Word count: 3,975 words text + 11 tables/figures x 250 words (each) = 6,725 words Submission Date: August 1, 2016

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1 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay 0 0 MAXIMUM PARTICLE SIZE, FINES CONTENT AND DUST RATIO INFLUENCING BEHAVIOR OF BASE AND SUBBASE COURSE AGGREGATES Rabindra Chaulagai Graduate Research Assistant rchaula@siue.edu Abdolreza Osouli, Corresponding Author Assistant Professor Edwardsville, IL aosouli@siue.edu Sajjad Salam Graduate Research Assistant ssalam@siue.edu Erol Tutumluer Professor, Paul F. Kent Endowed Faculty Scholar tutumlue@illinois.edu Sheila Beshears Aggregate Technology Coordinator Heather Shoup Central Office Geotechnical Engineer Matthew Bay Undergraduate Research Assistant mabay@siue.edu Civil Engineering Department Southern Illinois University Edwardsville Edwardsville, IL Department of Civil and Environmental Engineering University of Illinois at Urbana-Champaign N. Mathews, Urbana, IL 0 Illinois Department of Transportation Springfield, IL Word count:, words text + tables/figures x 0 words (each) =, words Submission Date: August,

2 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay ABSTRACT Unbound aggregate base and subbase layers are the main load bearing layers in a pavement structure. Size and shape properties of these aggregate materials should be controlled to ensure proper workability during construction and improved performance for pavement longevity. To investigate the effects of gradation, maximum particle size, percent passing the No. 0 sieve and dust ratio on quality of aggregates, an extensive number of soaked CBR tests were performed on a crushed limestone material. Dust ratio represents the amount of material passing (or minus) the No. 0 sieve divided by the amount of minus No. 0 sieve. The dust ratios studied were 0., 0. and.0. Two commonly used gradations in Illinois with maximum particle sizes of in. and in. were mainly studied to analyze the effect of fines content with respect to maximum particle size in the gradation. A typical range of percentages passing the No. 0 sieve (i.e., %, %, and %) was also considered. The results show that the gradation, dust ratio, and fines content should be all taken into account in the selection of aggregate properties for stability requirements. Aggregates with larger maximum size particles provide high strength and they are not affected as much by the increase in fines content. Whereas, aggregates with smaller maximum size particles indicate lower strength and are more influenced by changes in fines content. It is also concluded that samples with a dust ratio of.0 do not necessarily result in a low strength aggregate material. Keywords: Unbound aggregates, Soaked CBR, Maximum particle size, Fines content, Dust ratio

3 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay 0 0 INTRODUCTION Most commonly constructed conventional flexible pavements are made up of unbound aggregate base and subbase layers. These are the main load bearing layers which provide structural capacity, stability or resistance to deformation, and resistance to moisture induced deterioration through drainability. Pavement longevity is dependent on the performance of these layers which can be improved by properly selecting aggregate material properties for high strength and modulus characteristics. Among the most important properties influencing the strength of unbound aggregates are aggregate type (crushed vs uncrushed), gradation (maximum and average particle sizes, fines content, etc.), plasticity index (PI), dust ratio (DR), and moisture content (). Gradation characteristics are defined based on maximum aggregate size, particle size distribution and the amount of fines. Gradation has influence on aggregate density and strength (,, ). Maximum density can be achieved by a certain dense gradation which includes various sizes of particles and results in minimum voids. There are studies that recommend optimal gravel to sand sized particle ratio to achieve higher strengths (). The interaction of the effects of maximum size, gradation and fines content with strength is complex. Fines content, i.e., material passing the No. 0 sieve, has a profound effect on aggregate strength when the maximum particle size is large (). Moreover, permanent deformation susceptibility of an unbound aggregate layer is increased with an increase in fines content (). Beside gradation, deformation of the aggregate layer is also influenced by angularity and compaction of the aggregates. Angular material has better interlock and undergoes smaller permanent deformation after shakedown compared to rounded aggregate or gravel (). Compaction usually increases density, strength and stiffness of the material. Particles are reoriented and void space becomes smaller in a closely spaced arrangement. Greater California Bearing Ratio (CBR) values are commonly obtained for crushed limestone compared to gravel, when tested with the equal compaction effort (). Additionally, aggregate type (e.g., crushed vs uncrushed) becomes very important in determining the aggregate layer strength, when the fines content is low (). Different states have their own standards and have set up limits for the finer particle sizes and their properties, such as plasticity index, dust ratio and percent passing the No. 0 sieve. Dust ratio is defined as the ratio of the percentage of material passing the No. 0 sieve to that of the percent passing the No. 0 sieve. For example, Missouri Department of Transportation (MODOT) allows the use of up to % passing the No. 0 sieve material (), while Oklahoma DOT (OKDOT) () has capped it to % similar to Illinois DOT (IDOT) () and most other states. States such as Arkansas () and Colorado () have setup limits for the DR and PI as 0. and %, respectively. However, Indiana DOT (INDOT) () and New York DOT (NYDOT) () have a PI limitation of %. Hence, based on the quality of available material and site conditions, each state has established their own limits of aggregate index properties for highway construction. Moreover, national standards, such as American Society for Testing and Materials (ASTM) () and American Association of State Highway and Transportation Officials (AASHTO) (), have set up maximum allowable percentages passing the No. 0 sieve for the aggregate used in the base and subbase to % and %, respectively. The maximum dust ratio is set at 0. in both standards. This paper describes findings from an ongoing study focused on investigating effects of maximum particle size, dust ratio and percent passing the No. 0 sieve on strength and

