The coefficient of friction and Hamaker constants of cementitious materials

Abstract

• AFM was used to directly determine the Hamaker constants of cementitious materials. • Material characteristics affected the Hamaker constant and coefficient of friction. • The higher the Hamaker constant, the higher the coefficient of friction. • The recommended values can help to accurately calculate inter-particle forces. The friction and adhesion forces between particles are key factors affecting the flowability of cementitious materials (CMs). However, typical values are absent for common CMs due to the limitations of testing methods and the complexity of material components. In this paper, the Atomic Force Microscopy (AFM) and direct shear method were proposed to measure the Hamaker constants and coefficient of friction (COF) directly. The measured Hamaker constants and COF of limestone powder, silica fume, Type I Portland cement, ground granulated blast furnace slag, and fly ash ranged from 7.59 to 18.19×10 -20 J, and 1.06 to 1.36, respectively. Results also indicate a positive relationship between the Hamaker constant and COF. These recommended values can help to accurately calculate interaction forces for single or blend CMs and optimize their storage and transportation.