Potential Energy Savings From the Use of Recycled Glass in Brick Manufacturing

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A research project, sponsored by the California Department of Conservation and managed by the Center for Environmental Economic Development (www.ceedweb.org), was undertaken to determine whether energy savings were possible from substituting 12 mesh recycled soda lime container glass for ceramic grog in brick manufacturing. 12 mesh is the grade of recycled glass currently being processed for use by fiberglass manufacturers. The Chief investigator for the project was Robert Kirby of Seattle, Washington (kirbgood@earthlink.net).

ASTM C-1272-05a, "Standard Specification for Heavy Vehicular Paving Brick" was chosen as the applicable standard. Bricks containing 50 percent glass were fired until a kiln profile was found that produced bricks with average cold water absorption less than 6 percent. 50 percent glass bricks meeting the absorption standard were made with the following kiln profile:

Then the minimum weight glass/clay brick was found that, when fired to the schedule above, also met strength standards for heavy vehicular paving bricks. The minimum weight brick meeting the strength standard consisted of

As a control, bricks were made using the same dry clay, but with conventional ceramic grog. The minimum firing profile using conventional grog was:

The conventional bricks meeting the strength standards consisted of

Energy analyses of the kiln and firing profile gave the following results:

Energy to make glass/clay brick (per 4x8 brick):
Including kiln7717 BTUs per brick
Without kiln losses1456 BTUs per brick
Energy to make a grog/clay brick:
Including kiln11,085 BTUs per brick
Without kiln losses2382 BTUs per brick
The percentage of energy saved:
Including kiln30.4%
Without kiln losses38.9%

In addition to the firing energy savings, the fired glass/clay bricks weigh 11 percent less than the conventional bricks, resulting in transportation energy savings.

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Also, for additional information about this energy research projects, see: Recycled Glass in Ceramics Energy Research