THE USE OF INDUSTRIAL LIMESTONE WASTE IN SAHARAN …aim is to finding the optimal tuff-limestone sand mixture. Different formulations, of tuff-limestone mixtures, have been established

THE USE OF INDUSTRIAL LIMESTONE WASTE IN

SAHARAN ROAD DESIGN

SAHARAN YOL TASARIMINDA KIREÇTAŞI ENDÜSTRIYEL

KIRTASİYE ATIKLARININ KULLANILMASI

Idriss GOUAL*1, Mohamed Kamel GUEDDOUDA

2, Mohamed Sayah GOUAL

3,

Nabil ABOU-BEKR4, Saïd TAİBİ

5 and Ahmida FERHAT

6

Université de Laghouat, Laboratoire de recherche de Génie Civil, BP.37 G - 03000 Laghouat-

Algérie,

2 Université de Tlemcen, Laboratoire Eau et Ouvrages dans Leur Environnement, BP 230-

13000 Tlemcen, Algérie.

3 Université du Havre, Laboratoire Ondes et Milieux Complexes, 53 rue de Prony, BP540,

76058 Le Havre, France.

ABSTRACT

This work focuses on the exploitation of local industrial waste by their use in the formulation

of new material, which can be used in road engineering. This waste is limestone sand

extracted from local crushing stations of limestone rocks. An experimental investigation is

conducted, in two parts. The first one aims to study the effect of limestone sand addition on

the physicomechanical behaviour of tuff-limestone sand mixture. Different proportions of

limestone sand ranging from 0 to 50% were considered. The results carried out on the

compaction, bearing and compressive strength tests, have permitted to select the formulation

80% tuff + 20% calcareous sand, which present the best mechanical strength. The second one

aims to study the effect of treatment with few percentage (4% and 8%) of hydraulic binders

on the mechanical behaviour of tuff-limestone sand optimal mixture. After treatment, very

important improvement have been achieved on the mechanical behaviour of optimal mixture.

Finally, the experimental approach revealed the possibility of the use of local materials

containing tuff and quarry waste for the design of pavement and showed the interest of the

treatment process with hydraulic binders which is necessary in order to mitigate the problems

of non-stability in wet medium.

Key word: waste, tuff, mechanical behaviour, treatment, road engineering

*1 Phd , Research Laboratory of Civil Engineering, University of Laghouat , [email protected], [email protected]. 2,3,6 Phd, Research Laboratory of Civil Engineering, University of Laghouat , [email protected] ; [email protected];

[email protected]. 4

Université de Tlemcen, Laboratoire Eau et Ouvrages dans Leur Environnement,

5 Université du Havre, Laboratoire Ondes et Milieux Complexes

6 Title, Affiliation, e-mail

489

7. Geoteknik Sempozyumu 22-23-24 Kasım 2017, İstanbul

mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]

ÖZET

Bu çalışma, yol mühendisliğinde kullanılabilecek yeni malzeme biçiminde yerel endüstriyel

atıkların kullanılması üzerine odaklanmaktadır. Bu atık, kireçtaşı kayalardaki yerel öğütme

istasyonlarından çıkan kireçtaşı kumudur. Deneysel bir araştırma iki bölüm halinde

gerçekleştirildi. Birincisi, kireçtaşı kumunun eklenmesinin tüf-kireçtaşı kum karışımının

fizikomekanik davranışı üzerindeki etkisini incelemektir. % 0 ila 50 arasında değişen kireçtaşı

kumunun farklı oranları düşünüldü. Sıkıştırma, rulman ve basınç dayanım testleri üzerinde

yapılan sonuçlar, en iyi mekanik mukavemet olan% 80 tüf +% 20 kalkerli kumdur. İkincisi,

tüf-kireç taşı kumu optimal karışımı mekanik davranışı üzerine birkaç yüzdelik (% 4 ve% 8)

hidrolik bağlayıcı ile yapılan etkinin incelenmesidir. Tedaviden sonra, optimal karışımın

mekanik davranışı üzerinde çok önemli bir gelişme sağlanmıştır. Sonunda, deneysel yaklaşım,

döşeme tasarımı için tüf ve taş ocağı atığı kullanma ihtimalini ortaya çıkardı ve ıslak ortamda

dengesizlik sorunlarını hafifletmek için hidrolik bağlayıcıların muamelesinin gerekli

olduğunu gösterdi.

