# Pore Structure Degradation of Different Cement
## 4 Results and Discussion  
### Mercury Intrusion Porosimetry  
The total porosity values obtained for the studied specimens at 90 days can be observed in Table 2. In the exposure medium column, \"no attack\" refers to samples hardened in laboratory conditions and \"attack\" refers to those exposed to the sulphuric acid attack. First, the total porosityof all the mortars had similar magnitude, independently, in the acid attack. In relation to those stored in optimallaboratory conditions (without attack), the lowest total porosity values were noted for the specimens with nanosilica. This result shows a slightly beneficial effect of this addition in terms of porosity, which agrees with another study in which nanosilica has been used [28]. The control and ethyl silicate specimens had practically the same total porosity when not exposed to the acid attack. This result was expected in view of the fact that the ethyl silicate was applied by spraying on the surface of the sample, whereas the rest of the admixtures analysed in this work were incorporated during the setting of the specimens. Therefore, the effects of the ethyl silicate in the total porosity of the global material were less noticeable, especially when it was not exposed to harmful conditions. Finally, for this optimallcondition, the highest total porosity corresponded to the mortars with zinc stearate. Regarding the total porosity of the mortars exposed to the sulphuric acid attack, the lowest values were noted for the control specimens, followed by the nanosilica ones. On the other hand, the highest values of this parameter were observed for the zinc stearate and ethyl silicate samples. With respect to the effects of the abovementioned attack on the total porosity of each material, small variations of this parameter were observed. In the case of control and zinc stearate mortars, total \begin{table}
\begin{tabular}{c c c} \hline
**Mortar Type** & **Exposure Medium** & **Total Porosity (\%)** \\ \hline \multirow{2}{*}{Control} & No attack & 10.1 \\  & Attack & 8.6 \\ \hline \multirow{2}{*}{Ethyl silicate} & No attack & 10.0 \\  & Attack & 11.7 \\ \hline \multirow{2}{*}{Zinc stearate} & No attack & 13.5 \\  & Attack & 11.1 \\ \hline \multirow{2}{*}{Nanosilica} & No attack & 9.4 \\  & Attack & 9.9 \\ \hline \end{tabular}
\end{table} 
Table 2: Porosity results at 90-day exposure. porosity showed slightly lower values for the samples exposed to the sulphuric acid attack, compared to the optimal condition ones. On the contrary, for the ethyl silicate specimens, this parameter was higher when subjected to the harmful condition. For nanosilica mortars, the attack hardly had an effect on total porosity. The pore size distributions in fixed diameter intervals--\(<\)10 nm, 10-100 nm, 100 nm-1 \(\upmu\)m, 1-10 \(\upmu\)m, 10 \(\upmu\)m-0.1 mm, and \(>\)0.1 mm--were also studied. These distributions for the studied mortars can be observed in Figure 2. In addition, the volume of each pore interval for the studied samples is compiled in Table 3. Regarding the control mortars, the volume of pores with diameters higher than 100 nm hardly changed between the samples exposed to the sulphuric acid attack and those hardened in the optimal condition. On the other hand, a noticeable decrease in the volume of smaller pores (diameters lower than 100 nm) in the control samples subject to the acid attack was observed, compared to those without the attack. Therefore, the previously described reduction of total porosity for control mortars exposed to the attack could be related to the abovementioned decrease of overall volume of pores of diameter ranges lower than 100 nm. In view of this, it can be pointed out that the sulphuric acid attack produced a less-refined microstructure in control mortars, with a predominance of pores of higher sizes.