Introduction. This article presents the results of an experimental determination of the creep coefficient of glass-composite pressure pipes using long-term testing over 10,000 hours in accordance with GOST R 55077-2012. The relevance of the study is driven by the requirements of current Russian construction legislation: under the Town Planning Code of the Russian Federation and SP 35.13330.2020, the normative service life of pipeline structures is not less than 50 years, which necessitates mandatory substantiation of the long-term mechanical properties of the material. The aim of the present work is the experimental determination of the moisture creep coefficient for a control specimen of a continuous-winding glass-composite pipe and the prediction of creep coefficients over a 50-year horizon Materials and methods. The objects of study were segments of glass-composite pressure pipes of grade Dy 1000 0.6 10000, manufactured by continuous filament winding of glass roving onto a cylindrical mandrel. The control formulation contained no plasticizer; the modified formulations incorporated additives PolyPlast M, Polyplex, and Clearstrength XT100 at dosages of 10, 15, and 20% by binder mass. Long-term specific ring stiffness under creep conditions was tested in accordance with GOST R 55077-2012 (GOST 34644-2020). Specimens were placed horizontally and fully submerged in water (temperature 23±2 °C, pH = 7±2), then loaded with a diametral compressive force maintained constant throughout the entire test period of 10,000 hours. Ring deflection was measured at specified time intervals. Two specimens were tested for each formulation and the results were averaged. Results. For the control formulation of pipe grade Dy 1000 0.6 10000, the mean moisture creep coefficient αavg = 0.74 over a 50-year horizon was determined by regression analysis in logarithmic coordinates. To predict the behaviour of nine modified formulations containing plasticizers PolyPlast M, Polyplex, and Clearstrength XT100 at dosages of 10, 15, and 20%, the theoretical framework of A.A. Askadsky's molecular-kinetic theory was applied, based on the Boltzmann–Volterra integral equation with relaxation kernel T₁(τ). The method was verified against the control specimen: the coefficient of determination R² = 0.97, and the deviation between calculated and experimental load values does not exceed 0.28%. Predicted creep coefficients α₅₀ and long-term specific ring stiffness S50 were computed for all modified formulations. Conclusion. All investigated formulations satisfy S₅₀ > 5000 N/m² and comply with the 50-year normative service life requirements under current Russian legislation. The Askadsky method yields a more conservative prediction compared to the GOST method — from −3.4% to −18.4%
Shashkin et al. (Wed,) studied this question.