Relationship between cement composition and the freeze-thaw resistance of concretes

Concrete exposed to cyclic freezing and thawing may deteriorate by surface scaling, internally developed cracks or both in combination. The rate of deterioration tends to be accelerated in concretes containing higher levels of supplementary cementitious materials including slag and limestone. A fundamental insight into the relationship between cement composition and freeze-thaw resistance is therefore imperative for developing durable composite cement concretes. Concrete samples prepared from CEM I, binary slag cements and ternary limestone slag cement blends at 0.5 w/b ratio without air entrainment were investigated. The freeze-thaw test was based on the CIF method according to PD CEN/TR 15177. Additionally, phase assemblages in the concretes before and after freeze-thaw damage were evaluated. Before freeze-thaw testing, compressive strengths were similar but the composite cements were slightly more susceptible to carbonation. However, the scaling and internal damage resistance decreased in the order of CEM I, binary and limestone ternary blended cements. The composition of the scaled material differed from the bulk, revealing an absence of portlandite and a marked reduction in AFm and ettringite contents. A probable explanation for the reduced freeze-thaw resistance includes the porosity differences and the lower portlandite content compared to CEM I concrete.