Ping 2021

Journal of Building Engineering 43 (2021) 102869
Contents lists available at ScienceDirect
Journal of Building Engineering

journal homepage: www.elsevier.com/locate/jobe
Chemical investigation and process optimization of glycerine pitch in the

green production of roofing tiles
Wei Ping Teoh a, Swee Yong Chee b, Noor Zainab Habib c, Mohammed J.K. Bashir a,
Vui Soon Chok d, Choon Aun Ng a, *
a
Faculty of Engineering and Green Technology, Universiti Tunku Abdul Rahman, Malaysia
b
Faculty of Science, Universiti Tunku Abdul Rahman, Malaysia
c
Institute of Infrastructure and Environment, Heriot-Watt University, Dubai Campus, United Arab Emirates
d
KL-Kepong Oleomas Sdn Bhd, Malaysia
A R T I C L E I N F O A B S T R A C T
Keywords: High embodied carbon of concrete and waste generation from the oleochemical industry pave an alternative way
Glycerine pitch for the sustainable utilization of glycerine pitch (GP) and used cooking oil (UCO) in the production of roofing
Used cooking oil tiles. In this study, a mixture of UCO and GP, known as blended organic binder (BOB) was utilized to produce
Roofing tiles
Eco-Roofing tiles, namely BOB-RT. To prepare the specimen, the BOB with percentages varied from 5 to 11% was
Green production
blended with a mixture of fly ash and fine sand. The weight ratio of fly ash and fine sand is 35: 65. The mixture
was then moulded and heat cured at 190 ◦ C for 24 h. The chemical and mechanical properties of the cured
specimens were investigated through Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy
(ATR-FTIR), transverse breaking strength, water absorption, permeability, and porosity tests. A preliminary
investigation on the effect of BOB at different mixing ratios was assessed. The highest flexural strength of 12.605
MPa was achieved by a specimen when 10% of BOB (GP: UCO 30:70) was utilized. However, the hygroscopic
effect of GP and fly ash led to the high water absorbability (10.81–20.13%) of the specimen. This issue can be
addressed by the addition of dodecanedioic acid or by applying a UCO-based protective layer. The results
revealed that the water absorbability of the specimen was significantly reduced by 56.8%. In addition, the
feasibility of GP as a sole binder in the production of roofing tile (known as GP-RT) was investigated too. The
optimized GP-RT produced from 12% of GP possessed a maximum flexural strength of 6.32 MPa with 4.46% of
water absorption, which can be qualified as a proper roofing tile according to ASTM standards. From the
environmental perspective, the embodied carbon and embodied energy of the Eco-Roofing tiles are relatively
lower than the conventional roofing products.
1. Introduction waste materials, which composed of highly organic, biodegradable, and

