Mortar Based on Dune Sand and Substitute Wood Sawdust: Physico-Mechanical Characterization and Relationship Between Properties in Young Age

Mortar Based on Dune Sand and Substitute Wood Sawdust: Physico-Mechanical Characterization and Relationship Between Properties in Young Age

Assia Aidoud* Messaouda Bencheikh Nacera Khaldi Ilyess Mouhamed Ahmed Herga

Laboratory and Department of Civil Engineering and Hydraulics, University 8 May 1945 of Guelma, BP 401, Guelma 24000, Algeria

Department of Civil Engineering and Hydraulics, University 8 May 1945 of Guelma, BP 401, Guelma 24000, Algeria

Corresponding Author Email: 
aidoud.assia@univ-guelma.dz
Page: 
447-453
|
DOI: 
https://doi.org/10.18280/acsm.450603
Received: 
2 December 2021
|
Accepted: 
27 December 2021
|
Published: 
31 December 2021
| Citation

OPEN ACCESS

Abstract: 

The South of Algeria is known for these immense sand dunes, which cover part of its territory (Sahara). The main objective of this study is the recovery of sands dune and wood waste (sawdust). The latter, which constitutes a potential source of several environmental and economic problems. The objective of this present work is to characterize the physico-mechanical properties at a young age of a dune sand-based mortar lightened by wood waste and to examine the suitability of using it for various applications in the construction of buildings. The improvement of the characteristics of these sands, which essentially formed of sand untapped to date and with the sole aim of enhancing this national sand wealth. The formulation of the mixtures is based on the substitution of dune sand by sawdust, at different weight contents 0, 10, 20 and 30%. The quantity of cement is fixed at 450 g. The results obtained show firstly that the introduction of sawdust improves the characteristics of the mixture (grain size tends to be spread out, reduction in densities), and secondly the physico-mechanical characteristics, especially at 30% substitution (reduction absorption by total immersion of 20.50%, porosity of 28.32%, wet density of 1.73% and dry density of 14.94% and increase in tensile strength of 61.43% and in compression of 63.87%). The effect of sawdust on the relationships between the properties of mortars was clearly noted either for the relationships between early strengths or between compressive and tensile strengths.

Keywords: 

sawdust, mortar, absorption, porosity, resistance

1. Introduction

The evolution of the current world forces us to rethink construction methods. Indeed, today, the construction sector consumes a significant amount of energy. It is responsible for about a quarter of carbon dioxide emissions, not to mention the depletion of non-renewable resources. This sector must therefore innovate to limit its impact on the environment while guaranteeing user comfort [1]. Several investigations have been attempted with the aim of using overabundant sand from the dunes in the construction sector, particularly in Algeria and Africa, which have been the subject of research [2].

The universal need to protect the environment and manage natural resources well requires establishing new laws and adapting new concepts. The recovery of natural materials and the recycling of waste are an effective means in the face of the economic and ecological constraints of recent years [3]. Faced with the context of environmental protection and like all industrial and household waste, waste from wood processing industries will have to be recovered and valued [4]. Many products already exist on the market, but knowledge in this field is still limited and studies must be carried out in order to better understand certain mechanisms and improve the properties of these materials [5].

2. Experimental Details

The materials used for the preparation of the mixtures and the making of the various mortars are of local origin, whose preliminary characteristics are presented in Table 1. A witness sand mortar and three mortars composed in a manner substituted dune sand (DS) with different percentages of sawdust (0, 10, 20 and 30%) respectively. With a stabilization treatment of sawdust before mixing the mortar pastes. This treatment consists of soaking the wood residues in water for 24 hours before use, for each composition Table 2 were the subject of this comparative study at young age (7, 14, 21 and 28 days). The tests concerned the determination of some physico-mechanical properties of early-age mortars (porosity, absorption, wet and dry densities, compressive strength, tensile strength). All the tests were carried out on prismatic specimens (4 x 4 x 16) cm3. Keep in water after stripping until the days of the test.

The compression and tensile tests (by three-point bending) were carried out respectively by a press of 2000 kN capacity with speeds of 0.5 MPa/s and by a digital universal mechanical strength testing machine of 50 kN of capacity, load and controlled displacement. The measurements of the physical properties were carried out by a hydrostatic balance precision of 0.01 g.

