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0Accepted Manuscript
Material development for a sustainable precast concrete block pavement R. Bharathi Murugan, C. Natarajan, Shen-En Chen
PII: S2095-7564(16)30189-1
DOI: 10.1016/j.jtte.2016.09.001
Reference: JTTE 82
To appear in: Journal of Traffic and Transportation Engineering (English Edition)
Please cite this article as: Bharathi Murugan, R, Natarajan, C., Chen, S.-E., Material development for a sustainable precast concrete block pavement, Journal of Traffic and Transportation Engineering (English Edition) (2016), doi: 10.1016/j.jtte.2016.09.001.
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1 Original research paper
2 Material development for a sustainable precast
3 concrete block pavement
5 R. Bharathi Murugana*, C. Natarajana, Shen-En Chenb
6 a Department of Civil Engineering, National Institute of Technology, Tiruchirappalli, Tamil Nadu, India
7 b Department of Civil and Environmental Engineering, University of North Carolina at Charlotte, Charlotte,
8 NC 28223, USA
9 Abstract
10 Portland cement concrete (PCC) and asphalt concrete (AC) are the most common roadway and highway
11 construction materials which are more suitable for continuous slab pavements. The durability of these
12 materials is highly dependent on construction quality and techniques, and both materials are difficult to
13 repair. Heavy rain storms in India have recently revealed several roadway pavement failures and resulted
14 in significant repair costs. Interlocking block type pavements are simpler to construct and maintain than
15 both PCC and AC pavements but, have only been used for slower traffic roads due to weak interlocking at
16 the joints. To improve the quality of block pavements, blocks made of PCC with waste tire crumb rubber
17 partially replacing river sand (fine aggregate) are suggested. The joint interlocks can be further improved
18 by modifying the block geometry. The material is completely recycled and is deemed more superior than
19 concrete pavements when repair and construction techniques and costs are concerned. This paper
20 presents the material characterization of Rubberized Concrete Blocks (RCB) using crumb rubber particle
21 size ranging from 0.075 mm to 4.75 mm to partially replace the fine aggregates. It also discusses the
22 advantages of RCB over continuous material pavements.
23 Keywords: Rubberized concrete; Crumb rubber; Damage mechanism; Material characterization and
24 Impact energy.
28 'Corresponding author. Tel.: +91 9488024542.
29 E-mail address: rbmmecivil@gmail.com (R.B. Murugan).
32 1 Introduction
33 Conventional modes of roadway and highway pavement construction utilize predominantly in-situ, large
34 dimension and slab-based techniques with either Portland cement concrete or hot mixed asphalt concrete
35 (AC). Due to the wear, tear and abuses of daily traffic, paved roads experience usage damages and
36 require constant maintenance. For example, based on the 2010 capital spending estimate, the US spends
37 $65.3 to $86.3 billion annually for highway condition maintenance (US DOT, 2013). Furthermore, the
38 maintenance of roadways require extended traffic closure periods to complete the patching, overlaying,
39 cutting and curing of materials involved, all resulting in additional financial losses. The key disadvantages
40 of conventional roadway in-situ construction and maintenance are inconveniences to drivers and
41 additional costs associated with extensive site operations. In addition, there is also the seasonal
42 constraint to on-site constructions such as concrete curing or hot mix asphalt placement during low
43 temperatures, that can result in sub-standard products. An alternative pavement technology is the use of
44 block pavements. Despite advances in concrete block pavement technologies, the use of concrete block
45 pavement (CBP) remains limited and must be promoted.
46 State-of-the-art reviews of CBP technologies indicate that modern CBPs' have excellent engineering
47 properties and low life cycle costs. They are easy to construct and maintain, and have a very good
48 aesthetic appearance as compared to conventional pavements (i.e., concrete and asphalt). Additionally
49 CPB's can be easily replaced, thus minimizing the waste of materials and time for construction. This last
50 advantage makes CPB's more sustainable than conventional pavements.
