geotechnical properties of waste excavation rock in ...

Journal of Materials in Civil Engineering. Submitted April 20, 2011; accepted November 3, 2011; posted ahead of print November 5, 2011. doi:10.1061/(ASCE)MT.1943-5533.0000419

GEOTECHNICAL PROPERTIES OF WASTE EXCAVATION ROCK IN PAVEMENT SUB-BASE APPLICATIONS

Ac N ce ot p C ted op M ye a di nu te s d cr ip t

A. Arulrajah1, M. M. Y. Ali2, J. Piratheepan3 and M. W. Bo4

A. Arulrajah1 Associate Professor, Swinburne University of Technology, Melbourne, VIC3122, Australia. [email protected] M. M. Younus Ali2 PhD Student, Swinburne University of Technology, Melbourne, VIC3122, Australia. [email protected] J. Piratheepan3 Lecturer, Swinburne University of Technology, Melbourne, VIC3122, Australia. [email protected]

M. W. Bo4 Senior Principal/Director, DST Consulting Engineers Inc, Thunder Bay, Ontario, P7B 5V5, Canada. [email protected]

Corresponding Author: A/Prof Arul Arulrajah Faculty of Engineering and Industrial Science (H38), Swinburne University of Technology, P.O Box 218, Hawthorn VIC 3122 Australia. Email : [email protected] Phone : +613-92145741 Fax : +613-92148264

1 Copyright 2011 by the American Society of Civil Engineers


ABSTRACT This paper presents the findings of an extensive laboratory investigation on the geotechnical properties of waste excavation rock in pavement sub-bases. The waste excavation rock used in this study originated from ―basalt floaters‖ or surface


excavation basalt rock (basalt). Traditionally this material would have been disposed as waste, often into landfill. The engineering properties of the crushed basaltic waste

rock were compared with the local road authority specifications to assess its

performance as a pavement sub-base material. The experimental programme was extensive and included tests such as particle size distribution, modified Proctor compaction, particle density, water absorption, California Bearing Ratio, Los

Angeles abrasion loss, pH, organic content, static triaxial and repeated load triaxial tests. The Los Angeles abrasion loss value obtained indicated that the crushed

basaltic waste rock is durable. California Bearing Ratio values were found to satisfy the local state road authority requirements for a lower sub-base material. Repeated load triaxial testing established that the crushed basaltic waste rock would perform

satisfactorily as a pavement sub-base material in the field. The results of the laboratory testing undertaken in this research indicated that crushed basaltic waste

excavation rock satisfied the criteria for use in pavement sub-base applications.

Keywords: geotechnical; waste rock; pavement; sub-base; repeated load triaxial;

permanent strain.



INTRODUCTION Reuse of waste materials is a topic of global concern and of great international interest. The urgent need for reuse of waste materials is driven mainly by environmental considerations, due to the increased scarcity of natural resources and


the increasing cost of land fill in most countries.

The crushed waste excavation rock used in this study originates from ―basalt floaters‖ or surface excavation rock which commonly occurs near the surface to the

west and north of Melbourne, Australia. The rock is often encountered in excavation for residential sub divisional development and in the excavation works for drainage lines as well as other subsurface infrastructure. Traditionally this material would have been disposed as waste, often into landfill. However, due to their hardness and

durability, research has been undertaken in this paper to investigate its reuse in pavement sub-base applications. In Melbourne, soils are commonly classified into nine types. Heavy clay on younger basalts is one of these soil types and in these

regions, outcrops of basalt rock known as basalt floaters occur extensively (Graaff

and Wootton 1996).

In this paper, a suite of extensive laboratory tests were undertaken on crushed

basaltic waste rock and their geotechnical properties investigated and compared to

that of traditional virgin quarried material used in flexible pavement sub-bases.

