FHWA probes SCM, natural pozzolans within best pavement practices

Sources: Federal Highway Administration; CP staff

A new FHWA Tech Brief cites benefits and drawbacks of fly ash, slag cement, silica fume and natural or alternative pozzolans for highway-grade concrete. “Supplementary Cementitious Materials — Best Practices for Concrete Pavements” (FHWA-HIF-16-001) outlines how transportation agencies approach increasing service demands on concrete structures, along with expectations for reduced environmental impact plus lower initial and lifecycle costs.

The Tech Brief discusses hydraulic and pozzolanic activity; the chemistry, specifications and performance characteristics of fly ash, slag cement and silica fume; plus, ternary mixtures, where two or more SCM or binder materials join ordinary portland cement in concrete mix designs. It also examines how availability issues of the main SCM are opening the door to a) natural pozzolans, including some diatomaceous earths, opaline cherts and shales, tuffs and volcanic ashes, pumicite, and various calcined clays and shales; and b) alternative SCM, defined as inorganic materials that react, pozzolanically or hydraulically, and beneficially contribute to concrete strength, durability and workability, but do not meet ASTM or AASHTO specifications for conventional SCM.

Supplementary Cementitious Materials — Best Practices for Concrete Pavements” was published with oversight of FHWA Concrete Pavement Engineer Sam Tyson, P.E., and authored by Michigan Technological University Professor Lawrence Sutter. A pdf of the seven-page Brief can be obtained here.