土木專業(yè)畢業(yè)外文翻譯--粉煤灰含量和骨料級配在混凝土路面耐久性的影響（英文）

1、Effect of Fly Ash Content and Aggregate Gradation on the Durability of Concrete PavementsSukhvarsh Jerath, P.E., M.ASCE1; and Nicholas Hanson2Abstract: In the regions where temperature fluctuations are large ranging from

2、 below freezing in winter to high temperatures in summer, concrete highway pavements fail because of poor durability rather than lack of strength. The effect of fly ash replacement of Portland cement and the use of dense

3、 aggregate gradation on the durability of concrete mixtures is studied in this research. Eight concrete mixtures were cast, four of them using the aggregates as per current specifications and the other four mixtures usin

4、g dense graded aggregates. For each of these two gradations, different fly ash replacement amounts of 30, 35, 40, and 45% for Portland cement were used. All mixtures were designed for 6% air content, and 25–38 mm ?1 to 1

5、 1/2 in.? slump for the freshly mixed concrete. The study shows that the increase of fly ash content from 30 to 45% increased the durability of concrete mixtures without the loss of compressive and flexural strengths. Th

6、e concrete mixtures containing dense graded aggregates, and higher percentage of fly ash required less water content indicating the beneficial effects of fly ash and dense graded aggregates. When the fly ash content was

7、increased from 30 to 45% in the concrete mixtures, the permeable pore space decreased in the specific gravity, absorption, and voids in hardened concrete tests; the electric charge passing through the layers reduced in t

8、he rapid chloride ion permeability tests; and the spacing factors were smaller in the microscopical determination of air-void tests indicating greater durability. These experimental results proved the benefit of using hi

9、gher content of fly ash in concrete. The use of dense graded aggregates also proved beneficial.DOI: 10.1061/?ASCE?0899-1561?2007?19:5?367?CE Database subject headings: Aggregates; Durability; Fly ash; Freeze-thaw; Concre

10、te pavements; Voids.IntroductionConcrete disintegration and durability problems in highway pave- ments have been reported in many cold regions due to frost and harsh weather conditions in winter. Water happens to be cent

11、ral to most durability problems in concrete, therefore a concrete will be more durable if there is little or no evaporable water left after drying. If we can use an aggregate gradation where the remaining air voids in th

12、e aggregate are less, then we will need less paste to fill them and this in turn will reduce the available evaporable water. The ASTM C 33-00 ?ASTM 2001? allows 80–100% of the material to pass the No. 8 sieve. This speci

13、fication along with the standard coarse aggregate designations, results in the removal of large portions of intermediate size particles. The aggregate made up of all ranges of particles minimizes paste volume and increas

14、es durability. The current practices use a mixture of 60:40 coarse to fine aggregates ratio, to get the combined aggregate that is called gap-graded. In this mixture of aggregates, there are not enough intermediate size

15、particles that are between No. 4 and No. 16 sieve opening sizes.An evaluation of the construction records and pavement cores by Muszynski et al. ?1997? from projects constructed since 1987 suggest that poor mix proportio

16、ning practices and a high variabil- ity in aggregate gradation directly affects the constructability of pavements. The research showed that aggregate grading controls are an effective method of improving the placement ch

17、aracteris- tics and finish quality of new concrete pavements. Goltermann et al. ?1997? indicated that the selection and combination of the aggregates has a dominating influence on the quality and price of concrete and sh

18、ould receive more attention. There is some subjective evidence that the total aggregate gradation can be op- timized to yield improved concrete performance during construc- tion and service life, but it is not absolutely

19、 convincing. The in- fluence of total aggregate gradation on the freeze-thaw durability of concrete test specimens that employed a variety of commonly used aggregates was examined by Cramer and Carpenter ?1999?. The opti

20、mized gradation mixes did not show consistently im- proved performance compared with the control mixtures consist- ing of 60–40 blend of naturally occurring coarse/fine aggregates, but showed better performance in compar

21、ison with the near-gap graded mixtures. The use of fly ash is in harmony with the concept of sustain- able development. To considerably increase the utilization of fly ash, it is necessary to advocate the use of concrete

22、 that will in- corporate large amounts of fly ash as replacement for cement. In two investigations, one used eight fly ashes and two Portland cements from U.S. sources ?Bilodeau et al. 1994?, and in the other six fly ash

23、es and five ASTM Type I Portland cements were se- lected from sources across various regions of Canada ?Siva- sundaram and Malhotra 2004?. Based upon test results it was concluded that the air-entrained high volume fly a

24、sh concretes exhibited excellent durability characteristics. In a paper ?Jiang1Professor, Dept. of Civil Engineering, Univ. of North Dakota, Upson II Room 260, 243 Centennial Drive Stop 8115, Grand Forks, ND 58202- 8115.