Anahtar kelime: atık, tüf, mekanik davranış, tedavi, yol mühendisliği

1. INTRODUCTION

The Algerian public works sector has seen in recent years a regained dynamism, characterized

by the intensification of relaunch process of construction project and rehabilitation of roads,

after a decade marked by severe economic crisis. The country's authorities have set up an

ambitious program, estimated at more than 10 billion dollars, gate on the realization of

important number of roads, highways and engineering structures , plus the development and

opening up of regions of the highlands and Southern Algeria. This program will have without

doubt a need of classic road materials ("good quality" aggregates) that exceeds what nature

can offer. In some desert regions, classic materials are scarce or even inexistent. The necessity

to build roads with optimized cost has prompted engineers and technical experts to adapt local

materials. Lot of these materials proved to be very interesting in road engineering, as tuff,

volcanic materials, sands, lateritic,… etc.

The tuffs are available in Algerian arid region; they cover an area of about 300,000 km2[1].

Their use in the construction of road pavements for low or average traffic is considerably

developed. Often, to improve their engineering properties for extend their uses in the

construction of road pavements at high traffic we need to be stabilized. Different techniques

of stabilization have been developed for more than 40 years, based on the association with

other materials (unbound granular materials or sand), or on the treatment with hydraulic

binders.[2]- [8]

Often, in Algeria, significant quantities of limestone waste of about 15millions of tonne by

year [9], generated from crushing stations, are untapped and which constituted both an

environmental nuisance and loss of raw material. Several researchers have considered the

reuse of these wastes in the field of building construction, they have allowed a new building

materials comparable to the usual materials or oven better [10]-[12]. Therefore, the idea to

reuse these wastes in the field of road engineering is original, it can solve threefold problems:

environmental, technical and economical. It is in this context therefore that we undertook this

study. Its objective is to valorise the local materials and to reuse industrial waste in road

construction. The experimental methodological is conducted on two parts. The first part,

explored the effect of limestone sand addition (0 - 50%) on the engineering properties of tuff

in order to find an optimal tuff- limestone sand mixture. The second part concerned the effect

490


of the treatment with few percentages (4 and 8%) of hydraulic binders on the mechanical

behaviour of the optimal mixture. The aim is dual: (i) to verify that the optimal formulation

conforms to the regulation rules, (ii) Extend their field of use in road pavements with medium

and high traffic.

2. MATERİALS

3.1. Basic materials

The basic materials used in this study come from the Laghouat region, located 400 km South

of Algiers, in Algeria. The first material is the tuff a material available within the Laghouat

region. It’s used often in road construction of low traffic. The second material is the limestone

sand, which is crushing waste of limestone rocks. Indeed, in crushing stations, the fraction of

aggregates whose diameter is greater than 3mm is commercialised; the rest is rejected into the

nature.

The chemical and EDX analysis of both materials is given in Table 2 and figure 1. The main

constituent is calcite, 51% and 76% for tuff and limestone sand respectively. According to the

CTTP standards [13], the materials satisfied the condition.

Table 1. Chemical analysis Results

Composition SiO2 Al2O3 Fe2O3 CaO MgO SO3 K2O Na2O L.F.

Tuff 8,89 1,85 0,66 48,44 1,34 0,56 0,26 0,00 40.14

Limestone sand

(Makhloufi et al.,

2012)

0.76 0.41 0.23 54.9 0.61 0.61 0.24 0.04 36.3

Figure 1. EDX analysis of the base materials

Figure 2, present the grading curves of both materials and standards spindle of the

dimensioning catalogue of new roads[13].The tuff is located outside the spindle of tuff 1, of

granular class 0/40 characterised by a skeleton purely frictional. It wedges better to the

spindle of tuffs 2 of granular class 0/20. For these materials, the resistance is purely achieved

by cohesion.

C: CaCO3

F: FeO2

S: SiO2

Tuff

C C C

C

C S

C

F

Limestone sand

C C

C C C

C

C

S

F

C C C

C

C C F

S

491


Figure 2. Grain size distribution curves for tested materials and standards spindle.

The results of geotechnical characteristics tests of both materials, and the standards

recommended by CTTP[13] are summarised in Table 2.

According to the CTTP standard, the tuff satisfy all the recommended conditions, it classified

under bearing class S2,which can be used in road pavements (basic, foundation) for principal

network Level 2 (RP2) [13].

3.2. Hydraulic binders

The hydraulic binders used in our study are lime and cement. There are chosen according to

their availability in our region. The lime used is hydrated lime, supplied by the SODEPAC

company, is 94% per cent Ca(OH)2. It is very fine and passes through an 80-μm sieve opening.

Concerning the cement used was COMPOSED PORTLAND CPJ-CEM II /A 42.5 NA 442,

supplied by the French Company LAFARGE, Algerian Unity.

Lime is widely used in civil engineering applications such as road construction, embankments,

foundation slabs and piles. When lime is added to soils (with clay particles) in the presence of

water, a number of reactions occur leading to the improvement of soil properties. These

reactions include cation exchange, flocculation, carbonation and pozzolanic reaction. The

cation exchange takes place between the cations associated with the surfaces of the clay

particles and calcium cation of the lime. The effect of cation exchange and attraction causes

clay particles to become close to each other, forming flocs; this process is called flocculation.

Flocculation is primarily responsible for the modification of the engineering properties of soils

when treated with lime [15].

Croft [16] found that the addition of lime significantly reduces the liquid limit, plasticity index

and maximum dry density of the soil, and increases its optimum water content and strength.

Bell [17] indicated that the optimum addition of lime needed for maximum modification of the

soil is normally between 1% and 3% lime by weight, and further additions of lime do not bring

changes in the plastic limit, but increase the strength. However, other studies reported the use

of lime between 2% and 8% in soil stabilization [18].

Cement treatment is similar to that of lime and produces similar results. Cement treatment

develops from the cementitious links between the calcium silicate and aluminate hydration

products and the soil particles [16]. Addition of cement to soils (with clay particles) reduces

the liquid limit, plasticity index and increases the shear strength [19].

0.01 0.1 1 100

20

40

60

80

100

Pas

sin

g (

%)

Diameter of soil particles (mm)

Tuff

Limestone sand

Spindle of tuff1 (0/40)

Spindle of tuff2 (0/20)

492


3.3. Methods

The experimental work consisted:

Firstly, the effect of limestone sand addition on the mechanical behaviour of tuff is study. The

aim is to finding the optimal tuff-limestone sand mixture. Different formulations, of tuff-

limestone mixtures, have been established in this way with limestone sand content varying

from 0 to 50 %.The experimental works are followed by compaction using the Modified

Proctor energy as per ASTM D1557 standards. CBR tests were also performed on specimens

prepared to maximum Modified Proctor density and optimum moisture content according to

ASTM D1883 standards. Unconfined compressive strength (UCS) test according to ASTM

D2166 standards were conducted on cylindrical samples, with a diameter of 50 mm and height

of 100 mm, compacted by static compaction with double piston at MPO and conserved at 0, 3,

7, 14 and 28 days in open air.

Secondly, the influence of type and percentage of binder on the physical and mechanical

behaviour of the optimal mixture is made. The experimental work included the addition two

percentages 4 and 8% of different hydraulic binders: Portland cement, hydrated lime, and

mixed = x% cement + 3.x% lime (x = 1-2).

Numerous studies focused on hydraulics binder stabilisation of soils have been published in

literature and the application of this technique has seen much advancement in civil engineering

practice and research[20]-[33].

The effect of treatment on the compaction characteristics and bearing of soil explain

immediate stability were determined by conducting modified proctor tests and CBR tests on

specimens according to ASTM D1557 and ASTM D1883 respectively, with different amounts

of binder. Unconfined compressive strength tests on compacted specimens were conducted

according to ASTM D2166 and ASTM D4609, translate long-term mechanical behaviour.

The materials were mixed with binder thoroughly until a uniform colour was observed.

Formation of clumps was avoided when water was added to soil binder mixture. All

specimens for the strength test were prepared at their optimum water content on cylindrical

samples, with a diameter of 50 mm and height of 100 mm, and compacted by static

compaction with double piston. The mixing and compaction was completed in less than an

hour. For each binder contents, two sets of specimens were prepared. One set of specimens

consists in measuring the variation of UCS, with respect to time was tested after 3, 7, 14 and

28 days of curing in the open air. The other set of specimens was cured for aperiod of 28 days

in the open air, then immersed in water for 1, 3 and 7 days prior to testing.

3. RESULTS AND DİSCUSSİON

3.1. Effect of limestone sand addition (formulation of an optimal mixture)

3.2.1. Compaction test

Figure 3 shows the variation of the maximum dry density and optimum water content with the

limestone sand content. As the amount of limestone sand increased, the maximum dry density

increased and the optimum water content decreased. When the limestone sand content varied

from 40% to 50%, the maximum dry density and the optimum water content remained

unchanged at 2.04g/cm3and9.8% respectively.

These results can be readily explained by noting that as the limestone sand increase they

replacement the fin elements of tuff, which, due to their shape and size play a role lubricant.

As the limestone sand increase, it lubricates the particles of the tuff, and facilitates their

493


movement by guiding them to fill the voids causing higher soil density during compaction. A

corresponding decrease in the water content will follow due to the replacement the fin

elements of the soil matrix. However, beyond a certain limiting value, the amount of

limestone sand, in the range of percentages tested, will be in excess to what is needed to fill

the voids of the compacted soil matrix and no increase in the maximum dry density will be

achieved.

From these results, in the range of limestone sand percentages tested in this study, it is

reasonable to think that the 40% of limestone sand can be considered in the first time as the

optimal mixture for which the compactibility cannot be improved.

Figure 3. Variation of (a) the optimum water content and (b) maximum dry density with

limestone sand content

3.2.1. CBR test

CBR tests were carried out on both soaked and unsoaked Specimens. Figure 5 shows the

variation of the CBR values with the limestone sand content for the soaked and unsoaked

specimens. The results indicate a marked increase of about 50% in the CBR values as the

limestone sand content increased to 30% and 40% for unsoaked and soaked specimens

respectively. However, for the mixture containing 50% limestone sand the CBR values

dropped while keeping greater than values or equal to those of natural tuff.

A close examination of Figure 4, reveals that the soaked CBR values are smaller than the

unsoaked values with a significant difference for the mixture with 30% limestone sand. This

is due to the sensitivity of the tuff to moisture increases. This is characteristic of the non-

cohesive granular materials, which owe their cohesion to the presence of the capillary forces

during compaction. These forces disappear starting from a certain threshold, the presence of

water becoming harmful for cohesion[34].

The results highlighted, in the range of limestone sand percentages tested in this study, an

optimum limestone sand content range between 30 and 40 %, which present the best bearing.

Figure 4. Variation of the CBR values with limestone sand content

0 10 20 30 40 50 609.0

9.5

10.0

10.5

11.0

11.5

12.0

Op

tim

um

wat

er c

on

ten

t (%

)

Limestone sand content (%)

(a)

0 10 20 30 40 50 601.92

1.95

1.98

2.01

2.04

2.07

2.10

(b)

Max

imu

m d

ry d

ensi

ty (

g/c

m3)


0 10 20 30 40 50 600

10

20

30

40

50

CB

R (

%)


Unsoaked

Soaked

494


3.2.1. Unconfined compressive strength test

The most common test to characterise hardening consists in measuring the variation of

unconfined compressive strength (UCS), with respect to time for compacted tuff- limestone

sand mixtures. The UCS is an index to evaluate the cohesion of compacted

materials[4][7][35]- [38].

Figure 5 translates the variation of UCS with limestone sand content from the 3rd at 28th day

of maturation. For each time, the maximum UCS values are obtained for different limestone

sand content. At 3rd day the UCS increased with limestone sand content to reach maximum

value correspond to 50% of limestone sand content. Beyond this time, between the 7th at 28th

day, it appears optimal limestone sand content varied from 20% to 40% for which the

compressive strength is maximum. Noted that this optimum (Figure 6), decreases when the

time increases and stabilizes at 20% limestone sand from the 14th day. A maximum UCS value

of the order of 4.1 MPa is indicated for 20% of limestone sand content corresponds an increase

of 8% compared to natural tuff.

Figure 5. Variation of the UCS with limestone

sand content at different times

Figure 6. Variation of the maximum UCS with

limestone sand content at different times

Subject to verification of this data for other ages beyond 28th day and in the range of limestone

sand percentages tested in this study, it is reasonable to think that the 20% of limestone sand

content can be adopted as the optimal mixture, which presents the best mechanical strength.

Finally, from the first part of these experimental investigations, the formulation composed

from 80 % tuff + 20 % limestone sand is chosen us an optimal mixture, which present the best

mechanical strength. This optimal mixture will be from now on called TSCopt

The physico-mechanical and chemical properties of the TSCopt compared to natural tuff with

the standards regulation are summarized in table 2. The TSCopt satisfy all the recommended

conditions, it classified under bearing class S1, which can be used be used in road pavements

(basic, foundation) for principal network Level 2 (RP2, ˂ 1500 vehicles / day)[13].

3.2. Effect of treatment on the mechanical behaviour of TSCopt

3.2.1. Compaction test

The effect of treatment on optimum water content and maximum dry unit weight of soils were

determined from modified proctor tests and are as shown in Figures 7a and 7b, respectively. It

can be observed that, generally, as binder content increased, optimum water content increased

whereas maximum dry unit weight decreased. Changes in compaction characteristics are

significant at lower percentages of binder (4%) whereas changes of compaction characteristics

of treated soils are minimal at higher percentages of binder (8%).

0 10 20 30 40 50 602.75

3.00

3.25

3.50

3.75

4.00

4.25

3rdday 7

thday

14thday 28

thday

UC

S (

MP

a)


0 10 20 30 40 50 603.25

3.50

3.75

4.00

4.25

28th

day

14th

day

7th

day

Max

imu

m U

CS

(M

Pa)


3rd

day

495


Table 2. Physico-mechanical and chemical properties of base materials and TSCopt.

Geotechnical characteristics tests

Material CTTP

standard Tuff Limestone

sand TSCopt

Grading analysis test ASTM D 6913

Granular class 0/D

Fine fractions < 80µm (%)

Uniformity coefficient Cu (%)

Hazen coefficient Cz (%)

30

32

67

1.2

3

15

12

0.8

30

15

30

1.9

20-40

22-32

-

-

Atterberg Limits tests ASTM D 4318

Liquidity limit LL (%)

Plasticity limit LP (%)

Plasticity index IP (%)

33

22

11

17

-

-

34

-

-

< 40

-

< 15

Methylene Blue value test ASTM C1777

Methylene blue value MB (0/D) 0.5 0.13 - -

Modified Proctor test ASTM D 1557

Optimal water content wMPO (%)

Maximum unit dry weight dMPO (g/cm3)

11.4

1.95

8.7

2.1

10.4

2

-

-

CBR test ASTM D1883

Un-soaked (%)

Soaked (%)

Bearing class [13]

