Building materials, 6/2000
When we talk about materials, future use aspects, claydite and claydite-concrete are estimated ambiguously.
B.S. Komissarenko, Head of the department “Production of building materials, goods and constructions” of Samara State Architecture and Building Academy, corresponding member of Academy of Technical Sciences of Russian Federation, professor.
Aspects for claydite and claydite-concrete production in consideration of modern objectives in the building industry
At the moment claydite tends to be replaced in the country with other types of insulants by production of enclosing parts. The fact is that bulk density of almost all claydite (keramzite) produced in Russia is around 450 – 550 kg/m³. However, in the view of new tendencies of raising requirements for enclosing parts temperature lag the production of one-layer external wall panels as it is on basis of regular claydite becomes hardly possible even with all innovations.
At the same time one should not disregard another reality – a powerful claydite production basis has been created in Russia (dozens of factories has been built; highly qualified staff is working in this sphere etc.). In such circumstances the liquidation of claydite industry cannot be treated as a correct decision.
From our point of view and taking into account modern requirements it is more correct to work on modification of properties of claydite produced on claydite plants, and to work out its possible application.
One of the solutions of this problem is producing extra-light claydite with bulk density 200 – 250 kg/m³, which accordingly will lower its heat conduction. However, it will be impossible to produce competitive expanded-clay concrete applying standard technologies even using such claydite.
Chair “Production of building materials, goods and constructions” of Samara State Architecture and Building Academy developed a fundamentally new technology of no-sand claydite-concrete preparation and producing one-layer wall panels with improved thermo technical characteristics on its basis (patent RF #2059587 “Methods of claydite-concrete preparation”, bulletin #3, 1996, authors Komissarenko B.S. and Chikhnovoryan A.G.).
Effectiveness of this technology is conditioned on applying new firm synthetic foaming agent ПО-6К (produced by PO “Salavatnefteorgsintez”). And when producing claydite-concrete standard equipment practically with no adaptation can be used. Fine aggregate is completely excluded from concrete composition.
It should be separately noted that the developed no-sand claydite-concrete has optimal combined structure of cement stone, which is saturated with multitude of smallest closed air pores evenly distributed through the volume. With such a structure the concrete has low sorption humidity, low capillary leak-in and water absorbing.
Technology of concrete porisation allows producing no-sand claydite-concrete with an average density at dry state of 650 – 700 kg/m³ with the dry concrete heat conductivity factor not more than 0.14 W/(m•°C) and design factor of concrete heat conductivity not more than 0.16 W/(m•°C) – by dry and normal humidity conditions of operation in the dry humidity climate zone (conditions of Samara).
Materials consumption for 1 m³ of claydite-concrete is: cement – 200 – 250 kg, claydite – 1150 – 1200 l, water – 140-160 l, additives ПО-6К – 1.5 % of the cement mass.
Application of claydite-concrete allows decreasing one-layer wall panels’ thickness to 50 – 55 cm which makes them competitive with regard to brick walls, which are material intensive, labour intensive and of high cost.
This technology is implemented at 15 enterprises with considerable benefits.
A noticeable switch to production of three-layer panels which takes place nowadays is connected with some difficulties. The construction of such panels means their high technical inhomogeneity, which is about 0.5 – 0.75. Production of panels of this type requires more labour inputs and higher reinforcing steel consumption, including expensive rustproof steel bindings as compared with production of one-layer panels. It should be noticed that three-layer panels are joined media where there are always differential temperature and humidity at the media boundaries. In such media and especially by temperature fluctuations, conditions for surface processes are created, the processes sequent to sorption and desorption processes. A very important role has water surface tension.
At large surfaces the speed of foam plastic destruction is comparable to the speed of vaporization (energy of transition state activation for polystyrene is 5 – 7 kJ/mol, transformation heat - 8.6 kJ/mol). Application of effective imported heat insulators like extrusion foam polystyrene which fully comply with the requirements for the inner layer of quality and long-live three-layer panels, will lead to a considerable rise in prices.
One more peculiarity of maintenance of buildings with three-layer enclosing parts should be noted. Three-layer walls contain steam-proof heat insulation in the middle layer, and this is why a healthy microclimate cannot be created without conditioning. This circumstance will lead to a considerable rise in prices of buildings.
