Road Layer Works

Requirements for approved target grading:

SANS 1200-M and Colto requirements state that the aggregate for bases and sub-bases should be derived from hard, sound and durable rock.

Approved target gradings are determined by laying a trial section using material complying with grading limits given in the table below. Prior to compaction, six samples of the material in situ are taken and subjected to grading analysis. The resultant (smoothed) grading curve is then classified as the approved target grading for that project and all future grading results
are evaluated against this target.

Note: Approved target gradings are not used by AfriSam to produce product.

Soluble salt requirements:

Colto requirements recommend the following on site:

For quartzite, tillite, shale and G1 to G4 materials, measure the soluble salts against pH or electrical conductivity.

• Use the material if the pH is >10 after treatment at the crushing plant, and subsequently remains = 8,0.
• If the pH is <6,0 treat with lime until the pH = 10,0 before use.

For natural gravel and other crushed aggregate, use the material if the electrical conductivity (EC) is 0,15 Smˉ1, but pay particular attention to design and construction if the pH = 6,0.

• If the pH = 6,0, the EC is 0,02 Smˉ1 and sulphates are not a problem, use the material. If not, analyse the material in accordance with the customer’s instructions and submit a proposal for approval.
• Where the salinity of water added for compaction causes the salinity of the material to increase, determine soluble salinity within 24 hours of compaction before prime coat is applied.