1. INTRODUCTION
⌅The
construction industry is generating a large quantity of construction
and demolishing waste in the form of concrete waste which needs to be
properly managed for sustainable development. The application of
concrete waste in the form of recycled aggregate concrete (RAC)
minimizes the requirement of landfills for the demolition waste, and
transportation costs of aggregates by preserving the natural resources,
reclamation lands, and reducing the number of loads headed to landfills (1-61.
McGinnis, M.; Davis, M.; de la Rosa, A.; Weldon, B.D.; Kurama, Y.C.
(2017) Quantified sustainability of recycled concrete aggregates. Mag. Concr. Res. 69 [23], 1203-1211. https://doi.org/10.1680/jmacr.16.00338.
2.
Coelho, A.; De Brito, J. (2012) Influence of construction and
demolition waste management on the environmental impact of buildings. Wast. Manag. 32 [3], 532-541. https://doi.org/10.1016/j.wasman.2011.11.011.
3.
Azúa, G.; González, M.; Arroyo, P.; Kurama, Y. (2019) Recycled coarse
aggregates from precast plant and building demolitions: Environmental
and economic modeling through stochastic simulations. J. Clean. Prod. 210, 1425-1434. https://doi.org/10.1016/j.jclepro.2018.11.049.
4.
Xiao J.; Chunhui, W.; Ding, T.; Akbarnezhad A. (2018) A recycled
aggregate concrete high-rise building: structural performance and
embodied carbon footprint. J. Clean. Prod. 199, 868-81. https://doi.org/10.1016/j.jclepro.2018.07.210.
5. Silva, R.V; De Brito, J.; Dhir, R.K. (2018) Fresh-state performance of recycled aggregate concrete: A review. Construc. Build. Mat. 178, 19-31. https://doi.org/10.1016/j.conbuildmat.2018.05.149.
6.
Ozbakkaloglu, T.; Gholampour, A. (2018) Time-dependent and long-term
mechanical properties of concretes incorporating different grades of
coarse recycled concrete aggregates. Eng. Struct. 157, 224-234. https://doi.org/10.1016/j.engstruct.2017.12.015.
).
Furthermore, the production of cement is increasing to meet the demand
for concrete construction resulting in high carbon dioxide emissions.
The impact of cement on the environment can be minimized by partially
replacing it with fly ash. Additionally, a large portion of industrial
and municipal wastewater is discharged into rivers and landfill sites.
The environmental regulating agencies are following strict guidelines
and denying a municipal landfill near cities. These agencies are
enforcing pressure to identify an alternative way of disposal at a fair
price. The rapid development in population and the increase in economic
developments raised the demand for freshwater. Concrete requires one
trillion gallons of water annually which is the second largest used
material after water (77.
More, A.B.; Ghodake, R.B.; Nimbalkar, H.N.; Chandake, P.P., Maniyar,
S.P.; Narute, Y.D. (2014) Reuse of treated domestic wastewater in
concrete - a sustainable approach. Ind. J. of Appl. Res. 4 [4], 182 - 184. Retrieved from https://www.worldwidejournals.com/indian-journal-of-applied-research-(IJAR)/article/reuse-of-treated-domestic-waste-water-in-concrete-andndash-a-sustainable-approach/MzU0MA==/?is=1.
).
Hence, the use of freshwater in construction industries and other
sectors must be reduced to build an equilibrium between the demand and
supply of freshwater (88.
Al-Jabri, K.S.; Al-Saidy, A.H.; Taha, R; Al-Kemyani, A.J. (2011) Effect
of using wastewater on the properties of high strength concrete. Proc. Eng. 14, 370-376. https://doi.org/10.1016/j.proeng.2011.07.046.
). The half population of the world will be faced with a shortage of freshwater by 2025 (99.
Nishida, T.; Otsuki, N.; Ohara, H.; Garba, Z.; Nagata, T. (2013) Some
considerations for the applicability of sea water as mixing water in
concrete. In: 3rd Inter. Conf. Sust. Const. Mat. Tech., Japan. Retrieved
from http://www.claisse.info/2013%20papers/data/e056.pdf.
).
Researchers are emphasizing to reuse of wastewater, especially in
concrete production. The wastewater can be used in the construction of
concrete to minimize the high cost of its management (1010.
Hassani, M.S.; Asadollahfardi, G.; Saghravani, S.F.; Jafari, S.;
Peighambarzadeh, F.S. (2020) The difference in chloride ion diffusion
coefficient of concrete made with drinking water and wastewater. Construc. Build. Mat. 231, 117182. https://doi.org/10.1016/j.conbuildmat.2019.117182.
).
It was concluded that RAC-produced concrete exhibits inferior characteristics as compared to traditional concrete (55. Silva, R.V; De Brito, J.; Dhir, R.K. (2018) Fresh-state performance of recycled aggregate concrete: A review. Construc. Build. Mat. 178, 19-31. https://doi.org/10.1016/j.conbuildmat.2018.05.149.
, 11-1411.
Verian, K.P.; Ashraf, W.; Cao, Y. (2018) Properties of recycled
concrete aggregate and their influence in new concrete production. Res. Cons. Rec. 133, 30-49. https://doi.org/10.1016/j.resconrec.2018.02.005.
12.
Kisku, N.; Joshi, H.; Ansari, M.; Panda, S.K.; Nayak, S.; Dutta, S.C.
(2017) A critical review and assessment for usage of recycled aggregate
as sustainable construction material. Construc. Build. Mat. 131, 721-740. https://doi.org/10.1016/j.conbuildmat.2016.11.029.
13. Xiao, J.; Li, W.; Fan, Y.; Huang, X. (2012) An overview of study on recycled aggregate concrete in China (1996-2011). Construc. Build. Mat. 31, 364-383. https://doi.org/10.1016/j.conbuildmat.2011.12.074.
14.
González-Taboada, I.; González-Fonteboa, B.; Martínez-Abella, F.;
Carro-López, D. (2016) Study of recycled concrete aggregate quality and
its relationship with recycled concrete compressive strength using
database analysis. Mater. Construcc. 66 [323], e089. https://doi.org/10.3989/mc.2016.06415.
).
Some findings indicate that when recycled coarse aggregate (RCA) is
used as a substitute to natural coarse aggregate (NCA) then the
compressive strength of concrete is reduced between 20 to 30% (15-1715. McNeil, K.; Kang, T.H.-K. (2013) Recycled concrete aggregates: A review. Int. J. Conc. Struc. Mat. 7, 61-69. https://doi.org/10.1007/s40069-013-0032-5.
16. Rahal, K. (2007) Mechanical properties of concrete with recycled coarse aggregate. Buil. Env. 42 [1], 407-415. https://doi.org/10.1016/j.buildenv.2005.07.033.
17. Dabhade, A.; Choudhari, S.; Gajbhiye, A. (2012) Performance evaluation of recycled aggregate used in concrete. Int. J. Eng. Res. App. 2 [4], 1387-1391.
).
Besides, the compressive strength is reduced by 20 to 25% when NCA is
fully replaced with RCA by holding the quantity of cement and W/C ratio
constant (1818.
Etxeberria, M.; Vázquez, E.; Marí, A.; Barra, M. (2007) Influence of
amount of recycled coarse aggregates and production process on
properties of recycled aggregate concrete. Cem. Conc. Res. 37 [5], 735-742. https://doi.org/10.1016/j.cemconres.2007.02.002.
).
When RCA is collected from different resources, the difference in
compressive strength is more pronounced due to the variance of aggregate
properties (18-2518.
Etxeberria, M.; Vázquez, E.; Marí, A.; Barra, M. (2007) Influence of
amount of recycled coarse aggregates and production process on
properties of recycled aggregate concrete. Cem. Conc. Res. 37 [5], 735-742. https://doi.org/10.1016/j.cemconres.2007.02.002.
19. Mukharjee, B.B.; Barai, S.V. (2014) Influence of nano-silica on the properties of recycled aggregate concrete. Construc. Build. Mat. 55, 29-37. https://doi.org/10.1016/j.conbuildmat.2014.01.003.
20.
Li, W.; Xiao, J.; Sun, Z.; Kawashima, S.; Shah, S.P. (2012) Interfacial
transition zones in recycled aggregate concrete with different mixing
approaches. Construc. Build. Mat. 35, 1045-1055. https://doi.org/10.1016/j.conbuildmat.2012.06.022.
21.
Huda, S.B.; Shahria Alam, M. (2015) Mechanical and freeze-thaw
durability properties of recycled aggregate concrete made with recycled
coarse aggregate. J. Mat. Civ. Eng. 27 [10], 04015003. https://doi.org/10.1061/(ASCE)MT.1943-5533.0001237.
22.
Duan, Z.H.; Poon, C.S. (2014) Properties of recycled aggregate concrete
made with recycled aggregates with different amounts of old adhered
mortars. Mat. Des. 58, 19-29. https://doi.org/10.1016/j.matdes.2014.01.044.
