Solar Energy 269 (2024) 112338

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Solar Energy
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Experimental investigation on utilization of crushed solar panel waste as

sand replacement in concrete
Sarita Zele a, *, Amrut Joshi a, Nivedita Gogate a, Deepti Marathe a, Amar Shitole a, b
a
Dr Vishwanath Karad, MIT World Peace University, Pune, Maharashtra 411038, India
b
Pimpri Chinchwad College of Engineering and Research, Pune, Maharashtra 412102, India

A R T I C L E I N F O A B S T R A C T

Keywords: Solar power has seen tremendous growth in the last few decades across the globe, which has also led to
Solar panel waste increasing waste generated from the damaged and End of Life (EoL) solar panels. Typical solar panel waste
End of life consists largely of glass (>70 %) and the rest is metals (Si, Cu, Ag) and polymers (EVA, PVDF, PET). Recycling
Recycling
solar panels by separating each layer is a complex, extremely energy intensive, and expensive process. Most of
Sand replacement
Waste glass concrete
the solar panel waste thus ends up in landfill. In view of the large quantities of solar panel waste being generated,
an economical and environmentally friendly solution is required for its safe disposal. This work evaluates the use
of solar panel waste as sand (fine aggregates) replacement in producing concrete. We have conducted a
comprehensive characterization study of the solar waste sand (SWS) prepared by crushing solar panels. Field-
used and discarded crystalline silicon photovoltaic panels were collected, and post removal of frames the lam­
inates were crushed to achieve sand like size gradation. All the significant physical and chemical properties are
evaluated as per relevant codes for fine aggregates. The results indicate that the particle size distribution and
fineness modulus of SWS lies within permissible range. The water absorptivity, specific gravity, and silt content
are in the acceptable range for fine aggregates as per the code stipulations. The potential alkali aggregate
reactivity is evaluated to check the possibility of expansion cracking in concrete. Further, concrete cubes are
prepared with the solar panel waste as sand replacement. Their compressive strength (3, 7, 28 days) tests indicate
that it is possible to achieve desired strength of concrete by developing an appropriate design mix with the solar
panel waste. Our study clearly establishes that SWS is suitable to replace fine aggregates in concrete. This
approach can provide a sustainable pathway for large scale solar panel waste recycling. It will also help conserve
sand, a fast-depleting natural resource.

1. Introduction between two sheets of polymer (EVA - Ethylene Vinyl Acetate) and a
front glass on top and a backsheet, which is a combination of polymers
Solar Photovoltaic (PV) installations have grown exponentially in the (PET and PVDF) [3]. This assembly known as ‘laminate’ is held together
last few years in India and across the globe as solar power is seen as a with an aluminium frame around it and has a junction box to hold the
clean, efficient, and environmentally friendly source of energy. World­ cable connectors at the back. To protect the solar cells from any envi­
wide PV installation has already crossed 1 TW and the top five countries ronmental damages, the upper and lower surfaces of the cells are bonded
(China, USA, Japan, Germany, and India) contribute around 70 % of the to the glass and backsheet with EVA by a lamination process carried out
total PV installations [1]. The global crystalline silicon (c-Si) cell and PV under vacuum [4]. Fig. 1 shows a cross-sectional view and the layers in
module production has increased to 600 GWp at the end of 2022 [2]. the laminate of a typical c-Si module. EVA is the most preferred
Among the technologies available for solar PV, c-Si has the largest share encapsulant used in the PV industry as it provides the necessary optical
of the global market due to its high conversion efficiency, rapid reduc­ transmission, mechanical support, moisture resistance, and electrical
tion in cost over the years and vast field history. A typical c-Si solar PV isolation [5]. The lamination process ensures that the solar panels
module (panel) is made up of several silicon cells connected in series, deployed in the field can continue to produce power in extreme climatic
which are the key components of the module. The cells are encapsulated conditions without being impacted by any harsh environmental

* Corresponding author.
E-mail address: sarita.zele@mitwpu.edu.in (S. Zele).

