How Can One Prevent Cement from Hardening in a Concrete Mixer Truck?

Drivers in my area often keep a few bags of sugar in their cabs. In case they cannot offload the concrete due to traffic or mechanical issues, they mix sugar into the batch, significantly delaying its hardening. However, in situations where the concrete cannot be mixed or mechanically delayed, other methods can be employed.

Methods to Prevent Concrete from Setting in a Concrete Mixer

There are several methods to prevent concrete from setting in a concrete mixer. These include:

1. Initial Water Addition Method

On extremely hot days, adding slightly more water than required works well. This method helps delay hardening by keeping the mix more fluid.

2. Incomplete Mixing Method

Not fully mixing the water, aggregate, and cement will result in a workable concrete that can be mixed later as needed.

3. Slow Drum Rotation Method

Maintaining a slow rotation of the drum helps in more thorough mixing and prevents the concrete from setting prematurely.

Furthermore, concrete hardening is a chemical reaction that can be partially delayed using additives. However, movement of the mixer drum does not have a significant effect on this reaction but can affect the distribution of components within the concrete mix.

Concrete Hardening Process and Its Prevention

The hardening process of concrete is based on a chemical reaction that begins once the concrete is loaded and mixed. If the concrete is unable to be used within a certain timeframe, it must either be dumped or allowed to solidify in the drum, often necessitating an overall replacement or the laborious process of chipping the concrete out of the barrel. Dumping or removal often results in additional costs and can be legally challenging.

Concrete needs to be mixed to set up properly, not to prevent setting. Keeping a load waiting too long may result in two scenarios:

- The driver will dump the load wherever he is, and the cleanup process is expensive and often not covered by insurance.

- The driver will return to the yard, where the charges for removing and replacing the truck barrel apply, or you might have to hire a laborer to chip the concrete out of the barrel. This is not only costly but also not covered by insurance.

Therefore, proper planning of your concrete pours is crucial to avoid these complications. Timing and logistics must be managed carefully to ensure that the concrete does not harden prematurely in the mixer truck.

Conclusion

The methods discussed above offer practical solutions for delaying the hardening of concrete in concrete mixer trucks. However, it is essential to monitor the time and conditions carefully to avoid unnecessary costs and risks. Effective planning and communication with your crew can significantly reduce the likelihood of issues arising from concrete hardening delays.