Experimental evaluation of salt corrosion resistance of potassium salt magnesium phosphate cement coating slurry

In this work, a self-compacting potassium salt magnesium phosphate cement (PMPC) coating slurry was prepared by improving the water binder ratio and adding an appropriate amount of water glass (WG) and silica microfume (SMP). By performing long-term solution immersion tests, the following conclusions can be drawn: the remaining flexural and compressive strength values (Δff and Δfc) of the PMPC specimens (M2) containing 2 % WG and 10 % SMP immersed in water, 3.5 % NaCl solution, and 5 % Na2SO4 solution for 540 days were greater than 95 % and 90 %, respectively. In comparison to the reference PMPC specimen without WG and SMP (M0), the Δff and Δfc increased by more than 30 % and 25 %, respectively. After 540 days in 3.5 % NaCl solution and 5 % Na2SO4 solution, the salt corrosion coefficients (Kf and Kc) of the M2 specimen were all greater than 1. After excluding the factor of water corrosion, the salt crystals in the solution had a strengthening effect on the hardened PMPC paste. The M2 specimens experienced volume expansion after being immersed in a solution composed of water, 3.5 % NaCl solution, and 5 % Na2SO4 solution for 540 days (7.21× 10−4, 13.52 × 10−4, and 10.92 × 10−4); this expansion was significantly lower than that of the M0 specimen under the same conditions (13×10−4, 18.5×10−4, and 21.5×10−4) due to the relatively denser initial structure. The initial water absorption rate of M2 (0.64 %–0.66 %) was significantly lower than that of M0 (0.72 %–0.75 %). After soaking in water, 3.5 % NaCl solution, and 5 % Na2SO4 solution for 540 days, the water absorption of the M2 specimens increased by 64.6 %, 7.6 %, and 12.5 %, respectively, which is clearly lower than that of M0 specimens (95.9 %, 22.7 %, and 30.6 %). The increase in the water absorption of the specimen in the salt solution was also obviously smaller than that in the aqueous solution.