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Procedia Engineering 00 (2017) 000–000
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Procedia Engineering 200 (2017) 325–332
3rd International Conference on Natural Fibers: Advanced Materials for a Greener World, ICNF
2017, 21-23 June 2017, Braga, Portugal
Mechanical behavior of mortar reinforced with sawdust waste
Haveth Gil*, Andrés Ortega, Jhon Pérez
Politécnico Colombiano Jaime Isaza Cadavid, Facultad de Ingenierías, Carrera 48 N° 7-151, Medellín 050022, Colombia
Abstract
Compressive strength, density and dynamic elastic modulus of mortar reinforced with wood sawdust wastes (WSW) were
investigated. Additions of 0, 0.5, 1 and 3% by weight of (WSW) were used. The mechanical influence of sawdust was followed
after 7, 30 and 90 days of curing. Scanning electron microscope (SEM) was used to characterize the morphology of the
composites and to find the adhesion behavior of sawdust. The results show that compressive strength increases with sawdust
content up to 0.5%. Using sawdust content larger than 1%, produces mortars with an excessive loss of compressive strength,
especially for 3% of WSW. Lightweight mortar was obtained only for 3% of WSW reaching a compressive strength of almost
25MPa after 90 days of curing. According to SEM results, a good adhesion was originated for 0.5 and 1% of WSW and for all
WSW percentages used a positive effect on the post-cracking behavior was found.
© 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the scientific committee of the 3rd International Conference on Natural Fibers: Advanced
Materials for a Greener World.
Keywords: Sustainable materials, mortar, sawdust waste, wood by-products
1. Introduction
Wood products and furniture can generate sawdust waste which is usually accumulated generating environmental
problems. On the other hand, concrete is a widespread material used in the construction sector due to its capacity of
compressive strength and ability to shape up in several geometric configurations. The problem with concrete arises
in the manufacture of cement and its environmental burden associated to high production of carbon dioxide (CO2)
which is released to the atmosphere but also due to the diminishing of nonrenewable sources. Some authors reveal
that for the production of every 600 kg of cement, approximately 400 kg of CO 2 is released [1]. In addition, concrete
density is a major concern in terms of weight and transport of materials. This is the reason of the increasing building
* Corresponding author. Tel.: +57-4-3197900 ext 509
E-mail address: hhgil@elpoli.edu.co
1877-7058 © 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the scientific committee of the 3rd International Conference on Natural Fibers: Advanced Materials for a
Greener World.
1877-7058 © 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the scientific committee of the 3rd International Conference on Natural Fibers: Advanced
Materials for a Greener World
10.1016/j.proeng.2017.07.046
326
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construction with lightweight concrete which usually offer advantages such as economical reduction and more
environmental friendly composites.
Lightweight mortar using sawdust as reinforcement has become an important issue in recent years especially in
tropical countries where this type of waste is produced in large quantities. The use of cement, sawdust and sand for
making floor and wall panels has been fairly common in many parts of the world [2]. Torkaman et al. [3]
investigated the effects of partial replacement of Portland cement by wood fiber waste for producing lightweight
concrete blocks and they found that compressive strength of the concrete blocks decreased with increasing cement
replacement. The waste is produced typically by two forms: powder and chips obtained from sawmill. Sales et al. [4]
found that water treatment sludge and sawdust can be applied in concrete as a light weight coarse aggregate to obtain
mechanical properties suitable for non-structural applications.
Sawdust waste incineration fly ash (SWIFA) has been employed to produce cement pastes and concrete mortars
[5]. Some authors have used wood ash as replacement of cement in the production of concrete and mortar with good
results [6]. However, some authors have found that the use of these type of ashes present low improvements on
mechanical properties [5]. There is also evidence of successful addition of wood by-products in lightweight mortar
up to 5% [7]. Bederina et al. [8] and Belhadj et al. [9]investigated the effect of wood shavings in mortars and they
concluded that the material could be added to the cement matrix without any preliminary treatment. In general, the
use of lightweight aggregates in concrete (such as wood chips) can be advantageous, by allowing reduced size of
foundations and structural elements [7]. In this study an attempt was made to use wood sawdust wastes (WSW) for
producing lightweight mortars and to obtain estimation of composite mechanical properties at different curing
periods.
2. Experimental
2.1. Materials
WSW used in this investigation was of Colombian production and was categorized as WSW-coarse in terms of
the particle size [10]. WSW was collected during sawing and then it was sieving. Material retain on sieve # 4 (4.76
mm) were used for all mixtures. Ordinary Portland cement type I of specific gravity of 3.1 was used to produce
mortars. Quartz sand with size below 5 mm was also used in the composite.
