International Journal of Civil Engineering and Technology (IJCIET) Volume 7, Issue 5, September-October 2016, pp. 466–476, Article ID: IJCIET_07_05_051 Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=7&IType=5 ISSN Print: 0976-6308 and ISSN Online: 0976-6316 © IAEME Publication
EFFECT OF FINE MATERIAL ON COMPACTION CHARACTERISTICS OF SUBBASE MATERIAL USING THE SUPERPAVE GYRATORY COMPACTOR Mohammed Y. Fattah Professor, Building and Construction Engineering Department, University of Technology, Baghdad, Iraq. Miami M. Hilal Lecturer, Building and Construction Engineering Department, University of Technology, Baghdad, Iraq. Huda B. Flyeh Graduate Student, Building and Construction Engineering Department, University of Technology, Baghdad, Iraq. ABSTRACT Soil compaction is defined as a method for mechanically increasing the density of soil by reducing the air volume from between particles. The main objectives of compaction are increasing strength, stiffness and stability of soil by reducing its compressibility and decreasing permeability of the soil mass by reducing its porosity. The Superpave Gyratory Compactor (SGC) was developed to compact pavement layer samples to densities similar to that obtained in the field after construction and traffic compaction. This research targeted two primary purposes: First evaluating the effect of water content on compaction charactereristics, second investigating the effect of fine material on dry density and CBR value of subbase material. To meet these research objectives, various water contents and percents of fine materials were used to compact the specimens. The results showed that the subbase material becomes stiffer when the fine materials increases from 5 % to 10 % and 13 % and the dry density increases which leads to increase in CBR value. Boch dry density and CBR decrease with the increase of water content bove the optimum water content. Key words: Subbase material, SGC, CBR , fine materials , dry density. Cite this Article: Mohammed Y. Fattah, Miami M. Hilal and Huda B. Flyeh, Effect of Fine Material on Compaction Characteristics of Subbase Material Using the Superpave Gyratory Compactor. International Journal of Civil Engineering and Technology, 7(5), 2016, pp.466 –476. http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=7&IType=5
1. INTRODUCTION Pavement structure response under load is very sensitive to the properties of the materials used in the base and subbase layers. The quality of pavement design is greatly dependent on the accuracy and manner in which the material properties are evaluated. A realistic characterization of layer materials is needed for the success of pavement design, especially for the mechanistic design approach. The subbase layer in a
http://www.iaeme.com/IJCIET/index.asp
466
[email protected]
Mohammed Y. Fattah, Miami M. Hilal and Huda B. Flyeh
pavement improves the supporting capacity, provides drainage, minimizes the detrimental effects of frost action, and provides uniform support to the upper layers. The subbase generally has the maximum thickness of all the layers of a flexible pavement, and therefore economy of road construction would depend upon maximum utilization of locally available material in the subbase construction. Aggregate gradation has effects on strength and modulus characteristics of aggregate base–granular subbase materials. The importance of specifying proper aggregate grading or particle size distribution has long been recognized for achieving satisfactory performance in pavement applications. Unbound granular materials are commonly used in aggregate base-granular subbase courses in flexible pavements. The main functions of these unbound pavement foundation layers are to distribute load through aggregate interlock and protect the weak subgrade beneath. Currently, there is a growing interest in the possibility of using an Superpave gyratory compactor SGC device to predict the construction compaction and life cycle of soils being used in base, subbase, and subgrade of roadways, runways, and taxiways. Several studies exist that investigate the use of the SGC for soils ranging from granular soils to clays. Many of these studies investigate by basing test procedures on approved asphalt testing procedures and varied the test parameters such as the angle of gyration, rate of gyration, number of gyrations, and other SGC test equipment variables to determine appropriate values. One study at Florida State University (Ping et al., 2002) explores the possibility of using the SGC to better predict the response of sandy soils to modern construction equipment. In summary, findings showed that varying the vertical stress, as a way of increasing the dry unit weight had little to no effect when the vertical pressure is above 200 kPa. Ping et al. used a maximum confining pressure of 500 kPa during all testing. The angle of gyration was reported to have some effect on the dry density of the sample when the number of gyrations is low, but the effect is minimal when the number of gyrations is increased. By varying the moisture content and keeping all other variables constant from test to test, the study shows that a moisture content and dry density curve can be plotted that resemble a modified Proctor moisture content curve. The most significant finding of the study