24

17

S2

27

16

-

32

19

S1

-

-

-

Abrasion test ASTM C131 55 - - -

Los Angeles LA (%)

UCS test Rc28 (MPa) 3.79 - 4.1 -

CaCO3 content (%)[14] 51 76 57 ≥ 45

Figure 7.Variation of (a) Optimum water Content and (b) Maximum Dry unit weight versus

type and binder content

3.2.1. CBR test

CBR tests were performed on treated samples prepared to the maximum Modified Proctor

density and optimum moisture content. Tests were carried out on both soaked and unsoaked

0 4 810.0

10.5

11.0

11.5

12.0

12.5

13.0

13.5

14.0 Hydrated lime

Portland cement

Mixed

Op

tim

um

wat

er c

on

ten

t (%

)

Binder content (%)

(a)

0 4 81.90

1.92

1.94

1.96

1.98

2.00

2.02

Hydrated lime

Portland cement

Mixed

(b)

Max

imu

m d

ry d

ensi

ty (

g/c

m3)

Binder content (%)

496


specimens. The results, which are presented in figures 8a and 8b, and table 3, indicate a

marked increase in the CBR values as the binder content increased at both cases soaked and

unsoaked. At high percentage of binder (8%), a significant increase more than2 and 7 is

observed respectively on both unsoaked and soaked samples (table 3).

A close examination of Figure 8, and table 3, reveals that with lime treatment the soaked CBR

values are smaller than the unsoaked values. However, on both treatments with cement and

lime-cement mixture the soaked CBR values are more than the unsoaked values. These results

can be explained by the fact that immersion fosters cement hydration by analogy to concrete.

For example, at different cement content the soaked CBR index exhibited greater values

compared to unsoaked CBR index in a ratio of about 2.

Figure 8. Variation of the CBR values with type and binder content

Table 3. Summary of CBR value sand CBR ratio of treated samples compared to untreated

samples

Binder type Content (%)

CBR (%) CBR a d a

CBR a d a

Unsoaked soaked Unsoaked soaked

Hydrated lime

0

4

8

32

46

55

19

39

50

1

1.4

1.7

1

2.1

2.6

Portland cement

0

4

8

32

60

73

19

94

131

1

1.9

2.3

1

4.9

6.9

Mixed

0

4

8

32

51

64

19

69

90

1

1.6

2

1

3.6

4.7

3.2.1. Unconfined compressive strength

The unconfined compression test is one of the widely used laboratory tests in pavement and

0 4 80

20

40

60

80

100

120

140

160 Hydrated lime

Portland cement

Mixed

(a) Unsoaked

CB

R (

%)

Binder content (%)

0 4 80

20

40

60

80

100

120

140

160(b) Soaked Hydrated lime

Portland cement

Mixed

CB

R (

%)

Binder content (%)

497


soil stabilization applications. Unconfined compression strength is often used as an index to

quantify the improvement of soils due to treatment[33][39]. For example, ASTM D

4609(Standard guide for evaluating effectiveness of admixture for soil stabilization) states that

an increase in unconfined compressive strength of 345 kPa (50 psi) or more must be achieved

for a treatment to be considered effective. In addition, if specimens do not slake during

immersion, the treatment may be effective; and if no significant strength is lost due to

immersion, the treatment may be effective for water proofing soils.

The effect of binder content on unconfined compressive strength of TSCopt, at different times,

is shown in Figure9. It can be observed that different treatment leads to significant increase in

unconfined compressive strength especially after the 3rd day of conservation. These increases

are versus time, type and percentage of binder. According to this figure, the soil cemented with

Portland cement shows the highest unconfined compressive strength. However, the samples

treated with hydrated lime shows the lowest unconfined compressive strength. Surprisingly,

with 4% cement content, at 28th day of curing, a significant increase in unconfined

compressive strength in order to7 MPa close to those achieved with 8% hydrated lime content.

UCS ratio of treated compared to untreated samples, for each day, is summarised in Table 5.