Table 1. Physical characteristics of materials

Properties

Unit

Sand dune

sawdust

Cement

Finess modulus

(%)

1.83

Very difficult to achieve because of its shape

-

Sand equivalent (visual)

(%)

96.68

47

-

Sand equivalent (piston)

(%)

88.86

90.9

-

Apparent density

(g/cm3)

1.425

0.087

1.12

Absolute density

(g/cm3)

2.629

0,156

3.16

SSB

(cm2/g)

-

-

3630

Table 2. Composition of the mortars studied

Sawdust content (%)

MS0%

MS10%

MS20%

MS30%

dune sand (g)

1350

1215

1080

945

Ciment (g)

450

450

450

450

Water (g)

270

225

225

225

Sawdust (g)

0

7.085

14.17

21.26

W/C

0.6

0.5

0.5

0.5

3. Influence of Sawdust on the Physical Properties of Early Mortar

The different results of the physical properties are grouped together in Table 3 and illustrated by figures ‘Figure 1’, ‘Figure 2’, ‘Figure 3 and Figure 4’.

Table 3. Effect of sawdust on the physical properties of mortar at a young age

Properties

Time

7 days

14 days

21 days

28 days

Total immersion absorption (%)

MS0%

14,328±1,188

12,586±0,267

8,153±0,075

9,825±0,170

MS10%

12,986±0,174

12,733±0,406

9,17±0,085

8,999±0,662

MS20%

14,069±0,113

14,121±0,189

10,3±0,243

10,549±0,047

MS30%

11,507±0,836

13,324±1,306

9,489±1,699

7,811±1,273

Porosity (%)

MS0%

26,932±1,807

24,266±0,486

16,528±0,194

19,603±0,269

MS10%

22,114±0,620

22,107±0,496

16,413±0,185

16,421±0,772

MS20%

23,991±0,095

24,265±0,087

23,461±7,341

18,644±0,130

MS30%

19,883±0,739

21,736 ± 1,018

16,209±2,102

14,052±1,753

Wet bulk masses

(g/cm3)

MS0%

1,143±0,562

1,474 ± 0,490

1,082 ± 0,511

1,098 ± 0,518

MS10%

1,13 ± 0,531

1,385 ± 0,366

1,092 ± 0,515

1,09 ± 0,515

MS20%

1,41 ± 0,538

1,419 ± 0,392

1,148 ± 0,440

1,106 ± 0,522

MS30%

1,115 ± 0,542

1,35 ± 0,315

1,095 ± 0,482

1,079 ± 0,485

Volume masses dry (g/cm3)

MS0%

1,882 ± 0,825

1,928 ± 0,003

2,027 ± 0,957

1,996 ± 0,944

MS10%

1,703 ± 0,806

1,737 ± 0,039

1,79 ± 0,839

1,828 ± 0,870

MS20%

1,705 ± 0,815

1,719 ± 0,018

1,655 ± 1,031

1,765 ± 0,831

MS30%

1,732 ± 0,700

1,64 ± 0,090

1,724 ± 0,999

1,809 ± 0,965

Figure 1. Evolution of immersion absorption as a function of sawdust content at (7,14,21,28) days.

Figure 2. Evolution of porosity as a function of the sawdust content at (7,14,21,28) days

Figure 3. Evolution of the wet densities as a function of the sawdust content at (7,14,21,28) days

Figure 4. Evolution of dry densities as a function of the sawdust content at (7,14,21,28) days

3.1 Total immersion absorption and porosity

From “Figure 1” MS10% showed less absorption than MS0% at 7 and 28 days and moderately greater than MS0% at days 14 and 21, this decrease in absorption is due firstly to the presence of sawdust with their sizes larger than that of dune sand and secondly to the phenomenon of cement hydration and the composition of ettringites. On the other hand, the absorption of MS20% is always higher compared to other mortars except at 7 days it marked a slightly less absorption than that of MS0% at this age. Tend says that MS30% had the lowest absorption of other mortars at 7 and 28 days and greater than that of MS0% at 14 and 21 days.

From "Figure 2" MS10% and MS30% showed less porosity than MS0% on days 7-28. While MS20% scored less porosity than MS0% at 7 and 28 days to equal it at 14 days and score the greatest porosity at 21 days.

3.2 Wet and dry density

From 'Figure 3' The wet density of MS20% is always higher than those of other mortars except at 14 days it marked a wet density less than that of MS0% and greater than those of MS10% and MS30%. MS10% and MS30% mortars consistently scored less wet densities than MS0% and slightly higher than the latter at 21 days.

From "Figure 4" The dry densities of the three mortars (MS10%, MS20%, MS30%) marked consistently lower values than those of MS0%.

4. Influence of Sawdust on the Mechanical Properties of Early Mortar

The various results of the mechanical properties are grouped together in Table 4 and illustrated by figures ‘Figure 5 and 6’.

