EFFECT OF SOME TYPES OF COATINGS ON THE PERFORMANCE OF REED IN CEMENT MEDIA
European Scientific Journal October 2014 edition vol.10
EFFECT OF SOME TYPES OF COATINGS ON THE PERFORMANCE OF REED IN CEMENT MEDIA
Dr. Adil.M.Abdullatif 0
0 Civil Engineering Department, College of Engineering, University of Nahrain
The recent years have witnessed some serious attempts to use wood and vegetable fibers, such as reed fibers, in concrete as reinforcement or as light weight aggregate due to its low cost and relatively high tensile strength.Unfortunately the durability of these materials in concrete media is very low due to the high PH value of concrete. The effect of some coatings on the tensile strength, modulus of elasticity and absorption of reed exposed to media of high PH value is investigated. The effects of these coatings on the modulus of rupture of cement mortar prisms reinforced with reed are also investigated. Many coatings, namely, epoxy paint, styrene -butadiene rubber (SBR), polyvinyl acetate (PVA), and liquid mastic were used. It is concluded that epoxy paint has shown the most superior qualities as a coating by exhibiting less absorption, higher tensile strength, higher modulus of elasticity and higher modulus of rupture.
Reed; durability; modulus of rupture; epoxy; concrete; tensile strength; modulus of elasticity
Many attempts have been made to use sawdust in concrete to reduce
the density and improve the thermal conductivity of concrete or to make
nailing concrete (Neville, 1995). Nailing concrete is a material into which
nails can be driven or hammered .Several attempts were ,also, made to use
vegetables fibres such as reed and bamboo as reinforcement to improve the
tensile and flextural strength of concrete and cement mortar(Raouf,1975).
Many investigations have been carried out scince 1914 in China to use
bamboo as reinforcement in concrete (AL-Ossi and AL-Ali,1989). In 1939
,many studies have been carried out by Datta in Germany in the same field.
Such attempts have had economical advantages in the past by reducing
demand on steel in war times.In some counteries ,rice husks have been used
to make concrete (AL-Ossi and AL-Ali,1989).
The major problem facing these attempts is the detorieration of
cellilose and hemicellilose in cement media as the PH value of cement paste
is very high (aproximately 13) . One more point that must be mentioned is
that the wood and vegetable fibers have also many other disadvantages:
1- These materials absorb or release water depending on their
environments . These processes lead to volume changes and ,as a
result, decrease the bond with surrounding matrix (AL-Ossi and
2- The surface of vegetable fibers is unfortunately smooth which
reduces the bond with the matrix.
3- The differences between the coefficient of thermal expansion of the
vegetable fibers and that of cement mortar or concrete may lead to
reducing the bond and ,in other cases, to disrupt the matrix materials.
4- The adverse effect of termite and fungi on wood and vegetable fibers.
In spite of these disadvantages reed has the advantage of relatively
high tensile strength (about 150 MPa) , low density( 0.413- 0.852 g\cm3)(
Abdul-Lateef and Al-Attar,2013) and low cost.
Many measures, however, were suggested to overcome these
disadvantages (Gram, 1983and NCCL ,1986):
1- Using these fibers as bundles to decrease the surface area exposed to
2- Using fibers saturated with water to eliminate moisture absorption .
3- Treating the fibers with certain chemical such as Sodium sulfate and
4- Overlaying the fibers with certain materials such as epoxy paint,
5- Reducing the PH value of the matrix by adding fly ash or by using
high alumina cement.
6- Overlaying the external surface of concrete by water proofing
The present work is designed to study the role of some coatings on
reducing the harmful effect of concrete media on the mechanical properties
of reed. To simulate the chemical action of concrete media, lime- saturated
water was used for this purpose.
1n 1988 Abdel-Rahman studied the durability characteristics of date
palm frond stalks as Reinforcement in Structural Concrete (Abdel Rahman,
1988).He concluded that asphaltic coating resulted in 10-100% decrease in
water absorption of the samples.
Gram (Gram, 1983) suggested an accelerated method to assess the
durability of natural fibers in high PH media by cyclic wetting and drying. In
wetting cycle the fiber reinforced concrete sample were exposed to 50
centigrade for 3 hours, in the other hand, in drying cycle the samples were
exposed to 20 centigrade and relative humidity of 95%.
Sink (NCCL, 1986) studied the resistance of some fibers (such as
sisal and coir) to basic media .He concluded that coir has good resistance to
G.Ramakhnaris and T. Sundararajan (Ramakhnaris and Sundararajan,
2005) presented the results of the variation in chemical composition and
tensile strength of coir, sisal, jute and Hibiscus cannabinus fibers, when they
are subjected to alternate wetting and drying and continuous immersion for
60 days in three liqued mediums namely, water, saturated lime and sodium
hydroxide. Compressive and flexural strengths of cement mortar (1:3)
specimens reinforced with dry and corroded fibers were determined after 28
days of normal curing. From the results it was observed that there was
substantial reduction in the salient chemical composition of all the four
fibers, after exposure in the various mediums. Coir fibers are found to retain
higher percentages of their initial strength than all other fibers, after the
specified period of exposure in the various mediums. The compressive and
flexural strengths of all natural fiber reinforced mortar specimens using
corroded fibers are less than the strength of the reference mortar (i.e. without
fibers) and fiber reinforced mortar specimens reinforced with dry natural
G. Ramakrishna, et al, (Ramakrishna, et al, 2010) stated that
durability of natural fiber cement composite can be evaluated on the basis of
flexural toughness and it has a special significance. Toughness of a natural
fiber composite can also be evaluated by impact tests, which helps in
realistic assessment of ductility of the above composite. Evaluation of
durability of a natural fiber composite by residual impact strength and
flexural toughness index and their comparison are presented and discussed.
Impact strength values could be used to assess the durability of natural fiber
composites in contrast to the conventional toughness indices used for
composites, in general.
Ordinary Portland cement was used in this research. Table (1) shows
the chemical and physical properties of this cement which conform to the
Iraqi specification ( I.Q.S 5,1984).
Natural sand from Karbala was used. It conforms to the Iraqi
specification ( I.Q.S 45-1984).
Lime was used to simulate the cement media. The PH value of the
lime was tested and was found to be 12.7 which approximately equals the
(PH) value of cement solution (12.9).
Other chemical properties of lime are shown in Table (2).
Three groups of samples were collected from three different places in
Baghdad ( Kadimiya, Latifiya,and Radwania)
3-1-5- Overlaying materials:
3-1-5-1- Liquid mastic:
This material which is usually used as water proofing agent is
available in the local markets . It is in liquid state at normal temperatures.
3-1-5-2- Styrene butadiene rubber (SBR):
This material is also available in the local markets .The type used in
this research is Swiss-Egypt product. SBR is a mixture of approximately 75
percent butadiene (CH2=CH-CH=CH2) and 25 percent styrene
(CH2=CHC6H5). In most cases these two compounds are copolymerized
(their single-unit molecules linked to form long, multiple-unit molecules) in
an emulsion process, in which a soaplike surface-acting agent disperses, or
emulsifies, the materials in a water solution.
3-1-5-3- Polyvinyl acetate (PVA):
Polyvinyl acetate is a rubbery synthetic polymer with the formula
(C4H6O2)n. It belongs to the polyvinyl esters family with the general formula
-[RCOOCHCH2]-. It is a type of thermoplastic (12). This material was
available in the local markets in small tines .The type used in this research is
3-1-5-4- Epoxy paint:
This material is available in the local markets . It is produced by
Modern paint industries company (Iraq).
3-2 - Testing Program:
The following tests were carried out on reed mortar samples:
3-2-1- Absorption test:
Six reed samples from each group were weighed after being dried in
oven to 65 centigrade .After that the samples were submerged in water for
48 hours and weighed again . The absorption was calculated according to the
3-2-2- Tensile strength:
The authors failed to carry out this test in a universal testing machine
for concrete or steel because the specimens crushed and badly damaged at
the point of grips . Therefore, twelve specimens (six with a node in the free
length and six without a node) for each sample were tested in the Zwick 1454
tensile testing machine with capacity of 10 kN (Fig. 1). This machine is
designed to test plastics and leather and is available in the Central
Organization for Standardization and Quality Control, COSQC, Baghdad.
The tested specimens were shaped as strips with the dimensions of (25200)
Fig. 1: The Zwick 1454 tensile testing machine
3-2-3-. Modulus of elasticity:
The same machine (which has the capability of recording the
elongation of reed specimen against the applied load) was used to obtain
Modulus of elasticity.The modulus of elasticity of each sample was
calculated by the following equation:
E: modulus of elasticity, GPa.
P: applied load within elastic range, N.
L: span length between supports, mm.
A: cross-sectional area, mm .
l: elongation, mm.
3-2-4- Modulus of rupture:
(150*50*700) mm mortar prisms (cement 1: sand 3) were used for
modulus of rupture test. The prisms were reinforced with 4 reed slices (1.5
cm width). The reinforcement ratio was 1%. Hydraulic compression
machine of (2000) kN capacity ELE digital machines was used with a simple
beam at the third-Point loading according to the (ASTM C 78-04). The
ultimate tensile strength in flexural (modulus of rupture) was calculated
using the following formula:
fr = PL/bd2 .. (3)
fr: modulus of rupture, (MPa).
P: maximum applied load recorder by tested machine, (N).
L: average length of specimen, (mm).
b: average width of specimen, (mm).
d: average depth of specimen, (mm).
The reference sample without coating was tested at the age of 28 days, while
the other samples were tested at 120 days after 30 cycles of wetting and drying of 48
4-Results and discussion:
Table (3) shows the results of absorption tests for reed samples with
different types of coating. It is obvious that samples with epoxy paint exhibit
less absorption than that of other samples. It means that this paint is the most
efficient coating in decreasing the water absorption. It is also shown that all
types of coatings used in this research have desirable effects on the water
absorption of reed.
The results of tensile strength and modulus elasticity of reed samples,
after exposure to water saturated with Ca(OH)2 for 90 days, is shown in
Table (4).The samples with epoxy paint showed the highest tensile strength
and modulus elasticity. This is in line with the results of absorption tests. The
lesser the water absorption the more efficient performance against the effect
of deterioration due lime action.
It is also shown that the samples coated with mastic, PVA, and SBR
showed less tensile strength and modulus elasticity than that of the reference
sample. It could be attributed to the deterioration of cellulose and
hemicellulose of fibers exposure to water saturated with lime.
The samples coated with epoxy, however, showed no decrease but
increase in tensile strength and modulus elasticity. This may be due to the
improvement of mechanical properties of reed resulting from epoxy
Table (5) shows the results of modulus of rupture results for mortar
prisms reinforced with reed and exposed to 30 cycles of wetting and drying.
According to this Table, it could be stated that:
a- There is a decrease in modulus of rupture for sample without coating
after exposure to wetting and drying cycles. It could also be attributed
to the deterioration of cellulose and hemi-cellulose fibers exposed to
water saturated with lime.
b- The decrease in modulus of rupture for samples reinforced with
coated reed of PVA and SBR after exposure to wetting and drying
cycles is less than that for samples without coating.
c- Samples with reed coated with epoxy paint exhibited increase in
modulus of rupture. It is in line with the results of tensile strength and
modulus of elasticity of reed samples.
For the investigated reed samples and mortar reinforced with reed,
the following conclusions could be The samples of reed with epoxy paint
exhibit less absorption compared to other samples.
1- After exposure to water saturated with Ca(OH)2 for 90 days ,the
samples with epoxy paint showed the highest tensile strength and
2- There is a decrease in the modulus of rupture for samples of
mortar reinforced with uncoated reed and after exposure to drying
and wetting cycles. Similar trend is shown by mortar reinforced
with reed coated with PVA and SBR.
3- Mortar samples reinforced with reed coated with epoxy paint
exhibited increase in modulus of rupture.
Chemical and physical properties of cement
Initial setting time
Initial setting time
Table (3) Absorption of reed with different types of coating
Type of coating Absorption % *
Table (4)Tensile strength and modulus of elasticity of reed samples after exposure to water
saturated with Ca(OH)2 for 90 days
Tensile strength ( MPa) *
Table ( 5 )Modulus of rupture results for mortar prisms reinforced with reed and exposed to
30 cycles of wetting and drying
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