Winter 2017-18

David R. Smith 2 interlockutor You Have to Think A s we enter the 24th year of this magazine, the industry returns to pre-recession sales levels. Residential sales dominate about three- quarters of shipments, with the remainder placed in commercial (specified) applications. Permeable interlocking concrete pavements, paving slabs and planks are the high-growth products. Permeable units have been regulated into existence, whereas slabs and planks present a sleek, modern aesthetic that visually and emotionally connects pedestrians to residential and commercial settings. While the economy charges forward and pulls construc- tion with it, we continually remind users that segmental concrete pavement products are elements or components within larger pavement systems. The systems con- sist of hundreds of possible combinations of elements: paving units, patterns, colors, bedding and base materials. Traffic and soils often drive the right combinations. Like any other pavement or build- ing system, finding the right combination of elements for an application is the key to ease of construction and minimal maintenance. ICPI provides a large stable of detail drawings and specifica- tions on www.icpi.org to help designers choose the best combination of elements. Twenty-three ICPI Tech Specs offer design, construction and maintenance advice on a range of assemblies. However, they don’t cover absolutely every design situation. There- fore, some thinking is required to find the assembly that fits the application while avoid- ing cut-and-paste solutions. More importantly, thought and study are required to understand the interaction of pavement materials under different loads and in vari- ous climates. In a fee-driven, hurry-up design and construc- tion world, clear thinking about segmental pavement can get overlooked. Some decision tools are needed to bring clarity to design thought processes. One segmental paving expert who provided an integrated decision tool for many ap- plications is Professor John Knapton on www.sept.org/ techpapers/1098.pdf . Entitled, “A Total Quality Approach to Pavement Specification,” the paper was written 17 years ago and provides a structure for decision-making regarding selecting the right pavement structure components. An- other summary of structural performance and system as- semblies are presented below as a guideline. We hope these clarify your thinking . STRUCTURAL PERFORMANCE LIMITS *ESALs = 18,000 lb equivalent single axle loads continued on page 3