51 The durability of CPB is mainly dependent on the quality and strength of the paving block. However,
52 the block-block interface conditions are also critical to the overall performance of the pavement. The
53 paving blocks can be produced in different grades of concrete, shapes and sizes (Shackel, 1990). Several
54 standards and specifications, such as the Indian Standards (Bureau of Indian Standards, 2006), the
55 British Standards (BS EN 1338:2003) (British Standards Institution, 2003), the ASTM C936/C936M
56 (ASTM, 2015), are available for the detailed definition and basic requirements of the paving blocks. In
57 earlier global standardization efforts, Houben et al. (1984) gave a comprehensive review of all published
58 standards, which documented block thickness of 140 mm in some cases.
59 For typical applications, the small element of precast paving unit is used as a surface course and the
60 bedding sand provides a more flexible response compared to conventional pavements (Singh et al., 2012).
61 Thus, the following factors can influence the structural performance of CBP: (1) paving blocks (i.e., shape,
62 size, thickness and laying pattern); (2) bedding sand (i.e., thickness, grading, angularity and moisture
63 content); (3) base and sub-base (i.e., material type and thickness); and (4) sub-grade (i.e., material type
64 and strength) (Soutsos et al., 2011). Joints can be filled with sand to enhance the interface friction.
65 Polymer filler material can be used to stabilize the joint sand and reduce water infiltration.
66 Loading frequency and scenarios are also critical to the durability of block pavements. The standard IS
67 15658:2006 clearly indicates that the strength and thickness of paving blocks are decided based on the
68 traffic volume. For high volume traffic roads, there is a need to carry large amounts of load, thus requiring
69 stronger and thicker paving blocks. The sub-base and bedding sand thickness are selected based on
70 required bearing capacity of the base course design. For base course with lower bearing capacity, then
71 the required sub-base and bedding sand materials would be more.
72 Manufactured paving blocks have a high compressive strength, but they can still fail during heavy
73 traffic loads due to weaknesses and result in spalling and cracks. Therefore, CPBs require high flexural
74 strength and toughness to sustain a heavy traffic load. However, it is difficult to improve the flexural
75 capacity of conventional concrete block without modifying its material properties. Therefore, there is a
76 need to modify conventional concrete ingredients to improve the toughness of the paving block. In this
77 paper, waste tire crumb rubber mixed with conventional concrete is suggested as a sustainable way to
78 improve block toughness. The result is a Rubberized Concrete Block Pavement (RCBP), which has been
79 shown to have a good resistance to cracking and fracture as compared to conventional concrete (Li et al.,
80 2004; Ling et al., 2009b).
81 Toughness is a parameter that describes the fracture response at a sudden impact load. The
82 toughness of paving blocks can help quantify their resisting properties to cracking induced by frequent
83 wheel impacts. In this study, crack resistance is evaluated based on the impact test suggested by ACI 544.
84 2R-89. As seen from the test results collected, the impact energy of the paving block is calculated for the
85 first cracking load and the load at complete failure. The ductility index is also measured from the first crack
86 and failure impact energy.
87 The authors of this paper focus on fundamental studies of concrete material modification with the
88 partial replacement of fine aggregates with crumb rubber from waste tires. Crumb rubber is made of
89 shredded waste tires, and, is thus a waste reduction technique to sustains the living environment. Waste
90 tire utilization has been studied as early as the 1990s (Siddique and Naik, 2004). The main advantages of
91 crumb rubber utilization in concrete include lower density, higher impact and toughness resistance,
92 enhanced ductility, and better sound insulation. However, waste tires are very difficult to handle because
93 they are not naturally biodegradable (El-Gammal et al., 2010; Issa and Salem, 2013; Khaloo et al., 2008).
94 Out of the three conventional methods of waste tire handling (i.e., reuse, burning and dumping), the
95 burning of waste tires results in large amounts of Co, NO^ and SO^ emissions. Dumping waste tires can
96 also create serious land hazard and settlement effects (EPA, 1999).