25、 2Structural Engineer, Ulteig Engineering Inc., 5201 East River Rd., Suite 308, Fridley, MN 55432. Note. Associate Editor: Baoshan Huang. Discussion open until October 1, 2007. Separate discussions must be submitted for

26、individual papers. To extend the closing date by one month, a written request must be filed with the ASCE Managing Editor. The manuscript for this paper was submitted for review and possible publication on June 6, 2005;

27、ap- proved on September 18, 2006. This paper is part of the Journal of Materials in Civil Engineering, Vol. 19, No. 5, May 1, 2007. ©ASCE, ISSN 0899-1561/2007/5-367–375/$25.00.JOURNAL OF MATERIALS IN CIVIL ENGINEERI

28、NG © ASCE / MAY 2007 / 367Downloaded 30 Dec 2010 to 220.249.72.3. Redistribution subject to ASCE license or copyright. Visit http://www.ascelibrary.orgExperimental ProgramA total of eight mixtures were designed in t

29、his study, and the constituent proportions for the concrete mixtures are given in Table 3. Concrete mixtures with a “GG” designation used gap- graded aggregates, whereas “DG” designation mixtures were cast using dense-gr

30、aded aggregates. Percentages after the letters GG and DG in a mixture designation denote percentage of fly ash replacement for Portland cement. For example, GG-30% is a con- crete mixtures containing 30% fly ash replacem

31、ent for cement and gap graded aggregates, where as DG-40% is a concrete mixture containing 40% fly ash and dense graded aggregates. This study integrated the practices of using dense-graded aggregates and the replacement

32、 of Portland cement by fly ash to achieve maximumpossible durability. Concrete mixture GG-30% is currently used by the NDDOT for highway pavements. It contains 334.2 kg of cementitious material per cubic meter ?564 lb/yd

33、3? of concrete with 30% fly ash replacement for Portland cement, 6% air con- tent, and enough water to give 25–38 mm ?1 to 1 1/2 in.? slump. Mix GG-30% is a control mixture in this research. The amount of water required

34、was determined by trial and error on a test batch to attain the desired slump of 25–38 mm ?1 to 1 1/2 in.?. The air- entraining admixture dosage was also determined in a similar manner. Various ASTM ?ASTM 2001? standard

35、tests were conducted on the freshly mixed and hardened concrete. The t-test is used here to compare the average values of the control mix GG-30%, and other mixes, for strength and durability tests assuming un- equal vari

36、ances between two samples. Microsoft Excel was used to perform the data analysis. The determination of whether there is statistically significant difference between the two means is reported as a P value. Null hypothesis

37、, H0: ?x??y?0, where ?x and ?y are the means of the two samples, ?x being the larger of the two, is used to calculate the P value. The smaller the P value, the more certain we can be that H0 is false, and there is a diff

38、er- ence between the two samples’ averages.Test ResultsPlastic PropertiesThe experimental test results include comparison of plastic and hardened concrete properties made with gap and dense graded aggregates, and differe

39、nt percentages of fly ash replacement of Portland cement. The plastic properties of unit weight, air content, and slump are given in Table 3 for various concrete mixtures. The water/cementitious ratio varied between 0.36

40、 and 0.37. The airTable 2. Sieve Analysis of AggregatesSieve sizeCumulative percentage passingCoarse aggregate Intermediate aggregate Fine aggregateCombined aggregate ?gap graded?Combined aggregate ?dense graded?25.0 mm

41、100 100 100 10019.0 mm 93 100 96 9212.5 mm 55 100 73 779.5 mm 21 100 100 53 63No. 4 0.6 68 100 40 47No. 8 0.3 31 90 36 35No. 16 1 60 24 18No. 30 33 13 10No. 50 14 6 4No. 100 3.8 1.5 1No. 200 2.4 1.0 0.7Table 3. Mix Desig

42、nations and ProportionsMix designationUnitGG-30% GG-35% GG-40% GG-45% DG-30% DG-35% DG-40% DG-45%Date September 5, 2002 September 12, 2002 September 18, 2002 September 25, 2002 November 14, 2002 January 24, 2003 January

43、27, 2003 January 30, 2003Cement kg/m3 234.0 217.2 200.5 183.8 216.9 201.6 186.0 170.7lb/ft3 14.6 13.6 12.5 11.5 13.6 12.6 11.6 10.7Fly Ash kg/m3 100.3 117.0 133.7 150.4 93.2 108.4 124.1 139.4lb/ft3 6.3 7.3 8.4 9.4 5.8 6.

44、8 7.8 8.7Fine aggregate kg/m3 759.5 753.1 751.3 747.7 579.6 579.2 579.9 577.4lb/ft3 47.5 47.1 47.0 46.7 36.2 36.2 36.2 36.1Intermediate aggregate kg/m3 0 0 0 0 478.2 477.9 476.4 476.1lb/ft3 0 0 0 0 29.9 29.9 29.8 29.8Coa

45、rse aggregate kg/m3 1,110.4 1,113.2 1,114.7 1,116.4 860.4 858.7 857.2 856.2lb/ft3 69.4 69.6 69.7 69.8 53.8 53.7 53.6 53.5Workability factor 36.2 36.2 36.2 36.2 34.9 34.9 34.9 34.9Coarseness factor 74.3 74.3 74.3 74.3 54.

46、6 54.6 54.6 54.6Water kg/m3 123.4 123.4 120.5 119.1 115.2 115.2 113.4 114.5lb/ft3 7.7 7.7 7.5 7.4 7.2 7.2 7.1 7.2Water/cementious ratio 0.37 0.37 0.36 0.36 0.37 0.37 0.37 0.37Unit weight kg/m3 2,307.5 2,366.1 2,362.1 2,3

47、33.9 2,526.4 2,484.8 2,500.8 2,521.6lb/ft3 144.2 147.9 147.6 145.9 157.9 155.3 156.3 157.6Air content ?%? 6.03 5.73 5.87 6.43 6.03 6.60 6.43 5.83Slump mm 40.1 40.1 33.8 38.1 42.4 33.8 33.8 29.7in. 1.58 1.58 1.33 1.50 1.6