hazardous components, have been generated from the oleochemical
The worldwide population has rapidly grown from 1.65 billion to 6 industry [3]. Glycerine pitch is one of the by-products generated during
billion by the 20th century, and reported reaching 9.0 billion by 2037 the production of refined glycerine [4]. Normally, glycerine pitch is
[1]. These expansions have visibly created environmental and waste generated through vacuum distillation of the crude glycerine (feedstock)
management challenges in all aspects. Along with the improvement of to produce refined glycerine (products). In the distillation process, the
the living standard, the demand for oleochemicals is expected to in undistilled materials will accumulate at the bottom of the vacuum
crease significantly. The refined glycerine, or commonly known as distillation column as residues, which is known as glycerine pitch. The
glycerol, is one of the oleochemical products with widespread applica residues are composed of a significant amount of dust and contaminants,
tions in end-use industries, such as medical and pharmaceuticals, food which limit its usage in other applications [5]. The conventional ways to
and beverage, personal care, tobacco, and so on [2]. Attributed to the recover the useful components, such as glycerol and fatty acids from the
enormous demand for glycerol, significant quantities of effluent and glycerine pitch are infeasible due to the cost constraint. This has urged
* Corresponding author.
E-mail address: ngca@utar.edu.my (C.A. Ng).
https://doi.org/10.1016/j.jobe.2021.102869
Received 7 January 2021; Received in revised form 4 June 2021; Accepted 9 June 2021
Available online 11 June 2021
2352-7102/© 2021 Elsevier Ltd. All rights reserved.
W.P. Teoh et al. Journal of Building Engineering 43 (2021) 102869
the researchers to look for alternative ways to convert the glycerol waste usage of natural resources by beneficially utilizing these wastes. Hence,
into valuable products at a lower cost. the construction sector should attempt to implement sustainable
Glycerine pitch generated from the oleochemical industry created a development and products, such as the incorporation of environmen
disposal issue due to its high alkalinity and organic contents [6]. tally friendly waste materials, to potentially decrease the carbon emis
Without proper treatment before being disposed of, the pitch may sion during the manufacturing process [24]. Consequently, the recycling
contribute to environmental damage through contamination of natural of waste and implementing it in building materials will yield significant
resources, soil, water stream, and groundwater. In Malaysia, the current benefits to the construction industry in the economic, technical, and
solution for the disposal of glycerine pitch is through the incineration environmental aspects.
process or by sealing it in drums prior to landfill [7]. As glycerine pitch In the previous studies, experimental works have shown that used
possesses a relatively significant calorific value, it was suggested by cooking oil, waste engine oil, and blended waste oil can be used as an
some organizations to incinerate it for power generation and boiler alternative binder for the production of roofing tiles [25–27]. Different
operation [8,9]. However, as evidenced by national data compiled by from the cementitious binder, the binding mechanism of the waste oils is
the U.S. Environmental Protection Agency (EPA) in their eGRID data expected being an encapsulation process [28]. When the waste oil po
base, the incineration process is incredibly bad for the climate, as it lymerizes under elevated temperature, the polymerized components will
releases 2.5 times as much carbon dioxide to generate a similar amount continuously coat around the aggregate and filler incorporated in the
of electricity as a coal power plant [10]. Besides, incineration of glyc system, and hence, they bonded together and formed a proper binding
erine pitch may also emit a highly hazardous and lethal gas called matrix. The utilization of waste oils in the production of building ma
acrolein to the atmosphere [11,12]. Without effective controls, the terials is able to fully replace clay and cement, which are considered as
harmful pollutants may be emitted into the air, which may affect human not environmentally friendly as they possessed high embodied carbon
health and pollute the environment. and energy [29]. In addition, the industrial waste, such as pulverized fly
Improper disposal of glycerine pitch certainly will lead to air, soil, ash and bottom ash has been used in conjunction with the waste oils,
and groundwater contaminations. Proper treatment of glycerine pitch which is possible to significantly decrease the usage of traditional ag
requires significant cost for its processing, transportation, and working gregates, thus promoting a product fully produced from waste materials.
area. Hence, the trend of research now is shifting towards the investi The production of a fully waste-made unit offers a way for the treatment
gation of the alternative usage of glycerine pitch in the industry. It of wastes, enhance their values, and conserve natural resources.
would be advantageous if its valuable components, such as free glycerol, Generally, the roofing tiles produced from these waste materials
fatty acids or glycerides can be recovered for valuable usage. For possessed convincing properties which can fulfil the requirements of
instance, the recovery of glycerol and diglycerol through the purifica roofing tiles in terms of breaking strength, percentage of water ab
tion process give a positive impact on both the economic and environ sorption, and permeable characteristic according to the ASTM stan
mental perspectives [11]. Due to its moisturizing properties, purified dards. Other than that, an innovative approach was attempted by
glycerol can be used in the production of eco-friendly soap, which gives utilizing pure glycerol and vegetable oil, coupled with secondary ag
reasonable purity after treated with dilute sulfuric acid and activated gregates for the full replacement of cement in the production of masonry
carbon [13]. Besides, by coupling with Lactobacillus inoculant, glycerine units [30]. It was discovered that glycerol would enhance the homo
pitch can act as a medium of the fermentation process to produce liquid geneous distribution of cooking oil in the concrete matrix and hence
biofertilizer. In this case, glycerine pitch serves as a carbon source for reduce the required vegetable oil content in the manufacturing process.
stimulating the growth of Lactobacillus [2]. Moreover, it is also exploited Interestingly, glycerine pitch contains free fatty acids and a significant
as a carbon source for the production of poly (3-hydroxybutyr amount of glycerol content [11]. Hence, in this study, it was hypothe
ate-co-4-hydroxybutyrate) copolymer by a novel, yellow-pigmented sized that the use of glycerine pitch, which aims for a full replacement of
bacterium Cupriavidus sp. [14], as well as an activated absorbent for conventional binding materials, is possible.
methylene blue removal after being distillated via zinc chloride activa This study utilizes glycerine pitch and used cooking oil as a blended
tion [15]. These attempts subsequently improved the economic values of organic binder (BOB), coupled with fine sand as aggregate, and fly ash as
glycerine pitch, whilst established a feasible waste management filler to produce a roofing material with mechanical performance that
approach for it. However, potential health problems of GP are another can fulfil the requirements of corresponding ASTM standards. In the
issue of concerned when it is utilized for soap making [16]. The possi second attempt, glycerine pitch was used as the sole binder, while used
bility of contamination when it is used as biofertilizer should also be cooking oil was utilized as the coating materials in order to enhance the
taken into consideration. water resistivity of the roofing tiles produced. Several parameters were
Attributed to the overwhelming demand for housing and infra taken into consideration to suit the waste materials used in the
structure in both the developing and developed countries, there has been manufacturing process, which include the binder content, curing tem
tremendous growth in the construction sector towards the demand of perature, and curing duration. The absorption properties of aggregate
cement [17]. Solely in Malaysia, approximately 43.48 million concrete and filler used in the manufacturing process of roofing tiles play an
roof tiles were produced in 2019, which contributed around 85% of the important role to determine the required compositions of waste binders
total roofing materials produced [18,19]. Besides causing the increased [30]. Utilization of sand aggregate and fly ash which is considered inert
consumption of natural resources, the cement sector generates carbon in terms of the physical and chemical properties tend to significantly
dioxide through raw materials pulverization, clinker grinding, carbon decrease the binder content. High compacting pressure applied during
ate decomposition, and fossil fuel combustion [20]. On a global basis, it the moulding of the roofing materials can enhance the compactness of
was reported that approximately 65 Megaton of carbon dioxide was the raw materials, minimize the pore size of the samples, hence further
generated from the construction sector annually, which is released decrease the binder content required for the proper binding of the
during the manufacturing process of around 70 Megaton of cementitious samples. In addition, the production of cement clinkers normally re
building materials [21]. The carbon dioxide released from the con quires a temperature up to 1450 ◦ C [31], while the production of clay
struction sector is equivalent to 94% of the global carbon dioxide bricks under the firing process needs to be carried out at a temperature
emitted, making it the greatest contributor towards greenhouse gases as high as 1100 ◦ C [32]. This resulted in high embodied carbon and
emission [22]. Besides, the rapid growth in populations and industrial embodied energy of the building materials produced from clay and
ization in these countries have generated an enormous amount of waste cement. Therefore, a curing temperature below 200 ◦ C as applied in this
materials, which may be harmful to human health as well as to the study to produce roofing tiles will significantly reduce the carbon di
environment [23]. With the increasing housing demand and the quan oxide emissions and energy consumption of the manufacturing process.
tities of waste generated, there has been a concerted effort to reduce the This is in line with the previous study, in which the embodied carbon
2
and embodied energy of the Vege-Roofing tiles produced at the curing fatty acids and inorganic salts [11]. However, the composition might
temperature of 190 ◦ C are 267% and 321% lower than that of conven vary depending on the feedstock and process used to generate the
tional concrete tiles, respectively [25]. glycerine pitch. The recovery technique proposed by Ref. [11] was used
Four major objectives are enumerated to be achieved at the end of to determine the compositions of glycerine pitch. It was believed that
this study, which includes: glycerol and free fatty acids are the main contributor to the strength
development of the Eco-Roofing tile, while glycerol can also enhance the
i. To investigate the possibility of using glycerine pitch as binder, homogeneity of the binder’s distribution in the binding matrix [28]. The