97 Previous efforts to use waste tire for construction applications involved shredding the waste tires into
98 small particles, then using them as concrete aggregate replacements (Siddique and Naik, 2004). In this
99 paper, the authors explore the possible use of waste tire crumb rubber as a partial replacement of fine
100 aggregates by volume in pavement blocks. The study focuses on the use of rubberized concrete blocks in
101 roadway pavement applications.
102 2 Damage mechanisms of pavements
103 Fig. 1 demonstrates the different conceptual failure modes involved in PCC pavement, AC pavement and
104 CBP pavements. In contrast to both PCC and AC pavements, block pavements involve joint action, which
105 may result in hinge formation. This presents the blocks with stress release and preserves their integrity.
106 AC pavement behavior is significantly affected by surface temperature due to solar radiation and ambient
107 conditions, where as such thermal effects are less pronounced in PCC and CBP pavements. RCBP and
108 CBP pavements share similar damage mechanisms. Both AC pavements and RCBP may involve crack
109 tip blunting due to the presence of rubberized material (i.e., rubber in tire and bituminous material in
110 asphalt). As seen in Fig. 1(b), concrete block pavement can be designed to optimize the flexural behavior
111 of the block pavement system and moderate interactions between block and joint behaviors.
Important aspects of rubberized concrete are possible strain softening and fracture arrest mechanisms due to the presence of rubber shreds within the concrete material which is not shown in Fig. 1. A previous study has shown that rubber shreds can reduce the plastic shrinkage cracking of concrete, which can significantly enhance its durability (Twumasi-Boakye, 2014). The proportioning of amount of rubber shreds can help reduce shrinkage behavior and optimize material performance. This study characterizes the block behavior with different proportions of rubber shred mix. (a) (b)
Wheel load i
Single layer PCC pavement
Hinge formation
Dimple rupture for clearagel
Void coalescence for first crack advancing
Void nucleation and growth ;
Stretch zone development:
Plastic zone formation: Notch + fatigue crack :
¡00 o „ooo
O) . «
u S G £
CO O £ ^ w £ £ U
M CL»
Í-H to
Crack at steady stage
'Onset of facture instability (crack initiation)
/Crack tip blunting
Crack growth A a
122 Fig. 1 Failure modes of different pavements. (a) PCC pavement. (b) Concrete block pavement (Soutsos et
123 al., 2011). (c) AC pavement (Tang, 2014).
125 3 Materials and methods
126 3.1 Materials
127 Ordinary Portland cement 53 grade (OPC 53) conforming to IS 12269:1987 is used throughout this study
128 (Bureau of Indian Standards, 1987). The cement properties were determined, and test results are
129 summarized in Table 1. River sand was used as the original fine aggregate. River sand properties are
130 defined per IS 383:1970, where the specific gravity was found to be 2.65 and fineness modulus of 2.45
131 was used (Bureau of Indian Standards, 1970). Crushed granite stones with a maximum size of 20 mm,
132 specific gravity of 2.63 and fineness modulus of 7.2 were used as coarse aggregates. The shredding of
133 waste tires produced crumb rubber particles that passed through a sieve size of 4.75 mm and was
134 determined to have specific gravity of 0.689.
135 Table 1 Cement properties.
Sl. No. Properties Results IS 12269:1987 requirements
1 Normal consistency 31% -
2 Specific gravity 3.14 -
3 Initial setting time (min) 65 Not < 30
final setting time (min) 280 Not > 600
4 Fineness (m2/kg) 320 225
5 Compressive strength
7 d (N/mm2) 38.60 37.00
28 d (N/mm2) 56.96 53.00
137 3.2 Mix proportion
138 UNI-Paver 50 mm thick paving blocks were manufactured at a local plant for compressive strength and
139 flexural strength tests. To determine the static strength and moduli parameters, cylinders with a 150 mm
140 diameter and 300 mm height were cast. An M20 grade concrete with a cement, fine aggregate and coarse
141 aggregate ratio of 1:1.89:2.88 and water to cement ratio of 0.5 were used as the control. Table 2 shows
142 the concrete mix design used in this study.