2.2. Mortar preparation and testing of specimens
Water absorption test of approximately 1 g of WSW were performed by means of a RADWAG PMC 210/WH
moisture analyzer at 105ºC. Lightweight mortars with a water/cement/sand ratio of 0.4:1:1 were manufactured. The
content of WSW inside the mortars was of 0, 0.5, 1 and 3% by weight. The wood by-products were pre-soaked in
water before mixing to prevent it from soaking the water meant for cement hydration [11,12].
The cement paste was mixed with added sand in a mechanical mixer at 60 rpm for 2 min with 40% of the total
water required. Then, sawdust was gradually incorporated in the mixture and a further 40% of the water was slowly
added. After using all sawdust, the remaining water was added followed by 1 min rest. Cube samples of 2 in x 2 in x
2 in were casting in steel forms to perform mechanical tests and density estimation after 7, 30 and 90 days of curing.
Samples were stored during the first 24h in a curing box chamber at 100% of relative humidity (RH) and after that,
they were demoulded and placed in and environment at 22 ± 2ºC and 78 ± 3% RH.
Each cubic specimen was tested for ultrasonic pulse velocity (UPV) using a CONTROLS Model E48 ultrasonic
pulse velocity testing device. Compressive strength was evaluated according to ASTM C109 [13]. All experiments
were performed by triplicate samples in order to get statistical variations of the data. A scanning electron microscope
(SEM) model JSM6490-LV from JEOL Company was used to perform morphological observations on selected
samples. The accelerating voltage used was 20 kV.
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3. Results and discussion
3.1. Water absorption
Humidity content of WSW obtained from three independent samples was 8.72 ± 0.4%. This value is very close to
the one reported in the literature [14]. An important issue regarding this type of composite is the concern of using
wood by-products in a cement matrix because of its high moisture absorption. Moreover, the low compatibility
between the fibers and the cement is also taking into account [15]. In this study, the pre-soaked in water treatment of
the WSW was effective to produce workable cement mixtures.
3.2. Morphological results
Scanning electron micrographs of WSW before mortar preparation is shown in Fig 1. As can be seen, the wood
by-product presents fibrous morphology of irregular shape than can be suitable for a good cement adhesion. A fiberlike continuous layer is observed which is highly carbonaceous in nature with high carbon content [1]. An elemental
composition of WSW with rich quantities of carbon, oxygen and potassium was found by means of energy
dispersive X-ray (EDX) results.
Fig.1. SEM micrographs of sawdust before mortar preparation.
Scanning electron micrographs of mortar with different amount of sawdust content after 7 days of curing are
presented in Fig. 2. A good adhesion of sawdust was developed at the interface at least for 0.5 and 1% of
reinforcement. These results are in agreement with compressive tests (see below). From the micrographs, it can be
concluded that sawdust surface does not present evidence of significant damage and the material was well dispersed
in the composites.
a)
b)
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c)
Fig.2. SEM micrographs of mortar containing a) 0.5%, b) 1% and c) 3% by weight of sawdust after 7 days of curing.
3.3. Compressive strength of mortars
According to Filho et al. [16] an increase in the initial water curing period led to a considerable decrease in the
depth of carbonation. Reduction of matrix alkalinity can be used as advantage to increase natural fiber durability
within a cement matrix [17,18]. In this paper, it was chosen only a 24h initial water curing and then samples were
allowed to cure at room temperature. The results from the compressive tests are shown in Fig. 3. Blank samples
show larger compressive strength in all cases. After 7 days of curing, there is not a statistical difference for sawdust
contents between 0.5 and 1%. However, when the curing time increases, mortars with 0.5% of sawdust performed
better and after 30 and 90 days of curing time the results are very close to the one without sawdust. Average values
of 41 and 39.74 MPa were found for 0 and 0.5% of WSW respectively. The morphology of the WSW discussed
before together with examination after mortar failure gives the idea that WSW helps in the post-cracking behavior by
assuring a certain bridge effect of wood fibers. This creates a positive effect in terms of deformation capacity of
mortars. The effect has been seen before in the literature [7].
Fig.3. Compressive strengths as a function of sawdust content for 7, 30 and 90 days of curing
Using higher contents of sawdust seems to worsen compressive strength which exhibits the lowest resistance after
90 days of curing compared to the other proportions. A SEM micrograph of a mortar after 30 days for 3% of WSW
is shown in Fig 4. As can be seen in the figure, a poor adhesion is present at the interface due probably to increasing
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magnitudes of water absorption in the fibers which causes low efficient hydration reaction on the cement matrix.
Indeed, mortar resistance with 3% of WSW is below of 25 MPa but it is composite that can be used as lightweight
mortar. The lower sand to cement ratio (1:1) allowed reaching compressive strength values above 24, 32 and 39 MPa
for 3, 1 and 0.5% WSW respectively.