https://doi.org/10.1016/j.solener.2024.112338
Received 14 August 2023; Received in revised form 8 November 2023; Accepted 9 January 2024
Available online 19 January 2024
0038-092X/© 2024 International Solar Energy Society. Published by Elsevier Ltd. All rights reserved.
S. Zele et al. Solar Energy 269 (2024) 112338

recovered materials are mixed and difficult to separate, and have low
value so the cost of recycling can barely be met. They have conducted a
comparative analysis of several silicon PV recycling technologies and
presented the economic viability of three common EoL treatment ap­
proaches: landfill, glass recycling, and thermal recycling. Landfilling is
the cheapest option when disposal fees are low. However, it is not sus­
tainable and causes environmental burden, besides loss of valuable
metals [16]. Glass recycling appears economically feasible where land­
fill fees are high, or where disposal of modules in landfill is prohibited
[5]. However, implementation of this is not widespread because of
technical challenges in removing impurities from glass and high cost of
processing [5,17]. Thermal recycling of modules with high value re­
covery of Si wafers and metals like Cu and Ag has been proposed by
previous studies [11,17,18]. Researchers have also shown recovery of Si
Fig. 1. Layers in a laminate of c-Si PV module: (a) cross-sectional view (b) layer wafers using chemical methods by dissolution of EVA in organic solvents
description. [18,19]. Unfortunately, this recovery approach is not found to be
practical due to long duration of treatment. Besides, the recovered cells
exposures. During the lamination process, the crosslinking reaction of can become damaged and may have defects making it difficult to be
EVA takes place, which dramatically alters its characteristics and pro­ accepted by manufacturers [19]. To recover Si from the solar cells,
vides the required adhesion between the solar cells, glass, and backsheet multiple chemical treatment steps are required. These include KOH
[6]. The strong and durable bond between the various layers of solar treatment to remove Al electrode from cell backside, HNO3 etching
panel provides the necessary capability to continuously function and followed by NaCl solution to remove Ag and HF to remove anti-reflector
produce power for decades in the field. However, it is also the primary from front surface [7]. The recovered glass from the solar waste cannot
reason, which makes the recycling of waste solar panels very complex be directly recycled. It needs multiple treatment steps like mechanical
[5]. shredding or milling and sieving followed by chemical treatment to
A typical solar panel has a life expectancy of 25 years and at the End separate the semiconductor and polymers embedded in it [17]. More­
of Life (EoL) the waste panel needs to be disposed safely or recycled. over, the chemical treatment for separation of glass from polymers has
With the enormous growth in solar PV installations globally, EoL man­ the disadvantage of long processing times and disposal of liquid waste
agement of solar panel waste is becoming an increasingly significant making it unsuitable for recycling of high volumes of EoL solar panels
issue. At the end of 2050, the cumulative global solar PV waste is pre­ [19,20].
dicted to be 60–78 MT [7]. At the present, most countries have classified PV recycling is still facing a lot of economic viability and techno­
solar panel waste as general or industrial waste, while European Union logical challenges. Mainstream method for disposal of EoL solar panels
has PV specific electronic waste regulations [8]. Based on the Extended till date is landfilling in many regions across the globe including India
Producer Responsibility Principle, the European Union’s Extended [16,21]. Most of the experimental recycling work was carried out using
WEEE (Waste Electric and Electronic) Directive requires all PV pro­ lab scale small panels [5,11]. Recycling process used to demonstrate
ducers supplying to European market to finance the costs of collecting layer separation on small lab-scale panels or coupons may not work with
and recycling the PV panels put on the market in Europe. In USA, a same efficiency on actual field used standard (200 Wp or larger) mod­
voluntary recycling program was initiated by the Solar Energy Industry ules. The interlayer adhesion in a standard 200 Wp module is much
Association (SEIA) in 2016 [8]. In India, waste solar panels and cells stronger due to the typical industrial lamination process than a small 2.5
have been added in the electronic waste management rules by the Wp panel made with cut cell pieces. The efficiency of material recovery
Ministry of Environment, Forest, and Climate Change (MoEFC) in 2022. from PV recycling will be highly dependent on this bond strength so the
As per the current draft guidelines, every solar PV cell and module lab scale recovery processes will need to be further optimized. The PV
manufacturer must maintain waste inventory and store the waste solar recycling methods mostly assume that the EoL panels when brought for
modules and cells until the final solar waste management guidelines are recycling will be in pristine conditions. However, most decommissioned
available [9]. modules when brought to recycling have broken/cracked glass, due to
EoL management of solar panels is fast becoming a significant part of the nature of scrap handling and transportation. This will further lower
the PV value chain and offers various opportunities to recycle materials the material recovery and increase quantity of material going into
from solar panel waste. However, in India, due to absence of commer­ landfill. Due to these limitations in PV recycling, there is a need to
cially viable process for recovery of usable materials and lack of develop an environmentally friendly and economically viable technol­
mandatory regulations, much of the solar panel waste is currently ogy, which can handle large volumes of solar panel waste. The present
disposed of in landfill [7]. Research scientists are currently working on work attempts to address this gap through examining a possibility where
recycling of solar panel waste with different objectives. Most are focused EoL PV waste can be upcycled and used in construction as concrete.
on recovering the valuable metals like Al, Ag, Cu, and Si and few are In many countries, including India, there is a high chance that the
looking at separating Si cells or glass for reuse [10–15]. The approach laminates will be disposed in landfill [17]. Environmental impact
used by most researchers for recycling of c-Si solar panels involves layer assessment studies of disposal of EoL panels using different pathways
by layer separation using combinations of mechanical, thermal, and [14,16,20,21] have indicated that responsible methodologies need to be
chemical processes [14]. Typically, waste recyclers remove the Al developed to minimize the associated environmental burdens. Life Cycle
frames from the solar panels and the laminates (panels without the Assessment studies have indicated that PV industry can benefit by
frames) are subjected to different process steps depending on the developing synergies for industrial symbiosis [22]. PV recycling can
objective of recycling [5]. The laminates consist of metals (Si cells with become successful only if the materials used for manufacturing of solar
traces of Ag, Cu, Zn, Pb) embedded with polymers (EVA, PET, PVDF) and modules can be reused even after its useful life of 25 – 30 years. Rao et al.
tempered glass. These components are separated by a delamination have suggested use of EoL PV in buildings by integrating as building
process involving high energy thermal process such as pyrolysis, me­ element [1]. Experimental work on characterization of thermal and
chanical crushing, and chemical dissolution [12–14]. A techno- mechanical behaviour of waste solar panels indicate that they can be
economic review by Deng et al.[5] reported that the most popular used in ceramic tiles for similar technological performance [26].
solar PV recycling technologies are economically unattractive, the Various waste materials have been utilized in concrete production.