Table 4. Effect of sawdust on the mechanical properties of mortar at young age

Properties

Time

7 days

14 days

21 days

28 days

 

Compressive strength (MPa)

MS0%

18,782 ± 6,286

31,697 ± 5,594

25,085±4,559

18,033 ± 2,148

MS10%

19,203 ± 2,687

23,328 ± 2,267

21,96±2,655

19,485±1.643

MS20%

20,258 ± 2,106

24,072 ± 3,496

22,527±2,284

20,717±0.961

MS30%

24,278 ± 5,709

17.065 ± 2.279

24,143±1,259

29,55±1.907

Tensile strength (MPa)

MS0%

4,917 ± 1,350

6,883 ± 0,536

4,901 ± 0,319

3,145 ± 0,176

MS10%

5,516 ± 0,616

5,48 ± 0,236

3,545 ± 0,614

4,274 ± 0,434

MS20%

5,518 ± 0,125

5,963 ± 0,107

3,6 ± 0,860

4,877 ± 0,131

MS30%

7,341 ± 1,166

6,007 ± 0,841

4,427 ± 0,794

5,077 ± 0,669

Figure 5. Effect of adding sawdust on compressive strength at (7,14,21 and 28) days

Figure 6. Effect of adding sawdust on tensile strength at (7,14,21 and 28) days

4.1 Résistance à la Compression et à la Traction

According to 'Figure 5' The pace of the evolution of the compressive strength of mortars (MS10%, MS20%) as a function of time is the same with values slightly higher than those of MS0% to 7 and 28 days, and generally less than 14 and 21 days. On the other hand, that of MS30% is inversely to that of MS0% with a remarkable difference at 7 days and very remarkable at 14 and 28 days to mark almost the same resistance at 21 days. The values of the compressive strengths without sawdust or with sawdust show higher values compared to those found by Kameni Kamga [6] because the latter used reverie sand and another method of treating sawdust. On the other hand, my resistance values without less than that of the study by Ndong Engoned [7] that can be explained by its method of treatment by smoothing.

According to 'Figure 6' The pace of the evolution of the tensile strength of the three mortars (MS10%, MS20%, MS30%) as a function of time is the same with values greater than those of MS0% at 7 and 28 days and less than 14 and 21 days.

5. Effect of Wood Waste on the Relationship Between Mortar Properties

The relationships between early age strengths (compressive and tensile) and characteristic 28 days strengths can be influenced by the substitution of sand by sawdust. It has been observed through the results of these properties that they can present different values. In this part of the work, we explore the effect of sawdust content on these relationships at different ages, for compressive strengths and even for tensile strengths. These relationships between resistances are also situated in relation to those given by the regulations in force (BAEL [8], EC2 [9]).

  • For the relationships between the compressive strengths at a young age and the characteristic strengths at 28 days, the following formulas Eq (1) were used; Eq (2) and Eq (3):

From « BAEL [8] »

$\mathrm{f}_{\mathrm{Cj}}=\frac{\mathrm{j}}{4,76+0,83 \mathrm{j}} \mathrm{f}_{\mathrm{C}_{28}}$              (1)

For fc28 ≤ 40 MPa

From « EC2 [9] »

$\mathrm{f}_{\mathrm{cm}}(\mathrm{t})=\beta_{\mathrm{cc}}(\mathrm{t}) \mathrm{f}_{\mathrm{cm}}$          (2)

With $\quad \beta_{\mathrm{cc}}(\mathrm{t})=\exp \left[\mathrm{s}\left[1-\left(\frac{28}{\mathrm{t}}\right)^{1 / 2}\right]\right]$             (3)

Or

"s": is a coefficient which takes different values depending on the class of the cement, in which it is taken equal to 0.25 for our case (Cement CEM 42.5 N).

"fcm": Average compressive strength at 28 days.

  • And in the same way for the relations between tensile strengths at young age and characteristic strengths at 28 days.

  •  For the relationships between compressive strengths and tensile strengths Eq (4) and Eq (5).

From « BAEL [8] »

$\mathrm{f}_{\mathrm{tj}}=0,6+0,06 \mathrm{f}_{\mathrm{Cj}}$              (4)

From « EC2 [9] »

$\mathrm{f}_{\mathrm{ti}}=0,30(\mathrm{fcj})^{2 / 3}$           (5)

5.1 Relationships between compressive strengths at young age and characteristic strengths at 28 days

The results are grouped together in the Table 5 below and shown diagrammatically in the Figures 7-9, which follow.