Laboratory tests were conducted on 20 mm nominal size crushed waste excavation rock samples as obtained from a recycling facility. The properties of the crushed waste rock were assessed to gauge its performance as a pavement sub-base material. Currently 3.3 million tonnes of waste excavation rock is stockpiled annually in 3 Copyright 2011 by the American Society of Civil Engineers


Australia, with 656,000 tonnes of basaltic waste rock stockpiled annually in the state of Victoria (Sustainability-Victoria 2010). Similar significant quantities of waste rocks and marginal materials are also stockpiled worldwide in numerous countries (Nunes et al. 1996; Rodgers et al. 2009; McKelvey et al. 2002; Akbulut and Gurer


2007) thus making this an issue of global significance.

This research is significant as it will enable the diversion of large amounts of waste

excavation rocks from landfills worldwide, and enable their sustainable usage in

various Civil Engineering infrastructure works, particularly targeting pavement subbases. The properties of waste excavation rock may vary from country to country and location to location. Nevertheless, the approach used in this research is applicable to

similar waste excavation rocks in other countries and provides an approach for waste excavation rocks to be used as a sustainable construction material instead of being

destined for landfills.

REVIEW OF PAST STUDIES

Nunes et al. (1996) while carrying out a study on secondary materials for pavement

construction in the United Kingdom reported California Bearing Ratios of 5% and

35% for minestone and slate waste respectively. Nunes et al. (1996) conducted

repeated load triaxial test for slate waste in an unbound form and reported a resilient

modulus value of 272 MPa. Rodgers et al. (2009) experimented on sandstone aggregate originated from arenaceous sedimentary rock and reported that at an applied pressure of 500 kPa the resilient modulus was 205 MPa.



McKelvey et al. (2002) examined the shear behaviour of 40 mm uniform crushed recycled rock in a study of their use in ground improvement works in the United Kingdom. Shear strength tests were carried out in a 305 mm by 305 mm shear box with a maximum shear strain in both dry and wet conditions. Angles of internal friction of 48 degrees to 51 degrees were reported for crushed basalt based on the


shear box tests.

Akbulut and Gurer (2007) have previously reported on particle densities of marble

quarry waste in Turkey. The authors used four types of rock materials for their study,

namely, waste marble, andesite and two other limestones. The authors reported that the specific gravity or particle density of the materials ranged from 2.40 to 2.70. Flakiness index of waste marbles and andesite was reported as 9.41% and 8.63% respectively while that for two different types of limestone was reported as 3.54%

and 4.85%. Los Angeles Abrasion loss results indicated the marble waste exhibited the maximum abrasion loss with a Los Angeles value of 27.44% which was

attributed to the outcome of high calcium oxide content. The Los Angeles Abrasion

loss result for the andesite was reported as 25.89% while that of the two specimens of limestone resulted were reported as 25.60% and 20.91%.

The sustainable reuse of traditionally waste materials in civil engineering including

pavement sub-base applications has generated much interest worldwide in recent years. Of late, research has been undertaken by several authors on various recycled

waste materials in road and pavement applications. This includes reclaimed asphalt pavement (Puppala et al. 2011; Hoyos et al. 2011; Taha et al. 2002), recycled crushed brick (Arulrajah et al. 2011a; Aatheesan et al. 2010; Poon and Chan 2006;



Debieb and Kenai 2008; Gregory et al. 2004), recycled crushed glass (Wartman et al. 2004; Grubb et al. 2006; Clean Washington Center 1998; Ali et al. 2011; Disfani et al. 2011a; Disfani et al. 2011b), recycled concrete aggregate (Sobhan and Krizek 1998; Poon and Chan 2006; Tam and Tam 2007; Tam and Tam 2006; Courard et al. 2010), other types of Construction and Demolition wastes (McKelvey et al. 2002;


Khalaf and DeVenney 2005; Bennert et al. 2000) and wastewater biosolids (Arulrajah et al. 2011b). Other forms of marginal pavement materials have also been

widely reported by various other authors (Tao et al. 2010; Nunes et al. 1996; Rodgers et al. 2009; Akbulut and Gurer 2007; Papagiannakis and Masad 2007; Saride et al.

2010).

