Alteration of cement pastes by organic acids

Title: Alteration of cement pastes by organic acids
Author(s): A. Bertron, J. Duchesne, G. Escadeillas
Paper category : conference
Book title: International RILEM Symposium on Concrete Science and Engineering: A Tribute to Arnon Bentur
Editor(s): J. Weiss, K. Kovler, J. Marchand, and S. Mindess
Print-ISBN: None
e-ISBN: 2912143926
Publisher: RILEM Publications SARL
Publication year: 2004
Nb references: 16
Language: English

Abstract: Agriculture produces effluents, as liquid manure and ensilage effluents, that cause serious environmental problems. In order to limit this pollution, manure need to be stored in watertight silos often made of concrete. Manure contains organic acids which constitute a severe chemical aggression for concrete. This research aims at analyzing the alteration mechanisms of cement based materials stored in organic acids and determining the composition parameters of binders that influence the durability. Ordinary and blended Portland cement specimens were immersed for 18 weeks in an aggressive solution at pH 4 composed of a mix of 5 organic acids found in liquid manure. Chemical and mineralogical modifications in the pastes were analyzed by microprobe and xray diffraction respectively. Analyses were run from the sound to the altered zone. The altered depths and the mass losses variations of the samples were monitored over time. The alteration of the matrix occurs, for all the binders, by an almost total decalcification, the vanishing of the crystallized or amorphous hydrated phases and the probable formation of a silica gel, the presence of which allows limiting the kinetics of further alteration. The silicocalcic anhydrous grains are chemically modified although C4AF and slags grains keep their initial composition in the altered zone.

Online publication: 2004-03-25
Classification: Degradation
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/2912143926.068