Assessment of Field Compaction of Aggregate Base Materials ... - MDPI

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Assessment of Field Compaction of Aggregate Base Materials for Permeable Pavements Based on Plate Load Tests Yong-Jin Choi, Donghyun Ahn, Tan Hung Nguyen and Jaehun Ahn * Department of Civil and Environmental Engineering, Pusan National University, Busan 46241, Korea; [email protected] (Y.-J.C.); [email protected] (D.A.); [email protected] (T.H.N.) * Correspondence: [email protected]; Tel.: +82-10-510-7650 Received: 27 September 2018; Accepted: 16 October 2018; Published: 22 October 2018







Abstract: The permeable pavement is one of Low Impact Development technics that allows stormwater to infiltrate through the pavement surface and the underlying base layer, thereby reducing surface runoff and preventing water contamination. For permeable base layers of permeable pavements, open-graded aggregates are often used to infiltrate and store stormwater in the pore of aggregate base layers. The mechanical behavior of open-graded aggregates has not been a major interest of pavement industry and society, and therefore there is much less information known for behavior of compacted open-graded aggregates comparing to dense-graded materials. This study aims at investigating the mechanical behavior of compacted permeable or open-graded aggregate base materials based on field experiments. Five different open-graded aggregates were selected, and they were compacted in the field up to 12 passes with a 10-ton vibratory compaction roller. The mechanical behaviors of aggregates were evaluated by conducting plate load tests at 2, 4, 8, and 12 passes of roller. For the test conditions considered herein, the strain modulus at the first loading seems to provide more consistent results with respect to aggregate types and level of compaction than other stiffness measures from plate load tests. Keywords: permeable pavement; low impact development; open-graded aggregate; field test; plate load test

1. Introduction Increase in impervious areas due to urbanization has adversely affected the hydrologic cycle by reducing stormwater infiltration, increasing river peak flows, reducing groundwater baseflow, and increasing urban pollutant inflows into rivers [1,2]. The permeable pavements, one of most widely used Low Impact Development (LID) technics, is considered as an approach to solving this problem [3]. Unlike conventional impervious pavements, permeable pavements have pores that allow stormwater to infiltrate through the pavement surface and the underlying base layer, thereby reducing surface runoff and preventing water contamination [2]. For road pavements, compaction is a key process during construction because it directly affects the stability and durability of the pavement aggregate bases [4]. Therefore, proper compaction quality control (QC) is essential to achieving adequate engineering performance. In permeable pavements, for stormwater infiltration and retention, the base layer is composed of open-graded aggregates with even particle size distributions and large voids between particles unlike conventional (dense-graded) aggregate base materials. Despite the wide application of permeable pavements, reasonable specifications or standards for compaction QC of open-graded aggregate materials do not seem well established. Generally, the compaction quality of pavement base layers is assessed by density in terms of relative compaction, which is defined as the ratio of the field dry density to Sustainability 2018, 10, 3817; doi:10.3390/su10103817

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terms of relative compaction, which is defined as the ratio of the field dry density to the maximum dry [5]. dry Thedensity characteristics of characteristics these aggregates different from are those of conventional base the density maximum [5]. The of are these aggregates different from those of conventional materials, it isthe difficult to define the maximum dry density andconventional field density materials, andbase it is difficult to and define maximum dry density and field density using test methods [6–10].test methods [6–10]. using conventional With With the recent recent adoption adoption of of the the mechanistic-empirical mechanistic-empirical pavement pavement design design (MEPDG) (MEPDG) method, method, there there have increasing efforts effortstotomonitor monitorcompaction compactionquality quality evaluating stiffness or strength of have been increasing byby evaluating thethe stiffness or strength of the the compacted [4,11,12]. Modulus-based compaction QC directly measures the modulus, rather compacted soil soil [4,11,12]. Modulus-based compaction QC directly measures the modulus, rather than than the density, the on-site compacted fill. The measured modulus the advantage being the density, of theof on-site compacted fill. The measured modulus has thehas advantage of beingofdirectly directly related to structural performance and design parameters. Various tests and for related to structural performance and design parameters. Various tests and devices fordevices measuring measuring modulus have been and developed and are in use, including the plate load test (PLT) modulus have been developed are currently incurrently use, including the plate load test (PLT) [13,14], light [13,14], light weight deflectometer (LWD) [15], soil (SSG) stiffness (SSG) [16], dynamic cone weight deflectometer (LWD) [15], soil stiffness gauge [16],gauge and dynamic coneand penetrometer [17]. penetrometer Several studies using these and conducted devices have also been conducted Several related[17]. studies usingrelated these tests and devices have tests also been [4,5,12,18–27]. With these [4,5,12,18–27]. With theseConcrete trends, the Interlocking Concrete Pavement Institution (ICPI) [1] and the trends, the Interlocking Pavement Institution (ICPI) [1] and the American Society of Civil American Society [28] of Civil (ASCE) [28] have recommended assessing the compaction Engineers (ASCE) have Engineers recommended assessing the compaction quality of permeable base layers quality of permeable using devices such as thethere LWDare andnoSSG. However, since modulus there are using devices such asbase the layers LWD and SSG. However, since standards or target no standards or target modulus values itfor proper compaction, is difficult incompaction practice to values for assuring proper compaction, is assuring difficult in practice to evaluateitthe quality of evaluate thethese quality of compaction evenMetropolitan when these City devices used. Seoul Metropolitan City [29], even when devices are used. Seoul [29],are ICPI [1], and ASCE [28] have suggested ICPI [1], and ASCE have suggested specifications based on the number of a to vibratory specifications based [28] on the number of passes of a vibratory compaction roller, of butpasses it is hard find the compaction roller, it is hard to afind the basis published for selecting such a number. basis published forbut selecting such number. Given challenges of of using usingdensity-based density-basedcompaction compactionQC, QC,assessing assessingthe the compaction quality Given the challenges compaction quality of of pavement base layers modulus-based methods provide a valid alternative. However, pavement base layers by by modulus-based methods can can provide a valid alternative. However, therethere have have beenstudies few studies attempting to elucidate the compaction characteristics of permeable base been few attempting to elucidate the compaction characteristics of permeable base materials materials the values modulus proper quality control. The mainofobjective of is this study is to using the using modulus for values properfor quality control. The main objective this study to investigate investigate and understand the mechanical of open-graded aggregates in the field based on and understand the mechanical behavior ofbehavior open-graded aggregates in the field based on PLT, which PLT, which can provideinput a valuable input in establishing the methods and specifications for QC of can provide a valuable in establishing the methods and specifications for QC of permeable permeable aggregate bases. aggregate bases.

