Update on THHRC Research into the Phosphoric Acid Modification of Asphalt

Transcription

1 Update on THHRC Research into the Phosphoric Acid Modification of Asphalt The Office of Research, Development, and Technology (RD&T) Turner-Fairbank Highway Research Center (TFHRC) McLean, VA Jack Youtcheff FHWA Terry Arnold FHWA Susan Needham FHWA/Global Inc. NEAUPG and RMAUPG October 2007

2 Some Old News + Latest Results 1. Effect of Acid Grade 2. Stiffening Effect is Asphalt Dependent 3. Simple Qualitative Test 4. Effect of Moisture 5. Effect on Antistrip Additives

3 Effect of Acid Grade and Asphalt Source All acid grades give similar stiffness increase Grades containing water may give foaming problems Stiffness change is asphalt dependent

4 Stiffness of AAK-1 Modified with Phosphoric Acid 24 hrs 165oC G*/Sinδ kpa % 105% 85% 75% Phosphoric Acid % (Normalized to 100% Acid)

5 10 Stiffness of AAD-1 Modified with Phosphoric Acid - 24 hrs 165oC 8 G*/Sinδ kpa % 105% 85% 75% Phosphoric Acid (Normalized to 100% Acid)

6 8 Stiffness of AAM-1 Modified with Phosphoric Acid 24hrs 165oC 6 G*/Sinδ kpa % 105% 85% 75% Phosphoric Acid % (Normalized to 100% Acid)

7 Stiffness of ABM-1 Modified with Phosphoric Acid - 24 Hrs at 165oC 6 G*/Sinδ kpa % 105% 85% 75% Phosphoric Acid % (Normalized to 100% Acid)

8 Effect of 115% PPA Acid Modification on Original PG Grade Degrres Centigrade AAD-1 AAK-1 AAM-1 ABM-1 60% Bach 94% Bach Whiting Holly % Acid

9 Susan P. Needham Test No special equipment or expertise needed Requires a few inexpensive chemicals Test is rapid and simple A blue color is developed after 5 minutes Test can detect 0.1% PPA in asphalt Details available on TFHRC Website

10 Susan P. Needham Test Quantities are not critical Put 1 gram of hot asphalt into a 1oz can Add 1ml of n-butanol and swirl in the can Add 2mls water Add 1 ml of ascorbic acid/ammonium molybdate solution A blue color is developed within a few minutes.

11 Susan P. Needham Test

12 Moisture Sensitivity Does adding a hydrophilic material like phosphoric acid impart moisture sensitivity to the binder?

13 Environmental Effects -Water BBR Beams and DT samples of neat binder and 50% mastics were soaked in a 45 o F water bath Beams were dried with a paper towel and weighed Water absorption increases with increasing PPA particularly at levels greater than >1-1.5% Neat binders also showed some loss of stiffness and phase angle

14 % Water Absorption Water Absorption of Citgo Asphalt BBR Beams Modified with 115% Polyphosphoric Acid 0.50% 1.00% 1.50% 2.00% 3.00% 4.00% Days Water Immersion 45 degf

15 0.70 Water Immersion Citgo Asphalt + 50% Gravel Water Absorption % % PPA 0.5% PPA 1.0% PPA 1.0% PPA 1.5% PPA 1.5% PPA 2.0% PPA 2.0% PPA Days in Water

16 0.70 Water Immersion Citgo Asphalt + 50% Gravel Water Absorption % % PPA 0.5% PPA 1.0% PPA 1.0% PPA 1.5% PPA 1.5% PPA 2.0% PPA 2.0% PPA Days in Water

17 Water Immersion Citgo Asphalt + 50% Diabase Water Absorption % % PPA 0.5% PPA 1.0% PPA 1.0% PPA 1.5% PPA 1.5% PPA 2.0% PPA 2.0% PPA Days in Water

18 Water Immersion Citgo Asphalt + 50% Sand Water Absorption % % PPA 0.5% PPA 1.0% PPA 1.0% PPA 1.5% PPA 1.5% PPA 2.0% PPA 2.0% PPA Days In Water

19 Effect of 245 Days 44 degf Water Soaking Citgo Asphalt 45 G*/Sin Delta 70 Deg C KPa Original Soaked Polyphosphoric Acid %

20 Effect of 245 Days 44 degf Water Soaking Citgo Asphalt Phase Angle 70 Deg C Degrees Original Soaked Polyphosphoric acid %

21 Hamburg Testing Rationale There is no perfect test to measure stripping We chose Hamburg at 50 o C The tests are not meant to be exhaustive Criterion is Does PPA make it better or worse Tests are done in duplicate Both results are shown on the charts

22 Effect on Antistrip Additives Expectation has generally been that lime and amines cannot be used with PPA modification since the alkalinity of the antistrips would be neutralized by the acidity of the PPA and vice versa From this acid/alkaline viewpoint a non amine antistrip, like a phosphate ester, we would not expect to affected by PPA If only things were that simple.

