Volume 6, Issue 10 (November 2009)
Effects of Strength, Permeability, and Air Void Parameters on Freezing-Thawing Resistance of Concrete with and Without Air Entrainment
The present research is aimed at investigating effects of concrete properties, particularly concrete rapid chloride permeability, strength, and air void parameters, on freezing-thawing (FT) resistance. In this study, concrete mixtures are made with different types of cement (Types I with 15 % class C fly ash and Type IP cements), different water-to-binder ratios (w/b=0.25, 0.35, 0.45, and 0.55), and with or without air entraining agent. The 28-day compressive strength, rapid chloride permeability, and FT durability of the concrete are determined according to ASTM C873, C1202, and C666A, respectively. The air void parameters of the concrete are measured with air void analyzer, Rapid Air, and porosity (ASTM C642) tests. The results indicate that although concrete made with a low w/b (≤0.35) has low rapid chloride permeability (≤1320 C), it generally still requires proper air entrainment for a desirable FT resistance (with a durability factor of ≥85 %), except for the concrete having very low rapid chloride permeability (520 C) and very high 28-day compressive strength (88 MPa or 12 760 psi). For the non-air-entrained concrete studied, there are clear relationships between FT durability and porosity, w/b, and permeability. However, such relationships do not exist for air-entrained concrete. The FT resistance of air-entrained concrete is largely dependent on the concrete air void characteristics.