CORRECTING TENDERNESS OF A SHALE BY CHEMICAL TREATMENT ¹

ABSTRACT An attempt was made to increase the strength of a tender shale in both the green and dry states. Finer grinding, aging, and the addition of chemicals were the expedients used. Sulphuric acid increased the dry modulus of the shale up to 251% when used in concentrations up to 10%. This benefit was offset by a leaching of the color; 0.25% HCl and 0.25% tannic acid increased the dry modulus 42% and 72%, respectively. Organic binders as Bindex and glutrin showed a 100% increase. Two per cent Na ₂ CO ₃ and 1% BaCO ₂ showed a 60% and 45% increase. Molasses plus yeast improved the machining and the green strength of the shale. Finer grinding of the shale to pass 28‐ mesh and aging for one week improved the dry modulus 75.7%.