Nanomodified Solutions Based on Composite Sulphoaluminate Binding Substances

The article deals with development of solutions and influence caused by nanoadditives and surfactants on the processes of structural formation of sulphoaluminate phases. According to the results of the research, the introduction of nanoadditives is not possible without surfactants. The influence of modifiers is determined on the basis of experimental studies of mixtures of pure C₃A and AC, ACH minerals. Therefore, the technology of dispersion of nanoadditives and their introduction during the process of preparation of the mixture is proposed. Based on the methods of planning a full-factor experiment and conducting experimental studies, a set of experimental and statistical models are developed, a number of solution compositions based on the components of alumina and gypsum binders containing the maximum amount of ettringite are determined: 17.1% alumina cement, 7.32% gypsum, 0.4% plasticizer, 0.18% nanotubes, 75% sand, and a system strength of 40.2 MPa is provided. The optimal composition providing system strength of 37.8 MPa includes 16.7% alumina cement, 7.15% gypsum, 0.4% plasticizer, 0.75% taurite, and 75% sand. Samples with silicon dioxide (the optimal content of it is of 1%) have system strength of 42.8 MPa and consist of 16.52% alumina cement, 8.48% gypsum, 0.4% plasticizer, 1% taurite, and 75% sand. Formation of a strong structure of solutions is associated with the creation of a gel phase and hydroaluminates of cubic crystal system С₃АН₆, as well as a stable ettringite phase. With the use of nanomodifiers, the formed blocks are freely joined in the cement matrix that leads to a decrease in internal stresses in the not yet formed cement system. In addition, doping of C₃AṤH₃₂ and C₃AṤH₁₂ crystals is suggested. Internal stresses leading to a decrease in the strength of the not yet formed structure do not arise because the joining of blocks takes place in free space. In the case when the hydration process is topochemical, the rate of structure formation will depend on the granulometric composition of the components and the rate of diffusion inside the grain. By means of changing conditions for introduction of various additives into the solution system, it is possible to influence the shape, size, number of crystals, and, accordingly, formation of a spatial structure for the purpose of obtaining a product with the required properties.