Lightweight Concrete Mixed with Superfine Crumb

297

วารสารวิชาการพระจอมเกล้าพระนครเหนือ ปีที่ 19 ฉบับที่ 3 ก.ย. - ธ.ค. 2552 The Journal of KMUTNB., Vol. 19, No. 3, Sep. - Dec. 2009

Lightweight Concrete Mixed with Superfine Crumb

Rubber Powder Part 1: Insulation Properties

Piti Sukontasukkul1*and Somyot Wiwatpattanapong2

บทคัดย่อ ในการศึกษาครั้งนี้ คอนกรีตมวลเบาผสมด้วยผง

ยางรถยนต์ชนิดละเอียดมากจะถูกนำมาศึกษาโดยเน้นในส่วนของคุณสมบัติการเป็นฉนวน ผงยางที่นำมาใช้ผลิตจากโรงงานแปรรูปยางรถยนต์ เก่าเพื่อใช้ ในอุตสาหกรรม เช่น งานถนนราดยาง บล็อกยาง วัสดุอุดรอยร้าว เชิงเพลิงทางเลือก เป็นต้น จากกระบวนการผลิตด้วยวิธีการบดละเอียดทำให้ได้ขนาดต่างๆ กัน ตั้งแต่หลายมิลลิเมตรไปจนถึงระดับไมครอน ขนาดเล็กสุดอยู่ที่ประมาณ 500-600 ไมครอน ในการทดลองนี้จะนำขนาดที่ เล็กที่สุดมาใช้ผสมคอนกรีต โดยจะแทนที่มวลรวมละเอียดในสัดส่วน 10% 20% และ 30% โดยน้ำหนัก บทบาทหลักของเม็ดยางเป็นการแทนที่มวลรวมละเอียดทำให้คอนกรีตมีหน่วยน้ำหนักเบา แต่เนื่องจากขนาดของเม็ดยางที่เล็กนี้ ทำให้เม็ดยางเข้าไปแทรกตัวอยู่ในเนื้อคอนกรีตและรวมถงึอดุชอ่งวา่งตา่งๆ สง่ผลใหค้อนกรตีมคีวามสามารถในการดูดซึมและช่องว่างลดลง และมีคุณสมบัติฉนวนด้านเสียงและอุณหภูมิที่ดีขึ้น

คำสำคัญ: ผงยางชนดิละเอยีดมาก คณุสมบตัดิา้นเสยีง

และอุณหภูมิ

Abstract

In this study, insulation properties of lightweight

concrete mixed with commercialized superfine crumb

rubber powder is investigated. Crumb rubber

produced from rubber reclaimed plant has been used

widely in several applications such as pavement,

blocks, rubber tiles, sealant, supplement fuel etc.

Because of the grinding during the manufacturing,

crumb rubbers are found in various sizes from several

millimeters to microns. The smallest size is about 500

to 600 micron. In this experiment, the superfine

crumb rubbers are mixed with concrete by replacing

fine aggregate at the rate of 10%, 20% and 30% by

weight. The main role of crumb rubbers powder is to

replace fine aggregates to produce lightweight

concrete. However, because of its small diameter and

dense property, crumb rubber powder will also act as

a filler to fill small voids in concrete to reduce water

absorption and porosity. Also, the decrease in density

results in better thermal and sound properties.

Keywords: Superfine Crumb Rubber, Sound and

Thermal Properties

1 Associate Professor, Department of Civil Engineering, Faculty of Engineering, King Mongkut’s

University of Technology North Bangkok. 2 Student, Department of Civil Engineering, Faculty of Engineering, King Mongkut’s University of

Technology North Bangkok.

* Corresponding Author, Tel.0-2913-2500, Ext. 8625, E-mail: [email protected]

Received October 16, 2008; Accepted July 20, 2009

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1. Introduction 1.1 Manufacturing Crumb Rubber

Abandoned tires has been a waste problem around the world, millions ton of tires are being

discarded every year. In Thailand, total consumption of rubber products was about 242 metric tons, this number included about 90 metric tons of vehicle

tires [1]. One way to recycle them is to grind them into small particles. Crumb rubber is widely accepted and found it ways into several applications

such as asphalt, sealants, rubber sheets or mix with cementitious materials like concrete.

