Surface modification of bulk material for particle bed 3D concrete printing – Effect on wettability, porosity, and mechanical properties

• Diethylene glycol on particle surface reduces porosity of sand/cement mixture. • Diethylene glycol on particle surface increases bulk density of sand/cement mixture. • Diethylene glycol on particle surface increases concrete strength in SCA. • Bulk density of sand/cement mixture correlates with concrete strength in SCA. This study investigates the influence of particle surface modifications on particle bed concrete 3D printing by Selective Cement Activation (SCA). Prior research suggests that enhancing particle wettability and reducing bulk porosity of the particle bed increases the performance of SCA components. In this work, the effects of dry coatings (nanoscale SiO 2 and TiO 2 ) and a liquid grinding aid (diethylene glycol – DEG) on the wettability and bulk density of two sand fractions and a sand/cement mixture were examined. Nanoscale SiO 2 was found to improve the wettability of the sand/cement mixture, while DEG and nanoscale TiO 2 increased the bulk density and, consequently, reduced the bulk porosity. Based on the results, specimens were 3D printed using the modified materials. Surface modification by DEG increased the compressive strength of printed specimens by 30 % compared to the unmodified, reference material. This increase is attributed to a higher bulk density and, thus, particle bed density compared to the reference material. We conclude that surface modifications enhancing the bulk density can significantly increase the compressive strength of SCA components, thereby expanding SCA’s potential and facilitating its use in construction.