143 Table 2 Concrete mix design.
Sl. No. Mix ID Crumb rubber replacement (%) Mix ratio C:FA:CA:CR Slump (mm)
1 R0 Control mix 1:1.89:2.88:0.00 48
2 R5 5% FA replaced by CR 1:1.78:2.88:0.09 50
3 R10 10% FA replaced by CR 1:1.71:2.88:0.18 52
4 R15 15% FA replaced by CR 1:1.62:2.88:0.27 56
5 R20 20% FA replaced by CR 1:1.53:2.88:0.36 61
6 R25 25% FA replaced by CR 1:1.44:2.88:0.45 69
144 Note: C: Cement; FA: Fine aggregate; CA: Coarse aggregate; CR: Crumb rubber.
146 3.3 Test methods
147 In this paper, waste tire fines are mixed in PCC blocks with different percentage replacements of fine
148 aggregates (i.e., 5%, 10%, 15%, 20% and 25%). The blocks were then tested for compressive strength,
149 flexural strength, static modulus of elasticity and impact energy. The results comparing concrete with
150 crumb rubber and normal concrete without rubber are presented in the following.
151 The compressive strength and flexural strength test was performed in accordance with IS 15658:2006
152 and the static modulus of elasticity test was performed in accordance with IS 456:2000 (Bureau of Indian
153 Standards, 2000, 2006). The IS 456:2000 recommends an empirical relation between the static modulus
154 of elasticity and compressive strength of concrete, expressed below as Eq. (1).
160 161 162
168 169
E = 5000f (1)
where Ec is static modulus of elasticity in MPa, fck is characteristic compressive strength of concrete at 28 d in MPa. IS 456:2000 further suggests that the flexural strength, f, of concrete can be defined as Eq. (2).
f = 0-7f (2)
Guidelines from ACI committee suggest that the impact energy from a load can be determined via the free fall of a drop weight onto the center of at paving block (ACI, 1999). A 4.54 kg weight was lifted to 0.457 m above the specimen and then released. The drop weight impact testing machine is shown in Fig. 2. The weight was dropped repeatedly, and the blows required to produce the first visible crack and complete failure of the specimens were noted. The impact energy is then calculated for each paving block using the following equation.
v = V 2(0.9 g )h
where U is impact energy, n is number of blows, m is weight of the hammer (4.54 kg), v is drop weight hammer velocity, g is gravitational acceleration, and h is drop height (0.457 m). A factor of 0.9 was used to account for the effect of air resistance and friction between the lifting weight and guided rails.
Hammer
Specimen
Base plate
171 Fig. 2 Impact testing machine.
173 4 Material characterization results
174 4.1 Workability
175 Table 2 shows that the addition of crumb rubber increased the concrete's slump, indicating that the crumb
176 rubber improved the workability of the concrete material. Since crumb rubber does not absorb water as
177 compared to river sand, less water is needed for rubberized concrete to achieve good workability.
179 4.2 Compressive strength
180 The 28-day compressive strength, on the other hand, reduced with increasing crumb rubber replacement.
181 Fig. 3 shows the decreasing strength versus increasing rubber replacement. This observation is
182 consistent with several previous studies. 25% of rubber replacement represents a strength reduction of
183 nearly 50%. The decrease in 28-day compressive strength of concrete with 5%, 10%, 15%, 20% and 25%
184 waste tire crumb rubber was observed to be 7.85%, 13.34%, 21.92%, 29.90% and 46.44%, respectively,
185 when compared to normal concrete without rubber replacement. The strength reduction due to crumb
186 rubber addition may result from the fact that at first the rubber particles are much softer than the cement
187 paste, resulting in rapid crack propagation around the rubber particles. This leads to failure in the rubber-
188 cement matrix. Since rubber particles have more air content, they can increase the voids within the
189 concrete and decrease the compressive strength of the paving block (Al-Mutain et al., 2010; ; Guneyisi et
190 al., 2004; Khatib and Bayomy, 1999).