In Thailand, the manufacturing of commercialized

crumb rubbers consists of three steps (Figure 1). The first step is to cut and sort out the grindable parts (parts without radial steels). Next, the rubber pieces

are fed into series of cutting wheels several times until the desired size is achieved. Finally, crumb rubbers are sorted out according to the particle size.

The grinding technique allows the crumb rubbers to be produced in various sizes (about 7 to 8 different sizes). The biggest one has a diameter of about 5 mm

while the smallest one has a diameter of about 600 micron.

1.2 Concrete Microstructure Concrete consists mainly of three components:

cement, aggregates and water. During the mixing,

when water comes in contact with cement, series of chemical reactions called “hydration reactions” begin. The hydration reactions are exothermic and involve

series of temperature changes from beginning to end (until concrete get harden).

(a)

(b)

(c)

Figure 1 Manufacturing Crumb Rubber a) Sorting,

b) Grinding, c) Sieving

In harden concrete, the micro structure can be

divided into two parts: 1) solid and 2) void (or Porosity) part. The solid part consists of hydrated cement (Calcium Silicate Hydrate (CSH), Calcium

Hydroxide (CH), etc.), aggregates, unhydrated cement















(a)

(b)

(c)




















(a)

(b)

(c)






1. Introduction

1.1 Manufacturing Crumb Rubber

Abandoned tires has been a waste problem

around the world, millions ton of tires are being

discarded every year. In Thailand, total consumption

of rubber products was about 242 metric tons, this

number included about 90 metric tons of vehicle

tires [1]. One way to recycle them is to grind them

into small particles. Crumb rubber is widely

accepted and found it ways into several applications

such as asphalt, sealants, rubber sheets or mix with

cementitious materials like concrete.

In Thailand, the manufacturing of

commercialized crumb rubbers consists of three

steps (Figure 1). The first step is to cut and sort out

the grindable parts (parts without radial steels).

Next, the rubber pieces are fed into series of cutting

wheels several times until the desired size is

achieved. Finally, crumb rubbers are sorted out

according to the particle size. The grinding

technique allows the crumb rubbers to be produced

in various sizes (about 7 to 8 different sizes). The

biggest one has a diameter of about 5 mm while the

smallest one has a diameter of about 600 micron.

1.2 Concrete Microstructure

Concrete consists mainly of three components:


Figure 1 Manufacturing Crumb Rubber a) Sorting, b) Grinding, c) Sieving.

when water comes in contact with cement, series of

chemical reactions called “hydration reactions”

begin. The hydration reactions are exothermic and

involve series of temperature changes from

beginning to end (until concrete get harden).


divided into two parts: 1) solid and 2) void (or

Porosity) part. The solid part consists of hydrated

cement (Calcium Silicate Hydrate (CSH), Calcium

Hydroxide (CH), etc.), aggregates, unhydrated

cement and interface zones between cement and

aggregates. As for the porosity, there can be divided

into 3 different kinds: 1) capillary pores, 2)

gel pores, and 3) interface pores. The pores in

concrete come in various sizes. Capillary pores

caused primarily by entrapped water and are

considered the largest of all. Gel pores are consider

smallest and causes by the formation and

compaction of CSH [2], [3].

Usually, the pore structure plays a significant

role on the durability of concrete. This is because

the existing of these pores allows external

substances (moisture and gas) to migrate in and out

of concrete structures. Some substances can be

harmful and caused deterioration in concrete.

Therefore to increase concrete durability, engineers

have to deal directly with the pore structures.

Theoretically, the migrations of water and gas occur

(a) (c) (b)

299


mostly through the capillary pores which are large

pores and some of them might still interconnected

[4]. To stop the migrations, the volume of large

sized pores must be reduced. This can be achieved

by using small w/c ratio or using fillers (such as

silica fume, fly ash etc.).