23.
González-Fonteboa, B.; Seara-Paz, S.; De Brito, J.; González-Taboada,
I.; Martínez-Abella, F.; Vasco-Silva, R. (2018) Recycled concrete with
coarse recycled aggregate. An overview and analysis. Mater. Construcc. 68 [330], e151. https://doi.org/10.3989/mc.2018.13317.
24.
Rattanachu, P; Karntong, I; Tangchirapat, W; Jaturapitakkul, C;
Chindaprasirt, P. (2018) Influence of bagasse ash and recycled concrete
aggregate on hardened properties of high-strength concrete. Mater. Construcc. 68 [330], e158. https://doi.org/10.3989/mc.2018.04717.
25.
Sánchez Roldán, Z.; Valverde Palacios, I.; Valverde Espinosa, I.;
Martín-Morales, M. (2020) Microstructural analysis of concretes
manufactured with recycled coarse aggregates pre-soaked using different
methods. Mater. Construcc. 70 [339], e228. https://doi.org/10.3989/mc.2020.16919.
).
The mortar stuck with coarse aggregate often compromises the strength
properties of recycled aggregate concrete (RAC). If 34% mortar is stuck
to an aggregate of size 10 to 20 mm then the compressive strength of RAC
is reduced up to 10% (2222.
Duan, Z.H.; Poon, C.S. (2014) Properties of recycled aggregate concrete
made with recycled aggregates with different amounts of old adhered
mortars. Mat. Des. 58, 19-29. https://doi.org/10.1016/j.matdes.2014.01.044.
).
In the first 180 days, concrete produced with biologically treated
wastewater reported a 17% improvement in compressive strength.
Afterward, axial strength in the case of secondary treated wastewater
tends to decrease by approximately 18% relative to primary treated
wastewater. However, the water absorption is higher, when secondary
treated wastewater is used in concrete production (2626. Shekarchi, M.; Yazdian, M.; Mehrdadi, N. (2012) Use of biologically treated domestic waste water in concrete. Kuw. Jour. Sci. Eng. 39 [2B], 97 - 111. Retrieved from http://apc.ku.edu.kw/jer/files/30Jan20131206585-use%20of.pdf.
).
After examining the behavior of concrete fabricated with cementitious wash water, Asadollahfardi et al. (2727.
Asadollahfardi, G.; Asadi, M.; Jafari, H.; Moradi, A.; Asadolllahfardi,
R. (2015) Experimental and statistical studies of using wash water from
ready-mix concrete trucks and a batching plant in the production of
fresh concrete. Constr. Build. Mater. 98, 305-314. https://doi.org/10.1016/j.conbuildmat.2015.08.053.
)
reported that cement wash water can be successfully used for the
production of good quality fresh concrete. Experimental results showed
that concrete fabricated with cement wash water or a mixture of it and
clean water was performed better as compared to that concrete developed
with silica and water admixture (2828.
Asadollahfardi, G.; Tahmasabi, G.; Nabi, S.M.; Pouresfandyani, H.;
Hossieni, S.A.A. (2017) Effects of using concrete wash water on a few
characteristics of new concrete. Envir. Eng. Manag. J. 16 [7], 1569-1575.
). Another research conducted by Wasserman (2929. Wasserman, B. (2012) Wash water with the mix: effects on the compressive strength of concrete. Int. J. Constr. Ed. Res. 8 [4], 301-316. https://doi.org/10.1080/15578771.2011.633974.
)
found that the compressive strength of concrete enhanced when
cementitious washout water is used in concrete production as compared to
traditional concrete. The compression performance of concrete was
explored by using three kinds of wastewater such as sewage water,
groundwater, and potable water, Nikhil et al. (3030.
Nikhil, T.R.; Sushma, R.; Gopinath, S.M.; Shanthappa, B.C. (2014)
Impact of water quality on strength properties of concrete. Indian J. Appl. Res. 3 [7], 197-199. Retrieved from https://www.worldwidejournals.com/indian-journal-of-applied-research-(IJAR)/article/impact-of-water-quality-on-strength-properties-of-concrete/NDI0OA==/?is=1&b1=225&k=57.
) deduced that concrete showed maximum compressive strength when drinking water used. Rabie et al. (3131.
Rabie, G.; Hisham A.E.; Rozaik, E.H. (2019) Influence of using dry and
wet wastewater sludge in concrete mix on its physical and mechanical
properties. Ain Sham. Eng. J. 10 [4], 705-712. https://doi.org/10.1016/j.asej.2019.07.008.
)
performed an experimental study on mechanical properties of concrete
developed by using wet and dry sewage sludge observed that there was a
minor difference in compressive strength values by replacing cement
content with wastewater sludge at 5%, 10%, and 15% (by weight of cement
content), but compressive strength beyond that percentage tends to
decrease by 61.6% and 68.5%, correspondingly. Roychand et al. (3232.
Roychand, R.; Pramanik. B.K.; Zhang, G.; Setunge S. (2020) Recycling
steel slag from municipal wastewater treatment plants into concrete
applications - A step towards circular economy. Res. Cons. Rec. 152, 104533. https://doi.org/10.1016/j.resconrec.2019.104533.
)
investigated the mechanical performance of concrete developed by using
steel slag collected from civic wastewater effluent plant and reported
that after substituting the coarse aggregate with steel slag aggregate,
the compressive capacity increased by 18% and 16.8% at 7 and 28-days
curing, correspondingly. Research conducted by Saxena and Tembhurkar (3333.
Saxena, S.; Tembhurkar, A.R. (2019) Developing biotechnological
technique for reuse of wastewater and steel slag in bio-concrete. J. Clean. Prod. 229, 193-202. https://doi.org/10.1016/j.jclepro.2019.04.363.
)
reported that bio- concrete showed a decline in its properties by
incorporating wastewater and steel slag which can be fixed by using
microbiologically induced CaCO3. The tensile and compressive strength of bio-concrete was increased by 12.5% and 31.1% due to its reduced water absorption.
Many studies explore the performance of RAC with fly ash (34-4034.
Kou, S.; Poon, C.; Agrela, F. (2011) Comparisons of natural and
recycled aggregate concretes prepared with the addition of different
mineral admixtures. Cem. Conc. Comp. 33 [8], 788-795. https://doi.org/10.1016/j.cemconcomp.2011.05.009.
35.
Kurda, R, de Brito, J.; Silvestre, J.D. (2019) Water absorption and
electrical resistivity of concrete with recycled concrete aggregates and
fly ash. Cem. Conc. Comp. 95, 169-182. https://doi.org/10.1016/j.cemconcomp.2018.10.004.
36.
Kurda, R.; de Brito, J.; Silvestre, J.D. (2017) Influence of recycled
aggregates and high contents of fly ash on concrete fresh properties. Cem. Conc. Comp. 84, 198-213. https://doi.org/10.1016/j.cemconcomp.2017.09.009.
37.
Kurda, R.; de Brito, J.; J.D. Silvestre, (2018) Indirect evaluation of
the compressive strength of recycled aggregate concrete with high fly
ash ratios. Mag. Concr. Res. 70 [4], 204-216. https://doi.org/10.1680/jmacr.17.00216.
38.
Kurda, R; Silvestre, J.D.; de Brito, J; Ahmed, H.(2018) Optimizing
recycled concrete containing high volume of fly ash in terms of the
embodied energy and chloride ion resistance. J. Clean. Prod. 194, 735-750. https://doi.org/10.1016/j.jclepro.2018.05.177.
39.
Rashidian-Dezfouli, H.; Rangaraju, P. (2017) Comparison of strength and
durability characteristics of a geopolymer produced from fly ash,
ground glass fiber and glass powder. Mater. Construcc. 67 [328], e136. https://doi.org/10.3989/mc.2017.05416.
40.
Mis, H.; Güner, E.D.; Güner, H; Gökçe, N. (2020) A study on
industrial-scale waste utilization in construction material production:
the use of fly ash in GRP composite pipe. Mater. Construcc. 70 [340], e234. https://doi.org/10.3989/mc.2020.12719.
).
These investigations depicted that the effect of fly ash in RAC was
superior to that in natural aggregate concrete (NAC). Kurad et al. (4141.
Kurad, R.; Silvestre, J.D.; de Brito, J.; Ahmed, H. (2017) Effect of
incorporation of high volume of recycled concrete aggregates and fly ash
on the strength and global warming potential of concrete. J. Clean. Prod. 166, 485-502. https://doi.org/10.1016/j.jclepro.2017.07.236.
)
studied the effect of replacing NCA with RCA and cement with fly ash.
They concluded that the compressive strength of concrete decreased up to
3% when RCA was 100% replaced with RAC. 30% replacement of cement with
fly ash reduced the strength of concrete up to 4%. Moreover, the
decrease in the compressive strength of concrete for the combined use of
RCA and fly ash was less than their individual use due to the
pozzolanic reaction of fly ash with the adhered cement paste of RCA.
