Softeners (plasticizers), added to the concrete mix

Superplasticizers are construction and chemical additives, with which plasticization is achieved a very strong and significant improvement in the consistency of mortar or concrete. To distinguish from other less efficient they are called plasticizers superplasticizers (Engl. "Superplasticizer"). Their effectiveness in relation to water saving in the manufacture of concrete generally higher than with conventional plasticizers lignosulfonate (see. Table 2.3). In Germany, the use of plasticizers in concrete regulated originally published in 1974, the "Directives for the production and processing of liquid concrete." The chemical composition distinguish two different groups of plasticizers, namely poly condensates and polycarboxylates. The latter are mostly more efficient than polycondensates, and generally, they are more expensive products. In the manufacture of concrete superplasticizers (diluents) that usually used raw materials without chlorine; in some countries it is forbidden to use it for reasons of protection against corrosion.

 

Table 2.3 -Dostigaemaya water savings for a variety of plasticizers

Пластификатор	Классификация	Экономия воды в бетоне, %
средняя	максимальная
Лигносульфонат	пластификатор	5 - 15
NSF	суперпластификатор	10 - 25
MFS	суперпластификатор	10 - 25
Поликарбоксилаты	суперпластификатор	20 - 30
Амфотерные поликарбоксилаты	суперпластификатор	30 - 45

 

polycondensates

Polycondensates - are polymers in which the water outlet (= condensation) form a chain molecule with repeating units (structural units). Since most high polycondensates or structuring degree of condensation are obtained as insoluble, resinous compounds, and they are also called condensate resins. In the construction chemicals in these polycondensates are used as superplasticizers:

· Naphthalene-formaldehyde condensate resin (ASN it. NSF, Eng. PNS = "polynaphthaline sulfonate")

melamine-formaldehyde-sulphite condensate resin (IFS it. MFS, Eng. PMS = "polymelamine sulfonate")

The quantitatively dominating ASN resin with an annual rate of about 350 000 tons, compared with MFS-resins with the general manufacturing 100,000 tons (in both cases as a 40% aqueous solution). Conducted various experiments with phenol, urea, dicyandiamide and sulfanilic acid resins. Successful experiments were only a sulfanilokislota-melamine-cobalt-condensate resins. Compared with pure melamine resins, they show improved reception time of the flushing impact of the concrete. The resulting low cost urea-formaldehyde-sulphite resin insufficient stability during storage (further condensation into insoluble resins) proved to be a big disadvantage.

Concrete

Concrete artificial stone material consisting of a mixture of hardened binder (with water, at least - without it) and fillers. The mixture is specially selected or calculated to ensure obtaining the desired properties of the concrete. The concrete mixture is thoroughly mixed in concrete mixers, fit into molds or formwork and compacted mehanizirirovannymi different ways (by vibration, etc.). It hardens concrete mix in the natural (atmospheric) or artificial conditions of heat and humidity.

A concrete one in the main building materials. It is widely used for the manufacture of precast concrete components, large panels, blocks, etc. Products, as well as for the erection of precast-monolithic and monolithic concrete and reinforced concrete structures. There are many species and varieties of concrete. Depending on the type of binder distinguished: concrete cement (the most common), lime, gypsum concrete, asphalt, etc. plastbeton Aggregates used in concrete are divided into melkie- sand, and large - gravel or crushed stone..

With regard to the cement concrete, the most common classification for volume weight, which is associated with other important properties of concrete - density, strength, thermal conductivity, etc. The following types of concrete are distinguished depending on the volume weight..:

1) Particularly heavy concrete - volumetric weight of more than 2500 kg / m3, the concrete with a very dense structure containing special tvzhelye aggregates of steel, iron ore, barite, etc. It is used for protection against rays pronikvovenmya in nuclear power plants;.. for simultaneous protection against the penetration of neutrons; this concrete must also include the greatest possible amount of hydrate, t. e. chemically bound water.

2) Concrete tyazhelyy- bulk density of 1800- 2500 kg / m3 (usually approx. 2200-2400 kg / m3). The most common (ordinary) type of concrete, especially widely used in concrete and reinforced concrete structures and buildings. It has a sufficiently dense structure and contains a filler of solid rocks.