5 10 15 20
Crumb rubber content (%)
Fig. 3 Compressive strength as a function of crumb rubber replacement. 4.3 Modulus of elasticity
200 201
202 203
To determine the rubber crump replacement effect on the Young's modulus, a value is computed from Eq. (1) and compared to the test results, which are shown in Fig. 4. The modulus for normal concrete is 29.43 MPa at 28 d, and the modulus decreases with increasing rubber content. Fig. 4 clearly shows that the measured moduli of elasticity are lower than the calculated values. Generally, normal concrete is more brittle when the modulus of elasticity is higher, and concrete mixed with a large volume of rubber is more ductile or flexible when the modulus of elasticity values are lower (Ling et al., 2009a). Therefore, it is proven that the addition of a low volume of crumb rubber into concrete notably increases the modulus of elasticity.
S 30 fr 25
I 20 %
[723 By experiment
Fwl By experience (IS 456:2000)
R0 R5 RIO R15 R20 R25 Mix ID
Fig. 4 Static modulus of elasticity as a function of crumb rubber replacement.
205 4.4 Flexural strength
206 A comparison of flexural strength and the computed values from Eq. (2) is shown in Fig. 5, where the
207 experimental results peak at 5.2 MPa for R15 rubber replacement concrete. The improvement in flexural
208 strength is limited to relatively small amounts of rubber crumb. In general, normal concrete is more brittle
209 with a higher modulus of elasticity when compared to rubberized concrete mixed with large volumes of
210 rubber, thus demonstrating a more flexible behavior (Ling et al., 2009a). However, empirical results
211 according to IS 456:2000 show a consistent decreasing flexural strength with increasing rubber
212 replacement contents, which contradicts the experimental results.
■G 4
■4—'
1223 By experiment
Km By experience (IS 456:2000)
R0 R5 R10 R15 R20 R25 Mix ID
Fig. 5 Flexural strength as a function of crumb rubber replacement.
215 The authors believe that the flexural strength increase of RCB concrete demonstrates a possible
216 bridging of rubber within the fracture zone, resulting in the arrest of fracture propagation. This
217 phenomenon is described as "strain hardening" in fiber-reinforced concrete under tension, where the
218 tensile behavior has demonstrated the fiber bridging within propagating cracks (Fantilli et al., 2009).
219 Soranakom and Mobasher (2007) describe the post-crack flexural responses of fiber reinforced concrete
220 as "deflection softening" or "deflection hardening" because of the effective activation of tensile responses
221 within the embedded fiber bridging, which is a function of the amount of fiber and the anchor strength of
222 the fibers. The material characterization tests performed in this study demonstrate the flexural
223 performance of RCB material, validating earlier speculation that block pavements using RCB can benefit
224 from both the joint interaction and flexural strength of individual blocks.
226 4.5 Impact energy
227 The number of blows required to produce the first visible crack and complete failure for each type of
228 paving block are presented in Table 3. Based on the number of blows the first crack impact energy and
229 failure impact energy were calculated using Eq. (3) and plotted in Fig. 6. Compared to conventional
230 concrete paving blocks, the first crack impact energy increased by 34.48%, 51.23%, 71.92%, 91.62% and
231 112.31%. The failure impact energy increased by 35.81%, 53.02%, 74.88%, 96.27% and 118.14% to 5%,
232 10%, 15%, 20% and 25% of sand replaced by crumb rubber by volume, respectively.