Some studies (3434.
Kou, S.; Poon, C.; Agrela, F. (2011) Comparisons of natural and
recycled aggregate concretes prepared with the addition of different
mineral admixtures. Cem. Conc. Comp. 33 [8], 788-795. https://doi.org/10.1016/j.cemconcomp.2011.05.009.
, 3535.
Kurda, R, de Brito, J.; Silvestre, J.D. (2019) Water absorption and
electrical resistivity of concrete with recycled concrete aggregates and
fly ash. Cem. Conc. Comp. 95, 169-182. https://doi.org/10.1016/j.cemconcomp.2018.10.004.
, 3838.
Kurda, R; Silvestre, J.D.; de Brito, J; Ahmed, H.(2018) Optimizing
recycled concrete containing high volume of fly ash in terms of the
embodied energy and chloride ion resistance. J. Clean. Prod. 194, 735-750. https://doi.org/10.1016/j.jclepro.2018.05.177.
, 4242. Liu, K.; Yan, J.; Zou, C. (2018) Behaviour of recycled aggregate concrete under combined compression and shear stresses. Mater. Construcc. 68 [331], e162. https://doi.org/10.3989/mc.2018.06217.
)
portrayed that the incorporation of fly ash to the RAC presented better
performance as compared with NAC in terms of sorptivity, chloride ion
migration, and water absorption, etc. The addition of glass fibers
improved the compressive, split tensile, and flexural strengths of
concrete due to the enhanced bridging effect of fibers in concrete (43-4843.
Ali, B.; Qureshi, L.A. (2019) Influence of glass fibers on mechanical
and durability performance of concrete with recycled aggregates. Construc. Build. Mat. 228, 116783. https://doi.org/10.1016/j.conbuildmat.2019.116783.
44.
Ali, B.; Qureshi, L.A.; Shah, S.H.A.; Rehman, S.U.; Hussain, I.; Iqbal,
M. (2020) A step towards durable, ductile and sustainable concrete:
Simultaneous incorporation of recycled aggregates, glass fiber and fly
ash. Construc. Build. Mat. 251, 118980. https://doi.org/10.1016/j.conbuildmat.2020.118980.
45.
Koushkbaghi, M.; Kazemi, M.J.; Mosavi, H.; Mohseni, E. (2019) Acid
resistance and durability properties of steel fiber-reinforced concrete
incorporating rice husk ash and recycled aggregate. Construc. Build. Mat. 202, 266-275. https://doi.org/10.1016/j.conbuildmat.2018.12.224.
46.
Santillán, L.R.; Locati, F.; Villagrán-Zaccardi, Y.A.; Zega, C.J.
(2020) Long-term sulfate attack on recycled aggregate concrete immersed
in sodium sulfate solution for 10 years. Mater. Construcc. 70 [337], e212. https://doi.org/10.3989/mc.2020.06319.
47.
Zhang, Y.; Yan, L.; Wang, S.; Xu, M. (2019) Impact of twisting
high-performance polyethylene fibre bundle reinforcements on the
mechanical characteristics of high-strength concrete. Mater. Construcc. 69 [334], e184. https://doi.org/10.3989/mc.2019.01418.
48.
Alberti, M.G.; Enfedaque, A.; Gálvez, J.C.; Picazo, A. (2020) Recent
advances in structural fibre-reinforced concrete focused on
polyolefin-based macro-synthetic fibres. Mater. Construcc. 70 [337], e206. https://doi.org/10.3989/mc.2020.12418.
). Xue et al. (4949.
Xie, J.; Huang, L.; Guo, Y.; Li, Z.; Fang, C.; Li, L.; Wang, J. (2018)
Experimental study on the compressive and flexural behaviour of recycled
aggregate concrete modified with silica fume and fibres. Construc. Build. Mat. 178, 612-623. https://doi.org/10.1016/j.conbuildmat.2018.05.136.
)
explored the bonding behavior between the steel fibers and RAC
manufactured with mineral admixtures (silica fume) and observed an
improvement in the compressive strength of RAC due to a good bond
between steel fibers and RAC. Furthermore, the incorporation of both
silica fume and steel fibers significantly improved the performance of
RAC at elevated temperatures.
1.1. Scope and significance
⌅The contaminated wastewater is producing negative impacts on the natural atmosphere as well as on human health. Therefore, such adverse impacts on the environment and human health could be avoided up to a certain limit by using wastewater in the concrete mix. Furthermore, to overwhelm the low tensile strength of plain concrete and the high carbon footprint of the cement industry, the use of glass fibers and fly ash to concrete is beneficial. In this study, mechanical properties such as compressive strength and split tensile strength as well as durability properties i.e., water absorption, chloride penetration, and resistance against H2SO4 of the recycled aggregate concrete incorporating with fly ash and glass fibers (FGRAC) have been studied under different curing ages by employing six types of wastewater for mixing purpose such as domestic sewage wastewater (DSW), fertilizer factory wastewater (FFW), textile factory wastewater (TFW), sugar factory wastewater (SFW), leather factory wastewater (LFW), and service station wastewater (SSW). One concrete mix was manufactured with potable water without adding glass fibers and fly ash for the comparative analysis. A one-way variance analysis (ANOVA) study was conducted at the five percent significance level to determine the value of discrepancy between the different properties of FGRAC mixes.
2. TESTING PROGRAM
⌅2.1. Materials
⌅Ordinary Portland cement having grade 43 was employed for concrete production as per ASTM C150/C150M (5050.
ASTM-C150/C150M-18, Standard specification for Portland cement, ASTM
International, West Conshohocken, PA. 2018. Retrieved from https://www.astm.org/DATABASE.CART/HISTORICAL/C150C150M-18.htm.
). The physicochemical properties of cement are presented in Table 1.
F type fly ash taken from DIRK Pozzoplast was used in the present
study. The chemical and physical properties of fly ash were reported in Table 1.
The RCA was used by replacing 100% NCA. For this purpose, reinforced
concrete columns and cylinders with ages of 1 to 2 years were crushed
having a compressive strength ranging between 30 MPa and 45 MPa. The
recycled aggregate with a maximum size of 12 mm was obtained. In this
study, Lawrancepur sand was used according to ASTM C33/C33M-18 (5151.
ASTMC33/C33M-18, Standard specification for concrete aggregates, ASTM
International, West Conshohocken, PA. 2018. Retrieved from https://standards.globalspec.com/std/10290845/astm-c33-c33m.
). The physical and chemical properties of sand and RCA are mentioned in Table 2 and the sieves analysis graphs of both materials are presented in Figure 1.
The alkali-resistant glass fibers were employed in the present study
having a tensile strength of 1800 MPa and a specific gravity of 2.65.
Some of the main characteristics of glass fibers were reported in Table 3.
The RAC was manufactured with six various types of wastewater based on
their origins and potable water. The clean water was fully relieved by
each wastewater type. The chemical examination of each type of
wastewater was carefully performed and mentioned in Table 4.
Besides, the chemical properties of wastewater were comprehensively
tested in the Pakistan Council of Research in Water Resources.
Physical properties | Chemical properties | ||||
---|---|---|---|---|---|
Parameter | Cement | Fly ash | Component | Cement | Fly ash |
Consistency (%) (5252.
Bian, J.; Cao, W.; Zhang, Z.; Qiao, Q. (2020) Cyclic loading tests of
thin-walled square steel tube beam-column joint with different joint
details. Structures. 25, 386-397. https://doi.org/10.1016/j.istruc.2020.03.027. ) | 29.2 | 28.6 | SiO2 (%) | 22.3 | 60.4 |
Specific gravity (5353.
Yang, J.; Guo, T.; Chai, S. (2020) Experimental and numerical
investigation on seismic behaviours of beam-column joints of precast
prestressed concrete frame under given corrosion levels. 2020. Structures, 27, 1209-1221. https://doi.org/10.1016/j.istruc.2020.07.007. ) | 3.0 | 2.3 | Al2O3 (%) | 5.7 | 26.7 |
Final setting time (mins) (5454.
Attari, N.; Youcef, Y.S.; Amziane, S. (2019) Seismic performance of
reinforced concrete beam-column joint strengthening by frp sheets. Structures. 20, 353-364. https://doi.org/10.1016/j.istruc.2019.04.007. ) | 235 | - | SO3 (%) | 2.5 | 1.1 |
Initial setting time (mins) (5454.
Attari, N.; Youcef, Y.S.; Amziane, S. (2019) Seismic performance of
reinforced concrete beam-column joint strengthening by frp sheets. Structures. 20, 353-364. https://doi.org/10.1016/j.istruc.2019.04.007. ) | 110 | - | MgO (%) | 5.3 | 0.8 |
Specific surface area (m2/kg) (5555.