1.3 Need for Better Insulation

Nowadays, the design and construction

purposes of a modern house should not focus on

residential and aesthetic purpose only, but also should

consider other issues like, energy conservation and

becoming an integral part of the environment. As we

know, the earth’s average temperature is rising slowly

every year due to the effect of global warming. Cares

for the environment are urgently needed by reducing

the use of fuel energy, encouraging the use of

recycled materials, reducing the emission of carbon

dioxide gas, etc [5]. The construction industry can

help by employing site management to minimize

wasted materials, using recycled aggregates, selecting

environmental friendly materials, etc.

In the case of an individual household,

architectural design based on environmental aspect

should be considered in order to achieve such goal.

From a concrete engineer’s point of view, material

selection also plays an important role. The use of

better insulating materials can directly reduce long-

term energy consumption.

1.4 Research Significance

In the last 20 years, material properties of

crumb rubber concrete have been investigated quite

exclusively [7]-[12]. Information on the mechanical

properties of crumb rubber concrete with particle

size varied from 1 mm and larger in terms of

compressive, tensile, flexural strengths, thermal and

sound, is quite well-known. However, there is no

information on the effect of crumb rubber with

particle size smaller than 1 mm on properties of

concrete. By using smaller particle size of crumb

rubber, the internal voids inside the concrete are

expected to be filled. By filling these voids, some

micro-mechanisms inside the concrete may be

different from normal concrete and concrete mixed

with large size crumb rubber. For example, the

overall absorption of concrete which is usually very

high most of the lightweight aggregate concrete may

decrease due to the decreasing of volume of

capillary pores. Thus, it is interesting to see whether

other properties are affected by the filler effect of

superfine crumb rubber.

Therefore, the objective of this study is to

investigate on the effect of superfine crumb rubber

powder on properties of concrete such as absorption,

porosity, thermal and sound properties (such as

thermal conductivity factor, thermal resistivity, heat

transfer, sound absorption at different frequencies

and noise reduction).

2. Experimental Program

2.1 Materials

Materials used in this study consisted of

Portland cement type I, 10 mm coarse aggregate,

river sand, crumb rubber (Figure 2), water and

superplasticizer Type F (13 cc /1 kg) of cement

weight. Crumb rubber with particle size pass

through sieve No. 25; the properties and gradation

of crumb rubbers are given in Table.1 and Figure3.

The mix proportion for the control specimen (no

crumb rubber) was set at 1.00:0.45:1.64:1.95

(Cement : Water : Fine Aggregate : Coarse Aggregate).

300


In the case of the superfine crumb rubber

concrete (SCRC), fine aggregate were replaced with

crumb rubber at 10% 20% and 30% by weight.

Gradation of sand and sand+crumb rubber is given

in Figure 4. Details on the casting and assigned

designations are given in Table 2.

2.2 Specimen Prepartion and Testing

Concrete was dry-mixed using pan mixer for

about 5 minutes, then added water and continued

mixing for another 5 minutes, after that it was poured

into molds. Three tests were carried out: 1) Density, Voids

and Absorption [13], 2) Steady-State Heat Flux

Measurement and Thermal Transmission Properties

[14]. (Figure 5), and 3) Acoustics Determination of

Sound Absorption Coefficient and Impedance in

Impedance Tube [15] (Figure 6). Number of

samples for each test is summarized in Table 3.

Figure 4 Gradation of Fine Aggregate+Crumb Rubber.

Figure 2 Crumb Rubber Powder.

powder on properties of concrete such as absorption, porosity, thermal and sound properties (such as thermal conductivity factor, thermal resistivity, heat transfer, sound absorption at different frequencies

and noise reduction).

2. Experimental Program 2.1 Materials

Materials used in this study consisted of Portland cement type I, 10 mm coarse aggregate,

river sand, crumb rubber (Figure 2), water and superplasticizer Type F (13 cc /1 kg) of cement weight. Crumb rubber with particle size pass through

sieve No. 25; the properties and gradation of crumb rubbers are given in Table.1 and Figure3. The mix proportion for the control specimen (no crumb

rubber) was set at 1.00:0.45:1.64:1.95 (Cement : Water : Fine Aggregate : Coarse Aggregate).

In the case of the superfine crumb rubber

concrete (SCRC), fine aggregate were replaced with crumb rubber at 10% 20% and 30% by weight. Gradation of sand and sand+crumb rubber is given

in Figure 4. Details on the casting and assigned designations are given in Table 2.

