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 CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 55, 2016 

A publication of 

 
The Italian Association 

of Chemical Engineering 
Online at www.aidic.it/cet 

Guest Editors: Tichun Wang, Hongyang Zhang, Lei Tian
Copyright © 2016, AIDIC Servizi S.r.l., 
ISBN 978-88-95608-46-4; ISSN 2283-9216 

Research on Mechanical Properties of Steel Fiber Reinforced 
Rubber Concrete 

Yonggang Mi*, Yunhe Liu 
School of Civil Engineering and Architecture, Xi'an University of Technology, Xi'an 710048, China. 
miyonggang2006@163.com 

The purpose of this paper is to research on the mechanical properties of steel fiber reinforced rubber concrete 
in this paper. Cracks, deformation and other issues often exist in the process of using concrete, a commonly 
used building material. Adding a certain amount of powder or rubber particles in concrete can be a good 
solution to these problems. This work studied construction technology of green rubber concrete. It is found 
that only by emphasizing the selection of tire and rubber particles as well as fabrication and application of 
rubber concrete can the quality of construction engineering be improved to the highest extent, based on the 
concept and characteristics of rubber concrete and combining them with the status of their applications in 
building construction. 

1. Introduction 
Crumb Rubber Concrete (CRC) is one type of “young” building materials, with less than thirty years of history. 
CRC exhibits many different mechanical behaviors from those of conventional concrete. Current studies 
reveal that (1) CRC improves its anti-cracking behavior; (2) CRC increases in the resistance to water and 
chloride penetration; and (3) CRC exhibits large deformability and energy-absorbing capability. These macro 
properties of CRC have a close relationship with its microstructure and would affect the structural properties. 
In this regards, it is important to “read” CRC in the view of microscopic scale and explore its influence on 
structural properties.  
With the development of building technology, demands for high-performance materials are growing. In 
traditional architecture, mud and stones and other materials are mainly used, resulting in poor quality of 
construction and impossibility of constructing high rise buildings. Yet with the development of modern natural 
science and technology, the discipline of material science emerges, playing a significant role in the 
construction sector (Siddique et al., 2004). For example, the use of steel, concrete and other materials can 
greatly improve the quality of construction work. Subject to historical factors, China started late in science and 
technology and there are still gaps between China and some western countries in the study of concrete and 
other materials. Especially with the emergence of skyscrapers in recent years, the requirements for the 
performance of concrete are higher. In this context, different materials are added to the concrete according to 
practical needs, creating some new features in concrete. For example, adding powder or rubber particles can 
produce high flexibility in the concrete (Hernández-Olivares et al., 2002). Although concrete is one of the most 
commonly used building materials, it does not always meet the requirements due to the high brittleness. It has 
been observed from some previous research that the properties of concrete will be improved when the used 
automobile-tire chips are added into concrete. As a new material rubber concrete can not only improve the 
performance of concrete but also solves the problem of dealing with waste tires. This is a kind of resource 
saving and environment-friendly material, which has a broad application prospect in civil engineering. As a 
kind of hyper-elastic material, rubber primarily improves the internal structure of concrete through physical 
interaction without changing the chemical properties of each component in the concrete. Adding the rubber 
particles greatly improve the properties of shock absorption, impact resistance, spilling resistance, heat and 
sound insulation and etc. The figure 1 shows the steel fiber reinforced rubber concrete roof. 
 

                               
 
 

 

 
   

                                                  
DOI: 10.3303/CET1655067

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Please cite this article as: Mi Y.G., Liu Y.H., 2016, Research on mechanical properties of steel fiber reinforced rubber concrete, Chemical 
Engineering Transactions, 55, 397-402  DOI:10.3303/CET1655067   

397



 

 

 