coupled with fine sand and fly ash in the production of roofing moisture content, ash content, volatile matter and calorific value of
tile. glycerine pitch were investigated using ASTM and BS:EN standards as
ii. To identify the chemical properties of glycerine pitch contrib shown in Table 2.
uting to the hardening of roofing tiles.
iii. To optimize the proportion of raw materials and the 2.2.2. Pulverized fly ash (PFA)
manufacturing conditions for the production of the novel roofing The fly ash utilized in this study was collected from TNB Jana
tile. manjung Sdn. Bhd, which is in Sitiawan, Perak, Malaysia. The PFA
iv. To calculate the total embodied carbon and embodied energy of collected was dried and sieved to eliminate any incompletely burned
environmentally friendly roofing tiles as compared to commer components prior to the manufacturing process. The average sizes of the
cialized cementitious and clay-made products. fly ash were determine using a particle size analyser (Malvern, Master
sizer 2000), were found to be 115.014 μm and 6.333 μm, in terms of
The physical properties, which include transverse breaking strength, volume and mass moment mean, respectively. The chemical composi
water resistivity, and permeation characteristics of the innovated tion of PFA was analysed using Energy-dispersive X-ray spectroscopy
roofing tiles produced were also investigated for its suitability in con (EDX) and the details are shown in Table 3:
struction application.
2.2.3. Fine sand
2. Materials and methodology The fine sand utilized in the production of specimens was collected,
dried, and separated accordingly to the following particle sizes: 4.0 mm,
2.1. Development of Eco-Roofing tiles 1.0 mm, 0.5 mm and <0.5 mm (ASTM C 136/136M − 14). Table 4 shows
the weight percentage of sand particles with different sizes.
Glycerine pitch, used cooking oil, fine sand, fly ash and dodeca
nedioic acid (DDDA) were utilized as the raw materials in the production 2.2.4. Used cooking oil (UCO)
of two types of Eco-Roofing tiles, namely blended organic binder-made Used cooking oil utilized in the coating process of roofing tiles was
roofing tiles (BOB-RT) and glycerine pitch-made roofing tiles (GP-RT) collected from the household. It is generated from a continuously
respectively. Table 1 shows the summary of the roles and characteristics heating process under high temperature in the presence of air and
of the raw materials involved in the manufacturing process. moisture, which consequently leads to the degradation of the cooking
oil. The viscosity and molecular structure of used cooking oil might vary
2.2. Materials depending on the extent of degradation in different cooking conditions.
Hence, the collected UCO was blended and filtered to ensure homoge
2.2.1. Glycerine pitch (GP) neity. The specific gravity and viscosity of UCO, which were measured
Glycerine pitch (GP) used in this project was collected from KL- using a hydrometer and a digital rotary viscometer, were 0.92 and
Kepong Oleochemical Sdn. Bhd. located in Pulau Indah, Selangor, 168.6 cP, respectively.
Malaysia. It is highly alkaline (pH > 10), pasty (viscosity = 1221.6 cP)
and dark brown in colour. Glycerine pitch is water soluble with an
ambient density of 1.0–1.1 kg/L. In addition, the flashpoint and auto- 2.3. Manufacturing process of eco-roofing tiles
ignition temperature of the glycerine pitch are >200 ◦ C and >250 ◦ C
respectively. Hence, the curing temperature below 200 ◦ C is considered The manufacturing process of Eco-Roofing tiles required three steps,
appropriate for the production of Eco-Roofing tiles. Theoretically, which are (i) the mixing of raw materials, (ii) moulding via Marshall
glycerine pitch possesses a significant amount of crude glycerol, free compaction and (iii) heat curing process, as shown in Fig. 1. In the
mixing process, the proportion of the raw materials were measured by
their dry mass. The mixing ratio of fine sand to fly ash is fixed at 65:35
Table 1
The roles and characteristics of raw materials used in the production of Eco-
throughout the study, and their total weight is acted as a base weight for
Roofing tile. other materials. The percentage of GP, UCO and additive are calculated
according to the base weight. Table 5 shows the mix design of the Eco-
Role Physical Chemical
Roofing tiles produced in this study.
Glycerine Binder Dark brown, pasty Consists of glycerol, fatty
pitch component acids, inorganic salt, and
Viscosity: 1221.6 cP other additives. Table 2
Specific gravity: 1.43 Comparison of the parameters of glycerine pitch with those obtained from
Water soluble another source.
Used Binder Yellowish, oily solution Possesses vast range of
Parameter Literature Review Current Test Method
cooking Viscosity: 168.6 cP free fatty acids.
[11] Study
oil Specific gravity: 0.92
Fine sand Aggregate Composed of grains with Neutral in nature Crude glycerol (%) 70–80 ~70 [11]
size lower than 4.0 mm Free fatty acids (%) <10 ~4
Fly ash Filler Dark brown powder Possesses various oxides Inorganic salts (%) <10 ~5
Specific gravity: 0.26 components. Moisture (%) – 3.39 BS:EN
Average particle size: The composition of SiO2, 12880:2000
115.014 μm (volume) Al2O3 and Fe2O3 is more Ash content (%) – 17.67 BS:EN
and 6.333 μm (number) than 70%. Volatile matter (%) – 78.94 12879:2000
DDDA Additive White pallet C12H22O4 Calorific value (kcal/ – 4017 ASTM D 240–14
Dissolve in the binder Dicarboxylic acid kg)
3
Table 3 and GP at different mixing ratios) were investigated. Those binders are
Chemical composition of PFA utilized in this study. named as binder A, binder B and binder C, with the UCO:GP ratio of
Oxide Components Percentage Constitution ASTM 618-12a 70:30, 50:50 and 30:70 respectively. The samples were heat cured at
(%) 190 ◦ C for 24 h to ensure the preliminary chemical interactions between
Silicon dioxide (SiO2) 58.73 SiO2 + Al2O3 + Fe2O3 ≥ UCO and GP. The differences among the binders are observed and
Aluminium Oxide 27.64 70% recorded.
(Al2O3)
Ferrous Oxide (Fe2O3) 5.06 2.5. Mechanical analysis of Eco-Roofing tiles
Calcium Oxide (CaO) 3.44 –
Magnesium Oxide 2.12 –
(MgO) 2.5.1. Transverse strength & flexural strength
Sodium Oxide (Na2O) 1.26 – The transverse strength of the samples was determined in accordance
Sulfur Oxide (SO3) 0.89 ≤5.0% with ASTM C 1492–03. The tests were performed by using a Material
Loss of Ignition (LOI) 1.68 ≤6.0%
Testing Machine T-Machine, and the data obtained were analysed using
a software program, namely Universal Testing Manager. In this process,
the samples were tested in a three-point bending mode with a horizontal
Table 4 plane, whereby there are two lower support members supporting the
Size distribution of the sand aggregate utilized in this study. lower base of the tile. The load was applied perpendicularly to the plane
Size Distribution of Sand Aggregate Percentage (%) of the tile with the third member located at the mid-span of the tile. The
>4.0 mm 6.3
results obtained are expressed in the unit of Newton (N). Once the yield
>1.0–4.0 mm 7.3 strength (dry or wet transverse strength) was obtained from the material
>0.5–1.0 mm 5.5 testing machine, the flexural strengths, σ, in terms of MPa can be
<0.5 mm 80.9 calculated from Equation (1) for the three-point bending mode, in
accordance with ASTM C 293–08. The minimum dry and wet transverse
After being thoroughly mixed, the raw mixture was measured and strengths to be achieved are 1779 N and 1334 N respectively.
divided into 300 g per bulk sample mass. The mass of each portion was /( )
Flexural Strength (MPa) = 3PL 2wd2 (1)
fixed at 300 g to maintain the consistency throughout the study. The raw
mixture was transferred into a mould and compacted by using an where.
Automatic Marshall Compactor. The compactor lifts the 4.535 ± 0.015
kg load and automatically releases it at the specified height of 457 ± 5 P = maximum force applied, N
mm. Each specimen was compacted for 20 bowls. After the moulding L = span length, mm
process, the sample was off-moulded, and heat cured in a ventilated w = width of the sample, mm
oven. The uncured, compacted specimens possessed low strength and d = diameter of the sample, mm
required extra care when handling it. As this study mainly focuses on the
feasibility of waste materials as the alternative binder, the curing tem 2.5.2. Percentage of water absorption
perature and curing duration were fixed at 190 ◦ C and 24 h, as proposed The testing procedure and calculation of water absorption were in
in the previous study [33]. After the curing process, the specimens accordance with ASTM C 67–07a. The dried samples were submerged
became rigid and possessed a smooth surface, sharp angle, with signif into clean water for 24 h at a temperature between 15.5 and 30.0 ̊ C.
icant strength. After 24 h of immersion, the samples were taken out and the surface of
Certain roofing tile samples were coated with used cooking oil (UCO) the samples were wiped dry. The final wet weight of each sample was
using either a spraying or an immersion method. The spraying method measured within 5 min after the sample has been removed from water.
utilized a spray gun to distribute the UCO evenly on the surface of The percentage of water absorption is calculated according to Equation
samples, while the immersion method involved immersion of the sample (2). According to the standard, the maximum percentage of water that
into a tank full of UCO. In the coating process, UCO was found not only can be absorbed by a specimen is 6%.
forming a layer on the surface of specimens but also penetrates into the
specimens. The hydrophobicity of UCO would significantly enhance the Water Absorption (%) = [(Ww − Wd ) / wd ] × 100% (2)
lotus effects of the sample’s surface and reduce the rate of penetration of
where.
water molecules into the body of samples [33]. Prior to the coating
process, the samples were pre-cured at 190 ◦ C for 4 h to rigidify their
Ww = wet weight of the specimen after 24 h of submersion, g
outer layer. The second layer was coated on the tiles after it was heat
Wd = dry weight of the specimen before submersion, g
cured for another 2 h, and the third layer was applied after another 2 h.
The specimens were heat cured continuously after each coating process
2.5.3. Porosity
until the total curing duration reached 24 h. After that, the specimens
The testing procedure and calculation of porosity were in accordance
were tested for their transverse strength and water absorption tests.
with BS:EN 1881–122. The oven-dried weight, buoyance balance and
saturated surface dry weight of the roofing tile specimens were
2.4. Chemical analysis by Attenuated Total Reflectance Fourier measured accordingly. The porosity of the specimen is calculated ac
Transform Infrared Spectroscopy (ATR-FTIR) cording to Equation (3):
Porosity = [(Ws − Wd ) / (Ws − Wb )] × 100 (3)
ATR-FTIR spectroscopy (PerkinElmer Spectrum Two with a Univer
sal ATR accessory unit) is performed at room temperature, with the where.
detection range of 4000–400 cm− 1. It is used to investigate the func
tional groups of the blended organic binder. The ATR sampling device Ws = saturated weight of specimen, g
provides a fair analytical environment, which allows the comparison of Wd = dry weight of specimen after oven dried, g
the number of functional groups present in different samples by refer Wb = buoyance balance of specimen, g
ring to the intensity of the absorption peaks.
In this study, three types of blended organic binders (mixture of UCO
4
Fig. 1. Manufacturing process of an innovated roofing tile.
2.5.4. Water permeability 3. Results and discussion

