Construction and Building Materials 23 (2009) 1035–1041

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Construction and Building Materials

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Sound insulation of fibre reinforced mud brick walls

Hanifi Binici a,*, Orhan Aksogan b, Derya Bakbak a, Hasan Kaplan c, Bilge Isik d

a Kahramanmaras Sutcu Imam University, Department of Civil Engineering, Avsar Campus, Kahramanmaras, Turkeyb Cukurova University, Department of Civil Engineering, Adana, Turkeyc Pamukkale University, Department of Civil Engineering, Denizli, Turkeyd Istanbul Technical University, Department of Architecture, Istanbul, Turkey

a r t i c l e i n f o

Article history:Received 7 November 2007Received in revised form 1 May 2008Accepted 6 May 2008Available online 26 June 2008

Keywords:Sound insulationFibreReinforced mud bricks

0950-0618/$ - see front matter � 2008 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2008.05.008

* Corresponding author. Tel.: +90 344 2191051; faxE-mail addresses: hbinici@ksu.edu.tr (H. Binici), aks

bakbakderya@yahoo.com.tr (D. Bakbak), hkaplan@pabilge.isik@kerpic.org (B. Isik).

a b s t r a c t

The aim of this paper is to find a better alternative for the insulation of industrial noise and to improvethe mechanical properties of fibre reinforced mud bricks. It was observed that the fibre reinforced mudbricks fulfill the compressive strength and sound insulation requirements of the ASTM and Turkish Stan-dards. Basaltic pumice as an ingredient was found to improve the sound insulation performance of fibrereinforced mud bricks. The experimental results showed that fibre reinforced mud brick, with basalticpumice as ingredient, can be used in industrial buildings for walls to improve sound insulation.

� 2008 Elsevier Ltd. All rights reserved.

1. Introduction

Mud bricks have been used in the construction of shelters forthousands of years and approximately 30% of the world’s presentpopulation still lives in earthen structures [1]. Earth is a cheap,environmentally friendly and abundantly available building mate-rial. It has been used extensively for wall construction around theworld and particularly in developing countries [2]. Sustainableconstruction is using natural resources in such a way as to meeteconomic, social and cultural needs, but not depleting or degradingthese resources to such an extent that they cannot meet theseneeds for future generations [3].

Mud brick-makers of Turkey and the Middle East have longbeen using fibrous ingredients like straw to improve the tensilestrength of mud bricks [4].

The compressive strength of fibre reinforced mud bricks wasfound to be higher than that of concrete bricks. Moreover, the pres-ence of fibres in mud bricks has been reported to provide flexibilityto structures by Binici et al. [5]. In another study of the foregoingauthors the fibre reinforced mud bricks are reported to fulfill thecompressive strength and heat conductivity requirements of theASTM and Turkish Standards [6]. It is also mentioned that the fibrereinforced mud brick house has been found to be superior to theconcrete brick house for keeping indoor temperatures stationaryduring the summer and winter. The European Standard EN

ll rights reserved.

: +90 344 2191052.ogan@cu.edu.tr (O. Aksogan),mukkale.edu.tr (H. Kaplan),

12354-3 [7] describes a calculation method designed to estimatethe reduction of outdoor sound by facades or other external sur-faces of buildings.

Sound insulation of building parts, such as walls, roofs anddoors, reducing the rate of noise in the houses is very important.There are many different methods for measuring sound insulation[8–10]. In the present study, the noise insulation of industrialbuildings is investigated. In small cities and districts in Turkeymany small industrial structures are made as a type project(Fig. 1). In these buildings, people are working under high levelsound. In the walls of these buildings the use of briquettes gener-ally causes serious health problems.

The present research examines five different types of bricks ineleven different walls of small industrial buildings. Three of the fi-bre reinforced mud bricks are made with plastic, polystyrene andstraw. The remaining ones are concrete and fired bricks. Further-more, the sound insulation effect of basaltic pumice as ingredientin reinforced mud bricks was also investigated.

2. Materials and methods

2.1. Materials

The materials used in this study for fibre reinforced mud brickproduction were clay as the main matrix, cement, basaltic pumiceand gypsum as the stabilisers and plastic fibre, straw and polysty-rene fabric as the fibrous materials.

The basaltic pumice cone deposits are of Quaternary age and arelocated in southern Turkey. The pumice comprises an average of

Fig. 1. Small industrial building.

