EFFECT COMPACTION OF BITUMINOUS CONCRETE

Transcription

1 OF ANTISTRIPPING ADDITIVES ON EFFECT COMPACTION OF BITUMINOUS CONCRETE THE W. Maupin, Jr. G. Scientist Research opinions, findings, and conclusions exnressed in this ( are those of the author and not necessarily those of report of Highways & Transportation and Department University of Virginia) the by the sponsoring agencies.) Highway and Transportation Research Council Virginia Cooperative Organization Sponsored Jointly by the Virginia (A Charlottesville, Virginia November 198! VHTRC 92-R23

2 BITUMINOUS RESEARCH ADVISORY COMMITTEE R. L. ALW00D, Chairman, District Materials Engineer, VDH&T A. D. BARNHART, District Materials Engineer, VDHST P. F. CECCHINI, District Engineer, VDH&T J. L. CORLEY, Assistant District Engineer- Construction, VDHST W. R. DAVIDSON, Assistant Maintenance Engineer, VDHgT W. A. DENNISON, District Materials Engine=r_, VDH& C. E. ECHOLS, Asst. Prof. of Civil Engineering, U. Va. R. V. FIELDING, Materials Engineer, VDH&T C. S. HUGHES II!, Highway Research Senior Scientist, VHgTRC A. B. JOHNSON, Assistant Construction Engineer, VDH&T J. T. LOVE, Materials Engineer, Materials Division, VDHgT H. E. MARSHALL, District Engineer, FHWA T. W. NEAL, JR., Chemistry Lab. Supvr., Materials Div., VDH&T R. S. THOMAS, Bituminous Engineer- Maintenance Div., VDH&T R. D. WALKER, Chairman,.Dept. of Civil Engineering, VPI & SU i±

3 objective of this investigation was to determine the of antistripping additives on the compaction of bituminous effect To do this, the densities obtained on test sections concrete. and without additive were compared. Comparisons of nuclear with and the void contents of cores from the pavement revealed densities significant differences. Also, there were no significant differ- no in the optimum numbers of roller passes required to attain ences density on the sections with and without additive. maximum Based the results of this investigation, the inability to on the desired densit9 should not be attributed to the use of achieve ABSTRACT of the asphalt cement were probably not influenced enough properties the additives to affect compaction. by antistripping additives.

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5 OF ANTISTRIPPING ADDITIVES ON EFFECT COMPACTION OF BITUMINOUS CONCRETE THE W. Maupin, Jr. G. Scientist Research of the most important factors in the attainment of pave- Some density are ambient temperature, mix temperature, lift thick- ment service life of the pavement will be realized and no price full for construction will be assessed. adjustment paving contractor reported an incident where apparently the A density could be obtained only when the antistripning addi- required specified for the mix was omitted; therefore, a possible addi- tive factor influencing density was identified. Much of the plant tional requires an antistripping additive, and it seemed reasonable mix the additive might affect the viscosity of the asphalt cement that attempt was made to locate jobs using S-5 mixes with An that was not susceptible to stripping and that were being aggregate additives and three asnhalts were tested in the mix Three shown in Table i. At least one tanker of asphalt cement designs no additive was used on each job. If the contractor had with one tank for storing asphalt cement, the tank had to be emptied only completely when a changeover was made from additive to no additive. by PURPOSE AND SCOPE rolling equipment and procedure, and mix components. It is ness, that these factors be properly considered so that the important thereby result in compaction difficulties. Consequently, an and was undertaken to determine the effect of the additive investigation on compaction. achieve the objective of the investigation, density was To and compared on test sections with and without additive monitored for four paving projects (see Appendix A). awarded to contractors who were willing to cooperate.

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7 optimum number of roller passes was obtained for each the two mixes in a test section by establishing roller patterns of a nuclear device. optimum compactive effort was used with the placement of each mix. roller pattern also indicated. for the compaction characteristics of the mixes were affected whether the additive. by after the sections were completed, ten 4-in. cores were Soon for each mix and transported to the laboratory for density obtained Nuclear densities were also obtained at 20 locations determinations. each mix. for of the plant mixes were obtained for the fabrication of Samples specimens to be used in laboratory tests. Marshall Density and Void Determinations necessary, the surface layer of the cores was separated When the other layers by sawing or chiseling. n the cores were from by fan at room temperature overnight. bulk specific dried was obtained by ASTM test method D2726; however, no correc- gravity was attempted for any moisture that might have remained in tion cores. the of the cores were combined and the maximum specific Several was determined by ASTM test method D2041 using a type A gravity percent air voids was calculated by ASTM test method D3203. tests were performed according to ASTM test method Marshall on plant mix obtained during construction of the test section. D1559 total mix, voids filled with asphalt, and voids in the min- Voids aggregate were calculated to determine the compactibi!ity eral TESTING PROGRAM Field Tests Labor at o_ry T e s ts container. Marshall Tests of each mix.