Fig.4. SEM micrograph of mortar containing 3% by weight of sawdust after 30 days of curing.
3.4. Density of mortars
The values of mortar density after 90 days of curing times are exhibited in Fig 5. In all cases except for 3% of
WSW, density values are very close to each other and also there are no statistical differences. According to
Corinaldesi et al.[7] the maximum limit for a mortar to be considered lightweight is 1.8 g/cm3 and the results shows
that the only mixture conditions that could be classified as lightweight is the one with 3% of WSW. Average density
value for this composite is 1.75 g /cm3. These results are in agreement with investigations using wood waste in
mortar showing lightweight mortar for at least 5% of dosage wood by-products [7] or with wood shaving used by
replacing sand in mortars [8].
Fig.5. Mortar density as a function of sawdust content
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3.5. Dynamic modulus of elasticity
UPV technique is an indirect method for quantifying homogeneity in cement-based materials. An emitter sends
an ultrasonic pulse through the tested material to a receptor, and the distance between the emitter and receiver
divided by elapsed wave travel time [19]. The dynamic elastic modulus of the mortars were calculated using Eq. (1)
[20,21]:
Edem  c 2
1   (1  2 )
1  x109
(1)
Where, Edem=dynamic elastic module of mortar (GPa), ρ=hardened mortar density (kg/m3), c=UPV (m/s) and
ν=Poisson’s ratio. Poisson’s ratio was assumed as 0.22 for all mortar mixtures. Reported values of this parameter in
the literature are within the range of 0.22 to 0.24 [22,23].
Dynamic elastic moduli estimations against compressive strength for mortar after 90 days of curing are shown in
Fig. 6. A linear relation was found but with low correlation coefficient (R=0.86). When the amount of WSW
increases, the value of the dynamic elastic moduli decreases, as is observed to the left in Fig. 6. However, there is no
difference between mortars with 0.5 and 1% of WSW. Mortar with 0% of WSW exhibited larger modulus of an
average 22.7 GPa and mortar with 3% of WSW exhibited the lowest modulus (16.6 GPa). The results are in
agreement with compressive strength obtained from independent measurements.
Fig.6. Dynamic elastic modulus versus compressive strength for mortar after 90 days of curing
Table 1 summarizes average pulse velocity, dynamic elastic modulus and density values for all mixture
conditions. After 7 days of curing, average modulus increased within the range of 2-10% with 0.5% of WSW but
with 3% of sawdust the modulus decreases in 23%. For longer periods, the modulus was always reduced in the range
of 4-27%. As is inferred in the data, reinforced levels of sawdust of 3% become a significant factor not only for the
density but in the dynamic elastic modulus. This indicating that mortars less stiff could be manufactured by adding
WSW to the mixture as was reported before [7].
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Table 1. Pulse velocity, dynamic elastic modulus and density values for mortar modified with WSW at different curing times
Curing time
WSW content
Pulse velocity
Dynamic elastic modulus
Density
(days)
(%)
(m/s)
(GPa)
(kg/m3)
7
0
3241.80
18.65
2.01
0.5
3412.24
20.63
2.02
1
3261.74
19.01
2.04
3
3059.99
14.31
1.75
0
3561.11
21.86
1.98
0.5
3466.92
20.46
1.95
1
3346.57
19.60
2.02
3
2922.23
11.94
1.59
0
3581.08
22.66
2.02
0.5
3397.20
20.16
1.99
1
3424.13
21.04
2.04
3
3287.59
16.57
1.75
30
90
This study shows the differences on the mechanical properties of mortar reinforced with different amounts of
sawdust waste. Further tests should be performed in order to analyze sawdust durability within cement matrix.
4.
Conclusions
In this experimental study, mortars modified with wood by-product waste were produced and mechanical
properties were followed for several curing times. Mortars containing 0.5 and 1% of wood waste performed better
than those prepared with 3%. In fact, the higher reinforced percentage used seems to worsen compressive and elastic
modulus of mortar although exhibits the lowest density. The low sand to cement ratio (1:1) was useful to reach good
compressive strengths values of above 24, 32 and 39 MPa for 3, 1 and 0.5% WSW respectively. SEM results are in
agreement with mechanical tests showing that 3% of WSW evidence poor adhesion at the interface. It should be
emphasized that WSW has a positive effect on the post-cracking behavior which leads to the improvement of the
ductility of mortars.
Acknowledgements
The authors are grateful to Politécnico Colombiano Jaime Isaza Cadavid for financial assistance (Proyectos de
investigación sede central Politécnico Colombiano Jaime Isaza Cadavid 2016).
References
[1] C.B. Cheah, M. Ramli, The implementation of wood waste ash as a partial cement replacement material in the production of structural grade
concrete and mortar: An overview, Resour. Conserv. Recycl. 55 (2011) 669–685.
