TRANSPORT and ROAD

RESEARCH LABORATORY

Department of the Environment

TRRL REPORT LR 447

COMPACTABILITY OF GRADED AGGREGATES

1. STANDARD LABORATORY TESTS

by

D.C. Pike

Materials Section

Construction Division

Transport and Road Research Laboratory

Department of the Environment

Crowthorne, Berkshire

1972

LR447

CONTENTS

Abstract

1. Introduction

2. Materials examined

2.1 Sources of standard experimental aggregates

2.2 Standard gradings

2.3 Ancillary tests

3. Compaction tests

3.1 Preparation of materials

3.2 Compaction of specimens

3.3 Measuring and weighing of specimens

3.4 Degradation during compaction

3.5 Calculation and plotting of results

4. Discussion

4.1 The influence of particle shape and texture upon compactability

4.2 The influence of grading upon compactability

5.

6.

7.

8.

4.2.1 Influence of general grading

4.2.2 Influence of fines content

4.3 Optimum moisture content

4.4 MPVS as a parameter ofcompactability

Summarised conclusions

Acknowledgement

References

Appendix

Page

1

1

2

2

2

2

2

2

3

3

3

3

4

5

6

6

6

6

7

7

8

8

8

Q CROWN COPYRIGHT 1972

Extracts from the text may be reproduced

provided the source is acknowledged

Ownership of the Transport Research Laboratory was transferred from the Department of Transport to a subsidiary of the Transport Research Foundation on l S t April 1996.

This report has been reproduced by permission of the Controller of HMSO. Extracts from the text may be reproduced, except for commercial purposes, provided the source is acknowledged.

COMPACTABILITY OF GRADED AGGREGATES 1. STANDARD LABORATORY TESTS

ABSTRACT

As part of an investigation into the mechanical properties of graded aggregates, British Standard vibrating hammer compaction tests have been carried out on a wide range of materials.

It has been found that if results are expressed on a volumetric basis they can be used to simplify studies of the effects on compacta- bility of changes in properties such as particle shape, texture and size distribution.

None of the experimental materials exhibited optimum moisture contents according to the standard criteria: a method of overcoming this problem is proposed. Research aimed at providing improvements in apparatus and method is continuing.

1. INTRODUCTION

There are many different kinds of road-making aggregates used in Gt. Britain, and their mechanical

properties strongly influence the performance of both unbound and bound mixtures during construction

and also in service. Two of the most important aspects of these mechanical properties are compaction and

mechanical stability.

As part of a programme of research into the classification of aggregates, a study is currently being made

of the shear strengths of compacted, graded aggregates using a shear-box machine. Several preliminary steps

were necessary for this work: standard aggregates have been selected, a method of preparing these materials

has been developed and standard gradings have been adopted.

The densities of packing and the shear strengths of graded aggregates are inter-dependent, an increase

in dry density usually producing an increase in shear strength for a given material. The British Standard

vibrating hammer compaction test 1 has been used to assess the relative compactability of the materials to

be examined in the shear-box tests.

During the compaction tests it became apparent that several features of the standard method should

be reconsidered for this investigation. It was necessary to develop both a volumetric basis for reporting test

results, to overcome the differences between the specific gravities of the experimental aggregates, and also

a method of estimating optimum moisture contents for these materials because none of them yielded

results which could be dealt with according to the standard procedures.

This Report discusses the results of the compaction tests, and the techniques which have been developed

for plotting the results, for assessing compactability and for estimating optimum moisture contents.

2. MATERIALS EXAMINED

2.1 Sources of standard experimental aggregates

For the programme of research into the classification of aggregates 17 aggregates have been selected

from the 1500 or so possible sources in Great Britain such that each of the main categories of trade group,

petrological type and particle shape and texture are represented. A summary of these sources is given in

Table 1, and their geographical distribution is illustrated in Fig. 1.

2.2 Standard gradings

14 standard gradings having a nominal maximum size of 38 mm have been selected to represent the

broad range of size distributions in common use for sub-base, road-base and basecourse materials. These

gradings are shown in Table 2 and eight of them are plotted graphically in Figs. 2 and 3; they include

examples of well-graded, poorly-graded and gap-graded distributions and are specified in terms of proportions

finer than a set of 10 sieve-sizes which form a simple series.

'Table 2 also gives values of coefficient of uniformity for the standard gradings. The coefficient of

uniformity is defined as the ratio of that aperture size through which 60 per cent of a meterial passes, to

that aperture through which 10 per cent passes, and is used in soil mechanics to quantify the state of grading

of a material (see Section 4.21).

2.3 Ancillary tests

For the purposes of this investigation standard tests specified in British Standard 812 2 have been

carried out on the experimental materials. Table 3 gives values of oven-dried specific gravity and water-

absorption for four sizes of each aggregate, and Table 4 gives values for these properties weighted for the

gradings actually used in the compaction tests. Table 5 gives values of angularity number and Table 6 gives

values of flakiness index both measured on a range of sizes larger than 6.3mm.

3. COMPACTION TESTS

The British Standard vibrating hammer compaction test, described in BSi 3771, was designed to reproduce

the states of compaction achieved when granular materials are compacted in full-scale conditions using heavy

plant under proper supervision. The test requires the measurement of dry densities of specimens which

have been compacted at a range of moisture contents into a metal mould having a diameter of 152mm using

an electrically-powered vibrating hammer.

3.1 Preparation of materials

The raw aggregates obtained from quarries were subjected to a wet-sieving process which removed

almost all dust or silt and screened the products into 10 roughly single-sized fractions. These fractions were

dried and recombined to the required gradings. In those cases where a content of material finer than

0.075ram was required the deficits in fines were made up with non-plastic, ground, silica flour.

A standard mix-weight of 5kg was used for all specimens. Six mixes of each type were made up for

Aggregates 1 to 17 to Grading I and for Aggregates 4 and 11 to Gradings II to XIV. One of each type of

mix was subjected to wet-sieve analysis. The other five mixes were used in compaction tests: one was used

dry and the other four had different quantities of water added, so that initial moisture contents were

produced to span the range between the dry state and a state slightly above saturation for full compaction.

