Strength Characteristics and Temperature Distribution of Concrete Containing Crumb Rubber as Partial Replacement of
Fine Aggregate
Broneca Sibin1*, Eriant Jolly1, Verrill Valeryan Victor Wong1, Ahmad Nurfaidhi Rizalman1**
1 Faculty of Engineering, Universiti Malaysia Sabah, Jalan UMS, 88400, Kota Kinabalu, Sabah, Malaysia
*Corresponding Author: *[email protected], **[email protected]
Accepted: 15 February 2021 | Published: 1 March 2021
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Abstract: This paper presents an experimental study on the strength characteristics and temperature distribution of concrete containing crumb rubber as partial replacement of fine aggregate. This study examines the effect of different percentages (3%, 5%, 10% and 15%) of crumb rubber on concrete with strength of 25 N/mm2 and 30 N/mm2. The results show that crumb rubber reduces slump, compressive strength, and flexural strength of concrete.
Moreover, concrete containing crumb rubber has higher temperatures than plain concrete when exposed to fire.
Keywords: crumb rubber, strength, temperature, fine aggregate, sustainable concrete
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1. Introduction
Tyre rubber is a curved-shape, durable and non-biodegradable material. Due to these properties, managing waste tyre rubber by landfills and burning are considered as non- sustainable for several reasons: (1) they take up a lot of space in landfill, (2) they release toxic substances when burned, and (3) they provide breeding grounds for mosquitoes. In other words, they pose negative impacts to environment and human health. Therefore, the management is shifted to reuse waste tyre rubber as viable route to cut down the amount of waste produced.
In building construction, numerous attempts have been made to investigate the reuse potential of waste tyre rubber as aggregate replacement in concrete (Thomas & Gupta, 2016; Shu &
Huang, 2013). A few studies consistently discovered that the use of rubber improved the ductility, toughness, impact resistance, fracture, and damping of the concrete (Gerges et al., 2018; Moustafa & Elgawady, 2017; Abdullah et al., 2012). However, concrete containing tyre rubber suffered a reduction in compressive and flexural strength, and greater strength loss was obtained when coarse aggregates are replaced rather than fine aggregates (Yu & Zhu, 2016).
Thus, the tyre rubber was grinded into smaller sizes ranging from 4.75mm to 75μm, called as crumb rubber, to partially replace fine aggregates in concrete. Although it still reduced the strength, it met the minimum strength requirements of light weight concrete (Sofi, 2018;
Mohammed et al., 2017).
Despite many studies on the mechanical and dynamic properties of concrete containing tyre rubber, the knowledge on the fire performance of concrete containing tyre rubber is not widely explored. Therefore, this study aims to investigate the strength characteristics and temperature distribution of concrete containing crumb rubber. The concrete is produced by using crumb
rubber at different percentages as replacement of fine aggregate. Then, the slump height, compressive strength, flexural strength, and temperature distribution of concrete containing crumb rubber are evaluated against normal concrete.
2. Materials and Methods
Materials
The cement used was Ordinary Portland Cement (ASTM Type 1). The crumb rubber used in this research was obtained from Hoyu Tyre Sales Sdn. Bhd as shown in Figure 1. The physical properties of crumb rubber, fine aggregates, and coarse aggregates are tabulated in Table 1.
Figure 1: Crumb Rubber
Table 1: Physical properties of coarse aggregates, fine aggregates, and crumb rubber.
Material Type Size Moisture Content (%) Water Absorption (%)
Crumb Rubber Tyre Rubber < 4.75 mm 1.43 2.00
Fine Aggregates River Sand < 4.75 mm 1.24 1.29
Coarse Aggregates Sandstone 10 – 20 mm 0.76 1.67
Mix Proportions
The concrete mixes in this study were designed according to the Standard Specifications for Building Work (Jabatan Kerja Raya Malaysia, 2005). To investigate the strength characteristics, two (2) groups of concrete mixes were used with target strength of 25 N/mm2 (Group 25P) and 30 N/mm2 (Group 30P). Group 25P was designed with a constant water to cement (W/C) ratio of 0.50 and cement content of 9.54 kg/m3. In group 30P, the W/C ratio and cement content were kept constant at 0.45 and 10.65 kg/m3, correspondingly. The percentage replacements of fine aggregate with crumb rubber were 3%, 5%, 10% and 15% by weight. In total, there were (10) specimens tested on slump height, compressive strength, and flexural strength. The reading for each specimen was taken as an average of three (3).
