Surface treatment with silicon-based nanoparticles in Portland cement specimens subjected to physical sulfate attack

The use of simple (SN) or functionalized (FN) silicon nanoparticles in three variants of surface treatments to mitigate the physical sulfate attack was evaluated in mortar specimens made with ordinary portland cement (OPC) or sulfate resistant cement (SR). The treatment variants were: T1 – with a 0.1% suspension of SN, applied by immersion, in the first 72 h of cure; T2 – with a 0.1% suspension of FN, applied by brushing after 28 days of hydration; and T3 – consecutive application of T1 and T2. Subsequently, the specimens were partially immersed in a 5% sodium sulfate solution and subjected to wetting and drying cycles. A physical-chemical characterization was carried out utilizing XRD, XRF, and SEM/EDS and the surface contact angle was determined regularly during the exposure. The results were complemented with a visual analysis of the specimens at the end of the exposure. The results showed that, although the specimens treated with T1, T2 and T3 show a certain degree of deterioration caused by the physical sulfate attack, the treatments have contributed to preventing the entry of the sulfate solution at the beginning of the exposure. Therefore, it is concluded that the treatments are effective in the initial stages of exposure to the physical sulfate attack.