Table 1Chemical content of the cement, basaltic pumice and gypsum used in the study (%)

Oxides Cement Basaltic pumice Gypsum

SiO2 20.1 43.9 Insoluble SiO2

0.55Al2O3 5.2 14.1

Al2O3 + Fe2O3

Fe2O3 3.9 12.1 0.83

CaO 64.1 9.3MgO + CaO

MgO 2.2 8.9 87.56Na2O + K2 1.4 0.3 0.75OSO3 1.2 – 0.83LI (Loss of ignition) 0.5 0.5 2.17Insoluble residue – – –

Table 2Chemical and physical properties of the clay used in this study [11]

Particle sizes Water soluble cation (meq/l) Water

Sand Silt Clay Ca+ Mg+ Na+ K+ HCO�343.44 24.52 32.04 3.5 3.7 0.31 0.31 4.28Chemical compositionSiO2 Al2O3 Fe2O3 CaO M52.40 25.12 7.95 1.42 2.4

Table 3Designations of mixtures

Mix designation Composition of bodies of fibrous mud bricks

SA1 Clay + plastic fibre + basaltic pumice + waterSA2 Clay + plastic fibre + cement + waterSA3 Clay + plastic fibre + gypsum + waterSB1 Clay + straw + basaltic pumice + waterSB2 Clay + straw + cement + waterSB3 Clay + straw + gypsum + waterSC1 Clay + polystyrene fabric + basaltic pumice + waterSC2 Clay + polystyrene fabric + cement + waterSC3 Clay + polystyrene fabric + gypsum + water

1036 H. Binici et al. / Construction and Building Materials 23 (2009) 1035–1041

85% volcanic glass and 15% phenocrystic feldspars along with min-or hematite minerals, determined by microscopy. XRD analysesshow the presence of dominant illite and kaolinite as clay mineralsalong with feldspar. The high porosity of the basaltic pumice is anadvantage for easy and economical crushing [11].

For the materials used in this study, the chemical compositionsof the cement, basaltic pumice and gypsum are given in Table 1and the chemical and physical properties of the clay are given inTable 2.

2.2. Methods

2.2.1. Mixing of raw materialsThe materials used, mentioned in Table 3, were added to the

mixture with the proportions given in Table 4 to obtain three dif-ferent specimen groups and mixed thoroughly in dry state. Waterwas added and the ingredients were further mixed thoroughly bykneading until the mass attained a uniform consistency.

2.2.2. Preparation of brick wallsThe size of the fibre reinforced mud bricks and the concrete

bricks to be used in the sound absorption tests were selected as150 mm � 150 mm � 150 mm in accordance with the EN TS [12].The mixture for both mud and concrete bricks were placed in woodmoulds, where they were compacted by vibration. Plan and crosssection of the industrial project are given in Figs. 2 and 3,respectively.

2.2.3. Testing of mud bricksThe mud bricks were taken out from the moulds, covered with

wet gunny bags and allowed to cure for a week. They were testedfor compressive strength after 30 days. The test results were foundas the average of the compressive strengths of five specimens. Indi-vidual variations of more than ±5% of the average were not consid-ered in calculating the average values.

2.2.4. Acoustic properties of the wallsAcoustic measurements of sound insulation in industrial build-

ings made with fibre reinforced mud bricks, concrete bricks andred bricks were performed according to the EN TS 415 [12]. Theforegoing standard specifies field methods for measuring the air-borne sound insulation properties of interier walls between tworooms. Sound absorption coefficients of the samples were mea-

soluble anion (meq/l) Density (g/cm3) Permeability (cm sn)

CO�3 CL� SO�4 1.278 1.8 � 10�17

0.44 1.3 4.49

gO SO4 K2O TiO2 LI5 0.64 4.27 0.70 3.6

Table 4Mixture proportions

Mix designations Components (kg)

Clay Cement Basaltic pumice Gypsum Plastic fibre Straw Polystyrene fabric Water

SA1 60 – 10 – 0.2 – – 20SA2 60 10 – – 0.2 – – 20SA3 60 – – 10 0.2 – – 20SB1 60 – 10 – – 2 – 20SB2 60 10 – – – 2 20SB3 60 – – 10 – 2 – 20SC1 60 – 10 – – – 0.6 20SC2 60 10 – – – – 0.6 20SC3 60 – – 10 – – 0.6 20

Fig. 2. Plan of small industrial building.