2. Permeable Permeable Base Base and and Compaction Compaction Quality Quality Control 2. 2.1. Permeable Permeable Base Base and and Open-Graded Open-Graded Aggregates Aggregates 2.1. The base base of of aa road road pavement, pavement, which which is is the the layer layer installed installed directly directly below below the the surface surface layer, layer, plays plays The the important important roles roles of of receiving receiving vehicular vehicular loads loads from from the the surface surface layer layer and and supporting supporting the the surface surface layer layer the itself [30]. In addition to these key functions, a permeable base should ensure adequate stormwater itself [30]. In addition to these key functions, a permeable base should ensure adequate stormwater infiltration into into the the underlying underlying pavement pavement layers. layers. Thus, Thus, unlike unlike general general base base layers layers that that are are constructed constructed infiltration with dense-graded aggregates, permeable bases use open-graded aggregates (Figure 1). In the United United with dense-graded aggregates, permeable bases use open-graded aggregates (Figure 1). In the States, ASTM No. 57 aggregates are widely adopted for permeable base (choker course) [1,28]. In Korea, States, ASTM No. 57 aggregates are widely adopted for permeable base (choker course) [1,28]. In Korea, for example, example, Seoul Seoul Metropolitan Metropolitan City City [29] [29] proposed proposed its its own own specification of open-graded aggregates for specification of open-graded aggregates bases for the permeable block pavements. Since open-graded aggregates have very uniform particle bases for the permeable block pavements. Since open-graded aggregates have very uniform particle size distributions, distributions, and and the the fraction fraction of of fine fine particles particles is is negligibly negligibly small, small, the the base base layers layers constructed constructed with with size these aggregates contain large voids among particles. Stormwater infiltrates through or is retained in these aggregates contain large voids among particles. Stormwater infiltrates through or is retained in these voids, thus satisfying the hydrologic requirements of the permeable base. these voids, thus satisfying the hydrologic requirements of the permeable base.

(a)

(b)

Figure illustration of pavement base materials; (a) Open-graded aggregates;aggregates; (b) DenseFigure 1.1.Conceptual Conceptual illustration of pavement base materials; (a) Open-graded graded aggregates.aggregates. (b) Dense-graded

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2.2. Compaction Quality Control and Permeable Base Compaction of the base layer is a significant process in the construction of permeable pavements and a key step towards achieving the desired engineering performance. Inadequate compaction of the base layer can undermine the stability and durability of the entire pavement [11]. Thus, compaction quality must be properly assessed during the construction of permeable pavements. The most common criterion for ensuring adequate road base compaction quality is the relative compaction, the ratio of the field dry density to the maximum dry density. However, conventional density-based compaction control is hard to implement for open-graded aggregate bases. During the construction of the base layer, the relative compaction of the compacted lift should meet certain target values. Typically, the maximum dry density is obtained by the Proctor compaction test [6,7] and the field dry density is measured by the techniques such as sand-cone [8], rubber balloon [9], and nuclear density gauge [10] methods. However, because the characteristics of permeable base materials, which is open-graded aggregates, are different from those of typical soils, it is difficult to measure the maximum dry density and the field dry density with these conventional test methods. First, because the particles of open-graded aggregates are very large and uniform, it is difficult to meet the specifications of the Proctor test [6,7]. Moreover, the impact hammer used in the Proctor compaction test often breaks the large particles, and thus changes the specimens [31]. Second, in the sand-cone method, the shape of the test hole cannot be maintained due to the collapse of the aggregate, and sand replacement is not valid because the sand used for filling the test hole enters the voids and pore openings [8]. The rubber balloon test is also highly challenging due to problems with maintaining the shape of the hole, and the rupturing of the rubber due to the sharp edges of the aggregate particles [5,9]. The nuclear density gauge method may also be affected by the gravel and large particles or the large voids in the permeable base, and has not been calibrated for such condition. The safety of radioactive wave is also arguable resulting in implementation and management challenges [5,10,11]. As mentioned in the introduction, modulus-based compaction QC has received increasing attention due to its merits and validity. Because the measurement of field dry density and maximum dry density of open-graded aggregates is challenging, modulus-based compaction QC can make an effective alternative method for monitoring the compaction quality of permeable base layers. However, very few studies have been conducted on the modulus-based compaction QC of permeable base layers. Although some permeable pavement specifications such as those of the ICPI [1] and ASCE [28] have suggested the use of the LWD and SSG to assess compaction quality, there are no specific target modulus values in these specifications to ensure proper compaction. In addition, the ICPI and ASCE [1,28] have proposed at least four passes of a 10-ton vibratory compaction roller as a standard for achieving proper compaction, but, the proposed standards do not elaborate the basis for this specification. There are several studies that used the PLT to evaluate the modulus of dense-graded ground materials. The results from literatures are summarized in Table 1. Examples of compaction QC specifications with target modulus values that can be assessed with the PLT are presented in Table 2. Table 1. Moduli of dense-graded ground materials evaluated by PLT 1 in literatures. Literature

Soil Type

MDD 2 (g/cm3 )

OMC 3 (%)

RC 4 (%)

MC 5 (%)

Ev1 6 (MPa)

Ev2 7 (MPa)

Wiman [27]

Fine sand subgrade Natural gravel Crushed rock aggregate Granular base

1.72 3 2.18 3 2.17 3 2.35 3

14.4 3 3.7 3 4.7 3 4.5 3

99–101 99.7 99.8 95.8

5.3–9.9 2.4 2.7 2.2

35–36 65 61 77.6

97–107 190 185 191

Kim and Park [18]

Poorly graded gravel

2.27

-

-

5.9

23–53

48–137

Kim et al. [32]

Silty sand Lean clay

-

-

-

-

11~15 12~23

21~28 18~37

1

Plate load test; 2 Maximum dry density from the standard Proctor test; 3 Optimum moisture content from the standard Proctor test; 4 Relative compaction; 5 Moisture content when PLT is conducted; 6 Strain modulus for first loading cycle; 7 Strain modulus for second loading cycle.

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Table 2. Table 2. Modulus-based Modulus-based compaction compaction specifications. specifications. Literature Literature ZTVE-StB ZTVE-StB 94 [33]94 [33]

Country Country

Requirement Requirement

Material Material

1 GT GW, GI,GT GU, GW, GI, GU, Germany Germany -

Standard specification for Standard specification for Korea Korea road construction [34] [34] road construction

Ev2 (MPa) Ev2 (MPa)

v1 /Ev1 EEv2v2/E

≥70 ≥70 -

-≤ 2.5 ≤2.5

1

Subbase Subbase

-

Corresponding Corresponding RC (%) RC (%) k2.5 (MPa/m) k2.5 (MPa/m) - ≥98 ≥98 - - ≥2294 2 ≥294

--

-

≥95 ≥95

11

2 Modulus 2 Modulus German soil according to DIN 18196 [35]; [35]; of subgrade reaction defineddefined at 2.5-mm German soilclassification classification according to DIN 18196 of subgrade reaction at settlement using a 30-cm loading plate.

