*3.3. Effect on Consistency*

Figures 5–7 show the relationship between w/cm ratio and consistency, as expressed by the Vicat plunger penetration, for each SCM. Figure 5 shows that OPC replacement with HCFA increases the w/cm ratio for normal consistency, and the w/cm ratio needs to be increased further for higher replacement rates. This can be explained due to the higher water demand of HCFA but also due to its negative effect on packing density. OPC substitution with LFS (Figure 6), on the other hand, seems to have a minimal effect on consistency, and the w/cm ratio for normal consistency remains unchanged regardless of the rate of cement replacement. The same seems to be the case for OPC substitution with LF (Figure 7), where there seems to be a small increase in consistency at the 30% replacement rate. Again, the effect of LFS and LF on the consistency of fresh cement pastes can be linked with their effect on packing density, which agrees with the literature [45,46].

**Figure 5.** Effect of OPC replacement with HCFA on fresh paste consistency.

**Figure 6.** Effect of OPC replacement with LFS on fresh paste consistency.

**Figure 7.** Effect of OPC replacement with LF on fresh paste consistency.