Fig. 3. Cross section of small industrial building.

H. Binici et al. / Construction and Building Materials 23 (2009) 1035–1041 1037

sured under the same humidity conditions. The relative humiditywas 50% and the frequency of the sound was between 100 and

1800 Hz. The small industrial buildings tested in this work wereof equal dimensions. The sound used in the test was a norm oneproduced in a welder room. The sound level was 100, 200, 250,315, 400, 500, 600, 800, 1000, 1250 and 1800 Hz and 1/3 octave fil-ters were used.

2.2.5. Sound absorption coefficientsSound absorption coefficients of reinforced mud concrete, and

fired brick boards were measured using the impedance tube methodASTM C 384-98 [13] to determine the insulation properties to beused in the design of insulation boards in brick wall constructions.

3. Results and discussion

3.1. Mechanical properties

The compressive strength values of the fibre reinforced mudbricks tested in the present study vary from 3.4 to 5.1 N/mm2

Table 5The characteristics of compressive strength and physical properties of bricks

Mixdesignations

Compressivestrength (MPa) – 30days

Waterabsorption after24 h (%)

Loss of weightafter 7 days(%)

Density(gr/cm3)

SA1 4.2 1.245SA2 5.2 30.2 13.0 1.266SA3 3.9 1.279Average 4.4 1.263SB1 3.5 1.248SB2 4.1 32.6 13.6 1.257SB3 3.7 1.255Average 3.7 1.253SC1 3.9 1.251SC2 4.1 33.4 13.4 1.271SC3 3.8 1.258Average 3.9 1.260Concrete

brick2.1 33.7 15.4 1.290

Fired brick 6.4 11.2 6.4 1.425

50

55

60

Spec

dB

Fibre reinforced mud brick group A

Fibre reinforced mud brick group B

Fibre reinforced mud brick group C

Concrete Brick

Fired Brick

Fig. 4. Sound frequency-dB

10

20

30

40

50

60

100 400 700

Freque

dB

Fired Brick Concrete Brick

Fig. 5. Sound frequency-dB relation of group A fibre reinforced m

1038 H. Binici et al. / Construction and Building Materials 23 (2009) 1035–1041

and are much higher than the those required by the EN TS 2415 fortraditional mud bricks, which is 0.5–1 N/mm2 (Table 5). In practi-cal terms this means that using fibre reinforced mud bricks thethickness of the outer load bearing walls can be reducedsubstantially.

The highest compressive strength at all ages has been found forthe plastic fibre specimen. Considering the average compressivestrength of the early age specimens, the compressive strength ofgroup SA were found to be 16% higher than that of group SB and12% higher than that of group SC (Table 5). The compressivestrength was highest in the fired brick.

Specimens, with higher water absorbances had higher densitiesand weight losses than the others. The effects of stabilisers on thecompressive strengths of different groups were found to be differ-ent. Specimen SA2 had the highest compressive strength whichwas 16% higher than that of SA1 and 24% higher than that of A3(Table 5). The compressive strengths of the fibre reinforced mudbricks were about two times that of the concrete bricks.

imens

relation of brick walls.

900 1800

ncy (Hz)

A1 A3 A2

ud brick, basaltic pumice concrete brick and fired brick walls.

10

20

30

40

50

60

100 400 700 900 1800

Frequency (Hz)

dB

Fired Brick Concrete Brick B1 B2 B3

Fig. 6. Sound frequency-dB relation of group B fibre reinforced mud brick, basaltic pumice concrete brick and fired brick walls.

10

20

30

40

50

60

100 400 700 900 1800Frequency (Hz)

dB

Fired Brick Concrete Brick C1 C2 C3

Fig. 7. Sound frequency-dB relation of group C fibre reinforced mud brick, basaltic pumice concrete brick and fired brick walls.

1.2

1.25

1.3

1.35

1.4

1.45

Specimens

Den

sity

(gr/c

m3 )

Fibre reinforced mud brick group A

Fibre reinforced mud brick group B

Fibre reinforced mud brick group C

Concrete Brick

Fired Brick

Fig. 8. The variations of density and dB coefficient for the bricks.