2.5-mm settlement using a 30-cm loading plate.

3. 3. Field Field Test Test 3.1. Test Materials 3.1. Test Materials Three types of open-graded aggregates were used in the construction of the permeable base test Three types of open-graded aggregates were used in the construction of the permeable base test bed; the maximum particle sizes of these aggregates were 40 mm (D40), 25 mm (D25), and 13 mm bed; the maximum particle sizes of these aggregates were 40 mm (D40), 25 mm (D25), and 13 mm (D13), as they are presented in Figure 2. These rhyolite aggregates were brought to the field in air-dried (D13), as they are presented in Figure 2. These rhyolite aggregates were brought to the field in aircondition two days before the test started. Two additional aggregates, “D40 + D25” and “D25 + D13”, dried condition two days before the test started. Two additional aggregates, “D40 + D25” and “D25 were prepared by mixing their component aggregates in equal proportions by volume. The mixing + D13”, were prepared by mixing their component aggregates in equal proportions by volume. The was conducted by a backhoe excavator, and the volumes of the aggregates were approximated by the mixing was conducted by a backhoe excavator, and the volumes of the aggregates were excavator bucket. The volumetric compositions, basic properties, and particle size distributions of the approximated by the excavator bucket. The volumetric compositions, basic properties, and particle five open-graded aggregate test materials are presented in Table 3 and Figure 3. Figure 3 also presents size distributions of the five open-graded aggregate test materials are presented in Table 3 and Figure the lower and upper bounds of particle size distribution of two specifications, the ASTM No. 57 and 3. Figure 3 also presents the lower and upper bounds of particle size distribution of two specifications, Seoul Metropolitan City [29]. The particle size distribution of D40+D25 was comparable to ASTM No. the ASTM No. 57 and Seoul Metropolitan City [29]. The particle size distribution of D40+D25 was 57 (the material for choker layer in ICPI [1] and ASCE [28]) and specification of Seoul Metropolitan comparable to ASTM No. 57 (the material for choker layer in ICPI [1] and ASCE [28]) and specification City [29]. of Seoul Metropolitan City [29].

(a)

(b)

(c)

used to construct construct the test bed. The maximum particle Figure 2. Three types of open-graded aggregates aggregates used mm (D13). (D13). sizes are: (a) 40 mm (D40); (b) 25 mm (D25); (c) 13 mm Table 3. Basic information of the test materials. Table 3. Basic information of the test materials. Test Material Test Material Lithology Lithology

D40 D40 D40 + D25 D40 + D25 D25 D25 D25 + D13 D25 + D13 D13 D13

Rhyolite Rhyolite

Material byby Volume MaterialComposition Composition Volume D40 D40

D25 D25

D13 D13

100% 100% 50% 50% - -

- 50% 50% 100% 100% 50% 50% -

---50% 50% 100%

1 1

-

-

100%

CCuu1

1

2.88 2.88 2.99 2.99 2.48 2.48 2.84 2.84 2.79 2.79

2

Specific GravityAbrasion Abrasion Rate Cc 2Cc Specific Gravity Rate (%)(%)

1.191.19 1.081.08 1.021.02 1.16 1.16 1.16 1.16

2.67–2.75 2.67–2.75

Coefficient of uniformity; 2 Coefficient of curvature.

Coefficient of uniformity; 2 Coefficient of curvature.

12.812.8 9.8 9.8 10.310.3 11.2 11.2 12.3 12.3

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100

D40 D40+D25 D25 D25+D13 D13 ASTM No. 57 Seoul Metropolitan City [29]

Passing by weight (%)

90 80 70 60 50 40 30 20 10 0 100

10

1

0.1

Particle size (mm) Figure 3. Particle size distribution of test materials and specifications. Figure 3. Particle size distribution of test materials and specifications.

3.2. Test Program 3.2. Test Program The test program in this study (Table 4) was set for each aggregate material. A 30-cm lift (first Thelaid testand program in this (Table was set for eachcompaction aggregate material. A 30-cm lift) was compacted bystudy 12 passes of a4)10-ton vibratory roller. After 2, 4, 8,lift and(first 12 lift) was laid and compacted by 12 passes ofon a 10-ton vibratory compaction roller. After 4, 8, and 12 passes, two (duplicate) PLTs were performed each compacted aggregate. Another 30-cm2,lift (second passes, two on (duplicate) PLTs performed on each and compacted aggregate. lift) was laid the first lift, andwere the previous compaction PLT sequences wereAnother repeated.30-cm Thus,lift a (second was the first lift, and the previous PLTwere sequences wereFrom repeated. total of 80lift) cases oflaid PLTon (5 materials, 2 lifts, 4 numbers ofcompaction passes, and and 2 tests) performed. the Thus, a totalthe of strain 80 cases of PLTfor (5the materials, 2 lifts, 4 numbers passes, were performed. PLT results, moduli first and second loading of cycles (Ev1and and2 Etests) and v2 , respectively) From the PLT results, the strain moduli for the first and second loading cycles the modulus of subgrade reaction (defined at 2.5 mm of settlement; k2.5 ) were obtained. (Ev1 and Ev2, respectively) and the modulus of subgrade reaction (defined at 2.5 mm of settlement; k2.5) were Table 4. Test program. obtained. Test Materials D40 D40 +Test D25Materials D25 D40 D40 + D25 D25 + D13 D13 D25 D25 + D13 D13

Lift Number of Roller Passes Table 4. Test program. Lift

First (30 cm) Second (30 cm)

First (30 cm) Second (30 cm)