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S. Zele et al. Solar Energy 269 (2024) 112338

Table 1 demonstrate circular economy through industrial symbiosis. Seques­

Composition of typical c-Si solar PV waste [14]. tering this large volume of waste in concrete will further help in
Component Weight Percent % conserving a fast-depleting resource, sand.
In our study, field-used, discarded and EoL waste solar panels were
Glass 70.00
Aluminium Frame 18.00 crushed to produce fine aggregates. Physical and chemical character­
Polymers: EVA, PVDF, PET 6.60 ization tests were conducted on these fine aggregates, to assess its
(Encapsulant & Backsheet) suitability as sand replacement in concrete. Further, concrete cubes
Solar Cells: Si 3.65 were cast using standard process and replacing regular sand with solar
Metallization on cells: Ag 0.053
Cables 1.00
waste sand to study the mechanical behaviour.
Other internal cables and metals 0.693
(Cu, Al, Sn, Pb) 2. Materials

2.1. Solar panel waste sand (SWS) preparation

The possibility of using various types of waste glass as a replacement of
sand in concrete has been explored by researchers across the globe [23].
To prepare the solar waste sand, we collected 10 discarded field-used
Most studies indicate that the waste glass can be a good replacement for
200 Wp c-Si solar panels. Fig. 2 shows the process flow for preparation of
aggregates and/or cement in concrete [24–29]. Solar PV waste largely
sand from solar panel waste. The junction boxes and cables attached to
consists of waste glass with small fractions of mixed metals and polymers
the panels were removed manually and external aluminium frames from
as shown in Table 1. However, this new method of using crushed solar
the panels were separated mechanically using a customized tool. The
waste as a sand replacement in concrete has not been investigated
preparation of SWS was carried out with support from Threco Recycling
before. This recycling approach will eliminate the need for high energy
LLP, an electronic waste recycling company based in Khopoli, India.
and cost intensive steps like pyrolysis and combustion. By promoting the
Fig. 3 shows the various stages in preparation of Solar panel Waste Sand.
usage of solar panel waste in concrete, the construction industry will
The laminates were shredded (Compression cutter, 0.75 hp motor) into

Fig. 2. Process Flowchart for preparing Solar panel Waste Sand (SWS).