In our opinion the regulations introduced at the second phase of energy-saving are in a way set too high, taking into account realistic potentialities of building industry. Majority of plants are not ready to switch to production of three-layer panels, also there are no heat insulations which are completely suitable for the inner layer of such panels in the country.
So, the cost of extra-light claydite panels will be comparably low; such panels will provide high manufacturability of production. Absence of claydite shortage will solve the problem of mass production of panels. Switching to production of claydite with bulk density 200 – 250 kg/m³ should not be a special problem since at present there are quite a lot of technologies developed (different methods of selecting raw materials, using special additives and other) which allow producing light-weight claydite from practically any type of clay staff.
Increasing effectiveness of roofing insulants is of current interest. And claydite and claydite-concrete are not the last to add to the improvement.
In Russia we have a positive experience of applying claydite-concrete as effective heat insulation. For instance, in 1962 it was suggested to use dry no-fine concrete plate heat insulant when building Samara coordinate boring machines plant. Using plate insulant of no-fine claydite-concrete (with claydite of bulk density 250 kg/m³) for heat insulation of the shop allowed refusing expensive imported materials and achieving necessary temperatures in manufacturing facilities.
Application of no-fine claydite-concrete as a heat insulant in the covering plates (ПНС, ПКЖ and other) manufactured during a single processing cycle directly at the factory reached quite a significant volume in Samara region.
This experience shows that application of extra-light claydite allows manufacturing a diversity of effective light-weight concrete constructions for roofing insulants.
At the other hand, wide adaptation of claydite in constructional heat-insulated and construction concretes decreases the weight of the buildings and therefore the cost of assembling articles on the building yard is decreased, building load is reduced, and it al allows decreasing costs of laying the foundation and so on. That is why our claydite factories should direct their efforts to producing claydite product range extended both in bulk density and breakup.
Thus, application of claydite in gutters for heating mains without heat insulation of pipelines should be considered as very effective. Similar application was implemented in more than 40 regions of the country. A large complex of research work has been done to study the durability of gutters considering the possible aggressive influence of subsoil waters, claydite behaviour at high temperatures, thermotechnical and constructional calculations of gutters have been done.
It turned out, that heating mains with claydite-concrete gutters have long durability, which exceed the durability of regular mains for 4 – 5 times.
Applying claydite-concrete in the floors of stock buildings is very promising. Regular claydite of density 1200 kg/m³ have heat absorption equal to that of oak parquet. This fact allows increasing the durability of basis constructions considerably and to improve living conditions for the animals.
One more peculiarity of claydite and claydite-concrete application should be noted. Claydite and claydite-concrete factories were designed and built at the same site in many regions of the country. This is why the cost of transportation is decreased considerably and claydite production technology become simpler by joint operation of the factories.
Hot claydite can be used, and consequently hot claydite-concrete can be used, which will lead to a considerable power saving.
Country has long experience in using constructional claydite-concrete. Thus, when applying it in house-building (e.g. 99 series projects) floor panels, inside walls, stair flights, landings etc. are made of claydite-concrete. Complex application of claydite-concrete provides 8 % decrease in labour consumption, 30 % in cost of transportation, 2 – 5 % in cost, 10 % in reinforcing steel and concrete consumption. Positive experience of claydite-concrete application has been also collected by building of high-rise solid-cast apartment houses, monolithic transistor, development, manufacturing and building of claydite-concrete industrial buildings etc.
There is a variant of producing extra-heavy claydite (keramdor), which is manufactured at reduced for 200 – 300 °C temperatures of burning with bulk density of about 900 kg/m³. Such claydite will be quite competitive due to energy saving during its production with imported natural road metal. It can be applied in road-building, armoured concrete load-bearing structures and other.
Besides technological and economical advantages, claydite has several advantageous characteristics as compared to the natural road metal. These are the improved mortar fraction and aggregate bonding due to deep penetration of the cement paste into the claydite granules which increases durability, service life and stability of the concrete.
Thus, it will be rational nowadays to revise claydite production possibilities and reorient claydite factories without stopping them, to the new objectives of producing two types of claydite:
Extra-light claydite M150 – M250 (manufacturing of effective enclosing parts, walls, roofing, plate heat insulants etc.);
Hard claydite of durability 2.5 – 4 MPa (for manufacturing of supporting constructions, road building, solid houses and buildings etc.).