2 Number of Roller Passes 2 4 8 12

4 8 12

3.3. Test Bed Construction and Test Procedure 3.3. The Test test Bed Construction and Test Procedure bed was constructed at a site on the Yangsan campus of Pusan National University in SouthThe Korea. the site was excavated shown in Figure 4. The of overall dimensions of thein test First, bed was constructed at a siteason the Yangsan campus Pusanplan National University excavated area were 3.7 × 20 m with a trapezoidal vertical cross-section, except the excavation South Korea. First, the site was excavated as shown in Figure 4. The overall plan dimensions offor the ramp needed forwere the entry and testing equipment. Afterexcept excavation, the test bed excavated area 3.7 ×of20the m construction with a trapezoidal vertical cross-section, the excavation for was divided using rubberand partitions to isolate each test material (Figure ramp neededinto for the the five entrysections of the construction testing equipment. After excavation, the test 5a). bed The ofinto the the lift five (30 cm) wasusing guided by the rubber to partitions thattest hasmaterial the same height with washeight divided sections rubber partitions isolate each (Figure 5a). The the lift. of The unloaded aggregates werebyevenly spread with thethat bucket excavator to level height the lift (30 cm) was guided the rubber partitions has of thethe same height with thethe lift. surface (Figure 5b). Thereafter, a 10-ton rollerthe (Dynapac) was used to compact the aggregates The unloaded aggregates were evenlyvibratory spread with bucket of the excavator to level the surface (Figure roller operated along the longitudinal direction of used the test Afterthe theaggregates specified (Figure5c). 5b).The Thereafter, a 10-ton vibratory roller (Dynapac) was to bed. compact number roller (Table 4),along the PLTs were performed for each testtest material to determine the (Figure of 5c). The passes roller operated the longitudinal direction of the bed. After the specified modulus of the compacted lift (Figure 5d). After the tests on the first lift were completed, the second number roller passes (Table 4), the PLTs were performed for each test material to determine the lift was laid of the first and the compaction and on PLTthe procedures werecompleted, repeated. the second modulus ofon thetop compacted liftlift, (Figure 5d). After the tests first lift were lift was laid on top of the first lift, and the compaction and PLT procedures were repeated.

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(a)

(b) Figure Figure 4. 4. Test Test bed bed layout: layout: (a) (a) Cross-sectional Cross-sectional view; view; (b) (b) Plan Plan view. view.

(a)

(b)

(c)

(d)

Figure Test bed bed construction construction and and test test procedure: procedure: (a) (a) Test Test bed excavation excavation and and test test section section separation; Figure 5. 5. Test Test bed sectionseparation; separation; (b) Lift construction; (c) Compaction; (d) PLT. (b) Lift Lift construction; construction; (c) (c) Compaction; Compaction; (d) (d) PLT. PLT.

The accordance with DIN 18134 18134 [14] [14] with with some somemodifications modifications considering considering The PLT PLT was was carried carried out out in in accordance with DIN prevailing field fieldconditions. conditions.InIn the loading process, a loading plate a diameter 30was cm the prevailing the loading process, a loading plate withwith a diameter of 30ofcm was used without applying seating because the surface of aggregates compaction used without applying seating sandsand because the surface of aggregates rightright after after compaction was was very flat. excavator The excavator was used to deliver the reaction The normal the very flat. The was used to deliver the reaction force.force. The normal stressstress actingacting on theon plate platemeasured was measured by reading hydraulic pressure acting hydraulicjack jackwith withthe the pressure was by reading the the hydraulic pressure acting onon thethe hydraulic measurement dial thethe testtest began, a preloading stressstress (~0.01(~0.01 MPa) MPa) was applied for proper measurement dialgauge. gauge.Before Before began, a preloading was applied for seating seating of the plate, the and displacement measurement dial gauge set to zero. The loading proper of theand plate, the displacement measurement dialwas gauge was set to zero. The cycle (first loading was applied eight approximately equally spaced upstages to theup planned loading cycle (first cycle) loading cycle) was in applied in eight approximately equallystages spaced to the maximum stress (~0.5 MPa); then, the load was reduced to 50% and 25% of the maximum stress planned maximum stress (~0.5 MPa); then, the load was reduced to 50% and 25% of the maximum successively, and finally to back the preloading stress. The reloading cycle (second loading cycle) was stress successively, and back finally to the preloading stress. The reloading cycle (second loading cycle) was the same as the first loading cycle, but the last loading stage (the 8th stage) was not applied following the DIN 18134 [14]. The magnitude of preloading and maximum stresses varied slightly

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the same as the first loading cycle, but the last loading stage (the 8th stage) was not applied following Sustainability 2018, 10, x FOR PEER REVIEW 7 of 13 the DIN 18134 [14]. The magnitude of preloading and maximum stresses varied slightly among tests accommodating equipment and field conditions. The test locations offset from eachfrom other to among tests accommodating equipment and field conditions. The test were locations were offset each minimize interference among the PLT measurements (Figure 6). The location of PLT in each aggregate other to minimize interference among the PLT measurements (Figure 6). The location of PLT in each bed is illustrated Figure 6; the numbers 2, 4,numbers 8, and 122,represent of roller passes,of and the aggregate bed is in illustrated in Figure 6; the 4, 8, andthe 12number represent the number roller symbol “a” and “b” represent the“b” firstrepresent and second Additional also conducted onalso the passes, and the symbol “a” and the tests. first and second PLTs tests. were Additional PLTs were subgrade by the test bed. conducted on the subgrade by the test bed.

Figure 6. 6. Layout Layout of of test test locations locations on on aa test test bed bed section. section. Figure

4. Results and Discussion 4.1. 4.1. Modulus Modulus Calculation Calculation The and the strain modulus at the second v1 and the strain modulus at the second The values values of of the the strain strain modulus modulus at at the the first first loading loading EEv1 loading were calculated based on the process specified in DIN 18134 [14]. The calculation method loading EEv2 v2 were calculated based on the process specified in DIN 18134 [14]. The calculation method uses a second-order uses a second-order polynomial polynomial regression regression analysis analysis to to determine determine the the stress–settlement stress–settlement curve curve for for the the first first and and second second loading loading cycles. cycles. The The determined determined curve curve is is expressed expressed by by the the following following equation: equation: + a2 ·σ∙ 02 s= = a0 + + a1 ·∙σ0 +

(1) (1)

where is the settlement of the plate (mm), is the normal stress below the plate (MPa), , , where s is the settlement of the plate (mm), σ0 is the normal stress below the plate (MPa), a0 , a1 , and a2 and is the constant determined from second-order polynomial regression analysis (mm, is the constant determined2 from second-order polynomial regression analysis (mm, mm/MPa, and mm/MPa, and mm/(MPa) , respectively). The determined curves and constants are illustrated with mm/(MPa)2 , respectively). The determined curves and constants are illustrated with the test results the test results shown in Figure 7. In Figure 7, “a” and “b” represent the duplicate of the tests (Figure shown in Figure 7. In Figure 7, “a” and “b” represent the duplicate of the tests (Figure 6). The values 6). The values of Ev1 and Ev2 were determined from the first and second regression curves, respectively, of Ev1 and Ev2 were determined from the first and second regression curves, respectively, as follows: as follows:

11 Ev==1.5 1.5∙·r ·∙ a1 ++a2 ·σ∙0max

(2) (2)

where Ev isisthe the strain modulus (MPa), is radius the radius the plate is the maximum where strain modulus (MPa), r is the of theofplate (mm),(mm), σ0max is the maximum normal normal stressthe below plate (MPa). stress below platethe (MPa). 2.5), the For the thecalculation calculation modulus of subgrade reaction at 2.5-mm displacement For of of thethe modulus of subgrade reaction at 2.5-mm displacement (k2.5 ), the(kaverage average slope between the displacement 0 and the regression curve theloading first loading slope between the displacement of 0 andof2.5 mm2.5 onmm the on regression curve of the of first cycle cycle (Figure was used. The following is the equation for calculating (Figure 7) was7)used. The following is the equation for calculating k2.5 : k2.5: ∆ ∆σ0 (3) k2.5. == (3) s where ∆ is the difference between the preloading stress and the stress corresponding to 2.5-mm where ∆σ0 is the difference between the preloading stress and the stress corresponding to 2.5-mm displacement and is the displacement (therefore, 2.5 mm or 0.0025 m). displacement and s is the displacement (therefore, 2.5 mm or 0.0025 m).

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0

0

a - 1st loading cycle a – 2nd loading cycle b - 1st loading cycle b – 2nd loading cycle

2

2

y = −7.99 x2 + 20.48 x − 0.37

4

y = −7.65

6

x2

+ 21.62 x − 0.86

y = 1.22 x2 + 1.30 x + 8.21

8 y = 1.11 x2 + 1.05 x + 8.47

10 0.0

0.1

0.2

0.3

a - 1st loading cycle a – 2nd loading cycle b - 1st loading cycle b – 2nd loading cycle

k2.5 at a

Settlement, s (mm)

k2.5 at a

Settlement, s (mm)

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y = −9.55 x2 + 17.29 x − 0.80

4 y = −8.77 x2 + 17.92 x − 0.85

6 y = 1.28 x2 + 1.08 x + 5.91

8

y = 1.34 x2 + 0.97 x + 5.39

10 0.4

0.5

0.6

0.7

Normal stress, σ0 (MPa)

(a)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Normal stress, σ0 (MPa)

(b)

Figure 7. Examples Examples of of stress-settlement stress-settlement curves curves in in the first lift: (a) (a) D25 D25 at locations locations “a” “a” and “b” “b” after 4 roller passes; (b) D25 at locations “a” and “b” after 12 roller passes.

4.2. Relationship Relationship Between Between Roller Roller Pass Pass and and Modulus Modulus 4.2. Figure 88 summarizes , k 2.5 and and E /E for the successive roller passes at Figure summarizes the the changes changes in inEEv1v1,, EEv2 Ev1 v2, k2.5 v1/Ev2v2for the successive roller passes at which the PLTs were conducted. Each point in Figure 8 is the average of of two two test test results results (duplicate). (duplicate). which the PLTs were conducted. Each point in Figure 8 is the average The values of E , E , and k steeply increase up to four roller passes for most of the test materials v2, and k2.5 2.5steeply increase up to four roller passes for most of the test materials The values of Ev1 v1, Ev2 and lifts. lifts. It It is is clear clear that that E Ev1 keepsincreasing increasingas asthe thenumber number of of passes passes raises raises after after four four passes passes but but with with v1keeps and declined trends. E and k seem to somewhat reflect the change in materials with increasing number v2 declined trends. Ev2 and k2.52.5seem to somewhat reflect the change in materials with increasing number of passes, passes, but butthey theyare arenot notas assensitive sensitiveororconsistent consistenttotothe thenumber number passes is noted of ofof passes asas Ev1E. v1 It .isItnoted thatthat Ev2 Ev2the is the strain modulus during reloading process and thematerial materialmay maybe becompressed compressed and and become become is strain modulus during reloading process and the denser during during the the first first loading loading cycle, the consequence of the first loading rather than the denser cycle, making making E Ev2 v2 the consequence of the first loading rather than the measure of of roller roller compaction. isthe the stiffness stiffness measure measure of of the the aggregate aggregate at at relative relative smaller smaller strain strain 2.5is measure compaction. kk2.5 level than E , so that the effect of increased compaction level on highly nonlinear material may not v1 level than Ev1, so that the effect of increased compaction level on highly nonlinear material may not be captured well by k . From Figure 8a–c, it can be found that the minimum of four roller passes 2.5. From Figure 8a–c, it can be found that the minimum of four roller passes be captured well by k2.5 recommended by the ICPI and and ASCE ASCE [1,28] [1,28] is is an an efficient efficient one, one, but but one one can can expect expect hardening hardening of of the the recommended by the ICPI open-graded materials for larger number of roller passes than four. open-graded materials for larger number of roller passes than four. The underlying underlying subgrade 2.5 The subgrade layer layer could could affect affectthe theresults resultsof ofPLTs, PLTs,and andthe thevalues valuesofofEv1 Ev1, ,EEv2v2 and and kk2.5 of subgrade were 69 MPa, 196 MPa, and 143 MPa/m, higher than those of all open-graded aggregates. of subgrade were 69 MPa, 196 MPa, and 143 MPa/m, higher than those of all open-graded aggregates. Because the higher stiffness thanthan the permeable base layers, the Ev1the values Because the subgrade subgradehas hasa considerably a considerably higher stiffness the permeable base layers, Ev1 of the first lift, built directly on the subgrade, are slightly higher than those of the second lift for most values of the first lift, built directly on the subgrade, are slightly higher than those of the second lift cases (Figure but certainly not significant. These differences are not captured by other modulus for most cases8a), (Figure 8a), but certainly not significant. These differences are not captured by other measures such as E and k . modulus measures v2 such as 2.5 Ev2 and k2.5. The strain strainmodulus modulusatatreloading reloadingcycle cycle ) showed high dependency on material the material The (E(E showed high dependency on the type.type. The v2)v2 The permeable base layers composed of large particles at the lowest compaction level, in some cases, permeable base layers composed of large particles at the lowest compaction level, in some cases, has has higher Ev2 the thansmaller the smaller particles the highest compaction level. For example, D13 12 higher Ev2 than particles at the at highest compaction level. For example, D13 with 12with passes passes showed considerably lower E than D25 with 2 passes (Figure 8b). These results indicate that v2 showed considerably lower Ev2 than D25 with 2 passes (Figure 8b). These results indicate that the the selection of materials is very important, andlevel the level of compaction not compensate the selection of materials is very important, and the of compaction does does not compensate the mismis-selection ofmaterials. the materials. selection of the When the values of E of open-graded aggregates are compared to those of conventional v1 of open-graded aggregates are compared to those of conventional When the values of Ev1 (densely-graded) ground materials in literature literature (Table (Table 1), of open-graded aggregates are smaller (densely-graded) ground materials in 1), E Ev1 v1 of open-graded aggregates are smaller than those those of of dense-graded dense-graded materials materials with with similar similar particle particle sizes sizes (gravel), (gravel), but but rather rather close close to to those those of of than dense-graded materials with smaller sizes (sand and clay). The values of E are, however, closer to v2 are, however, closer to dense-graded materials with smaller sizes (sand and clay). The values of Ev2 densely-graded gravel rather thanthan the densely-graded sand orsand clay. or As such, permanent densely-graded gravelmaterials materials rather the densely-graded clay. more As such, more deformation is expected in open-graded aggregates than in dense-graded aggregates, but the resilient permanent deformation is expected in open-graded aggregates than in dense-graded aggregates, but the resilient deformation may be similar for these materials. When they are compared to the requirements in German [32] and Korean [33] guides, all the materials tested meet the requirement