Fig. 3. Preparation of Solar panel Waste Sand (SWS): a) Waste Solar Panels b) Laminates ready for crushing c) Polymer flock separated d) SWS used for casting
concrete cube.

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S. Zele et al. Solar Energy 269 (2024) 112338

small strips and then passed through a scrap granulator (Shredder with 5 screw-topped glass jar. The jar is rotated at a speed of 80 rpm for 15 min.
hp motor) using 0.048 kWh/ kg for preparation of SWS. Visual inspec­ The suspension is allowed to settle, and residue is washed multiple times
tion of the crushed materials showed largest chunks (>4.75 mm) were until a 1000 mL cylinder is filled. Next, the contents of 1000 mL cylinder
mainly polymer flocks with small fractions of metals and glass are oven dried to a constant weight at 110 0C. The silt content of SWS is
embedded in it. The middle size groups were mainly glass and finest size calculated using Eq. (2).
group contained mostly metals. The mixed crush was manually sieved ( )
100 1000ws
for further particle size segregation. Percentage of Silt = − 0.8 (2)
w1 V

3. Experimental methodology where w1 is the weight of the original sample in g, ws is the weight of
dried residue in g and V is the volume of pipette in mL.
Concrete is a composite material produced by mixing fine aggregates
(sand), coarse aggregates, cement, admixtures, and water in predefined
proportions. The products of hydration reaction between cement and 3.3. Water absorptivity and specific gravity of SWS
water bind the coarse aggregates, fine aggregates in a dense matrix of­
fering strength as well as stiffness to the hardened concrete. Fine ag­ 3.3.1. Context
gregates offer the requisite surface area for deposition of the hydration Water absorption of fine aggregates influences the water available
products thereby ensuring even load distribution on the entire matrix. for hydration reaction in concrete wet mix. The specific gravity of SWS
Moreover, the sand being inert, does not interact chemically in hydra­ impacts the weight (density) of concrete.
tion reaction. This paper explores the possibility of replacing sand with
SWS. The following subsections detail the various experimental tests (for 3.3.2. Experimental procedure [34]
fine aggregates) that are performed on SWS as per the requirements of SWS sample is placed in a tray covered with distilled water at room
relevant codes [31–40]. The experimental tests are described with temperature for 24 h. The entrapped air is removed by agitation with a
respect to their context, procedure, and calculations. rod. The water is drained by decantation through a filter paper. Weight
of saturated sample is then recorded as A. Subsequently, the residue is
placed in a pycnometer, which is filled with distilled water (Weight B).
3.1. Particle size distribution of SWS The contents of pycnometer are then emptied in a tray, oven dried for 24
h and weighed (Weight D). The weight of pycnometer filled with
3.1.1. Context distilled water is recorded as Weight C. The specific gravity, apparent
Particle size gradation of fine aggregates affects quantities of cement, specific gravity and water absorption of SWS are calculated using Eqs.
water, consistency, workability, porosity, shrinkage, and durability of (3––5) respectively.
concrete. Finer sand grading results in lower workability [30], and af­
D
fects the compressive, tensile strength and stiffness [27]. The size Specific Gravity = (3)
(A − (B − C))
gradation and fineness modulus of the fine aggregates significantly in­
fluence the performance of fresh and hardened concrete [28].
D
Apparent Specific Gravity = (4)
(D − (B − C))
3.1.2. Experimental procedure [32]
The air dried SWS sample is screened through sieves of aperture sizes 100(A − D)
4.75 mm, 2.36 mm, 1.18 mm, 600 µm, 300 µm, 150 µm, and 75 µm. The Water Absorption(percent of dry weight) = (5)
D
weight of material retained on each sieve is measured on a balance with
least count of 1 mg. The results of this test are reported as the percentage
by weight of the total sample passing one sieve and retained on the next 3.4. Chemical composition of SWS
smaller sieve, to the nearest 0.1 percent in a tabular form. The particle
size distribution is then graphically represented as a curve with aperture The chemical composition of SWS was determined using XRF
size in mm on X axis (in log scale) and percent passing on Y axis. (Wavelength Dispersive X Ray Fluorescence spectrometer - Bruker S8
Additionally, the fineness modulus of the SWS is calculated using Eq. Tiger model).
(1).
3.5. Alkali aggregate reactivity

∑
(Cumulative percentage weight retained on each sieve)
Fineness Modulus = (1)
100

