The amount of concrete yield you receive, unload, and pour into your forms or frames is hardly set in stone. According to this whitepaper from the National Ready Mix Concrete Association, yield can vary due to factors ranging from air temperature, distance, and time traveled to the ratio of concrete/air/water to concrete supplier discrepancies to the way you measure and weigh the delivered product.
How can you plan for and deal with yield discrepancies?
Six steps for fewer concrete yield discrepancies
To prevent—and more fully manage—any concrete yield discrepancies, consider taking the following steps:
- Check yield using the ASTM C-138 unit weight test method on three samples from three different loads (yield is the total batch weight divided by the average unit weight or density).
- Accurately measure volume density by using an accurate, externally clean scale that’s placed on a level surface, remembering that total batch weight = the sum of the weights of all materials from the batch ticket. You can then reevaluate your volume required towards the end of the pour, provide your estimate to the concrete producer and adjust your order for a few loads to have the optimal amount of concrete. This step helps you avoid the need for short loads after the plant has closed, or having to deal with unavailable delivery trucks and costs for returned concrete.
- Estimate any extra concrete you’ll need (for example, include an allowance of 4-10% over plan dimensions for waste, over-excavation, etc.). Note that repetitive operations and slips form placement enables you to make more accurate concrete estimates, while sporadic operations like alternating placement in slabs, footings, walls, incidental fill around pipes, and the like require larger margins of error.
- Construct your forms with enough bracing and shoring (especially if you’re using elevated slabs) to minimize deflection and bulging.
- For on-grade slabs, accurately finish and compact the subgrade to the property elevation.
- Use technology that lets you quickly determine jobsite yield, monitor real-time truck locations and load-level summaries, view records of load status times, and automatically match incoming delivery tickets with hauler pay sheets and invoices. Or take a look at in-truck probes that let you remotely check your slump while it’s in-transit so you can quickly recognize and reject out-of-spec loads.
Many construction companies are turning to smart jobsite technology to empower their crew and project managers, increase productivity, improve job oversight, and avoid costly errors and delays.
Get more information on how to CONNEX Jobsite keeps tabs on job cost tracking, material order and delivery management, traceability of critical path materials, and material quality assurance information all in one centralized location.
Also, learn how COMMANDassurance provides instant updates on your in-transit slump.