is that the number of gyrations has the biggest impact on the dry density of the samples. More gyrations equates to higher dry densities (Ping et al., 2002). A separate phase of the study performed at Florida State University by Ping et al., (2003) investigates the effect of increased energy input on the dry density of the sample. In this phase, the pressure, number of gyrations, angle of gyration and gyration rate vary. By keeping the moisture content similar throughout testing, the study focused on varying the compactive energy input into the sample. A test performed on A2-4 sand shows that 40 varying the gyration rate from 10 to 20 to 30 gyrations per minute has no effect on the final dry density when all other variables are held constant. Additionally, findings showed that the number of gyrations has a significant impact on the final dry density of the sample as was concluded from the previous study; more gyrations result in higher densities. Additionally, at low gyration numbers, the gyration angle has a significant impact on the densification, but this impact diminishes as the gyration count increases. In the 2003 study, an increase in vertical pressure did not have a major influence on the final dry density (Ping,et al. , 2003). Nsaif (2012) used the SGC to estimate the maximum dry density and optimum moisture content of two types of cohesive soil classified according to AASHTO system as silty soil (A-4) and clayey soil (A-7-6). The results were compared to standard, modified Proctor and dry field density. The effect of confinement pressure, number of gyrations and moisture content were also studied. Results of using Gyratory compactor showed convergent values to those obtained using standard and modified Proctor tests. It was found that the max dry density of silty soil (A-4) is lower by (2.07%) and higher by (1.35%) than that obtained of using standard proctor test at (200 kPa) and (600 kPa) respectively, while the maximum dry density of clayey soil (A-7-6) is lower by (1.2%) than that obtained by standard proctor test at (300 kPa). The idea of testing cohesionless and cohesive soils by use of an SGC is developing more interest as years pass. Standard testing procedures like the Standard Proctor and Modified Proctor testing methods have been available since the 1930’s and are now becoming obsolete. The Proctor tests define what is often http://www.iaeme.com/IJCIET/index.asp
467
[email protected]
Effect of Fine Material on Compaction Characteristics of Subbase Material Using the Superpave Gyratory Compactor
considered the maximum theoretical dry densities for soils to be achieved by construction. However, recent improvements in the size, technology, and capabilities of construction equipment have made it possible to reach greater densities in the field than these tests are capable of producing in the lab. For this reason, there is much interest in the possibility of using the SGC to test soil samples in the lab to determine OMC and Maximum Dry Density, as well as the potential to simulate the life cycle of these soils in an accelerated manner. The SGC is being explored as a means to more closely simulate the actual compaction process used in the field during construction due to its gyratory action. The main objectives of the present study is studying the effect of increasing fine material on compaction characteristics and CBR and effects of moisture content and migration of moisture on the densification of the subbase material using the Superpave Gyratory Compactor. In this paper, the pressure and angle of gyration are kept constant with changing the number of gyrations to (50, 100 and 200) gyrations.
2. EXPERIMENTAL WORK 2.1. Subbase Used The subbase course is the layer of material under the base course. The use of two different granular materials is more economic instead of using the more expensive base course material for the entire layer, cheaper and local materials can be used as a subbase course on top of the subgrade. The surveys showed that the subbase serves as a filter between the subgrade and the base course, if the base course is open graded (Huang, 2004). Mechanical sieve analyses were carried out to determine the grading of subbase material shown in Table 1 and Figure 1 according to the limits of the Iraqi specification requirements for gradation of subbase (R6). The subbase is brought from Badra area, east of Wasit governorate east of Baghdad city capital of Iraq. Type (B) is used in this research, with three percentages of fine (Passing sieve No. 200) ,(5, 10 and 13)%. A mass of (3000 g) of subbase is loosely placed in one lift into the gyratory mold of 150 mm internal diameter. Table 1 Limits of Iraqi specification requirements for gradation of subbase (SoRB, 2003 - R6). Seive size (mm)
Iraq specification passing Type B
Subbase 1 passing%
Subbase 2 Passing%
Subbase 3 passing%
75
-
-
-
-
50
100
100
100
100
25
75-95
81
81
81
9.5
40-75
48
48
48
4.75
30-60
35
35
35
2.36
21-47
28
28
28
0.3
14-28
25
25
25
0.075
5-15
5
10
13
http://www.iaeme.com/IJCIET/index.asp
468
[email protected]
seive size (mm)
Mohammed Y. Fattah, Miami M. Hilal and Huda B. Flyeh
110 100 90 80 70 60 50 40 30 20 10 0
Minimum Maximum Gradation 0
10
20
30
40
50
60
70
80
%passing
Figure 1 Gradation curves of subbase material with specification of SORB (2003).
