Standard Test Procedures Manual

Transcription

1 STP Standard Test Procedures Manual Section: EXTRACTION AND MOISTURE CORRECTION 1. SCOPE 1.1. Description of Test This method describes the procedure for determining the Extraction and Moisture Corrections used for adjusting the percentage asphalt determined in STP 204-2, Asphalt Content by Centrifuge Extraction Application of Test This test method must be used with the extraction procedures described in STP The extraction correction is required because of the loss of fines through the filter and for asphalt absorbed into the aggregate. The moisture correction is required because the moisture in the mix is extracted as bituminous binder. The intent is for the lab sample to match the field pavement core properties Units of Measure The Extraction Correction and are expressed as percentage asphalt contents. 2. APPARATUS AND MATERIALS 2.1. Equipment Required Extraction Correction The equipment and materials required is the same as the equipment required in the extraction procedure that you used to determine the asphalt content of the mix The equipment and materials required is described in the test procedure STP 204-1, Moisture Test by Oven Drying. Date: Page 1 of 6

2 3. PROCEDURE Extraction Correction A. VIRGIN MIXES (Permanent Labs only) Type 1V Extraction Correction for Testing Virgin Aggregate Aged Mixes This is the extractor correction to be used when testing the AC content of cores, check tests or other samples that have been mixed a minimum of 1 or 2 days prior to testing. Prepare mix with a known percentage of bituminous binder using aggregate and asphalt binder from the jobsite. For conventional hot mix plants use the aggregate from the coarse and fine hot bins of the plant and recombine to the stockpile average using the 5.00 mm sieve as the control. Carefully extract the mix (as soon as the sample has been prepared) using the appropriate test procedure, either STP 204-2, Asphalt Content by Centrifuge Extraction and use the difference between "percent asphalt extracted" and actual "percent asphalt added" as a correction on subsequent mixes tested. Ensure that the number of washings used in the extraction correction is the same as the number of washings used for the actual plant mix. An example is shown below: % asphalt extracted 5.60% 5.35% Extractor Correction (-)0.15% (+)0.10% The correction should be an average of three trial mixes and should be determined for each lab man and new pit on the jobsite. subtracted to any of the following tests in the manner shown: Extractor Correction 0.15% 0.10% Corrected % asphalt extracted 5.15% 5.20% Page: 2 of 6 Date:

3 The procedure for is described in the Standard Test Procedure STP 204-1, Moisture Test by Oven Drying. Type 2V Extraction Correction for Testing Virgin Aggregate Fresh Mixes This is the extractor correction to be used when testing "fresh mixes" (i.e. extractions performed immediately after mixing, generally quality control test at the plant site). Prepare mix with a known percentage of bituminous binder using aggregate and asphalt binder from the jobsite. For conventional hot mix plants use the aggregate from the coarse and fine hot bins of the plant and recombine to the stockpile average using the 5.00 mm sieve as the control. Let the mixed sample sit at room temperature for hours. After sitting for hours, place the sample in an oven preheated to 120 o C. Remove the sample from the oven after 4 hours + 15 minutes. Carefully extract the mix (as soon as the sample has been conditioned) using the appropriate test procedure, either STP 204-2, Asphalt Content by Centrifuge Extraction and use the difference between "percent asphalt extracted" and actual "percent asphalt added" as a correction on subsequent mixes tested. Ensure that the number of washings used in the extraction correction is the same as the number of washings used for the actual plant mix. An example is shown below: % asphalt extracted 5.60% 5.35% Extractor Correction (-)0.15% (+)0.10% The correction should be an average of three trial mixes and should be determined for each lab man and new pit on the jobsite. subtracted to any of the following tests in the manner shown: Extractor Correction 0.15% 0.10% Corrected % asphalt extracted 5.15% 5.20% Date: Page: 3 of 6

