten plain PCs and the 30 metakaolin (MK) blends were tested for two years under ASTM C 452-68 specifications, determining not only the percentage increase in length, ΔL(%), of the specimens, but also the sulphate content in the curing water. Other parameters studied included: chemical analysis of the cementitious materials used and specific properties of some of the cements tested.<br /><br />The experimental results, ΔL(%) versus time, re-confirmed that the formation rate of ettringite from the reactive alumina, Al<sub>2</sub>O<sub>3</sub><sup>r-</sup>, present in the pozzolan must be substantially higher than the formation rate of ettringite from the C3A present in the PC. This was verified by the variation of the sulphate content in the specimen curing water throughout the test. In light of those findings, in this article these two types of ettringite are denominated rapid forming ettringite or ett-rf, and slow forming ettringite or ett-lf.<br><br>En esta Parte I de la investigación, se han logrado verificar mediante el ensayo ASTM C 452-68, los resultados obtenidos en anteriores investigaciones realizadas con DRX y SEM y el ensayo Le Chatelier-Ansttet. Para ello, a 10 cementos Portland –6 CPO y 4 CPRS– se les añadió 20%, 30% y 40% de metakaolín (MK). Tanto los 10 CP como los 30 de sus mezclas con metakaolín (MK), se ensayaron durante 2 años, mediante dicho método ASTM C 452-68, y a sus probetas no sólo se les determinó su incremento porcentual de longitud, ΔL(%), sino además, el contenido de sulfatos de sus aguas de conservación. Otras determinaciones complementarias fueron: análisis químico de los materiales cementiceos utilizados y propiedades específicas de algunos cementos ensayados.<br /><br />Los resultados experimentales, ΔL(%) frente al tiempo, han confirmado de nuevo que la velocidad de formación de la ettringita de origen alúmina reactiva, Al<sub>2</sub>O<sub>3</sub><sup>r-</sup>, de las puzolanas, tiene que ser considerablemente mayor que la velocidad de formación de la ettringita de origen C3A de los CP, lo que ha sido verificado por la evolución durante todo el ensayo, del contenido de sulfatos de las aguas de conservación de las probetas. Debido a ello, se ha propuesto denominar a ambos tipos de ettringitas, ettringita de rápida formación, ett-rf, y ettringita de lenta formación, ett-lf, respectivamente.