The water permeability test was modified and conducted in accor
dance with ASTM 1167–11. The experiment was set up as shown in 3.1. Attenuated Total Reflectance Fourier Transform Infrared
Fig. 2. A PVC tube was sealed on the upper surface of the test specimen Spectroscopy
with a watertight sealant. Clean water was added into the tube up to a
depth of 51 ± 6 mm measured from the highest point of the upper The chemical compositions of blended organic binder (BOB) were
surface of the specimen. It is observed for a period of 24 h to check if analysed for a better understanding of the relationship between the
there is any water penetrating through the specimen. If there is no functional groups of the binders and the mechanical properties of the
penetration of water through the specimen, the roofing tile is deemed as specimens produced. Fig. 3 shows the comparison spectra of Binder A,
being impermeable. Binder B, and Binder C, which are represented by the red, blue and
purple spectrum respectively. Generally, these spectra possess similar
absorption peaks, while the intensities of the absorption peaks varied
depending on the composition of glycerine pitch (GP) and used cooking
5
Table 5
The mix design of the Eco-Roofing tiles.
Eco-Roofing Types of binder Percentage of Percentage of fine sand and fly ash Coating process
Tiles binder
BOB-RT Blended organic binder: A mixture of GP and 5–12% Coated with 1, 2 and
Mixture of fly ash and fine sand at weight ratio of 35:65. The total
UCO at mixing ratio of 30:70, 50:50 and 70:30. 3 layers of UCO.
weight of fine sand and fly ash served as base weight of another
GP-RT Glycerine pitch 9–12% Coated with a single
ingredient.
layer of UCO.
group is not involved in the expected chemical reactions. The presence

