Effect of hydrophobic modification and dosage of long afterglow phosphors on the properties of self-luminescent cement-based materials

Both the hydrolysis instability of original long afterglow phosphors (OLP) and limited amount of reflective powders (RP) degraded the luminescent performance of self-luminescent cement-based materials (SLCM). This study novelty proposed a solution by coating organosilicon layer on the OLP surface to create hydrophobic effect for enhancing its water resistance. Furthermore, compared with typical SLCM with low content of LP and RP, SLCM mixtures were prepared through replacing cement by LP and containing higher volume of RP according to the modified Andreasen and Andersen (A&A) model. The effects of dosage and surface modification of LP on the strength, hydration kinetics, luminescent performance, phase composition and microstructure of SLCM were examined. Hydrophobic LP (HLP) achieved similar crystal structure but changed its surface morphology as well as enhanced its water resistance. Introduction of the OLP into SLCM was liable to generate the hydrolysis products. HLP performed better in generating more hydration products but less hydrolysis products, thus formed a compact microstructure and enhanced the thermal stability. Hydration kinetics revealed that the hydrolysis reaction of OLP decreased the heat of hydration, while the hydration process was promoted by HLP. Higher dosage of LP after hydrophobic modification in SLCM helped in obtaining a better luminescent performance but caused a drastic reduction in strength. Overall, the optimal dosage of HLP in SLCM including higher volume of RP was more effective in achieving a superior luminescent performance without degrading the strength.