The wetted materials were hand-mixed and allowed to stand overnight to allow the aggregates to absorb

water; they were then remixed before use.

3.2 Compaction of specimens

The mixes were compacted generally in accordance with the British Standard test except that the

whole of each mix was used, regardless of the height of the compacted specimens. Most specimens exhibited

,heights within the limits prescribed by the B.S. test, but a few were slightly too high. It is probable that

this did not affect the results of the tests significantly.

During compaction it was found that the vibrating action of the hammer drove off some dust from

the dry specimens, and also forced out a sludge of water and fine aggregate from the wettest specimens.

Both the dust and sludge were lost either OUtside the mould or on to the top of the compaction tool.

3.3 Measuring and weighing of specimens

After compaction the specimens generally exhibited top surfaces which were plane except for narrow

peripheral ridges of fine material. These ridges were trimmed off and the heights of the specimens were :

measured in accordance with the standard test method, except in the case of specimens which contained

low proportions of fine aggregates and which exhibited rather open-textured top surfaces. In these cases a

metal disc of known thickness was placed firmly on the trimmed specimens and measurements were made

to the top face of the disc. After measurement each specimen was weighed, and then dried and:reweighed.

for the determination of moisture content.

3.4 Degradat ion during compaction

Some of the Weaker aggregates were observed to crush during compaction.. Wet-sieve analyses were

carried out On specimens both before and after compaction and it was found that both particle strength and

grading affected the degree of degradation suffered by the experimental materials. The gradings obtained

from the sieve analyses made on specimens after compaction have been used in this Report where the

influence of particle size distribution upon compactability is discussed.

3.5 Calculat ion and p lo t t ing of results

The British Standard test requires the calculation of dry densities and moisture contents, and the

plotting of these results on graphs together with 'air-voids lines' calculated from values of specific gravity

as shown in Fig. 4. The positions of the air-voids lines in these graphs vary with specific gravity and it is

not easy to compare the compactability of aggregates having different specific gravities.

This difficulty may be overcome by transposing the results of compaction tests to a volumetric basis,

and a simple method of transposition has been developed for this purpose. ~Briefly, the method reduces the

3

results of compaction tests into statements of the proportions of the volumes of compacted specimens

which are occupied by solids, water and air, as fol lows:-

where

100 = V s + V w f + V a f

Vs = proportion of volume occupied by solids - per cent

Vwf = proportion of volume occupied by free water (i.e. water held between, not within,

particles of aggregate) - per cent

Vaf = proportion of volume occupied by free air (i.e. air held between particles of

aggregate) - per cent.

The method of calculating these volumetric parameters is illustrated in Fig.5 with typical results from

this investigation, and the amended graph for plotting results is shown in Fig.6. A distinction is made

between 'free' and 'absorbed' water, because absorbed water can play no part in compaction. Zero propor-

tion of volume occupied by free water implies complete saturation of the voids within the aggregate

particles; because of difficulties in making accurate measurements of Water-absorption values using the test

procedures given in BS812 2 this theoretical assumption can be applied only approximately at present.

Aggregates at moisture contents lower than their water-absorption values yield negative values of proportion

of volume occupied by free water; these negative values can be visualised as potential demands for water

which must be satisfied when water is added, before any 'free ~ water is generated.

The results of all the compaction tests are plotted on a volumetric basis in Figs. 7 to 12.

4. DISCUSSION

The British Standard vibrating hammer compaction test requires that:

"1. The dry density . . . . . . . . corresponding to the maximum point on the moisture-content/

dry-density curve shall be reported as the 'maximum dry density' . . . . . . . .

2. The percentage moisture content corresponding to the maximum dry density on the

moisture-content/dry-density curve shall be reported as the 'optimum moisture content' ."

A definition of these terms is given in Fig. 1 of BS 1377 2 which is reproduced in Fig.4a of this Report. It

will be seen from Figs. 7 to 12 that none of the curves plotted therein have convex-upward shapes, and

indeed most of them are of the type illustrated in Fig.4b. The convex-downward shape of these curves

may be explained as follows. At zero moisture content, high densities were achieved because the specimens

were almost entirely enclosed by the mould and the compaction tool. (In compaction tests such as the

2.5kg rammer and 4.5kg rammer tests 2 the compaction tool occupies only a relatively small proportion

of the surface area of the specimen, and a blow applied at one side of the surface may cause disruption

within a specimen of dry granular material without increase 'in dry density.)

When small amounts of water were added some moisture was absorbed within the particles of aggregate

but when this demand had been satisfied the particles became coated with thin films of water, which were

tightly held by strong surface tension forces and acted as displacers even when high compactive forces were

applied. This displacing effect increased with increase in moisture content until a "pessimum" moisture

content was reached (cf Fig.4b), at which a minimum level of dry density was recorded.

4

Further increase in moisture content yielded sufficieht free water tolubricate• the particles, and dry "

densities then increased with increase in moisture'content .towards saturation. The addition of water beyond

that amount required to saturate the aggregate at full compaction had little effect on dry ~ density, because

excess water was driven out, together with some fine aggregate. The tendency for granular materials tO

yield relations between dry density and moisture content of this type is probably especially marked where

they contain non-plastic fines, but similar effects have been noted during tests on a clay-bound hoggin. • z ~ ' l ~ , •

Lewis and Parsons 3 have shown that convex,downward curves are obtained when water-bound

macadams are compacted in the field with a wide range of plant, and workers in the US 4 have also reported ' i

similar results achieved with vibrating hammer compaction tests.

Although the results obtained cannot be used directly, to give values of maximum dry density and

optimum moisture content, a simple method of obtaining these parameters for materials of the type

described has been developed. In order to overcome the problem of differences in specific gravity referred

to in Section 3.5, the maximum proportion of volume Occupied by solids has been preferred to the maximum

dry density for this investigation.