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deformation may be similar for these materials. When they are compared to the requirements in 9 of 13 German [32] and Korean [33] guides, all the materials tested meet the requirement for Ev2 but not for EEv2v2but /Ev1 and This would be partially because the current requirements are setup focusing on v1 and k2.5. This would be partially because the current requirements are setup for not fork2.5 Ev2./E dense-graded materials. For open-graded aggregates, itaggregates, will be necessary more suitable focusing on dense-graded materials. For open-graded it will to be develop necessary to develop requirements for QC. more suitable requirements for QC. Sustainability 2018, 10, x FOR PEER REVIEW

20

140 120

16 Ev2 (MPa)

Ev1 (MPa)

100

12 8 D40 (1st lift) D40+D25 (1st lift) D25 (1st lift) D25+D13 (1st lift) D13 (1st lift)

4 0 0

2

4

6

10

12

60 40

D40 (2nd lift) D40+D25 (2nd lift) D25 (2nd lift) D25+D13 (2nd lift) D13 (2nd lift)

8

80

20 0

0

14

2

Number of Roller Passes

4

(a)

12

60

10

Ev2/Ev1

80 k2.5 (MPa/m)

14

40

6

0

4 4

6

10

12

14

12

14

8

20

2

8

(b)

100

0

6

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8

10

12

Number of Roller Passes

(c)

14

0

2

4

6

8

10

Number of Roller Passes

(d)

Figure roller passes passes and andmodulus modulusmeasures: measures:(a) (a)EEv1v1;; (b) (b) EEv2 v2;; (c) Figure8. 8.Relationship Relationship between between number of roller (c) k2.5 2.5; ; v1.v1 . (d) (d) EEv2v2/E/E

4.3. Relationship RelationshipBetween BetweenMaterials Materialsand and Modulus Modulus 4.3. The results reorganized in Figure 9 to present better the differences among materials. The results in inFigure Figure8 are 8 are reorganized in Figure 9 to present better the differences among The values of E are higher for larger size of particles with a few variations (Figure The D13 v1 materials. The values of Ev1 are higher for larger size of particles with a few variations9a). (Figure 9a). sample, the smallest particles among the investigated, has the lowest values of E , E , and k for v1 v2 2.5 The D13 sample, the smallest particles among the investigated, has the lowest values of Ev1, Ev2, and most cases. The values of E are mostly within a band of 80~130 MPa. The values of k do not seem v2 2.5 k2.5 for most cases. The values of Ev2 are mostly within a band of 80~130 MPa. The values of k2.5 do not consistent, possibly because they represent the slope of stress and displacement at very range seem consistent, possibly because they represent the slope of stress and displacement atnarrow very narrow of displacement (2.5 mm). range of displacement (2.5 mm).

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20

140 120

16

Ev2 (MPa)

Ev1 (MPa)

100 12 8 4

2 pass (1st lift)

4 pass (1st lift)

8 pass (1st lift)

12 pass (1st lift)

2 pass (2nd lift) 8 pass (2nd lift)

4 pass (2nd lift) 12 pass (2nd lift)

80 60 40 20 0

0 D40

D40+D25

D25

D25+D13

D40

D13

D40+D25

Material

D25

D25+D13

D13

Material

(a)

(b)

100

14 12

80 60

Ev2/Ev1

k2.5 (MPa/m)

10

40

8 6 4

20

2 0

0 D40

D40+D25

D25

D25+D13

D13

Material

(c)

D40

D40+D25

D25

D25+D13

D13

Material

(d)

2.5; (d) Ev2 v2/E Figure9.9.Relationship Relationshipbetween betweenmaterials materialsand andmodulus modulusmeasures: measures:(a)(a) Ev1 ; (b)EE (c)kk2.5 . . Figure Ev1 ; (b) /Ev1v1 v2v2;;(c)

4.4. Variations Variations Between Between Modulus Modulus Measurements Measurements 4.4. Figure 10 the the examples of the of modulus values obtained averaging theaveraging measurements Figure 10shows shows examples the modulus values before obtained before the at two locations “a” and “b”. It can be found that E , which measures slope of stress and displacement v1 measurements at two locations “a” and “b”. It can be found that Ev1, which measures slope of stress up todisplacement the maximum more consistent results comparing k2.5 that uses smaller 2.5 that and upstress, to thepresents maximum stress, presents more consistenttoresults comparing to kportion of thesmaller stress-displacement (Figure 7). For dense-graded this gap maymaterials, be less significant; uses portion of thecurve stress-displacement curve (Figurematerials, 7). For dense-graded this gap for open-graded materials for that open-graded undergoes considerable amount of displacement, Ev1 and Ev2 give may be less significant; materials that undergoes considerable amount of more consistent results. Table 5 summarized the variations of duplicate measurements for all the tests displacement, Ev1 and Ev2 give more consistent results. Table 5 summarized the variations of duplicate conducted, andfor forall open-graded aggregates, Ev2 wouldaggregates, be a more reliable forbe QC measurements the tests conducted, andEv1 forand open-graded Ev1 andmeasure Ev2 would a than k . 2.5 more reliable measure for QC than k2.5.