Figure 1: The steel fiber reinforced rubber concrete roof 

2. Analysis of rubber concrete 
Concrete plays an important role in construction. The use of concrete has greatly improved the quality of 
construction, so it is highly valued. But with the development of the construction sector itself and the 
emergence of complex engineering works, concrete of superior performance must be used in order to 
complete these projects and demands for properties of concrete are even various (Toutanji et al., 1996). In this 
context, certain materials are added to concrete to promote better performance of the concrete. Naturally, tire 
and rubber particles are added to concrete to make rubber concrete, because rubber has good elasticity while 
concrete often causes cracks, deformation and other issues and even accidents in the process of using and 
after completion. Adding powder or rubber particles into concrete can ensure certain flexibility of the concrete, 
thereby avoiding cracks. In traditional concrete construction, water is easy to penetrate the interior, corrosion 
steel and other materials, while rubber concrete can increase tightness. Thus, the use of rubber concrete can 
improve the performance of concrete from different aspects.  
Rubber concrete has distinctive features compared with ordinary concrete. Above all, rubber concrete has 
good flexibility, effectively preventing the building deformation, increasing the building. Airtight is keeping 
water from penetrating into the concrete and protecting the steel and so on. Out of practical applications, 
people can add other materials to concrete to achieve the same goals but at a higher price than rubber. 
Consequently, the use of rubber is common now, producing a lot of waste and large amounts of polluting 
gases when it is being burned due to its corrosion resistance. Especially with the shorter lifespan of rubber 
products, such as three years for car tires, and the popularity of automotive applications, a large number of 
rubber garbage is produced annually. Therefore disposal of these rubber wastes has become an important 
issue. This shows that adding powder and rubber particles to concrete can not only control the costs well, but 
can also solve environmental problems to a certain extent. Due to rubber concrete's lower requirements to 
rubber; it is essential to make waste rubber products into the form of powder or granules after simple 
treatment. It is precisely these characteristics of rubber concrete that make it widely used in modern building 
construction (Hernández-Olivares et al., 2004).  
With the limitation of technology in China, the study of new materials such as rubber concrete started late. 
While in the late eighties, the United States had already began to conduct researches on rubber concrete, 
adding a powder and granular form of rubber to concrete to improve the performance of concrete. Still, actual 
survey found that adding different components of powder and granules differentiated the performance of the 
concrete. However, due to the low level of technology at the time, the performance of rubber concrete could 
not be controlled well. With the development of material science and construction engineering, rubber 
concrete has been highly valued and widely used in the actual construction due to its superior performance 
(Khaloo et al., 2008). Through practical researches, people have gotten a deeper understanding of the impact 
of different amounts of tire and rubber particles to the concrete's properties. In the actual construction, people 
were targeted to select powder or rubber particles as well as the specific components according to the actual 
needs. Due to the low level of technology, rubber concrete in China (Batayneh et al., 2008) has a relatively 
short-time development. The real estate market in China has been hot in recent years, so out of the actual 
need for building construction and China's actual situation, some foreign advanced technology has been 
learned and the country's rubber concrete technology has been improved. Also, to maximize the performance 
of rubber concrete, some simple experiments will be carried out in the field in the actual construction process 
(Cheng et al., 2014).  

3. The rubber concrete model and algorithm 
Rubber concrete has been widely applied after years of development and improvement. People continue to 
improve rubber concrete in the process of use, making rubber concrete relatively perfect (Shu et al., 2014). 

398



 

 

According to the actual needs, people are targeted to match proportions of rubber concrete. As basic 
materials in construction, the rubber concrete's performance can directly affect the quality of the project, so 
factors that affect the use of it must be paid attention to. The figure 2 shows the basic figure for mechanical 
properties (Thomas et al., 2014). 
 

 

Figure 2: The basic figure for mechanical properties 

There are lots of such factors in the actual building construction. The first one is the operator's professional 
quality. The operator works to mix and stir rubber concrete, only sufficient technical skills ensuring the 
properties of rubber concrete. The second factor is rubber concrete material itself. In making rubber concrete, 
people get sand and mud around the construction site to facilitate the construction project. Due to different 
geological conditions in different regions, sand stone and mud vary in performance. As a result, the 
performance of rubber concrete will be greatly impacted by materials in poor geological conditions. Besides, 
environmental factors should be considered because rubber emits toxic gases. Correspondingly, rubber 
concrete should be handled properly in order not to influence the construction project and the personnel's 
health.  
Green rubber concrete has been very widely used in building construction because of its characteristics. And it 
is applied in China's construction sector but the limited technical level causes many problems in the actual 
applications. To start with, it is the lower quality of the construction workers. They cannot get a good grasp of 
the ratio of rubber concrete as well as the amount of powder and rubber particles to be added according to the 
actual needs. Next it comes the law level of environmental protection. Most of the rubber used in rubber 
concrete is junk, the majority being automobile tires. These rubber products have little to do with 
environmental protection and emit harmful gases in the production process. Therefore, these rubber materials 
will be exposed in indoor environment and greatly impact human health if not properly disposed. Actual survey 
finds that currently less rubber concrete has been used in building construction in China despite of people's 
realization of its importance. The main cause of this phenomenon is fewer manufacturers of powder and 
rubber granules meanwhile with a relatively backward production process. They are unable to meet the needs 
of the actual use of rubber concrete. Thus, it is necessary to intensify research on rubber concrete to improve 
its application in China.  
Assume that the input of question is a pattern set { } ⊂  composed of second-type object. If any object  
belongs to the first type, mark it as 1, if it belongs to the second type, mark it as -1. Take n samples from 
collection as training set, as is shown in (1) (hunag et al., 2016): 