The maximum values of proportion ofvolume occupied by solids were achieved either on dry specimens

or on specimens at or near saturation. Because the values achieved on the dry •specimens Were general!y very

similar to the values obtained on the wettest specimens, the 'dry' values have been adopted as parameters of

compactability for this investigation• (the use of 'dry' values can reduce laboratory testingfime - see

Section 4.3). The values ofmaximumproportion of volume occupied by solids measured on dry materials

(hereafter referred to as MPVS) have been used to assess the effects of changes in particle 'shape~ texture and

grading of graded aggregates.

4.1 The influence of particle shape and texture upon compactability

Values of MPVS for each of the 17 standard aggregates combined to Grading I are shown in Fig.13

grouped by petrological type. It will be seen that in each of the petrological groups (except the limestones)

values of MPVS decrease as the angularity of particles increases: also the rougher-textured aggregates give

generally lower values than the smoother materials. The slightly different results achieved with limestones

can probably be attributed to the relatively flaky shape of the coarse particles of Aggregate 7 (see Table 6).

Much research has been carried out into the effects of the shape and texture or" aggregate particles •

upon their mechanical properties. British Standard 8122 includes the angularity number test which measures

the void contents of single,sized coarse aggregates subjected to light compaction in metal moulds. Average

values of angularity number from Table 5 are plotted against MPVS values for 17 aggregates to Grading i in

Fig. 14.

The angularity numl~er cannot be used to assess the compactability of graded aggregates; nor is the

type of compaction used in this test.similar in nature or degree to that used in field conditions. Nevertheless,

a highly significant* correlation was obtained betwee n the values plotted in Fig. 14, showing that, provided

the grading is kept constant, an increase in angularity and roughness of the coarse particles Produces a

reduction in compactability.

Where the term 'highly significant' appears in this Report it means statistical significance at the 99 per

cent (P = 0.~01) level.

5

4.2 The influence of grading upon compactability

The standard gradings vary both in the general shape (e.g. 'well-graded', 'poorly-graded' or 'gap-graded')

of the size distributions of the particles between 38mm and 0.075mm in diameter, and also in the content

of fines. The effects of these variations are considered separately.

4 .2.1 Influence of general grading. Coefficients of uniformity (CU - see Section 2.2) are used as a

guide to the general shape of size distributions. Well-graded size distributions give high values (CU> about 40)

and poorly-graded and uniformly-graded distributions give low values; gap-graded distributions may require

special consideration.

In Fig. 15 values of MPVS for Aggregates 4 and 11 combined in the 14 standard gradings are plotted

against the logarithms of coefficients of uniformity for these gradings calculated from the results of wet-sieve

analyses made on samples after compaction. Highly significant correlations were obtained for both aggregates;

as would be expected the well-graded mixtures gave higher levels of dry density than the poorly-graded

materials.

4 .2 .2 Influence of fines c o n t e n t . Gradings I to IX are all well-graded but include three groups of size

distributions, each having a common grading but with varying fines contents. Gradings I, IV and VII lie close

to the central gradings specified for a number of road materials in common use, Gradings II, V and VIII lie

near the coarse limits permitted for these materials and Gradings III, VI and IX lie at the fine extremes.

Fig. 16 shows values of MPVS for Aggregates 4 and 11 to Gradings I to IX arranged into sub-groups according

to the gradings of the fractions coarser than 0.075mm, plotted against fines contents calculated from the

results of wet-sieve analyses made after compaction.

It will be seen that values of MPVS generally increased with increase in fines content in the range 0 to

10 per cent, except for the 'central' sub-group of gradings for Aggregate 4 which gave a maximum level of

density at a fines content of about 5 per cent.

4.3 Optimum moisture c o n t e n t

Most of the experimental materials gave highest dry densities when compacted dry or at initial

moisture contents at or slightly above that proportion of water required to saturate the aggregates at a state

of full compaction. For the purposes of the investigation into the shear strengths of graded aggregates it

has been necessary to develop a method of estimating optimum moisture contents for these materials.

The strong vibrating action of the compaction hammer drove off excess water from the saturated

specimens, but I if this loss of water had been prevented artificially by sealing the mould so that only air could

escape, the compaction tests would probably have yielded results similar to those illustrated in Fig.17, and

it would then have been possible to identify optimum moisture contents for the experimental materials.

These optimum moisture contents would be very close to the moisture contents required to saturate the

aggregates at the maxinlum levels of dry density achieved in the compaction tests. Assuming that equal

levels of dry density are achieved on dry and saturated specimens these saturation moisture contents are

given by the expression:-

100 - MPVS ) + W. Abs. OMC = 1 O0 ( M--ffV~ x SpG

where OMC = estimated optinmm moisture content for graded aggregate - per cent

6

MPVS = maximum proportion of volume occupied by solids - p e r cent

SpG = oven-dried specific gravity of aggregate

W. Abs - water-absorption value of aggregate - per cent.

The derivation of this expression is given ifi the Appendix to this Report. Values of optimum moisture

content for the experimental materials using this expression and both 'dry' and 'wet ' values of MPVS are

shown in Table 7. The differences between the two sets of estimates of optimum moisture content are

small enough in most cases to permit the use of 'dry' values of MPVS for the estimation of optimum moisture

contents for further laboratory work, although mixes to Gradings II, X and XIII require special consideration.

It will be seen from Figsl 9 to 12 that mixes to these gradings did not give simple convex-downward

curve s exhibiting similar levels of dry density when dry and at saturation. These materials contained low

proportions of fine aggregate and nominally no material finer than 0.075mm, and yielded relatively low-

density, open-textured specimens in the compaction tests and the concept of optimum moisture content

probably cannot be applied to them in a simple way.

