Scope of Ready Mix Concrete

Scope of Ready Mix Concrete

Long, Long years ago, their where simple houses but in 21st century we can see houses constructed in R.C.C. Therefore concrete got more importance than any other construction material. So the use of concrete is increasing day by day.

For construction most of the contractors and builders have to collect the raw materials required for the construction before starting actual works. These materials should be stored at the site properly. This technique can be possible when there will be more empty space at the construction site which is not possible in congested areas. At this time there is one solution to overcome all these problems that is nothing “READYMIX CONCRETE”.

By using R.M.C we can save the time and money required for the labors. In following places ready mix concrete can be used:-

·     Major concerting projects like dams, roads, bridges, tunnels, canals etc.

·     For concreting in congested areas where storage of materials is not possible.

·     Sites where intensity of traffic makes problems.

·     When supervisor and labor staff is less.

·     To reduce the time required for construction etc.

·     Huge industrial and residential projects.

Testing of Concrete

Testing of Concrete

The results of concrete tests are used as the basis for deciding whether the delivered concrete is in accordance with the specification, if the reported results are below the compliance loyal, doubt is cast on the quality of the supplied concrete and the long term durability of the structure. If the investigation indicates that the sampling, preparation and or storage of the test specimens have not been in accordance with the required standard procedures, then the result will be invalid. Further valuable management time, better devoted to other management functions, will have been wasted.

It is, therefore, in everyone's interest that sampling and testing is done correctly so that the results provide a valid basis for logical decision making. Where the contractor is required to perform on-site concrete testing, it is imperative that suitable test facilities are available, that the appropriate equipment is calibrated and that the staff has been fully trained in the relevant test techniques, one can look the factors that affect the price compliance test, (i.e.) the compressive strength test.

As  a result is the average of the compressive test specimens made for the same sample of concrete. Individual variation should not be more than 15 Percent of the average. If more. The results of the average. If more, the results of the sample are invalid. This is because differences of this magnitude indicate poor sampling, cube making, curing or crushing. It is, therefore essential that correct test facilities are provided and the people with responsibility for sampling and testing concrete are suitably trained.

Slump test for predicting the workability of concrete is done at batching plant and working site. The main problem in the production of ready mixed concrete is maintaining the workability of the mix right to the time of placing. Concrete stiffens with time and the stiffening may also be aggravated by prolonged mixing and by high temperature. With the use of retarding admixtures, the time limit can be extended to 3 or even 4 hours, The United States Bureau of Reclamation provides for an extension of 3 to 6 hours in the time of contact between cement and wet aggregate in transport prior to mixing.  The general requirement is that concrete shall be discharged from the truck-mixer within 2 h of the time of loading. However, a longer period may be permitted if retarding admixtures are used or in cool humid weather or when chilled concrete is produced.

Objective of Ready Mix Concrete

Objective of Ready Mix Concrete

The main objective to choose this topic is that an engineer should know the advantages of Ready Mix Concrete and disadvantages of Site mixed concrete. As Ready Mix Concrete are widely using in bigger and medium size of projects today, engineer should be aware the technicality of the Ready Mix Concrete and the operational work to ensure the quality of work to be maintain. Site engineer to be know that what are the steps to be taken to check the concrete in Ready Mix Concrete, what is required to be specified for Ready Mix Concrete, what is the information required to be supplied by the Ready Mix Concrete supplier, what checks are necessary by the consumer before ordering Ready Mix Concrete, what are the checks needed at site prior and after to receipt of Ready Mix Concrete.

Concrete Admixtures and the Environment

Concrete Admixtures and the Environment

Concrete admixtures are liquid or powder additives. They are added to the concrete mix in small quantities to meet specific requirements:

·     To increase the durability

·     To improve the workability

·     To change the setting or hardening reaction of the cement

The effect of admixtures is always to improve the concrete. In quantity terms, super plasticizers (high range water reducers) and plasticizers (water reducers) as a group make up about 80% of all of the admixtures used today.

How much do concrete admixtures leach, biodegrade or release fumes?

Super plasticizers should be non-toxic, water-soluble and biodegradable.

Tests on pulverized concrete specimens show that small quantities of super plasticizers and their decomposition products are leachable in principle. However, the materials degrade well and do not cause any relevant ground water pollution. Even under the most extreme conditions, only small quantities of organic carbon leaches into the water.

·     Conclusion of test: The air is not polluted by super plasticizers.

To summarize: How environment-friendly are super plasticizers?

Concrete admixtures are appropriate for their application and when correctly used are harmless to man, animals and the environment.

The technical benefits of super plasticizers for clients and construction professionals outweigh the occurrence of low, controllable emissions during use. Concrete admixtures merit being rated environment-friendly because they create negligible air, soil or ground water pollution.

