## 4 Discussion
These pozzolanic reactions filling the pores agree with the formation of pores of a smaller diameter and a decrease in the percentage of the bigger pores observed for up to 3 months. It is worth noting that the pH of the samples remained approximately constant over time, so the pozzolanic reaction was not limited because of this factor. No previous results have been reported using cement and limestone powder waste. Nevertheless, [PERSON] et al. [4] reported a reduction in the pores smaller than 0.1 \(\upmu\)m up to 7 days for a cement-stabilized silty clay. After 7 days, the volume of pores larger than 0.1 \(\upmu\)m decreased and the volume of smaller pores increased. The thermogravimetric analysis showed a clear increase in weight loss during the decarbonation process for the samples with the industrial waste. These results agree with previous results obtained for an expansive soil amended with marble dust [20]. Similar results were observed using X-ray diffraction analysis, where the biggest quantity of calcite was recorded for the lime samples with the industrial waste. This observation was also made by [PERSON] et al. [51] for a lime-treated expansive soil, with the calcite crystals formation (CaCO\({}_{3}\)) attributed to the carbonation reaction between the lime, Ca(OH)\({}_{2}\), and the carbon dioxide, CO\({}_{2}\), existing in the air. However, only lime and natural soil were used in that case. Therefore, in the present study, the effect of the presence of the industrial waste also had to be considered. This result reinforces the idea of nucleation on the surface of the industrial by-product particles. On the contrary, slightly lower values of portlandite seem to be found in the samples with the industrial waste in the TGA analysis. A general trend of slightly increasing Ca(OH)\({}_{2}\) was found when the duration increased, which is in agreement with the results of a previous study using fly ash as a cement partial replacement [11]. The reduction of dehydroxylation over time for the cement samples can be related with the decrease in the total porosity observed in the mercury intrusion porosimetry results. This reduction was attributed to the reaction of the portlandite with the clay minerals filling the pores. This reduction was not observed in the lime samples because the calcium hydroxide was released for a longer time. Moreover, the lime samples showed slightly greater values of weight loss at the dehydroxylation stage than the cement samples. This could be because lime produces Ca(OH)\({}_{2}\), and also because, according to [PERSON] et al. [51], the lime treatment of soils strongly modifies the hydroxylation band in the TGA analysis. No previous results for comparison have been found using limestone powder waste in soil stabilization using this technique. The increase in the amount of gypsum over time observed by the X-ray diffraction analysis when the samples were made using a sulfate solution could explain the lower values of total porosity obtained by mercury intrusion porosimetry and the more compact structures of these samples observed in the SEM images. In the same way, the SEM images show a more compact structure in the samples with the industrial waste than in the samples without the by-product. This observation agrees with the total porosity and the microstructure refinement observed using mercury intrusion porosimetry for the industrial waste samples. This more compact structure could be due to the nucleation effect of the by-product, as previously reported when using other by-products as a partial binder replacement [4]. Regarding the samples made using the Na\({}_{2}\)SO\({}_{4}\) solution, no harmful effect was found in these samples compared to those made using distilled water. A more compact structure was observed in the SEM images, and lower values of total porosity were recorded for these samples. Moreover, the UCS values recorded were slightly greater for these samples at 6 months.