H. Binici et al. / Construction and Building Materials 23 (2009) 1035–1041 1039

1040 H. Binici et al. / Construction and Building Materials 23 (2009) 1035–1041

3.2. Sound insulation

The experiments showed that basaltic pumice in bricks in-creased the absorption coefficient of these walls. The results are gi-ven in Figs. 4–11 and Table 6. The decrease of the sound absorptionis most probably due to the high porosity of the basaltic pumice asstated by Kelling et al. [11].

Yilmazer and Ozdemir reported that the addition of some fibresinto the mixture for making perlite plates improved a number offeatures [14]. This study showed that some stabilisers and fibresincreased the durability, as well as the sound absorption coeffi-cients. The authors also reported that larger pores improved theacoustic properties of the perlite plates. Likewise, in the presentstudy, composite boards with plastic fibres and polystyrene fabrichad higher sound absorption coefficients than the others. Speci-

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

100 400Frequ

Fired Brick

Concrete Brick

Fibre reinforced mud brick group A1

Fibre reinforced mud brick group B1

Fibre reinforced mud brick group C1

Sou

nd a

bsor

ptio

n co

effic

ient

Fig. 9. Sound absorption coefficients of b

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

100 400Frequ

Fired Brick

Concrete Brick

Fibre reinforced mud brick group A2

Fibre reinforced mud brick group B2

Fibre reinforced mud brick group C2

Sou

nd a

bsor

ptio

n co

effic

ient

Fig. 10. Sound absorption coefficients

mens with basaltic pumice had higher sound absorption coeffi-cients than the others.

Specimens SA1, SB1 and SC1 showed lower sound absorptioncoefficients than the others in the 100–1800 Hz frequency range.The sound absorption coefficients of fibre reinforced mud bricks in-creased as the frequency increased. However, they decreasedaround the frequency of 100 Hz and increased again. In addition,the concrete and fired bricks showed decreasing sound absorptioncoefficients as the frequency increased. This can be explained bytheir specific characteristic of absorbing sound in the low fre-quency range but reflecting it in the middle and high frequencyranges. The present research showed that the sound insulation offibre reinforced mud brick walls can be accomplished by addingbasaltic pumice in the production of mud bricks.

800 1000 1800ency (Hz)

ricks (with basaltic pumice content).

800 1000 1800ency (Hz)

of bricks (with cement content).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

100 400 800 1000 1800

Frequency (Hz)

Sou

nd a

bsor

ptio

n co

effic

ient

Fired Brick

Concrete Brick

Fibre reinforced mud brick group A3

Fibre reinforced mud brickgroup B3

Fibre reinforced mud brick group C3

Fig. 11. Sound absorption coefficients of bricks (with gypsum content).

Table 6The measured sound levels (dB)

Mix designation of specimens Frequency (Hz)

100 200 250 300 400 500 600 800 1000 1250 1800

SA1 4 10 12 18 21 25 29 32 36 43 52SA2 4 11 13 19 20 24 28 31 35 42 51SA3 3 10 11 17 19 23 27 30 34 41 50SB1 5 11 13 20 22 26 30 35 39 49 53SB2 4 12 14 19 20 25 29 34 38 48 52SB3 5 11 13 18 19 24 28 33 37 47 51SC1 6 12 14 21 24 27 31 36 41 52 54SC2 6 12 14 20 23 26 30 35 40 51 53SC3 5 11 13 19 22 25 29 34 39 50 52Concrete brick 15 18 20 24 28 32 45 55 56 57 58Fired brick 16 19 25 29 24 27 32 43 47 58 59

H. Binici et al. / Construction and Building Materials 23 (2009) 1035–1041 1041

4. Conclusion

The fibre reinforced mud bricks, especially the group SA speci-mens, have been found to fulfill the compressive strength require-ments of the ASTM and Turkish Standards. The basaltic pumice, asan ingredient, was found to improve the sound insulation perfor-mance of fibre reinforced mud bricks, specimen SA1 yielding thebest result. A decrease in density improved the sound insulationperformance. Moreover, the fibre reinforced mud brick industrialbuilding has been found to be superior to the one made with basal-tic pumice, in this respect. This is most probably due to the highporosity of the basaltic pumice. Finally, it can be concluded that fi-bre reinforced mud brick, with basaltic pumice as ingredient, canbe used in industrial buildings for walls to improve sound insula-tion. Thus, this experimental study has shown that using variousingredients in mud bricks decreases the effect of noise on workersin industrial buildings.

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