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100

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80 k2.5 (MPa/m)

Ev1 (MPa)

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4

60 40 20

D13 (a)

D40+D25 (b)

D13 (b) 0

0 0

2

4 6 8 10 12 Number of Roller Passes

14

0

2

4 6 8 10 12 Number of Roller Passes

(a)

14

(b)

Figure10. 10.Examples Examplesof ofmodulus modulusmeasurements measurementsbefore beforeaveraging: averaging:(a) (a)EEv1v1 measurements measurementsat atlocation locationaa Figure 2.5 measurements andbbin inD40+D25 D40+D25of offirst firstlift; lift;(b) (b)kk2.5 measurements at at location location aa and and bb in in D13 D13 of of second second lift. lift. and Table Table5.5.Coefficients Coefficientsof ofvariation variationof ofmodulus modulusmeasures. measures. Modulus Modulus Ev1 Ev1 Ev2 Ev2 k2.5 k2.5

CoefficientofofVariation Variation (CV) Coefficient (CV) Maximum (%) Mean(%) (%) Maximum (%) Mean 16.1 5.3 16.1 5.3 22.4 4.5 22.4 4.5 40.6 10.5 40.6 10.5

5.5.Conclusions Conclusions The Themechanical mechanicalbehavior behaviorof ofopen-graded open-gradedaggregates aggregateshas hasnot notbeen beenaamajor majorinterest interestof ofpavement pavement industry industryand andsociety, society,and andtherefore thereforethere thereisisno nomuch muchinformation informationavailable availablefor forbehavior behaviorof ofcompacted compacted open-graded open-graded aggregates. aggregates. Sets of PLTs PLTs have have conducted conducted to to investigate investigate the the mechanical mechanical behavior behavior of of compacted compacted permeable permeable or or open-graded open-graded aggregates. aggregates. Based Based on on the the test test results, results, the thefollowing followingfindings findings were weremade: made:

•

•

•

•

The values valuesof ofEEv1v1,, EEv2 for most most of of the the test test v2, and k2.5 2.5 steeply The steeply increased increased up up to four roller passes for materialsand andlifts liftsconsidered consideredhere. here.EEv1v1 clearly clearly keeps keeps increasing increasing as as the the number number of ofpasses passesraises raises materials afterfour fourpasses passesbut butwith withdeclined declinedtrends. trends.The Theminimum minimumof offour fourroller rollerpasses passesrecommended recommendedby by after theICPI ICPIand andASCE ASCE[1,28] [1,28]isisefficient, efficient,but butone onecan canexpect expecthardening hardeningof ofthe theopen-graded open-gradedmaterials materials the forlarger largernumber numberof ofroller rollerpasses passesthan thanfour. four. for Thestrain strainmodulus modulusatatthe thesecond secondloading loadingcycle cycle(E(Ev2v2)) showed showed high highdependency dependencyon onthe thematerial material The type. Large Large particles particles at at the the lowest lowest compaction compaction level, level, in in some somecases, cases,had hadhigher higherEEv2v2 than than the the type. smaller particles at the highest compaction level. The selection of materials is very important, smaller particles at the highest compaction level. The selection of materials is very important, and andlevel the level of compaction not compensate the mis-selection the materials. the of compaction does does not compensate the mis-selection of theofmaterials. Foropen-graded open-gradedaggregates aggregatesthat thatundergoes undergoes large largedeformation deformation during during PLT, PLT,the thestrain strainmodulus modulus For E v1 and Ev2 measures much wider range of stress and displacement than k2.5. As such, Ev1 and Ev2 Ev1 and Ev2 measures much wider range of stress and displacement than k2.5 . As such, Ev1 and more consistent results. For open-graded aggregates, Ev1 and Ev2 would make a more Egive v2 give more consistent results. For open-graded aggregates, Ev1 and Ev2 would make a more reliable measurefor forQC QCthan thankk2.5. reliable measure 2.5 When the results are compared torequirements the requirements in German and guides, Koreanall guides, all the When the results are compared to the in German and Korean the materials materials meet the requirement v2 but not for Ev2/Ev1 and k2.5. This would be partially tested meettested the requirement for Ev2 but for not Efor Ev2 /Ev1 and k2.5 . This would be partially because because the current requirements are setup on dense-graded It will to be the current requirements are setup focusing onfocusing dense-graded materials. It materials. will be necessary necessary to develop more suitable QC requirements for the open-graded aggregate base. develop more suitable QC requirements for the open-graded aggregate base.

Author Contributions: Conceptualization and methodology Y.-J.C., D.A., and J.A.; Validation, Y.-J.C., T.H.N., D.A., and J.A.; Formal Analysis, Y.-J.C.; Investigation, Y.-J.C. and J.A.; Resources, J.A.; Data Curation, Y.-J.C.; Writing—Original Draft, Y.-J.C.; Writing—Review & Editing, J.A.; Visualization, Y.-J.C.; Supervision, J.A.; Project Administration, J.A.; Funding Acquisition, J.A.

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Author Contributions: Conceptualization and methodology Y.-J.C., D.A., and J.A.; Validation, Y.-J.C., T.H.N., D.A., and J.A.; Formal Analysis, Y.-J.C.; Investigation, Y.-J.C. and J.A.; Resources, J.A.; Data Curation, Y.-J.C.; Writing—Original Draft, Y.-J.C.; Writing—Review & Editing, J.A.; Visualization, Y.-J.C.; Supervision, J.A.; Project Administration, J.A.; Funding Acquisition, J.A. Funding: This research was supported by a grant from the Technology Advancement Research Program (grant No. 18CTAP-C132363-02) funded by the Ministry of Land, Infrastructure, and Transport of the Korean government. Acknowledgments: The authors would like to thank the Ministry of Land, Infrastructure, and Transport of Korean government for the grant from Technology Advancement Research Program (grant No. 18CTAP-C132363-02). Conflicts of Interest: The authors declare no conflict of interest.

References 1. 2. 3.

4.

5.

6. 7. 8. 9. 10.

11. 12. 13.

14. 15. 16.