The course in the asphalt pavement structure immediately below the base course is the subbase. If the subgrade soil is of adequate quality, it may serve as the subbase (Asphalt Paving Design guide, 2014). The subbase sample was subjected to routine laboratory tests to determine its properties. The tests included, sieve analysis, dry unit weight, California bearing ratio with compaction to 95% of the maximum dry density, and specific gravity for three percentage of fine material (passing sieve No. 200) , according to the specification of the State Organization of Roads and Bridges, Standard Specification for Roads and Bridges (SORB, 2003), Table 2 presents the physical properties of subbase material with the corresponding specification. The dry material was thoroughly mixed with water and compacted in the SGC with a vertical pressure of 600 kPa. During preliminary testing, the specimens were subjected to 50 gyrations. Later, it was decided to increase the gyrations to 100 and 200 in order to input more energy and achieve higher densities. Durig compaction the longitudinal axis of the mold is gyrated at a fixed angle from the vertical axis while the top and bottom platens are kept parallel and horizontal. The samples are compacted at optimum water content and optimum +0.5 % , then the samples are tested to determine the CBR. Table 2 Physical properties of subbase Laboratory test
ASTM Designation
California bearing ratio (CBR)
Test results 5 % fines
10 % fines
13 % fines
D1883-05
39 %
45 %
48 %
Optimum moisture content (O.M.C)
D1557 – 12
5.4
5.8
6
Specific gravity
D-854-14
2.356
2.586
2.715
Atterberg Limits a . liquid limit (L.L) b. Plastic limit (P.L)
D 4318-10
a. 34 b. 17
Salinity a. Gypsum b. SO3
B.S.I 1377, part 3
a. 0.00299 b. 0.00139
http://www.iaeme.com/IJCIET/index.asp
469
[email protected]
Effect of Fine Material on Compaction Characteristics of Subbase Material Using the Superpave Gyratory Compactor
2.2. CBR Tests The California Bearing Ratio CBR tests were conducted after the specimens of (3000 g) were compacted using Superpave gyratory compactor, this is done by using a special mold of 150 mm diameter and 80 mm in height proportionate with the specimen volume as shown in Figure 2, while, Figure 3 shows the samples after compacted and tested in CBR.
Figure 2 Special mold for sample preparation
Figure 3 Subbase specimens after compaction and CBR test
2.3. Testing Results 2.3.1. Compaction Curve Before SGC tests were run on material, modified Proctor tests (ASTM D-1557) were performed on it to obtain the optimum moisture content and maximum modified Proctor density. However, 56 blows per layer and a larger mold, 23.76 cm3 in volume were used due to the larger aggregate size. The water content – dry density relations are drawn as shown in Figures 4 to 6 from which the optimum water content and
http://www.iaeme.com/IJCIET/index.asp
470
[email protected]
Mohammed Y. Fattah, Miami M. Hilal and Huda B. Flyeh
maximum dry density were obtained. Table 3 shows the optimum water content value for subbase materials with different percents of fines. Table 3 Optimum water content for subbase materials with different percents of fines (Passing sieve No. 200). Optimum water content % for
Maximum dry density (g/cm3)
5% fines
Optimum water content % for
Optimum water content % for
Maximum dry density (g/cm3)
13% fines
10% fines
Maximum dry density (g/cm3)
2.197
3.5
2.305045
4.5
2.314
4.4
2.2321
4.5
2.382367
5.5
2.380
5.6
2.245
5.5
2.371523
6
2.366
7.1
2.188
6.5
2.33852
6.5
2.345
Dry density (Kg/m3)
3.4
2.42 2.4 2.38 2.36 2.34 2.32 2.3 2.28 2.26 2.24 2.22 2.2 2.18 2.16
density zero air voids
0
1
2
Zero air
3
4
5
6
7
8
% Water content
Dry density (Kg/m3)
Figure 4 Water content – density relationship for subbase material with 5% fines. 2.4 2.38 2.36 2.34 2.32 2.3 2.28 2.26 2.24 2.22 2.2 2.18
density zero air voids Zero air
0
1
2
3
4
5
6
7
% Water content
Figure 5 Water content – density relationship for subbase material with 10% fines.
