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26 CHAPTER 8 Quality Control Quality control is required to ensure desired performance. and when traffic control can be removed. Moisture content can The following section describes procedures that should be be determined by complete moisture evaporation from the followed to improve the likelihood of good performance for chips using a forced draft oven or a microwave oven. By weigh- a chip-seal project. ing the chips before and after removing moisture, the moisture content (w) can be determined as follows: 8.1 Aggregate Sieve Analysis wet weight - dry weight Aggregate gradation should be checked whenever there is w, % = 100 wet weight potential for significant variation in the chip gradation. For example, if chips have been stockpiled near the project and there is sufficient quantity to supply the entire project, a com- 8.3 Embedment Depth Measurement plete gradation analysis before construction begins, and every During Construction 100 tons thereafter, should be adequate. Also, loader opera- Embedment depth is usually determined during construc- tions at the stockpile can produce excess material passing the tion by pulling several chips out of the binder and visually esti- no. 200 screen and should, therefore, be monitored. Aggregate mating the amount of embedment. This is difficult and often gradation should not deviate from the target design gradation subjective even if chips have a very low flakiness index. There- by more than the following tolerances: fore, a new method is recommended of spreading a volume of Tolerance, 50 cm3 of glass beads over the surface of the embedded chips Sieve , % and measuring the diameter. During the chip-seal design, the 3 /4 5 relationship between glass bead diameter and aggregate embed- 1 /2 5 ment is determined. During construction the glass beads are 3 /8 4 No. 4 3 spread on the pavement and the diameter measured. Embed- No. 8 1 ment is then determined using the relationship between glass No. 200 0.5 bead diameter and embedment from the design measurements. When chips are supplied from multiple locations, sam- pling and testing for gradation should be done with more 8.4 Field Viscosity frequency, including checking each truck if high variability The viscosity of the emulsion should be checked for each is suspected. Because a full sieve analysis may not be practical, transport load. This can be done in the absence of a field lab- hand sieving in the field using only the coarse aggregate screens oratory using a Wagner flow cup. Flow times of 20 to 70 s at can provide information on the suitability of the material or 85 to 150F for a 6-mm orifice or 10 to 60 s at 85 to 140F for help determine if more laboratory testing is needed. a 7.5-mm orifice have been found to provide satisfactory flow rates. If flow rates using a Wagner cup are not within these 8.2 Moisture Content of System limits, the temperature of the emulsion should be checked to The moisture content of the chips should be measured at the determine if emulsion temperature is the cause. If tempera- beginning and the end of the day for (1) calculating aggregate ture of the emulsion is not causing unacceptable flow rates, spread rate and (2) determining when sweeping can be done other causes should be investigated.