# Hydration, Setting and Crack-Resistance Properties of Activated HVFACs at Early Stages
## 2 Materials and Methods
### Instruments and Test Methods
#### 2.2.2 Hydration Heat  
Based on the test methods to evaluate the hydration heat of cement (GB/T12959-2008) [30], the hydration heats of the FAC specimens are measured by a cement hydration heat detector (SHR-650 II). The method is based on the thermo-chemical heat of hydration of Hess' law, i.e., the heating effect of the chemical reaction is only associated with the initial state and final state of the tested system regardless of its reaction path. The ASTM C186 [31] uses a similar method to measure hydration heat. When the calorimeter temperature is kept at a constant level, the hydration heat of the tested cement under certain curing ages is defined as the difference between the measured  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Groups**} & **Series of** & **w/b** & **Replacement** & **Fly ash** & **Cement** & \multicolumn{3}{c}{**Aggregates**} & \multirow{2}{*}{**Adminutes**} & \multirow{2}{*}{**Lime**} & **Activator** \\  & **Test No.1** & **Ratio** & **Ratio of FA** & **kg/m3** & **kg/m3** & **Coarse** & **Fine** & **kg/m3** & **kg/m3** & **kg/m3** \\ \hline Compressive + & C40-FA-AC2 & 0.41 & Y = 0.02, & 3857 & 385 (-17) & 1094 & 705 & 3.08 & 38.5 & 385Y \\ Setting time & C60-FA-AC2 & 0.30 & 0.3, 0.4, 0.5, & 530Y & 303 (-1Y) & 1113 & 562 & 7.95 & 38.5 & 386Y \\ Early crack & C40-FA-AC2 & 0.41 & 0.6, 0.7 & 385Y & 385 (-17) & 1094 & 705 & 3.08 & 38.5 & 388Y \\ \hline \hline \end{tabular}  
* the specimen CX-FAY-ACZ means a FAC specimen uses CX concrete, FA of Y times the used cement (mass) and Z-type AC  
\end{table}
Table 2: Mix proportions of concrete.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Groups** & **Test No.1** & **Cement (g)** & **Fly ash (g)** & **Water (ml)** & **Na\({}_{2}\)SO\({}_{4}\) (g)** & **Curing Age (Days)** \\ \hline \hline  & FA00-AC00 & 40 & 0 & & & \\  & FA20-AC00 & 32 & 8 & & & \\  & FA30-AC00 & 28 & 12 & & & \(1/3/7\) \\  & FA40-AC00 & 24 & 16 & 100 & 0 & \\ Hydration & FA50-AC00 & 20 & 20 & & & \\  & FA60-AC00 & 16 & 24 & & & - \\  & FA70-AC00 & 12 & 28 & & & - \\ \hline  & FA40-AC10 & & & & 0.4 & \\  & FA40-AC15 & 24 & 16 & 100 & 0.6 & \(1/3/7\) \\  & FA40-AC20 & & & & 0.8 & \\ \hline \hline \end{tabular}  
* where, specimen FA-ACy means a FAC mortar was made with \(\times\)% FA (mass of cement) and is activated by \(y\)% AC (by mass of binder).  
\end{table}
Table 3: Mixture proportion details in the hydration heat group. FA, fly ash. AC, activator.  
solution heat, from the dissolving heat of un-hydrate cement (H\({}_{1}\)) and hydrated cement (H\({}_{2}\)) via using a certain concentration of standard acid. The method and instrument for testing hydration heat are illustrated in Figure 1.  
To evaluate the hydration heat of various kinds of fly ash-cement systems under different conditions, the mix proportion details of FAC paste are listed in Table 3. The mass of FA in the binder of concretes/pastes changes from 0%-70% of PC, and the activation of FA-PC was completed by using chemical activator of Na\({}_{2}\)SO\({}_{4}\) with 1.0, 1.5 or 2.0% of the binder materials' mass.