Figure 9. Variation of unconfined compressive strength with type and content binder

A close examination of Figure 9, and table 4, reveals that with 8% binder content, and at 7th

day, the improvement in unconfined compressive strength of samples treated with cement is

more than twice compared to untreated samples. This improvement is achieved after two week

with mixed treatment. After less than 4week, at 28th day, which present the long term

behaviour in this study, the improvement in unconfined compressive strength with mixed

treatment is close than that obtained with cement treatment. However, the hydrated lime

treatment confers a good improvement, but more less than the other treatments. For the time

tested in this study, the mechanical strengths with mixed treatment are close than that obtained

with cement treatment.

0 4 80

2

4

6

8

10

12

Hydrated lime

Portland cement

Mixed

(At 3rd day)

UC

S (

MP

a)

Binder content (%)

0 4 80

2

4

6

8

10

12

Hydrated lime

Portland cement

Mixed

(At 7th day)

UC

S (

MP

a)

Binder content (%)

0 4 80

2

4

6

8

10

12

Hydrated lime

Portland cement

Mixed

(At 14th day)

UC

S (

MP

a)

Binder content (%)

0 4 80

2

4

6

8

10

12

Hydrated lime

Portland cement

Mixed

(At 28th day)

UC

S (

MP

a)

Binder content (%)

498


Table 4. Summary of unconfined compressive strength and unconfined compressive strength

ratio of treated samples compared to untreated samples for each day

Binder type Content

(%)

Unconfined compressive

strength (MPa)

UCS a d a

UCS a d a

3rd

day

7th

day

14th

day

28th

day

3rd

day

7th

day

14th

day

28th

day

Hydrated

lime

0

4

8

3.1

3.3

3.8

3.6

4.2

5.4

3.9

4.8

7.0

4.1

5.3

7.8

1.0

1.1

1.2

1.0

1.2

1.5

1.0

1.2

1.8

1.0

1.3

1.9

Portland

cement

0

4

8

3.1

3.8

5.4

3.6

5.5

7.4

3.9

6.2

9.9

4.1

7.2

10.5

1.0

1.2

1.7

1.0

1.5

2.1

1.0

1.6

2.5

1.0

1.8

2.6

Mixed

0

4

8

3.1

3.3

4.6

3.6

4.9

6.1

3.9

5.3

8.3

4.1

5.8

9.0

1.0

1.2

1.5

1.0

1.4

1.7

1.0

1.4

2.1

1.0

1.4

2.2

The immersion effect on unconfined compressive strength of treated and untreated specimens

is studies from the other set of specimens conserved for 28 days in the open air, and then

immersed in water for 1, 3 and 7 days prior to testing.

Figure 10 presents the state of TSCopt specimens after being immersed in water. It is noted

that untreated specimens are destroyed rapidly after being immersed in water and total strength

is lost due to immersion, by against the treated specimens are presented an area slightly

disintegrated. This disintegration is more marked for lime specimens treated. There is no

significant strength, of the treated specimens, lost due to immersion.

Untreated

specimens

Treated specimens

Figure 10. States of TSCopt specimens after being immersed in water

The immersion effect on unconfined compressive strength of treated and untreated specimens

is shown in Figure 11. Generally, the soaked treated samples present a significant increase in

strength. These increases are versus immersing time, the binder type and percentage of binder.

It can be observed that cement treatment leads to significant increase in unconfined more than

the other treatments. Surprisingly, soaked samples with 8% cement content exhibited

unconfined compressive strength about of 4.5 MPa greater than unsoaked untreated samples.

It can be explained by the fact that the moister content served at the sample preparation, was

not sufficient to hydrate all the quantity of binder during the 28 days of storage, and once the

samples are soaked, the hydration reaction was activated again and therefore the resistance has

increased.

