Page 71 - Highway Engineering Handbook Building and Rehabilitating the Infrastructure

54 CHAPTER ONE

waste. The federal government as well as some states now have recycling mandates in
place. Permits are often required when conducting recycling activities, and/or when creat-
ing an authorized disposal site in using certain wastes as embankment fill. If the recycling
activity falls under the RCRA classification of “use constituting disposal,” additional reg-
ulations apply.
Economic Cost and Benefit. Economic considerations are often the driving force behind
recycling efforts on the county and city level, because of the increased landfilI costs and
increasingly limited capacity. Recycling for highway departments may become more
attractive as budget cuts increase and the price for recycled waste materials decreases. In
some cases, recycled materials extend the service life of highway components, making the
life-cycle costs of using such materials attractive.
Engineering Properties and Technical Performance. Because of the variability of the
composition of waste materials, performance results for end products may vary signifi-
cantly, requiring careful evaluation before identifying suitable applications for their use.
The primary question is “does the performance of the material compare favorably with
the same material constituted from raw materials?” In some instances, the use of waste
material has consistently improved performance. For instance, silica fume use in portland
cement results in higher compressive strength and higher resistance to corrosion of steel
reinforcement due to the increased density and reduced porosity of the resulting concrete.
(“Silicon,” Minerals Yearbook, U.S. Bureau of Mines, Washington, D.C., 1989.)

Construction Materials Shortages and Alternative Resource Availability. Millions of
tons of aggregate are used each year in the construction of highways. Resources from exist-
ing quarry mining are being depleted and the new sources are often not used because of
restrictive regulation and preferred uses of the land. In areas experiencing shortages, recy-
cling construction materials, waste minerals, and other products into aggregate is more
cost-effective than shipping aggregate from distant quarries. Steel is one of the most widely
recycled materials used in highways. Steel reinforcement can be composed completely of
recycled scrap steel, and steel girders can contain as much as 25 percent recycled scrap
steel. Recycling scrap steel greatly reduces reliance on foreign sources for raw materials in
the steel industry. (NCHRP Synthesis 199, p. 6.)

1.6.1 Legislation Affecting Use of Recycled Material
The Resource Conservation and Recovery Act (RCRA). RCRA classified solid waste
management facilities and practices, required states to develop comprehensive state plans
for solid waste management (Dufour, op. cit., p. 99). RCRA also emphasized the growing
landfill capacity problem and the need to develop approaches to handling wastes. In the
preamble of RCRA, attention was called to the vast quantity of recoverable materials that
are placed in landfills and to the fact that the recovery or conservation of many of these
materials would benefit the United States by reducing projected landfill capacity require-
ments, retaining and expanding our national resources, and reducing the country’s depen-
dence on foreign resources.
In reference to recycled materials, Section 6002 of RCRA requires that federal, state,
and local agencies receiving funds from the federal government must procure supplies
and other items composed of the highest practical percentage of recovered or recycled
materials, consistent with maintaining satisfactory levels of

• Product quality
• Technical performance