A common sight …
Concrete trucks are a common sight on construction sites and highways. Hardly surprising as there are over 70,000 of these vehicles on the roads in the USA (National Ready Mixed Concrete Association, 2022).
These large, cylindrical vehicles are used to transport and deliver concrete to various locations. The average truck carries 8 – 10 cubic yards, however larger trucks can carry up to 14 cubic yards. For smaller jobs or where access is difficult, smaller trucks carrying 4 cubic yards are available.
In this blog post, we will explore the history of concrete trucks, the different configurations available, how they work and the various components that make up these important machines.
In 1904 a German inventor, Richard Bodlaender, patented a “mobile mixer”. It was essentially a horse drawn cart where the front wheels had been replaced by a large drum containing paddles which churned the concrete as the horses pulled the vehicle forward. It was very heavy and slow and, understandably, unpopular with the horses.
Although his initial attempts to patent his 1916 invention failed, Stephen Stepanaian is seen as the inventor of the motorized “transit mixer”. Meanwhile, in 1920 a Kansas inventor Ackert Bickel patented his concrete truck which was called “Apparatus for Concrete Work”.
These trucks had a horizontal drum and were powered by an internal combustion engine. Development on these machines continued and through the 1930s demand increased as more and more highways were built. Improvements included the ability to tilt the drum, to facilitate delivery, and water tanks to allow more time before the concrete had to be discharged.
The concrete truck is essentially a mobile concrete batching plant. It consists of several components, including the mixer, the drum, the chute, the water tank, and the engine.
Let’s take a closer look at each of these components:
1 The Mixer
Mixer: The mixer is the heart of the concrete truck. It is responsible for mixing the various ingredients that make up the concrete, including cement, water, and aggregates (such as sand, gravel, and crushed stone). The mixer is typically a rotating drum that is mounted on the truck chassis.
2 The Drum
Drum: The drum is the cylindrical container that holds the mixed concrete. It is made of high-strength steel and is designed to withstand the rigors of transporting and pouring concrete. The drum can be rotated in both directions to agitate the concrete and prevent it from settling or hardening. In one direction the contents are forced against gravity to the bottom of the drum, agitation and mixing the content.
Courtesy “Marta Ambrosetti, DensityDesign Research Lab” – https://en.wikipedia.org/wiki/en:Creative_Commons.
In the other direction, the contents can be pushed out of the drum enabling the discharge process.
3 The Chute
Chute: The chute is the long, flexible pipe that extends from the drum of the truck to the point where the concrete is being poured. The chute is usually made of rubber or plastic and can be angled and positioned to deliver the concrete precisely where it is needed.
4 Water Tank
Water tank: The water tank is an integral component of the concrete truck. It holds clean water that is used to mix with the other ingredients to create the concrete. The tank is typically located near the cab of the truck and can hold several hundred gallons of water.
5 The Engine
Engine: The engine is what powers the concrete truck. It is usually a diesel engine that provides the necessary torque to rotate the drum and drive the truck. The engine is also responsible for powering the hydraulic system that operates the mixer and the chute.
Now that we have explored the various components of the concrete truck, let’s take a look at how it works:
- Loading: The first step in the process is to load the ingredients into the mixer. The cement, aggregates, and water are typically loaded in predetermined amounts according to the desired mix design.
- Mixing: Once the ingredients are loaded, the mixer is activated, and the drum begins to rotate. The rotating action helps to mix the ingredients thoroughly, ensuring that the concrete is consistent and homogenous.
- Transporting: After the concrete is mixed, the truck begins its journey to the construction site. The drum continues to rotate during transit, keeping the concrete in a liquid state and preventing it from hardening.
- Pouring: Once the truck reaches the construction site, the chute is positioned and the concrete is poured into place. The operator can control the flow rate and direction of the concrete by adjusting the position of the chute.
The design and technologies within concrete trucks continue to evolve bringing greater efficiency and effectiveness into the construction sector.
In conclusion, concrete trucks are a critical component of the construction industry. They provide a mobile and efficient way to transport and deliver concrete to construction sites.
Understanding how these machines work helps us appreciate the complex engineering and design that goes into making them.