When to Use Aggregate Blending Constraints

In a previous blog post on material blending we touched on some of the reasons why a user might want to employ material constraints while blending multiple aggregate products.  I would like to expand on those reasons and add a few more to the list.  The mathematical and visual blending tools available in StonemontQC for aggregate, asphalt and concrete materials are very robust and powerful.  Each of these blending tools will allow the user to constrain the aggregate blend percentages while attempting to meet a specification or target.   There are many practical reasons to use aggregate blending constraints when blending.
Ensure the Use of Low Cost or Waste Materials
Cost conscious producers know that incorporating suitable low cost surplus material into their blends not only helps off-set the use of more expensive materials but has the added benefit of using stockpiles of a product that might otherwise need to be hauled away at an additional expense.  Many of these by-products go through the same plant processes as any other material and are of the same inherent quality.  Just be sure that the materials are properly tested and suitable for the intended purpose.  Set a minimum percentage of these materials in your blend and start using your waste piles.
Create a Better Balance of Material Consumption
Aggregate sources don’t produce all materials at the same tons per hour.  Rarely does the demand for products match the plant’s output either.  Setting up blend percentage constraint’s that more closely match a source materials output and demands can help keep plants in balance ensuring that every rock gets sold.  This takes a special attention to detail and a thorough evaluation of inventories and production and shipping tonnages.
More Accurate Batching
The aggregate blend looks absolutely perfect when you use just 2% of that blend sand and in theory it will be the most pump-able concrete product ever produced.  But will you ever be able to accurately batch that small amount?  Batch plants attempting to jog-in just the right amount of material into the weigh hopper often miss the mark when the mark is too small for the given weigh unit (such as 20 lb increments).  Furthermore, attempting to use such small material amounts, especially for fine sand material, can cause the material to bridge over the gate stopping the flow of material to the blend.   If you open the gates some more or jog them, all at once you got the sand you wanted and then some. When developing the blend, set the minimum constraint to a percentage that will provide sufficient material that can be accurately weighed and batched resulting in a smooth running plant.
Shorter Batch Times
So you opted to keep that small percentage of material in the mix after all.  Your batch plants computer can handle it right?  You got the jog times so small that you know that it will batch accurately.  The problem is, now that batch takes a lot more time to complete.  Increasing batch times by only a matter of minutes can have a trickle-down effect making each load even later then the last.  Creating blends that are more constrained to have a reasonable amount of each material not only speeds up the process but makes for happy customers when their deliveries are on time.
Maintain Specific Material Properties
Sometimes it’s not just the material gradation that matters.  You may be looking to maintain a specific combined specific gravity or total fractured faces in the product.  Creating percentage restrains on key materials can help maintain those other blended material properties where you want them.
Limit Reliance on a Single Product
It is really convenient when you have an aggregate product that works well in a blend.  But what if that product has an overweight contribution to the blend with a high variability?  Well, the high variability of that single product will increase the variability of the blend resulting in a higher probability of failures.  StonemontQC includes the Mix Risk tool to help evaluate the blend and identify this situation.  One solution may be to set a maximum percentage constraint on this product and possibly add an additional product to the blend with a minimum percentage constraint.
Minimize the Use of Expensive Products
Sometimes the best product is also the most expensive.  Savings can be realized if you can minimize the use of these really expensive products by constraining the maximum percentage used and still create a great material blend.  The minimum and maximum percentage constraints also can be used in conjunction with other tools such as minimizing the cost of the blend while meeting the desired specifications.
Good luck on you aggregate blends and put those material percentage constraints to good use.

For more information please contact Stonemont Solutions, Inc.

Michael Rodriguez
Stonemont Solutions, Inc.