( , ) 1, 2, 3,..., ni ix y i =  

1
1i

y
=

= 
= −   (1) 

The final purpose of Support Vector Machine is: based on selected training set, a discriminant function is 
formed to distinguish the second type model correctly.  
In mathematics, hyperplane is linear subspace whose codimension equals 1 in eulidean n-spaces. This is the 
extension of straight line in plane and plane in space. Assume that F is domain, hyperplane in Fn of eulidean 
n-spaces is shown in (2)  

1 1 2 2 ... 0n na x a x a x b+ + + + =    (2) 
The defined subset, among which  is the constant all of which are not zero, as is shown in (3) 

399



 

 

, 0iw x b+ =    (3) 
So, if hyperplane  exist to make  

, 1iw x b+ ≥  1iy =   (4) 

, 1iw x b+ ≤ − 1iy = −   (5) 
Therefore, domain F is linearly separable. Generally, F is called training set, and there exists such hyperplane 
of the training set which is also linearly separable. 

2exp , 1, 2,...,2
j

j
j

X C
h j m

b

 −
 = − =
 
    (6) 

The output of the network is given as: 

( ) 1 1 2 2 ...m m my k wh w h w h w h= = + + +   (7) 
Assuming the ideal output is y (k), the performance index function is: 

( ) ( ) ( )( )21
2 m

E k y k y k= −
   (8) 

The equation of basic function is as equation (9) as follows: 

( ) 0j ijkl k l kij k iC u e uϕ ρ∂ ∂ + ∂ − =    (9) 
Under the linear relationship, basic equation is shown in equation (2): 

( ) 0j ijkl k l kij ke u η ϕ∂ ∂ − ∂ =    (10) 

The linear differential equation can be expressed into the following simplified forms: 

( , ) ( , ) 0L f xω ω∇ = , 
2( , ) ( )L Tω ω ρ∇ = ∇ + J    (11) 

In which, 

( ) ( )
( )

( ) ( )
ik i
T
k

T t
T

t τ
∇ ∇

∇ =
∇ − ∇

, 

0
=

0 0
ikδ

J
 ,

( , )
( , )

( , )
ku xf x

x
ω

ω
ϕ ω

=
   (12) 

4. The experiment and result analysis 
For rubber concrete, the selection of tire and rubber particles is important. It not only directly affects the 
performance of rubber concrete, but also impacts costs. There are currently lots of manufacturers producing 
powder and rubber particles on the market, offering a variety of powder products to meet the needs of different 
areas. In the actual selection, optimal and targeted powder or rubber granules should be selected according to 
the actual needs as well as the using effect of powder. Actual survey finds that marry of currently available 
powder and rubber particles are produced by foreign companies. While some production companies in China 
represent a large gap with foreign companies in the powder properties. For cost considerations, some 
construction units will choose products from China's companies in actual building construction due to the 
relatively low price of tire and rubber granules. It often results in quality problems after completion. This shows 
the importance of the selection of tire and rubber particles.  
By the actual construction process, certain experiments will be conducted after the selection to ensure the 
performance of the powder and rubber particles. And if conditions permit it, they can be taken to the laboratory 
to detect with professional testing equipment to make a comprehensive understanding of it.  
The proportion and mixing are very important for ordinary concrete, the same being true of rubber concrete. 
Adding material to concrete increases the difficulty of the proportion and mixing. Therefore the operator must 
understand the specific properties of concrete in different proportions in order to take good control of its 
performance. It is the only way to grasp the added amount of powder or rubber particles to make rubber 

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concrete meet the needs of the actual construction. In the actual making process, the operator should pay 
attention to the ratio of ordinary concrete apart from powder and rubber particles. Because adding powder will 
affect the performance of normal concrete, mechanical experiments should be initiated in the field to ensure 
the performance of rubber concrete and meet the needs of actual application. The rubber concrete can only 
be used after the test of practice. In China's production of rubber concrete, the staff merely adds some powder 
or rubber particles to ordinary concrete based on their work experience due to their low qualities. Although in 
this approach, properties of rubber concrete can be improved, the targeted ratio cannot be accomplished 
according to the actual situation of the construction project. For example, some of the concrete possesses a 
certain degree of flexibility but still cannot meet the needs of practical use since some parts require higher 
elasticity. Figure 3 shows the tensile property and flexure property. 
 

