August 31, 2018
Concrete balls. How to prevent them.
So, you have balls appear in your concrete from time to time? Maybe they always happen at one plant but not others? Maybe they happen so rarely that you have just accepted it? If any of these situations are true, read on to catch the highlights of everything to check with some examples.
What is a concrete ball made of? In almost every case a concrete ball of made up of cement, sand and moisture. I say moisture because it does not have to be free water or even water at all I some extreme cases. It could be large quantities of admix that trigger it in some cases. The generally universal ingredient is the presence of moisture and the absence of rocks at the same time with cement and sand. So what are some possibilities?
- High moisture sand
- Water or high volumes of admix added at the same time sand and cement are entering the truck.
- Water, sand and cement going into the truck together (minus rock)
Now what are some examples to check that we have seen?
- A water valve that leaks. Even smaller amounts can cause balls. In one particularly difficult case to troubleshoot, one customer had a water valve that leaked ONLY when cement was flowing. This was only discovered by accident when a truck prematurely pulled out from under the plant one day in the middle of discharging and the water was clearing visible.
- An aggregate scale that discharges sand alone first rather than a mixture of sand & rock. If this is the case, try reversing the weigh up order of the aggregates.
- A single mix design with a large quantity of admix. If this mix has been identified as the mix causing balls, try changing the discharge settings of your batching system to discharge the admix after the rock begins discharging.
- A single mix design that weighs up sand & rock in a reverse order from every other mix. If this mix has been identified as the mix causing balls, try reversing the weigh up order of the aggregates.
- Also try draining the overhead sand bin (water dripping from the gate would be a dead giveaway). Then try having the loader operator pull from higher up in the pile to get the drier material.
One important thing to note is that absolutely none of these can be troubleshot from the batch office. It takes physically being on the plant to watch each area to narrow down and eliminate the possibilities. Maybe you have another example? Maybe you have tried all of these solutions and still cannot solve your issue? Either way, give us a call. We would love to here your examples and of course we would be happy to help.
We would love to hear abour your experiences and of course let us know if we can help your company.