8 of asphalt cement with and without additives were Samples at the hot mix plant during construction of the test ob-tained Viscosity tests were performed at 140 F and 275 F by sections. test methods D2!71 and D2170, respectively.. penetration ASTM tests were performed according to Virginia test method Bottle to verify the presence or absence of antistripping additives #55 the field test sections. test was conducted on asphalt in sampled at the hot mix plant during the construction of the cement of the jobs and also on samples of plant mix from job #4 to all the presence or absence of additive and to gather infor- verify on predicted performance.* This information will be useful mation the implementation of the modified stripping test. in Density and Voids optimum number of roller passes required for maximum den- was equal for mixes with and without additive on each of the sity jobs. None of the mixes displayed any lack of stability four rolling; however, some cracking, apparently caused by the during pavement densities determined by the nuclear device are in Table 2 and the voids of the cores in Table 3. re listed not a significant difference at a 95% confidence level between was with and without additive on any job. voids total mix sections high V M low VFA and high VMA of the Marshall tests renorted by subsequently. Asphalt Cement of the asphalt cements was measured by ASTM test method DS. Bottle and Stripping Tests test section. a modified procedure described in Transportation Re- Using Record 712, stripping tests were performed on cores from search RESULTS finish roller, was observed in both mixes on job 2. high for all mixes except those on job 4. plant mix was were not compactible, with-the exception of job 4, as reflected probably *Manp -n, G. W. Jr. "Imniementat{on of Stripping Test for Asphaltic Concrete" Transnortation Research Record 7 2, 1979

9 voids and stabilities from Marshall tests on nlant mix listed in Table 4. re was a significant difference in voids are mix between the mixes with and without additive on only total I, and this difference was attributed to the very low vari- job in the test results. voids total mix on jobs 1-3 were ability or very close to the upper specification limit of 6%, and outside voids filled with asphalt were below or very close to the lower the limit of 65%. At the 95% confidence level only job specification produced a significant difference between the average stabilities 4 mixes with and without additive. of Table 2. Nuclear Densities, lb./ft. 3 With Addit ive Without Additive Job I i Table 3. Percent Voids Total Mix Job With Additive Without Additive I I0.i ! Marshall Tests

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11 additives sometimes cause changes in the Antistripping physical properties of the asphalt cement. prop- original of the asphalt cements with and without additive are erties in Table 5. listed values were 3 to 9 units higher for the asphalt Penetration containing additive. viscosity at 275 F was slightly cements for the asphalt cements with additive, and the additive less the viscosity at 140 F to decrease by 90 to 260 poises. caused test values remained within the specification limits for All and the physical changes caused by the additives would AC-20, probably not affect the compaction characteristics of the mixes. Tests bottle test should fndicate positive results with additive present in both cases. It is possible that a small amount was additive was present at the location at which the "no additive" of was taken or that the storage tank was not emptied com- sample of the asphalt containing the additive. pletely to the results of the stripping tests, given in According 7, there was a definite improvement of the TSR of the sec- Table containing additive over the TSR of the section with no tion on job 4. se results indicate that at least there additive more additive in the mix in the additive section than. in the was in the no additive section. TSR of the sections with mix of additive, respectively. TSR of the section with absence on job 2 was not significantly higher than the TSR of additive section with no additive; therefore, there is no definite the of the presence or absence of additive. It is possible indication that the additive was present but not effective in this case. summary, the results indicate additive was present when In and that possibly a very small amount was present in claimed, Asphalt Cement Bottle. a nd,,,,str,.,,.,ipping. and negative results when there is no additive. As can be present in Table 6 all jobs except job 4 yielded such results. seen of asphalt cements supposedly with and without additive samples job 4 all yielded positive results, indicating that additive on was significantly greater than the TSR of sections with additive additive on jobs i and 3,thereby verifying the presence and no the section "without additive" on job 4.

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13 (cores) mix) (plant re was no significant difference in densities of mixes I and without additives. with presence of additive did not influence the optimum number roller passes required for maximum density. of properties of the asphalt cements were probably not enough by the additives to affect compaction. influenced Table 6. Results of Bottle Tests Job With Additive Without Additive I Positive Negative 2 Positive Negative 3 Positive Negative 4 Positive Positive Table 7. Results of Stripping Tests Tensile Strength Ratio Job With Additive Without Additive I (cores) (cores) (cores) CONCLUSIONS

14 inability to achieve the desired density of bituminous should not be attributed to the use of antistripping concrete Attention should be focused upon the effects of additives. type, mix design, and compaction procedures.* aggregate RE C0MMENDAT! 0N G. W. Jr., "Probi=ms in chieving Density in Asnhaltic. Maupin," Vi ginia Highway and Transportation Research Council, Concrete", Virginia, February Charlottesville, I0

15 Salem districts for helping to arrange the test sections, obtain- and cores, performing field tests, and providing traffic control. ing AC KN 0 WLE DGEME NT S is expressed to Virginia Department of Highways Appreciation Transportation personnel in the Culpeper Lynchburg, Richmond, and thanks are extended to the contractors for cooperating in Also, of the test sections. construction i I

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17 APPENDIX A Job Locations Job #i Route 24, Campbell Co., July 1978 SECO-OP Pole Evinzton Job #2 Route 460, Dinwiddie Co., Sept Additive // No 0.15 Mi Mi Mi.!

18 Mi. 0.2 Route 631 to Mi. 1.3 Mi. to Route #4- Route 460, Blacksburg Bypass Job Co., Sept Montgomery M±. J 0.85 ft. 150 Job #3 Route 6i2, Orange Co., Oct ditive No Additive C&P VA Pole 62UA36 EBL WBL 0.2 Mi. Route 314