Put Inzenjering - Concrete mixing plant was put into operation in 2002 and since 2005 it has acquired production control software for all concrete kinds of automatized concrete base.

Technical equipment and availability of capacities guarantee safe service and high quality. Concrete production capacity is 45 m3 per hour.

All kinds of concrete prevail. The concrete is fabricated with all necessary additives, as required by an orderer, with the possibility of postponed concrete setting when transported to longer distances. With the concrete base, there will be soon installed laboratory for concrete quality control.

Basic raw materials for concrete fabrication:

• Aggregate – there is used washed and separated aggregate from our separation, of declared fraction sizes: 0-4, 4-8, 8-16 and 16-31,5mm
• Cement - PC20S used.
• Concrete additives – according to orderer’s needs
• Water

We pay particular attention to permanent quality control of the concrete mass. All tests are made in the „Institut za puteve“ laboratory.

Ready for use concrete samples taking and testing is done regularly, aimed at constant maintenance and improvement of the concrete quality. Concrete transportation is by means of our own mixers, aided by auto-pump, as necessary.

Classic concrete with four fractions

1. CONCRETE MB 15
2. CONCRETE MB 20
3. CONCRETE MB 25
4. CONCRETE MB 30
5. CONCRETE MB 35
6. CONCRETE MB 40
7. CONCRETE MB 45

Classic concrete with three fractions

1. CONCRETE MB 15
2. CONCRETE MB 20
3. CONCRETE MB 25
4. CONCRETE MB 30
5. CONCRETE MB 35
6. CONCRETE MB 40

Pumped concrete with four fractions

1. CONCRETE MB 20
2. CONCRETE MB 30
3. CONCRETE MB 40

Pumped concrete with four fractions

1. CONCRETE MB 20
2. CONCRETE MB 30
3. CONCRETE MB 40

Concrete

Concrete is heterogeneous building material consisting of cement, as the basic binding medium, and other binding materials (blasting furnace slag, precipitator ashes, micro-silica...), coarse aggregate that may be natural, crashed and artificial (recycled), fine aggregate which can also be natural and artificial and water, necessary for chemical reactions taking place in the concrete hardening process.

Chemical process which happens after concrete mixing and placing is known as hydratation. Water chemically reacts with the cement, forming the paste which covers other components making the concrete. Chemical reaction leads to concrete hardening, transforming the fresh concrete mixture into rock.

Concrete application in building industry is very widespread and quite known to the wide public. Concrete, as building material, is the most widespread material. According to some data, as of 2005, the total world concrete production was around 6 billion cubic meters, representing around 1 cubic meter per inhabitant of the planet.

Concrete Fabrication (Concrete Mixing)

When designing the concrete mixture, the way of fabrication should be taken into account, as well, that is, the way of component materials mixing. This is important because different types of mixers that may be found in the market sometimes do not correspond to requested concrete kinds.

Technological system of a concrete plant comprises a bunker or silo for aggregate, a silo for cement, water dosing unit and additives dosing unit. It is an option that such a plant may contain additional siloes for storage of filler materials, microsilica or some other concrete fillers or additives.  In case of very fine fillers use, it is desirable to use special facilities, mixing material and the water, dosing it, in that way, to the concrete mixture (in order the losses of powder materials be less). The dosing process depends on a concrete mixing plant manufacturer and it differs from manufacturer to manufacturer.

Quality Control

Concrete quality is defined on the structure design basis, that is, technical conditions for concrete works carrying out. In the structure design, the required concrete designation (MB) is defined, as well as other concrete characteristics conditioning the durability of the structure (resistant to effects of frost, frost and salt, waterproof...). In design documentation the concrete class should be stated for a certain project part or position which contain either the concrete designation or the concrete designation and other required characteristics.

The concrete pressure hardness is tested on cubes (20 cm edges) kept in water or 95% relative humidity at temperature from 17-23oC".

The concrete designation (MB) represents standardized pressure hardness in MPa,  based on 28 days of age concrete characteristic hardness. Characteristic pressure hardness is the value beyond which there may be expected at most 10% of all hardnesses at tested sample pressure (10% fractile).

For reinforced cocncrete there may not be used a concrete designation lower than MB 15.

Quality control consists of fabrication inspection and conformity control in view of the structure design conditions and concrete design.

Concrete quality control implies to check if a corresponding concrete batch meets required concrete designation and other prescribed characteristics. Based on the taking over criteria it is decided if a corresponding batch shall be accepted or rejected.
A concrete batch represents a quantity of concrete of the same class and kind, prepared and treated under same conditions, and it refers to concrete placed into the same or different structural elements in corresponding period.

The volume of concrete batch and the number of randomly taken samples in such batch is defined by the structure design, that is, concrete control programme, in that one batch must not be related to the concrete fabrication period longer than one month.  The number of samples referring to one batch must not be more than 30.

Concrete Fabrication Control

Concrete mixing plant manufacturer makes hardness tests at pressure exerted on a sample, taken for each concrete kind, and it is done every day during the concrete fabrication or at each  50m3, that is, each 75 mixtures.

In case the concrete fabrication in the period of assessment exceeds 2000m3, the samples for concrete testing are taken at each 100m3, that is, at each 150 mixed quantities.

Conformity asessment in view of the conditions prescribed is at placement site.

Regarding concrete supplied from the concrete mixing plant, at least one sample should be taken for each day of concrete pouring at the concrete placement site or at each 100m3, that is, at each 150 mixed quantities.

The assessment of the obtained concrete designation (MB) per batch is based on criteria  contained in BAB 87.

Chemical additives

Chemical additives represent powder or liquid additives, giving the concrete required characteristics impossible to obtain without their addition. In normal circumstances, additives dosing does not exceed 5% in regard to the cement mass. They are added imediately before or during mixing. Reasons for additives application are as follows:

• rеinforced concrete structures fabrication costs reduction
• ensuring quality of fresh concrete mixture during concrete mixing, transport, pouring and care
• hardened concrete characteristics improvement
• possibility of faster building procedure in situation where it is necessary

Successfulness of concrete additives application depends on dosing quantity as well as on the way of concrete pouring. Most additives are liquid and it is possible to use them either in the concrete mixing plant or at site. Effective use of additives depends on goals we like to reach both in the fresh concrete mixture and in the hardened concrete.

Aggregate - Introduction

Selection of an aggregate should be an issue implying technical, economic as well as aggregate availability ascpects in certain region (at structure building site). Aggregate characteristics, its storage and many other aggregate related parameters greatly impact  the characteristics of both fresh and hardened concrete. Depending on the possibility of aggregates storage and their quality control the concrete manufacturers will have smaller or bigger variations in the concrete quality from one to another mixing batch and from day to day of concrete fabrication.

Aggregate, as the main constituent of the concrete, impacts both fresh and hardened concrete characteristics. Its important role in the concrete is often neglected and put aside due to its relatively low price (the price compared to binding materials is far more lower).

Aggregate – Aggregate Quality Control

Quality control assurance is a very complex and comprehensive system of control and quality acceptance. These actions provide for required aggregate quality level assurance. These actions most frequently consist of routine visual inspections and quality control tests, in terms of the way of aggregate fabrication, its handling and acceptance of test at time of fabrication or its use in concrete fabrication.

The purpose of quality control is to monitor and regulate the fabrication process, to provide for uniform materials, to permanently meet numerous specified requirements till the time of this material use in the concrete fabrication.

According to the Concrete Rule Book and pursuant to numerous world standards, the necessary tests to control the plant fabrication (when it is to do with aggregate) are as follows:

• aggregate (fine fractions) humidity testing
• fractions granulometric composition testing
• fractions fine particles quantity

All stated tests must be performed on weekly basis with fine fractions humidity tests done even more frequently in case of some changes ocurrence (due to atmospheric precipitation).