4 The procedure for is described in the Standard Test Procedure STP 204-1, Moisture Test by Oven Drying. B. RECYCLE MIXES Type 1R Extraction Correction for Testing Recycled "Aged Mixes" (Permanent Labs only) This is the extractor correction to be used when testing the AC content of cores, check tests, or other samples that have been mixed a minimum of 1 or 2 days prior to testing. Prepare a virgin mix (no reclaim) with a known percentage of bituminous binder using aggregate and asphalt binder from the jobsite. The gradation of this virgin mix is to be the same as the gradation of the actual recycled mix (mix design or job mix formula). For conventional hot mix plants use the aggregate from the coarse and fine hot bins of the plant and recombine to the stockpile average using the 5.00 mm sieve as the control. Carefully extract the mix (as soon as the sample has been prepared) using the appropriate test procedure, either STP 204-2, Asphalt Content by Centrifuge Extraction and use the difference between "percent asphalt extracted" and actual "percent asphalt added" as a correction on subsequent mixes tested. Ensure that the number of washings used in the extraction correction is the same as the number of washings used for the actual plant mix. There are two possible cases in determining an extractor correction: CASE 1 more asphalt extracted than added due to lost fines, CASE 2 less asphalt extracted than added due to absorption The two cases are shown below: % asphalt extracted 5.60% 5.60% Extraction Correction (-)0.15% (+)0.10% The correction should be an average of three trial mixes and should be determined for each lab man and new pit on the jobsite. subtracted to any following tests in the manner shown: Page: 4 of 6 Date:

5 Extractor Correction 0.15% 0.10% Corrected % asphalt extracted 5.15% 5.20% The procedure for is described in the Standard Test Procedure STP 204-1, Moisture Test by Oven Drying. Type 2R Extraction Correction for Testing Recycled "Fresh Mixes" This is the extractor correction to be used when testing "fresh mixes" (ie. extractions performed immediately after mixing, generally quality control tests at the plant site). Prepare a virgin mix (no reclaim) with a known percentage of bituminous binder using aggregate and asphalt binder from the jobsite. The gradation of this virgin mix is to be the same as the gradation of the actual recycled mix (mix design or job mix formula). For conventional hot mix plants use the aggregate from the coarse and fine hot bins of the plant and recombine to the stockpile average using the 5.00 mm sieve as the control. Let the mixed sample sit at room temperature for hours. After sitting for hours, place the sample in the oven preheated to 120 C. Remove the sample from the oven after 4 hours + 15 minutes. Carefully extract the mix using test procedure STP 204-2, Asphalt Content by Centrifuge Extraction. There are two possible cases in determining an extractor correction: CASE 1 more asphalt extracted than added due to lost fines, CASE 2 less asphalt extracted than added due to absorption. The two cases are shown below: % asphalt extracted 5.70% 5.35% Extraction Correction (-)0.25% (+)0.10% Correction for extractor error is "Type 1R" + (("difference"-"type 1R")*"the virgin aggregate ratio") Date: Page: 5 of 6

6 Given: Type 1R extraction correction = (-).15(CASE 1) or (+)0.10(CASE 2) Difference = (-).25(CASE 1) or (+)0.10 Virgin agg. ratio =.60 Correction for extraction error CASE 1 = (-).15 + (((-.25)-(-.15))*.60) = (-).21 CASE 2 = (+) (((+0.10)-(-0.10))*0.60) = (+)0.10 The correction should be an average of three trial mixes and should be determined for each lab man and new pit on the jobsite. subtracted to any following tests in the manner shown: Extractor Correction 0.21% 0.10% Corrected % asphalt extracted 5.09% 5.20% The procedure for is described in the Standard Test Procedure STP 204-1, Moisture Test by Oven Drying. 4. RESULTS AND CALCULATIONS The collection of test results and calculations are done on the appropriate form as described in the standard test procedures STP 204-2, Asphalt Content by Centrifuge Extraction. 5. CALIBRATIONS, CORRECTIONS, REPEATABILITY Calibrations, corrections, and repeatabilities are stated in the appropriate test procedures STP or STP Page: 6 of 6 Date: