experimental research of the permeable concrete with rigid polymeric fibers
TRANSCRIPT
Experimental Research of the Permeable Concrete with Rigid Polymeric
Fibers
LIU Xiaofan1, a, WANG Ting1, b and LI Jixiang1, c 1 School of Civil Engineering and Architecture, Wuhan Polytechnic University, China
Keywords: permeable concrete, rigid polymeric fibers, properties modification, experimental research
Abstract. In order to improve the hardness and strength of the permeable concrete, rigid polymeric
fibers are mixed to the concrete. Compressive strength tests, flexural strength tests, tensile splitting
strength tests and permeable performance tests prove that the rigid polymeric fibers could increase the
hardness and strength of the permeable concrete. The optimized mix proportion and forming process
are recommended to support the application of the permeable concrete.
Introduction
Permeable concrete is made of cement, water, coarse aggregate and other adding materials. Without
fine aggregate, permeable concrete has honeycomb structure with lightweight and porous properties,
which could reduce the surface runoff caused by heavy rain[1]
. The pavement made of permeable
concrete could also decrease the heat island effect, absorb the noise from the surface of the road and
purify the water. Permeable concrete pavement is of great benefit to the city ecological environment
protection.
The porous property of permeable concrete makes the contradiction to have the high strength and
good permeability performance at the same time, and this make the material has some defects when
applied in projects, such as low carrying capacity, small bond force of aggregates and more cracks. In
this study, rigid polymeric fibers is mixed into the permeable concrete to increase the strength and
durability of this material, which may improve the application field of permeable concrete.
Materials and Mix Proportion Design
Cement is the 32.5 composite portland cement. The length of the rigid polymeric fiber is 38mm.
Crushed stones with the particle size of 5-10mm are chosen as coarse aggregates. High efficiency
water reducers are added into the material to enhance the performance of the permeable concrete.
The mix proportion design should try to increase the strength of the permeable concrete while not
decrease the permeability performance. The rigid polymeric fibers act as bridges between the coarse
aggregates. The mix ratio of rigid polymeric fibers should fit the aggregate cement ratio and water
cement ratio[2]
. The detailed mix proportion is shown as table 1 and table 2.
Table 1 Amount of materials in permeable concrete
particle size
[mm]
water cement
ratio
cement
[kg/m³]
coarse aggregate
[kg/m³]
water
[kg/m³]
water reducer
[kg/m³]
target
porosity
5~10 0.35 368 1472 129 4.416 20%
Table 2 Mix proportion design of each experiment [kg/m³]
test number cement coarse aggregate water water reducer fiber
1 13.14 52.56 4.62 0.158 0
2(1%) 13.14 52.56 4.62 0.158 0.325
3(2%) 13.14 52.56 4.62 0.158 0.651
4(3%) 13.14 52.56 4.62 0.158 0.977
Advanced Materials Research Vols. 821-822 (2013) pp 1204-1207Online available since 2013/Sep/18 at www.scientific.net© (2013) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.821-822.1204
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 137.122.8.73, University of Ottawa, (eBOOK+Periodicals), Ottawa, Canada-17/08/14,13:35:21)
Specimen Cast and Construction Technology
There two different specimen size of the experiment. One is 50mm×150mm×150mm, which is used
to test the compress strength, tensile splitting strength, porosity and permeability coefficient of
permeable concrete. The other is 100mm×100mm×515mm, which is used to test the flexural strength.
The specimen cast and construction technology of permeable concrete is shown as figure 1. There
three steps should be noticed of this proceeding. (1) Dry mix first and then wet mix, that is, cements,
crushed stones and rigid polymeric fibers should be mixed firstly, which could make the fibers
homogeneous dispersion in the mixture. Then, water and other admixtures could be mixed together[3]
.
(2) The mixing process should try to make sure that every crushed stone be covered with slurry. (3) In
order to strengthen the connection among the aggregates and increase the connection effect of fibers,
the vibration time of the specimen should not too long. Otherwise, the slurry will separate from the
aggregate and form an impermeable layer on the bottom of the specimen, which would reduce the
water permeability of the concrete. The optimal vibration time is 10 to 20 second.
Fig. 1 Specimen cast and construction technology of permeable concrete
Analysis of Experimental Results
The volume percentage of rigid polymeric fiber in four groups is 0, 1%, 2% and 3%. Compress
strength tests, flexural strength tests, tensile splitting strength tests and permeable performance tests
are carried to prove the feasibility of rigid polymeric fiber in permeable concrete.
Compress strength tests. Figure 2 shows the 7 days age and 28 days age compress strength of
permeable concrete with different volume percentage of rigid polymeric fibers.
