Effect of particle size on cement foams

Abstract

This work attempts to elucidate the foaming kinetics, hierarchical structures, engineering properties and mechanisms of cement foams with high-volume quartz powder (QP) of different fineness from 200 to 2000 meshes. Comprehensive experiments were conducted to measure the fresh slurry properties, foaming process, penetration strength, and structure of the foams and skeletons. Foaming kinetics was analyzed using fractional-kinetic (FK), pseudo first-order (PFO) and pseudo second-order (PSO) models. Results show that the increase of QP fineness can, respectively, keep, increase and decrease the pH, viscosity, and flowability. The FK model shows the best fitting goodness of foaming kinetics, and the slurry with the QP fineness of 600 meshes possesses the fastest foaming speed. Fine QP shortens the induction time and exothermic peak time, and improve the collapse strength. Coarse QP induces more small bubbles and severe breakage of skeleton, and coarsen the nanopores. The interrelationships among the experiment outcomes and the mechanisms of colloidal adhesion, nucleation and growth of bubbles and cement hydrates, and microstructure development in skeletons are profoundly discussed. The findings deepen the mechanistic understanding of cement foams with different size particles.