4.4 MPVS as a parameter of compactability

It has been shown in Section 4.2.4 that values of MPVS are influenced by the shape and texture of

aggregate particles, and in Section 4.2 that they are also influenced by grading. Fig. 15 shows that the

differences in MPVS values obtained for two aggregates are maintained over a wide range of gradings. It is

concluded that values of MPVS provide a useful way of monitoring the combined effects of particle shape,

texture and grading of graded aggregates on their compactability. The significance Of this finding upon

shear strengths will be investigated in the next phase of the work. Values of MPVS are based on the results

of a test which employs a compaction hammer which generates high compactive forces, and therefore they

are more likely to be related to results obtained in the field than existing standard parameters of compact-

ability such as the angularity number; it is intended to check this point during later field work.

Mthough the British Standard vibrating hammer test has yielded useful results in this investigation,

further modifications are needed to improve the reliability of results to be used in detailed studies of the

mechanical properties of aggregates. Further research is being carried out to investigate possible ways of

improving methods of measuring water-absorption value and of overcoming loss of fines during the compac-

tion test.

5. SUMMARISED CONCLUSIONS

1. The results of a series of BS vibrating hammer compaction tests carried out on a wide range of graded

aggregates gave convex-downward curves when plotted graphically, although compaction tests carried

out on soils usually yield convex-upward curves.

. The results obtained in this investigation were transposed to a volumetric basis and the 'maximum

proportion of volume occupied bY solids' (MPVS) measured on dry specimens has been adopted as

a parameter of laboratory compactability. A method of calculating optimum moisture contents has

been developed also usfng values~ofMPVS.

. It has been shown that the values of MPVS obtained were related, in quantifiable ways, to the shape,

texture and grading of the particles of the aggregates examined, and that values of MPVS can be used

to assess the combined effects of these variables upon c0mpactabili'ty.

6. ACKNOWLEDGEMENT

The work described in this Report is part of the programme of the Sand and Gravel Association Cooperative

Research Team operating within the Materials Section of the Construction Division of the Laboratory, under

the direction of Mr. G.F. Salt.

7. REFERENCES

1. BRITISH STANDARDS INSTITUTION. Methods of testing soils for engineering purposes. British

Standard BS. 1377. London, 1967 (British Standards Institution).

. BRITISH STANDARDS INSTITUTION. Methods of sampling and testing of mineral aggregates, sands

and fillers. British Standard BS.812. London, 1967 (British Standards Institution).

3. LEWIS, W.A., and A.W. PARSONS. The performance of compaction plant in the compaction of two

types of granular base material. Road Research Laboratory Technical Paper No. 53. London, 1962

(Her Majesty's Stationery Office).

4. DOVE, R.P., T.G. WILLIAMSON and H.R.J. WALSH. Development of a high-velocity impact test

for laboratory compaction. West Lafayette, Indiana, 1968 (Indiana State Highway Commission).

5. ROAD RESEARCH LABORATORY. Soil mechanics for road engineers. London, 1952 (Her

Majesty's Stationery Office).

8. APPENDIX

A method of calculating the moisture content required to saturate exactly a sample of graded aggregate at a known dry density.

The mathematical expression used in Section 4.3 for the calculation of estimates of optimum

moisture content for the experimental materials con be derived by a series of simple arithmetical steps.

A diagrammatic representation of the composition of a sample of saturated graded aggregate is shown in

Fig. 18, which is a modified version of Fig. 9.6 of 'Soil Mechanics for Road Engineers'. 5

The moisture content of the saturated sample is given by the total mass of water as a proportion of

the total mass of dry solids, but as shown at Section 3.5 it has been found to be convenient to consider

separately the free water held between the particles of aggregate and the absorbed water within the particles.

The content of absorbed water is obtained from ancillary tests (see Section 2.3 and Fig. 2), but it is

necessary to calculate the free water content which, using the symbols in Fig. 18, is given by the expression:

Free moisture content = 1 O0 x Mwf per cent . . . . . . . . . . . . . . . (1) Ms

8

Values of Mwf are not given directly by the calculations of the results of compact ion tests i l lustrated in

Fig. 5, but may be obtained simply from the volumetric data. By d e f i n i t i o n : -

Mwf = 3 'wf x V w f . . . . . . . . . . . . . . (2)

and Ms = 3's x Vs x 3 'wf . . . . . . . . . . . . . . (3)

hence Equation (1) may be r e w r i t t e n : -

Free moisture content = 100 x Vwf x 7 wf • (4) Vs x 3's x " /wf . . . . . . . . . . . . .

The terms used in Equation ( 4 ) m a y be simplified b~, transposing the symbols used therein into the symbols

and units used for the results of the compaction tests. For a saturated sample at full c o m p a c t i o n : -

Vs = MPVS - per cent

Vwf = (100 - MPVS) - per cent

') 's = Sp.G

therefore Equation (4) may be rewritten (cancelling values of 3' w f ) : -

100 ± MPVS ) Free moisture content = 100 ( M-~--~ x S---~.G-

and the total moisture is obtained by adding the absorbed w a t e r : -

Saturat ion moisture content = 100 1 0 0 - MPVS + W.Abs (fl- g x S-p.C

. . . . . . . . . . . . . . ( 5 )

. . . . . . . . . . . . . . ( 6 )

9

T A B L E 1

Sources, petrological types and descriptions of the shape and surface texture of the coarse particles of the 17 experimental aggregates

Ref. no.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

Name

Bridport

Chertsey

Longfield

Branston

Rugeley

Hartshill

Cerney

Carnforth

Holcombe

Stanley Ferry

Scorton

Haughmond

Harehill

Llwyn

Croft

Clee Hill

Corby

General type*

G

G

G

G

G

R

G

G

R

G

G

R

G

G

R

R

Petrological Description of coarse particles

type Shape Texture

Flint

Flint

Flint

Quartzite

Quartzite

Quartzite

Limestone

Limestone

Limestone

Gritstone

Gfitstone

Gritstone

Igneous

Igneous

Igneous

Igneous

Very rounded

Irregular

Angular

Rounded

Mixed

Angular

Rounded, flakey

Mixed

Angular

Rounded

Angular

Angular

Rounded

Mixed

Angular

Angular

Very smooth

Smooth

Very smooth

Smooth

Mixed

Rough

Smooth

Mixed

Rough

Rough

Very rough

Very rough

Mixed

Mixed

Rough

Rough

Slag Angular Very rough

* G = sand and gravel, R = crushed rock, S'= slag

10

0 ~

0

-~ c~

X .E ~ o

2 .~

. ,,~

% . . ~

--,I "~t

I-- ~

': N

"~-1 " .