Hu, Y.; Zhao, J.; Zhang, D.; Li, Y. (2020) Cyclic performance of
concrete-filled double-skin steel tube frames strengthened with
beam-only-connected composite steel plate shear walls. J. Build. Eng. 31, 101376. https://doi.org/10.1016/j.jobe.2020.101376. ) | 330 | 423 | CaO (%) | 59 | 4.2 |
Fineness (Blaine Test) (cm2/g) | 2770 | 2950 | Fe2O3 (%) | 6.0 | 2.5 |
Compressive strength at 3 days (MPa) (5656.
Won, D.; Lee, J.; Seo, J.; Kang, Y.J.; Kim, S. (2020) Hysteretic
performance of column-footing joints with steel composite hollow RC
columns under cyclic load. J. Build. Eng. 29, 101165. https://doi.org/10.1016/j.jobe.2019.101165. ) | 38.5 | - | Loss of ignition (%) | 2.9 | 4.2 |
Compressive strength at 28-days (MPa) (5656.
Won, D.; Lee, J.; Seo, J.; Kang, Y.J.; Kim, S. (2020) Hysteretic
performance of column-footing joints with steel composite hollow RC
columns under cyclic load. J. Build. Eng. 29, 101165. https://doi.org/10.1016/j.jobe.2019.101165. ) | 42.5 | - | K2O (%) | 0.8 | - |
Soundness (5757.
Xue, Y.; Yang, Y.; Yu, Y. (2020) Pseudostatic testing for load-carrying
capacity of precast concrete-encased steel composite columns. J. Build. Eng. 29, 101189. https://doi.org/10.1016/j.jobe.2020.101189. ) | No expansion | - | Na2O | 0.4% | 1.4 |
Property | Sand | RCA |
---|---|---|
Water absorption after one day (%) | 2.25 | 7.7 |
Fineness modulus | 2.45 | - |
Specific gravity | 2.62 | 2.25 |
Dry density (kg/m3) | 1650 | 1305 |
Maximum size (mm) | 4.75 | 12.0 |
Minimum size (mm) | - | 4.75 |
Parameter | Value | Parameter | Value |
---|---|---|---|
Diameter ( | 15 | Length (mm) | 8-16 |
Melting point (oC) | 1000 | Texture (g/km) | 80 |
Loss on ignition at 900oC (%) | 1.15 | Moisture (%) | 0.4 |
Elastic modulus (GPa) | 70 | Tensile strength (MPa) | 1800 |
Specific gravity | 2.65 | Density (kg/m3) | 890 |
Parameter (unit) | PW | FFW | TFW | SSW | DSW | SFW | LFW |
---|---|---|---|---|---|---|---|
pH value | 7.0 | 2.5 | 7.2 | 6.0 | 7.4 | 7.5 | 6.5 |
TDS (mg/l) | 761.6 | 2138 | 325.6 | 416.5 | 931.6 | 2712.2 | 387 |
TSS (mg/l) | 26.4 | 47.6 | 18.7 | 59.5 | 433.5 | 58.7 | 35.2 |
Turbidity (NTU) | 0.8 | 2.8 | 1.0 | 31.5 | 212.5 | 21.3 | 22.6 |
DO (mg/l) | 5.4 | 2 | 4.5 | 2.2 | 2.4 | 2.6 | 5.3 |
COD (mg/l) | 15.8 | 488.3 | 102 | 1207 | 357.9 | 807.5 | 1075 |
BOD (mg/l) | 10.4 | 518.5 | 59.5 | 952 | 264.4 | 612 | 852 |
Alkalinity (mg/l) | 69.8 | 1.4 | 40.8 | 73.1 | 82.5 | 104.6 | 23.5 |
Conductivity (m-s/cm) | 1.2 | 7.3 | 0.6 | 0.7 | 1.6 | 5.7 | 1.4 |
Bicarbonates (mg/l) | 283.1 | 180 | 10.8 | 297.5 | 340 | 637.5 | 14.3 |
Hardness (mg/l) | 307.7 | 2176 | 290.7 | 314.5 | 612.9 | 1802 | 225.4 |
Sulphate (mg/l) | 6.2 | 807.5 | 89.3 | 98.6 | 641.8 | 178.5 | 74.6 |
Fluoride (mg/l) | 0.3 | 0.1 | 0.6 | 0.1 | 1 | 0.4 | 0.5 |
Nitrate (mg/l) | 1.2 | 56.1 | 2.4 | 8.5 | 86.7 | 27.2 | 2.2 |
Chloride (mg/l) | 10.4 | 892.5 | 53.9 | 212.5 | 289 | 732.7 | 183.4 |
Iron (mg/l) | 1.7 | 3.1 | 0.8 | 1.0 | 0.7 | 1.3 | 1.2 |
2.2. Fabrication and testing of specimens
⌅To achieve an optimal saturation, the RCA was submerged in potable water for 10 minutes (5858.
González, J.G.; Robles, D.R.; Valdés, A.J.; Morán del Pozo, J.M.;
Romero, M. (2013) Influence of moisture states of recycled coarse
aggregates on the slump test. Advan. Mater. Res. Trans. Tech. Publ. 72, 379-383.
).
Seven different types of FGRAC mixes i.e., potable drinking water mix
(PW30-GF-100RCA), domestic sewage wastewater mix (DS30-GF-100RCA),
fertilizer factory wastewater mix (FF30-GF-100RCA), textile factory
wastewater mix (TF30-GF-100RCA), sugar factory wastewater mix
(SF30-GF-100RCA), service station wastewater mix (SS30-GF-100RCA), and
leather factory wastewater mix (LF30-GF-100RCA) were prepared. For
comparative analysis, each of the FGRAC mixes was compared with the
FGRAC mix prepared using potable water (PW) containing fly ash and glass
fibers. The labeling of FGRAC mixes was done in such a way that the
first two letters from the left side indicate the type of wastewater,
the first digit from the left side indicates the percentage of fly ash,
two letters at the middle indicate the addition of glass fibers, the
digit from the right side indicates the 100% replacement of NCA with
RCA, and three letters at the right side indicate recycled aggregate
concrete (RAC).
A total of twenty-one cylindrical specimens (150 mm 300 mm) from each wastewater (constant quantity) were prepared for the determination of compressive strength and splitting tensile strength. Three samples for each wastewater at all ages were prepared and tested. A total of forty-two specimens (50 mm height and 100 mm in diameter) were developed for examining the waster absorption. For the determination of chloride ion migration, forty-two samples (100 mm in diameter and 100 mm in height) were also prepared. Whereas, sixty-three cube samples of size 100 mm were cast to explore the resistance of FGRAC concrete against sulfuric acid attack. The ingredients and quantities utilized for each FGRAC blend as shown in Table 5.
Mix ID | Mixing water | Cement (kg/m3) | Fly ash (kg/m3) | Glass fibers (kg/m3) | RCA (kg/m3) | Sand (kg/m3) | |
---|---|---|---|---|---|---|---|
Type | Content (kg/m3) | ||||||
PW30-GF-100RCA | Potable water | 233 | 466 | 94 | 12 | 1050 | 625 |
DS30-GF-100RCA | Domestic sewage | 233 | 372 | 94 | 12 | 1050 | 625 |
FF30-GF-100RCA | Fertilizer factory | 233 | 372 | 94 | 12 | 1050 | 625 |
TF30-GF-100RCA | Textile factory | 233 | 372 | 94 | 12 | 1050 | 625 |
SF30-GF-100RCA | Sugar factory | 233 | 372 | 94 | 12 | 1050 | 625 |
SS30-GF-100RCA | Service station | 233 | 372 | 94 | 12 | 1050 | 625 |
LF30-GF-100RCA | leather factory | 233 | 372 | 94 | 12 | 1050 | 625 |
A mixer at a speed of 20 revolutions/min (capacity of 0.15 m3)
was used to mix concrete. A total of 10 minutes required for complete
mixing. To achieve a homogenous mixture, the aggregate was mixed with
water, fly ash, and cement in the first 5 minutes then added the
remaining quantity of water and the glass fibers. For each wastewater
mix, a slump test (as per ASTM/C143) was performed and its values
ranging between 90 mm to 105 mm (5959.
Elmesalami, N.; Abed, F.; El Refai, A. (2020) Response of concrete
columns reinforced with longitudinal and transverse BFRP bars under
concentric and eccentric loading. Comp. Struct. 255, 113057. https://doi.org/10.1016/j.compstruct.2020.113057.
). For curing purposes, normal water was used in this study.
The
properties such as compressive strength and split tensile strength for
each RAC blend at different curing ages were tested. The compressive
strength of specimens at 7, 28, and 90-days was tested according to ASTM
C39 (6060. Al Najmi, L.; Abed, F. (2020) Evaluation of FRP bars under compression and their performance in RC columns. Materials. 13 [20], 4541. https://doi.org/10.3390/ma13204541.