234 Table 3 Impact test results for plain and rubber mixed concrete.
Mix ID No. of blows Average no. of blows Impact energy (J) Average impact energy (J) Ductility Index Average ductility index
First crack Failure First Failure crack First crack (N1) Failure (N2) First First crack crack N2/N1 Average of N2/N1
22 25 399.96 454.50 1.136
23 25 418.14 454.50 1.086
R0 26 27 24.2 25.6 472.68 490.86 439.96 465.41 1.038 1.059
22 22 399.96 399.45 1.000
28 29 509.04 527.22 1.035
39 41 709.02 745.38 1.051
36 42 654.48 763.56 1.166
R5 38 43 38.2 41.4 690.84 781.74 694.48 752.66 1.131 1.085
38 40 690.84 727.20 1.052
40 41 727.20 745.38 1.025
45 48 818.10 872.64 1.066
48 49 872.64 890.82 1.020
R10 46 48 45.6 49.6 836.28 872.64 829.01 901.73 1.043 1.091
47 49 854.46 890.82 1.042
42 54 763.56 981.73 1.285
51 56 927.19 1018.09 1.098
52 57 945.37 1036.27 1.096
R15 54 62 52.6 58.0 981.73 1127.17 956.27 1054.45 1.148 1.102
56 60 1018.01 1090.81 1.071
50 55 909.01 999.91 1.100
59 66 1072.63 1199.89 1.118
60 65 1090.81 1181.71 1.083
R20 62 69 59.2 65.4 1127.17 1254.43 1076.26 1188.98 1.112 1.104
58 64 1054.45 1163.53 1.103
57 63 1036.27 1145.35 1.105
63 70 1145.35 1272.61 1.111
65 72 1181.71 1308.97 1.107
R25 66 73 63.8 70.8 1199.89 1327.15 1159.89 1287.15 1.106 1.109
64 70 1163.53 1272.61 1.093
61 69 1108.99 1254.43 1.131
E3 First crack E23 Failure
R0 R5 RIO R15 R20 R25 Mix ID
Fig. 6 Impact energy of paving block.
239 With an increasing replacement percentage of shredded rubber, there is an increase in the impact
240 energy of paving blocks, which is observed by other researchers such as Nilli and Afroughsabet (2010),
241 Yildirim et al. (2010), and Al-Tayeb et al. (2012). This trend holds true for both impact energies at first
242 crack and at failure. The impact resistance of R25 is approximately twice that of R0 because crumb
243 rubber absorbs more energy. This proves that rubber acts as a fibre and an effective crack arrestor, when
244 an impact load is encountered. Thus plain concrete exhibits an early brittle failure when compared to fibre
245 reinforced concrete which shows better ductile properties (Swamy and Jojagha, 1982). The failure mode
246 of concrete depends on the cement matrix strength, aggregate strength and bond strength of the fibre with
247 aggregate matrix.
248 4.6 Ductility index
249 There are different definitions for ductility index including one based on displacement measurements
250 (Maghsoudi and Bengar, 2011). In this case, the ductility index is defined as the ratio of energy absorbed
251 at failure to energy absorbed at first crack (Senthilvdivel et al., 2014). Fig. 7 shows variations in the
252 ductility index of the wet cast paving blocks based on the crumb rubber replacements at various
253 percentages. An increase in the ductility index value is observed when the percentage of crumb rubber in
254 concrete mix increases. The percentages of sand replacement by crumb rubber (i.e., 5%, 10%, 15%, 20%
255 and 25%) and the associated increases within the ductility index are 0.93%, 1.16%, 1.82%, 2.3% and
256 2.94%, respectively.
R0 R5 RIO R15 R20 R25
257 Mix ID
258 Fig. 7 Ductility index of paving block.
260 5 Discussions
261 A modified block response diagram is shown in Fig. 8 to demonstrate the micro-macro behavior of the
262 likely moderation of block flexural responses and joint interlocking (hinge formation) mechanisms that
263 resist over-bearing wheel loads. As shown in Fig. 8, the block/joint system provides a more uniform
264 response against wheel loads with flexural hardening, and, at the same time, allows block separation at
265 the ultimate load. Thus, a stronger response system is created using RCB's.
