About the influence of carbon nanomaterials on the properties of cement and concrete

The article presents the results of studies on the modification of the cement stone and concrete with carbon nanomaterials, which were obtained as a by-product in the plasma gasification of coal. Under the action of plasma arc from the electrode material and coal supplied for the gasification, carbon nanomaterials - fullerene-containing soot are formed simultaneously in one apparatus. This method of production of carbon nanomaterials is a perspective due to a smaller effect on the increase in the cost of the final composite. These carbon nanomaterials have both compact and ultra-disperse fibrous structure, which indicates the presence of such basic forms of nanoparticles as «onion carbon structures» (multiwall, hyperfullerens) and «filamentous carbon structures» (nanotubes, nanofibers). Considering the problem of introduction and uniform distribution of carbon nanoparticles in the cement matrix, that are prone to aggregation, ultrasonic treatment of carbon nanomaterials and mixing water was carried out. The optimal dosage of carbon nanomaterials is 0.01 wt. %, which led to improved physical and mechanical properties of cement stone. It is found that when using various superplasticizers carbon nanomaterials ef fectively distributed in the mixing water amount, but the complex effect of improving cement varies depending on the type of superplasticizer. Changing of hydration temperature of the cement with carbon nanomaterials and various superplasticizers is determined. It has been shown that the introduction of carbon nanomaterials increase the maximum temperature during hydration. The introduction of carbon nanomaterials improves the physical, mechanical and performance properties of cement and concrete by accelerating the hydration process of Portland cement, improving the microstructure and reduction of porosity of cement stone. Lower total porosity of cement stone with the introduction of carbon nanomaterials was found by the method of mercury porosimetry, as well as changes in the number of micropores of cement stone of various sizes was shown. Physical and mechanical properties and performance of the concrete with the introduction of carbon nanomaterials were determined. The improvement in strength at different times of hardening, frost resistance, water absorption and water resistance of concrete were found.