). On the other hand, the split tensile strength of specimens at 28 and 90-days was tested as per ASTM C496 (6161.
Tu, J.; Gao, K.; He, L.; Li, X. (2019) Experimental study on the axial
compression performance of GFRP-reinforced concrete square columns. Advan. Struct. Eng. 22 [7], 1554-1565. https://doi.org/10.1177/1369433218817988.
).
The strength properties such as chloride ion migration, water
absorption, and acid attack were tested for all seven FGRAC blends. For
the determination of water absorption, ASTM C1585 (6262.
Chhorn, B.; Jung, W. (2020) Experimental evaluation of the tensile
bonding strength of the basalt fiber-reinforced polymer-concrete
interface. Advan. Struct. Eng. 23 [15], 3323-3334. https://doi.org/10.1177/1369433220934909.
) was followed. All specimens at 28-days were placed at room temperature to find resistance against sulfuric acid (H2SO4) left to dry at 50 C° for 24 hours then immersing them in 4% H2SO4.
To
find out how chloride ion penetrates, the specimens developed have been
cured in water for 28 and 90-days, preceded by oven-drying at a
temperature of 50°C for 24 hours. Following this, the specimens were
cooled to normal temperature and then submerged in a solution of 4% NaCl
for 56 days. The splitting of cylinders procedure was followed as per
the ASTM C496 (6161.
Tu, J.; Gao, K.; He, L.; Li, X. (2019) Experimental study on the axial
compression performance of GFRP-reinforced concrete square columns. Advan. Struct. Eng. 22 [7], 1554-1565. https://doi.org/10.1177/1369433218817988.
) and spraying with a 1N AgNO3 solution into water. When AgNO3 reacts chemically with chloride ions, AgCl is produced giving a silver color.
3. EXPERIMENTAL RESULTS AND DISCUSSIONS
⌅3.1. Compressive strength
⌅In
this current investigation, the compressive strength for each of the
six different FGRAC mixes was tested after 7, 28, and 90-days of curing
as per ASTM C39 (6060. Al Najmi, L.; Abed, F. (2020) Evaluation of FRP bars under compression and their performance in RC columns. Materials. 13 [20], 4541. https://doi.org/10.3390/ma13204541.
). Figure 2
reports the compressive strength of each varying FGRAC mix. Three
developed samples of all RAC blends for each age group were placed
compression test machine then their mean results were calculated.
TF30-GF-100RCA mix recorded the maximum compressive strength while the
DS30-GF-100RCA mix displayed the lowest compressive strength at all the
various testing ages. A control mix (PW30-GF-100RCA) has been developed
to conduct a relative study of the results of different FGRAC mixtures
produced using different kinds of wastewater. At 7-days, the compressive
strength shown by PW30-GF-100RCA was 18.45 MPa. The compressive
strength at 28-days was 26 MPa which was improved by 29% when compared
with the measurement at 7-days. The compressive strength was 31.36 MPa
when checked at 90-days, which was 142% of the compressive strength
observed at 7-days. Thus, the PW30-GF-100RCA mix with the testing age
noted a significant rise in its compressive strength.
The
compressive strength of concrete for the TF30-GF-100RCA mix improved
dramatically when compared with PW30-GF-100RCA at all ages. At 7-days,
the TF30-GF-100RCA blend showed a compressive strength of 22.4 MPa which
was 17.6% higher as compared to the compressive strength of
PW30-GF-100RCA at 7-days. After 28-days, the compressive strength of the
TF30-GF-100RCA mix was increased by 135% having a value of 34.6 MPa
which was 24.8% higher as compared to the compressive strength of the
PW30-GF-100RCA mix. When bicarbonates and fluoride existing in TFW
involves a reaction with Al2O3 remaining in
ordinary Portland cement and thus proceed to calcium fluoroaluminate
formation leading to the increased compressive strength of concrete.
This mineral is extremely toxic, resulting in both fast setting and
early hydration, which improved the performance (3333.
Saxena, S.; Tembhurkar, A.R. (2019) Developing biotechnological
technique for reuse of wastewater and steel slag in bio-concrete. J. Clean. Prod. 229, 193-202. https://doi.org/10.1016/j.jclepro.2019.04.363.
).
The high compressive strength of TF30-GF-100RCA than the control mix
may also be ascribed to the addition of glass fibers and fly ash. Fly
ash reduces the voids between fine particles and form CSH-gel after the
chemical reaction of free CH and fly ash particles. Furthermore, the
glass fibers provided the bridging effects between the particles of the
TF30-GF-100RCA mix to improve the compressive strength.
The improved compressive strengths of FGRAC mixes developed with wastewater could be ascribed to the pozzolanic reactions between free fly ash and CH. Fly ash filled the voids between sand and cement, improved the bond of glass fibers with the binding matrix, and, finally, formed a gel (C-S-H-gel) giving a stronger bond. Furthermore, the ability of glass fibers to prevent the propagation of cracks also improved the compressive strength of FGRAC mixes to give comparable results with the control mix.
By using FFW to produce FGRAC mixes, the compressive
strength attained at 7-days was higher and lesser at 28 and 90-days
associated with PW30-GF-100RCA. At 7-days, the FF30-GF-100RCA mix
exhibited a compressive strength of 21.2 MPa that is 13% higher than the
compressive strength of PW30-GF-100RCA at 7-days. The compressive
strength of the FF30-GF-100RCA mix was increased by 15.6% at 28-days
having a value of 25.2 MPa. It was further decreased by 7.8% at 90-days
when compared with PW30-GF-100RCA but it showed 12.9% higher strength
than at 28-days. This drop in the compressive strength of FF30-GF-100RCA
mix at 28 and 90-days of testing occurred because of an increased
quantity of COD as well as BOD at 5-days in FFW (6363. Mehrdadi, N.; Akbarian, A.; Haghollahi, A. (2009) Using domestic treated wastewater for producing and curing concrete. J. Env. Stud. 35(50): p. 129-136.
).
When DSW has been used for mixing, the compressive strength of concrete decreased considerably. At 7-day testing, the compressive strength was observed 11.9 MPa, at 28-days testing it was 18 MPa, and at 90-day testing, it was 15.3 MPa. The average compressive strengths were 35%, 30%, and 51% lower than the strengths reported in the same order by the PW30-GF-100RCA mix at testing days of 7, 28, and 90. The uniformity of the mixing water has a significant effect on concrete strength. Consequently, the concrete strength for DS30-GF-100RCA is lower than PW30-GF-100RCA. While at 28-days of testing, this strength of the DS30-GF-100RCA mix increased to 34.3% and it shows a reduction of up to 15% at testing days of 90. This reduction in the strength of the DS30-GF-100RCA mix can be due to the existence of many organic matters in DSW that reacts with cement ingredients and thus result in reducing the strength of concrete. Due to the large amount of sulfate found in DSW, the compressive strength of the DS30-GF-100RCA mix is decreased after 90-days of testing.
When SSW was used for mixing, then the
compression capacity of concrete was affected to a slight extent. It had
shown compressive strengths of 16.9 MPa in 7-days, 23.9 MPa in 28-days,
and 29.8 MPa in 90 test days. These compressive strengths were in
similar accordance with that of the PW30-GF-100RCA mix and on average
8.4%, 8%, and 4.8% were lower than compressive strengths displayed by
the PW30-GF-100RCA mix at the testing days of 7, 28, and 90. These
negligible variations indicate that the concrete compressive strength
has no noticeable effect when SSW is used for mixing. The reason is that
SS30-GF-100RCA has shown a decline in strength at all test ages which
can be due to the existence of BOD and COD in excessive amounts. The
concrete compressive strength decreased at 7-days by using SFW
comparison to the PW30-GF-100RCA mix, which subsequently increased to
43.9% after 28-day testing. SF30-GF-100RCA mix has shown increased
strength because of the long setting time of cement paste and the larger
surface area of cement particles (6464. Gao, X.; Yang, Y.; Deng, H. (2011) Utilization of beet molasses as a grinding aid in blended cements. Construc. Build. Mat. 25 [9], 3782-3789. https://doi.org/10.1016/j.conbuildmat.2011.04.041.
).
Compared with the PW30-GF-100RCA mix, the concrete compressive strength
decreased by 5% at 90-days. This drop in the compression capacity can
be due to the availability of C3S in cement triggering the hydration process to delay (6565. Akar, C.; Canbaz, M. (2016) Effect of molasses as an admixture on concrete durability. J. Clean. Prod. 112, 2374-2380. https://doi.org/10.1016/j.jclepro.2015.09.081.
, 6666. Ali, B.; Qureshi L.A. (2019) Durability of recycled aggregate concrete modified with sugarcane molasses. Construc. Build. Mat. 229, 116913. https://doi.org/10.1016/j.conbuildmat.2019.116913.
