Quarry Southern Africa November 2017 - Page 26

NEW TECHNOLOGIES IN ASPHALT PLANTS By Marcelo Zubaran As changing economic conditions and technologies combine to create new requirements for construction and road building, so, too, are the requirements for asphalt plants changing. N ew demands in the paving business, such as the production of sustainable asphalt mixes, more economical mixes, and mixes with greater durability, influence the chain of inputs, projects, and equipment. Asphalt plants are thus evolving significantly, having the goal of producing both traditional and more complex mixes that require special input (lime, cellulose fibres, and modified asphalt) with maximum productivity, efficiency, and economy. Three areas that bring benefits to the quality of the asphalt mix and/or optimisation to the production process are: (a) control over aggregates’ drying time; (b) fuel and energy economy through a new combustion system; and (c) control of the mixing time between the aggregates and the asphalt binder. Aggregates’ drying time For the production of hot asphalt mixes, the aggregates must be completely dry and heated to obtain adhesiveness with the An external pug mill mixer has been developed, which automatically controls the mixing time according to the requirements of the materials and as determined by the operator before or during production. 24 _ QUARRY SA | NOVEMBER 2017 asphalt binder and to produce a cohesive mix with suitable properties according to the design. It is known that aggregates are natural materials from rock formations whose characteristics derive from particular phenomena of each region. Thus, aggregates of the same origin may present quite distinct characteristics, such as the water absorption capacity and adhesiveness with the asphalt binder. Traditional plants dry and heat the aggregates in a rotating drum, driven by