4 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay 0 moisture-density relationship of a crushed limestone aggregate. A total of samples were engineered with two different target IDOT gradations (i.e., CA and CA ). These are dense graded gradations commonly utilized for the construction of unbound aggregate base and subbase layers in Illinois. Gradations similar to these but with different labels are commonly used by other states. Each sample configuration was prepared at to different moisture contents to identify the moisture-density relationship following the Standard Proctor test procedure per AASHTO T (). Then, soaked CBR tests were conducted on each sample per AASHTO T () to represent the strength of aggregates under severe conditions. It is worth noting that % of CBR samples were repeated to verify the obtained test results. ENGINEERED SAMPLES AND INDEX PROPERTIES The maximum particle sizes of CA and CA gradations are in. and in., respectively. For both gradations (i.e., CA and CA ), three different fines contents, i.e., percentages passing the No. 0 sieve, (i.e., %, %, %) and three different dust ratios (i.e., 0., 0.,.0) were considered when engineering the samples. The upper and lower limits of the two aggregate gradations (i.e., CA and CA ) are shown in Figure. The plasticity index of all prepared samples was limited to % in order to be within the acceptable limit of standards and state specifications. Figure shows the developed test matrix. Sample labels of A, B, and C designate gradations that have dust ratios of 0., 0., and.0, respectively. For samples that represented the CA gradation, the combination of a fines content of % and a dust ratio of 0. was logically impossible. Therefore, Group A- samples were not prepared for CA gradations. The Fuller curve maximum density gradation as given in Equation () was used to develop the target gradations for materials with sizes greater than the No. sieve. Percent passing (P) = x 0 () where d is the opening size of sieve and D is the maximum particle size, while n is a constant value considered as 0. to achieve a high density (). Upper and lower limits for the corresponding sieve sizes were also considered during the development of target gradations. Due to the differences in dust ratios, percent passing the No. 0 sieve was different even for the sample with the same amount of percent passing the No. 0 sieve. Figure a and Figure b show the target gradations that fall into the category of CA and CA gradations, respectively. It should be mentioned that coarse particle correction was applied to CA gradation per AASHTO T ().

5 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay Percent Finer (%) Percent Finer (%) (a) (b) 0 0 FIGURE (a) CA target gradations (b) CA target gradations studied VOID RATIO Sieve Size (mm) Sieve Size (mm) CA Upper Limit CA Lower Limit C-CA--A C-CA--B C-CA--C C-CA--A C-CA--B C-CA--C C-CA--A C-CA--B C-CA--C Void ratio is a function of shape, angularity and surface texture of an aggregate material in addition to compaction effort. It is closely linked to its permanent deformation potential (). Based on the dry densities of the samples with the different index properties, the ranges of void ratio were calculated as shown in Table. 0. CA Upper Limit CA Lower Limit C-CA--A C-CA--B C-CA--C C-CA--A C-CA--B C-CA--C C-CA--B C-CA--C

6 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay FIGURE Aggregate property test matrix studied TABLE Ranges of Void Ratio for CA and CA Crushed Limestone Gradations Fines content Dust ratio Range of void ratio with CA gradation (%) % % % NA = not available Range of void ratio with CA gradation (%) NA For samples with the same percent passing the No. 0 sieve and dust ratio, the void ratio was found to be generally greater in the CA gradation than in the CA. For example, in case of CA crushed limestone, the range of void ratio for % passing the No. 0 sieve with a dust ratio of 0. was found to be 0. to 0. while for the CA crushed limestone, it ranged from 0. to 0.. Since the CA gradation consists of larger size particles, it has larger voids between the particles. In addition, as the fines content was increased from % to %, the range of the void ratio decreased expectedly.