The common ground on past research on these waste materials is that many of these are recent publications and thus highlight the global urgency to seek a sustainable

solution for our vast stockpiles of various waste materials. This paper seeks to similarly solve the issue of the vast stockpiles of excavation waste rocks that are

often encountered during excavation for residential sub divisional development and civil excavation works that are commonly disposed worldwide, and to investigate

their geotechnical characteristics and potential reuse in pavement sub-base applications. This is believed to be a novel area of research on a waste material, with

few reported publications available on waste excavation rock, destined for landfill which involves significant quantities worldwide.

LABORATORY EXPERIMENTAL WORKS Samples of crushed basaltic waste rock were collected from a recycling site at Victoria, Australia. Samples were obtained by bulk sampling of waste excavation 6 Copyright 2011 by the American Society of Civil Engineers


rock stockpiles at the recycling site in 20 kg sample bags. The crushed waste rock had a maximum aggregate size of 20 mm. Laboratory tests were subsequently undertaken on the waste rock samples by using ASTM, British Standards and Australian Standards, as appropriate.


The experimental investigation included laboratory tests such as particle size

distribution, modified Proctor compaction, particle density, water absorption, California Bearing Ratio (CBR), Los Angeles abrasion loss, pH, organic content, static triaxial and repeated load triaxial (RLT) tests. Initially, the basic characterisation tests were performed to determine the properties of the crushed

waste rock samples. Subsequently, these tests were followed by the study of the

stiffness and permanent deformation characteristics of crushed waste rock under

repeated load triaxial testing regimes. The tests undertaken on the crushed waste rock were extensive and based on tests typically recommended by road authorities

worldwide on virgin quarry aggregates. These tests were undertaken to ascertain if the crushed waste rock could meet the performance requirements of traditional granular aggregates and if so could be used as a sustainable construction material in

pavement sub-bases. The tests suitable for testing recycled aggregates according to

various test standards has also been described by Sivakugan et al. (2011). The criteria

applied for laboratory testing enabled the assessment of the geotechnical properties

of the waste excavation rock prior to consideration of this material for future field applications

Particle size distribution and hydrometer analysis tests were performed in accordance with AS 1141.11 (1996) and ASTM-D 422 (1963) respectively. Particle density and water absorption tests were undertaken on both coarse (retained on 4.75 mm sieve) 7 Copyright 2011 by the American Society of Civil Engineers


and fine (passing 4.75 mm sieve) material. Particle density is one of the most important values to characterize pavement materials, because it allows understanding on many other properties of the material. In this study, the particle density and water absorption values were determined according to AS 1141.5 (2000) and AS 1141.6.1


(2000).

pH tests were performed in accordance with AS 1289.4.3.1 (1997). Organic content

tests were performed in accordance with ASTM-D2974 (2007). The ignition method was used to determine the organic content of the aggregates.

Hydraulic conductivity tests were performed in accordance with AS 1289.6.7.2 (2001). The samples were compacted at optimum moisture content and 98% of

maximum dry density. As the hydraulic conductivity of the samples was comparably smaller, falling head method was used to measure the hydraulic conductivity. The

sample was saturated overnight with de-aired water before starting the test to make

sure that the voids in the sample is fully saturated. While running the test, the falling of water level in the standpipe was recorded with time. The height and diameter of sample were measured and the diameter of the standpipe also recorded.

Flakiness index tests were performed in accordance with BS 812-105.1 (2000). Oven dry samples passed 63.0 mm and retained on the 6.30 mm sieve were selected for testing. Since the maximum aggregate size of the tested material was 20 mm, three subdivisions of aggregate were prepared. Materials passed 20 mm and retained on

14 mm, passed 14 mm and retained on 10 mm, passed 10 mm and retained on 6.30 mm sieve were the three subdivisions. The three subdivisions of samples were sieved through the respective special sieve sizes. The flakiness index of aggregates was 8 Copyright 2011 by the American Society of Civil Engineers


determined by the ratio of the combined mass of all particles passing each of the gauges to the total mass of the test portion.

The Los Angeles Loss abrasion test is the most widely specified test for evaluating the resistance of aggregates to abrasion and impact forces (Papagiannakis and Masad


2007). Following the standard test method for resistance to degradation of small-size

coarse aggregate by abrasion and impact in the Los Angeles machine (ASTM-C131 2006), LA abrasion tests were conducted on all sources. This test has been widely used as an indicator of the relative quality or competence of various sources of aggregate having similar mineral compositions.