[2] A.A. Awal, A. Mariyana, M. Hossain, Some aspects of physical and mechanical properties of sawdust concrete, Int. J. 10 (2016) 1918–1923.
[3] J. Torkaman, A. Ashori, A. Sadr Momtazi, Using wood fiber waste, rice husk ash, and limestone powder waste as cement replacement
materials for lightweight concrete blocks, Constr. Build. Mater. 50 (2014) 432–436.
[4] A. Sales, F.R. de Souza, F. do C.R. Almeida, Mechanical properties of concrete produced with a composite of water treatment sludge and
sawdust, Constr. Build. Mater. 25 (2011) 2793–2798.
[5] A.U. Elinwa, Y.A. Mahmood, Ash from timber waste as cement replacement material, Cem. Concr. Compos. 24 (2002) 219–222.
[6] C.B. Cheah, M. Ramli, The implementation of wood waste ash as a partial cement replacement material in the production of structural grade
concrete and mortar: An overview, Resour. Conserv. Recycl. 55 (2011) 669–685.
332
Haveth Gil et al. / Procedia Engineering 200 (2017) 325–332
Author name / Procedia Engineering 00 (2017) 000–000
8
[7] V. Corinaldesi, A. Mazzoli, R. Siddique, Characterization of lightweight mortars containing wood processing by-products waste, Constr.
Build. Mater. 123 (2016) 281–289.
[8] M. Bederina, B. Laidoudi, A. Goullieux, M.M. Khenfer, A. Bali, M. Quéneudec, Effect of the treatment of wood shavings on the physicomechanical characteristics of wood sand concretes, Constr. Build. Mater. 23 (2009) 1311–1315.
[9] B. Belhadj, M. Bederina, N. Montrelay, J. Houessou, M. Quéneudec, Effect of substitution of wood shavings by barley straws on the physicomechanical properties of lightweight sand concrete, Constr. Build. Mater. 66 (2014) 247–258.
[10] P. Turgut, Cement composites with limestone dust and different grades of wood sawdust, Build. Environ. 42 (2007) 3801–3807.
[11] B.S. Mohammed, M. Abdullahi, C.K. Hoong, Statistical models for concrete containing wood chipping as partial replacement to fine
aggregate, Constr. Build. Mater. 55 (2014) 13–19.
[12] C. Aciu, R. TAMAS-GAVREA, C. Munteanu, Manufacture of Ecological Mortars by Cork and Sawdust Waste Recycling., Bull. Univ.
Agric. Sci. Vet. Med. Cluj-Napoca Hortic. 70 (2013).
[13] C. ASTM, 109 Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (using 2-in. or [50-mm] Cube Specimens),
Phila. PA Am. Soc. Test. Mater. 318 (1999).
[14] M. Mageswari, B. Vidivelli, The use of sawdust ash as fine aggregate replacement in concrete, J. Environ. Res. Dev. 3 (2009).
[15] A.O. Olorunnisola, Effects of husk particle size and calcium chloride on strength and sorption properties of coconut husk–cement
composites, Ind. Crops Prod. 29 (2009) 495–501.
[16] R.D. Tolêdo Filho, K. Ghavami, G.L. England, K. Scrivener, Development of vegetable fibre–mortar composites of improved durability,
Cem. Concr. Compos. 25 (2003) 185–196.
[17] M.F. Canovas, N.H. Selva, G.M. Kawiche, New economical solutions for improvement of durability of Portland cement mortars reinforced
with sisal fibres, Mater. Struct. 25 (1992) 417–422.
[18] Z. Berhane, Performance of natural fibre reinforced mortar roofing tiles, Mater. Struct. 27 (1994) 347–352.
[19] M.R.M. Durán, A.A.T. Acosta, M.G.A. Contreras, M.R. Belmonte, Characterization of Mortar with Mineral Additives, MRS Online Proc.
Libr. Arch. 1612 (2013).
[20] A. Mardani-Aghabaglou, M. Tuyan, K. Ramyar, Mechanical and durability performance of concrete incorporating fine recycled concrete
and glass aggregates, Mater. Struct. 48 (2015) 2629–2640.
[21] R.E. Philleo, Comparison of Results of Three Methods for Determining Young’s Modulus of Elasticity of Concrete, J. Proc. 51 (1955) 461–
470.
[22] J. Dugat, N. Roux, G. Bernier, Mechanical properties of reactive powder concretes, Mater. Struct. 29 (1996) 233–240.
[23] Z. Lafhaj, M. Goueygou, A. Djerbi, M. Kaczmarek, Correlation between porosity, permeability and ultrasonic parameters of mortar with
variable water / cement ratio and water content, Cem. Concr. Res. 36 (2006) 625–633.