See the following publications:

·     “Environmental Compatibility of Concrete Admixtures” Report by the Association of Swiss Concrete Admixtures Manufacturers (FSHBZ)

·     EU Project ANACAD Analysis and Results of Concrete Admixtures in Wastewater Final report BMG Engineering AG Zürich

Sulphate resistant Sprayed Concrete

Sulphate resistant Sprayed Concrete

A sprayed concrete with a standard cement content of 400–450 kg/m³ has high sulphate resistance when it uses:

·     Cement combined with water reducer

·     a standard Portland cement combined with water reducer and added at > 5% or

·     a CEM III-S

Requirement: w/c < 0.50

Recommended mix design for wet sprayed concrete:

·     Granulometry                         0–8 mm

·     Cement content                        425 kg/m³        

Concrete Chemical Resistance

Concrete Chemical Resistance

Concrete can be attacked by contaminants in water, soil or gases (e.g. air). Hazards also occur in service (i.e. in tanks, industrial floors etc.).

·     Surface and ground water, harmful soil contaminants, air pollutants and vegetable and animal substances can attack the concrete chemically.

·     Chemical attack can be divided into two types:

-       Solvent attack: caused by the action of soft water, acids, salts, bases ,oils and greases etc

-       Swelling attack: caused mainly by the action of water soluble sulphates

Measures

·     Concrete structure as impermeable as possible, i.e. low porosity

·     Low water/cement ratio aim for < 0.45

·     Increase the concrete cover by 10 mm minimum

 Concrete only has adequate resistance against very weak acids.

Medium strength acids degrade the concrete.

Therefore extra protection of the concrete with a coating must always be specified for moderate to highly aggressive acid attack.

Concrete Surface

Concrete Surface

The impermeability and appearance requirements for concrete surfaces vary widely. Detailed planning and execution of the structure are required to meet these requirements.

Maximum surface impermeability is essential for all durability requirements. The attack always comes from outside to inside. Over vibration or inadequate curing weakens these zones. High quality appearance requirements have led to the production of so-called “fair-faced” concrete.

Appearance of concrete surfaces

In modern architecture concrete is increasingly used as a design feature as well as for its mechanical properties. This means higher specifications for the finish (exposed surfaces). There are many ways to produce special effects on these exposed surfaces:

·     Select a suitable concrete mix

·     Specify the formwork material and type (the formwork must be absolutely impervious!)

·     Use the right quantity of a suitable release agent

·     Select a suitable placement method

·     Use form liners if necessary

·     Consider any necessary retouching

·     Color using pigments

·     Install correctly (compaction, placing etc.)

·     Thorough curing in addition to all of these factors listed, the following are important for the concrete mix:

Exposed aggregate concrete

Exposed aggregate concrete is a popular surface design feature, e.g. for retaining walls, façade panels, garden features etc.

The aggregate structure is exposed on the surface by washing off and out. This requires surface retardation, which must be effective down to several mm.

In correctly designed exposed aggregate concrete, 2/3 of any single coarse aggregate is still within the hardened cement matrix.

Concrete strength

Concrete strength

Many factors influence the rate at which the strength of concrete increases after mixing. Some of these are discussed below. First, though a couple of definitions will be useful:

The process of strength growth is called 'hardening.' This is often confused with 'setting' but setting and hardening are not the same.

Setting is the stiffening of the concrete after it has been placed. A concrete can be 'set' in that it is no longer fluid, but it may still be very weak; you may not be able to walk on it, for example. Setting is due to early-stage calcium silicate hydrate formation and to ettringite formation. The terms 'initial set' and 'final set' are arbitrary definitions of early and later set; there are laboratory procedures for determining these using weighted needles penetrating into cement paste.

Hardening is the process of strength growth and may continue for weeks or months after the concrete has been mixed and placed. Hardening is due largely to the formation of calcium silicate hydrate as the cement continues to hydrate.

The rate at which concrete sets is independent of the rate at which it hardens. Rapid-hardening cement may have similar setting times to ordinary Portland cement.

Pumpability of Concrete

Pumpability of Concrete

The pumpability of concrete depends basically on the composition of the mix, the aggregates used and the method of delivery.

As far as the delivery and installation of pumped concrete is concerned, a significant reduction in the pump pressures and an increase in the output can be obtained by the systematic addition of pumping agents, particularly for use with crushed aggregates, secondary raw materials, highly absorbent aggregates etc.

Pumped concrete is used for many different requirements and applications nowadays. A suitable concrete mix design is essential so that the concrete can be pumped without segregation and blocking of the lines.

