The future of mix design is balanced
What is a Balanced Mix Design?
The FHWA defined balance mix design (BMD) as an “asphalt mix design using performance tests on appropriately conditioned specimens that address multiple modes of distress taking into consideration mix aging, traffic, climate and location within the pavement structure”. Essentially, balanced mix design involves designing a mix that is specific to the intended application, through the incorporation of multiple mechanical tests, which examine a particular form of distress.
why is it needed?
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Concerns with durability and cracking issues of asphalt pavements along with the growing awareness of the shortcomings of volumetric mix design systems have driven many SHAs and the asphalt pavement industry to explore the use of BMD as a new approach to asphalt mix design and production acceptance
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Establishing the state of performance of commonly used mixes (i.e., cataloging mixes) and optimizing those mixes to achieve performance will allow companies to help move asphalt related specifications forward to better ensure the needed field performance can be obtained.
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Balanced Mix Design allows for the optimization of mixes in terms of cost-effective material use (e.g., asphalt binder, aggregate, recycled material, additive, etc.) and performance. Without knowing the true performance of mixes, decisions on material use will likely be made based on assumptions, past experience (which may not hold true currently), raw cost alone or current specification limits and constraints. A total picture concept of materials plus performance provides the most benefit in terms of managing risk and increasing margin opportunity.
what we do…
At Trimat, we will perform the required volumetric mix design method (i.e., Superpave or Marshall) for determining an optimum binder content (OBC) that meets all the existing volumetric requirements. The mix design at OBC is then tested with the BMD mixture rutting and cracking tests. If the mix design fails the rutting and/or cracking test criteria, the entire mix design is repeated using different materials (e.g., aggregates, asphalt binders, recycled materials, and additives) or mix proportions until all the volumetric, rutting, and cracking criteria are satisfied. After passing the rutting and cracking tests, the mix design is then evaluated with the selected moisture damage test. If the design passes the moisture test criterion, the job mix formula is established for production.