Modified compaction effort was used to determine the maximum dry density and

optimum moisture content of the material. The modified compaction tests were conducted by following the Australian standard AS 1289.5.2.1 (2003), which is

similar to the ASTM-D1557 (2009). A cylindrical mould having an internal diameter of 105 mm and effective height of 115.5 mm was used for modified compaction

tests. The samples were compacted into the mould in five layers each and compacted

by 25 blows of a 4.9 kg rammer falling freely from a height of 450 mm.

California Bearing Ratio (CBR) test method followed the Australian standard AS 1289.6.1.1 (1998). The CBR tests were carried out on specimens subjected to modified Proctor compaction effort at the optimum water content and soaked for four days to simulate the worst case scenario. In the modified California Bearing Ratio (CBR) tests, samples were placed in a cylindrical mould (internal diameter of 152 mm) and compacted in five layers totalling an effective height of 117 mm by using a



spacer disc inserted into the mould before compaction. Modified compaction effort was used.

Crushed waste excavation rock is a coarse-grained material with a maximum particle size of 20 mm. In addition due to the reasonably high coefficient of consolidation


within the thin sub-base layer, consolidation is likely to be completed within a short

duration. Therefore, the Consolidated Drained (CD) triaxial test was considered

appropriate for determining the shear strength properties of the aggregate for longterm condition, since drainage will be allowed throughout the entire test which was

considered as suitably simulating actual field conditions. The CD triaxial tests were

performed in an automated triaxial testing system in accordance with ASTM-D4767

(2004). The samples were prepared in split mould of 100 mm diameter and 200 mm

in height. The test specimen was compacted to 98% of modified proctor maximum dry density in a split mould in eight layers. The compaction was done by mechanical compactor with around 15 blows of modified compactive effort for each layer. The initialization process was carried out before the saturation phase to check the proper functioning of the entire system and to detect early leaks through the rubber

membrane, the fittings, or the triaxial chamber. The saturation stage was initiated by increasing back pressure and cell pressure in order to achieve maximum saturation

while a constant effective stress (total stress minus back pressure) of 25 kPa on the

specimen was maintained. As the increase in cell pressure was applied, the system monitored the increase in back pressure. The back pressure was raised before the next cell pressure increment was applied, so that the effective stress on the specimen

was maintained. Due to this procedure, air in the specimen was absorbed and resulted in a greater B–value close to unity. Back pressure up to 725 kPa and cell pressure up to 750 kPa were applied in these series of tests and this process was carried out until 10 Copyright 2011 by the American Society of Civil Engineers


the minimum B–value of 0.95. Upon completion of saturation process applying back pressure, isotropic consolidation stage was carried out at effective confining pressures of 50 kPa, 100 kPa and 200 kPa. Triaxial compression (shearing) was executed on the saturated and previously consolidated specimens. The samples were compressed at the given consolidated confining pressures under drained conditions


(CD test). The shearing was performed under stain – controlled condition at the

selected strain rate of 0.01 mm/min. The CD triaxial test was considered appropriate for triaxial testing of recycled waste excavation rock. CD triaxial tests were undertaken at the Optimum Moisture Content (OMC) of the waste excavation rock,

which is considered the worst case scenario as it is the wettest state that would be supplied to the field

The Repeated Load Triaxial (RLT) Test was performed on the crushed basaltic waste rock according to Austroads (2000), the testing procedure of which is similar to the

test methods specified by AASHTO T 307-99 (2003). The RLT testing consists of two phases of testing, permanent strain testing followed by resilient modulus testing. Permanent strain testing consists of three or four stages, each performed at different

deviator stresses and a constant confining stress. A constant confining stress of 50

kPa and deviator stresses of 150 kPa, 250 kPa and 350 kPa were applied at each

stage respectively. Each loading consisted of 10,000 repetitions. The resilient

modulus testing phase consists of sixty six (66) loading stages with 50 repetitions, where confining stress varies between 20 kPa and 150 kPa and deviator stress varies

between 100 kPa to 600 kPa. 3 samples were prepared and air dried back to target moisture contents of 70 %, 80 % and 90 % of the optimum moisture content (OMC), to simulate the possible field moisture contents of sub-bases.



