American J. of Engineering and Applied Sciences 4 (1): 42-51, 2011 ISSN 1941-7020 © 2010 Science Publications Corresponding Author: Taher Abu-Lebdeh, Department of Civil, Architectural and Environmental Engineering, North Carolina A and T State University 1601 E. Market Street Greensboro, Tel: (336) 334-7575 Fax: (336) 334-7126 42 Freezing and Thawing Durability of Very High Strength Concrete Sameer Hamoush and Miguel Picornell-Darder, Taher Abu-Lebdeh and Ahmed Mohamed Department of Civil, Architectural and Environmental Engineering, North Carolina A and T State University, NC 27411, Greensboro, USA Abstract: Problem statement: The newly developed Very High Strength Concrete (VHSC), having compressive strengths of 29 ksi and flexural strengths of 6 ksi, represents a breakthrough in concrete technology. Study to further enhance the properties of this new concrete is continuing. Approach: The objective of this study is to investigate the effect of exposing Very High Strength Concrete (VHSC) specimens to rapid freeze/thaw cycles. Twenty one specimens were tested according to the Standards of the American Society for Testing and Materials ASTM C215, ASTM C666 and ASTM C78. Results: One hundred freeze/thaw cycles were performed on the VHSC specimens. Change in specimen’s dimensions and material’s properties were recorded at zero, forty, seventy and one hundred cycles. Dimensions and properties considered were: dimension of cross section, length, weight, Dynamic Moduli, Poisson’s Ratio, durability factor and Modulus of Rupture. Conclusion/Recommendations: The test results indicated that VHSC is good freeze-thaw resistance (durability factor > 85%) and can avoid freeze/thaw damage. Freeze- thaw cycling did not significantly affect VHSC specimens’ cross sectional dimensions, length, or Poisson’s Ratio. However, there was a decrease in the specimens’ weight with the increase in number of freeze/thaw cycles, but the decrease was very slim indicating little or no deterioration has occur. Moreover, the fine voids exist in VHSC greatly lower the freezing point of any trapped water, making the material less susceptible to Freeze- Thaw damage. Key words: Very High Strength Concrete (VHSC), freeze/thaw cycles, Dynamic Modulus of Elasticity, Dynamic Modulus of Rigidity, Modulus of Rupture, Durability Factor (DF), reducing admixture, osmotic pressure, chemical attack INTRODUCTION Very High Strength Concrete (VHSC) is a newly developed material by the U.S. Army Engineer Research and Development Center (ERDC). The unconfined compressive strength of VHSC can be five times the compressive strength of the conventional normal concrete and toughness of about eight times greater than that of conventional fiber reinforced concrete. These superior properties were achieved by considering several factors such as low flaws, particle packing, improved material homogeneity, low water cement ratio, mixing method and special curing treatment (Abu-Lebdeh et al., 2010a; 2010b; O’Neil et al., 1999; 2006; Hamoush et al., 2010; Ravichandran et al., 2009; Saravanan et al., 2010). To date, researchers continue working on enhancing the properties of this new concrete. One of such properties is the durability of the material. This study is an attempt to investigate the durability of Very High Strength Concrete (VHSC) subjected to rapid freeze/thaw cycles. Durability of concrete may be defined as the ability of concrete to resist weathering conditions, chemical attack and abrasion while maintaining its desired engineering properties. It can be measured by using the standards of the American Society for Testing and Materials (ASTM C-666) which defines the resistance of concrete to rapid freeze and thaw cycles. Durability of concrete is the percent ratio of the dynamic modulus of elasticity after a number of freeze and thaw cycles to the corresponding value before the freeze and thaw cycles. Further, there are many theories explaining how freezing and thawing causes damage to concrete. Such theories include: critical saturation, hydraulic pressure, ice accretion and osmotic pressure (Beaudoin et al., 2009; Mustafa et al., 2009). Critical saturation theory is