Stone materials, even against the background of the appearance of durable fiberglass products and lightweight foam concrete blocks, remain in high demand in the construction market. At the same time, technologies for the use of traditional materials also do not stand still, forcing engineers and designers to pay more attention to technical documentation. For stone and reinforced masonry structures, there is its own regulatory documentation that regulates both the standards for the manufacture of target materials and the methods of their use directly during construction processes.
Code of rules for masonry and reinforced masonry building structures
The current version of SP 15.13330.2012 applies to the development of new projects for stone and reinforced structures, as well as to the reconstruction of existing buildings. An important emphasis in the document is placed on the features of the operation of facilities in the conditions of the Russianclimate. The rules establish requirements for structures that are built not only from natural stone, but also are derivatives of clay materials. At the same time, SP 15.13330.2012 "Stone and reinforced masonry structures" does not apply to the design of construction projects that are planned to be operated under conditions of increased dynamic loads and in seismically hazardous areas. The same applies to tunnels, bridges, pipes, thermal and hydraulic units. The requirements approve the safety standards and serviceability of structures, which is expressed in the technical characteristics of materials and their parameters. In particular, the standards relate to the properties of stone products, mortars used in construction, individual technological solutions and reinforcement methods.
In addition to structural parameters, the joint venture approves the requirements for elements related to stone structures. For example, adjacent parts of coatings or binders should not contribute to the spread of fire throughout the structure or its individual parts. Insulation of stone and reinforced masonry structures, in particular, should be carried out taking into account the fire resistance limits, which are determined by the calculation and analytical method in the process of fire tests.
Basic provisions of GOST for stone structures
With regard to stone structures and structures, GOST regulates the methods for testing masonry and the parameters of brick as one of the main materials for construction objects of this type. With regard to tests, the standard applies to walls and block structures, taking into accountoperating conditions and technical and structural requirements of a particular project. In turn, according to GOST, a brick is defined as a piece product intended for masonry on a building mixture. The purpose of the structure can be defined as load-bearing structures, self-supporting walls, cladding, etc.
Single, hollow, silicate and ceramic bricks stand out as standard. The sizes may also vary. To begin with, it is worth noting the difference between working and non-working parameters. In the first case, we are talking about the dimensions between the edges of the vertical protrusions, which form the thickness of the structure with a single masonry. The non-working size of a brick according to GOST is defined as the length between vertical edges, which determines the length of the wall. The actual length of the product varies from 250 to 288 mm, width - from 60 to 138 mm, and thickness - from 55 to 88 mm. It should also be borne in mind that the technical rules for the construction of walls, in particular, impose restrictions on the use of certain brick formats.
SNiP for stone and reinforced masonry structures
SNiP norms regulate design processes related to structural solutions for walls, panel parts of structures, block elements and various kinds of brickwork. At the same time, the possibility of deviating from the established rules remains, but only if there is an appropriate justification. In addition, the standards approve the standards for the preparation of solutions, taking into account the humidity regime, compliance with the requirements for strength andsustainability of the planned facility.
The updated version of SNiP for masonry and reinforced masonry structures II-22-81 also pays attention to measures that ensure the possibility of construction in winter, including the use of heat engineering means. The requirements for maintaining thermal and humidity conditions due to industrial heaters right on the construction site, frost-resistant additives and plasticizers for solutions are considered. Concrete grades that can be used in the same system with stone structures are also considered separately. For example, this applies to heavy, porous, porous, cellular and silicate grades of concrete. The use of insulating materials for concrete is allowed, but only on condition that such additions will not reduce the tensile strength of the mortar to 0.7 MPa.
What are stone and reinforced masonry building structures?
Almost always stone structures are made in the form of masonry, which, in turn, forms the basis of engineering structures and buildings. Specifically, such structures can be represented by external walls, arches, ceilings, pipe parts, collectors, towers and foundations. And in each case, the stone, its derivatives or imitation materials act as an integral element. The masonry itself can be characterized by different indicators of durability, strength, fire resistance, biological security and thermal insulation ability. Among the negative operational properties of masonry, massiveness, high weight and high labor costs during construction are distinguished. However,optimization of the parameters of the raw materials made it possible to minimize these weaknesses. As confirmation, we can cite brick walls, which are characterized by consistent regular geometry, low weight and good insulating properties.
Reinforced masonry structures can be called a modification of ordinary stone or brickwork. The difference lies in providing the structure with metal rods, which increase the strength characteristics of the object. The reinforcement itself can be represented by different materials - both traditional rods and a mesh that is more flexible in terms of laying. Also, modern reinforcement of stone and reinforced masonry structures can be performed with thin (6-8 mm) fiberglass rods, steel bandages and overlays. In classical schemes, strengthening and reinforcement is carried out from the inside in a longitudinal, transverse or circular way, but depending on the type of construction, the principle of external lining can also be applied.