). Figure 3 represents the comparative strengths of all RAC blends at 7, 28, and 90 test days.
When LFW was used for mixing, then the compression capacity of concrete was affected to a slight extent. It had shown compressive strengths of 16.7 MPa in 7-days, 29.9 MPa in 28-days, and 30.5 MPa in 90 test days. These compressive strengths were in similar accordance with that of the PW30-GF-100RCA mix and on average 9.5%, 3.3%, and 7% lower than compressive strengths displayed by the PW30-GF-100RCA mix at the testing days of 7, 28, and 90. These negligible variations indicate that the concrete compressive strength has no noticeable effect when LFW is used for mixing. The reason is that LF30-GF-100RCA has shown a decline in strength at all test ages that may be associated with a large amount of COD and BOD in LFW. The improved compressive strengths of FGRAC mixes fabricated with wastewater could be ascribed to the pozzolanic reactions between free CH and fly ash. Fly ash filled the voids between sand and cement, improved the bond of glass fibers with the binding matrix, and, finally, formed a gel (CSH-gel) giving a stronger bond. Furthermore, the ability of glass fibers to prevent the propagation of cracks also improved the compressive strength of FGRAC mixes to give comparable results with the control mix.
3.2. Split tensile strength
⌅
Figure 4
demonstrates the split tensile behavior of various FGRAC mixes that
have been manufactured using different wastewater types. The specimens
were tested following ASTM C496 (6161.
Tu, J.; Gao, K.; He, L.; Li, X. (2019) Experimental study on the axial
compression performance of GFRP-reinforced concrete square columns. Advan. Struct. Eng. 22 [7], 1554-1565. https://doi.org/10.1177/1369433218817988.
).
The PW30-GF-100RCA mix displayed an average tensile strength of 2.45
MPa at 7-days, 2.85 MPa at 28-days, and 3.46 MPa at 90-days,
respectively indicating that the PW30-GF-100RCA mix displayed a split
tensile strength of 117% at 90-days compared to its strength at 28-days.
The TF30-GF-100RCA mix showed significantly higher split tensile
strength whereas the DS30-GF-100RCA mix showed the lowest strength. The
TF30-GF-100RCA mix displayed improved split tensile strengths of 2.84
MPa after 7-days, 3.6 MPa after 28-days and 4.1 MPa at 90-days that were
13.7%, 20.8%, and 15.6% greater than the PW30-GF-100RCA mix tested at
various days, respectively. The tensile strength displayed by the
TF30-GF-100RCA mix was greater as the TFW has lesser bicarbonates
amounts relative to other wastewater types. After all, the rise in
bicarbonates contributes to reduced tensile strength (6767.
Reddy, V.V.; Rao, S. (2004) Effects of alkalinity present in water on
strength and setting properties of fly ash concrete. CI-Premier PTE Ltd
Singapore.
). The improved split tensile behavior of
FGRAC mixes may be attributed to the pozzolanic reactions between free
fly ash and CH. Fly ash forms the C-S-H-gel and fills the small voids
between the fine aggregates and binder particles. Furthermore, the
ability of glass fibers to prevent the propagation of cracks and to
produce the bridging effect also improved the split tensile strength of
FGRAC mixes to give comparable results with the control mix
PW30-GF-100RCA.
The
FF30-GF-100RCA mix indicated split tensile strengths of 2.36 MPa at
7-days, 2.68 MPa at 28-days, and 3.17 MPa at 90-days, respectively. This
indicates that the split tensile strengths were reduced by 3.6% at
7-days, by 5.9% at 28-days, and by 8.4% at 90-days associated with the
control mix when FFW was used for mixing. The tensile strengths
demonstrated by the DS30-GF-100RCA mix were small with falls of 8.9% at
7-days, 7% at 28-days, and 9.8% at 90-days as compared with the
PW30-GF-100RCA mix. The SF30-GF-100RCA mix displayed split tensile
strengths of 2.34 MPa at 7-days, 2.71 MPa at 28-days, and 3.29 MPa at
90-days with a reduction of 4.5% at 7-days, 5.0% at 28-days, and 4.8% at
90-days, respectively. The decreases in split tensile strengths
displayed by diverse FGRAC mixes (i.e. FF30-GF-100RCA, DS30-GF-100RCA,
SS30-GF-100RCA, and SF30-GF-100RCA) can be due to the excess of total
suspended solids, COD, and BOD in such kinds of wastewater (6868. Mahasneh, B. (2014) Assessment of replacing wastewater and treated water with tap water in making concrete mix. Elect. J. Geotec. Eng. 19, 2379-2386.
). The concrete displays a reduction in the tensile strength when the volume of chloride increases (6969.
Venkateswara Reddy, V.; Ramana, N.V.; Gnaneswar, K.; Sashidhar, C.
(2011) Effect of magnesium chloride (MgCl2) on ordinary Portland cement
concrete. Ind. J. Sci. Tech. 4 [6], 643-645. Retrieved from https://indjst.org/articles/effect-of-magnesium-chloride-mgcl2-on-ordinary-portland-cement-concrete.
).
This is due to the presence of large quantities of chloride. These
FGRAC mixes have lower pH values. The reduction of the pH value is
responsible for reducing the strength of the split tensile (7070. Kucche, K.J.; Jamkar, S.S.; Sadgir, P.A. (2015) Quality of water for making concrete: A review of literature. Int. J. Sci. Res. Pub. 5 [1], 1-10. Retrieved from http://www.ijsrp.org/research-paper-0115.php?rp=P373551.
).
Figure 5
shows the comparison between the relative percentage of split tensile
strengths produced by various FGRAC mixes and that reported by the
PW30-GF-100RCA mix for different age groups. The LF30-GF-100RCA mix
displayed enhanced split tensile strengths of 2.89 MPa after 7-days, 3
MPa after 28-days, and 3.4 MPa at 90-days that were on average 15.2% and
5.6% greater than the PW30-GF-100RCA mix experienced at 7 and 28-days,
respectively. While this mix presented a 2% lower value of split tensile
strength at 90-days compared with the PW30-GF-100RCA mix. The tensile
strength displayed by the LF30-GF-100RCA mix was greater as the LFW has
lesser bicarbonates amounts relative to other wastewater types because
the rise in bicarbonates results in the reduced tensile behavior of
concrete (6767.
Reddy, V.V.; Rao, S. (2004) Effects of alkalinity present in water on
strength and setting properties of fly ash concrete. CI-Premier PTE Ltd
Singapore.
).
3.3. Water absorption
⌅Being
a durability parameter, the water absorption calculates the number of
pores that are moisture-accessible in concrete. If water absorption is
extreme, it will cause reinforcement corrosion which leads to the
penetration of numerous toxic chemicals and when react with cement
additives thus completely change the characteristics of concrete. Figure 6
indicates the water absorption shown by different RAC blends. Nearly
all the specimens displayed relatively higher water absorption levels.
This may be due to higher water absorption levels for RCA (7.7%). When
the findings were analyzed, they demonstrated that the different types
of wastewater had no significant impact on concrete water absorption as
shown in the literary works (7171.
Asadollahfardi, G.; Delnavaz, M.; Rashnoiee, V.; Ghonabadi, N. (2016)
Use of treated domestic wastewater before chlorination to produce and
cure concrete. Construc. Build. Mat. 105, 253-261. https://doi.org/10.1016/j.conbuildmat.2015.12.039.
).
Different
FGRAC mixes reported a reduction in the properties of water absorption
with time. The water absorption shown by the PW30-GF-100RCA mix was
12.5% at 28-days and 9.2% at 90-days, representing the decline in
moisture content over time. As compared to PW30-GF-100RCA, the water
absorption shown by the TF30-GF-100RCA mix was lower. The moisture
content was 99% at 28-days and 98% at 90-days equated to PW30-GF-100RCA.
The decline in water absorption may be attributed to a reduction in the
amount of chloride, as the volume of chloride rises, the concrete
density lessens with reduced strengths plus enhanced porosity in
concrete (6969.
Venkateswara Reddy, V.; Ramana, N.V.; Gnaneswar, K.; Sashidhar, C.
(2011) Effect of magnesium chloride (MgCl2) on ordinary Portland cement
concrete. Ind. J. Sci. Tech. 4 [6], 643-645. Retrieved from https://indjst.org/articles/effect-of-magnesium-chloride-mgcl2-on-ordinary-portland-cement-concrete.
).
When
tested at 28 and 90-days, correspondingly, the water absorption values
of the FF30-GF-100RCA mix were 9.7% and 16.5% higher than that of
PW30-GF-100RCA. The DS30-GF-100RCA mix displayed moisture content that
is the highest with 14.6% at 28-days, 12% at 90-days that have been
14.7%, and 23.9% higher than with the PW30-GF-100RCA mix. The large
quantities of organic wastewater existing in DSW contribute to the
establishment of large numbers of small pores resulting in higher water
absorption. The water is consumed by such waste during the mixing
process and then emitted during concrete casting, which increases the
ratio of water to cement (W/C) and thus decreases the concrete density (7272.
