This is What Prevents Ready-Mix Concrete from Spilling from a Concrete Mixer Truck

Many people are curious about how liquid concrete mixture doesn’t spill while being transported by a concrete mixer truck on the roads. Yet, this vehicle often travels on various road conditions, from straight to undulating paths. It turns out there is a technical mechanism that keeps the concrete safe inside the drum during the journey. This system involves the direction of the drum’s rotation, the design of the spiral blades inside it, and the proper operation techniques. Summarised from the Ministry of Public Works and Housing, one of the main keys is the direction of the drum’s rotation. When carrying concrete, the mixer truck’s drum rotates counter-clockwise, known as the “mixing” direction. This rotation prevents the mixture from being pushed out; instead, it holds it inside the drum. Inside the drum, there are spiral or helical blades made of steel that resemble threads. When the drum rotates in transport mode, these blades function to push the concrete inward. Thus, even though it’s in liquid form, the mixture stays inside and doesn’t spill. Without this rotation, the materials in the concrete could separate. Moreover, the concrete risks starting to harden before reaching the project site. Interestingly, this rotation direction is reversed during the pouring process. When the truck arrives at the site, the drum is rotated clockwise so that the spiral blades push the mixture out from inside the drum. It’s important to note that the drum’s rotation is not just an additional feature but an absolute necessity in concrete transportation. If the drum stops rotating for too long, the concrete can start to harden in about one hour. This condition not only damages the concrete’s quality but also potentially damages the mixer drum itself.