Calibration and Quality Control
Producing high-quality concrete begins long before the first yard is discharged. Volumetric mixers are much more accurate than a batch plant that is working just from weight. BUT that accuracy depends entirely on proper calibration and regular quality control procedures. A machine that is out of calibration by only a few percent can produce concrete with the wrong cement content, incorrect water-to-cement ratio, or inconsistent air content. These issues can lead to failed tests, unhappy customers, and unnecessary costs.
At Site-Mix Concrete, calibration is considered scheduled preventative maintenance. Every operator is responsible for ensuring that the truck is producing concrete exactly as designed before it arrives on a customer's jobsite.
Our objective is simple:
Produce every mix to specification.
Deliver consistent quality from the first yard to the last.
Verify our equipment rather than assume it is correct.
Document all quality control activities.
Cross check tests performed by operators by senior managers and QC personal.
Verifying Material Discharge
The most basic process of calibrating a volumetric concrete mixer is verifying that each individual material is being dispensed accurately from the truck. Every ingredient is tested independently to ensure the machine is delivering the correct amount according to the approved mix design. The coarse aggregate (stone), fine aggregate (sand), cement powder, water, and each admixture are discharged separately into calibrated containers and measured by weight and compared to their target values.
This process confirms that every material delivery system is operating correctly and are calibrated before the materials are combined into concrete. By verifying each ingredient individually, we ensure the proper proportions are maintained, resulting in consistent slump, strength, yield, and overall concrete performance from the first yard to the last.
Yield Box Testing: Verifying We Produce
One of the biggest advantages of volumetric concrete is the ability to precisely control the amount of concrete we are producing for the specific needs of the job and contractor. After each component is calibrated and tested, it is time to back check the whole process. A yield box is used to verify the amount of concrete being produced. To ensure our trucks are delivering exactly one cubic yard when programmed to do so.
A yield box is a certified container with a known volume. By producing concrete into this box and measuring the finished volume, we can verify that our equipment is accurately proportioning cement, aggregates, water, and admixtures. This process confirms that our calibration is correct and that our customers are receiving the quantity of concrete they are paying for.
During each yield test, we also document important quality-control information, including:
Mix design
Slump
Air temperature
Aggregate moisture conditions
Truck number
Operator
Date of testing
If the results indicate even a minor variation, the truck is recalibrated before returning to production.
Unlike rough estimates or improvised containers, a certified yield box provides an accurate and repeatable method of verifying concrete production. It's just one of the many quality-control measures we use to ensure every load leaving our plant meets our standards for accuracy, consistency, and performance.
