## 3 Experiment
### Model Mortar Components
#### 3.4.4 Fine Ground Limestone (FGL)  
Ground limestone has been used as an inactive microfiller in the company Prefa Brno a.s. for many years. According to them, the benefits include lower cement consumption and improvements in the surface quality of the products. The use of FGL was also required in the newly designed concretes. In this case, it was V8 class ground limestone, supplied by CARMEUSE CZECH REPUBLIC s.r.o. from their Vapenka Mokra plant (Mokra, Czech Republic). The chemical composition of the used cement and other powder admixtures is given in Table 1, granulometry is presented in Figure 4. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Composition**} & \multirow{2}{*}{**Compound**} & \multicolumn{2}{c}{**CEM I 42.5**} & \multicolumn{2}{c}{**MK Mefisto L05**} & \multicolumn{2}{c}{**GBFS**} & \multicolumn{1}{c}{**FGL**} \\ \cline{3-8}  & & **Average** & **Average** & **Guaranteed** & **Average** & **Average** \\ \hline \multirow{8}{*}{Content \% of mass} & CaO & 64.2 & 0.28 & \textless{}0.4 & 30–50 & 95.5–98.8 ** \\  & SiO2 & 19.5 & 54.4 & \textless{}56 & 30–43 & 0.7 \\  & Al2O3 & 4.7 & 37.5 & \textgreater{}35 & 5–18 & \textless{}0.1 \\  & Fe2O3 & 3.2 & 3.5 & \textless{}4.0 & 0.2–3 * & \textless{}0.1 \\  & MgO & 1.3 & 0.25 & \textless{}0.4 & - & 0.01 \\ \cline{2-8}  & SO3 & 3.2 & - & - & \textless{}1 including FeO + traces of MnO and & ** the sum of \\  & Cl- & 0.047 & n. g. & - & \textless{}1 including FeO + traces of MnO and & CaCO3 + MgO3 \\ \cline{2-8}  & K2O & 0.78 & 1.1 & \multirow{2}{*}{max. 1.3} & \multirow{2}{*}{Sulfur} & \multirow{2}{*}{CaCO3 + MgO3} \\  & Na2O & 0.09 & \textless{}0.1 & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of chemical composition of different powdered binders used in the described tests. Figure 3: SEM photo of (**a**) mixture of CEM grains (big particles) and (**b**) metakaolin grains (small particles) [28]. 3.4.5. Silica Sand (SiS)  
Model mortars and small samples require smaller aggregate. The best results have been achieved with washed SiO\({}_{2}\) sand (SiS) type PR 31 (fraction 0.3-1.6 mm) and type PR 30 (fraction 0.1-1.0 mm). The used ratio was PR31 (60-70%):(30-40%) PR30. The supplier was the company Provodinske pisky a.s. Provodin plant (Provodin, Czech Republic). 3.4.6. Xypex--Crystallization Admixture  
The cooperating company, Prefa Brno a.s., was interested in including a crystallization admixture in the experiment. The aim was to determine how the crystallization admixture affects concrete exposed to sulfates. Prefa Brno a.s. supplied the admixture Xypex Admix C-1000 [30] with the information that it be used in an amount of 2% of cement content. According to the admixture manufacturer, the resistance of the resulting material should be equal to sulfate-resistant cement and should improve workability of fresh concrete. Since no additional instructions on the material substitution were provided, a compromise was chosen--1% of Xypex (i.e., 5.7 kg/m\({}^{3}\)) substituted the same amount of CEM + FGL and the other 1% was included in addition to the initial binder paste volume. 3.4.7. Set Retarding Admixture  
A small amount of a set retarding admixture was used in the composition of the final mixtures, namely the type Centrament Retard 360, a product of the company MC Bauchemie s.r.o. (Zebra, Czech Republic). A small amount of this admixture retards the initial intensive reaction of cement (binder) with water. As a result, this allows the formation of a larger number of condensing cores and leads to improvements of long-term properties. 3.4.8. Multifunctional Admixtures  
During the design and production stage of high-performance concretes (HPC), a key role is played by plasticizing, superplasticizing or even hyperplasticizing admixtures (a term used by the company Mapei). Recently, the term \"multifunctional admixtures\" has also been used and is probably the most suitable. Multifunctionality of admixtures is currently gaining increasing importance.