Table 1 Properties of Crumb Rubber and Aggregates

Categories Crumb Coarse Fine Rubber Agg. Agg.

Avg. Bulk SG 0.62 2.68 2.43 Avg. Bulk SG (SSD) 0.62 2.69 2.47 Avg. Apparent SG 0.62 2.70 2.55 Avg. Absorption (%) 1.05 0.25 2.04 Fineness Modulus 2.83 - 2.9

Figure 2 Crumb Rubber Powder

0102030405060708090

100

0.0010.010.11

Percent Finer by Weight

Diameter (in) Figure 3 Gradation of Crumb Rubber

0102030405060708090

100

0.0010.010.11

Percent Finer by Weight

Diameter (in.)

100% Fine

70% Fine + 30% CR (30SCRC)

80% Fine + 20% CR (20SCRC)

Figure 4 Gradation of Fine Aggregate+Crumb Rubber

Figure 3 Gradation of Crumb Rubber.

Table 1 Properties of Crumb Rubber and Aggregates

Categories Crumb Rubber

Coarse Agg.

Fine Agg.

Avg. Bulk SG Avg. Bulk SG (SSD) Avg. Apparent SG Avg. Absorption (%) Fineness Modulus

0.62 0.62 0.62 1.05 2.83

2.68 2.69 2.70 0.25

-

2.43 2.47 2.55 2.04 2.9

Table 2 Details and Assigned Designations

Designation

Weight per m3

Crumb Rubber

kg

Cement kg

Coarse Agg kg

Fine Agg kg

Water

kg

PC 0 478.7 933.5 783.8 215

10SCRC 78.4 478.7 933.5 705.5 215

20SCRC 156.8 478.7 933.5 627.1 215

30SCRC 235.2 478.7 933.5 548.7 215

301


Table 3 Casting Schedule

Type of Concrete

Number of specimen

Thermal Sound Density

PC 3 8 3

10SCRC 3 8 3

20SCRC 3 8 3

30SCRC 3 8 3

Total 12 32 12

Details of each test are described briefly below:

• Density and Voids [13] The specimens are

weighed under 4 different conditions: oven-dried,

saturated after immersion, saturated after boiling

and immersed under water. Then, the obtained

weights are used to calculate the density and

permeable voids based formulas given in the

standard.

• Steady-State Heat Flux Measurement and

Thermal Transmission Properties [14] The two

concrete specimens in form of square shape (300 x

300 x 25.4 mm) are setup between the heat source

(hot plate) and two cold surface assemblies. The test

begins by increasing the temperature of the hot plate

and at the same time measuring the temperature

change of both hot and cold surface assemblies.

Continue heating up until the temperature entered

the steady-state heat flux.

• Acoustics Determination of Sound

Absorption Coefficient and Impedance in

Impedance Tube [15] (21): Two different sizes of

specimens in form of dish: dia-290 x 500 mm and

dia-990 x 500 mm were used at two different

frequency ranges: high frequency (2000 and 4000 Hz)

and low frequency (125, 250, 500 and 1000 Hz).

Measurements were carried out according to the

standing wave method in which a loud speaker sets up

a sound field in a tube terminated by the sample.

When the standing waves were produced in the tube,

the ratio between the maximum and minimum sound

pressure were measured. The absorption coefficient

of the sample for zero degree incident sound wave

was then calculated from the measured data.

Figure 5 Steady-State Heat Flux [14].

2.2 Specimen Prepartion and Testing Concrete was dry-mixed using pan mixer for

about 5 minutes, then added water and continued mixing for another 5 minutes, after that it was

poured into molds. Three tests were carried out: 1) Density, Voids and Absorption [13], 2) Steady-State Heat Flux Measurement and Thermal Transmission

Properties [14]. (Figure 5), and 3) Acoustics Determination of Sound Absorption Coefficient and Impedance in Impedance Tube [15] (Figure 6).

