Influence of cement properties in the reaction rate and mechanical behavior of concrete with high fl y ash content

Molina Bas, Omar I. and Moragues Terrades, Amparo and Gálvez Ruiz, Jaime and Guerrero Bustos, Ana (2011). Influence of cement properties in the reaction rate and mechanical behavior of concrete with high fl y ash content. In: "13th International Congress on the Chemistry of Cement", 03/07/2011 - 08/07/2011, Madrid, España.

Description

Title: Influence of cement properties in the reaction rate and mechanical behavior of concrete with high fl y ash content
Author/s:
  • Molina Bas, Omar I.
  • Moragues Terrades, Amparo
  • Gálvez Ruiz, Jaime
  • Guerrero Bustos, Ana
Item Type: Presentation at Congress or Conference (Article)
Event Title: 13th International Congress on the Chemistry of Cement
Event Dates: 03/07/2011 - 08/07/2011
Event Location: Madrid, España
Title of Book: Proceedings of 13th International Congress on the Chemistry of Cement
Date: 2011
Subjects:
Faculty: E.T.S.I. Caminos, Canales y Puertos (UPM)
Department: Ingeniería Civil: Construcción
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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Abstract

The use of fly ash (FA) as an admixture to concrete is broadly extended for two main reasons: the reduction of costs that supposes the substitution of cement and the micro structural changes motivated by the mineral admixture. Regarding this second point, there is a consensus that considers that the ash generates a more compact concrete and a reduction in the size of the pore. However, the measure in which this contributes to the pozzolanic activity or as filler is not well defined. There is also no justification to the influence of the physical parameters, fineness of the grain and free water, in its behavior. This work studies the use of FA as a partial substitute of the cement in concretes of different workability (dry and wet) and the influence in the reactivity of the ash. The concrete of dry consistency which serves as reference uses a cement dose of 250 Kg/m 3 and the concrete of fluid consistency utilized a dose of cement of 350 Kg/m 3 . Two trademark of Portland Cement Type 1 were used. The first reached the resistant class for its fineness of grain and the second one for its composition. Moreover, three doses of FA have been used, and the water/binder ratio was constant in all the mixtures. We have studied the mechanical properties and the micro-structure of the concretes by means of compressive strength tests, mercury intrusion porosimetry (MIP) and thermal analysis (TA). The results of compressive strength tests allow us to observe that concrete mixtures with cements of the same classification and similar dosage of binder do not present the same mechanical behavior. These results show that the effective water/binder ratio has a major role in the development of the mechanical properties of concrete. The study of different dosages using TA, thermo-gravimetry and differential thermal analysis, revealed that the portlandite content is not restrictive in any of the dosages studied. Again, this proves that the rheology of the material influences the reaction rate and content of hydrated cement products. We conclude that the available free water is determinant in the efficiency of pozzolanic reaction. It is so that in accordance to the availability of free water, the ashes can react as an active admixture or simply change the porous distribution. The MIP shows concretes that do not exhibit significant changes in their mechanical behavior, but have suffered significant variation in their porous structure

More information

Item ID: 12546
DC Identifier: http://oa.upm.es/12546/
OAI Identifier: oai:oa.upm.es:12546
Deposited by: Memoria Investigacion
Deposited on: 07 Aug 2012 09:26
Last Modified: 05 Jun 2018 14:12
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