http://www.iaeme.com/IJCIET/index.asp
471
[email protected]
Effect of Fine Material on Compaction Characteristics of Subbase Material Using the Superpave Gyratory Compactor 2.36
Dry density (Kg/m3)
2.34
Z
2.32
density
2.3
zero air voids
2.28 2.26 2.24 2.22 2.2 2.18 0
1
2
3
4
5
6
7
% Water content
Figure 6 Water content – density relationship for subbase material with 13% fines
2.3.2. Compaction Using Gyratory Compactor Compaction curves can tell a lot about the behavior of a material during a test. Compaction curves for each of the materials at 50,100, and 200 gyrations are shown in Figures 7 to 12 for subbase material prepared at the optimum moisture content and optimum moisture content + 0.5%. It is clear that the dry density increases with the increase of the number of gyrations. It can be concluded that the higher the number of gyrations, the higher the dry density that can be achieved. Furthermore, the dry density increases with increase in percent of fines as shown in Figures 13 and 14. The CBR is affected significantly by the increase of dry density due to interlocking between particles. The CBR increases when the percentage of fines increases because the fine particles interlock the voids between large particles. Figure 15 illustrates the behavior of CBR with different percents of fines. Another factor that affect the value of CBR is the water content. The maximum CBR value can be achieved at optimum water content. In this paper, the samples compacted at the optimum water content and 0.5 % above the optimum to characterize the effect of that increase in water content on CBR. Figure 16 shows the CBR at the optimum +0.5% water content. The results show a decrease in CBR with increase water content due to replacing the soil particles by the water particles. 2300
Dry density (g/cm3)
2200 2100 2000 1900
50 gyrations 100 gyrations
1800
200 gyrations 1700 0
50
100 Number of gyrations
150
200
Figure 7 Dry density for subbase material with 5% fines (passing sieve No. 200) prepared at optimum water content.
http://www.iaeme.com/IJCIET/index.asp
472
[email protected]
Mohammed Y. Fattah, Miami M. Hilal and Huda B. Flyeh 2250 2200 Dry density (g/cm3)
2150 2100 2050 2000 50 gyrations
1950
100 gyrations
1900
200 gyrations 1850 1800 0
20
40
60
80 100 120 Number of gyrations
140
160
180
200
Figure 8 Dry density for subbase material with 5% fines (passing sieve No. 200) prepared at optimum water content +0.5%. 2400
Dry density (g/cm3)
2300 2200 2100 2000 1900
50 gyrations 100 gyrations
1800
200 gyrations 1700 0
20
40
60
80 100 120 Number of gyrations
140
160
180
200
Figure 9 Dry density for subbase material with 10% fines (passing sieve No. 200) prepared at optimum water content. 2300
Dry density (g/cm3)
2200 2100 2000 1900 1800 50 gyrations 1700
100 gyrations
1600
200 gyrations
1500 0
20
40
60 Number of gyrations
80
100
120
Figure 10 Dry density for subbase material with 10% fines (passing sieve No. 200) prepared at optimum water content +0.5%.
http://www.iaeme.com/IJCIET/index.asp
473
[email protected]
Effect of Fine Material on Compaction Characteristics of Subbase Material Using the Superpave Gyratory Compactor 2400
Dry density (g/cm3)
2300 2200 2100 2000 50 gyrations
1900
100 gyrations
1800
200 gyrations
1700 0
20
40
60
80 100 120 Number of gyrations
140
160
180
200
Figure 11: Dry density for subbase material with 13% fines (passing sieve No. 200) prepared at optimum water content. 2300
Dry density(g/cm3)
2200 2100 2000 1900
50 gyrations 100 gyrations
1800
200 gyrations
1700 0
20
40
60
80 100 120 Number of gyrations
140
160
180
200
Figure 12 Dry density for subbase material with 13% fines (passing sieve No.200) prepared at optimum water content +0.5%. 5 % fines
2300
10 % fines
13 % fines
Dry density (g/cm3)
2280 2260 2240 2220 2200 2180 2160 2140 50
100 Number of gyrations
200
Figure 13 Effect of percent of fine material on dry density for subbase material compacted at optimum water content.