Composition

·     Aggregate

Max. particle < 1/3 of pipe bore

The fine mortar in the pumped mix must have good cohesion to prevent the concrete segregating during pumping.

·     Cement

Max. particle		Round aggregate		Crushed aggregate
8 mm		380 kg/m³		420 kg/m
16 mm		330 kg/m³		360 kg/m³
32 mm		300 kg/m³		330 kg/m³

·     Water/binder ratio

If the water content is too high, segregation and bleeding occurs during pumping and this can lead to blockages. The water content should always be reduced by using superplasticizers.

·     Workability

The fresh concrete should have a soft consistence with good internal cohesion. Ideally the pumped concrete consistence should be determined by the degree of compatibility.

·     Pumping agents

Difficult aggregates, variable raw materials, long delivery distances or high volume installation rates require a pumping agent. This reduces friction and resistance in the pipe, reduces the wear on the pump and the pipes and increases the volume output.

·     Pump lines

-  80 to 200 mm (normally  100, 125 mm)

- The smaller the, the more complex the pumping (surface/cross-section)

- The couplings must fit tightly to prevent loss of pressure and fines

- The first few metres should be as horizontal as possible and without bends. (This is particularly important ahead of risers.)

- Protect the lines from very strong sunlight in summer

·     Lubricant mixes

The lubricant mix is intended to coat the internal walls of the pipe with a high-fines layer to allow easy pumping from the start.

Conventional mix: Mortar 0–4 mm, cement content as for the following concrete quality or slightly higher. Quantity dependent on andline length

·     Effect of air content on pumped concrete

Freeze/thaw resistant concrete containing micropores can be pumped if the air content remains < 5%, as increased resilience can be generated with a higher air content.

Tunnel Segment Concrete

Tunnel Segment Concrete

Modern tunneling methods in unstable rock use concrete segments which are immediately load bearing as linings to the fully excavated tunnel section.

Precast concrete units called tunnel segments perform this function.

Production

Due to the large numbers required and heavy weight (up to several tones each), tunnel segments are almost always produced near the tunnel portal in specially installed precasting facilities. They have to meet high accuracy specifications. Heavy steel formwork is therefore the norm. Because striking takes place after only 5–6 hours and the concrete must already have a compressive strength of >15 N/mm², accelerated strength development is essential.

There are several methods for this. In the autoclave (heat backflow) process, the concrete is heated to 28–30°C during mixing (with hot water or steam), placed in the form and finished. It is then heated for about 5hours in an autoclave at 50–60°C to obtain the necessary demoulding strength.

Composition

Aggregate

·     Normally 0–32 mm in the grading range according to EN 480-1

Cement

·     Cement content 325 or 350 kg/m³

·     CEM I 42.5 or 52.5

Placing

·     The fresh concrete mix tends to stiffen rapidly due to the high temperature, making correct compaction and finishing of the surface difficult.

·     Due to the rapid industrialized process, a plastic fresh concrete consistence can be used. The desired initial strength can only be obtained by a low water/cement ratio, which should therefore always be<0.48.

Concrete with enhanced Fire Resistance

Concrete with enhanced Fire Resistance

Concrete with enhanced or high fire resistance means concrete which is improved so that it can withstand the defined high heat conditions. Concrete itself cannot burn, but above certain temperatures it loses first its mechanical properties and then its form. Without special measures concrete is normally heat resistant in service up to a temperature of about80°C.

Concrete with high fire resistance is used for

·     Emergency areas in enclosed structures (tunnel emergency exits)

·     General improved fire resistance for infrastructure

·     Fire resistant cladding for structural members

Properties of concrete with high fire resistance

·     As a rule the fresh concrete behaves like standard concrete during placing

·     The hardened concrete has a somewhat slower strength development than normal, but again the properties are similar

Production of concrete with high fire resistance

·     The concrete production does not differ from standard concrete

·     The mixing process must be monitored due to the fibers normally included

·     It is beneficial to the future fire resistance of this concrete if it can dry out as much as possible

Constituents for the production of concrete with high fire resistance

·     Achievement of maximum fire resistance is based on the composition of the aggregates used

·     The resistance can be greatly increased by using special aggregates

·     The use of special plastic fibers (PP) increases the resistance considerably

·     The use of selected sands improves the resistance of the cement matrix

Mechanisms of behavior in fire

The capillary and interstitial water begins to evaporate at temperatures around the boiling point of water (100ºC). Steam needs more space and therefore exerts expansion pressure on the concrete structure. The cement matrix begins to change at temperatures of about 700°C. The effect of the aggregates is mainly dependent on their origin and begins at about 600°C. Concrete starts to “melt” at about 1200°C.