23 Materials Used Asphalt from Citgo Stripping Sandstone Aggregate from MD (Banned by MDDOT) Limestone Aggregate from MD Granite from GA Amine Antistrip from Arr-Mazz- LA-2, LOF65-00 Non Amine from Innophos Innovalt-W (a phosphate ester) Lime from Chemical Lime Company

24 Phosphoric Acid Alone With all three aggregates the addition of PPA to the binder made the stripping worse One exception was with 3% PPA and sandstone aggregate. The addition of 3% PPA makes an asphalt far too stiff to be used. It is a stiffening effect we are seeing rather than an increase in moisture resistance 1% PPA addition did not stiffen the neat binder

25 35 Hamburg 50degC Citgo Asphalt Sandstone Aggregate Rut Depth mm % PPA 1% PPA 3%PPA 3% PPA Passes

26 Hamburg 50degC Citgo Asphalt Limestone Aggregate Rut Depth mm % PPA 1% PPA Passes

27 Hamburg 50degC Citgo Asphalt GA Granite Aggregate Rut Depth mm % PPA 1% PPA Passes

28 Next some chemistry Ca(OH) 2 + H 3 PO 4 = CaHPO 4.2H 2 O 74 lbs 98 lbs 172 lbs If the mix contains 1% Lime and 1% Phosphoric Acid There is a Large Excess of Lime (25X)

29 Lime Treated Aggregate Aggregates were treated with 1% lime added as a wet slurry and dried. Chemistry shows the lime overwhelms the PPA by 25:1 Lime showed up very well in the tests Stripping was unaffected by PPA modification Addition of 1% lime to the neat binder did not show any stiffness increase

30 73 Effect of Lime on Asphalt Stiffness 1.0KPa Citgo BP Whiting Lion Oil deg C % Lime

31 35 Hamburg 50degC Citgo Asphalt Lime Treated Sandstone Aggreagte Rut Depth mm % Lime 1% Lime 0.5% PPA 1% Lime 3% PPA Passes

32 25 Hamburg 50degC Citgo Asphalt Lime Treated Limestone Aggregate Rut Depth mm % Lime 1% Lime 1% Lime 1% PPA 1% Lime 1% PPA Passes

33 20 Hamburg 50degC Citgo Asphalt GA Granite Aggregate 18 Rut Depth mm % Lime 1% Lime 1% Lime 1% PPA 1% Lime 1% PPA Passes

34 More Chemistry-Titration of Amine Antistrip with PPA Titrate an ethanol solution of antistrip with phosphoric acid 1gm Adhere LOF equivalent to 0.49 gm PPA 1gm Adhere LA-2 equivalent to 0.57 gm PPA If the binder contains 0.5% of antistrip and 1% of PPA then the PPA is in excess, about 25% being neutralized by the amine

35 Arr-Mazz LA-2 Additive did not work well with Sandstone or Limestone Sandstone PPA worse with both aggregates Additive worked well with GA Granite PPA modification showed no effect with Granite.

36 35 Hamburg 50degC Citgo Asphalt Sandstone Aggregate Rut Depth mm % LA-2 0.5% LA-2 0.5% LA-2 1% PPA 0.5% LA-2 1% PPA Passes

37 35 Hamburg 50degC Citgo Asphalt Limestone Aggregate Rut Depth mm % LA-2 0.5% LA-2 0.5% LA-2 1% PPA 0.5% LA-2 1% PPA Passes

38 Hamburg 50degC Citgo Asphalt GA Granite Aggregate Rut Depth mm % LA-2 0.5% LA-2 0.5% LA-2 1% PPA 0.5% LA-2 1% PPA Passes

39 Arr-Mazz LOF Additive almost passed the test with Sandstone PPA Modification did not have much effect Additive did not worked well with Limestone PPA modification made it worse Additive worked well with Granite PPA modification had no effect

40 Hamburg 50degC Citgo Asphalt Sandstone Aggregate Rut Depth mm % LOF % LOF % LOF % PPA 0.5% LOF % PPA Passes

41 Hamburg 50degC Citgo Asphalt Limestone Aggregate Rut Depth mm % LOF % LOF % LOF % PPA 0.5% LOF % PPA Passes

42 Hamburg 50 degc Citgo Asphalt GA Granite Aggregate 20 Rut Depth mm % LOF % LOF % LOF % PPA 0.5% LOF % PPA Passes

43 Innovalt W 2-Ethylhexyl phosphate A phosphate ester and not expected to be affected by PPA Additive worked well with sandstone PPA modification made it a lot worse Additive did not work well with Limestone PPA improved it slightly Additive worked well with Granite and was not affected by PPA modification

44 Hamburg 50degC Citgo Asphalt Sandstone Aggregate Rut Depth mm % Innovalt-W 0.5% Innovalt-W 0.5% Innovalt-W 1% PPA 0.5% Innovalt-W 1% PPA Passes

45 Hamburg 50degC Citgo Asphalt Limestone Aggregate 35 Rut Depth mm % Innovalt-W 0.5% Innovalt-W 0.5% Innovalt-W+ 1% PPA 0.5% Innovalt-W+ 1% PPA Passes

46 Hamburg 50degC Citgo Asphalt GA Granite Aggregate 20 Rut Depth mm % Innovalt-W 0.5% Innovalt-W 0.5% Innovalt-W 1% PPA 0.5% Innovalt-W 1% PPA Passes

47 Non Amine antistrip Innovalt-W This is already a phosphate ester and would not react further with phosphoric acid PPA modification would not be expected to affect the antistrip performance With this asphalt/stripping aggregate combination this is not true

48 Conclusions Hamburg Testing Test is only an indication PPA increases moisture sensitivity of neat binders Action of amine and phosphate ester antistrips is aggregate specific- PPA generally increases moisture sensitivity With Lime Treated Aggregates the moisture sensitivity is unaffected by PPA modification Users need to test each asphalt/aggregate/antistrip combination.

49 Questions?