~o

'I=)

0 0 I ~ ~ ~ (~l ~ co

0 ~ ~ ~ ~'~ o~ ~ cO

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

• -~ 00

0 0

0 o0

0 ¢xl

00

o0 0 0

0

0 0 0 0

× R

~ O0

O0 ,-~

O~

O0 O~

I TM O4 0

0 0 0 0 0 0

- >

- R x x

11

TABLE 3

Results of measurements of oven-dried

specific gravity and water-absorption values on four sizes

of each of the 17 standard aggregates

iAgg. ref. n o .

9

10

11

12

13

14

15

16

17

38 to 19 mm size

Specific Water absorption

gravity - per cent i

2.53 0.58

2.56 0.71

2.58 0.38

2.59 0.50

2.60 0.53

2 . 6 3 0.61

2.55 2.27

2.62 0.75

2.70 0.21

2.42 2.70

2.49 1.64

2.79 0.44

2.63 0.71

2.64 0.67

2.59 1.24

2.85 0.48

2.58 0.81

19 to 9.5 9.5 to 4.8 Material finer mm size mm size than 4.8 mm

absorption absorption Specific Water absorption gravity - per cent

Specific Water

gravity - per cent

2.53 1.10

2.50 1.90

2.57 0.60

2.59 0.56

2.60 0.59

2.63 0.64

2.50 3.03

2.61 0.97

2.70 0.24

2.42 3.50

2.50 1.58

2.79 0.55

2.63 0.66

2.63 0.79

2.59 0.98

2.85 0.51

2.65 0.91

Specific Water

gravity - per cent

2.51 1.30

2.43 3.30

2.54 1.06

2.56 1.10

2.58 0.70

2.63 0.70

2.45 3.83

2.63 0.98

2.70 0.24

2.49 4.50

2.52 1.69

2.79 0.52

2.61 0.83

2.63 0.73

2.59 1.09

2.85 0.62

2.73 0.74

2.55

2.56

2.60

2.58

2.56

2.64

2.62

2.68

2.70

2.61

2.57

2.79

2.63

2.67

2.59

2.81

2177

1.20

1.10

2.80

0.90

1.20

0.38

1.02

0.19

0.24

2.40

1.08

0.70

0.35

0.46

1.39

0.90

0.68

12

" T A B L E 4

Weighted values of oven-dried specific gravity and

water-absorption value for the experimental graded aggregates

a) 17 aggregates to Grading I

Aggregate

reference n o .

7

8

9

10

11

12

13

14

15

16

17

Weighted value of:

Specific

gravity Water abs.

- per cent

1 2.53

2 2154

3 2.58

4 2.58

5 2.58

6 2.63

2.55

2.64

2.70

2.53

2.54

2~79

2.63

2.64

2.59

' 2.85

2.70

1.0

1.5

1.5

0.8

0.7

0.6

2.1

0.5

0.2

3.0

1.4

0.5

0.6

0.7

1.2

0.5

0.8

b) Aggregate 11 to Gradings II to XIV

Grading

reference

n o .

II

III

IV

V

VI

VII

VIII

IX

X

XI

XII

XIII

XIV

Weighted value of:

Specific

gravity

2.52

2.55

2.54

2.52

2.55

2.54

2.52

2.55

2.50

2.56

2.53

2.52

2.55

Wa te r abs. - per cent

1.5

1.4

1.4

1.5

1.4

1.4

1.5

1.4

1.6

1.2

1.4

1.5

1.4

Notes: 1. These values are calculated by

weighting the values given in Table 2 by the proportions used in each mix.

2. The effect of the added silica flour upon these values has been ignored.

3. All mixes made with Aggregate 4 gave identical values.'

13

TABLE 5

Angulari ty numbers measured on the 17 experimental aggregates

Aggregate Angulari ty number measured on particles of s i z e : -

reference ,

no. 19 to 13 mm 13 to 9.5 mm 9.5 to 6.3 mm

3

4

6 12

9

10

11

12

13

14

t5

16

17 ̧

10

12

14

10

10

11

10

9

9

6

8

10

I0

12

11

12

10

11

11

9

11

14

14

Average

result

(all sizes)

10

10

11

10

10

I0

12

13

14

TABLE 6

Flakiness indices of 6 sizes of the coarse fractions of

the 17 experimental aggregates

Aggregate reference

n o .

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

Flakiness index measured on particles of s i z e : -

l ! to 1 in 2

38 to 25 mm

10 12

22 15

20 17

10 6

16 14

26 16

47 37

13 10

15 5

37 30

58 52

19 10

9 6

67 44

43 30

39 32

11 14

l ! to 1 in 4

32 to 25 mm

1 to 3 in 4

_3to l_in 4 2

19 to 13 mm mm

14 21

26 18

26 35

12 18

25 41

15 36

43 41

12 19

13 15

45 33

28 34

43 19

7 2 8

21 26

24 6

36 30

26 28

25 to 19 mm

3

14

13

10

16

15

41

8

7

25

36

12

10

24

31

22

17

1__ to -3in 2 8

13 to 9.5

__3 to ! i n 4- 4

9.5 to 6.3 mm

2

30

26

10

60

16

19

10

14

32

23

13

7

12

12

19

12

Average result

(all sizes)

10

21

23

11

29

21

38

[2

12

34

39

19

11

32

24

30

18

15

TABLE 7

Estimates of optimum moisture content calculated

according to the method given in Section 4.3

Mix reference nos.