Underwater Concrete

Underwater Concrete

As the name suggests, underwater concrete is installed below the water line, e.g. for

·    Port and harbour installations

·    Bridge piers in rivers

·    Water industry structures

·    Metro systems

·    Deep shafts in unstable ground, where an internal fall in the water level could lead to hydraulic ground heave, etc.

Composition

·     Aggregate

-       Use an aggregate suitable for pumped mixes

-       –Fines including cement > 400 kg/m³

·     Cement

-       Min. cement content 350 kg/m³

·     Special requirements

A reliable method of placing underwater concrete with minimum loss is the tremie process (Contractor method). The concrete is placed directly through a 20–40 cm pipe into and through the concrete already installed. The pipe is raised continuously, but the bottom end must always remain sufficiently submerged in the concrete to prevent the water going back into the pipe.

Another method also used today is pumping a suitably modified mix through a standard concrete pump. Here again, the end of the delivery pipe must be kept deep enough in the fresh concrete.

·     Other important considerations:

-       As the flow rate of water increases, more leaching can occur. Mini-mum flow conditions are best

-       Avoid pressure differences on the pipe (such as water level differ-ences in shafts)

·    Special underwater concrete

Previously installed rough stone bags or “gabions” can be in filled later with modified cement slurries (the bag method).

Mixing Water in Concrete

Mixing Water in Concrete

The suitability of water for concrete production depends on its origin.

lists the following types:

·     Drinking water

Suitable for concrete. Does not need to be tested.

·     Water recovered from processes in the concrete industry (e.g. wash water)

Generally suitable for concrete but the requirements in annex A of the standard must be met (e.g. that the additional weight of solids in the concrete occurring when water recovered from processes in the concrete industry is used must be less than 1% of the total weight of the aggregate contained in the mix).

·     Ground water

May be suitable for concrete but must be checked.

·     Natural surface water and industrial process water

May be suitable for concrete but must be checked.

·     Sea water or brackish water

May be used for non-reinforced concrete but is not suitable for reinforced or pre stressed concrete.

The maximum permitted chloride content in the concrete must be observed for concrete with steel reinforcement or embedded metal parts.

·     Waste water

Not suitable for concrete.

Combined water is a mixture of water recovered from processes in the concrete industry and water from a different source. The requirements for the combined water types apply.

Sub base Preparation – Concrete Placement

Sub base Preparation – Concrete Placement

Vapour barriers should be placed under all concrete ground level floors to prevent the transfer of moisture and soil gases such as radon gas. Sloping the landscape away from the building, placing a 100 mm granular sub base between the soil and the slab, adding a sub base drainage system, and using drain tiles and vapour barriers will reduce moisture problems.

After new concrete is poured and hardened it is roughened to make a better bond with the next placement. Wood forms should be oiled or treated with form release agent to prevent damage to the concrete when they are removed. Reinforcing bars should be clean and without loose rust and scale. Concrete should be placed as close as possible to its final destination. The placed concrete layer, usually 300 mm in depth, should be consolidated, and made uniform and horizontal, before the next layer is added. Concrete should not be poured into piles and placed by moving it horizontally because it will segregate as the cement and water mixture moves ahead of the aggregate. 

Concrete slump test

Mastour ReadyMix provides its customers with high-quality branded Ready mix concrete and cement products for their construction needs

The concrete slump test is an empirical test that measures the work ability of fresh concrete.

More specifically, it measures the consistency of the concrete in that specific batch. This test is performed to check the consistency of freshly made concrete. Consistency is a term very closely related to work ability  It is a term which describes the state of fresh concrete. It refers to the ease with which the concrete flows. It is used to indicate the degree of wetness. Work ability of concrete is mainly affected by consistency i.e. wetter mixes will be more workable than drier mixes, but concrete of the same consistency may vary in work ability  It is also used to determine consistency between individual batches.

The test is popular due to the simplicity of apparatus used and simple procedure. Unfortunately, the simplicity of the test often allows a wide variability in the manner that the test is performed. The slump test is used to ensure uniformity for different batches of similar concrete under field conditions,  and to ascertain the effects of plasticizers on their introduction

Welcome to Mastour ReadyMix

It is a subsidiary of Mastour Holding Group , which was established in 1978 , It is working in the field of ready-mixed concrete and cement products , as well as some other miscellaneous activities .
The company has the experience and achievements that make them among the major companies operating in this area, they have the technical personnel of the fleet and operational enough to be as well.
And the importance of quality and its impact on the construction of the country , has been the slogan of the company :

Together... To Build the Country with High Quality

And to investigation of the company's slogan , Were processed the laboratories on the latest models and equipment, attracted the best professionals to maintain the quality of their products to Attract customers by quality of the product .