Superplasticizers freeze-thaw resistance

Table 2.4 Freeze-thaw resistance of superplasticized concrete (Rixom)...

Despite the fact that the minimum spacing factor is exceeded, the concrete freeze-thaw resistance of the concrete does not appear to be adversely affected [71]. Table 2.7 clearly shows how the presence of an SNF superplasticizer increases the spacing factor of the air void system at each of the three water-cement levels evaluated [71]. 

It has sometimes been argued that concrete is seldom damaged by frost action if low water-cement ratio mixes are used. However, the paramount effect of air entrainment in improving freeze-thaw resistance was clearly demonstrated in a study of the freeze-thaw resistance of both air-entrained and non-air-entrained superplasticized concrete with low water-cement... 

Admixtures are substances that are added during the mixing process in small quantities related to the mass of cement, in order to improve the properties of fresh or hardened concrete [7,8]. The most utilised admixtures are water reducers and superplasticizers that may be added to improve the workability of concrete or reduce the amount of mix water accelerators that are used to increase the rate of development of early strength of concrete set-retarders that reduce the setting time of concrete air-entraining agents that increase the freeze-thaw resistance of concrete (Section 3.1). Recently, corrosion inhibitors have been developed in order to increase the corrosion protection of embedded steel these will be treated in Chapter 13. 

The effect of superplasticizers on the properties of concrete is similar to that of plasticizers. The strength and durability increase as a result of water content lowering. Superplasticizers do not affect creep [297], bnt improve the freeze-thaw resistance [376]. However, the nse of air entraining agents is recommended in several cases [361]. 

In the early days of the use of superplasticized concrete, some concerns were aired regarding the resistance of air-entrained concrete containing superplasticizers to freeze-thaw cycling. However, more recent research has indicated the following ... 

The use of superplasticizers in air-entrained concrete has caused much debate. Two main problems are associated with superplasticized air-entrained concrete (1) a decrease in air content by 1-3% when slump is increased from 75 mm to 220 mm after the addition of the superpiasticizer to create flowing concrete, and (2) a change in the air void system to less desirable values. However, most investigators [10-11, 12] have shown that, although the air-void spacing factor required for adequate frost resistance is altered, the change did not necessarily affect the freeze-thaw durability of... 

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