Effect of Cement Paste on Concrete Properties

Cement paste has a great impact on the properties of concrete, however, these properties are related to the three concrete components cement, aggregate and water. The effect of cement paste should be discussed under the assumption that all these components are of high quality and their proportions in the concrete mixture are fairly well selected. 

According to Gebauer [1], the water demand of cement paste is the fimetion of the CjA and alkali content, as well as the function of cement fineness. However, in the same report [1] this author also found no relation between the water demand of cement and water content in concrete mixture, to produce the composite of stable consistency. It appears in practice that this parameter is strongly affected by aggregate, particulariy by its porosity and sand fraction content. Therefore the exceptional caution is required as the results are transferred from cement paste to concrete mixture. 

Locher [2] investigated the effect of cement fineness, determined by the parameters of RRSB equation, such as x — particle size (determining such a diameter that 63.2% particles are smaller than x ), n—slope of the straight line determining the half of width of normal distribution, on the water demand of cement. At constant n, the reduction of x parameter from 20 to 13 pm in the n-x system leads to the significant growth of water demand (Fig. 6.1). The C3A reactivity, as well as the specific surface of cement are shown in Fig. 6.1 too. 

The state of the art of the relation between the properties of cement paste and concrete, has been summarized by Bombled [3]. The effect of cement fineness and cement content in 1 m of concrete was particularly well recognized (Figs. 6.2 and 6.3) [4], 

Moreover, the effect of mineral and chemical composition of cement on setting and stiffening of concrete is known, as well as on its strength. 

---