Building Materials

natural and artificial materials and products used for the construction and repair of buildings and structures. The many different purposes and operating conditions of buildings and structures account for the variety of demands placed on building materials and for the great diversity of available materials. Two basic categories of building materials are recognized: general-purpose materials, such as cement, concrete, and timber, used in the construction of various types of structures, and special-purpose materials, such as acoustic, insulating, and refractory materials. Depending on the degree of preparation before use, building materials are conventionally classified as building materials proper, such as binders and aggregates, and structural components, which are prefabricated units and elements to be installed in buildings at the construction site, such as reinforced-concrete panels, toilet stalls, and door and window units.

Industrialization and the expansion of modern construction have led to an increased share of prefabricated structural components in the total production volume of building materials. The greater output of building materials in the form of almost totally prefabricated items makes it possible to increase labor productivity, decrease costs, and accelerate construction work (seeTOTAL-PREFABRICATION CONSTRUCTION).

Building materials may be divided into 11 basic groups according to processing and functional criteria.

Natural masonry materials. Natural masonry materials include rocks that have been mechanically processed, such as facing slabs, stone for blocks, crushed stone, gravel, and quarry stone. The introduction of advanced methods of extracting and processing stone, such as diamond sawing and heat treatment, substantially reduces labor requirements and costs in the preparation of masonry materials and increases the application of such materials in construction.

Timber and wood products. Timber and wood products are building materials derived mainly from the mechanical processing of wood, including round timber, lumber and semifinished products, parquet, and veneers. Lumber and semifinished products are used in modern construction on a wide scale for various carpentry products, built-in building equipment, and such strip products as baseboards, handrails, and overlays. Laminated-wood products hold promise for future use (seeBONDED STRUCTURES).

Ceramic materials and products. Ceramic materials and products are prepared by shaping, drying, and firing raw material containing clay. Such materials are used in diverse areas of construction because of their greater variety of types, high strength, and durability. They are used for walls (brick and ceramic blocks) and sanitary fixtures and as exterior and interior facings for buildings (ceramic tiles). A porous aggregate for lightweight concretes called keramzit is also included in this category.

Inorganic binders. Inorganic binders are primarily powdered materials, such as cements of various kinds, gypsum plaster, and lime, that form a plastic paste when mixed with water and then harden. Some of the most important inorganic binders are port-land cement and its varieties.

Concretes and mortars. Concretes and mortars are artificial masonry materials with a wide range of physicomechanical and chemical properties, obtained from a mixture of a binder, water, and aggregates. The principal type of concrete is cement concrete. Modern construction also uses products made of silica concrete. Lightweight concretes are ideal for large, precast structural components and units. Reinforced concrete—a combination of concrete with steel reinforcement—is used to increase the flexural strength and tensile strength of structural elements. Concretes and mortars are used directly at building sites (cast-in-situ concrete) and also in the factory preparation of structural units (precast reinforced concrete). Asbestos cement products and structural components, obtained from a cement slurry and reinforced with asbestos fiber, are also included in this category.

Metals. Rolled steel is the principal metal used in construction. Steel is used for the reinforcement in reinforced concrete, for building frameworks, bridge spans, pipes, and heating apparatus, and as a roofing material (roofing steel). Aluminum alloys are also used as structural and finishing materials.

Heat-insulating materials. Heat-insulating materials are used for insulation in the enclosing structures of buildings, in industrial equipment, and in pipes. The materials in this group are available in a large variety of compositions and structures. They include mineral wool and mineral-wool products, cellular concretes, asbestos materials, foam glass, expanded perlite and vermiculite, fiberboard, reed board, and Fibrolit (rigid insulation made from a mixture of wood-wool in portland cement). The use of heat-insulating building materials in enclosing structures permits substantial weight reductions in such structures and reductions in the overall expenditure of materials and in the energy required to maintain temperatures in buildings and structures. Some heat-insulating materials are also used as acoustic materials.

Glass. Glass, used chiefly for transparent enclosures, is produced in the form of ordinary sheet glass, glass for special purposes, including reinforced, tempered, and heat-insulating glass, and glass products, such as glass bricks, rolled glass sections, and glass facing tiles. The use of glass for the exterior facing of buildings, for example, sheet glass with a pigment on one side, holds promise for the future. Cast stone, sittals, and slag sittals are also included in this category because of their engineering characteristics.

Organic binders and waterproofing materials. Organic binders and waterproofing materials include bitumens and pitches, as well as asphalt concrete, Ruberoid, tar paper, and other materials that use bitumens or pitches as a base. Polymer binders used to obtain polymer concretes are also included in this category. Sealing materials in the form of mastic and elastic packing, for example, Gernit (a porous gasket made from a foam polymer with a hard protective coating), Izol (a sealing mastic), and Po-roizol (a porous, elastic, rubber strip or gasket made from worn-out tires), and waterproof polymer films are produced to meet the needs of prefabricated housing construction.

Polymer building materials. Polymer building materials constitute a large group of materials that use synthetic polymers as a base. They are noted for excellent mechanical and decorative properties and water and chemical resistance, and they are easy to handle. They are used mainly for floor coverings (linoleum, rubber linoleum, vinyl tiles), structural and finishing materials (laminated paper plastics, glass-reinforced fiber plastics, chipboard, decorative coatings), heat-and sound-insulating materials (foam and honeycomb plastics), and strip construction products.

Varnishes and paints. Varnishes and paints are finishing materials that use organic and inorganic binders as a base and form decorative and protective coatings on the surfaces of structures. Synthetic paint and varnish materials and water-emulsion paints with polymer binders are widely used.

Standards and improvements. The quality of construction materials is characterized by the grade rating. The grade rating is the basic performance characteristic of the materials, for example, the strength, specific weight, or frost resistance, or a combination of several characteristics. The methods of testing building materials and the technical requirements placed on such materials are established by standards—by the State Standards (GOST) in the USSR—and by specifications.

The cost of building materials in modern construction in the USSR accounts for approximately 60 percent of the total construction costs. Thus, further improvement in the efficiency of construction depends to a considerable degree on more extensive use of new, primarily lighter building materials, such as lightweight concretes, polymer materials, and metal structures that use light alloys, on increased production of special building materials, such as rapid-hardening cements and efficient heat-insulating materials, and on the use of better-quality traditional building materials. Important potential factors in lowering construction costs are the increased use of local building materials, for example, blocks made from such lightweight rocks as tuff ana coquina, and the use of industrial wastes, such as metallurgical slags, ash from steam power plants, and woodworking waste materials. An important trend in the improvement of building materials is the development of efficient finishing materials that improve the architecture and appearance of buildings and structures. (See also.)