 

Figure 3: The tensile property and flexure property 

According to the previous analysis, different adding amounts of powder and rubber particles will differentiate 
the performance of rubber concrete. Taking the complexity of the current project into account, different parts of 
the construction require various materials in the actual building construction. So the added amount of powder 
and rubber particles should be controlled to meet the needs of different parts of the project. Thus the use of 
rubber concrete should be targeted. The operator should analyze the project program and get specific 
understanding of different parts' needing components of concrete, to produce the corresponding amounts of 
rubber concrete. In practical construction, different parts of the construction using rubber concrete with 
corresponding properties can improve the quality of construction works in large parts. This plays an important 
role in the construction of the project. Given the complexity of building construction, the rubber concrete 
usually requires site fabrication. After fabrication, simple experiments should be conducted in the field to verify 
some important properties of rubber concrete in order to the performance of concrete. Only the authenticated 
materials can be used in the actual construction, so that the quality of construction projects can be well 
controlled. Figure 4 shows the XRD result. 
 

 

Figure 4: The experiment result 

XRD results show that although the chemical constituents of cement is complicated, no new phase is found in 
the hydration products of the cement paste incorporating crumb rubber; The peak intensity of calcium 
hydroxide (CH) from the hydration products of the cement paste incorporating crumb rubber is reduced 
significantly compared to that from the control blends. This suggested that cement-based materials 
incorporating crumb rubber would have a larger growth in strength in late time, and this suggestion is 
preliminarily supported with a set of experimental data by other searchers. Through the pore structure and 
fractal characteristic of CRC which is analyzed quantitatively using MIP, the results show that the Mode Pore 

401



 

 

Diameter, the Mean Pore Diameter, the Median Pore Diameter and the porosity of CRC are increased 
compared to those of conventional concrete, and the pore distribution scope of CRC becomes wide. The 
fractal dimension D of the pores in CRC decreases with the increase of the crumb rubber content, which 
indicates that the pore distribution tends to becomes regular when rubber is added.  A finite element model for 
a rectangular plane containing an elliptic hole in the center is established based on stress concentration theory. 
This model illustrates the mechanism of rubber’s delaying the multiplication of the crack in CRC and explains 
why CRC exhibits high ductility. Stress concentration factor (SCF) is introduced to measure the stress 
concentration degree. It is found from the results that SCF increases significantly as the shape factor of the 
elliptic hole increases. Soft filler decreases the SCF and reduces the affected area of the hole along x and y 
directions. This research is helpful in explaining why CRC can exhibit ductile failure mode even in low 
temperature. A modified stress-strain relationship for CRC which is proposed in section 3 shows based on this, 
theoretical formula for the flexural capacity of CRC beam, which take into account the peak compressive strain 
and the ultimate compressive strain of CRC, is established. The neutral axis moves downward remarkably 
because of the large ultimate compressive strain of CRC, which results in the compressive zone of CRC beam 
increases significantly. The calculation results show that with the same grade of concrete strength the flexural 
capacity of CRC beam is increased by 0.10% (when rubber content is 0.12%, namely, λ1≤1.5;λ2≤2.0). An 
example shows that the flexural capacity of the CRC beam is increased by 7.6%. Based on the modified 
stress-strain relationship of CRC, ductility evaluation method is used by means of curvature ductility factor 
(CDF). The method indicates that the peak compressive strain and the ultimate compressive strain of concrete 
affect the ductility of concrete beam significantly as well as reinforcement ratio and yield strength of steel. In 
the end, a comparison shows that the calculated ductility of a reinforced CRC beam is about as 1.642.59 
times as that of a conventional concrete beam. 

4. Conclusions 
By analysis of the full text, it can be seen that rubber concrete has been highly valued because of its 
distinctive features of improving features of ordinary concrete including its elasticity and tightness and 
preventing problems such as cracks in the concrete. In addition, powder and rubber particles are mostly 
produced from discarded automobile tires, promoting the disposal of waste rubber. As a consequence, the use 
of rubber concrete is very common in current building construction. In conclusion, the selection of powder and 
rubber particles as well as actual matching proportions must be highly valued in order to well control the 
performance of rubber concrete. Plus, after fabrication of rubber concrete, simple experiments can be 
conducted in the field to ensure that its performance meets the needs of actual construction.  

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