Influence of Superplasticizer oin the Volume Stability of Hydrating Cement Pastes at an Early Age

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Title: Influence of Superplasticizer oin the Volume Stability of Hydrating Cement Pastes at an Early Age

Author(s): B. Bissonnette, J. Marchand, C. Martel, and M. Pigeon

Publication: Special Publication

Volume: 206

Issue:

Appears on pages(s): 167-188

Keywords: cement, early-age, hydration, Le Chatelier contraction, self-desiccation, shrinkage, superplasticizer

Date: 4/1/2002

Abstract:
The influence of superplasticizer on the chemical (total) and autogeneous (external) shrinkage of hydrating cement pastes was investigated. Three different commercial CSA Type 10 cemeents were tested. Test variables also included type of superplasticizer (melamine-based and naphtalene-based) and dosage in admixture (three different dosages). All neat paste mixtures were prepared at a water/cement ratio of 0.35. Chemical shrinkage measurements were carried out using the classical dilatometric method initially developed by Le Chatelier. Autogeneous shrinkage measurements were performed according to the immersion method. All tests were performed in a temperature-controlled bath kept at 20 degrees C. Test results indicate that the dosage in admixture influences the kinetics and magnitude of both chemical shrinkage and autogeneous shrinkage, especially during the first 24 hours. Beyond that period, the overall effects of dosage were observed to be less pronounced. Data also emphasize the potentioal importance of the type of superplasticizer upon early volume changes. Though the investigated cements are known to sometimes exhibit quite different early-age behaviors in the field, no significant differences were observed as far as chemical shrinkage and autogeneous shrinkage are concerned.