3.5.1. Context
The potential reactivity between silica and alkaline content (origi­
3.2. Silt content of SWS nating from Na2O and K2O) present in cement and other sources needs to
be evaluated for possibility of Alkali Silica Reaction (ASR). ASR can
3.2.1. Context create deleterious effects in concrete since the reaction products are
The proportion of fine particles (smaller than 75 µm) present in a expansive and result in cracking of concrete. In ASR, the alkalis (Na+,
sample of fine aggregates is called the silt content. The silt content in the K+, and OH− ) present in the concrete pore solution react with unstable
fine aggregates affects the compressive strength as well as the cohesion siliceous phases encountered in the aggregates, generating a hygro­
and permeability of concrete. scopic product, the ASR gel. The surrounding water causes the ASR gel
to swell developing tensile stresses, which can lead to cracking of the
3.2.2. Experimental procedure [33] concrete. A network of cracks can begin to form as the ASR-induced
Air dried SWS sample and sodium oxalate solution are placed in a cracks propagate from the aggregate particles into the cement paste.

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S. Zele et al. Solar Energy 269 (2024) 112338

20N(V3 − V2 )
Rc = × 1000 (7)
V1

where Rc is the reduction in alkalinity in mmoles/L; N is normality of the

HCl used for the titration; V1 is the volume in mL of dilute solution; V2 is
the volume of HCl in mL used to attain the phenolphthalein end point in
the test sample; V3 is the volume of HCl in mL used to attain the
phenolphthalein end point in the blank.
Step 2: Accelerated Mortar Bar Expansion Test
In step 2, an accelerated mortar bar test is performed [37]. In this
test, SWS is graded as per the requirements and mixed with cement to
Fig. 4. Mortar Bar with 100% replacement of sand with SWS. obtain a dry mix ratio of 1 part of cement and 2.25 parts of SWS. Mortar
is then prepared by adding water (water to cement ratio 0.47 by mass) to
the dry mix. The mortar is then placed in bar moulds and kept in moist
This can further accelerate the reaction by ingress of water and alkalis
cabinets for 24 h. After de-moulding (as shown in Fig. 4), the bars are
through the cracks [31].
placed in an oven maintained at 80 0C. Initial length of the bars is then
measured after 24 h. The mortar bars are then returned to the oven
3.5.2. Experimental procedure [35,36,37]
maintained at 80 0C by immersing in 1 N NaOH solution. Subsequent
The potential alkali aggregate reactivity is determined in two steps.
length measurements are then taken till the 16th day. Average expan­
First, the dissolved silica and reduction in alkalinity values are obtained
sion value is then calculated.
to check whether the fine aggregates are innocuous or potentially
deleterious. If the material is found to be potentially deleterious, a
3.6. Determination of chloride and sulphate content
second confirmatory test (Accelerated Mortar Bar Expansion Test) is
carried out.
3.6.1. Context
Step 1: Determination of Dissolved Silica and Reduction in
One of the main concerns in reinforced concrete is the chloride-
Alkalinity
induced corrosion. Concrete being highly alkaline, acts as a barrier to
SWS is pre-processed by crushing, sieving, and immersing in 1 N
steel corrosion. However, the presence of chlorides can initiate the steel
caustic soda solution. This solution along with the blank is placed in a
corrosion reaction. Rust, formed by corrosion of steel occupies a larger
liquid bath maintained at 80 0C for 24 h. The contents are filtered and
volume than the original steel. As a result, the concrete cover to the
diluted. This sample is further used for determination of dissolved silica
reinforcement starts staining, cracking, and spalling. Sources of chloride
and reduction in alkalinity.
ions can be internal or external. The extent of chloride penetration de­
The dissolved silica content is determined using gravimetric method
pends on the thickness of concrete cover and quality of concrete.
by treating the evaporated sample with HCl and drying the filtrate. The
Corrosion by external sources is initiated only when chloride content
dissolved silica content is determined using Eq. (6).
penetrating the concrete is higher than the threshold concentration and
Sc = 3330(W1 − W2 ) (6) it encounters the reinforcement. As against this, internal chlorides
(present in constituents of concrete) are available to initiate corrosion
where Sc is concentration of silica in mmol/L; W1 is weight of silica in when concrete is cast. Hence, it is necessary to check the level of chlo­
grams found in 100 mL of dilute solution; W2 is weight of silica in grams rides in fine aggregates used for concrete production. Sulphate ions
found in blank. present in aggregates react with CaOH and calcium aluminate hydrate to
Reduction in alkalinity is determined using volumetric titration form gypsum and ettringite. This can lead to expansion, cracking,
method by titrating it with 0.05 N HCl using phenolphthalein indicator. strength loss, and disintegration of the concrete. Thus, monitoring sul­
The reduction in alkalinity in mmoles/L is calculated using Eq. (7). phate content in fine aggregates is essential.