For the investigation on the temperature distribution, only concrete in Group 25P was used.
There were (2) specimens in this study: plain concrete and concrete containing 10% of crumb rubber. Table 1 shows the proportions of concrete mixes of the study.
Test Methods
The slump height of the specimen was measured in accordance with procedures specified in
x 100 x 100 mm and 100 x 100 x 500 mm mould. After 24 hours, they were demoulded and cured in water for 28 days. Then, they were tested for compressive strength and flexural strength in accordance to BS EN 12390:3 and BS EN 12390:5, respectively (British Standard Institution, 2009).
For temperature distribution measurement, the fresh concrete was poured in a 420 x 130 x 200 mm mould. They were demoulded after 24 hours and cured in water for 28 days. Then, the concrete block was exposed to fire for 30 minutes. The temperature was measured at three (3) points (as shown in Figure 1) by using thermometer.
Table 2: Proportions of Concrete Mixes.
Group Specimen W/C ratio
Water Cement Coarse Aggregate
Crumb Rubber
Fine Aggregate
kg/m3 kg/m3 kg/m3 % kg/m3 kg/m3
25P
25P-00 0.50 4.89 9.54 32.60 0 0 13.97
25P-03 0.50 4.89 9.54 32.60 3 0.41 1356
25P-05 0.50 4.89 9.54 32.60 5 0.70 13.27
25P-10 0.50 4.89 9.54 32.60 10 1.40 12.57
25P-15 0.50 4.89 9.54 32.60 15 2.11 11.89
30P
30P-00 0.45 4.89 10.65 31.70 0 0 13.58
30P-03 0.45 4.89 10.65 31.70 3 0.40 13.17
30P-05 0.45 4.89 10.65 31.70 5 0.68 12.89
30P-10 0.45 4.89 10.65 31.70 10 1.36 12.22
30P-15 0.45 4.89 10.65 31.70 15 2.03 11.53
(a) (b)
Figure 2: Test Setup for Measuring Temperature Distribution of Concrete Block.
3. Results and Discussions
Table 3 shows the numerical results of the experimental study of slump, compressive strength, and flexural strength for concrete 25P and 30P. The discussions of the results are presented in the subsequent topics.
Table 3: Summary of Results.
Specimen
Slump Height Compressive Strength Flexural Strength Value
(mm)
Percentage Reduction (%)
Value (mm)
Percentage Reduction (%)
Value (mm)
Percentage Reduction (%)
25P-00 40 0 25.03 0.00 5.74 0.00
25P-03 37 7.50 20.18 19.37 5.70 0.70
25P-05 28 30.00 16.85 32.66 5.61 2.26
25P-10 27 32.50 11.73 53.13 5.38 6.27
25P-15 27 32.50 10.78 56.93 5.13 10.63
30P-00 41 0.00 28.23 0.00 6.21 0.00
30P-03 38 7.32 25.36 10.17 6.12 1.45
30P-05 32 21.95 24.06 14.80 5.81 6.44
30P-10 29 29.27 21.01 25.58 5.46 12.08
30P-15 27 34.15 18.12 35.81 5.16 16.91
Slump Height
The comparison of slump height results between concrete 25P and 30P is shown graphically in Figure 3. The results are consistent with a constantly decreasing trend as the percentage replacement of crumb rubber increases. Similar findings were also reported by several researchers (Rashad, 2016; Najim & Hall, 2013). Meanwhile, a huge drop in slump height was observed in 5% of crumb rubber for both concrete 25P and 30P.
The reduction in the slump height can be attributed to the rough surface of the crumb rubber particles as illustrated in Figure 1. The increase amount of crumb rubber in concrete increases the friction between rubber and the other particles which lead to less flow of the fresh concrete (Jirjees et al., 2019; Holmes et al., 2014).
