The life of a road starts with its asphalt mix. Too much binder and the mix can rut under summer heat and truck loads; too little and it cracks and ravels early. That is why the mix is tested both before and after paving.
Designing the mix
Design starts with choosing the aggregate and checking its gradation by sieve analysis so that it falls within the specification limits. Specimens are then prepared at several binder contents, compacted and tested with the Marshall method to find the optimum binder content that delivers the required stability, flow and air voids.
Key laboratory tests
- Sieve analysis of fine and coarse aggregate: checks the particle size distribution.
- Marshall stability and flow: measures the resistance of the mix to deformation under load.
- Theoretical maximum specific gravity (Rice test): used to calculate air voids and the degree of compaction.
- Binder extraction: finds the actual binder content of the mix, after which the gradation of the recovered aggregate is checked.
Checks during and after paving
Samples are taken from the mix delivered to site to confirm it matches the approved design. After paving, cores are cut from the finished layer to measure its thickness and density, and the density is compared with the laboratory density to find the compaction achieved.
We design asphalt mixes to project specifications, the Saudi code or international codes, and follow their quality from the plant to the finished layer.