RESULTS AND DISCUSSION The geotechnical properties of crushed basaltic waste rock obtained from the laboratory tests are summarised in Table 1. There are little available publications and reported findings on marginal materials similar to waste excavation rock and as such


the comparison of results with similar materials is limited.

The particle size distribution results before and after compaction for crushed waste rock is shown in Figure 1. The ―after compaction‖ grading curves show that some breakdown has occurred during compaction. Nevertheless, both before and after

compaction grading curves were well within the specified upper and lower bound limits as shown in Figure 1. The materials appear to be remaining reasonably well graded through the compaction process and this will generally aid the compaction process.

Particle density and water absorption tests were undertaken on both coarse (retained on 4.75 mm sieve) and fine (passing 4.75 mm sieve) materials. It can be noted from

Table 1 that the particle densities of coarse and fine aggregates are almost same with values around 2.86 Mg/m3, which is noted to be within only 5% difference of values

reported by Akbulut and Gurer (2007) for marble waste and andesite. The water

absorptions of fine aggregates are slightly higher than the coarse aggregates. The density results indicate that the qualities of aggregates in the coarse and fine particle are same.

The organic content was found to be low and with value of 1.04 %. The pH value was above 7 and this indicates that the material is alkaline by nature. 12 Copyright 2011 by the American Society of Civil Engineers


The hydraulic conductivity of the crushed waste excavation rock material was found to be 2.7 x 10-7 m/s which can be described as low. The hydraulic conductivity for the material was however deemed to be within the local road authority drainage requirements of 1 x 10-7 m/s for a pavement sub-base material, based on a flexible


pavement with a thin asphalt water-proofing layer.

A flakiness index value of 19 was obtained which is only nominally higher than the

maximum limit of 15 normally specified by the local state road authority, indicating that the material is still suitable for sub-base applications. The flakiness index was noted to be twice as compared to that reported by Akbulut and Gurer (2007) for marble waste and andesite.

The Los Angeles Abrasion Loss value of 21 was obtained which is well below the

maximum limits of 35 normally adopted by the local state road authority in Australia for sub-base pavement materials. This indicates that crushed waste rock is durable and can be used in pavement sub-base applications. The values are noted to be within a similar range to that of marble and andesite waste reported by Akbulut and Gurer (2007), which was similarly found to be less than the maximum limits targeted.

The compaction curve for the crushed basaltic waste rock is presented in Figure 2.

The maximum dry density of the waste rock after modified Proctor compaction effort was found to be 2.23 Mg/m3 at the optimum moisture content of 9.3%.

CBR tests were undertaken on samples collected at 3 different durations several months apart. The CBR values were between 121 to 204% and found to satisfy the state road authority in Australia requirements for a lower sub-base (Class CC3) 13 Copyright 2011 by the American Society of Civil Engineers


material which requires a minimum CBR value of 80%. The range in CBR results for the various sampling series could be due to slight variations in the aggregate strengths and compositions since they were carried out on different bulk samples and several months apart.


Consolidated drained (CD) triaxial tests undertaken on the crushed waste rock

indicated that it had a drained cohesion of 46 kPa and a drained friction angle of 51º.

The Mohr-Coulomb envelope from the triaxial tests in presented in Figure 3. The deviator stress versus vertical strain plots from the triaxial tests is presented in Figure

4. Interestingly, the drained friction angle was identical to the results reported by McKelvey et al. (2002) based on large shear box testing of crushed basalt in the United Kingdom.

In the Repeated Load Triaxial (RLT) tests, the material were compacted to 98%

modified proctor maximum dry density (MDD) and samples tested at moisture contents of 67%, 71% and 84% of the OMC. The RLT test result of permanent strain

testing (variations of permanent strain and resilient modulus against number of load

cycles) for the crushed basaltic waste rock is plotted in Figure 5 and Figure 6. The resilient modulus values from resilient modulus test with 66 stress stages were

presented in Figure 7. In the permanent deformation test (Figure 6), 50 kPa confining

pressure was used, whereas, in the resilient modulus test (Figure 7), the specimens were tested under 66 stress stages and each stage involved at least 50 cycles at the

stress condition of specified repeated deviator stress and static confining stress and higher resilient modulus values were obtained for higher confining stresses.