Fig. 5. Concrete cube casting: a) Mixing SWS with coarse aggregates and cement b) Concrete cubes with SWS.

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S. Zele et al. Solar Energy 269 (2024) 112338

Table 2 3.7. Determination of total alkali content

Details of concrete dry mix used for compression test.
Test Description of Dry Mix Water: Cement 3.7.1. Context
Mix Ratio High amount of alkali present in aggregates can lead to ASR reaction,
Content and Ratio which can cause cracking within the concrete that poses a threat to
T1 Cement: SWS: 10 mm Coarse Aggregates 0.46 durability. Consequently, estimation of alkalis in SWS in terms of Na2O
1: 1.5: 3 equivalent is essential.
T2 Cement: SWS: 10 mm Coarse Aggregates: 20 mm 0.40
Coarse Aggregates
1: 2.2: 1.1: 1.4
3.7.2. Experimental procedure [39]
The alkali content in SWS is measured as percent Na2O and percent
K2O using flame photometry.
3.6.2. Experimental procedure [38,39]
3.8. Soundness of SWS
3.6.2.1. Chloride content. The chlorides from the crushed aggregate
sample are extracted with hot dilute HNO3. The Chloride concentration 3.8.1. Context
is determined by volumetric titration method by adding 25 mL of 0.2 N The resistance of aggregates to disintegration due to weathering and
AgNO3 solution. Excess AgNO3 is then titrated with 0.02 N ammonium freeze–thaw cycles is determined through the soundness test. The
thiocyanate solution until a permanent faint reddish brown colour ap­ degradation and potential failure of concrete can be prevented by using
pears. The volume of ammonium thiocyanate is recorded as Y mL. The aggregates that are durable (resistant to weathering).
Chloride percentage is calculated using Eq. (8).
3.8.2. Experimental procedure [40]
Chloride, percent = 0.00142(25 − Y) (8)
In this test, SWS is thoroughly washed over 300 µm sieve and dried to
a constant weight at 110 0C. Then the SWS is sieved through sieves of
3.6.2.2. Sulphate content. The sulphate concentration is measured different aperture sizes to obtain 100 g each of five size groups between
gravimetrically by an acid extraction process through precipitation of 300 µm and 4.75 mm. The samples of each group are immersed in
the sulphate as BaSO4 by adding BaCl2 solution. The BaSO4 precipitate is Na2SO4 solution for 16 h at room temperature and then oven dried. Five
filtered and then ignited at 800 0C. The cooled residue is weighed (W). such cycles of drying and immersion are carried out. The average loss of
The percentage of sulphate is obtained using Eq. (9). mass in each group is reported.
Sulphate, percent = 34.3W (9)

Table 3
Particle Size Distribution of SWS and NRS.
Material % Finer Fineness Modulus

4.75 mm 2.36 mm 1.18 mm 600 μm 300 μm 150 μm 75 μm

SWS 100 51.81 37.62 25.56 12.44 5.44 0 3.18

NRS 89 72 38 21 6 2 0 3.72
Zone I 90–100 60–95 30–70 15–34 5–20 0–10 – 2.71–4
Zone II 90–100 75–100 55–90 35–59 8–30 0–10 – 2.1–3.37

Fig. 6. Particle Size Distribution of SWS.