499


Figure 11. Variation of unconfined compressive strength with type and content binder after

soaking

4. CONCLUSİONS

The main objective of this experimental work is to valorise local materials and industrial

wastes by using them in road engineering. It aims to show the possibility to improving the

mechanical proprieties of tuff by an economical treatment process using the waste of crunching

stations (limestone sand). An extensive laboratory-testing program was carried out to examine,

firstly, the influence of limestone sand on the mechanical properties of tuff. Secondly, the

treatment effect with hydraulic binders on the mechanical behaviour of the optimal tuff-

limestone sand mixture. The study included results of modified proctor, bearing and

unconfined compressive strength tests. Based on test results the following conclusions were

reached:

By increasing the amount of limestone sand in the tuff up to 40% the maximum dry density increased and the optimum water content decreased. Beyond this limit, the

maximum density and optimum water contents remained unchanged, and the

compactibility cannot be improved.

By increasing the amount of limestone sand in the tuff up to 30% and 40% for unsoaked and soaked specimens respectively, the CBR values increased for 50% and

reaching maximum values. This amount of limestone sand added permitted to gain on

average one bearing class.

The UCS, for each time, increased with amount of limestone sand in the tuff, and reached a maximum value corresponding to different limestone sand content varied

from 20% to 50%. These maximum UCS values are increased, with times, by

decreasing the amount of limestone sand in the tuff down to 20%. At long term (28th

day), this limit present an optimal limestone sand for which the compressive strength is

0 4 80.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Soaked for 1 day

Hydrated lime

Portland cement

Mixed

UC

S (

MP

a)

Binder content (%)

0 4 80.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Soaked for 3 days

Hydrated lime

Portland cement

Mixed

UC

S (

MP

a)

Binder content (%)

0 4 80.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Hydrated lime

Portland cement

Mixed

Soaked for 7 days

U

CS

(M

Pa)

Binder content (%)

500


maximum, which a gain of about 8% is produced in the mechanical strength.

The treatment with hydraulic binders increased optimum water content and decreased maximum dry unit weight of the soils. It indicates a marked increase in CBR values as

binder content increased. The bearing capacity of samples is improved, which CBR

value is 2 to 7 times higher than untreated samples. The soaked CBR values exhibited

greater values compared to unsoaked CBR values in a ratio of about two, except for

lime treatment soaked CBR values are smaller than unsoaked values.

The treatment leads to significant improvement in mechanical strength of the optimal tuff-limestone sand mixture (TSCopt). This improvement is versus type and content of

binder. Improvement in mechanical behaviours due to Portland cement treatment was

noticeably higher than other treatments. The mechanical strengths with low cement

content (4%) are close than that obtained with high lime content (8%). The mixed

treatment presents an economical treatment process that can confers at long term (for

the time tested in this study) an improvement equivalent to cement treatment.

With hydraulic binders treatment the specimens do not slake during immersion. For high cement content (8%), soaked samples exhibited unconfined compressive strength

greater than unsoaked untreated samples. In addition, the effect of type and content of

binder is clearer in wet condition compared to the dry state.

The results of this study have implications on improvement of mechanical behaviour of natural

tuff using both quarry waste (limestone sand) and hydraulic binders. In the term of using

quarry waste additives, the results shows that it is possible, at little cost, to improve mechanical

behaviour of the rough and abundant material, in the spirit of complementarity between the

economic constraints and environmental dimension. In the context of using hydraulic binder’s

additives, the results highlight the interest of treatment process with hydraulic binders in

significant improvement in the mechanical behaviour of the tuff-limestone sand mixture.

Therefore, while increase in strength can be achieved by cement treatment, high percentages of

cement should be used with extre²me caution in field applications. The binder contents must be

adjusted to take account of economic and technical constraints.

Finally, the experimental approach revealed the possibility of the use of local materials

containing tuff and quarry waste for the design of pavement and showed the interest of the

treatment process with hydraulic binders which is necessary in order to mitigate the problems

of non-stability in wet medium.

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Documents

THE USE OF INDUSTRIAL LIMESTONE WASTE IN SAHARAN …aim is to finding the optimal tuff-limestone sand mixture. Different formulations, of tuff-limestone mixtures, have been established