The sample with 71% of the OMC was not tested for the Stage 1 condition (Dynamic Deviator Stress = 150 kPa), as it was expected that this sample would perform well at a low deviator stress level. The low permanent strain and high resilient modulus of the 71% of the OMC sample at higher deviator stress levels, as indicated in Figures 5


and 6, confirmed this expectation.

Data from the 67% of the OMC sample is not presented in Figure 7 as the sample

failed at the start of this stage of testing. This is an additional testing phase and not considered essential as resilient modulus values can be obtained from the first phase of testing. This second phase of testing also has predefined variations in stress stages

and this additional phase of testing is not considered truly representative nor necessary to determine the performance of a pavement sub-base material.

The results of permanent strain and resilient modulus values at the end of each test

stages for the waste rock are given in Table 2. As the sample with 71% of the OMC was not tested for the Stage 1 condition, there is no corresponding result for this sample in Table 2

Table 3 presents the typical results of traditional granular sub-base materials used by the state road authority in Australia for comparison. The results of the waste rock indicated that, for the compaction standard of 98% modified proctor MDD and

moisture contents in the range of 67% to 84% of the OMC, the crushed basaltic

waste rock had much smaller permanent strain and much higher modulus than natural granular sub-bases. Moreover, high level of the modulus values achieved for the waste rock suggests that ―residual cementing action‖ is occurring in these samples.

While this action may result in shrinkage cracks and possibly some 15 Copyright 2011 by the American Society of Civil Engineers


reflective cracking, it is unlikely that will significantly affect the performance of the pavement layer over time. Interestingly, the resilient modulus values reported in Table 2 were found to match well and within the same range compared to those reported by Nunes et al. (1996) for minestone, slate waste as well as Rodgers et al. (2009) for arenaceous sedimentary rock. It may be concluded that the effects of


crushed basaltic waste rock content on the mechanical properties (both deformation

and resilient modulus) were marginal compared to the effects of dry density and moisture content.

The crushed waste excavation rock was found to perform satisfactorily at 98% MDD and at moisture content of 67% to 71% of the OMC, meeting the requirements

expected from a traditional quarried sub-base material. The crushed waste excavation rock showed sensitivity to moisture and produced higher limits of permanent strain and lower limits of resilient modulus, at 84% of the OMC.

It is noted that the normal operating field moisture content for most pavement

materials is generally below 75% of the OMC as such the performance at higher

moisture contents uniquely represents the ―worst case scenario‖. As expected the

performance of the material will be affected by increasing moisture contents and the density level achieved in the compacted samples.

CONCLUSIONS

The results of the laboratory testing undertaken in this research have shown that the crushed basaltic waste excavation rock satisfied the criteria for its use as an



aggregate in pavement sub-base applications. The degree of breakdown occurring in the waste rock is on the limit of what would be acceptable for this material.

The grading limits of the waste rock, ―before and after‖ compaction were compared to and found to be within the local state road authority specified upper and lower


bounds for usage of aggregates as a pavement sub-base material. The flakiness index value of crushed waste rock obtained in this investigation indicates that the material

is suitable for sub-base and base applications. The Los Angeles Abrasion Loss value

obtained, which is below the maximum limit adopted by the local state road authority indicates that waste rock is durable and can be used in pavement sub-base

applications. The CBR values obtained were between 121 to 204% and found to satisfy the local state road authority requirement for a lower sub-base material which requires a minimum CBR value of 80%.

The repeated load triaxial tests also established that crushed waste rock would

perform satisfactorily as a sub-base material in the field. The crushed waste

excavation rock was found to perform satisfactorily at 98% MDD and at moisture content of 67% to 71% of the OMC, meeting the requirements expected from a

traditional quarried sub-base material. The crushed waste excavation rock showed sensitivity to moisture and produced higher limits of permanent strain and lower limits of resilient modulus, at 84% of the OMC.

