Improvement of mechanical properties and chloride ion penetration resistance of cement pastes with the addition of pre-dispersed silica fume

The addition of pre-dispersed silica fume (DSF) into cement pastes can enormously improve the engineering property of cement pastes. Yet it is hard to evaluate the distribution of DSF and the absorption process between cement and DSF quantitatively. Therefore, an approach (the titration test) was used to investigate the distribution of DSF and the adsorption process quantitatively in cement pastes. After the examination of the physical and chemical properties of DSF modified cement-based materials, ideal results were obtained in this work. This paper highlights the primary findings in manufacturing and characterizing of DSF modified cement-based materials. For macroscopic performance, the pressure testing machine was used to test the mechanical properties of DSF modified cement-based materials. Meanwhile, Zeta potential analyzer was used to monitor the surface charges of particles in cementitious materials with different DSF contents. From a microcosmic perspective, scanning electron microscope (SEM) was used to capture the microstructure of the compound materials. In addition, to research the influential factors on DSF in the process of ball milling, ball milling time and the parameter of DSF of each ball milling process and other components added into the liquid were taken into account. Finally, the hydration process was simulated. The results show that the DSF can improve the mechanical properties and chloride ion penetration resistance of the sample. The simulated hydration process consists of five stages, which are agglomeration-trigger adsorption (Stage I), initial stable absorption (Stage II), free-dispersion (Stage III), reagglomeration-trigger absorption (Stage IV) and secondary absorption (Stage V). The five stages reflect the corresponding reaction characterization of DSF modified cement-based materials.