Number of samples for each test is summarized in Table 3. Table 2 Details and Assigned Designations

Weight per m3

Designation Crumb Rubber Cement Coarse

Agg Fine Agg Water

kg kg kg kg kg

PC 0 478.7 933.5 783.8 215

10SCRC 78.4 478.7 933.5 705.5 215

20SCRC 156.8 478.7 933.5 627.1 215

30SCRC 235.2 478.7 933.5 548.7 215


Type of Number of specimen Concrete

Thermal

Sound

Density

PC 3 8 3 10SCRC 3 8 3 20SCRC 3 8 3 30SCRC 3 8 3

Total 12 32 12

Details of each test are described briefly below: Density and Voids [13] The specimens are


saturated after immersion, saturated after boiling and immersed under water. Then, the obtained weights are used to calculate the density and permeable

voids based formulas given in the standard.

Figure 5 Steady-State Heat Flux [14]

Figure 6 Acoustics Determination of Sound

Absorption Coefficient and Impedance in Impedance Tube [15]

Steady-State Heat Flux Measurement and


concrete specimens in form of square shape (300 x 300 x 25.4 mm) are setup between the heat source (hot plate) and two cold surface assemblies. The test

begins by increasing the temperature of the hot plate and at the same time measuring the temperature

2.2 Specimen Prepartion and Testing Concrete was dry-mixed using pan mixer for

about 5 minutes, then added water and continued mixing for another 5 minutes, after that it was

poured into molds. Three tests were carried out: 1) Density, Voids and Absorption [13], 2) Steady-State Heat Flux Measurement and Thermal Transmission

Properties [14]. (Figure 5), and 3) Acoustics Determination of Sound Absorption Coefficient and Impedance in Impedance Tube [15] (Figure 6).

Number of samples for each test is summarized in Table 3. Table 2 Details and Assigned Designations

Weight per m3

Designation Crumb Rubber Cement Coarse

Agg Fine Agg Water

kg kg kg kg kg

PC 0 478.7 933.5 783.8 215

10SCRC 78.4 478.7 933.5 705.5 215

20SCRC 156.8 478.7 933.5 627.1 215

30SCRC 235.2 478.7 933.5 548.7 215


Type of Number of specimen Concrete

Thermal

Sound

Density

PC 3 8 3 10SCRC 3 8 3 20SCRC 3 8 3 30SCRC 3 8 3

Total 12 32 12

Details of each test are described briefly below: Density and Voids [13] The specimens are


saturated after immersion, saturated after boiling and immersed under water. Then, the obtained weights are used to calculate the density and permeable

voids based formulas given in the standard.

Figure 5 Steady-State Heat Flux [14]


Absorption Coefficient and Impedance in Impedance Tube [15]

Steady-State Heat Flux Measurement and


concrete specimens in form of square shape (300 x 300 x 25.4 mm) are setup between the heat source (hot plate) and two cold surface assemblies. The test

begins by increasing the temperature of the hot plate and at the same time measuring the temperature


Absorption Coefficient and Impedance in

Impedance Tube [15].

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3. Results and Discussions

3.1 Density, Absorption and Voids

As shown in Table 4 and Figure 7, the crumb

rubber concrete exhibited lighter density than that of

plain concrete. The bulk density of normal concrete

was found to be about 2330 kg/m3, the average bulk

density of 10%, 20% and 30% crumb rubber concrete

were found at 2,090, 1,970 and 1,820 kg/m3,

respectively.

The decrease in bulk density of concrete was

mainly due to the replacement of a heavier material

(fine aggregate) by a lighter one (crumb rubber).

The fine aggregate (river sand) used in this study

has an average specific gravity (oven dry) of 2.42,

while the crumb rubber has an average of about

0.61. By calculation, at 10%, 20% and 30%

replacement ratio, the overall density of concrete

was expected to decrease (due to the effect of crumb

rubber alone) by 7.5%, 14% and 19.5%, respectively.

The actual results are slightly higher than the

calculation and this, perhaps, due to the effect of

moisture in fine aggregate that did not taken into

account in the calculation.

In the case of the absorption and permeable

void (Table 4, Figure 8), unlike other lightweight

aggregated concrete, the effect of crumb rubber

adding into concrete appeared to lower both

absorption and permeable void content. For

conventional lightweight concrete, these two values

would be quite high because of the high porosity in

aggregates or large amount of air bubble in cement

paste. But when using crumb rubber powder, even

though the overall density of concrete decreased

gradually with the rubber content, the permeable

void was found to decrease instead of increase.