Fig. 2 Compress strength Fig. 3 Flexural strength Fig. 4 Tensile splitting strength
The mix of rigid polymeric fibers shows some affects to the compress strength of permeable
concrete. When the percentage of rigid polymeric fiber is 1%, the compress strength of permeable
concrete is higher than plain concrete. On one hand, the random distributed fibers act as a
three-dimensional net within the concrete specimen. Under the vertical load, the lateral deformation
of the concrete is constrained by the fibers, which could increase the compress strength of the
concrete[4]
. On the other hand, fibers could restrain the shrinkage cracks and make the concrete
relative density.
With the increase of the fiber volume percentage, the 7 days age and 28 days age compress strength
of the concrete become decrease. This proves the fiber content has an optimal ratio. While exceed the
aggregates
rigid fibers
mix mix 20s mix 90s mix 90s
water (20%) cement, water reducer water (80%)
die-filling stripping after 48h 7d, 28d maintenance shaping
Advanced Materials Research Vols. 821-822 1205
optimal ratio, the interface effect of the fiber will be exhibited, that is, the defects between the fiber
surface and aggregate will increase, which will decrease the compress strength of the concrete
indirectly.
Because of the limited bonding capacity, the application of 32.5 composite portland cement affect
the compress strength of the permeable concrete to some extend. 42.5 composite portland cement is
recommended as the adhesive material of the permeable concrete.
Flexural strength tests and tensile splitting strength tests. Figure 3 to 4 show the 7 days age and
28 days age flexural strength and tensile splitting strength of permeable concrete with different
volume percentage of rigid polymeric fibers.
Figure 3 shows that 1% fibers make the flexural strength of concrete lower than plain concrete. The
reason is that the fiber’s elastic modulus is lower than concrete. Low volume percentage of fibers
show more negative affects to the concrete. When the volume percentage add to 2% to 3%, the fiber’s
strengthen function become obvious and the maxim flexural strength of the concrete reach to
5.67MPa.
With the increase of the fiber’s volume percentage, the tensile splitting strength of permeable
concrete increase firstly and then decrease. The optimal fiber volume ratio makes the connection
effect of fibers obvious within the concrete. When applied loads, the high tensile strength of fibers
could absorb more energy and make the concrete’s splitting strength increase. Because the bond
strength of the slurry is limited, the continuous increasing of the fibers makes more initial defects,
while applied loads, the interface damage of aggregates and fibers appear earlier than the fracture of
fibers, which lead to the decrease of concrete’s tensile splitting strength.
Porosity tests and permeability coefficient tests. Figure 5 to 6 are the porosity and permeability
coefficient of permeable concrete with different fiber volume percentage. In this test, varying-head
method is adopted to test the permeability coefficient.
Fig. 5 Porosity properties Fig. 6 Permeability coefficient
Figure 5 and 6 show that the mixing of fibers has little effect to the porosity of permeable concrete,
but significant effect to the permeability coefficient. 3% volume ratio fibers could enhance the
permeability coefficient 3 times. This shows that fibers could increase the effective connected pores
while not add the pores of permeable concrete, that is, fibers could enhance the permeability of
concrete while not decrease the mechanical properties. Take the data of this test along, the
permeability of each specimen could meet the requirements of engineering applications.
Conclusions
Compressive strength tests, flexural strength tests, tensile splitting strength tests and permeable
performance tests prove the feasibility of mixing rigid polymeric fibers into the permeable concrete.
Conclusions are as followings.
(1) The mixing of rigid polymeric fibers suppresses the drying shrinkages and cracking of the
permeable concrete. The surface quality of the concrete is improved.
1206 Advances in Textile Engineering and Materials III
(2) Contrasted with plain concrete, the mixing of rigid polymeric fibers could increase the
compress strength of concrete. There is an optimal volume ratio of fibers. When exceed this ratio, the
compress strength of concrete decrease with the increase of fibers’ volume ratio.
(3) Rigid fibers have little effect to the porosity of permeable concrete, but significant effect to the
permeability coefficient, which could enhance the permeability of concrete.
Acknowledgements
This work was financially supported by the Science and Technology Project of Hubei Education
Department (Q20131702), Innovation Team Project of Hubei Education Department (T201107).
References
[1] Shen Rongxi, Wang Zhangshui, Cui Yuzhong. Fiber Reinforced Cement and Fiber Reinforced
Concrete. Beijing Industry Press, Beijing 2006 In Chinese
[2] Cheng Juan, Yang Yang, Chen Weizhong. Mix Proportion Design of Permeable Concrete.
Concrete 2006(10) In Chinese
[3] Richard C. Meininger. No-Fines Pervious Concrete for Paving. Concrete International: Design
and Construction. 1988, 1(8) 20-27
[4] Liu Weidong, Zhao Zhiguang.Performance of Permeable Concrete with Steel Fibers. Journal of
Building Strucutres 2006(6) In Chinese
Advanced Materials Research Vols. 821-822 1207
Advances in Textile Engineering and Materials III 10.4028/www.scientific.net/AMR.821-822 Experimental Research of the Permeable Concrete with Rigid Polymeric Fibers 10.4028/www.scientific.net/AMR.821-822.1204