**8. Effect of supplementary cementitious materials on freeze/thaw resistance**

Recently, the use of supplementary cementitious materials has dramatically increased due to an increase in environmental awareness. Incorporation of various mineral admixtures, supplementary cementitious materials, into concrete as one of the cement-based composites is a generally well known and frequently used approach. Supplementary cementitious materials are usually employed for partial replacement of cement in the production of concrete, where their use brings significant ecological and economic benefits [12].

Fly Ash, blast furnace slag, silica fume and metakaolin are commonly used supplementary cementitious materials for the purpose of enhancing the performance of concrete from a different point of view, such as enhancing the concrete's properties, value, and cost. They have a clear effect on the fresh, mechanical and durability performance of concrete, and thus on its Freeze/thaw resistance. Several studies conducted on the effect of supplementary cementitious materials on concrete performance have been reviewed [46–48]. Most of these studies have indicated that adding supplementary cementitious materials helps in resisting deleterious effects, such as alkali-silica reactivity, freeze/thaw deterioration, random cracking, and permeability. Supplementary cementitious materials enhance the frost resistance through reducing the macro capillary porosity of cement matrix and form stable gel-like hydration products [24].

#### **8.1 Cement type**

Concrete is rich in alkali and therefore it reacts actively with acidic gasses and liquids, freeze/thaw resistance of hardened cement paste plays an important role in the resistance of concrete to the freeze/thaw cycles. Especially in the case of using highquality coarse aggregate with low porosity. The freeze/thaw resistance of cement paste depends on its porosity, the size of pores, capillaries, and their distribution [49]. Skripkiūnas et al. [50], tested the freeze/thaw resistance of concrete made with different types of cement, the effect of four types of cement on the freeze/thaw resistance of concrete has been investigated by them: CEM I type Portland cement, CEM II/A-S 42.5 N and CEM II/A-LL 42.5 R contained 6–20% of blast furnace and limestone, and CEM III/B 32.5 N-LH contained 66–80% of slag. They concluded that concrete containing slag cement CEM III/B 32.5 N-LH has the highest freeze/

thaw and de-icing salt scaling resistance. While concrete containing Portland cement CEM I 42.5 R has the lowest freeze/thaw and de-icing salt scaling resistance.

The ductility of concrete made of cementitious composites decreased remarkably and the cement containing slag is freeze/thaw resistant [51]. Deja [52] observed a high salt scaling resistance of concrete containing cement rich in granulated blast furnace slag and by using air-entraining admixture even at relatively high values of w/c ratio. Skripkiūnas et al. [53] investigated hardened cement paste made of CEM I 42.5 R cement modified with synthetic zeolite admixture, the mass loss and deformations freezing/thawing cycles were much lower in concrete modified with synthetic zeolite which modifies the morphology of hardened cement paste. However, in other research for Skripkiūnas et al. [54], they investigated the freeze/ thaw resistance of concrete made of CEM I 42.5 R cement modified with sodium silicate solution and found that the destruction after 56 freeze–thaw cycles and exposure do de-icing salt solutions is smaller in hardened cement paste modified with sodium silicate solution. It may be used to improve the durability of hardened cement paste and concrete used in road building.
