## 4 Discussion  
The strong correlation observed between the empirical and rheometric measurements was more pronounced for cement systems with a low viscosity. This was in line with the finding reported in [3, 21, 33]. From the results presented in Section 3, the affinity of the blended SP-C was more supported by the amount of SP-A content within the blend. Since SP-A ionic charges were higher than that of SP-B, it could be assumed that when two admixtures are blended and added to a cement system, the admixture possessing the highest average anionic charge density will have the priority in adsorbing to the cement particles. The capacity of an SP in reducing the rheological parameter values could not only be attributed to its adsorption amount, but also to the length of the side chains. This is because the longer the side chains of the polymer, the greater the steric hindrance it can provide; therefore, increasing the fluidity of the cement paste [1, 27]. Moreover, the competitive adsorption behavior of SPs within a cement system could also be affected by sulphate ions, thus altering the efficiency of the SP [32].  
In fact, the ratio between the sulphate content and aluminate phase is one of the key parameters in regulating the SP effectiveness. It has been shown that a sulphate/C\({}_{3}\)A ratio between 0.7 and 2.0 was sufficient for aluminate hydrate growth and could prevent the production of organo-mineral phases, which formation requires large amounts of SP consumption [18]. Cement 1 and Cement 3 demonstrated higher adsorption abilities than Cement 2 at all concentrations of SP-A fractions, probably due to their higher C3A phases that reacted with the corresponding sulphate phases and led to higher ratio values that imply important SP consumption. In contrast, their yield stress values were higher, confirming that the consumed SP within these cements were used more to produce organo-mineral phases than for particle repulsion.  
The chemical composition of the investigated cements played an important role in affecting their fresh property. Probably, the lower sulphate and alkali contents in Cement 1 favored the dissolution of Ca-ions resulting in greater SP adsorption onto the cement particles without the competitiveness of sulphate ions. For the higher concentration of  
Figure 6: Summary of the adsorption (mg/g cement) of SP-C at 0.25% on Cement 1, Cement 2 and Cement 3.  
sulphate in Cement 2, whose adsorption was favored by a high alkali content, slowed down the adsorption of SP onto the reactive cement sites. The slow release of Ca-ions, due to the low alkali content and the low concentration of sulphate ions in Cement 3, favored the SP adsorption onto the cement.  
The rheological performances of cement pastes were in line with the adsorption behavior of the blended SP-C. Cement 1 with lower adsorption ability, especially at low SP-A contents, resulted in lower yield stress values. This would assume that the excess SP within the system repulsed cement particles through the hindrance effect phenomenon and, therefore, increased the fluidity of the mix demonstrated by low viscosity values.  
It is quite clear that the effectiveness of the SP, as shown in Figures 4 and 5, could be achieved by blending the PCE-based SP with short side chains and different molecular masses for rheological improvements of the mix. This is instrumental to ensure that un-adsorbed polymer remaining in the medium has an opportunity to assist in increasing the fluidity within the medium, as the polymer with a higher molecular weight gets preference in adsorbing first, saturating the adsorption sites before getting consumed by the hydration products. It is after this consumption of the initially adsorbed polymer that the un-adsorbed polymer is given an opportunity to adsorb on the cement particle, which improves the fresh properties of the paste.