Hardening of cement pastes based on surface modified dispersed mineral components
The article discusses the hardening of cement pastes with the addition of ultrafine silica fume silica dry gas, which was studied on a differential automatic calorimeter DAK-1-1A. To optimize the particle size distribution of composite Portland cement, it is proposed to use the surface modification method using a high-voltage electric field. The method of surface modification of dispersed mineral components of concrete includes bipolar treatment of cement and silica fume. In the electrification chamber under the influence of a high-voltage electric field of a corona discharge bipolar charging is carried out by passing one half of the aerosol stream through the positive unit of the charger, and the other half of the stream through the negative unit of the charger, then the unipolar charged particles enter the sinter with an alternating high-voltage electric field. Initially, the initial dispersed mineral components can be charged in a high-voltage field of a corona discharge; in this case, a sample of a finely dispersed component (“guest particles”) is poured through a charging chamber with a negative corona electrode, and a sample of coarsely dispersed components (“guest particles”) through a charging chamber with a positive corona electrode. The site of the electrification chamber consists of a corona electrode located in the center of the pipe, which is made of copper wire with a diameter of 0.6 mm. Then unipolarly charged particles enter the agglomeration chamber, where under the influence of a high-voltage alternating electric field, vibrations with different amplitudes and frequencies are carried out. Large particles oscillate with a larger amplitude and frequency than small particles, the gradient of the frequency and amplitude of oscillations causes an increase in the frequency of collisions of particles, which leads to the formation of spheroidal agglomerates. According to thermokinetic analysis, an increase in the degree of hydration after surface modification in the high-voltage electric field of dispersed mineral components of concrete was established. The results of x-ray phase analysis of cement stone indicate a decrease in the intensity of diffraction reflections of portlandite and an increase in the intensity of lines of calcium hydrosilicates.