Title: Influence of Negative Temperatures on Water Permeability of Concrete

Author(s): Anatoly Vovk and Irina Vovk

Publication: Symposium Paper

Volume: 326

Issue:

Appears on pages(s): 85.1-85.8

Keywords: antifreeze admixtures, microstructure, negative temperatures, ready-mix concrete, water permeability

DOI: 10.14359/51711068

Date: 8/10/2018

Abstract:

In countries with severe climate, in winter period ready-mix concrete is exposed to cooling down during transportation and placing before heat impact. To eliminate negative influence of negative temperatures, antifreeze admixtures are used purposely. Russian Standard GOST 24211-2008 stipulates antifreeze admixtures performance testing both at short negative temperature exposure (so called “warm” concrete) and for permanent hardening at temperatures below zero. In both cases the only performance criteria is concrete compressive strength. On the other side, in European standards such tests are not provided as a rule.

Statistically, nowadays antifreeze admixtures are used in very low dosage (~2÷3% of liquid commercial products for up to -25°С for “cold” concrete and even less for “warm” concrete technology). It was established, that, while using such amount of antifreeze admixtures, even short term exposure to negative temperatures (without concrete freezing) can adversely effects concrete`s water permeability. On examples on set of concretes with different dosages of common antifreeze admixture (up to maximum level recommended by “Temporary Construction Standards” 46-96 for -5÷-15°С range), main factors that influence on water permeability of concretes hardened under negative temperatures were observed. The formation of a fine microstructure due to the pozzolanic additive increases the resistance of the concrete to freezing, but the stability of the concrete water permeability can be achieved only by ensuring near-zero ice formation in the pore liquid.