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Recycling Aggregate.

Despite double-digit drops in aggregate production, recycled material has shown year-over-year growth. Last month's look at the Transportation Research Board's conference (New Markets for old Products) showed some of the new uses being tried for recycled concrete and asphalt. Here's look at some other developments on that market front.

RESURFACING IN ENGLAND

Resurfacing work on a major United Kingdom highway, the M25, has set an industry standard for recycled roads in the U.K., by having the highest-ever use of Recycled Asphalt Pavement material on the national network.

The project was a collaboration between business consultant Mouchel and Tarmac. It used more than 700 tons of existing porous surface course recycled material on the new road surface using 40% RAP material - a first on a motorway or major A road maintained by the Highways Agency. This is part of the Highway Agency's ongoing program of investment in maintaining more than 4,000 miles of motorway and major roads (with A designations) in England.

This project follows one completed in 2007 in which up to 25% of the aggregate from the existing surface was recycled back into the new surface course covering an area of 30,000 square meters.

Tarmac had to undertake extensive laboratory testing to ensure that the new surface could meet standards for Polished Stone Values, texture, depth, skid resistance, deformation resistance and durability. The approved departure from standard required for the 20-mm sized thin surface course was another first for the M25.

For three consecutive nights, Tarmac planed and removed the existing surface from around 17,000 square meters.

The material was then transported for reprocessing at the company's Hayes asphalt plant, which has been specially upgraded to deliver high-percentage RAP material. The new surface course was re-laid on the following night as a new 20-mm aggregate surface covering 6,900 square meters.

RAP material typically is recycled in base and binder course materials and it is uncommon to reuse this material in a thin surface course, which requires high PSVs to ensure good skid resistance.

"Recycled roads offer a vital opportunity both to conserve virgin aggregates and help to reuse road planings, says Tim Smith, Tarmac's technical manager for London and South East. "This work sets a high benchmark for future road schemes on the national network and, as an industry, we have an obligation to continue to develop innovative technology which can deliver a sustainable approach to road renewal."

"We have to be adaptable as well as innovative in our approach to maintaining the U.K.'s road network for the Highways Agency," says Steve Smith, Mouchel's project manager. "By reusing materials we achieve several objectives. We lessen the impact on the environment by reducing waste and carbon emissions while at the same time reducing costs. It is a real achievement that Tarmac and Mouchel have been able to work together delivering a concept we hope will set the industry standard for the future. Tarmac has made some serious commitments to this whole project."

SCIENCE OF RECYCLING

Magdy Abdelrahman, assistant professor of civil engineering at North Dakota State University, has been named a recipient of the Faculty Early Career Development award by the National Science Foundation. Abdelrahman will receive a five-year, $400,000 award from the foundation to conduct research on understanding the interaction of recycled materials with asphalt.

Abdelrahman's research will focus on using recycled materials, like tire rubber, to enhance the performance of pavement as an aspect of the civil infrastructure sustainability. The broad goal of the research is to fundamentally characterize the materials and process variables responsible for property development in asphalt-rubber interaction. "Asphalt applications have the potential to contribute to the solution of the growing solid waste problem, provided that engineering and environmental concerns are addressed," said Abdelrahman.

Recycled tires, also known as Crumb-Rubber Modifier, and RAP, for example, can be engineered and used successfully in asphalt pavement. Asphalt binders represent an area that can improve pavement performance, according to Abdelrahman. The proposed research will synthesize asphalt-CRM binders through interactions, will characterize the physical and chemical properties of asphalt-CRM binders, and will model the impact of chemical releases from recycled asphalt materials containing additives and polymers on soil and groundwater.

"This project will have a broad impact because solid waste is problematic throughout the world," said Abdelrahman. The plan includes development of a graduate/senior course on recycled material applications and faculty-professional focus meetings to exchange experiences in the area of recycled materials. Activities will be used to recruit, train and mentor students while preparing them for careers in recycled materials. Community outreach activities will raise awareness to K-12 students to the environmental issues facing the global community regarding solid waste management.

DEMOLITION INDUSTRY TO REBOUND

There is still a moderate level of optimism for the demolition industry this year. That finding comes from a recent survey of National Demolition Association members.

Nearly one-third of members said they expected sales to increase this year, while more than 25% thought sales would remain the same as the previous year. Only 19% expected a decrease in sales.

"Our industry is populated in large part by entrepreneurs," said Michael Taylor, NDA's executive director. "While they are well acquainted with business realities, they also tend to be optimistic and look for opportunities even when the economy is so challenging."

Regarding employment plans for 2010, nearly 30% expected to increase staff, while another 30% said that staff levels would remain about the same. Only 15% expected to lay off staff.

ACCORDING TO U.S. GEOLOGICAL SURVEY DATA ...

During 2009, roads in 48 states and Puerto Rico used recycled asphalt for road paving; 47 states used recycled concrete. The amount of concrete and asphalt recycled in 2009 increased 45% compared with 2008; in 2008 it increased 31% compared with 2007.
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Publication:Rock Products
Date:May 1, 2010
Words:963
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