7 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay EFFECT OF INDEX PROPERTIES ON DRY DENSITY Figure shows the maximum dry densities of the CA samples with different percent passing the No. 0 sieve at the optimum moisture contents (OMCs). As the fines content was increased from % to % for all samples A, B and C (for the dust ratios of 0., 0., and.0, respectively), an increase in dry density was generally observed. The average dry densities of samples with %, %, and % passing the No. 0 sieve were pcf, pcf, and, respectively. Since, greater amount of fines fill the void space among the particles, a higher dry density was achieved at % passing the No. 0 sieve. Additionally, while comparing the maximum dry densities based on the dust ratios, a higher dry density was obtained for the samples with the dust ratio of 0. (i.e., Sample A) as shown in Figure. Maximum dry density had a decreasing trend with increasing dust ratio in samples with the % and % fines contents. This implies, a higher dust ratio has a detrimental effect on the sample, if the fines content is less than or equal to %. Maximum Dry Density (pcf) 0 A B C 0 0 No. 0 Sieve % No. 0 Sieve % No. 0 Sieve % FIGURE CA gradation maximum dry densities as a function of fines content at OMC Similarly, as shown in Figure, the same trend of maximum dry density was obtained for the CA samples. A higher dry density was always obtained for the sample with a higher percent passing the No. 0 sieve. Similar to the CA samples, the CA crushed limestone samples with a dust ratio of 0. had higher dry densities than those with dust ratios of 0. and. For example, as shown in Figure, for the % fines content, maximum dry densities of pcf, pcf and pcf were obtained for the samples with dust ratios 0., 0. and, respectively. It is worth mentioning that the maximum dry densities of the CA samples were typically to pcf less than the ones for the CA samples due the presence of larger void spaces in the CA gradations.

8 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay Maximum Dry Density (pcf) 0 A B C 0 0 No. 0 Sieve % No. 0 Sieve % No. 0 Sieve % FIGURE CA gradation maximum dry densities as a function of fines content at OMC EFFECT OF FINES CONTENT ON STRENGTH For all samples, soaked CBR values obtained at OMC, OMC-.% and OMC+.% were averaged at the corresponding %, % and % fines contents. As shown in Figure a, there is a general, but very gradual, decreasing trend with increase in fines content in CA samples with DRs of 0. and 0. (i.e., Group A and B). It should be noted that both of these DR values are within the acceptable limits of AASHTO M for aggregates as base and subbase. The CA crushed limestone samples with a DR of 0. (i.e., Group A) is the only group that their strength decreases substantially with % minus No. 0 sieve. However, for a DR of.0 (i.e., Group C), the average soaked CBRs values have an increasing trend with higher fines content and all are above 0%. It should be noted per AASHTO Μ and ASTM D- that these materials with a DR of.0 are outside of currently acceptable limits aggregates for base and subbase application. According to Figure b, average soaked CBR values of crushed limestone CA samples had an increasing trend with the increase in fines content. The presence of larger voids in the CA gradation was the reason for lower soaked CBR values when fines content were low. The lowest average soaked CBR value was observed for samples with a DR of.0 and % fines content. However, interestingly samples with a DR of.0 but at higher fines content had average soaked CBR values of more than %. In fact, the sample with a DR of.0 and % minus No. 0 sieve outperformed almost all other samples in terms of strength.

9 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay Average Soaked CBR (%) Average Soaked CBR (%) (a) Percent Passing No. 0 Sieve (%) (b) FIGURE Average soaked CBR values for (a) CA and (b) CA crushed limestone gradations EFFECT OF DUST RATIO ON STRENGTH C-CA-A C-CA-B C-CA-C C-CA-A C-CA-B C-CA-C Percent Passing No. 0 Sieve (%) Group A, B and C samples had the dust ratio values 0., 0. and, respectively. In the case of the CA crushed limestone, as shown in Figure, the soaked CBR values at OMCs were greater for the samples with dust ratio of 0. (i.e., Group B) compared to the samples having DR values of 0. and.0 regardless of the fines content. The pronounced effect of a lower dust ratio on strength was observed only for samples with the highest fines content. The soaked CBR value at OMC for % fines content and dust ratio of 0. (Group A) was only %. This implies that CA aggregates with low dust ratios and high fines contents are not suitable for the base/subbase application. Similar trend of soaked CBR values were observed in case of the CA crushed limestone. As the dust ratio changed from 0. to, for all the CA samples, soaked CBR values