The decrease in permeable void and absorption

was because of 2 reasons: 1) the porosity of crumb

rubber particle and 2) the filling effect. In the case of

porosity, refer to Table 1, it could be seen that the

specific gravity of superfine crumb rubber under both

SSD and oven dry conditions were quite similar (0.61

and 0.62, respectively). The similarity implied that

crumb rubber was, in fact, not a porous material.

Therefore, by adding them into concrete, there was

no additional pore adding into the concrete pore

system. As for the filling effect, the small particle of

superfine crumb rubber (SCRC) played a significant

role in this part. With small particle size as 500-600

micron, the crumb rubbers were able to fill up some

of the capillary pores which led to the decrease in

absorption from 4.26% to 2.98% as show in Figure 8.

Figure 7 Bulk Density of Concrete vs. Crumb

Rubber Concrete.

Table 4 Bulk Density, Void and Absorption

Type Bulk Density (kg/m3)

Void (%)

Absorption (%)

PC 2330 9.35 4.26

10SCRC 2090 6.79 3.51

20SCRC 1970 5.90 3.39

30SCRC 1820 5.81 2.98

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3.2 Thermal Conductivity

By definition, the quantity of heat transmitted

through a unit thickness in a direction normal to a

surface of unit area, due to a unit temperature

gradient under steady state conditions is defined as

the thermal conductivity value (k). There are several

parameters affecting the value of k in materials,

such as density, moisture content, temperature etc.

In this case, let consider only the density.

Theoretically, the value of thermal conductivity is

directly proportional to the density; this means

materials with low density will usually exhibit low

value of k.

Based on the test results as shown in Figure 9

the k value of plain concrete was found at 0.531 W/m.K,

while those of SCRC were at 0.290, 0.275, and

0.267 W/m.K for 10SCRC, 20SCRC and 30SCRC,

respectively. Comparing in percentage, they are

lower by about 44% to 49%. The lower values of k

indicated that SCRC is essentially a better insulator

than plain concrete and is partly due to the lower

density of SCRC than that of plain concrete.

According to Thailand Industrial Standard

(TIS), the allowable values of k are specified within

the range of 0.303 to 0.476 W/m.K for conventional

lightweight concrete. The k-values of SCRC obtained

from this study were found to be less than or within

the allowable range of those specified by TIS.

3.3 Heat Transfer Rate and Heat Resistivity

The rate of heat transfer per unit time (hour)

and heat resistivity can be calculated using the

following equations:

(1)

(2)

Where q is heat transferred per unit time (W/ hour ),

r is heat resistivity (m2/kW), A is heat transfer area

(m2), k is thermal conductivity (W/m.K), dT is

Temperature difference across the material (K), t is

material thickness (m).

Using the value of k from the test and

assuming that the temperature difference between

night and day is 12oC, the area is 1 x 1 m2 and the

thickness is 0.10 m, the heat transfer and resistivity

of both plain and CR concrete can be calculated as

shown in Table 5.

Figure 8 Permeable Voids and Absorption.

Figure 9 Thermal Conductivity (k).

304


Table 5 Rate of Heat Transfer and Heat Resistivity

Type Heat Transfer W/h

Heat Resistivity m2/kW

PC 1,514 0.19

10SCRC 827 0.34

20SCRC 784 0.36

30SCRC 761 0.37

3.4 Sound Absorption

The ability of material to absorb sound at any

particular frequency is defined in form of the sound

absorption coefficient (α). In general, for a healthy

young person, the hearing range is 15 to 18,000

hertz [24]. According to the standard test, six

different ranges of sound frequencies were used to

measure the sound absorption of both plain and

SCRC: 125, 250, 500, 1000, 2000 and 4000 Hz.

The variation of α for each material over the

wide range of frequencies can be high or low

depending on material type. On the low side, for

example, a marble tile exhibits quite consistency

values of 0.01, 0.01, 0.01, 0.01, 0.02, and 0.02 over

the six frequency ranges. On the high side such as a

plaster board (for ceiling), it has rise and fall values

from 0.15, 0.11, 0.04, 0.04, 0.07, and 0.08 [25].