Aggregate Grading

1 I

2 I

3 I

4 I

5 I

6 I

7 I

8 I

9 I

10 I

11 I

12 I

13 I

14 I

15 I

16 I

17 I

Note*

Optimum moisture content - per cent

using 2 values of MPVS

'dry' 'saturated'

4.6 5.0

6.7 6.2

7.3 7.0

3.8 4.4

5.2 5.8

6.0 6.6

7.0 7.1

5.0 5.0

5.0 5.0

8.0 8.2

7.2 7.3

6.5 6.2

4.2 5.1

5.3 4.8

6.4 6.4

6.6 6.4

6.5 7.3

The term 'optimum moisture

content'cannot be easily

applied to these mixes

(see Section 4.3).

Mix reference nos.

Aggregate Grading

4 II*

4 III

4 IV

4 V

4 VI

4 VII

4 VIII

4 IX

4 X*

4 XI

4 XII

4 XIIi*

4 XIV

1 1 II*

11 III

11 IV

11 V

11 VI

11 VII

11 VIII

11 IX

11 X*

11 XI

11 XII

11 XIII*

11 XIV

Optimum moisture content - per cent

using 2 values of MPVS

'dry' 'saturated'

7.1 8.2

4.3 4.4

5.3 5.0

5.3 5.6

5.7 5.8

4.1 3.4

4.7 4.4

5.0 5.1

14.2 14.6

6.3 7.5

3.8 4.6

8.0 7.1

4.4 5.5

9.0 11.5

6.7 6.5

8.1 8.0

7.2 7.3

7.5 9.1

6.8 5.8

6.7 8.2

7.5 8.1

17.5 19.6

9.0 10.3

6.3 7.2

9.0 11.0

7.4 8.4

1 6

®

®

. ®

Fio.1. APPROXIMATE LOCATIONS OF THE SOURCES OF THE 17 STANDARD AGGREGATES

o, \ \ \ o \X\ a o \ X!', o ~ j

.l +,Oo o k / ~ _ .

0

~' o 0 " - I f ) ° ,~&- 0 0

0 0 0 0 0 0 0 0 0 03 cO I',. CO i13 ~" (~ o,I ,--

(),ua:) Jad) SaAa!S 6utssod uo!),JOdoJd aAp, OlnU-m3

O

E

E °--

E

E

t'3

E

E °--

E

O --

I13

03 --

tO

o~ I~, --

O O

0 0

0 c~

0 o 0 z z

E m ~i

~ L I-.13. 0 0- ° = ~ .E_ ~ 7 L ~ 8 0 1

n Q0

(a lO:)s 6O l ) saz !s @Jn~J@dD @A@!S

p - .

w

w

< I . - J

w

w

w

z

z • e l ~ ' }

I w I Z

z

z

cJ

c ~

!

0

l i - Q

t i .

o

L L J

C ~

!

a m

C ~

LL

120

~- 115 -1 U

.Q

v 110

0

~6 105

1- I ) ~ 1 0 0

f._ 121

95

I 10O/o 5O/o 0O/o

~k_ k_~_~_---~Air voids lines

Compact icn / \ I \ \ \ c u r v e _ _ _ ~ / \ i \ \ \

o I E u I I

0 5 10 15 20 25 30 Mo is tu re content (per cent )

(a) Def in i t i ons of t e r m s used in compact ion tests , rep roduced f rom Fig. 1 of B.S. 1377

150

-~ 140 u

JQ

v

>~ 135

e.-

130

~3

A, vo,0s ,,nos

145 07° ' (Gs = 2.E;7)

/ CO urv m oc on

125

120 0 5 10 15 20 25 30

M o i s t u r e con ten t (per cent )

(b) Typical resu l t of a compac t i on t es t achieved in th is i n v e s t i g a t i o n

Note : -The volues of dry dens i t y , mo is tu re content ond opporen t specif ic g r a v i t y used in Fig. 4b ore token f rom doto given in Fig. 5 fo r M ix 6/ I . The uni ts hove been chosen for d i rect comporison w i t h Fig. 40.

Fig./.. TYPICAL RESULTS OF COMPACTION TESTS

U

L E •

& o

3 > o E '- o

t - o o

L . 0 0 0

L

0 0

u

m ~

0 "-- L ~

@ @

> o L

U

~g o.

c- Q)

O) L U "0

~ o

E " -

m N

@

~.g r- o- 0 0 ~D

~0 --.I" 0 ~ . , - e~

~r~ o ~ e~ • e,l

-,.-' ....t' -11-

u~ ~ 0 0 - o,"

O4 --.it eO "~ 0

0 "

i ! ! ~ i

c~ 0 0 0 r~ ~o 0,-

O4 ~r) • (1{) r - cO

0 I ~n I ~ I . -~ ; ~ 0 0

~,~ ~,o'- ,,,o'- ,,o'- ~oo ~6 ~o ~o'- ,,,~,o L Z Z Z Z Z Z Z Z Z 0_

E c"

~ ,~ ~ o. = E r o . n L E ~ ' - o 0 ~ u~ -~

u~ 0 O_ "0 ~ ._ ¢- ~n L

~" E o~ . _ . . . _ o

Eo "- ~'~ 0 • Z o~ o~ oE ~ E u

- 5 o . ~ o e e c~ o = o . ._~-~ .~ L ~ "1 U >'~ " 0 ' ' ~

0 .~ ~ = = o ~ " -

'-- ~ ~ '4" t_-lO' ,4--' (1; I -

, . , - , ~ > , . - ,.-, ~ . ~ . - > , ... ,, ,, o , o 0 L ~ ¢~ L

E .o ® 0 i

"5 u -~ ® U

I!

®

i

O i @ 8 i °

i O

I I I I I I

@ ® ® @ ® ® ® ®

~ o

w

e- m _~ g, . i ~

w

=i i

7 ~

w i.....-

0 0 ~ ~ .