Seyyedalipour, S.F.; Yousefi Kebria, D.; Dehestani, M. (2015) Effects
of recycled paperboard mill wastes on the properties of non-load-bearing
concrete. Int. J. Enviro. Sci. Tech. 12, 3627-3634. https://doi.org/10.1007/s13762-015-0879-x.
).
When tested at 28 and 90-days correspondingly, the water absorption
values of the SS30-GF-100RCA mix were 8% and 22.8% higher than
PW30-GF-100RCA. Water absorption was enhanced by 11% at 28-days, and by
17% at 90-days while mixing with SFW. While using LFW in the mixing of
concrete, water absorption enhanced by 6.5% and 11.7% at 28 and 90-days,
respectively as related to the control mix. As previous studies have
shown, water absorption has been increased by using various forms of
wastewater in concrete mixes (3333.
Saxena, S.; Tembhurkar, A.R. (2019) Developing biotechnological
technique for reuse of wastewater and steel slag in bio-concrete. J. Clean. Prod. 229, 193-202. https://doi.org/10.1016/j.jclepro.2019.04.363.
).
The reduced water absorptions of FGRAC mixes may be attributed to the
reason that the addition of fly ash helps to reduce the water absorption
of concrete by filling the voids between the fine aggregates and the
binder matrix but the addition of glass fibers and the use of RCA
increases the water absorption due to high water absorption of RCA and
the enhancement in the length of microchannels in the microstructure of
concrete (4444.
Ali, B.; Qureshi, L.A.; Shah, S.H.A.; Rehman, S.U.; Hussain, I.; Iqbal,
M. (2020) A step towards durable, ductile and sustainable concrete:
Simultaneous incorporation of recycled aggregates, glass fiber and fly
ash. Construc. Build. Mat. 251, 118980. https://doi.org/10.1016/j.conbuildmat.2020.118980.
).
3.4. Chloride penetration
⌅In this study, chloride penetration of concrete is studied using 4% NaCl. The method used to calculate this parameter is the penetration of ions color in millimeters penetrated by the chloride ions into the concrete microstructure. Figure 7 indicates the values of chloride ions penetration for all types of FGRAC mixes. The highest chloride penetration values were given by the FFW, which is rich in chloride iron and sulfate ions.
The
control mix portrayed a chloride penetration of 11.87 mm at 28-days,
and 7.45 mm at 90-days. At 28 and 90-days, the TF30-GF-100RCA mix
displayed chloride penetration that was 12.6% higher and 18.9% higher
than PW30-GF-100RCA. This depicts the TF30-GF-100RCA mix as more
vulnerable to oxidation and steel bar corrosion. Also, penetration of
chloride indicated by the FF30-GF-100RCA blend was 14.23 mm in 28-days
and 10.41 mm in 90-days. Chloride ion penetration is also enhanced by
the pretty low pH value of FFW (7070. Kucche, K.J.; Jamkar, S.S.; Sadgir, P.A. (2015) Quality of water for making concrete: A review of literature. Int. J. Sci. Res. Pub. 5 [1], 1-10. Retrieved from http://www.ijsrp.org/research-paper-0115.php?rp=P373551.
).
The increased values of chloride penetration to FGRAC mixes may be
ascribed to the high water absorption of RCA and the addition of glass
fibers causing a balling and bridging effect between the binder matrix
leaving more voids to absorb chloride ions. But the addition of fly ash
is advantageous to resist the penetration of chloride ions by filling
the microstructure of concrete.
Fewer iron quantities in the DSW resulted in the chloride penetration values being close to the control mix. The chloride penetration shown by the SS30-GF-100RCA blend was 13.37 mm and 9 mm at 28- and 90-days, which is 11.2% and 17.2% higher on average than PW30-GF-100RCA values. The SF30-GF-100RCA mix demonstrated chloride penetration values close to those of the SS30-GF-100RCA mix. Similarly, the LF30-GF-100RCA mix depicted higher values of chloride ion penetration (12.24 mm at 28-days and 9.64 mm at 28-days) that were 3% and 22.7% higher than the control mix at 28 and 90-days, respectively. Hence, the chloride ion penetration represented by DSW was the lowest from all forms of wastewater tested, which indicates that it is less prone to corrosion.
3.5. Acid attack resistance
⌅This study examined the mass loss of test samples at 28, 90, and 120-days after soaking them in 4% of the H2SO4 solution. Figure 8 indicates the mass losses caused by each of the FGRAC mixes. The highest degradation was observed by the FF30-GF-100RCA mix.
The
degradation of the TF30-GF-100RCA mix is quicker than the control mix.
TF30-GF-100RCA mix reported mass losses of 6.28% after 28-days, 13.11%
after 90-days, and 16% after 120-days, which were 30.2%, 23.3%, and
15.8% higher than the PW30-GF-100RCA mix. The FF30-GF-100RCA mix
reported mass losses of 7.3% at 28-days, 14.89% at 90-days, and 17.86%
at 120-days that were 40%, 32.5%, and 24.5% higher than the
PW30-GF-100RCA mix. The largest mass loss of the FF30-GF-100RCA mix can
be linked to the lowest pH value (7373.
De Belie, N.; Verselder, H.J.; De Blaere, B.; Van Nieuwenburg, D.;
Verschoore, R. (1996) Influence of the cement type on the resistance of
concrete to feed acids. Cem. Conc. Res. 26 [11], 1717-1725. https://doi.org/10.1016/S0008-8846(96)00155-X.
, 7474.
Pavlik, V.; Unčík, S. (1997) The rate of corrosion of hardened cement
pastes and mortars with additive of silica fume in acids. Cem. Conc. Res. 27 [11], 1731-1745. https://doi.org/10.1016/S0008-8846(97)82702-0.
). Concrete deterioration is thus largely influenced by the pH value of both acid and wastewater mixing (7575.
O’Connell, M.; McNally, C.; Richardson, M.G. (2012) Performance of
concrete incorporating GGBS in aggressive wastewater environments. Construc. Build. Mat. 27 [1], 368-374. https://doi.org/10.1016/j.conbuildmat.2011.07.036.
).
Also, the greater mass loss can be due to the sulfate-rich FFW. The
DS30-GF-100RCA mix exhibited higher degradation in the initial stages,
but the degradation became identical to that of PW30-GF-100RCA at 90 and
120-days. The SF30-GF-100RCA mix displayed mass losses of 5.2% at
28-days, 12% at 90-days, and 15.4% at 120-day testing that were higher
due to the sulfuric acid (H2SO4) invasion. The
mass loss of LF30-GF-100RCA was observed to be 5.2%, 11%, and 14.4% at
28, 90, and 120-days, correspondingly. These mass losses were 15.6%,
9.2%, and 6.1% higher than that of the PW30-GF-100RCA mix. So, we can
say that with the use of all the various forms of wastewater examined,
the degradation of concrete becomes more rapid. Figure 9
records the relative mass losses of diverse concrete mixes at various
testing ages due to an acid attack as compared with the control mix. The
increased values of mass losses of FGRAC mixes may be attributed to the
addition of glass fibers causing a bridging effect between the binder
matrix leaving more voids to absorb chloride ions. But the addition of
fly ash is advantageous to resist the acid attack by filling the
microstructure of concrete.
3.6. Statistical analysis
⌅Tables 6-10Tables 6, 7, 8, 9, 10 demonstrate the ANOVA analysis at a significance level of 5% used to assess the importance of the discrepancies between the various durability properties of the FGRAC mixes at 90-days and the mechanical behavior at 28 testing days. The FGRAC mix was split into six groups of wastewater concrete mixes (TF30-GF-100RCA, FF30-GF-100RCA, DS30-GF-100RCA, SS30-GF-100RCA, SF30-GF-100RCA, and LF30-GF-100RCA) and a control mix PW30-GF-100RCA. A comparison was made between FGRAC mixes and the control mix (PW30-GF-100RCA) to explain the impact of the experimental outputs precisely.