Table 5. Compressive strengths at (7, 14 and 21) days as a function of sawdust content

Sawdust content

0%

10%

20%

30%

Cs7d

18,782

19,203

20,258

24,278

Cs7d (BAEL)

11,902

11,452

12,223

16,779

Cs7d (EC)

14,764

14,176

15,111

20,744

Cs14d

31,697

23,328

24,072

17.065

Cs14d (BAEL)

15,413

14,830

15,775

21,655

Cs14d (EC)

16,599

15,972

16,990

23,323

Cs21d

23,418

19,352

15,527

24,143

Cs21d (BAEL)

17,066

16,420

17,467

23,978

Cs21d (EC)

17,895

16,822

17,895

24,565

The values of the compressive strength at 7 days are higher than those of BAEL [8] and EC2 [9] for the different sawdust contents.

The values of the compressive strength at 14 days are higher than those of BAEL [8] and EC2 [9] except for the sawdust content of 30%.

The values of the compressive strength at 21 days are lower than those of BAEL [8] and EC2 [9] for the sawdust contents of 20% and 30% and higher for the other two contents 0% and 10%, but the most remarkable which is closer for the latter.

Figure 7. The relationships between the 7-day compressive strengths and the characteristic 28-day strengths as a function of the sawdust content

Figure 8. The relationships between the 14-day compressive strengths and the 28-day characteristic strengths as a function of the sawdust content

Figure 9. The relations between the compressive strengths at 21 days and the characteristic strengths at 28 days as a function of the sawdust content

5.2 Relationships between early tensile strengths and characteristic 28-day strengths

The results are grouped together in the Table 6 below and shown diagrammatically in the Figures 10-12 which follow.

Table 6. Tensile strengths at (7, 14 and 14) days as a function of sawdust content

Sawdust content

0%

10%

20%

30%

Ts7d

4,917

5,516

5,518

7,341

Ts7d (BAEL)

2,076

2,821

3,219

3,351

Ts7d (EC)

2,575

3,499

3,993

4,157

Ts14d

6,883

5,48

5,963

6,007

Ts14d (BAEL)

2,673

3,633

4,145

4,315

Ts14d (EC)

2,895

3,934

4,489

4,673

Ts21d

4,901

3,545

3,6

4,427

Ts21d (BAEL)

2,975

4,043

4,614

4,803

Ts21d (EC)

3,049

4,144

4,728

4,922

Figure 10. The relationship between the tensile strengths at 7 days and the characteristic strengths at 28 days as a function of the sawdust content

Figure 11. The relationship between the tensile strengths at 14 days and the characteristic strengths at 28 days as a function of the sawdust content

The values of the tensile strength at 7 days are higher than those of BAEL [8] and EC2 [9] for the different sawdust contents.

The values of the tensile strength at 14 days are higher than those of BAEL [8] and EC2 [9] for the different sawdust contents especially at 0%.

Figure 12. The relationship between the tensile strengths at 21 days and the characteristic strengths at 28 days as a function of the sawdust content

The values of the tensile strength at 21 days are lower than those of BAEL [8] and EC2 [9] for the sawdust contents of 10%, 20% and 30% and higher for the content 0%.

5.3 The relationships between compressive strengths and tensile strengths

The results are grouped together in the Table 7 below and shown diagrammatically in the Figures 13-16 which follow.

The curves for the experimental results are trend lines. And the curves of the results calculated by the formulas of BAEL and EC2 are curves following these formulas.

Table 7. Compressive and tensile strengths as a function of sawdust content at (7, 14, 21 and 28) days

Age

Sawdust content

0%

10%

20%

30%

7 jours

Cs (MPa)

18,782

19,203

20,258

24,278

Ts (MPa)

4,917

5,516

5,518

7,341

Ts (BAEL)

1,727

1,752

1,815

2,057

Ts (EC 2)

2,120

2,151

2,229

2,515

 

14 jours

Cs (MPa)

31,697

23,328

24,072

17,065

Ts (MPa)

6,883

5,480

5,963

6,007

Ts (BAEL)

2,502

2.000

2,044

2,041

Ts (EC 2)

3,005

2,449

2,501

2,497

21 jours

Cs (MPa)

23,418

19,352

15,527

24,143

Ts (MPa)

4,901

3,545

3,600

4,427

Ts (BAEL)

2,005

1,761

1,532

2,049

Ts (EC 2)

2,456

2,162

1,867

2,506

28 jours

Cs (MPa)

18,033

19,485

20,717

29,55

Ts (MPa)

3,145

4,274

4,877

5,077

Ts (BAEL)

