CONCRETE TRUCK AT OPERATION

Is it enough just to have a heavy vehicle license to be a mixer driver?

The answer, of course, must be no! Although the mixer is generally defined as a truck-mounted equipment, it has different features from all other trucks traveling on the highways, roads and also at the construction sites.

The center of gravity of the concrete trucks is high and its location changes at any time due to the constantly moving concrete in the drum. With the effect of centrifugal force created by the rotating drum, the concrete truck seems ready to rollover at any moment!

In addition to these, there are some limitations depending on the load carried by the mixer ie the concrete. Wet concrete must be mixed during the entire transport to preserve its properties. Also it has to be poured into the forms within 60-120 minutes after it is filled in the drum at the plant.

There are some companies that see the concrete truck drivers as concrete experts

when they enter the site and expect them to take all responsibility for the product once it is loaded into the drum. Therefore the basic concrete knowledge in any case is important for concrete truck drivers.

On the other hand mixer drivers have a very important role at the dispatch starting from filling the concrete to the vehicle in the plant and pouring it into forms or pumps hopper at site. And all concrete truck drivers should be aware of this duty at all stage.

The content of this handbook consists of necessary information for the safe operation of concrete trucks. All concrete truck drivers may find some new and important information that they have not encountered so far. That’s why I recommend reading this handbook and even working on some topics together with colleques.

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PUMPING CONCRETE DOWNWARD

Which is more risky pumping upward or pumping downward?

If the pump is setup closer than the safe distance, there is a danger of overturn the machine. Do you know what may happen to the outriggers if they are opened partially or none when the pump works close to a pit with fully unfold boom? They cannot withstand the additional forces and may break. And do you consider any precaution while working next to a pit with a big boom? Or do you completely trust your operator and leave the results to fate?

Setting the machine on the edges of pits, trenches and gaps away always cause a danger. This is frequently encountered in construction sites and more common in large projects during pumping down with big booms. The general rule here is defined as one-to-one or minimum 2 meters. However, while pouring the concrete down with big booms often this is impossible.

What should the operator do and do not in this case? Think that there are some additional hoses used out of rules in order to increase the total length. The boom is full of concrete up to the end of the last hose. And the operator bends the hose. Then calculate the effect of extra load in the boom.  And if he tries to move the machine a few meters with open boom and full of concrete. Unfortunately, pump operators have difficulties in such applications and the pumps are operated without static and dynamic calculations. It is obvious that this job cannot be left to the operator alone!

On the other hand, in case of an accident who will be the  responsible by law? Possible justifications and claims may be as  follows:

-The site chief says that the responsibility of the pump belongs entirely to the operator.

-The insurance company justifies that the safe distance is written on the machine. And it doesn’t make the payment.

-Does the operator automatically accept all warning signs indicated on the machine?

-Can the RMX company claim that this distance limitation clause is not specified in the policy even it is written on the machine?

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CONCRETE PUMPS AT OPERATION

Do you have a performans plan for each pumping operation.

-What reduces efficiency in the boom pumps operations?

If the answer is given with a single word, changing the setup location. This is not an easy precaution to take. However, poor planning may require more displacement than anticipated. This means loss of time and production at work. When you are working at a site, it is crucial that you manage time correctly and no labour or time is used up unnecessarily. Planning and timing is the key to productivity for ready mixed concrete companies as well as contractors.

-It is essential to use the pump efficiently in operations.

The first choice in this regard should be the determination of the boom length. Ideally, the boom should be as close to the building as possible, with easy access to all formwork without machine displacement i.e. in one setup.

-Replacing the pump location during the operation.

Now the boom sizes have grown a lot but still in many projects it is not possible to carry out the entire concrete pumping operation with a single setup. Nothing kills productivity like pump displacement in the middle of pouring. Sometimes this may become mandatory but unplanned relocations are the worst. Because they take more time and this can also cause cold joints in concrete. Therefore for setup the best and also alternative different locations, if any should be determined in advance.

-Time for replacement to relocate the pump.

The operator must first fold and close the boom. With the open boom displacement of the truck are forbidden in any case even a few meters. After the boom and the legs are collected, the pump truck is moved and the legs are re-setup in the new location then unfold the boom. This process can take at least one hour even more for pumps with large booms again to reach the concrete pouring position. For smaller boom pumps, this time may be less. But, in any case the displacement and repositioning of every size boom pumps is a serious event for efficiency in concrete operations.

-Enough space for mixer trucks.

There should be areas in the field where the mixer trucks can safely wait, even for a short time and they should be able to exit back and forth after safely discharging the concrete into the pump hopper. It is better to come from one route and return from another route after unloading. But more importantly, it is experienced in terms of efficiency. The approach of concrete mixer trucks in the new positioning of the pump will be re-determined and a risk assessment will also be required for them.

-Pump setup early in the morning.

Determining the pump setup location well and completing the operation without relocation is a very important issue for both safety and efficiency. Re-searching suitable ground and assessing other risks means wasting time. Another problem in this regard is that the concrete pumps go to the construction site mostly in the early hours and the appropriate place must be selected before the sun shines. And then the machine is relocated during the operation due to this lack of visibility. For this reason, making the pump setup planning one day in advance is of great importance for safety and efficiency.

Fast pumping to compensate lost time.

What we lose in fast pumping is more wear and more fuel. In concrete pumping operations, the pumps are operated at fast speed to compensate for the time lost due to machine displacement or other reasons. The contractor may insist on rapid pumping to make up for lost concrete volume. Maybe there’s no harm in that. However, faster pumping means more fuel consumption and also more wear on some wearing parts. On the other hand, the maintenance cost of the machine is also increased.