Groups | Counts | Sum | Average | Variance | ||
---|---|---|---|---|---|---|
PW30-GF-100RCA | 3 | 78.1500 | 26.0500 | 66.560643 | ||
DS30-GF-100RCA | 3 | 54.1462 | 18.0487 | 67.912354 | ||
FF30-GF-100RCA | 3 | 75.4650 | 25.1550 | 36.207506 | ||
TF30-GF-100RCA | 3 | 103.927 | 34.6425 | 128.911553 | ||
SF30-GF-100RCA | 3 | 82.0050 | 27.3350 | 72.507675 | ||
SS30-GF-100RCA | 3 | 71.83125 | 23.94375 | 24.922110 | ||
LF30-GF-100RCA | 3 | 75.5950 | 25.198333 | 0.3862583 | ||
ANOVA | ||||||
Source of Variation | SS (Sum of squares) | DOF (Degrees of freedom) | MS (Mean squares) | F | P-value | Fcrit |
Between Groups | 434.72027 | 6 | 72.4533799 | 1.2762036 | 0.3290271 | 2.8477259 |
Within Groups | 794.81621 | 14 | 56.7725864 | |||
Total | 1229.5364 | 20 |
Groups | Counts | Sum | Average | Variance | ||
---|---|---|---|---|---|---|
PW30-GF-100RCA | 3 | 8.535 | 2.845 | 1.6319437 | ||
DS30-GF-100RCA | 3 | 7.957 | 2.652 | 1.3675687 | ||
FF30-GF-100RCA | 3 | 8.040 | 2.680 | 0.973425 | ||
TF30-GF-100RCA | 3 | 10.810 | 3.603 | 1.6917520 | ||
SF30-GF-100RCA | 3 | 8.122 | 2.707 | 1.7310937 | ||
SS30-GF-100RCA | 3 | 8.017 | 2.672 | 1.0766437 | ||
LF30-GF-100RCA | 3 | 9.045 | 3.015 | 1.6688250 | ||
ANOVA | ||||||
Source of Variation | SS (Sum of squares) | DOF (Degrees of freedom) | MS (Mean squares) | F | P-value | Fcrit |
Between Groups | 2.12158214 | 6 | 0.3535970 | 0.24407037 | 0.95387880 | 2.84772599 |
Within Groups | 20.2825041 | 14 | 1.4487502 | |||
Total | 22.4040863 | 20 |
Groups | Counts | Sum | Average | Variance | ||
---|---|---|---|---|---|---|
PW30-GF-100RCA | 3 | 27.585 | 9.195 | 0.863325 | ||
DS30-GF-100RCA | 3 | 36.277 | 12.092 | 2.143481 | ||
FF30-GF-100RCA | 3 | 33.075 | 11.025 | 4.648275 | ||
TF30-GF-100RCA | 3 | 28.5675 | 9.5225 | 3.911643 | ||
SF30-GF-100RCA | 3 | 33.2775 | 11.092 | 0.343743 | ||
SS30-GF-100RCA | 3 | 35.7675 | 11.922 | 0.168882 | ||
LF30-GF-100RCA | 3 | 31.2775 | 10.425 | 2.892077 | ||
ANOVA | ||||||
Source of Variation | SS (Sum of squares) | DOF (Degrees of freedom) | MS (Mean squares) | F | P-value | Fcrit |
Between Groups | 22.199291 | 6 | 3.69988184 | 1.7299067 | 0.18648402 | 2.84772599 |
Within Groups | 29.942854 | 14 | 2.138775298 | |||
Total | 52.142145 | 20 |
Groups | Counts | Sum | Average | Variance | ||
---|---|---|---|---|---|---|
PW30-GF-100RCA | 3 | 22.3545 | 7.4515 | 2.05862475 | ||
DS30-GF-100RCA | 3 | 23.6145 | 7.8715 | 2.26391025 | ||
FF30-GF-100RCA | 3 | 31.2396 | 10.4132 | 2.67804012 | ||
TF30-GF-100RCA | 3 | 27.5709 | 9.1903 | 8.68046907 | ||
SF30-GF-100RCA | 3 | 27.9069 | 9.3023 | 3.35724627 | ||
SS30-GF-100RCA | 3 | 26.9871 | 8.9957 | 0.81108867 | ||
LF30-GF-100RCA | 3 | 28.9069 | 9.6356 | 4.636279603 | ||
PW30-GF-100RCA | 3 | 22.3545 | 7.4515 | 2.05862475 | ||
ANOVA | ||||||
Source of Variation | SS (Sum of squares) | DOF (Degrees of freedom) | MS (Mean squares) | F | P-value | Fcrit |
Between Groups | 18.592055 | 6 | 3.0986758 | 0.88585449 | 0.53040232 | 2.84772599 |
Within Groups | 48.971317 | 14 | 3.4979512 | |||
Total | 67.563372 | 20 |
Groups | Counts | Sum | Average | Variance | ||
---|---|---|---|---|---|---|
PW30-GF-100RCA | 3 | 30.1428 | 10.0476 | 3.12473535 | ||
DS30-GF-100RCA | 3 | 29.3265 | 9.7755 | 4.90601475 | ||
FF30-GF-100RCA | 3 | 44.6775 | 14.8925 | 10.05263175 | ||
TF30-GF-100RCA | 3 | 39.3277 | 13.1092 | 5.591521688 | ||
SF30-GF-100RCA | 3 | 36.1961 | 12.0653 | 7.141446047 | ||
SS30-GF-100RCA | 3 | 39.1807 | 13.0602 | 8.130450563 | ||
LF30-GF-100RCA | 3 | 33.1961 | 11.0653 | 6.490071047 | ||
ANOVA | ||||||
Source of Variation | SS (Sum of squares) | DOF (Degrees of freedom) | MS (Mean squares) | F | P-value | Fcrit |
Between Groups | 61.0771561 | 6 | 10.179526 | 1.56825679 | 0.22813058 | 2.84772599 |
Within Groups | 90.8737424 | 14 | 6.4909816 | |||
Total | 151.950898 | 20 |
The findings of the ANOVA test indicate that different FGRAC mixes did not show a substantial difference at 28-days of testing (P = 32.9% and F ˂ F crit ) between their compressive strengths at 28-days of testing, showing that the types of wastewater tested directly did not influence the compressive strength of FGRAC. On the other hand, for the results of the tensile test, these FGRAC mixes did not display any substantial difference between them (P = 95.4% and F ˂ F crit ), water absorption test (P = 18.64% and F ˂ F crit ), and sulfuric acid attack test (P = 22.8% and F ˂ F crit ). The results of the chloride penetration of different FGRAC mixes have also shown no difference with F ˂ F crit which indicates that the aspects of wastewater explored in FGRAC mixing did not influence the results of the chloride penetration.
The statistical analysis of the durability and mechanical properties of FGRAC mixes portrayed that the compressive and tensile strengths are not influenced by using different types of wastewater examined in the present work. Similarly, no significant differences in the durability properties of FGRAC mixes (water absorption, chloride penetration, and concrete mass loss due to acid attack) were observed. This statistical analysis shows that the examined types of wastewater can be employed for the mixing of concrete without meaningly affecting the mechanical and durability behavior of concrete.
4. CONCLUSIONS
⌅The present study investigates the mechanical and durability behavior of recycled aggregate concrete incorporating with fly ash and glass fibers (FGRAC) manufactured using different categories of wastewater. One concrete mix was fabricated with potable water without adding glass fibers and fly ash for the comparative analysis. A one-way ANOVA test was carried out to study the significance of using different wastewater types, fly ash, and glass fibers on the mechanical and durability behavior of FGRAC mixes. Key points of the present study are reported below.
FGRAC mix made with textile factory wastewater represented the maximum compressive strength of 37.7 MPa at 90-days that was 16.8% higher than the control mix. The addition of fly ash and glass fibers improved the compressive strength of FGRAC mixes by forming a CSH-gel and providing a bridging effect between the binder matrices. Correspondingly, the compressive strengths of FGRAC mixes made with FFW, SSW, SFW, and LFW were 7.8%, 4.8%, 7.7%, and 7% lower than the control mix.
The highest split tensile strength was portrayed by the FGRAC mix made with textile factory wastewater with a value of 4.1 MPa at 90-days that was 15.6% higher than the control mix. Correspondingly, the split tensile strengths of FGRAC mixed manufactured with FFW, SSW, SFW, and LFW were 8.3%, 3.4%, 4.9%, and 2% lower than the tensile strength of the control mix.
The FGRAC mix fabricated with domestic sewage wastewater presented the highest water absorption at 28-days that was 23.9% higher than the water absorption of the control FGRAC mix.
The chloride penetration test portrayed that all the FGRAC mixes presented higher values of chloride ion penetrations than the control mix. Fly ash reduced the chloride penetration by forming a stronger CSH bond, but the addition of glass fibers increased the voids to enhance the chloride penetration.
The attack of FGRAC mixes to 4% solution of H2SO4 reported that all the mixes presented higher values of mass loss as compared with the control mix. The addition of glass fibers caused an enhancement in the air voids increasing mass loss. The FGRAC mix made with fertilizer factory effluent portrayed the highest value of mass loss of concrete that was 32.5% higher than that of the control mix at 120-days.
The statistical study of the testing measurements indicated no significant difference between the various mechanical and durability performance of FGRAC mixes made with different types of effluents.
Finally, it can be concluded that all types of wastewater examined in the present study can be employed for manufacturing the concrete without significantly disturbing the mechanical and durability behavior of concrete directing towards sustainable development by overcoming the carbon footprint and low tensile strength of concrete