Concrete pumping is the final, critical link in the journey of ready-mix concrete from a batching plant to various heights and depths on a construction site. These operations require expertise in selection of the appropriate stationary or mobile pumps, installation and testing of the pumps, and scheduling concrete batching and delivery according to real-time construction activity. The total amount of concrete required for a construction site is usually specified for the entire year, and monthly delivery schedules are finalised in advance.
In practice, concrete delivery and pumping schedules for construction activities, such as piling, are confirmed a day in advance by the enabling works contractor in accordance with the quantity of concrete required for the day, and the progress of drilling and installation of reinforcing steel cages. To find out more about the concrete pumping process and its logistics, Construction Week joined Unibeton Ready Mix on one of its ready-mix concrete delivery and pumping operations in Dubai.
The construction site was of the Medium Pyramid hotel apartment building at the Falconcity of Wonders, where Middle East Foundations Group, the enabling works contractor, is completing piling works.
The Medium Pyramid (B+G+19 +health club) is one of three pyramids – named Small, Medium, and Large – to be built at the Pyramids Park in Falconcity of Wonders, emulating the Egyptian architectural wonder. According to the developer, Large Pyramid will be the biggest pyramid ever built and will function as a mixed-use complex comprising residences, offices, and other recreational avenues.
Since June 2018, Unibeton has delivered 26,000m3 of concrete to the Medium Pyramid site for the construction of 520 piles. Each pile required 50m3 of concrete transported in five mixer trucks and poured through a truck-mounted concrete pump. Drilling at the Medium Pyramid site was done at night, and reinforcing steel cages were installed early in the mornings. As a result, concrete piling work was conducted during daytime.
Senior general manager at Unibeton, Talaat Mouin Abdul Karim, explains the ordering and delivery process: “We produce concrete batches for piling according to the mix design specified by the enabling works contractor. The concrete strength specified for this project is 60N/mm2. The enabling works contractor also confirms the ready-mix concrete quantity required for a day and the time of pumping. Once we receive the booking, we assign truck-mounted pumps to the site,” says Karim.
The order is reconfirmed on the day of the pumping and Unibeton starts concrete batching only after the installation and testing of the concrete pump by the company’s staff. This allows the company to dispatch its mixer trucks in a way that allows them to arrive on site just in time for slump testing and concrete pumping.
When a truck-mounted pump reaches its site, Unibeton’s staff inspects the entrance and access points for pump installation and ensures that the land is well compacted for stability of the pump.
“Selecting the right location for installation of the concrete pump is a crucial part of the process. If the land is uneven or unstable, we alert the enabling works contractor to compact the [space]. Only then can we install and test the pump,” says Karim.
Unibeton assigns up to four staff on site for quality control, supervision, and assistance. This group includes a supervisor, a technician for slump tests, a concrete pump operator, and a helper.
“The quality control process starts with the batching of the concrete, followed by slump tests at the batching plant as well as on site, in order to ensure the consistency of the concrete in accordance with the mix design. Subsequently, the concrete is approved for pumping. If the slump value is low, the pump will not be able to function, and the batch will be rejected from the site,” says Karim.
Unibeton maintains a fleet of 253 mixer trucks and 61 truck-mounted, mobile concrete pumps in the UAE to transport and pour ready-mix concrete. The company’s mixer trucks have 9m3 and 12m3 capacities, and the average output capacities of its concrete pumps is 70-80m3/h.
According to Karim, a delivery of 50m3 of concrete would require five 12m3 mixer trucks. High-slump concrete is used for piling, and so, the trucks are loaded under full capacity in order to maintain the consistency of the concrete and avoid spillage on the road.
“We are able to batch and deliver ready-mix concrete within an hour after receiving confirmation from the site. The concrete batching process requires about 5-7 minutes, and it is delivered to the site in 50-60 minutes,” says Karim.
The time required for concrete pumping is almost the same as that required for batching. Each mixer truck takes 7–8 minutes to transfer all its concrete to the pump. If the time required for the trucks to enter and leave the site and connect with the truck-mounted pump is considered, it takes about an hour to pump 50m3 of concrete for a pile.
“The amount of concrete to be pumped for piling depends on the dimensions of a pile and its load bearing requirements. It’s common for construction sites in the UAE to have 100m3 of concrete per pile. We pumped 250m3 of concrete to construct a single pile at the Shindagha Bridge project in Dubai,” says Karim.
Unibeton is not a stranger to pushing the boundaries of concrete pouring. In 2016, the company set the Guinness World Record for pouring more than 19,793m3 of concrete continuously for 42 hours at Geepas Tower in Al Barsha, Dubai. The concrete was delivered using 300 mixer trucks that made more than 2,500 trips from three plants, and concrete pouring work was carried out with 14 pumps on site. An additional five pumps were on standby. Six hundred workers were employed in multiple shifts to work round-the-clock and complete the job.
One of the popular truck-mounted concrete pump models used by Unibeton regularly is the Schwing Stetter S42SX, which has a maximum vertical reach of 42.1m and horizontal reach of 38.1m.
Its maximum concrete output is 162m3/h at a maximum pressure of 85 bar on the concrete. The turret can be rotated 370° in either direction and the tip section can rotate 240°.
“The length of the boom determines the reach of the pump in a piling area. The longer the boom, the more the concrete piles can be covered by a truck-mounted pump from a fixed position of the truck. This saves time and avoids the need to create access points on large sites, particularly those with low-quality soil,” says Karim.
“Concrete pumps such as the Schwing Stetter S42SX are workhorses designed to operate 24 hours. We’ve used Schwing Stetter pumps to deliver 800m3 of concrete in 24 hours at an average rate of 40m3 per hour for a foundation project in the UAE. Such pumping capacities have been tried and tested and can be guaranteed for any project.”
Karim elaborates on the company’s maintenance process for concrete pumps, which he says is vital to avoid project delays: “Truck-mounted concrete pumps move from one site to another, and we often assign a pump on two or three sites a day. Generally, we assign a single truck-mounted pump to a site, unless it’s a large project that cannot afford downtime and requires standby pumps.
“The common issue facing mixer trucks and pumps is breakdown and related downtime costs. We have implemented scheduled inspection and maintenance processes to avoid such issues. It’s relatively easy to fix a truck. However, a concrete pump breakdown could cause significant delays. Therefore, we do not compromise on the quality or maintenance of our concrete pumps,” says Karim.