1,682

1,769

1,843

2,373

Ts (EC 2)

2,063

2,172

2,263

2,867

Figure 13. Relationship between compressive strengths and 7-day tensile strengths

Figure 14. Relationship between compressive strengths and tensile strengths at 14 days

The preceding curves show the Ts-Cs relationships for MSs with different sawdust content (0%, 10%, 20%, 30%) at 7, 14, 21 and 28 days. We notice that the differences between the regulatory curves and the experimental curves of the MS are very important with very acceptable regression qualities Ts-Cs (R2 = 0.9628, R2 = 0.7956, R2 = 0.9007 and R2 = 0.9974) respectfully at (7, 14, 21 and 28) days. These relationships always give overestimated values compared to those of the regulations.

It can be seen that the Rt-Rc relationships are influenced by the sawdust content at different ages.

Figure 15. Relations between compressive strengths and tensile strengths at 21 days

Figure 16. Relationship between compressive strengths and tensile strengths at 28 days

6. Conclusions

The absorption by total immersion has a maximum decrease of the order of 19.69% compared to MS0% for (MS30%) at 7 days, and a gradual increase at 14 and 21 days especially for MS20% of the order (12.20% and 26.33%) compares to MS0% and respectively to age. Most notable, at 28 days, was the decrease in total immersion absorption of MS30% of around 20.50% compared to that of (MS0%).

At 7, 14 and 28 days the maximum decrease in porosity was for (MS30%) respectively of the order of (26.17%, 10.43%, 28.32%) compared to (MS0%). On the other hand at 21 days (MS20%) marked an unfavorable increase.

The largest decreases in Wet Density were for (MS30%) on the order of (2.45%, 8.41%, 1.73%) at (7, 14, 28 days) respectively compared to that of (MS0%).

At 7 days the decreases in Dry Density were almost identical to reach 14.94% as the maximum values at 14 days for (MS30%) compared to that of (MS0%). However, the (MS20%) marked the maximum values (18.35%, 11.57%) respectively at (21 and 28 days) compared to that of (MS0%).

The tensile strength of (MS30%) increased by almost 50% compared to that of (MS0%) at 7 days, and that of (MS20%) decreased by an order of (13.37%, 27.67%) respectively at (14 and 21 days) compared to that of (MS0%), in order to increase for the three mortars (61.43%) for (MS30%) compared to that of MS0%.

At 7 days the compressive strength increased in proportion to the sawdust content with an average factor of (1.09), to decrease at 14 days by almost half (46.16%) for (MS30%) of the strength of MS0 %. At the end it increased by around (63.87%) at 28 days compared to that of the MS0%.

The relationships between the strengths either in tension and in compression at the young age and the characteristic strengths at 28 days are influenced at any age either by values higher or lower than those of the regulations.

The relationships between compressive strengths and tensile strengths are influenced by the sawdust content at different ages.

The correlations between the compressive strengths and the tensile strengths which appear in the regulatory documents (BAEL, EC2) valid for common mortars and concretes are no longer so in our case. Other parameters such as composition and sawdust content as well as age, which have been studied in this work, must be considered in these relationships.

Acknowledgment

The authors thank the LGCH research laboratory at the University 8 May 1945 (Guelma) and the pedagogical laboratory of the civil and hydraulic engineering department (Guelma) for their technical support during the experimental work.

Nomenclature

DS

dune sand

SSB

specific surface of Blaine, cm2.g-1

W/C

Water Cement Ratio

MS

Mortar with different % sawdust

f

Resistance

s

Coefficient which takes different values depending on the class of the cement

t

Time (age), days

CEM

Portland cement type

Cs

Compressive strength, MPa

Ts

Tensile strength, MPa

Greek symbols

$\beta$

Coefficient which takes different values depending on the time (age)

Subscripts

cj

Compressive at ‘j’ days

c28

Compressive at ‘28’ days

tj

Tensile at ‘j’ days

cm

Medium compressive

  References

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[8] BAEL 91 rules (DTU P 18-702) (revised February 99, 2000) Technical rules for the design and calculation of reinforced concrete structures and structures using the limit states method Fascicle 62, title 1 of the CCTG - Works section 1: reinforced concrete 1. http://www.sodibet.com/telechargement/BAEL%2091%20R%2099.pdf.

[9] Eurocode 2 (ENV 1992-1-2): Design of concrete structures, Part 1-2: General rules - calculation of fire behavior. February 2001. http://www-lmdc.insa-toulouse.fr/pres/mastergc/telechargement/pedagogie/EC2_M2P_COAB_Multon_2012.pdf.