5.2. Types of natural stone products

Natural stone materials are produced by industry of construction materials. The basic types of products are crushed stone, gravel, sand, rubble stone, cladding elements, wall sawn stone, paving and other elements of the special assignment (Fig.5.4).

Rubble stone is a construction material which consists of pieces of rock irregular in shape 70-1000 mm in size. It is used for laying of foundations, underground parts of buildings, walls of nondomestic, subsidiary and production buildings, for strengthening of earthen slopes, in road construction, and also as an aggregate for rubble concrete. In hydrotechnical construction fill dams are also erected of rubble stones. Stone composition by coarseness is assigned from getting minimum porosity taking into account the peculiarities of dams.

R ubble stone is divided into self-faced (with one uneven face) and slabby (with two approximately by parallel faces). Cobble stone is a type of rubble stone, round inshape.

Strength of rubble stone is estimated by compressive strength of initial rock in the water saturated state. Ultimate strength of rubble stone is in the range of 10-140 MPa. Stone made of metamorphic rocks should have strength not less, than 40 MPa, but the stone made of igneous rocks - not less, than 60 MPa. Frost resistance of rubble stone is approximately equal 15-300 cycles of freezing and thawing. There are accepted not more than 15% fragments with dimensions, different from limit ones in rubble stone batch. Clay content in stone should not exceed 2% by mass, softening coefficient should be not less, than 0.7.

Facing and walling stone. Facing slabs and stones are produced by sawing of natural stone blocks. In the case of application of off-quality blocks there are obtained sledged slabs and stones.

For obtaining facings elements rocks of granite group and metamorphic rocks like marble and colored variations of quartzites are commonly used. Sedimentary rocks - limestones, sandstones, dolomites, travertines and gypsums are applied mainly for internal facing. Quartzites and granites have the highest durability; marbles have considerably lower durability, and can quickly to collapse at outdoor conditions.

Rocks which are used for the application of facings elements should have compressive strength not less than 5 MPa, frost resistance - not less than 15 cycles. Depending on blocks dimensions they are divided into some groups. There is accepted in a block no more than one crack, which is visible at two adjacent surfaces, less than one third of measuring long. Cracks on slabs less than one third of width length are allowed in that case, when slabs are made from the colored marble. Facings elements have abrasive (polished, rubbed, honed) or impact (tooled, boasted, pointed) finishes. The most common are sawn slabs 6-80 mm thick, 200-400 mm width.

Decorative slabs with mosaic and ornamented surfaces are produced utilizing separate pieces of natural stone, crushed stone and sand, and also inorganic or synthetic binders. Slabs are marked by grades, type, kind of face and overall dimensions are specified in which.

Due to high durability of natural stone facing their maintenance costs are considerably less than, at finishing of buildings by paints, coloured mortars and concretes.

As walling materials sawn work stones and large-size blocks are used. For walls light-weight porous rocks are used which have average density 900-2100 kg/m³, compressive strength 0.4-50 MPa and frost-resistance not less than 15 cycles. Minimal value of softening coefficient of walling materials and blocks is 0.6, water absorption for tuffs is 50%, for limestones and other rocks it is 30%.

Walling stone and blocks often have following basic dimensions, mm:

Stones – length 390, 490, width 190, 240, height 188, 288;

Blocks - length 400, 500, width 820, 1000, height 2360, 2520, 2860, 3020.

By assignment wall stones are divided into facial and ordinary ones. Ordinary stones are used for walls erection with subsequent plastering.

Ultimate compressive strength of wall stones is 0.4-40 MPa, blocks - 2.5-40 MPa.

At symbolic notation of walling stone they specify type of stone by dimensions, its kind by assignment and compressive strength grade.

Walling elements made of natural stone have beautiful surface finish (rose, blue, yellow tuffs; white, yellow light grey limestones), they are processed easily.

From separate blocks, sawn from light-weight rocks, it is possible to make on mortar-based large composite blocks and panels the application of which enables to promote productivity of building.

It is effective to utilize composite blocks "floor" in high, which are made of 6-8 ordinary blocks, gaps between them are filled with cement mortar. Large panels, glued from separate elements by polymers are perspective products made of natural stone.

Border stone, pavestone, sledged stone and cobblestone are used for road construction as a workstone. These elements are served for detaching the traffic ways and highways from pedestrian ways (sidewalks), for paving roadways, tram-car ways, strengthening the slopes of earthen coatings and subbases. Raw materials for them are high-strength rocks with strength not less than 60 MPa, frost resistance not less than 25 cycles, with softening coefficient 0.6-0.9, water absorption 1-4%, impact resistance 15 kPа.

Piece natural stones are transported on pallets or separately, by purpose, by types and grades.

Stone materials and elements are widely used in water industry construction. At construction stone irregular in shape: rubble stone, cobblestone, sometimes boulders, gravel and crushed stone are utilized for laying of foundations of hydraulic structures, erecting the earth-and-rock-fill and rock-fill dams, preparation of rubble concrete for the erecting of interior zone of concrete and reinforced-concrete dams, foundations of the hydro systems of the pumping stations and hydroplanes, consolidation of hay-crops of canals and ponds, arranging of stoning round concrete hydraulic structures to protect concrete from corrosion. The stone of regular shape from igneous dense rocks and sandstones are used for dams stonework by the method of dry rubble (without mortar) by regular rows with bonding; arranging of finishing stonework of underwater and above-water parts of structures (embankments, pumping stations, hydroplanes buildings); masonry work of footings of aqueducts, bridges and retaining wall; architectural elements production (columns, semi-columns, basement parts of buildings). A cobblestone made of dense rocks is used for arrangement of fortifications from wave and speed influence of water, hay-crops of earthen dams, canals, water storages, at roadway pavings.

Hewn and sawn slabs made of dense water resistant rocks are used during the external cladding of underwater part of hydro systems, embankments, sometimes facing of hay-crops of the hydrosystems, floors arranging in buildings of hydroplanes and pumping stations. As facing material inside the pumping stations and hydroplanes buildings different types of marble, conglomerates and breccia are used. To improve architectural expressiveness of hydraulic structures there are applied different architectural compositions, produced of water resistant rocks (granite, gabbro, sandstone).

Especially wide application in water construction has clastic rocks such as sand, crushed stone and gravel, gravel-pebble and gravel-sand mixtures. These materials are used for concrete mixtures production for hydraulic and normal concrete; arranging the underlayers under monolithic and precast reinforced-concrete canal linings, roads, constructions; preparation of the drainage filings ups; at consolidation of hay-crops of canals and hydro systems, water storages.

Taking into account that stone materials used in hydraulic construction practically have permanent or periodical contact with water, which often is aggressive one, they have to meet raised requirements not only at density, strength but also in frost-resistance, resistance to aggressive environment.