Figure 3: Slump Height Comparison between Concrete 25P and 30P.
Figure 4: Image Enhancement of Crumb Rubber under Scanning Electron Microscope.
Compressive Strength
Figure 4 shows the comparison of compressive strength between concrete 25P and 30P. A decreasing trend in compressive strength was observed with the increase percentage replacement of crumb rubber for both concrete. Several researchers have also reported similar results (Jirjess et. al., 2019; Liu et al., 2017; Yusof et al., 2014).
The reduction in the compressive strength can be contributed to the bond between the crumb rubber particles and cement paste. As illustrated in Figure 6(a), well-bonded particles are observed in plain concrete. However, the rubber particles are poorly bonded with the cement paste which resulted to a gap between them, as shown in Figure 6(b). This caused the compressive strength of concrete containing crumb rubber to be reduced. Similar observations were also made by previous researchers (Bisht & Ramana, 2017; Mohammed 2017; Rashad, 2016).
Figure 5: Compressive Strength Comparison between Concrete 25P and 30P.
(a) (b)
Figure 6: Image enhancement of (a) plain concrete and (b) concrete containing crumb rubber under scanning electron microscope.
Flexural Strength
Figure 5 shows the flexural strength results for both concrete 25P and 30P. As the figure illustrates, the flexural strength decreases as the replacement percentage of crumb rubber increases. Similar findings were also obtained by previous studies (Bisht & Ramana, 2017; Yu
& Zhu, 2016). Moreover, unlike compressive strength, the differences in flexural strength between concrete 25P and 30P also become smaller as more crumb rubber are added to the concrete. At 15% replacement of crumb rubber, the difference in the flexural strength of concrete 25P and 30P is only 0.03 MPa; both are 5.13 MP and 5.16 MPa, respectively.
Figure 7: Flexural Strength Comparison between Concrete 25P and 30P.
Temperature Distribution
The temperature distribution between plain concrete and concrete containing 10% of crumb rubber as fine aggregate replacement was compared by measuring temperatures at three (3) points as illustrated in Figure 8. The results are tabulated in Table 4. From the table, it shows that concrete containing crumb rubber has higher temperature than plain concrete. These results suggest that concrete containing crumb rubber is not suitable to be used in areas of high fire risk.
However, it should be noted that the fire used in this test originated from lighter and ignited by using charcoal. It was also conducted in open environment where the specimens were exposed to external wind, thus may affect the reliability of the results. Therefore, it is suggested that the fire test is to be conducted in a closed environment where a constant and repeatable fire exposure is provided. Plus, the effect of varying amount of crumb rubber as fine aggregate replacement on the temperature of concrete should be included in future study.
Figure 8: Point of Temperature Measurement of the Concrete Block.
Table 4: Temperature Measurement of Plain Concrete and Concrete Containing Crumb Rubber.
Point
Plain concrete Concrete containing 10% of crumb rubber as fine aggregate replacement
Initial temperature (oC)
Final Temperature (oC)
Initial temperature (oC)
Final Temperature (oC)
A 37 123 37 141
B 33 112 33 135
C 31 82 31 112
4. Conclusion
In this study, the strength characteristics and temperature distribution of concrete containing crumb rubber was carried out. The percentages of crumb rubber as replacement of fine aggregates were 3%, 5%, 10%, and 15%. It was tested on two (2) grades of concrete, 25 N/mm2 and 30 N/mm2. Based on the study, the following conclusions are drawn:
a) Slump height, compressive strength and flexural strength of concrete reduced as the percentage of crumb rubber as fine aggregate replacement increased. The reduction in the properties of concrete containing crumb rubber was due to the rough texture of crumb rubber and poor bond of the rubber particles with the cement paste.
b) Higher temperatures were observed in concrete containing crumb rubber than plain concrete when exposed to fire. However, it is recommended that fire test is to be conducted in closed environment to ensure constant and repeatable fire exposure on the concrete. In addition, the effect of varying amount of crumb rubber on the temperature of concrete in fire is to be investigated in the future.
Acknowledgement
The authors would like to thank University Malaysia Sabah (UMS) for granting this project under code UMSGreat GUGO346-1/2019.
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