To ensure proper performance of a project, a mix design must be conducted to determine the compatibility of the aggregate, emulsified asphalt, water, mineral filler, and other additives. The mix design must be performed with the same material components to be used on the project in order to properly predict the performance of the micro surfacing mixture applied in the field. The mix design process results in a Job Mix Formula (JMF), which will specify the ratios of all materials to be used.
Mix designs must be completed according to ISSA A143/ASTM D6372 by a competent laboratory that is experienced with state of the art asphalt emulsion/aggregate mixing technology as it applies to slurry systems. The laboratory must possess the necessary specialized equipment and knowledgeable staff to perform the required tests. Knowing the specific system and the relationships of all the components is critical to the development of a good mix design. Each of the material components - aggregate, asphalt emulsion, water, and additives, must meet all job specifications and test requirements. Individual materials must be qualified through testing before the laboratory will perform further tests to determine the mix compatibility and performance under simulated wear conditions.
Although the contractor is responsible for providing the mix design, the owner’s representative should check the mix to verify that it meets the specification requirement. During mix design verification testing, an engineer conducts a series of tests on the basic materials. The materials must be available to the engineer so that this verification can be completed prior to the project starting. Mix design verification testing should be conducted at a laboratory designated by the engineer. Once the mix design is approved, all mixtures must follow the requirements stated in the resulting Job Mix Formula.
See the list of tests performed by the laboratory during the mix design process in the TESTING PROTOCOL section.
It is recommended to use a laboratory accredited by AASHTO re:source or equivalent.