Specifications include, but are not limited to: 1) Composition: Shell materials to be used for shell base or shell stabilized base, shall consist of naturally occurring deposits formed essentially of broken mollusk shell, corals and the skeletal remains of other marine invertebrates. Live or steamed shell or man-made deposits as a by-product of the shellfish industry will not be permitted. 2) Deleterious Substances: Shell materials shall be reasonably free of lumps of clay, organic matter, and other substances not defined which may possess undesirable characteristics. The material shall not contain silica sand in sufficient quantity to prevent bonding. 3) Physical and Chemical Properties: Shell materials shall meet the following physical and chemical requirements: Limerock Bearing Ratio (FM 5-515) - The material shall have an average LBR value of not less than 100. Material represented by any individual LBR value of less than 90 is unacceptable. Plasticity (FM 1-T 089 and FM 1-T 090) - That portion of the material passing the No. 40 [425 μm] sieve shall be non-plastic. Carbonates (FM 5-514) - The minimum percentage of carbonates of calcium and magnesium shall be 50. B. SHELL/ROCK MATERIAL: 1) Definition: Shell rock materials to be used for shell rock base shall be defined as naturally occurring heterogeneous deposits of limestone with interbedded layers or lenses of loose and cemented shell, to include cemented sands (calcitic sandstone). This material shall be mined and processed in a manner that will result in a reasonably homogenous finished product. Approval of mineral aggregate sources shall be in accordance with 6-3.3. 2) Deleterious Substances: Shell rock materials shall not contain lumps of clay, organic matter, cherty or other extremely hard materials, or other substances not defined, in sufficient quantity as to be detrimental to the finishing, strength, or performance of the base. The material shall not contain loose, free silica sand in sufficient quantity to prevent bonding of the base, or to result in a surface which is susceptible to distortion under construction traffic, or accumulation of loose sand on the finished surface which precludes bonding of the bituminous tack coat with the base, nor shall the material contain more than 50% loose, free shells, corals or skeletal remain of other marine invertebrates (retained on the No. 4 sieve). Materials shall contain no water sensitive clay minerals.