http://www.iaeme.com/IJCIET/index.asp
474
[email protected]
Mohammed Y. Fattah, Miami M. Hilal and Huda B. Flyeh
5 % fines
10 % fines
13 % fines
2280
Dry density (g/cm3)
2260 2240 2220 2200 2180 2160 Number of gyrations200 100
50
Figure 14 Effect of percent of fine material on dry density for subbase material compacted at optimum water content +0.5%. 5 % fines
CBR ,%
100 90 80 70
10 % fines
13 % fines
60 50 40 30 20 10 0 50
100
200
Number of gyrations
Figure 15 Effect of percent of fine material on CBR for subbase material compacted at optimum water content.
50
100
200
Figure 16 Effect of percent of fine material on dry density for subbase material compacted at optimum water content + 0.5 %.
http://www.iaeme.com/IJCIET/index.asp
475
[email protected]
Effect of Fine Material on Compaction Characteristics of Subbase Material Using the Superpave Gyratory Compactor
3. CONCLUSION Based on the extensive research and studies, it is concluded that: •
The higher percent of fine materials at a certain point gives a compacted subbase material with higher densitys and higher CBR value due to better interlocking between Particales of subbase
•
The dry density increases with the increase of the number of gyrations. Furthermore, the dry density increases with increase in percent of fines. The CBR is affected significantly by the increase of dry density due to interlocking between particles. The maximum CBR value can be achieved at optimum water content.
•
REFERENCE [1]
ASTM , " Standard Test Methods for Specific Gravity of Soil Solids by Water Pycnometer ", D 854 -12, American Society for Testing and Materials.
[2]
ASTM, “Standard Test Method for CBR (California Bearing Ratio) of Laboratory-Compacted Soils”, D 1883- 05, American Society for Testing and Materials.
[3]
ASTM, “Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort”, D 1557- 12, American Society for Testing and Materials.
[4]
ASTM, “Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils”, D 431810, American Society for Testing and Materials.
[5]
Kumpel C. j.,(2013), "investigation of compaction characteristics of subbase Material using the superpave gyratory compactor" , Paper 254.
[6]
Huang, Y. H. (2004). "Pavement Analysis and Design", 2nd edition, Prentice Hall, Englewood Cliffs, New Jersey. University of Kentucky.
[7]
Minnesota Asphalt pavement Association ,2014 ,Asphalt paving design guide
[8]
Nsaif, T. S., (2012), “Evaluation of Compacted Fine Soil Density Using Superpave Gyratory Compacter", M.Sc. thesis, Al-Nahrain University, Baghdad, Iraq.
[9]
Ping, W., Yang, Z., Leonard, M., and Putcha, S., (2002), "Laboratory Simulation of Field Compaction Characteristics on Sandy Soils". Transportation Research Board 81st Annual Meeting, Washington D.C., January pp.13-17.
[10]
Ping, W., Xing, G., Leonard, M., Yang, Z., (2003), "Evaluation of Laboratory Compaction Techniques for Simulating Field Soil Compaction" (Phase II). For the Florida Department of Transportation.
[11]
General Specification for Roads and Bridges, Section R6, 2003, " Selected Granular Material-Subbase Course ", Department of Planning and Studies, Iraq Minnesota Asphalt Pavement Association , (2004) ,
[12]
Asphalt Paving Design Guide New Brighton, 2014 , MN 55112
[13]
British Standard Methods of Test for Soils for Civil Engineering Purpose, BS-1377 Part 3.
[14]
Dr. K.V.Krishna Reddy, Correlation between California Bearing Ratio and Shear Strength on Artificially Prepared Soils with Varying Plasticity Index. International Journal of Civil Engineering and Technology (IJCIET), 4(6),2013, pp.61–66.
[15]
Islam M. Abo Elnaga, Using of Finite Element in Developing a New Method for Rigid Pavement Analysis. International Journal of Civil Engineering and Technology (IJCIET), 5(5),2014, pp.69–75.
http://www.iaeme.com/IJCIET/index.asp
476
[email protected]
