Winter Work

construction and erection work done during the winter at below-freezing temperatures. The rapid pace of construction in the USSR is explained to a considerable extent by the fact that construction work (earthwork, stonework, concreting, plastering, and roofing) is carried on throughout the year, relying during the winter months on special methods and additional measures. The elimination of seasonal fluctuations and the extensive use of winter working methods distinguish construction in the Soviet Union from construction in most foreign countries with similar climatic conditions.

Russian and Soviet scientists and engineers contributed much to the development and refinement of winter working methods. In 1912, Professor N. A. Zhitkevich demonstrated the feasibility of doing concreting at any time of the year and in the open air. Near Kiev in 1916-17 the engineer I. A. Kirienko built several reinforced concrete structures in winter by preheating the concrete mix materials and covering the concrete. The development and use of winter operations was hampered by the absence of scientifically based winter working methods and also by norm-based restrictions. (Winter work with concrete and mortar was permitted only in temporary enclosures or heated spaces.)

Winter work was done only on individual structures in the USSR up until the 1930’s. Technical specifications for the performance of winter construction work were developed and introduced in 1933. In subsequent years they were carried out universally. The total elimination of seasonal work fluctuations was an important factor in the realization of the extensive program of capital construction in the USSR. The USSR is the world leader in winter construction volume and the level of winter work technology.

Special technical requirements for doing separate types of winter construction and erection operations and for ensuring the necessary quality of construction are set forth in the Construction Standards and Rules. Winter work is divided into the following categories: earthwork, stonework, concreting, plastering, and roofing.

Earthwork. Earthwork requires preliminary preparation of the ground, which usually consists of preventing the soil from freezing: covering it with a layer of heating material (such as turf, sawdust, or slag), plowing and harrowing the upper soil layer (over large areas), using snow cover, and so on. The frozen ground is usually pre-aerated (broken up) or thawed out. A method of treating the ground without thawing it is also used, whereby the frozen soil is sectioned into blocks that are later removed by cranes or excavating machines. For large areas, such as in the digging of pits, saturation of the ground with water is advisable, since it produces partial thawing of the ground, increases porosity, and reduces hardness. Thawing of the frozen soil is done by probes that use steam, water, or electricity; by electric preheating of the soil with electrodes; or by the use of boxes and temporary local construction enclosures equipped with electric heaters or burners. The frozen ground is developed by special machinery and bulk-operation machines (tractors, excavators) with special equipment mounted on them. Interchangeable equipment for multibucket excavators (chain and rotary bucket excavators) is used for trenches. Machine-mounted equipment that destroys (crushes) the frozen ground by impact (diesel hammers, wedge-shaped rippers, and the like) is also used. With the block-sectioning method, the frozen ground is slit with disccutting machines or bar units mounted on tractors, trenchers, and chain and rotary-bucket excavators.

The blasting method is effective for deep frozen ground and large work volumes. Mechanically operated drilling rigs and gasjet units (thermodrills) are used for making the blastholes in which the explosive charges are set.

Stonework. Masonry freezing, first used in the USSR in 1931-32 during the erection of brick structures, is the basic and most economical method of stonework; this method was subsequently applied to construction using small and large blocks. This method consists essentially of laying stone on preheated mortars that retain the required plasticity at the moment of application and the formation of the joint. The thin mortar joint in the masonry quickly freezes and becomes very strong. The strength of the masonry mortar is partly reduced during thaws or in the spring, but it remains sufficient for normal construction work. The small loss of masonry strength is taken into consideration when specifying the composition of mortar.

Concreting. This type of winter work requires that the concrete be prevented from freezing until it acquires the necessary strength to permit “striking” of the structure or at least until the concrete has achieved its so-called critical strength (ranging from 50 percent to 30 percent of its designed strength, depending on the composition of concrete). Under these conditions, further freezing of the concrete will not affect its final strength.

Plastering. The most important condition for doing plastering in enclosed spaces is heating the spaces (combined with drying the building walls laid out during the winter, which have a high moisture content) and the coat of wet plaster. Various heating methods, such as large-capacity stationary air heaters and adjustable air heaters, are commonly used for the temporary heating and drying of buildings. Rooms and spaces are heated and dried by the installed central-heating system, in conjunction with electric heaters for hastening the drying of isolated locations such as damp corners and recesses. In some cases, plastering may be done in unheated spaces with the use of chlorinated solutions.

Roofing. The installation of roofing materials under winter conditions is complicated by the necessity of thawing out and drying the foundation (base). One layer of roofing material is usually pasted on during the winter and, with the onset of warm weather, the defects in the bottom layer are eliminated and the remaining layers are applied. In the winter, before the application of the roofing material, the cement base (binder) is covered with a layer of diluted bitumen or hot bituminous emulsion, or it is replaced by an asphalt concrete binder or a binder with a porous structure (lightweight aggregate cement mortar).