Proper graduation is vital to achieve a long life cycle. The agency must pay close attention to pre-existing problems in the subbase. RAP mixed with unsuitable material might provide short-term results, but the problems will reappear and have to be addressed later only if the subbase contains suitable materials will the RAP mixture provide an adequate road base. Local road managers must ensure adequate compaction and optimum moisture content. Soil additives can improve compaction because they attract moisture that will help attain optimum moisture content.
Additives allow contractors to meet compaction requirements with less job site effort and cost.
Conclusion RAP is viable replacement for virgin aggregate. With depleting natural resources municipalities should consider RAP as an alternative product. Aggregates in older pavements contain some of the best materials available today. Future municipal budgets may dictate that highway departments look to lower-cost alternatives such as RAP for overlays, shoulder material road base, and surface gravel for unpaved roads. I would be pleased to provide you with more detailed information as would the UNH T 2 Center.