E ~@ ~ . ~ ®

a . ~ U U O . ¢- U 0 " - "

0>-- ~ o ,- > L 0 ~" I

®~- o °

i 1 . . o 0_ n

@ @ > ° ~-

° 4 $ • °t. ~

I I I I " ~

z ® ®

100

9 6

U

{ -

c~ v 9 2 i n 13

O

/3

13

8 8 3 U U O

E

0 >

" - 8 4 0

0

0

0 L

13_

80

76

~ Zero oir voids

i

Absorbed I - t

w c l t e r I I

- 4 0 4 8 12 Proportion of volume occupied by residuGI free woter (per cent)

\

Fig. 6. RESULTS FROM Fig. 5 PLOTTEO ON A VOLUMETRIC 8ASIS

A

c

u ̧

-6

J~

Q;

c~

u

0

Q;

E

0

"6 c-

O

0 r~

0

0.

100

9G

92

88

84

80

76

Zero a i r voids

I 10% ai r voids , \ I I I

-4 0 4 8 12 Propor t ion of vo lume occupied by res iduol f r ee wa te r ( p e r cent )

Note : - The . resul ts shown indicate the wide renge of va lues ob ta ined . The resu l t s of t h e o t h e r agg rega tes comb ined to Greding I a re shown in fig. 8

Fig. 7. RESULTS OF COMPACTION TESTS ON AGGREGATES 1, 2,L.,6,12,1t,,15,16 AND 17 EACH TO GRADING ]

100

9G

r -

U

( -

eL 92~ v

"o o - -

0

>~ .(3 "o

--~ 88 t~

u u 0

E 0 >

8 4 c 0

0 t l 0 L

(3 .

8 ( )

7 6 t - 8

Zero air voids

I I I 5°/o air voids I I I I '

t 8

[ L ~

/ 10% ai r voids

~ 3

\ \

- 4 0 4 8 12 Propor t ion of volume occupied by residual free w a t e r ( per cent )

Fig.8. RESULIS OF COMPACI'ION TESIS ON AGGREGAIES 3,5, 7, 8, 9,10,11 ANO 13 EACH TO GRAOIHG T

100

(-

U {_

(3.

13

0 u3

>~ .Q

13

(3.

u u 0

E 0 >

N-- 0

c- O

L_ 0 Q. 0 .

n

96

92

88

84

80

76

Zero oir voids

i - \ / i ~ 5 / o air voids \

. ~ 10°/o oir voids \

-4 Proportion

0 4 of volume occupied/ by residuol

\ 8 12

free woter (per (:ent)

Fig.9. RESUL'I'S OF COMPACIION 1ESIS ON AGGREGAIE /. TO GRAOIHGS TT TO 9m" •

100

9 6

u

"~ 9 2 " o

0

"o

m 88 u 0

E

0 >

~- 8 4 0

0 ° ~

0

0 L n

8 0

7 6

L ~ . Zero air voids-

A, i \ 5 i. o~r \ i

',):,

I I I I I I

"I I I I I I I •

10°/o air voids

I I • I I I 0

X

-4 4 8 12 P['oport ion of volume occupied by residual free water (per cent)

\

\

Fig. i0. RESULTS OF COMPACTION TESTS ON AGGREGATE t, TO GRAOINGS l'X TO ]~3[

¢; u

i_

Q.

i / 1 l o

O i/}

a~

10

o . -1 u u O

E -1

>

t - O

i_ O n O [ - Q.

100

6 k

92:.

88

8 4

80

76

i J " ' I " \ Zero o i r voids

! .

I 5 Io a i r voids I I ,

I \ ' Jj • ' . . " ,

111

f

, \ I I I

- 4 0 4 8 12 Proport ion o f volume occupied by residual f r e e w a t e r ( p e r cent )

Fig.11. RESULTS OF COMPACTION TESTS ON AGGREGATE 11 TO GRADINGS 11' TO gTIT

92 ! \ \ ' • Z e r o a i r v o i d s

N 8 4 ' o I " m

"o XI

o 76 ~ ^ c .o

Z I 0

o I L a_ I

I 72 I

I

I 6 8 I

- 4 0 4 8 12 16

P r o p o r t i o n o f v o l u m e o c c u p i e d b y r e s i d u o l t r e e w o t e r ( p e r c e n t )

Fig. 12. RESULTS OF COMPACTION TESTS ON AGGREGATE 11 TO GRADINGS 1~ TO

>, I -

, < , > o ~

b

° • I < ~ I r '~

. ~ . ~

,~ o , . . .

{ < =

~, >~ ~,-- I ~ I IZ: 1~ CL L,,+, "--'

>', " ~ ) U ~

i < , > o . , _ ~ ~='-><._ - : ~ ' .++ : : n > ° o ¢~ .,~ ~..~ I I Z _ _ j (~") t '-+ MJ

OJ -~.-" , ~ , c ¢

~ L t _ o - +..=, m Z o" ~ o = < = <

x x ~ t,.) -'-~ ~¢...~ L--"~ 00 , E , ~ ~ o m ~_,..-,

.+_+ -+-+ -; ,._+~ " - < I ~ c 0 o ° L .~ M J

,#'-, ~ ,"8 = " - & ~o ~ =. - . ,

"+ , <+', >=:>

o' > ~ ~ - ~ "~ "- (i. 0 u.,

/ /

I

I I I I I > ~ I o,,i 13") Ob (3O CO O0 GO 0

o~ ~- I .--- c ( l . U a 3 a a d ) $ P J l O S X q ¢) , . . :1-~ c

• L ¢ 1 L . , C p a ] d n 3 3 o ~ W n l O A JO u o ! l . J O d O a d L u n u J ! x o i ~ O'~LJ 0

~ u~ 0 LL. ~'_.,

ccn ~ ~ ~" era c ~

o . _ 0 ~ - ~

<3) u.~

0 ~-" Z •

i ~ U L ~ . c~ o ~ ~ ._~n

0 o o /

0

0

e3 " - (33 03 0"~ cO

) O - -

:) 0

0

I ~. CO

(),u=~3 Jad ) s p ! l o s /~q p a ! d n 3 3 o auJnlOh ;o uo!3,JodoJd LunuJ!×OlAi

0

o

dl

L

. o

E c

I',. >~

I_ 0

c

o I _

M

0 I/')

z I

w

v--

l.w

Z

u

GL.