Varieties of stone and reinforced structures
Masonry configurations are distinguished by several features, the main of which is continuity. The structure can be lightweight monolithic or multi-layered, which also includes layers of cladding and thermal insulation. Moreover, technological layers can be located both inside and outside, which will determine the complexity of the masonry itself. A solid monolithic structure is more often used in the northern regions, since it is distinguished by frost resistance and high thermal conductivity. Lightweight types of stone and reinforced masonry structuresrepresent perforated, porous and porous-perforated masonry. Hollow blocks and bricks are often used to save on material and reduce load requirements for floors. It is advantageous to use such masonry in the construction of low-rise buildings and on the upper floors of high-rise buildings.
Materials for stone structures
Masonry is formed by separate elements, among which are the already mentioned bricks, blocks, silicate products, etc. The entire range of stone materials can be divided into natural and artificial. The first group includes heavy and light products of regular and irregular shapes. These can be natural rocks of granite, marble, sandstone, limestone, etc. Actually, the production process will consist in the mechanical external processing of minerals to achieve certain shapes and sizes. The production of agglomerates containing stone chips is also practiced. In this case, the structure will be of artificial origin, and the raw materials will still remain natural.
As for directly artificial materials, this category includes autoclaved, roasted and non-fired products. Standard walls made of autoclaved bricks are highly durable and long lasting. Fired clay and hollow bricks are also common, which can be used not only in self-supporting structures, but also as cladding. Concrete monolithic elements also belong to artificial stone materials. From block products of this typelaying foundations and floors are formed. Such structures are most often made with reinforcement, since cement in combination with bulk fillers is not able to provide sufficient tensile strength.
Facing building materials for stone structures
Stone is usually associated with the construction of reliable parts of buildings, which are subject to heavy loads. But decorative finishes are no less widely represented in this niche. First of all, the segment of stone facing materials is made up of tiled products. A natural and durable coating can be made from dense limestone, syenite, granite and marble. Aesthetic qualities will depend on how the elements and textures are processed at the factory. By the way, it is in this niche that agglomerate production technologies are actively used, since various patterns and patterns can be formed due to inclusions from stone chips.
Not without decorative value and brick. For exterior decoration, ceramic, clinker and facade facing bricks with a thickness of 60-80 mm are used. Due to special firing in furnaces, this facing material is endowed with frost resistance and fire resistance. For interior design, in order to reduce the load on walls and ceilings, it is recommended to use gypsum bricks. It is easy to process and lay, and after installation work it can be covered with paint and varnish coatings. The only drawback of gypsum is its high moisture absorption, so use it for the bathroom and kitchenunwanted.
Design of stone and reinforced masonry structures
Development of a design solution is carried out taking into account the requirements for the characteristics of the structure, methods of manufacturing material and direct construction. In the calculations, indicators such as the stability of the structure, its strength and spatial invariability are used. In modern design, they are also guided by the principles of divided calculation. This means that documentation is prepared separately for the building as a whole and its parts. In addition, the design of stone and reinforced masonry structures for buildings with a height of 36 m (12 floors) is allowed only if materials of increased strength correspond to cement grades 150-300. The documentation also provides for protection against external influences such as moisture, wind, mechanical stress, etc. In the case of reinforced structures, special attention is paid to metal elements, steel ties, connecting and embedded parts.
Masonry Mortars
Reliability and durability of structures and structures made of stone is largely determined by the building mixtures used. The binder component is not just a connecting link for individual masonry elements. Responsible technological tasks, determined by damper functions, fall on it. They allow buildings to cope with dynamic loads. At the basic level, masonry and reinforced masonry structures are constructed fromcement mortar without special additives. Such mixtures are prepared for standard single-type brickwork. As the masonry or cladding becomes more complex, additional requirements are introduced into the project for the strength of the mortar, its adhesive ability and resistance to various kinds of external influences. To improve the performance properties, technologists include plasticizers, modifiers and other additives in the compositions, aimed at maintaining or improving the individual qualities of the building mixture. With regard to stone structures, such qualities as vibration resistance, viscosity and moisture resistance are especially important, since the porous structure of masonry materials is initially characterized by high penetrating ability.
Conclusion
Stone and its derivatives are the basic resource for the construction of engineering structures and buildings. This mainly applies to facilities that have high technical and operational requirements. At the same time, normative manuals for masonry and reinforced masonry structures segment both consumables and masonry structures according to a variety of characteristics. They relate to strength factors, structural configuration, dimensions and protective properties. An extensive classification, coupled with a variety of ways to build stone structures, allows for a more complete and accurate implementation of design solutions.
