Lightweight combustion residues-based structural materials for use in mines. Quarterly report, 1 March 1995--31 May 1995

Abstract

The overall goal of this PrOject is to develop, design, and test artificial supports (post and crib members), for use in mines, which will be manufactured from coal combustion by-products (CCB) based lightweight structural materials. During the last quarter (Dec. 1, 1994--Feb. 28, 1995), it was reported that low LOI ({approx}5%) F-fly ash-based lightweight materials with density ranging from 70-1 110 pcf and compressive strength ranging from about 1,500 psi to 5,000 psi had been developed. During this quarter, 1) similar materials were developed using higher LOI ({approx}1O%) F-fly ash, 2) performance of materials using nylon fibers rather than polypropylene fibers was examined, 3) effect of addition of small amounts of FBC spent bed material on strength-deformation properties was evaluated, 4) flexural strength tests were performed on 2 in. X 2 in. X 12 in. cast beams, 5) compressive strength tests were performed on cast hollow cylinders (6 in. outer diameter, 2.762 in. inner diameter and 12 in. long) and 6) limited number of tests were conducted to determine the effect of mixing speed on strength of developed materials. The results of these studies indicate that 1) suitable lightweight materials using 60--65% higher LOI F-fly ash can be developed for fabrication of artificial supports, 2) nylon fibers perform significantly better than Polypropylene fibers, 3) loss of strength and deformability due to the use of higher LOI fly ash can be offset to some extent by adding 5--10% FBC spent bed material, 4) relationship between flexural strength and compressive strength, similar to that in concrete exists, 5) strength-deformation properties of hollow cylinders are similar to 3 in. X 6 in. solid cylinders, and 6) strength and deformation modulus increase with mixing speed. Two mixes for final development of lightweight materials have been identified and final test` will begin June 1, 1995.