of high composition of hydroxyl groups would lead to higher water
absorbability of the sample, as the hydroxyl groups form hydrogen
bonding with water molecules when exposed to moisture, resulting in a
hygroscopic effect [37]. In addition, a smaller peak of COO– was
observed at around 1647 cm− 1, which is caused by the functionalities of
soap content that exist in the glycerine pitch [38]. Other representative
peaks of glycerine pitch are C–O stretching vibration located at around
1464 cm− 1 and 1112 cm− 1, which are contributed by the primary and
secondary alcohol components present. The absorption peak of C–O–H
bending vibration also exists at 1038 cm− 1. From the combined spectra,
it can be observed that those absorption peaks mentioned above show
greater intensity in Binder C, as they are mostly contributed by the
glycerol or other components that existed in the glycerine pitch [38].
Binder B is composed of 50% of UCO and 50% of GP. In the spectrum,
the absorption peaks of Binder B were found located in similar regions as
Binder A and Binder C. However, the peak intensity of Binder B is at the
medium level. Hence it is not further discussed in this section.
3.2. Optimization of types of blended organic binder and the percentage of

incorporation
This section discusses the strength achieved by the specimens pro

duced by using the blended organic binder, which is a mixture of glyc
erine pitch (GP) and used cooking oil (UCO). Fig. 4 shows the average
flexural strength of triplicate specimens produced from blended organic
binders at three different ratios, hereafter referred to as Binder A (GP:
Fig. 2. Demonstration of water permeability test.
UCO 30:70), Binder B (GP:UCO 50:50) and Binder C (GP:UCO 70:30).
When Binder A was used in the manufacturing of roofing tiles, the
oil (UCO) in the binder. flexural strength of the tile samples increased when the percentage of
Among the spectra, Binder A showed the greatest peak intensity at binder increased from 5 to 11%. The maximum flexural strength ach
2922, 2853, 1739, 1236, and 1160 cm− 1, which represent the specific ieved was 12.605 MPa, which is from the samples produced using 11%
functionalities of UCO components. Two strong and intense absorption of binder content. For Binder B and Binder C, the plateau of strength was
peaks at 2922 and 2853 cm− 1 correspond to the asymmetric and sym achieved with 10% of binder content, where the maximum flexural
metrical C–H stretching vibration, which are contributed by long carbon strength was 4.428 MPa for Binder B and 7.895 MPa for Binder C.
chains from triglycerides and free fatty acids. The absorption peak at The percentage of binder contents is important in developing the
1739 cm− 1 corresponds to the C– – O stretching vibration contributed by
strength of the roofing tiles produced. In addition, the surface tension of
carbonyl and ester compounds [34]. The peaks at 1241 and 1167 cm− 1 the binder is also important to keep the raw mixture in shape during the
correspond to the stretching vibration of –C–O bond attached to a curing process. Fig. 5 shows the SEM image of the uncured specimen
methylene (–CH2) or a methyl (–CH3) group, which are contributed by which is produced from fly ash and binder. It can be observed that all the
triglycerides and ester compounds [35,36]. These functional groups are ash particles were covered with a layer of liquid binder and formed
relatively important as they can serve as a preliminary indicator of the liquid bridges to connect the ash particles together [39], consequently,
sample strength produced by each binder. Based on the ATR-FTIR hold the raw mixture in shape. From the experimental experiences, too
spectra, Binder A possessed greater amount of carbonyl (C– – O) and
little of binder (<5%) would make the uncured samples crumble,
ester –C–O bonds than Binders B and C. This indicates that more whereas excessive amount of binder (>10 or 11%) results in the mixture
carbonyl and ester functional groups are available to participate in the being too soft and hence unable to maintain its shape during the curing
strength development of roofing tile via condensation polymerization process. The failure samples are shown in Figs. 6 and 7 respectively.
[33] as well as glycerolysis reactions. The chemical reactions involved in Hence, it is important to control the binder content at the optimum level
the strength development will be further discussed in section 3.4, which to develop maximum strength for the specimens.
is on the effect of each chemical reaction on the mechanical properties From the trends of these binders, it was discovered that the optimum
achieved by the samples. binder contents of Binders A, B, and C are 11, 10 and 10% respectively.
In the ATR-FTIR spectrum of Binder C which is composed of 70% of Beyond the peak percentage, the samples crumbled and led to the for
GP, a broad absorption peak located at 3357 cm− 1 represents the mation of pores within the specimens. The pores formed in normal and
hydroxyl-bonded stretching vibration (-OH) contributed by the glycerol failure samples are compared in Fig. 8 (a) and (b). Those pores greatly
presented in the glycerine pitch [15]. The hydroxyl groups would not affect the strength development of the specimens, resulting in a dramatic
contribute to the strength development of roofing tiles as this functional decrease in their strength [40]. For Binder A, the strength achieved has
6
Fig. 3. Combined ATR-FTIR spectra of Binder A, B and C.
Fig. 4. Flexural strength of the specimens produced from blended

organic binders.
Fig. 6. Sample produced with binder <5% crushed easily even handle
with care.
3.3. Mechanical properties of the optimized specimens
With respect to the results obtained from section 3.2, the optimized
specimens with optimum binder content, which are produced from 11%
of Binder A, 10% of Binder B, and 10% of Binder C were selected for
further development and testing. Table 6 shows the comparison of the
key properties of the optimized specimens, which include the dry and
wet transverse strength, water absorption, and permeable characteristic.
It was found that the dry transverse strength of the optimized specimens
is much higher than the minimum requirements of commercial concrete
Fig. 5. SEM image of uncured sample. roofing tiles (1779 N) in accordance with ASTM C 1492. Hence, they can
be categorized under high-profile roofing tiles in terms of their strength.
dropped by 50.2% after the peak percentage. Similar to Binders B and Table 6 also shows the water absorption results of the optimized
Binder C, the strength of the specimens has decreased by 11.7% and specimens. Generally, the percentage of water absorption of these
19.2% respectively. specimens was between 6.69 and 10.81%, which exceeds the limitation
of 6% according to ASTM C 1167–03. Among the ingredients used, fly
ash and glycerol are responsible for the high-water absorbability of the
specimens. The hygroscopicity of fly ash enhances the water holding
7
Fig. 7. Failure sample produced with binder >12% failed to maintain in shape, crumbled, and resulted in more pores on its surface.
Fig. 8. (a) Normal sample possess fewer and smaller pores; (b) failure sample possess more pores with larger size.
and Binder C specimens, which composed are of 50 and 70% of glycerine

