English
Русский Highly dispersed modifier of cement composites based on natural wollastonite
Abstract
Objectives: development of a highly dispersed modifier based on natural vollastonite, which ensures the production of construction products with improved physical and mechanical properties.
Methods. The evaluation of the raw materials and the effect of their highly dispersed suspension obtained by ultrasonic dispersion on the structure and properties of cement stone and fine-grained concrete was performed using methods specified in GOST R 56593-2015 and GOST 10060-2012, as well as scanning electron microscopy, laser diffraction, nitrogen porometry, and X-ray phase analysis.
Results. The pozzolanic activity of the highly dispersed vollastonite additive was determined to be 87.3 mg/g, and it was confirmed by a 18.2% decrease in the intensity of Portlandite X-ray reflexes in the modified cement stone samples. The corrected frost resistance of the modified fine-grained concrete is noted, which is due to the integral homogeneous microstructure and the reduction in the total porosity of the cement stone from 0.0043 to 0.0019 cm3/g, i.e., by 2.4 times, compared to the control samples, with an increased concentration of crystalline phases of wateerite μ-CaCO3 and wairakite Ca(AlSi2O6)2∙2H2O. It was found that cement stone with a highly dispersed modifier has a relative increase of 32.4% and 5.4% in the concentration of crystalline phases of alite 3CaO∙SiO2 and belite β-2CaO∙SiO2, respectively.
Conclusions. The possibility of using mineral powder of substandard natural wollastonite with a specific surface area of 45786 cm2/cm3 and a particle size of 2.17 μm as a modifier of the structure and properties of fine-grained concrete has been proven and scientifically substantiated. A highly dispersed suspension of wollastonite with an average particle size of 0.405 μm, obtained by ultrasonic dispersion of the initial raw material in an aqueous medium of a polycarboxylate ester-based stabilizer for 5 minutes, with a content of 10% of the cement mass in fine-grained concrete, allows for the production of products with a bending strength of 6.8 MPa, a compressive strength of 58.5 MPa, and a frost resistance rating of F500.
Methods. The evaluation of the raw materials and the effect of their highly dispersed suspension obtained by ultrasonic dispersion on the structure and properties of cement stone and fine-grained concrete was performed using methods specified in GOST R 56593-2015 and GOST 10060-2012, as well as scanning electron microscopy, laser diffraction, nitrogen porometry, and X-ray phase analysis.
Results. The pozzolanic activity of the highly dispersed vollastonite additive was determined to be 87.3 mg/g, and it was confirmed by a 18.2% decrease in the intensity of Portlandite X-ray reflexes in the modified cement stone samples. The corrected frost resistance of the modified fine-grained concrete is noted, which is due to the integral homogeneous microstructure and the reduction in the total porosity of the cement stone from 0.0043 to 0.0019 cm3/g, i.e., by 2.4 times, compared to the control samples, with an increased concentration of crystalline phases of wateerite μ-CaCO3 and wairakite Ca(AlSi2O6)2∙2H2O. It was found that cement stone with a highly dispersed modifier has a relative increase of 32.4% and 5.4% in the concentration of crystalline phases of alite 3CaO∙SiO2 and belite β-2CaO∙SiO2, respectively.
Conclusions. The possibility of using mineral powder of substandard natural wollastonite with a specific surface area of 45786 cm2/cm3 and a particle size of 2.17 μm as a modifier of the structure and properties of fine-grained concrete has been proven and scientifically substantiated. A highly dispersed suspension of wollastonite with an average particle size of 0.405 μm, obtained by ultrasonic dispersion of the initial raw material in an aqueous medium of a polycarboxylate ester-based stabilizer for 5 minutes, with a content of 10% of the cement mass in fine-grained concrete, allows for the production of products with a bending strength of 6.8 MPa, a compressive strength of 58.5 MPa, and a frost resistance rating of F500.