10 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay at OMC were drastically lower than the CA samples. The soaked CBR values at OMC for the CA samples with a DR of.0 at %, % and % passing the No. 0 sieve, were %, %, and % less than those for the CA samples, respectively. In all cases, the CA samples with a dust ratio of, which has a gap graded gradation in terms of fines content, had a lower CBR at OMC. The soaked CBR values at OMC of all other samples were more than 0% Soaked CBR (%) FIGURE Soaked CBR values at OMC for the CA and CA crushed limestone gradations STRENGTH ZONES FOR CA AND CA GRADATIONS For all samples considered, soaked CBR tests were conducted at four to five different moisture contents. Therefore, CBR values obtained at OMC, OMC-.% and OMC+.% were averaged and plotted as shown in Figure a and Figure b for the CA and CA crushed limestone gradations, respectively. These figures depict the strength of a sample with respect to two index properties at the same time. Based on the average soaked CBR results, three strength zones for crushed limestone material were defined. Samples with the average soaked CBR value less than 0% were defined in a Low strength zone. Samples with the average soaked CBR value ranging from 0% to % were defined in a Medium zone while CBR values greater than % were defined in a High strength zone. It is worth noting that the data of this study are limited and some uncertainty in defining the boundaries are expected. As shown in Figure a, the CA crushed limestone samples show low CBR strengths when the percent passing the No. 0 sieve is high and the dust ratio is low. In other combinations of dust ratio and minus No. 0 sieve zones of medium and high strength are noticeable. Note that the maximum size of particles in the CA gradation is less than -in.,

11 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay whereas, 0% of the CA gradation particle sizes are larger than -in. and therefore include larger voids in the aggregate matrix. Accordingly, the interaction of the coarse aggregate skeleton and the void structure with the amount of fines is different. As shown in Figure b, regardless of the dust ratio, the inclusion of higher fines content, up to %, results in greater soaked CBR strengths. Therefore, the specifications for quality aggregates should take into account the gradation of the aggregates for the maximum and average particles sizes along with their PI, DR and fines content. The findings indicate that even though the dust ratio, gradation, PI and fines content of some aggregates may be within the specified limits of AASHTO M, their performance trends in terms of strength may be low. Therefore, the combinations of these properties are the most important and should be carefully taken into account to optimize the aggregate material selection for the stability and structural capacity requirements of unbound aggregate base and subbase courses. (a) Dust Ratio (b) Dust Ratio Medium High Medium Percent Passing No. 0 Sieve (%) Low High Medium FIGURE Strength zones established based on average CBR values at OMC and -/+.% OMC for (a) CA (b) CA crushed limestone gradations Low High Percent Passing No. 0 Sieve (%) Legend Average Soaked CBR Legend Average Soaked CBR