Table 6
pitch respectively in their binder contents.
Mechanical properties achieved by specimens produced from different binder.
By thoroughly mixing the ingredients, it was expected that the
Properties Binder A Binder B Binder C Standard value blended organic binder would be well distributed among the grains of
Binder content (%) 11 10 10 – sand and ash particles, as well as filling the interior and exterior pores of
Flexural strength 12.605 4.428 7.895 NA the specimens. During the heat curing process, the glycerol (from GP)
(MPa) and free fatty acids (from UCO) would react via glycerolysis reactions
Dry transverse 7885.9 ± 2770.1 ± 4939.2 ± >1779 N: High-
strength (N) 135.7 38.9 29.2 profile
[43], and solidified gradually. The binder would solidify at the end of
>1334 N: Low- the curing process, hold the mixture together and form a proper binding
profile
Water absorption 6.69 7.46 10.81 <6%: Grade 1
(%) <11%: grade 2
<13%: Grade 3
Wet transverse 1428.9 ± 853.2 ± 911.3 ± >1334 N: High-
strength (N) 89.5 55.0 101.3 profile
>1001 N: Low-
profile
Permeability Pass Pass Pass Impermeable to
water
capacity of fly ash [41]. In addition, the presence of three hydroxyl

groups in the chemical structure of glycerol, which readily forms
hydrogen bonds and make it hydrophilic towards water molecules [42].
As the composition of fly ash in the samples was fixed, it was predicted
that the water absorption of the specimens would continuously increase
when the composition of glycerine pitch increased. This explains the
situation in which the water absorption of the samples increased grad
ually when the mixing ratio of glycerine pitch in the blended organic
binder increased from 30 to 70%. Binder A specimen with 30% of
glycerine pitch showed the lowest absorbability compared to Binder B
Fig. 9. SEM image of cured sample.
8
matrix, as shown in Fig. 9. avoided when the water molecules formed at the end of the reaction are
However, the unreacted glycerol, or the free hydroxyl groups from driven off under high temperature [46]. The efficiency of glycerolysis
mono- and diglycerides, still exhibits the hydrophilic effect towards the reactions can be further enhanced when the composition of FFA was
water molecules. This might explain the higher water absorption of the around 50–60% to shift the equilibrium towards the products [47].
specimens with a greater composition of glycerine pitch. In addition, the
Glycerol + FFA Monoglycerides + water (4)
strength of these specimens reduced drastically after 24 h of immersion
in water. This weak wet transverse strength is caused by the penetration Monoglycerides + FFA Diglycerides + water (5)
of water molecules into the body of the specimens. Theoretically,
unreacted hydrophilic glycerol tends to fully or partially dissolute by the Diglycerides + FFA Triglycerides + water (6)
water molecules [30]. The presence of H+ and OH− ions from the water
Diglycerides + glycerol 2 Monoglycerides (7)
molecules pave a way to neutralise the polarized glycerol. Neutralized
glycerol molecules would thus be dissolved and leached into the water, Triglycerides + glycerol Monoglycerides + Diglycerides (8)
leaving a significant number of pores within the specimens. This is
supported by the porosity test results as shown in Table 7, where the Monoglycerides + Triglycerides 2 Diglycerides (9)
porosity of roofing tile specimens has increased significantly after the Besides the strength development process via the esterification re
water absorption test. The increase in the porosity subsequently actions with glycerol, UCO can also solely contribute to the strength
weakens the binding matrix of the specimen. development of the roofing tile. During the curing process at 190 ◦ C, it
was discovered that some white fume and strong odour were emitted
3.4. Proposed chemical reactions between GP and UCO upon thermal from certain specimens and became darker in colour at the end of the
treatment curing process. These phenomena indicated the decomposition and
oxidation of UCO [48]. The decomposition of UCO would release more
In this study, two different types of waste materials were used as the FFA into the binder, which is a more active reactant for the strength
alternative binder. Under the elevated temperature, the waste binders development process. Another reaction of UCO is the condensation
with different components and functional groups would undergo spe polymerization reaction. When an excessive amount of UCO is exposed
cific reactions that lead to the hardening process. Owing to the chemical to heat energy, it would trigger the chemical reaction between the FFA
composition of those binders, three chemical reactions as follow may and glycol to produce larger molecular species [25]. In addition, the
happen and help Eco-Roofing tile to gain strength during the curing cross-linking between the polymers via glycol compounds, or perhaps
process: with the glycerides are able to further enhance the mechanical strength
of the roofing tile specimens.
• Polarization of glycerol: Glycerol dehydrate to be polarized. It was found that the specimens produced from Binder A, which
• Glycerolysis reaction: Reaction between glycerol and free fatty acids composed of 70% of UCO, possessed the greatest mechanical properties
(FFAs) from used cooking oil (UCO). compared to Binder B and Binder C. In Binder A, the high composition of
• Esterification reaction: Reaction between UCO components, which FFA presence in UCO would shift the equilibrium of glycerolysis reaction
are FFAs and glycol. (reaction 1–6) towards the products, and hence produced a greater
number of glycerides compounds. The number of di- and triglycerides
When pure glycerol was heated at high temperature, it is well known produced will be higher with the excessive amount of UCO, while the
that the glycerol would be fully vanished and leave no residues. How presence of glycerides with a larger molecular size would significantly
ever, in glycerine pitch (GP), the interface between the glycerol and the increase the viscosity of the corresponding binder. The number of
free fatty acid (FFA) resulted in a sticky component with very high molecules with larger molecular size continued to grow to such an
viscosity. The interfacial with the oil components prevents glycerol from extent that they would no longer remain in the liquid state. As a result,
being evaporated under the elevated temperature. After being heated, several solid materials such as varnish or sludge would be present in the
the glycerol would release a water molecule via dehydration reaction to binder. At the end of the thermal treatment, the blended organic binder
produce polarized glycerol [28]. Polarized glycerol would form better (BOB) would be fully converted into solid form, resulting in the for
bonding with other components in the binder, subsequently enhanced mation of a hard, rigid binder [33]. However, a chemical reaction is
the stickiness of the heated glycerine pitch, and hence produced a never ideal. The unreacted UCO and GP would continue to undergo
greater bonding force with the aggregate and filler particles. condensation polymerization and dehydration reaction and hence
Free fatty acids from UCO would readily react with the polarized further enhance the mechanical strength of the specimens produced.
glycerol via esterification/glycerolysis reactions to produce mono Furthermore, crosslinking between the polymers and glycerides pro
glycerides (reaction 4). In this reaction, the alcohol group (R–OH) from duced would also contribute to strength development. The rate of po
glycerol would react with the carboxylic acid group (R–COOH) from free larization of glycerol is relatively low may be due to the high reaction
fatty acids (FFAs) to produce a monoglyceride with an ester group extent of glycerolysis and condensation polymerization reactions.
(R–COO–R’) and released a water molecule. Under the presence of In the case of Binder C, UCO builds up 30% of the total binder
excessive FFAs, the transesterification process would occur. This process content, hence the composition of FFA is insufficient for the effective
involved the reaction between monoglycerides with FFAs to produce glycerolysis reaction [47]. However, components of UCO and GP are still
other forms of glycerides, which are diglycerides and triglycerides (re reactive under elevated temperature. The occurrence of condensation
actions 5–9) [44]. These reactions are reversible when water molecules polymerization reactions between the FFA and glycol, as well as the
hydrolyse the mono-, di- and triglyceride (products) and regenerate the interactions of polarized glycerol with other components in the matrix,
glycerol (reactant) again [45]. However, this reversible reaction can be would still contribute to the strength development of the specimens. As a
result, the strength developed by Binder C reached 7.89 MPa as showed
Table 7 in Table 6.
Porosity test of specimens produced from different binder. Lastly, the Binder B specimens possessed the lowest strength among
the three types of binders, as shown in Table 6. Binder B consists of 50%
Properties Binder A Binder B Binder C
of UCO and 50% of GP. Theoretically, the 1:1 stoichiometric molar ratio
Porosity (before water absorption test) 8.43 10.23 9.06
between glycerol and FFA is proved suitable for high conversion towards
Porosity (after water absorption test) 12.60 18.68 21.70
Change in porosity (%) 49.47 82.60 139.51 monoglycerides [49]. Hence, the glycerolysis reactions are the main
9
contributor to develop the strength of the specimens. Besides, the high development of the specimens. Table 8 shows that the addition of 1% of
conversion rate of glycerolysis reactions makes the contribution of DDDA increased the dry transverse strength of Specimen II by 13.9%
condensation polymerization and polarization of GP negligible in the compared to the control specimen. The percentage of water absorbed by
binding process. Specimen II showed significant improvement after adding with DDDA,
By relating the chemical reactions and the strength achieved of these which was reduced to 5.32% and fell within the requirement of ASTM
three binders, strength developed by Binder A via glycerolysis and standard. However, the improvement on the wet transverse strength was
condensation polymerization achieved the highest strength, followed by still unsatisfactory, indicating that water molecules penetrating into the
Binder C (strength development via condensation polymerization and specimen resulted in the dissolution of glycerol in it and hence weak
polarized glycerol) and Binder B (strength development via glycerolysis ening the binding matrix of the specimen. Even though the water affinity
and polarized glycerol). Hence, it can be concluded that the condensa of glycerol can be further decreased by the addition of higher amount of
tion reaction which solely involved the UCO components has contrib DDDA, this would lead to a negative impact on the economic aspect of
uted to most of the strength development of the specimens, far beyond the specimens.
the contribution of glycerolysis reaction and polarization of glycerol. A more cost-effective and sustainable approach was attempted by
Comparison between Binder B and Binder C revealed that the strength utilizing the UCO as a protective layer of the modified specimen. Prior to
produced from 30% of condensation polymerization in Binder C is much the curing process, the modified specimen was pre-cured to fix its shape
greater than 100% of the glycerolysis that occurred in Binder B. The and to allow the evaporation of the volatile components. This process
polarization of glycerol contributed the least in strength development in left a significant number of pores on the surface of the specimens. When
the binding matrix. The formation of ionic bonding between the polar the pre-cured specimen was sprayed or immersed in UCO, the UCO
ized glycerol with other incorporated components is relatively weak component would fill up the pores and form a hydrophobic layer that
compared to the strength of the larger molecules formed from other covers the whole specimen. This process significantly enhanced the lotus
reactions. effects of the specimen’s surface. It is supported by the results of water
contact analysis as shown in Fig. 10. The coated specimens achieved a
water contact angle greater than 90◦ , which indicated that the coated
3.5. Alternative solution to enhance the mechanical properties of Eco-
layer is hydrophobic in nature.
Roofing tile
Specimen with great lotus effects tends to prevent or retard the
penetration of water molecules into the specimen, consequently, reduce
There are several ways to enhance the water resistivity of the spec
its water absorbability. This explains the results shown in Table 8, in
imens, which include: (i) incorporation of dodecanedioic acid (DDDA),
which specimens III and IV possessed a low percentage of water ab
and application of UCO coating by (ii) spraying or (iii) immersion
sorption, ranging from 3.00 to 3.08%. Besides, the UCO layer also
method. The first attempt involves the incorporation of 1% of DDDA into
contributed to the strength of the specimen via the esterification process.
the BOB prior to the manufacturing process. DDDA is a dicarboxylic
The free fatty acids from UCO would react with the glycerol present in
acid, which serves as an additive to enhance the strength and water
the original specimen through glycerolysis [43,44]. Hence, the reactions
resistivity of the specimens via cross-linking and esterification reaction
further enhance the interconnection between the binder and other ma
with glycerol. The second attempt further enhanced the water resistivity
terials within the roofing tiles. Fig. 11 shows the proposed coating
of the modified specimen by coating it with a protective layer made from
process of the specimen by the immersion method. Even though this
UCO. In the latter process, the uncoated specimens were pre-cured under
process may just enhance the binding developed at the outer layer of
190 ◦ C for 4 h, followed by the coating process through spraying or
roofing tiles, the strength achieved by the roofing tiles was increased to a
immersion method. The specimen coated with a layer of UCO needed to
significant extent. A comparison made between the modified specimens
be heat cured for another 2 h alternately before applying the second and
revealed that the dry transverse strength achieved by Specimen III was
third layers of UCO film onto its surface. After the coating process was
increased by 5.4%, while a much significant increment was found in
completed, the specimens were left to continue their heat curing pro
Specimen IV, where its strength was enhanced by 66.5% to achieve
cess, until the total curing duration is equal to 24 h.
The high water absorbability of GP is due to the presence of polyol
groups in the glycerol, which can easily form hydrogen bonding with
water molecules [50]. Hence, an idea to fully react the hydroxyl groups
to reduce their affinity towards water molecules was proposed. Dodec
anedioic acid (DDDA) reacts with glycerol via the esterification process
to produce glycerol ester [51]. Hence, it decreases the concentration of
hydroxyl groups in the blended organic binder. Besides, as DDDA is a
dicarboxylic acid, it can form a cross-linkage when reacted with two
glycerol units or unsaturated glycerides, thus, enhance the strength
Table 8
Mechanical properties of specimens produced under different conditions.
No. Samples Coating Average transverse Percentage of
method strength (N) water
absorption (%)
Dry Wet
I Control NA 2770.08 853.25 ± 7.46 ± 0.55