Z

.-.I .

92

8 8 r "

U f ._

r ,

gl "ID

ffl

g 4 . 0

q> . _ O .

U U 0

E 8 0

-5 >

o

I_

o a 7 6 0

E

E × .

0 Iz

.,. 7 2

G8

~..OQ A g ~ e g q t e 11 .. " 0 0 . . . . . . . / 0 /

•

/ . /o.

//~" "~ii~o~i/-" / on,0o,or , A g g r e g o t e 11 , '.

10 4 0 C o e f f i c i e n t of un i fo rm i~ ty ( l o g s c a l e )

Fig. 15. CORRELATION OF HPVS WITH COEFFICIENT OF UNIFORHII"Y FOR TWO AGGREGATES 1'0 GRAOINGS 'Z TO 1/'TV

2 0 0

3 3 oon L L 3 ~ 0

~ "~ "i-

• o . E ¢ O ~ U .

L

.Cl

O

Z c ~ w

w

m

o

N

W

I

E ~ O ~

O U ~

L

E "

O

1.l '

110

O . Q . 3 "-1

88X

~ o . c _ u ~ m

I -

o

0 ~ oJ

(~Ua:3 Jad) sp!IOS Xq pe!dn33o auJnlo^ ~o uo!~JodoJd Lunw!xoIAI

O CO

0 O ""

C ~

Q .

C ~

E " "

O ~

C ~

O

~ P

. - i

o ~

t - G) l , J

L .

v

U . _

0 I /1

Q

"0

Q.

U u 0

E :3

0 >

5 t "

0 o~

f ,_

0

0 I _

D-

100

• Zero air voids

. " ~ " - " Portion of curve to I ~ /be obtained f rom

Volumetric equivalent of ~ / over-saturated '~maximum dry d e n s i t y " . ~ / specimens, if a

_ ' . . . . " . ~ ~ / were,used

Portion of curve l " l

• I ( r Ou nms arteuSrUamtt eS d on J specimens

I I I I i Volumetric equivalent

of 'free' fraction of "optimum moisture

I content" I // I 0

Proportion of volume occupied by residual free Water (per cent)

Fig.17. TYPE OF RELATION BETWEEN PROPORTIONS OF VOLUME OCCUPIED BY SOLIDS AND FREE WATER WHICH WOULD BE OBTAINED IF LOSSES OF EXCESS WATER

FROM OVER-SATURATED SPECIMENS WERE ARTIFICIALLY PREVENTED

Volume

>

t/i >

F ree w a t e r

. . . . . . . . , . . . ~ , , . . . . . . . ~ . . ~ , . , ~ . ; .~:~ ~ ~ ~ ' ~ " . ~ > ~ ~ ~:,~'46"+~:~'~s:'~.~:'==::'¢,~,", ; . "; .~: ~

t_. ~ * ,,$ :~c~: v. , : i~- :., z ~ ~..>..~ ~ . ~ , .

~:...~.~. ~,,~,'~: :.:~..,_-_~:,.. ~ ~ ; ; . ~ ; ~ ' ~ : ; ~ - : ~ ' ~ o v ~ , , ~ , : - . . . : ,~ .~- . ,~ . - , : : .> ",. , . . ~ .~ : ; - .< . . ,~ '~ : -~ : .,_.e~r +, ~, .~. .~ .v ,~.~. ; , . . ,~ , : ,~z ?,:-~"L-;r_;:,Z~;~'~:~ ;2:~.V~::::;:.~='..~ + :~.'..:!';'.~';;~.~]:?~%-':'-~.~=,_==.~",7; ~,.";,.:-~,

Symbo ls used in this f i gu re and in t h e A p p e n d i x V = t o t a l v o l u m e M= t o t a l mass

Vs= v o l u m e of so l ids M s = m o s s of so l ids Vw f=vo lume o f f r e e w a t e r Mwf = mass of f r e e w a t e r

Mwa = mass of absorbed w a t e r

1~ w.f = dens i t y of w a t e r

s = oven-d r ied spec i f i c g r a v i t y of so l ids

M Q S S

1,

>

o

÷

Fig.18. OIAGRAMMATIC REPRESENTATION OF .THE COMPOSITION OF A SAMPLE OF SATURATEO GRAOEO AGGREGATE

(349) Dd .635271 2 ,750 4/' /2 HP Ltd. So'ton G.1915 P R I N T E D I N E N G L A N D

ABSTRACT

Compactability of graded aggregates 1. Standard laboratory tests: D C PIKE: Department of the Environment, TRRL Report LR 447: Crowthorne, 1972 (Transport and Road Research Laboratory). As part of an investigation into the mechanical properties of graded aggregates, British Standard vibrating hammer compaction tests have been carried out on a wide range of materials.

It has been found that if results are expressed on a volumetric basis they can be used to simplify studies of the effects on compactability of changes in properties such as particle shape, texture and size distribution.

None of the experimental materials exhibited optimum moisture contents according to the standard criteria: a method of overcoming this problem is proposed. Research aimed at providing improvements in apparatus and method is continuing.

ABSTRACT

Compactability of graded aggregates 1. Standard laboratory tests: D C PIKE: Department of the Environment, TRRL Report LR 447: Crowthorne, 1972 (Transport and Road Research Laboratory). As part of an investigation into the mechanical properties of graded aggregates, British Standard vibrating hammer compaction tests have been carried out on a wide range of materials.

It has been found that if results are expressed on a volulfietric basis they can be used to simplify studies of the effects on compactability of changes in properties such as particle shape, texture and size distribution.

None of the experimental materials exhibited optimum moisture contents according to the standard criteria: a method of overcoming this problem is proposed. Research aimed at providing improvements in apparatus and'method is continuing.