Winstone Aggregates has developed a modified aggregate product as an economical alternative to standard basecourse.

Developed at Winstone Aggregates' Flat Top plant in Auckland, the product has aptly been named Flat Top Hydrated Cement Treated Basecourse (HCTB). Extensive laboratory testing, using repeated load triaxial equipment, found that the addition of a low dosage of cement to basecourse significantly improved moisture sensitivity and stiffness, as well as giving greater resistance to deformation when wet.

Winstone Aggregates produces Flat Top HCTB in a high intensity mixing plant, blending cement and water with natural crushed basecourse (GAP40). The use of a computerised control system enables a uniform dispersion of cement and moisture and ensures a consistent product.

The product is subject to strict quality control standards and stockpile hydration levels are tested reularly, targeting optimum moisture content. Dr Greg Arnold of Pavespec has evaluated Flat Top HCTB and says the modified aggregate performs well even when wet and at low compaction.

"The use of this material will reduce the risk of early pavement failure and therefore is suitable for high trafficked state highways," he says.