Laboratory Modeling of Cement-Sand Mortar Freezing in Slurried Bored Piles in Permafrost Soils

When constructing on permafrost soils, slurried piles are widely used. The gap between the borehole wall and the pile surface is filled with a mortar. The bearing capacity of the piles is determined by the adfreeze strength between the mortar and the lateral surface of the pile. The standardized method of cement-sand mortar sample preparation for laboratory adfreeze strength testing at the design and survey stage not consider the cement hydration, since small-volume samples freeze rapidly. Consequently, the laboratory testing method does not correspond to the actual field curing/freezing conditions for the cement-sand mortarsamples. The work purpose is to provide experimental substantiation for the cement-sand mortar sample preparation method modifying, to develop a new sample preparation method and to design the device capable the samples curing/freezing temperature regime equivalent to the field conditions reproducing. The article presents the results of experiments determining of eight mortar compositions freezing time at temperatures of -1^оC and -4^оC. According to the experimental results, it was confirmed that cement-sand mortar standard samples freeze in no more than 24 hours, and cement does not hydrate. The method of the samples stepwise cooling at the predetermined temperature regime corresponding to the actual pile installation conditions was developed, as well as the device implementing this method comprising a heating element and a temperature controller. Ignoring cement hydration underestimates the design shear resistance. The proposed method improves the reliability of laboratory measurings and makes it possible to utilize the bearing capacity reserves of slurried piles.

P.M. SAZONOV¹, Engineer (This email address is being protected from spambots. You need JavaScript enabled to view it.);
A.G. ALEKSEEV², Doctor of Sciences (Engineering) (This email address is being protected from spambots. You need JavaScript enabled to view it.)

¹ Scientific Research, Design, Survey, and Engineering Technology Institute of Foundations and Underground Structures named after N.M. Gersevanov JSC SIC Stroitelstvo (6, 2nd Institutskaya Street, Moscow, 109428, Russian Federation)
² National Research Moscow State University of Civil Engineering (26, Yaroslavskoe Highway, Moscow, 129337, Russian Federation)

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