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S. Zele et al. Solar Energy 269 (2024) 112338

Table 4 soundness test is well below the prescribed limit for fine aggregates to be
Physical Characterization of SWS. used in concrete.
Property Requirement per IS Code Result Test Method The mean compressive strength of concrete with SWS is 20.68 MPa.
Reference The target mean compressive strength of M15 grade concrete is 15 +
Silt Content Below 3 % 6.67 % [33] (1.65 × 3.5) = 20.775 MPa [41]. The compressive strength and strength
Water Upto 5 % 0% [34] gain rate obtained for the test mixes of concrete using SWS as total sand
Absorptivity replacement display close correlation with that of M15 conventional
Specific Gravity 2.1–3.2 2.11 [34] concrete, as seen in Fig. 7.
All the results from our comprehensive testing of SWS clearly
3.9. Mechanical behaviour establish the suitability of SWS to be used as sand replacement in
concrete.
The acceptance criteria of concrete involve attaining desired
compressive strength [40]. Therefore, in this work, concrete cubes of
150 mm side with SWS as total replacement of sand are cast as shown in
Fig. 5. Two dry mix test sets (T1 and T 2) are developed as shown in
Table 2 to prepare concrete cubes with combination of aggregates.
Water to Cement ratio is chosen such that produced concrete is suitable Table 6
for casting the cubes. Three test specimens of each set were prepared for Chemical Characterization for reactivity of SWS in concrete.
testing the 3, 7 and 28 day’s compressive strength. Property Requirement per IS Results Test Method
383:2016 Reference

4. Results and discussion Alkali as Sodium N/A 0.07 [39]

Oxide (%)
Alkali as Potassium 0.01
This section presents results of the experimental tests carried out to
Oxide (%)
investigate the physical and chemical properties of SWS to determine its Total Alkali Content 0.3 0.08
suitability for using in concrete production. (%)
Table 3 shows the size fractions present in SWS as compared to Dissolved Sillica N/A 509.49 [35]
Natural River Sand (NRS). The range of percentages of various size (mmol / L)
Reduction in N/A 15.0 [36]
fractions in Zone I and Zone II sands as per Indian Standard have been Alkalinity (mmol /
included in the table for ready comparison. Moreover, the fineness L)
modulus of SWS, NRS and Zone I, Zone II sands are included. The par­ Alkali Aggregate If deleterious, check Deleterious [37]
ticle size distribution curve obtained for SWS is shown in Fig. 6 along Reactivity mortar bar expansion
Mortar Bar Expansion 0.1 0.03 [37]
with Zone I and Zone II sand. The physical characterization, chemical
(% Accelerated)
composition, and chemical characterization for reactivity of SWS are Chloride Content (%) Upto 0.04 0.007 [38]
listed in Table 4, Table 5, and Table 6 respectively. Sulphate Content (%) Upto 0.5 0.05 [39]
The behaviour of concrete with SWS under uniaxial compression at Soundness Test (% <10 2.67 [40]
curing age of 3, 7 and 28 days is shown in Fig. 7. loss by Na2SO4)

The comprehensive testing of fine aggregates prepared from solar

panel waste (SWS) shows that the SWS lies mostly within Zone I and
Zone II particle size distribution. Sands with particle size distribution
lying within Zone I to Zone IV are considered suitable for concrete.
Fineness modulus of SWS is 3.18, which falls within the range of Zone I
sand (2.71 – 4). The particle size distribution of SWS falls slightly outside
Zone I sand for a small range of particle sizes. Despite this marginal
deviation, the SWS is suitable to be employed in concrete as sand
replacement because the fineness modulus is within the range of Zone I.
The silt content of SWS is higher than the limiting value [36]. This ne­
cessitates removing some of the silt fraction from SWS prior to its use in
concrete. The water absorption and specific gravity of the SWS are
within the range [36] for fine aggregates to be used in concrete.
The dissolved silica and reduction in alkalinity values of the SWS
indicate that it is a potentially deleterious material. However, the
accelerated mortar bar test shows that the expansion of the mortar
containing SWS is well below the prescribed norms. This demonstrates
that ASR phenomenon will not significantly affect the performance of
concrete with SWS as sand replacement. Thus, it is possible to use SWS
as replacement of sand in concrete.
The chloride content and sulphate content of SWS are well below the
prescribed limits [36] for fine aggregates to be used in concrete. The Fig. 7. Compressive strength gain of concrete with SWS as total sand
percentage loss of mass in various size fractions of SWS as obtained in replacement.

Table 5
Chemical composition (weight %) of SWS.
SiO2 Na2O CaO Al2O3 MgO SO3 Fe2O3 TiO2 Mn2O3 K2O NiO ZrO2

70.1 12.98 9.05 3.37 2.94 0.27 0.16 0.12 0.06 0.03 0.02 0.02

7
S. Zele et al. Solar Energy 269 (2024) 112338

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