The results of the laboratory testing undertaken in this research indicated that crushed basaltic waste excavation rock satisfied the criteria for use in pavement subbase applications. The authors intend for this research to highlight that waste excavation rocks traditionally destined for landfill, can be used in a sustainable 17 Copyright 2011 by the American Society of Civil Engineers


manner in pavement sub-bases. The results presented would provide the reader an indication of the testing methodology, geotechnical properties and performance of these waste materials. A similar research and a quality control testing program is required locally to confirm if materials available elsewhere can meet the specified


local requirements for pavement sub-base applications.

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List of Tables

Table 1: Geotechnical properties of crushed basaltic waste rock.


Table 2: Results of permanent strain and resilient modulus from permanent strain testing for crushed basaltic waste rock at the end of each loading.

Table 3: Range of permanent strain and resilient modulus for traditional granular subbases (Arulrajah et al. 2011a).



Table 1: Geotechnical properties of crushed basaltic waste rock.

Geotechnical Parameters Particle density - Coarse (Mg/m3) Particle density - Fine (Mg/m3) Water absorption - Coarse (%) Water absorption - Fine (%) Organic content (%) pH Fine content (%) Hydraulic conductivity (m/s) Flakiness Index Los Angeles abrasion loss CBR (%) Compaction Max dry density (Mg/m3) (Modified) Optimum moisture content (%) Triaxial Test Cohesion (kPa) (CD) Internal friction angle (degree) Moisture Content = 84 % of OMC Resilient Modulus Moisture Content = 71% of OMC (MPa) Moisture Content = 67% of OMC

Crushed Basaltic Waste Rock 2.86 2.85 3.32 4.72 1.04 10.92 10.2 2.7×10-7 19 21 121-204 2.23 9.3 46 51 121-218 202-274 127-233

Accepted Manuscript Not Copyedited



Table 2: Results of permanent strain and resilient modulus from permanent strain testing for crushed basaltic waste rock at the end of each loading.

Sample description

Permanent strain (micro strain) Resilient modulus (MPa)

Actual Moisture content (% of the OMC) 84 71 67 84 71 67

Stage1: confining stress = 50 kPa deviator stress = 150 kPa 6629 -7939 148 193

Stage2: confining stress = 50 kPa deviator stress = 250 kPa 11715 6366 10620 181 240 213

Stage3: confining stress = 50 kPa deviator stress = 350 kPa 17835 9234 14653 218 274 233




Table 3: Range of permanent strain and resilient modulus for traditional granular subbases (Arulrajah et al. 2011a). Sample description

Permanent strain (micro strain)

Resilient modulus (MPa)

Target Moisture Content (% of the OMC)

Stage1: confining stress = 50 kPa deviator stress = 150 kPa

Stage2: confining stress = 50 kPa deviator stress = 250 kPa

Stage3: confining stress = 50 kPa deviator stress = 350 kPa 10000- failure (>20000) 10000-failure (>20000)

90

7000-15000

10000-20000

80

5000-10000

7000-15000

70

3000-10000

4000-15000

5000-20000

90 80 70

125-300 150-300 175-350

150-300 175-300 200-400

175-300 200-300 225-400




List of Figures Figure 1: Particle size distribution of crushed basaltic waste rock before and after compaction.


Figure 2: Compaction curve for crushed basaltic waste rock. Figure 3: Mohr-Coulomb failure envelope for crushed basaltic waste rock from Consolidated Drained triaxial tests.

Figure 4: Deviator stress versus vertical strain plots for crushed basaltic waste rock from Consolidated Drained triaxial tests.

Figure 5: Permanent strain testing - Permanent strain determination for crushed basaltic waste rock.

Figure 6: Permanent strain testing - Resilient modulus determination for crushed basaltic waste rock.

Figure 7: Resilient modulus testing - Resilient modulus of crushed basaltic waste

rock.


Figure 1



Copyright 2011 by the American Society of Civil Engineers

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Figure 7