Results of both plain and SCR concrete are

shown in Figure 10. It could be seen that at the low

frequency ranges of 125 and 250 Hz, both plain and

SCR concrete exhibited similar values of α. However,

at frequencies higher than 500 Hz, those of SCRC

started to separate and became higher than that of

plain concrete (Figure 11). High α indicated that

SCRC can absorb sound better at high frequency

ranges than plain concrete.

In addition, the sound absorption of material

can be illustrated using another value so called the

noise reduction coefficient (NRC). The NCR is an

average value of α at four frequencies in the middle

range, can be calculated using the following

equation:

NCR = (α250 + α500 + α1000 + α2000)/4 (3)

Results of NCR against the density are given

in Figure 11. Clearly, the noise reduction depended

mainly on the density of material. As the density

decreased, the noise reduction increased. For SCRC

which density less than plain concrete by about

20%, the noise reduction increased by about 46%.

Figure 10 Sound Absorption Coefficient. Figure 11 Noise Reduction Coefficient.

305


4. Conclusions

1. Concrete mixed with crumb rubber powder

has shown improvements on both porosity and

absorption by reducing both values up to about 38%

and 30%, respectively (at 30% replacement rate).

With small particle size, the crumb rubber is able to

fill up some capillary pores and voids in concrete.

2. With smaller specific gravity than conventional

fine aggregate, the crumb rubber can reduce the density of

concrete up to about 20% at the 30% replacement rate.

3. SCRC also provides better insulating properties

in both thermal and sound as seen by the decreasing

thermal conductivity value and increasing sound

absorption coefficient as compare to those of plain

concrete.

5. Acknowledgement

The authors would like to thank the Thailand

Research Fund-Master Research Grants (TRF-MAG)

for financially support this study and also Union

Pattanakit Co., Ltd., for providing crumb rubber.

References

[1] Rubber Research Institute, Statistic on the Use

of Vehicle Tires in Thailand, Ministry of

Agriculture, Thailand.

[2] S. Mindess, JF. Young and D. Darwin,

Concrete, 2nd Edition, Prentice Hall, 2003.

[3] A.M. Neville, Properties of Concrete, 4th

Edition,” Longman, 1996.

[4] JF. Young, S. Mindess, RJ. Gray and A. Bentur,

The Science and Technology of Civil

Engineering Materials, Prentice Hall, 1998.

[5] Montreal Protocol, United Nations

Environment Program, United Nation, 1997.

[6] N. Eldin and A. Senouci, “Measurement and

Prediction of the Strength of Rubberized

Concrete,” Cement and Concrete Composite,

no. 19, pp. 287-298, 1994.

[7] N. Eldin and A. Senouci, “Rubber-Tire Particles

as Concrete Aggregate,” ASCE: Journal of Materials

in Civil Engineering, vol.5, no.4, pp. 478-496, 1993.

[8] N. Fattuhi and L. Clark, “Cement Based

Materials Containing Shredded Scrap Truck

Tyre Rubber,” Construction and Building

Materials, vol. 10, no. 4, pp. 229-236, 1996.

[9] H. Huynh, D. Raghavan and C. Ferraris,

“Rubber Particles from Recycled Tires in

Cementitious Composite Materials,” NISTIR

5850 R; May 1996.

[10] Z.K. Khatib and F.M. Bayomy, “Rubber

Portland Cement Concrete,” Journal of

Materials in Civil Engineering, vol.11, no. 3,

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[11] H. Rostami, J. Lepore, T. Silverstraim and I.

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[13] ASTM DESIGNATION: C 642-97, Test Method

for Density, Absorption, and Voids in Hardened

Concrete.

[14] ASTM DESIGNATION: C 177-97, Test Method

for Steady-State Heat Flux Measurements and

Thermal Transmission Properties by Means of

the Guarded-Hot-Plate Apparatus.

[15] ISO DESIGNATION: 10534-1, Test Method

for Acoustics-Determination of Sound Absorption

Coefficient and Impedance in Impedance Tubes.

Part 1: Method Using Standing Wave Ratio.

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Lightweight Concrete Mixed with Superfine Crumb