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Smith, D.R. Permeable Interlocking Concrete Pavements, 4th ed.; Interlocking Concrete Pavement Istitute: Herndon, VA, USA, 2011; ISBN 978-1-4507-8440-5. Brattebo, B.O.; Booth, D.B. Long-term stormwater quantity and quality performance of permeable pavement systems. Water Res. 2003, 37, 4369–4376. [CrossRef] Kumar, K.; Kozak, J.; Hundal, L.; Cox, A.; Zhang, H.; Granato, T. In-Situ infiltration performance of different permeable pavements in a employee used parking lot—A four-year study. J. Environ. Manag. 2016, 167, 8–14. [CrossRef] [PubMed] Abu-Farsakh, M.; Alshibli, K.A.; Nazzal, M.; Seyman, E. Assessment of In-Situ Test Technology for Construction Control of Base Courses and Embankments; FHWA/LA.041389; Louisiana Transportation Research Center: Boton Rouge, LA, USA, 2004. Berney, E.S., IV; Mejias-Santiago, M.; Kyzar, J.D. Non-Nuclear Alternatives to Monitoring Moisture-Density Response in Soils; ERDC/GSL TR-13-6; U.S. Army Engineer Research and Development Center Geotechnical and Structures Laboratory: Vicksburg, MS, USA, 2013. ASTM International. Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-lbf/ft3 (2700 kN-m/m3 )); ASTM D1557; ASTM International: West Conshohocken, PA, USA, 2012. ASTM International. Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort (12,400 ft-lbf/ft3 (600 kN-m/m3 )); ASTM D698; ASTM International: West Conshohocken, PA, USA, 2012. ASTM International. Standard Test Method for Density and Unit Weight of Soil in Place by Sand-Cone Method; ASTM D1556/D1556M; ASTM International: West Conshohocken, PA, USA, 2015. ASTM International. Standard Test Method for Density and Unit Weight of Soil in Place by the Rubber Balloon Method; ASTM D2167; ASTM International: West Conshohocken, PA, USA, 2015. ASTM International. Standard Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow depth); ASTM D6938 REV A; ASTM International: West Conshohocken, PA, USA, 2017. Nazzal, M. Non-Nuclear Methods for Compaction Control of Unbound Materials; National Cooperative Highway Research Program Synthesis 456; Transportation Research Board: Washington, DC, USA, 2014. Meehan, C.L.; Tehrani, F.S.; Vahedifard, F. A comparison of density-based and modulus-based in situ test measurements for compaction control. Geotech. Test. J. 2012, 35, 387–399. [CrossRef] ASTM International. Standard Test Method for Repetitive Static Plate Load Tests of Soils and Flexible Pavement Components, for Use in Evaluation and Design of Airport and Highway Pavements; ASTM D1195/D1195M; ASTM International: West Conshohocken, PA, USA, 2009. Deutsches Institut fur Normung E.V. Soil—Testing Procedures and Testing Equipment—Plate Load Test; DIN 18134; Deutsches Institut fur Normung E.V.: Berlin, Germany, 2012. ASTM International. Standard Test Method for Measuring Deflections Using a Portable Impulse Plate Load Test Device; ASTM E2835; ASTM International: West Conshohocken, PA, USA, 2011. ASTM International. Standard Test Method for Measuring Stiffness and Apparent Modulus of Soil and Soil-Aggregate In-Place by Electro-Mechanical Method; ASTM D6758; ASTM International: West Conshohocken, PA, USA, 2018. ASTM International. Standard Test Method for Use of the Dynamic Cone Penetrometer in Shallow Pavement Applications; ASTM D6951/D6951M; ASTM International: West Conshohocken, PA, USA, 2018.

Sustainability 2018, 10, 3817

18.

19. 20. 21. 22. 23. 24. 25.

26. 27. 28. 29. 30. 31.

32. 33.

34. 35.

13 of 13

Kim, D.; Park, S. Relationship between the subgrade reaction modulus and the strain modulus obtained using a plate loading test. In Proceedings of the 9th World Congress on Railway Research, Lille, France, 22–26 May 2011. Alshibli, K.A.; Abu-Farsakh, M.; Seyman, E. Laboratory evaluation of the geogauge and light falling weight deflectometer as construction control tools. J. Mater. Civ. Eng. 2005, 17, 560–569. [CrossRef] Hufenus, R.; Rueegger, R.; Banjac, R.; Mayor, P.; Springman, S.M.; Bronnimann, R. Full-scale field tests on geosynthetic reinforced unpaved roads on soft subgrade. Geotext. Geomembr. 2006, 24, 21–37. [CrossRef] Jimenez, J.R.; Ayuso, J.; Agrela, F.; Lopez, M.; Galvin, A.P. Utilisation of unbound recycled aggregates from selected CDW in unpaved rural roads. Resour. Conserv. Recycl. 2012, 58, 88–97. [CrossRef] Sulewska, M.J. The control of soil compaction degree by means of LFWD. Balt. J. Road Bridge Eng. 2012, 7, 36–41. [CrossRef] Umashankar, B.; Hariprasad, C.; Kumar, G.T. Compaction quality control of pavement layers using LWD. J. Mater. Civ. Eng. 2016, 28. [CrossRef] Wersall, C.; Nordfelt, I.; Larsson, S. Resonant roller compaction of gravel in full-scale tests. Transp. Geotech. 2018, 14, 93–97. [CrossRef] Lenke, L.R.; McKeen, R.G.; Grush, M. Evaluation of a Mechanical Stiffness Gauge for Compaction Control of Granular Media; NM99MSC-07.2; New Mexico State Highway & Transportation Department: Albuquerque, NM, USA, 2001. Maher, A.; Bennert, T.; Gucunski, N. Evaluation of the Humboldt Stiffness Gauge; FHWA-NJ-2002-002; New Jersey Department of Transportation: Trenton, NJ, USA, 2002. Wiman, L.G. Accelerated Load Testing of Pavements: HVS-NORDIC Tests at VTI Sweden 2003–2004; VTI rapport 544A; Swedish National Road and Transport Research Institute: Linköping, Sweden, 2006. Eisenberg, B.E.; Lindow, K.C.; Smith, D.R. Permeable Pavements, 1st ed.; American Society of Civil Engineers: Reston, VA, USA, 2015; ISBN 978-0-7844-7867-7. Seoul Metropolitan City. Design, Construction and Maintenance Standards of Permeable Block Pavement; Ver. 2.0; Seoul Metropolitan City: Seoul, Korea, 2013. AASHTO. AASHTO Guide for Design of Pavement Structures; AASHTO: Washington, DC, USA, 1993; Volume 1, ISBN 1-56051-055-2. Cetin, A.; Kaya, Z.; Cetin, B.; Aydilek, A.H. Influence of laboratory compaction method on mechanical and hydraulic characteristics of unbound granular base materials. Road Mater. Pavement Des. 2014, 15, 220–235. [CrossRef] Kim, D.; Choi, C.; Kim, S.J.; Yu, J.Y.; Yang, S.C. Study on the subgrade reaction modulus (K30 ) and strain modulus (Ev ). J. Korean Soc. Railw. 2007, 10, 264–270. Research Society of Road and Traffic. Additional Technical Contractual Conditions and Guidelines for Earthwork in Road Construction and Technical Testing Instructions for Soil and Rock in Road Construction; ZTVE-StB 94; Research Society of Road and Traffic: Koln, Germnay, 1994. Ministry of Land, Infrastructure and Transport. Standard Specification for Road Construction; Ministry of Land, Infrastructure and Transport: Sejong, Korea, 2015. Deutsches Institut fur Normung E.V. Earthworks and Foundations—Soil Classification for Civil Engineering Purposes; DIN 18196; Deutsches Institut fur Normung E.V.: Berlin, Germany, 2011. © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).