Flexural bending
267 Fig. 8 Flexural hardening and joint interlock in the load bearing mechanism of RCBP.
269 The current study only involves the testing of a single block element and does not accurately reflect
270 the block-block-base interactions. Fig. 8 shows that the flexural response of the loaded individual block
271 may lie opposite to the formation of the joint hinge, resulting in reduced stress at the joints. This
272 mechanism is missing in continuous slab pavements and further proves the advantage of using blocked
273 pavements in roadway loading. However, such tests require multiple block elements and are beyond the
274 scope of this paper.
275 Additional enhancements to improve the impact resistance of pavement blocks, including the
276 placement of black toppings on block pavements have also been introduced for airplane runways, which
277 can also be considered for highway and road way applications.
279 6 Summary and conclusions
280 This paper dicusses a series of tests conducted to characterize concrete pavement blocks made with
281 partial replacement of fine aggregates with waste rubber in the form of fine shredded crumbs. The tests
282 conducted include strength tests and determinations of the modulus of elasticity and compressive and
283 flexural strengths. Comparisons to conventional concrete blocks include derived parameters, such as the
284 impact energy and ductility index. The test results support the initial assumption that rubberized concrete
285 pavement blocks have superior toughness and strength compared to conventional concrete blocks. These
286 blocks help mechanize the combined load bearing mechanisms that combine the hinge formation at joints
287 and flexural bending of blocks. Observations from this study are summarized as follows.
288 • A series of tests investigate the behavior of concrete containing fine waste tire crumb rubber. The
289 following conclusions are drawn based on the test results of this study, which show that there is
290 an increase in slump values when crumb rubber content increases up to 25%. This means that
291 the workability of rubberized concrete improves due to the addition of rubber crumbs and is
292 acceptable in terms of the ease of handling, the placing and finishing of wet concrete as
293 compared to normal concrete.
294 • Compressive strength is reduced with increasing rubber content, and the static modulus of
295 elasticity of rubberized concrete is lower than normal concrete. However, the flexural strength of
296 concrete increases up to 15% of the crumb rubber replacement. When the percentage of crumb
297 rubber replacement increases over 15%, the flexural strength begins to decrease. An explanation
298 may be based on tension strain hardening.
299 • If the suggested fracture arrest by the embedded rubber crumb/fiber, then the integration of
300 flexural hardening and joint interlocking would make RCBP a superior roadway pavement system.
301 Future studies should focus on demonstrating the global behaviors of a block pavement system
302 with joint response monitoring.
303 • The impact resistance of the paving blocks was calculated in two stages: (i) first cracks impact
304 resistance and (ii) failure impact resistance. Both stages of impact resistance were increased by
305 the replacement of sand with crumb rubber up to 25% by volume of sand. The ductility index also
306 increased when the crumb rubber content increased up to 25%.
307 • The incorporation of rubber content to concrete, changes, the failure pattern from a brittle mode to
308 ductile mode, which displays the beneficial effects of Portland cement block with crumb rubber,
309 used in absorbing vibrations.
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R. Bharathi Murugan holds a M. E (Structural Engineering), is pursuing his PhD at National Institute of Technology, Tiruchirappalli, Tamil Nadu, India. His research interests include special concretes, sustainable construction materials, pavement materials and utilization of waste materials in concrete.
Dr. C. Natarajan holds PhD degrees in civil engineering from IIT Madras, India. He is a professor in the Department of Civil Engineering at National Institute of Technology, Tiruchirappalli, Tamil Nadu, India. His research interests pertain to the domains of forensic investigation, size effects on beam, traditional structures, corrosion resistance in concrete and pavement materials. His publications in these areas are well cited. 398
Dr. Shen- En Chen holds PhD degrees in civil engineering from West Virginia University, USA. He is a professor in the Department of Civil and Environmental Engineering at University of North Carolina at Charlotte, USA. His research interests pertain to the domains of power transmission structures, carbon storage in geological formations, remote sensing for bridge monitoring and forensic investigation His publications in these areas are well cited.