-Planning for cleaning.

Each pump operator should be prepared in advance by a performance program for the operation. Everything should go within the program, including moving the pump truck. The operation manager should prepare the performance program together with the other relevant parties. For pumps with a boom over 50 meter, 30-45 minutes are allocated for the cleaning process. The most practical cleaning method is by pushing the sponge ball from the hose end. Concrete is sucked along the boom and discharged into the hopper. It is not recommended to move the machine with concrete in the boom and in case of concrete hardened including the valve, the cost can reach 15-20 thousand of Euros. At least there should be enough washing area for preliminary cleaning of pumps and mixer trucks at the operation site. Apart from this, a discharge place is required for the material left in the pump hopper and the mixer drum.

This E-Book, is consisting of fwg topics; pouring concrete operation management, performans plan, risk analysis, concrete pumps and safety, problems of big boom pumps, safety precautions, , who is responsible for safety, machine factors, human factors, site factors, preparation for operation, at the operation, evaluation of the operation etc.

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CONCRETE CONVEYING HIGHRISE BUILDINGS

Selecting right equipment and pumpable concrete and safety issues

-With modern concrete pumps, building heights have reached hundreds of meters. The record for today is about 600 meter and an engine of approx. 500 kw was used in the pump. However, the powerful concrete pump alone is not enough for such performance. Increasing the speed and volume of conveying concrete and the total performance are not only depending on pump. But the other factors such as suitable pipeline system, using right placing boom, concrete receipe, safety precautions and trained as well as experienced people are also important.

-All construction projects are the areas of potential danger! However with the selection of right equipment and personnel training these hazards can be eliminated. Unsafe working causes many injuries and breakdowns and interruptions in work. Safety is the most important factor that you can complete the job in the shortest time and at the least cost. Placing line, straight sections, bends and elbows should be chosen by knowledgeable and experienced people who know in certain areas the line must not be rigid but flexible. The use of placing booms and other special equipment has made the training more important for safety.

-Increasing the cross section of the line has a direct influence on the flow rate, the wear behaviour, the pressure requirement and the period for which the concrete remains in the pipeline given the same output per hour. On the other hand under high pressure concrete pump, delivery line and special equipment are always dangerous during pouring. All components of the system must be able to handle the maximum internal pressure. In addition, cleaning operations at the end of pouring can only be done by trained personnel. Do not think that it is simple job and can be done by ordinary workers. Injuries are mostly experienced during the cleaning phase.

-The rate of wear varies greatly. Hard aggregate is of course more abrasive than a softer aggregate . In addition to physical characteristics of the concrete, wear is also affected by the concrete volume conveyed, material velocity, pumping pressure and geometry of the system. You need also an accurate concrete recipe, because you can’t just rely on chemicals. The nature of the materials both facilitates the flow of concrete and provides a permanent advantage in concrete. For highrise building projects, sometimes the pipeline cost may take priority over the pump. And many problems can arise if the pump cannot produce enough pressure. For example, the material may get stuck in the line, causing the pipe to burst and the connections to break.

-This book is prepared to provide basic information for selecting right equipment and preparing pumpable concrete and safety issues. Therefore all staff  not only operative personel like pump operators, their assistants and other workers in the field, but also for the people who make preliminary work of any highrise building project can also benefit.

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READYMIX BIG BOOM PUMPS


Why we stuck in a 4 axle truck!

-The modern buildings in the cities are all going vertical and readymix companies need to big pumps. However the use of these truck mounted big boom pumps have some problems.

-First of all the ROI of high cost of the big boom pumps are not easy as the ones used in projects which can compensate this in the total budget of the construction.

-In the readymix business each pouring operation should deserve the machine on its own. Therefore the amortization period could not be short as 40-30m boom pumps. Because it is obvious that you can not everyday find a job for these big boom pumps.

-There is also operator problem. Because another guy may be the third one should assist him, in any case, to check the pumping units and outriggers while the operator following the boom-end at a close distance. Cleaning is also another issue…

-The operator of big boom pump should be paid more than the other operators using 30-40m pumps. But when you can not find a job for this pump and send the operator with a standard pump what will happen in terms of salary and income justice for pump operators within the company?

-But the main problem for the big pumps used in readymix is another subject. The design limitations*. These machines are considered as truck-mounted equipment and the GVW cannot exceed 32 tons for 4-axle truck on the roads. In some countries highways do not allow five-axle rigid trucks.

-There is a clear need for 5 axle rigid trucks not only for concrete equipment also for municipal and some other vehicles. There are even 6 axle chassis working with special permits supplying safe, economical furthermore functional in the countries where that this truth is seen.

-It is said that this was prevented in Turkey years ago in order to stimulate the use and accordingly sales of truck tractors. It is certain that maneuverability of truck tractor + trailer combination is better. But the need for 5-axle rigid chassis is also obvious.

-To solve this weight problems, manufacturers are constantly looking for lighter but stronger steels. This causes the material to be resistant to longitudinal loads, but to be weak in transverse and breakage.

-On the other hand manufacturers competing in the cheap segment use the lowest level of steel in its class. That means the price difference** which cannot be ignored starts with the boom material from the very beginning. In this point we must say that these pumps visits the workshop more often. And it goes without saying that this shortens the life cycle of the machine.

*This limitation is for on-road and not for off-road trucks.
**Price difference is at least 30-40 pc of the total cost.

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