# High-Durability Concrete Using Eco-Friendly Slag-Pozzolanic Cements and Recycled Aggregate
## 2 Slag-Pozzolanic CEM V Characteristics
### Basic Cement Qualities  
#### 2.2.1 Cementitious Constituents  
Subsequent to the manufacturing of the different CEM V cement types, testing of the main cement properties was performed (see also [47]). In a first step, the main chemical properties of the cementitious constituents of (3) and (4) were compared by X-ray fluorescence to illustrate the fundamentally different chemical composition of fly ash (FA), blast furnace slag (S), and the pozzolana zeolite (P) (see Table 1). In the case of FA and the natural pozzolana zeolite (P), SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) contents are--compared to S--high, suggesting high pozzolanic activity (see also Table 2).  
Blast furnace slag (S) shows similarly high values of SiO\({}_{2}\) with 41.2 wt% and a high CaO and MgO content of 37.2 and 10.1 wt%, respectively. Loss on ignition is relatively high in the case of Pozzolana, because of the chemically bound water from clinoptilolite [(Na, K, Ca)\({}_{2}\)-3 Al\({}_{3}\)(Al, Si)\({}_{2}\)Si\({}_{13}\)O\({}_{36}\)-12H\({}_{2}\)O].  
XRD of the cementitious constituents' analysis again provides further information on the degree of crystallinity by interpretation of the peak visualization: Broader, less distinct peaks suggest low crystallinity, while explicit and high peaks indicating the opposite. XRD diagrams of the raw materials used show the following (Figure 1): FA consists of well-crystallized SiO\({}_{2}\) and portions of anorthite (Calcium Feldspar), while the Ca- and Mg-aluminosilicates are diffuse and show a low crystalline grade without any distinct higher-intensity peak (Figure 1). Blast furnace slag (S) can be described as poorly crystallized, showing two major peaks indicating ferrite and belite phases, and also consisting of other, different burned phases (see Figure 1). By contrast, the natural pozzolana zeolite (P) consists of the well-crystallized tectosilicate Clinoptilite (numerous high-intensity single peaks with the main intensity at angles 2\(\Theta\) of 11.3 and 22.5).  
Pozzolanic activity of the cementitious constituents was tested using [PERSON]'s testing method according to [48] by the solution of 20 g of cement in 100 mL of water at 40 \({}^{\circ}\)C for varying periods (1, 7, and 28 d), measuring the calcium and hydroxide ion values, calculating the oxide-bounded Ca, and comparing the bounded CaO to the calcium oxide solubility isotherm curve (% of bounded CaO) (Table 2).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Compound** & \multicolumn{3}{c}{**Mass Percentage [wt\%]**} \\  & **Fly Ash (FA, V)** & **Blast furnace slag (S)** & **Pozzolana Zeolite (P)** \\ \hline SiO\({}_{2}\) & 57.8 & 41.2 & 61.4 \\ Al\({}_{2}\)O\({}_{3}\) & 17.9 & 6.2 & 11.5 \\ Fe\({}_{2}\)O\({}_{3}\) & 7.4 & 0.5 & 1.4 \\ CaO & 4.2 & 37.2 & 3.5 \\ MgO & 6.3 & 10.1 & 4.3 \\ SO\({}_{3}\) & 2.6 & 2.8 & 3.3 \\ Na\({}_{2}\)O & 1.4 & 1.4 & 1.3 \\ K\({}_{2}\)O & 1.3 & 0.4 & 1.6 \\ Loss on ignition & 1.1 & 0.0 & 12.2 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Chemical properties of cementitious constituents of (3) CEM V/A (S-V) 32.5 R and (4) CEM V/B (S-P) 32.5.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Compound** & \multicolumn{3}{c}{**Bounded CaO by Pozzolanic Additives [mmol/L and (\% in Saturated Ca(OH)\({}_{2}\) Solution)] after**} \\  & **1 Day** & **7 Days** & **28 Days** \\ \hline
**Fly ash (FA)** & 5.6 (25) & 12.7 (57) & 19.5 (87) \\
**Blast furnace slag (S)** & 7.5 (34) & 10.4 (47) & 12.8 (57) \\
**Pozzolana Zeolite (P)** & 19.2 (86) & 21.2 (95) & 21.7 (97) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Pozzolanic activity of cementitious constituents (by Frattini-test).  
Table 2 clearly shows that CaO is very rapidly and most strongly bound by the pozzolanae zeolite, bounding approximately 97% of CaO after a period of 28 days. This is achieved by the high SiO\({}_{2}\) and low CaO content, cf. Table 1, resulting in a high pozzolan activity.