specimens ± 176 55
II Catalysed NA 3154.86 925.72 ± 5.32 ± 0.9
specimens ± 525 100
III Oil-coated Spraying 3324.98 1695.36 3.08 ± 1.15
catalysed ± 263 ± 82
specimens (A)
IV Oil-coated Immersed 5252.05 2696.83 3.00 ± 0.91
catalysed ± 93 ± 113
Fig. 10. Water contact angle of (a) control sample; (b) UCO coated sample via
specimens (B)
spraying method; (c) UCO coated sample via immersion method.
10
Fig. 11. Coating process of the roofing tiles by the immersion method.
5252.05 N. In addition, the wet transverse strength achieved by Speci 2.42% and 1.91% respectively. The first UCO protective layer should
mens III and IV were 1695.36 and 2696.83 N respectively, far exceeded have covered most of the pores on the surface of roofing tiles. However,
the minimum requirement of 1001 N as per ASTM standard. However, it it was suspected that some part of the tile surface was exposed after the
was noticed that after 24 h of immersion in water, the strength of volatile compounds from the UCO has evaporated during the heating
Specimens III and IV has lost by 48.6–49.0%. Hence, it can be concluded process. Hence, further application of the second and third layers of UCO
that even they possessed a lower percentage of water absorption, pro would help to cover up the new pores and thus improved the water
long water immersion has shown a significant impact on the binding of resistivity of the tiles.
the specimens. However, it was also found that the average strength of roofing tiles
decreases drastically with the increase of the coating layer. Table 9 re
veals that the dry transverse strength achieved by sample VI with a
3.6. Number of coated layers towards the mechanical properties of single coating layer was 4686.99 N, which was relatively higher than
roofing tiles samples VII and VIII coated with two and three UCO layers respectively.
This can be explained that with the increase of the number of coating
The effect of multiple coated layers on the mechanical properties of layers, more heat energy is needed for the polymerization process of the
roofing tiles was investigated in this study. The coating layers were UCO layer. In addition, it was suspected that the coating layer has also
applied through the immersion method. As shown in Table 9, the UCO restricted and slowed down the transmitting of heat energy into the
coating layer is effective in decreasing the percentage of water absorbed core/the centre part of the roofing tiles. Such results indicated that the
by the specimens. By coating the roofing tiles with a single layer of UCO, roofing tile requires a longer heating duration to cure the samples
the water absorption of the sample decreased by 54.7% compared to the completely. It can be concluded that 24 h is insufficient to completely
uncoated samples. When the second and third layers of UCO was cure and increase the strength of the samples with multiple coating
applied, the water absorbed by the samples were further reduced to layers. It is suggested that a single UCO layer is sufficient. This is because
other than being able to decrease the percentage of water absorption of
Table 9 the samples below its minimum requirement, it is also able to develop
Mechanical properties of specimens with different coating layers. higher strength.
No. Number of Transverse Strength (N) Water Absorption
Layer (%)
Dry Wet
3.7. Feasibility of glycerine pitch being used as sole binder in the
V 0 2770.08 ± 853.25 ± 55 7.46 ± 0.55 production of roofing tiles
176
VI 1 5252.05 ± 93 2696.83 ± 3.00 ± 0.91
113 The feasibility of glycerine pitch (GP) as the sole binder in the pro
VII 2 3528.60 ± 1396.85 ± 2.42 ± 1.29 duction of roofing tiles was investigated in this section. GP possessed a
192 313 significant amount of dust, which limited its application in other in
VIII 3 2920.55 ± 1304.18 ± 1.91 ± 1.03 dustries. Besides, the disposal of these materials requires large space for
275 100
landfill whilst the rainwater may bring out certain harmful, soluble
11
components and contaminate the groundwater or water strain. Hence, Table 11

increasing the usage of GP in the production of roofing tiles is a good Mechanical properties of coated and uncoated GP-RT.
alternative solution for the waste management of glycerine pitch. Name Average Strength Percentage of Water Average Strength
Due to the high viscosity of GP, it was diluted with 10% of distilled (Dry Condition) Absorption (%) (Wet Condition)
water to enhance its mixability with other ingredients. Table 10 shows DTS (N) FS WTS FS
the strength of the specimens produced by utilizing 9–12% of GP as a (MPa) (N) (MPa)
sole binder. In this investigation, the maximum usage of GP is limited to Uncoated 2166.14 4.46 20.13 384.14 0.96
12%, as a higher percentage of binder would lead to the crumble of GP-RT
sample during the curing process, and increasing in pore size and Coated GP- 2924.46 6.32 4.64 1778.51 3.84
number, similar to the condition encountered in Figs. 7 and 8. Among RT
these GP-made roofing tiles (GP-RT), the highest strength was achieved * DTS = dry transverse strength.
when 12% of GP was utilized, which were 2166.14 N or equivalent to * WTS = wet transverse strength.
4.46 MPa. This value had fulfilled the minimum requirement of 1779 N * FS = flexural strength.
as per ASTM standards.
However, the hygroscopic behaviour of GP has led to a high per
centage of water absorption of the specimens, which was 20.13%. This
problem can be overcome by coating the specimen with a single layer of
UCO film via the immersion method. The mechanical properties of the
uncoated and coated GP-RT are shown in Table 11. Generally, the per
formance of the coated GP-RT is satisfying, as it showed a huge
enhancement in terms of the mechanical strength and resistivity towards
the water absorption. Compared to uncoated specimens, the strength of
coated GP-made sample increased by 35% and achieved 2924.46 N,
while the percentage of water absorption was reduced by 76.9%, from
20.13 to 4.64%. Besides, the wet transverse strength of specimens is
1778.51 N. Conclusively, the performance of coated GP-RT had fulfilled
all the basic requirements to be qualified as a standard roofing tile (as
per ASTM standards). Hence, glycerine pitch has high feasibility to be
used as a sole binder in the production of roofing tiles, as well as other Fig. 12. Carbon emission of Eco-Roofing tiles, cement tile, and clay tile.
building materials. However, the hydrophilic nature of glycerine pitch
still poses a great challenge for it to be used as a raw material for 1.89% in carbon emissions compared to BOB-RT. The slight differences
products that need to fulfill higher property requirements. between the embodied carbon of BOB-RT and GP-RT are caused by the
Comparing to the overall performance of the specimens produced in different emission factors of GP and UCO. In this study, the raw mate
this study, GP-RT which was produced by using GP as the sole binder rials used in the production of Eco-Roofing tiles, such as glycerine pitch,
possessed the lowest strength compared to those specimens produced by fly ash, and fine sand possessed zero carbon emissions [52,53], while the
using a blended organic binder. This is because most of the strength of carbon emission factor of UCO is as low as 0.004 kgCO2/kg [25].
GP-made roofing tile is provided by glycerol, where the polarization of However, they still contribute to the carbon emissions in transportation
glycerol forms weaker bonding with the grains of sand and ash particles. during the collection of materials, as well as the distribution of products
When UCO was incorporated as a protective layer, the UCO components and end-of-life management. Besides, the energy consumption during
which diffused into the outer layer of GP-RT would undergo glycer the production of Eco-Roofing tiles also contributes to carbon emissions.
olysis, which occurs between FFAs (from UCO) and glycerol (from GP). As a result, the carbon emissions of BOB-RT from the raw materials,
In addition, condensation polymerization that occurs between the manufacturing process, and transportation are 0.19, 20.87, and 78.94%
components of UCO can also significantly improve the strength of the respectively, and 0.05, 20.91 and 79.04% for GP-RT. The percentages
specimens. distribution of carbon emissions from different sectors is shown in
Fig. 13.
The results indicate that both types of Eco-Roofing tiles possessed
3.8. Environmental assessment of Eco-Roofing tiles
much lower embodied carbon compared to conventional roofing mate
rials, this is because the conventional raw materials, such as cement and
The environmental assessment of Eco-Roofing tiles (BOB-RT and GP-
clay or ceramic which possessed a higher carbon factor, were fully
RT) in terms of their embodied carbon was analysed and shown in
replaced by several waste materials [29]. This is in line with the findings
Fig. 12. The estimated carbon emissions of the Eco-Roofing tiles through
from previous researches, where the reduction in carbon emission was
the cradle to gate (materials extraction and manufacturing), cradle to
reported after the replacement of Portland cement with marble dust
site (distribution of products), and cradle to grave (end of life manage
[21], or supplementary cementitious materials [54]. It is also revealed
ment) were determined. According to the result, the embodied carbon of
that the embodied carbon of building materials decreases with the in
BOB-RT was 131.38 kg. CO2/tonne, while the embodied carbon of GP-
crease of waste content in the manufacturing process. Hence, the com
RT was reported as 128.90 kg. CO2/tonne, indicating a reduction of
plete replacement of cement in this project is considered more
environmentally friendly as it significantly decreases the embodied
Table 10 carbon of a building materials. In Fig. 12, a comparison study was made
Average strength achieved by GP-RT.
in terms of the carbon emissions of the Eco-Roofing tiles with the con
No. Percentage of binder Average DTS (N) Average Flexural Strength ventional roofing tiles. As reported in the PAS 2050 Assessment of
(MPa) Concrete and Clay Roof Tiles Summary Report, the embodied carbon of
IX 9% 801.41 1.73 concrete and clay tile is ranging from 206 to 224 kg. CO2/tonne and
X 10% 1459.23 3.16 265–460 kg. CO2/tonne [55]. Hence, it is obvious that the Eco-Roofing
XI 11% 1842.27 3.98
tiles produced in this study can reduce the carbon emission by
XII 12% 2166.14 4.46
37.4–42.5% with respect to the concrete roofing tiles, and 51.6–72.0%
*DTS = dry transverse strength.
12
Fig. 13. Percentage of carbon emission from the life cycle of Eco-Roofing tiles.
compared to the clay roofing tiles. Therefore, it can conclude that the
utilization of blended organic binder or glycerine pitch as the alternative
binder in the production of roofing tiles is a more environmentally
friendly approach, which is able to effectively reduce the emission of
carbon dioxide from the construction sector.
In addition, the embodied energy of the Eco-Roofing tiles was taken
as the total primary energy consumed over its manufacturing process.
Among the Eco-Roofing tiles, it was discovered that the embodied en
ergy of the GP-RT is in the lower site with respect to BOB-RT. As shown
in Fig. 14, it was estimated that 201 and 102 MJ of energy were
consumed while producing a tonne of BOB-RT and GP-RT respectively.
The higher energy consumption of BOB-RT is due to the usage of UCO as
one of the ingredients of alternative binder, which possessed embodied Fig. 14. Energy consumption of Eco-Roofing tiles, cement tile, and clay tile.
energy of 2.0 MJ/kg [56]. The findings from previous research discov
ered that the embodied energy of concrete and clay roofing tiles is
covered on the sand and ash particles, consequently formed an inter
ranging from 1594 to 1650 MJ/tonne and 4590–6500 MJ/tonne
particle bonding during the curing process. The packing and filling ef
respectively, which is much higher compared to the Eco-Roofing tiles
fects of fine sand and fly ash further improved the strength of the
produced in this study. This is because the traditional roofing tiles are
specimens.
mainly produced from cement and clay which possessed embodied en
In terms of the environmental aspects, both BOB-RT and GP-RT
ergy as high as 4.6 ± 2 MJ/kg and 3.0 MJ/kg [57], consequently, in
possess lower embodied carbon, which show a reduction of
crease the embodied energy of the building materials produced. By
37.4–42.5% and 51.6–72.0% compared to concrete and clay roofing
comparing the data, it was found that the embodied energy of the
tiles respectively. Incorporation of waste binder in Eco-Roofing tiles
Eco-Roofing tiles is 87.4–87.8% and 95.6–96.9 lesser than concrete and
shows an effective reduction in terms of the embodied energy as well.
clay roofing tiles, effectively reduce the energy consumed during the
The embodied energy of Eco-Roofing tiles is 87.4–87.8% and 95.6–96.9
manufacturing process. The replacement of traditional high
lesser than concrete and clay roofing tiles, respectively. In conclusion,
energy-consuming binders, such as kiln firing in clay and cement pro
the Eco-Roofing tiles have shown comparable mechanical properties
duction in concrete roofing tiles successfully reduces the energy con
with the conventional roofing materials; whilst recycling and imple
sumption to a significant extent. Hence, the binder from waste, such as
mentation of waste materials in the manufacturing process culminates in
used cooking oil and glycerine pitch with lower embodied energy could
sustainable development and paves an alternative way for their sus
be classified as an environmentally friendly binder.
tainable application in future.
4. Conclusion
CRediT authorship contribution statement
In this study, the feasibility of blended organic binder (mixture of
Wei Ping Teoh: Investigation, Formal analysis, Writing – original
glycerine pitch and used cooking oil) to produce environmentally
draft, Visualization, Validation. Swee Yong Chee: Supervision, Writing
friendly roofing tiles has been studied. Besides, the possibility of glyc
– review & editing. Noor Zainab Habib: Conceptualization, Method
erine pitch as the sole binder has also been investigated. The optimized
ology. Mohammed J.K. Bashir: Supervision. Vui Soon Chok: Re
specimen produced from both binders possessed significant strength,
sources. Choon Aun Ng: Supervision, Project administration, Funding
low water absorbability, and impermeable to water, fulfilling the re
acquisition, Writing – review & editing.
quirements as a high-profile tile according to ASTM standards. The
water absorption of the specimens can be further reduced by the addi
tion of dodecanedioic acid and the UCO coating process. This practice, Declaration of competing interest
which incorporated various waste materials in the production of roofing
tiles, can reduce the excessive waste disposal issues, decreases the The authors declare that they have no known competing financial
consumption of virgin materials, whilst culminating in benefits towards interests or personal relationships that could have appeared to influence
lower cost, cleaner production, and sustainable development. the work reported in this paper.
The predominant chemical reactions which lead to the hardening of
Eco-Roofing tiles are glycerolysis and esterification reactions for
Acknowledgement
blended organic binder (BOB), and polarization of glycerol through
dehydration process for glycerine pitch (GP). These reactions occur
We would like to extend our gratitude to Ministry of Education for
under elevated temperatures and lead to the rigidification and hard
the FRGS fund with project No. FRGS/1/2015/TK06/UTAR/02/1 and
ening of roofing tiles. The binding mechanism is known as an encap
Universiti Tunku Abdul Rahman for the UTAR RESEARCH FUND with
sulation process, where the polymerized components from binder
project No. IPSR/RMC/UTARRF/2018-C2/N01. Moreover, the authors
13
are thankful to TNB Janamanjung Sdn. Bhd. and KL-Kepong Oleomas industry, Cement Concr. Res. 114 (2018) 2–16, https://doi.org/10.1016/j.
cemconres.2018.03.015.
Sdn Bhd for providing the fly ash and glycerine pitch for this research
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Journal of Building Engineering 43 (2021) 102869

