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Would You Drink it?

The rule of thumb when you’re looking at an aggregate for use in your mix designs is to pay attention not only to its dispersion across the screens, but more importantly the percentage of material retained on the pan. The retention on the pan passing the #100 sieve being usually around 6 percent or less. The reason for this is that the particle size passing the 100 screen is small enough that it can actually inhibit the crystalline growth that is a byproduct of cement hydration. The finer the mix, the more cement is needed to cover the aggregate particles. Another potential culprit for adding excessive fines, is your mix water. Ideally, your mix water should be potable as a result of it being either city water or has gone through a filter and softening process. Pulling water directly from a well could be as detrimental as having high fines content in your aggregates. If you’d like to do an in-house check, take a small amount of your mixer water and place it in a clear glass cup. Place a coffee filter over the top of the glass and let the water evaporate. When totally evaporated see what’s left, if it’s clear that’s great.  If it’s hazy or you can see deposits, you may want to address your filtration methods. For more information contact Production Specialist Mike Maroney.

Single Minute Exchange of Die

Changing a product mold in our industry is never a matter of “if,” it’s strictly a matter of “when.” As such, that change out time is critical to the production flow. We’ve seen operations that approach a mold change like a race-car pit crew during production and other operations that do it at the end of the shift while clean-up is occurring. The assumption is that it is a constant work in progress to transition from one product to the next in an efficient and timely manner.  Lean Manufacturing has a term for it; SMED, or Single Minute Exchange of Die. SMED is a process driven method of reducing changeover times through observation and evaluation of the steps involved. It’s a method discerning what can be done while the equipment is running or can only be done while the equipment is stopped. This will result in external and internal procedures that can ultimately cut down the time needed for a mold change without compromising unit quality. For more information contact Mike Maroney.

Batch Control Software

We have a tendency to focus on the mechanical aspects of our products as they go through the manufacturing process. From when they strip out of the block machine, transferring into the kilns, processing through splitters or antique finishing machines, and ultimately being palletized and rolling out of the plant. It’s all visual and sensory based with mechanical steps and audible cues. What we don’t think about though is really the heartbeat of the system, this being the batching control software that maintains the cadence of the operation. You can’t see or hear the calculations made on a batch-by-batch basis, but it’s critical to an operation’s success that the functions and steps are fully understood by personnel. Take the time to get to know your Batch Control Software, for more information contact NCMA Production Specialist Mike Maroney.

Hustle and Flow

The old adage is that the block machine only runs as fast as the batched mix allows. There are several aspects to this, but we are going to focus on one — water demand. All of us are aware of the water-to-cement ratios that govern cement hydration and workability. As an example, I run a fine textured architectural mix with a water-to-cement ratio of 0.59. The cement only requires a .22 to .24 water to cement ratio to begin hydration, everything past that is water of convenience. Along with or without admixture, the water of convenience allows the batch mechanically move from sub-hopper to feed drawer to mold in relatively fluid motion. There is no standard water cement ratio. There are ranges which are utilized based on the mix gradation. Rule of thumb: the finer the mix, the higher the water cement ratio. Whereas, my Architectural Fine Texture mix requires a .59 water to cement ratio, my standard sand and gravel blend may only require a .51 water-to-cement ratio. For more information, Ask Mike.