Aggregate Base and Sub-base products are typically used in conjunction with concrete or asphalt pavements, but can also be used in any application requiring a solid foundation. Bases and sub-bases are a mix of particle sizes, usually ranging from less than 2 inches down to less than 75 microns (#200 mesh). The material finer than 75 microns acts as a binder for the product, instead of cement or asphaltic cement that would be used in concrete or asphalt.
Although some variation in aggregate properties is expected, a few of the characteristics that should be considered when selecting aggregate bases and sub-bases include:
- size and grading
- toughness and hardness
Size and Grading
The maximum size of an aggregate designates the smallest sieve size through which 100 percent of the material will pass. Grading of an aggregate is determined by sieve analysis. Maximum size and grading are controlled by specifications that prescribe the distribution of particle sizes to be used for a particular aggregate material. The distribution of the particle sizes help determine the stability and density of the mixture.
Absorption and Moisture Sensitivity
The porosity of an aggregate is generally indicated by the amount of water it absorbs when soaked in water. A certain degree of porosity is desirable, as it permits aggregates to absorb binder, which then forms a mechanical linkage between the binder and the aggregate particle. For aggregate bases and sub-bases, where ease of compaction is a consideration, the sensitivity to moisture can play a role in achieving optimum moisture.
Aggregates are subjected to additional crushing and abrasive wear during manufacture, placing, and compaction. Aggregates are also subjected to abrasion under traffic loads. They must exhibit an ability to resist crushing, degradation, and disintegration. The Los Angeles Abrasion test measures wear abrasion resistance of aggregates, and plays a role in overall pavement section design.
All of our Aggregate Base and Sub-base products are monitored through our continuous quality control program, which includes daily, weekly, and annual testing. This testing is performed by our in-house testing facilities, independent laboratories, and finally by Governmental Agencies such as CalTrans. If you need any test data, please contact the location you are interested in.