Contents lists available at ScienceDirect

Journal of Building Engineering

Chemical investigation and process optimization of glycerine pitch in the

1. Introduction waste materials, which composed of highly organic, biodegradable, and

Fig. 1. Manufacturing process of an innovated roofing tile.

2.5.4. Water permeability 3. Results and discussion

group is not involved in the expected chemical reactions. The presence

3.2. Optimization of types of blended organic binder and the percentage of

This section discusses the strength achieved by the specimens pro

Fig. 3. Combined ATR-FTIR spectra of Binder A, B and C.

Fig. 4. Flexural strength of the specimens produced from blended

3.3. Mechanical properties of the optimized specimens

and Binder C specimens, which composed are of 50 and 70% of glycerine

capacity of fly ash [41]. In addition, the presence of three hydroxyl

I Control NA 2770.08 853.25 ± 7.46 ± 0.55

components and contaminate the groundwater or water strain. Hence, Table 11

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Ping 2021

Uploaded by

Copyright:

Available Formats

Ping 2021

Uploaded by

Document Information

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Ping 2021

Uploaded by

Copyright:

Available Formats

Journal of Building Engineering 43 (2021) 102869

Contents lists available at ScienceDirect

Journal of Building Engineering

Chemical investigation and process optimization of glycerine pitch in the

1. Introduction waste materials, which composed of highly organic, biodegradable, and

Fig. 1. Manufacturing process of an innovated roofing tile.

2.5.4. Water permeability 3. Results and discussion

group is not involved in the expected chemical reactions. The presence

3.2. Optimization of types of blended organic binder and the percentage of

This section discusses the strength achieved by the specimens pro­

Fig. 3. Combined ATR-FTIR spectra of Binder A, B and C.

Fig. 4. Flexural strength of the specimens produced from blended

3.3. Mechanical properties of the optimized specimens

and Binder C specimens, which composed are of 50 and 70% of glycerine

capacity of fly ash [41]. In addition, the presence of three hydroxyl

I Control NA 2770.08 853.25 ± 7.46 ± 0.55

components and contaminate the groundwater or water strain. Hence, Table 11

You might also like

This section discusses the strength achieved by the specimens pro