B) Light concrete - volumetric weight of 500- 1800 kg / m3 contains light (porous) natural or artificial aggregates. The most common varieties of lightweight concrete: slag concrete, expanded clay lightweight concrete, pumice concrete, termozitobeton (with slag vemzoy) tufobeton. The structure of the lightweight concrete is dense enough. PIiroko used for the manufacture of large blocks and wall panels, and to overlap. For lightweight concrete relates cellular concrete.

4) Concrete particularly easy - volumetric weight of less than 500 kg / m3. These concretes are cellular concrete - concrete, foam concrete, the lightest large pore - perlitobeton and vermikulitobeton etc. With bulk density 700-1200 kg / m3 of concrete are structural and thermal insulation and used for the manufacture of large wall panels and blocks for reinforced covering buildings.; most lightweight concrete with bulk density of 400-500 kg / m3 is used insulation material for thermal insulation coatings of buildings and walls.

Frost resistance is required for concrete structures located in respective atmospheric conditions. For the walls of conventional buildings of concrete should withstand 15 times the standard test for alternating freezing and thawing - frost resistance of 15 cycles; Concrete outer parts of hydraulic structures frost should reach up to 500 cycles (depending on climatic conditions).

Water resistance of concrete required in waterworks, pressure pipes, tanks, and so on. N., Provides a dense structure of concrete and special. additives, water resistance is tested to twice the long-term operating pressure at the concrete layer no thicker than 15 cm.

concrete Thermal conductivity is of great importance for the walls of buildings and pavements; it into account when calculating their thickness. Thermal conductivity is related to the concrete structure. The values ​​of its range widely: from 0.10 (in the most lightweight cellular concrete) and 1.0 kcal / m.chas.grad (conventional heavy concrete).

All lightweight concrete have a thermal conductivity less than 0.70.

Shrinkage of the concrete is a decrease in volume of the concrete hardening it to the air, which can cause cracking in large structures. To prevent shrinkage arrange special. joints in buildings, provide hardening concrete (cement) in the first days after laying in wet conditions.

Mobile concrete plants

Concrete plant «COBRA» C40 series, C60 and C80 Tecwill (Finland

«COBRA» is the latest generation of concrete plants, which are characterized by mobility, a quick and easy start to work. At the same time «COBRA» - a powerful industrial complex for all types of construction, including the massive grounds and time-consuming buildings. Removable ramp aggregate supply can be supplied to the plant. Mobile steel elements allow you to set it close to the bunker zapolnitelya.Teploizolyatsiya, heating aggregate and mixtures possibility of heating ensures the production of high-quality concrete, even in winter. «COBRA» represents new opportunities for companies producing ready-mixed concrete, and construction firms. The plant is transported to the new facility by both road and rail. «COBRA» can work as a stationary plant using large-zapolnitelya.Mobilnye bunker installation type M economical to operate on large construction sites. Concrete using such a plant delivered to a stacking location to the nearest minute. Operating systems available in any climatic zones. Units are equipped with an automatic control system with options for different levels. On the ramp on both sides of the active chamber 4 warehouse is loaded camera. Flat boot loader is both weight device. Intensive mixing concrete components is carried out in a pan mixer «Stetter» or in a twin gutter company BHS mixer. Issuance is made concrete in trucks or dump trucks. Basic elements of the installation are collected on M-type plant. On-site installation of manufactured platforms, lifting the mixing area and securing the inclined support, installation of stairs and lining with quick shutters, installation of the equipment for the binder. Management System «Stetter MC", fully assembled at the factory, shipped to the site in konteynere.Mobilnye installation adapted for use in any climatic conditions. Winter installation option involves its use in -ZO'S (made concrete with the injection of steam and hot water) for dosing and weighing.Sistema Operations Management MS 200 consists of a personal computer for data processing and system «Simatik-S5», supplemented by high unit the voltage of the company «Stetter».Avtomaticheskaya technological adjustments (if necessary further adjustment of weighing errors) provides identity batches. Humidity sand dosing period is measured, in the same volume of water carried kneading adjustment and sand. When possible dosing errors signaling system error provides a text message about the error.