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. . . .. . 10-2 - Materials 10-2.1 - Dumped Riprap -- Stone used for dumped riprap "hall be hard, durable, angular in shape; resistant to weathering and to water action; free trOlll overburden, spoil, shale and organic material; and shall meet the gradation requirements for the class specitied. Neither breadth nor thickness ot a single stone should be less than one-third its length. Rounded stone or boulders will not be accepted unless authorized by special provisions. Broken concrete may be substituted for stone when authorized by special provisioDB. Shale and stone wi th shale seams are not acceptable. The minimum weight ot the stone shall be 155 pounds per cubic foot as com- puted by multiplying the specific gravity (bulk-saturated-surface-dry basis, AASIIO Teat T 85) times 62.3 pounds per cubic toot. The sources trom which the stone will be obtained shall be selected well in advance at the time when the stone will be required in the work. The acceptability ot the stone will be determined by service records and/or by sui table tests. It testing is required, sui table IllUIlples at stone shall be taken in the presence at the engineer at least 25 days in advance at the time when the placing of riprap is expected to begin. The approval of some rock fra8ments from a particular quarry site shall not be construed as con- sti tuting the approval at all rock fragments taken frClll that quarry. In the absence of service records, resistance to disintegration from the type at exposure to which the stone will be subjected will be deter- mined by any or all at the following tests as stated in the special provisions: (1) When the riprap must withstand abrasive action from material transported by the streu, the abrasion test in the Los Angeles machine shall also be uaed. When the abrasion test in the Los Angeles machine (AASHO Test T 96) is used, the stone shall have a percentage loss at not more tban 40 after 500 revolutions. (2) In locations not subject to tree zing or where the stone is exposed to salt water, the sulfate soundness test (AASHO Test T 104 for ledge rock using sodium sulphate) shall be used. Stones shall have a loss not exceeding 10 percent with the sulfate test after tive cycles. When the treezing and thawill8 test (AASHO Test 103 for ledge rock procedure A) is used as a guide to resistance to weathering, the stone should have a loss not exceeding 10 percent after 12 cycles 01' tree zing and thawing. (3) 11-37