12 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay 0 0 SUMMARY AND CONCLUSIONS The strength and deformation characteristics of unbound aggregate materials used in pavement base and subbase courses are significantly influenced by aggregate type (crushed vs uncrushed), gradation (maximum and average particle sizes, fines content, etc.), plasticity index (PI), dust ratio (DR), and moisture content. Two different Illinois DOT dense graded gradations, i.e., CA and CA, with -in. and -in. maximum particle sizes, respectively, were studied in a laboratory research effort. A wide range of percent passing the No. 0 sieve values, i.e., %, % and %, were considered in the test matrix to analyze the impact of fines content with respect to the maximum particle size in the gradation to the strength property of a crushed limestone aggregate material. Moreover, three different dust ratios, defined by the amount of material passing (or minus) the No. 0 sieve divided by the amount of minus No. 0 sieve material, (i.e., 0., 0. and ) were investigated. Standard Proctor tests were conducted to determine the moisturedensity relationships. Soaked CBR tests were followed to determine the strength of the sample. As the percent passing the No. 0 sieve was increased, maximum dry densities of both the CA and the CA crushed limestone gradations increased. However, due to the -in. maximum particle size of the CA crushed limestone, which resulted in larger void spaces between the particles, lower dry densities were obtained compared to those of the CA crushed limestone. It is worth mentioning that although lower dry densities were obtained for the CA crushed limestone, soaked CBR strength values were still comparable to those of the CA samples. When the average soaked CBR values at OMC and -/+.% OMC were considered, the strength zones established showed medium to high strengths for all combinations of the CA gradations except for samples with high fines contents and low dust ratios. On the other hand, the strength zones of the CA gradation indicated that inclusions of higher fines content would, in general, result in high strengths regardless of the dust ratio. ACKNOWLEDGEMENT The authors would like to acknowledge the Illinois Department of Transportation and Illinois Center for Transportation for the support provided for this research. The authors also like to show gratitude to the undergraduate students Matthew Eck, Jacob Lewis, and Jalen Bachman who worked on this project. REFERENCES. Yoder, E. J. and M. W. Witczak. Principles of Pavement Design, Second Edition... Kamal, M. A., et al. Field and Laboratory Evaluation of the Mechanical Behavior of Unbound Granular Materials in Pavements. Transportation Research Record 0. Washington D.C.,, pp -.. Dawson, A. R., N. H. Thom and J. L. Paute. Mechanical Characterstics of Unbound Granular Materials as a Function of Condition. Proceedings of European Symposium Euroflex. A.G. Correia ed., Balkema Rotterdam,, pp. -.. Bennert, Thomas and Ali Maher. The Development of a Specification for Granular Base and Subbase material. No. FHWA-NJ

13 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay 0 0. Xiao, Yuanjie, Erol Tutumluer and John Siekmier. Mechanistic-empirical Evaluation of Aggregate Base and Granular Subbase Quality Affecting Flexible Performance in Minnesota. Transportation Research Record: Journal of Transportation Research Board.,, pp. -.. Gray, J.E. Charactertics of Graded Base Course Aggregates Determined by Triaxial Tests. Engineering Research Bulletin No.,.. Barksdale, Richard D. Influence of Aggregate Shape on Base Behavior." Transportation Research Record,, pp. -.. Lekarp, F, U. Isacsson and A Dawson. Permanent Strain Response of Unbound Aggregates. Journal of Transportation and Engineering, 00, pp -.. Yoder, E. J., Principles of Pavement Design, John Wiley and Sons, Inc.,.. Tutumluer, Erol, Debakanta Mishra and Abbas A. Butt. Characterization of Illinois Aggregates for Subgrade Replacement and Subbase. Illinois: Illinois Center for Transportation, 0.. Missouri Standard Specification for Highway Construction, Missouri Department of Transportation (MODOT),.. Oklahoma Standard Specifications for Highway Construction, Oklahoma Department of transportation (OKDOT), 0.. Standard Specifications for Road and Bridge Construction, Illinois Department of Transportation (IDOT), Springfield,.. Standard Specification for Highway Construction, Arkansas Department of Transportation (AKDOT),.. Standard Specification for Road and Bridge Construction, Colorado Department of Transportation (CODOT),.. Standard Specifications, Indiana Department of Transportation (INDOT),.. Standard Specifications, Newyork State Department of Transportation (NYSDOT),.. ASTM Standard D. Standard Specification for Materials for Soil-Aggregate Subbase, Base and Surface Courses, ASTM International, West Conshohocken, PA, AASHTO M. Standard Specification for Materials for Aggregate and Soil-Aggregate Subbase, Base and Surface Courses, American Association of State Highway and Transportation Officials, Washington D.C.,.. AASHTO T. Standard Method of Test for Moisture-Density Relations of Soils Using a.-kg (.-lb) Rammer and a 0-mm (-in.) Drop, American Association of State Highway and Transportation Officials, Washington D.C.,.. AASHTO T. Standard Method of Test for the California Bearing Ratio, American Association of State Highway and Transportation Officials, Washington D.C.,.. Thom, N. H. and S. F. Brown. The Effect of Grading and Density on the Mechanical Propoerties of a Crushed Dolomitic Limestone. Proceedings of the th ARRB Conference, Part.,, pp -0.. AASHTO T. Standard Method of Test for Correction for Coarse Particles in the Soil Compaction Test, American Association of State Highway and Transportation Officials, Washington D.C.,.

14 Chaulagai, Osouli, Salam, Tutumluer, Beshears, Shoup, Bay. Saeed, Athar, et al. NCHRP Report-, Performance-related Tests of Aggregates for Use in Unbound Pavement Layers. Washington D.C, 0.