Project Title: LIGHTWEIGHT COAL COMBUSTION RESIDUES-BASED STRUCTURAL
MATERIALS FOR USE IN MINES
ICCI Project Number: 95-1/3.1A-8
Principal Investigator: Yoginder P. Chugh, Southern Illinois University at Carbondale
Other Investigators: A. K. Ghosh, K. Mehta, S. K. Dube, Y. Xiao, Southern Illinois University at Carbondale, Illinois
The MEARL Corporation, New Jersey; U.S. Bureau of Mines, Spokane, Washington; Woodruff Supply, Madisonville, Kentucky; Eagle Seal, Benton, Illinois
Project Manager: Dan Banerjee, ICCI
ABSTRACT
The overall goal of this continuation project is to develop, design, test
and commercialize artificial supports (post and crib members) from coal
combustion by-products based lightweight structural materials for use in
mines. Currently, these supports are made of wood and about 60 x
106 cu. ft. of wood is utilized in the United States for this
purpose in underground coal mines. The developed artificial supports will
be manufactured and marketed by the industrial co-sponsors of the project.
The project goal was proposed to be achieved over a three year funding period
from September 1, 1994 to August 31, 1997. Over the last 24 months, the project
has achieved several major objectives including: 1) development of high volume
(65 to 70%) coal combustion by-products (CCB)-based lightweight 70 to 110
pcf structural materials with potential to fabricate elements which can be
used as posts and cribs in mines; 2) development of a steam and hot water
curing cycles at atmospheric pressure which can provide 28-day ASTM curing
cycle compressive strength for prototype samples in 3-days; 3) fabrication
and testing of small length-prototype (5in.x5in.x24in. or 6in.x6in.x24in.)
structural elements; 4) fabrication and curing of full size posts
(5in.x5in.x72in.) ready for testing at the U.S. Bureau of Mines facilities
in Pittsburgh; 5) demonstration of the performance of small length-prototype
elements in the laboratory to state and federal agencies; 6) design of a
commercial fabrication process for implementation and its economic analysis;
7) input from mining companies in the region regarding interest in the products
being fabricated, 8) development of an analytical model to evaluate performance
of artificial posts under mining conditions, 9) identification of two in-mine
testing location for the CCB-based supports, and 10) CCB-based supports can
effectively compete with similar wooden products even without considering
the environmental benefits of CCB's utilization and forest depletion. Efforts
are currently underway to fabricate forty (40) prototype posts and two hundred
(200) prototype crib elements for in-mine testing.
Pages 1 to 27 contain proprietary information
EXECUTIVE SUMMARY
The overall goal of this continuation project is to develop, design, test
and commercialize artificial supports (post and crib members, Figure 1) for
use in mines, which are manufactured from coal combustion by-products based
lightweight structural materials. Currently, these supports are made of wood
and about 60 x 106 cu. ft. of wood is utilized in the United States
for this purpose in coal mines. The developed artificial supports will be
manufactured and marketed by the industrial co-sponsors of the project.
The results to date on the ongoing project (September 1, 1994 - Aug 31, 1996)
can be summarized as follows.
1) CCB-based lightweight structural materials with suitable load-deformation characteristics have been developed to replace wooden post and crib elements. These materials typically contain 65% to 70% coal combustion by-products, have densities ranging from 80 to 90 pcf, and compressive strength of 3 in. x 6 in. cylinders ranging from 2,200 to 3,300 psi, with elastic modulus of 350,000 to 700,000 psi.
2) Laboratory tests on small-size (5 in. x 5 in. x 24 in.) 90 pcf elements loaded axially (as a post) in compression in a servo-controlled stiff testing machine indicate compressive strength ranging from 2,500 to 2,800 psi, elastic modulus ranging from 500,000 to 600,000 psi, and desirable post-failure characteristics (similar to wood). These characteristics suggest feasibility of commercial application for use as posts and cribs, to replace the wooden posts and cribs, as artificial supports in mines.
3) Laboratory tests on 20 in. high 2 x 2 cribs constructed from 5 in. x 5 in. x 24 in. CCB-based 90 pcf material indicate a load carrying capacity of about 110-115 tons as compared to only 70-75 tons for a similar wooden crib. Furthermore, CCB-based cribs are about four times more rigid and should also provide better roof control.
4) A laboratory demonstration of the performance of small size CCB-based elements on 4/16/96 to about 30 representatives from MSHA, coal industry, Office of Mines and Minerals, Cinergy (Gibson Power Plant), and Office of Coal Development and Marketing indicated significant commercial potential for use of CCB-based materials to replace wooden supports in mines.
5) Industrial cooperators have had very positive response from the mining companies regarding the use of these materials in mines.
6) Gibson Power Plant administration has expressed significant interest in locating the first commercial plant on their site. They have indicated a possible investment of several hundred thousand dollars towards a pilot plant and equipment if the manufacturing is done on their site.
7) Based on an analysis of the current market and the cost of wood, it is expected that successful development and marketing of lightweight posts and crib members alone will utilize about 0.25 x 106 tons of PCC and FGD by-products in Illinois Basin coal mines. Nationwide, this could amount to about 2.5 x 106 tons. This amount will double if utilization in non-coal mines is also considered.
8) A hot water curing cycle has been designed and tested which can provide 28-day strength obtained by using ASTM curing cycle in three days.
9) Facilities have been developed to demonstrate the commercial scale process using the industrial scale facilities at Eagle Seal Inc., Benton, IL and Woodruff Supply Inc., Benton, IL and Madisonville, KY. Two large-size mixes 2,000 lb. dry material each have been successfully prepared and used to make posts and crib members.
10) Experiments using 1.5 in. long commercially available polyester fibers instead of nylon fibers indicate them to be superior because of their non-wettable characteristics and higher elastic modulus.
11) Additional experiments using polyester fibers of two different lengths (0.75 in. and 1.5 in.) in equal proportion indicate two different lengths should be utilized in commercial production.
12) Two underground mines have been identified for field-demonstration and cooperative agreements have been developed. Roof control plans using CCB-based developed materials have been prepared and submitted to MSHA for approval.
13) Instrumentation for testing in-mine performance of wooden as well as CCB-based supports is currently being procured and/or fabricated.
14) A 200-ton compression testing machine with 3 ft x 3 ft base with 8 ft throat height was designed and it is currently being fabricated. The machine should be available for use by the end of September, 1996.
15) Facilities for a pilot plant location at the Gibson Power Station have been identified and communicated to the company.