SECTION 910: AGGREGATE INDEX
910.1 Description
The Aggregate Index (AI) combines test values from the Los Ang eles Wear Test, Soundness Loss Test, and Absorption Test. The AI is a single v alue representing the overall quality of the source from which the aggregates are obtained. The Contractor shall not use an individual aggregate stockpile for AI determination.
910.2 Sampling and Testing Procedures
The Contractor shall: 1. Determine Los Angeles wear, soundness loss, and absorption v alues for the AI equation using at least five (5) random test samples obtained f rom all stockpiles at the source in accordance with AASHTO T 2. 2. Submit all of the five (5) samples to a Department approved Private Testing Laboratory for combination into a single sample. The Project M anager or the State Materials Bureau will have a list of approved Private Testing L aboratories. 3. Extract a representative test sample from the single sample to determine the Los Angeles wear and absorption values. 4. Prepare the sample used to determine the absorption as follo ws: a. Plus 3/4 inch 1000 grams b. 3/4 inch to 1/2 inch 1000 grams c. 1/2 inch to 3/8 inch 1000 grams d. 3/8 inch to #4 1000 grams 5. Separate the remaining amount of the single sample into five (5) test samples using the procedures in AASHTO T 248. 6. Calculate a soundness loss value for each of these five (5) samples using Table 910.2:1, “Standard Gradation for Soundness Loss Testing.” Table 910.2:1 Standard Gradation for Soundness Loss Testing Sieve size % passing 1 1/4 inch 100 1 inch 100 3/4 inch 79 1/2 inch 53 3/8 inch 34 No. 4 0 7. Average the five (5) soundness loss results to obtain the ov erall soundness loss value for the subject aggregate pit.
910.2.3 Testing of Aggregates
The Contractor shall perform the following tests using a Depar tment approved Private Testing Laboratory: 1. Los Angeles Wear (in accordance with AASHTO T 96, Method B); 2. Soundness loss (in accordance with AASHTO T 104); and Section 910: Aggregate Index Page 966 3. Absorption (in accordance with AASHTO T 85). The Contractor shall: 1. Use the same Private Testing Laboratory for the entire Proje ct unless otherwise approved (in writing) by the Project Manager. 2. Obtain samples under the observation of the Project Manager or Department designee. 3. Send copies of test repor ts to the Project Manager.
910.2.4 Frequency of Testing
The Contractor shall submit samples at least once every year t o maintain continuous approval of Commercial Material Sources. 910.2.5 Equation The Contractor shall calculate the AI of a coarse aggregate to the nearest whole number in accordance with the following equation:
A.SL LA AI 0.4 0.3 2.2 31 ( 1 ) Where, AI is the aggregate index LA is the Los Angeles Wear, the percent of aggregate wear at 500 revolutions if tested in accordance with AASHTO T 96 SL is the soundness loss of the sample if tested in accordance wi th AASHTO T 104 using magnesium sulfate with a test duration of five (5) cycles and the standard gradation in table 910.2:1 A is the absorption, the amount of moisture retained if tested i n accordance with AASHTO T 85 Example: 1. Determine the L.A. Wear as a whole number – for example, 25; 2. Determine the Soundness Loss as a whole number – for example , 15; 3. Determine the Absorption as a whole number – for example, 3; 4. Calculate the value of the L.A. Wear taken to the 2.2 power – t h a t i s , 2 5^ ( 2 . 2) = 1189.8; 5. Calculate the value of the Soundness Loss taken to the 3rd p ower – that is, 15^(3) = 3375; 6. Calculate the value of the Absorption taken to the 4th power – that is, 3^(4) = 81.0; 7. Add the value obtained from steps 4, 5, and 6 – that is, 11. 89.8 + 3375 + 81.0 = 4645.8; 8. Determine the square root of Step 7 – that is, √(4658.8) = 6 8.2; 9. Divide the result from Step 8 by 3 – that is, 68.2 ÷ 3 = 22. 7; The A.I. for this sample is 22.7.
Source: New Mexico Standard Specifications for Highway and Bridge Construction, 2019 Edition. Pages 0–0 of 974.