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Development of lightweight geopolymeric materials using coal fly ash and WastePaper
Author(s)
Nyabanga, Natali Maruva Sharlene
Date Issued
2019
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
The increase in population results in the intensification of coal combustion for power
generation. The exponential population growth in South Africa results in an increase in unused
process by-products such as coal fly ash (CFA) and wastepaper. In power plants, by-products
such as fly ash is extracted from the exhaust gases and disposed to landfills. The demand for
and consumption of paper in daily life is increasing every year, leading to paper disposal
problems. Waste paper has drawn interest from to researchers as a reinforcement material for
geopolymer due to its properties such as lightweight, affordability, availability, and toughness.
Non-load bearing materials are currently manufactured from gypsum and wood, but these
materials are relatively expensive due to the additional costs incurred by the addition of nonflammable
constituents. CFA and waste paper which are currently causing disposal problems
might provide an alternative and cost-effective route to manufacturing non-flammable,
lightweight, low cost and high strength non-load bearing geopolymeric materials. The chief
aim of this study is to develop lightweight, high strength geopolymeric material using waste
materials such as waste paper and CFA. Specifically, the objectives of this study are to evaluate
the compressive strength, weight, tensile strength, water absorption and shrinkage of the
reinforced geopolymer synthesized using different characterization techniques.
In addition, the impact of waste paper on CFA ratio, NaOH molarity and curing temperature
on compressive strength, geopolymer weight, water absorption and shrinkage properties will
be investigated in order to determine the optimum conditions for the synthesis of reinforced
geopolymers. Characterization of the geopolymer by x-ray diffraction, x-ray fluorescence, and
electron microscopy scanning were included in this analysis. This study will lead to the
development of cheap, lightweight, high strength construction material by making use of waste
paper and fly ash which is currently constituting an environmental nuisance. The result of this
research could find application in the construction industries.
No aggregates, sand or cement were used in any of the formulations developed in this study.
Waste paper content was varied from 10 % to 40 %. The optimum waste paper content was
found to be 20 % as the geopolymer weight was 0.856 kg, compressive strength between 3.8
MPa and 4.5 MPa; the water absorbed after 30 minutes of immersion was 0.360 L and the shrinkage percentage was found to be between 18 % and 20 %. The geopolymer product had
a mass varying from 0.91 to 1.2 kg per 100 mm3 and density of 600 - 1000 kg/m3. The operating
cost was calculated, and it was determined that for a 5 000 kg/year production, one
geopolymer costs ZAR 31.70 and at 160 000 kg/year the block costs about ZAR 5.02.
The optimum formulation used consisted of 2.4 kg of CFA, 0.6 kg of WP, 1.80 kg of H20, 0.64
kg of Na2SiO3 and 0.32 kg of NaOH. The mixture was mixed for a total time of 45 minutes and
the hydraulic pressure used for moulding was 5 MPa. The geopolymer was cured for less than
60 hours and aged for 7 days prior to any tests. Partitioning wallboard manufactured using this
formulation weighed 35 kg/m2 and the lightweight brick manufactured weighed 1.1 kg at 220
mm in length, 110 mm in width and 49 mm in depth. It was concluded that the materials can
be used for non-load bearing construction material and should be installed at 1 m above
ground level to avoid moisture absorption from the ground.
generation. The exponential population growth in South Africa results in an increase in unused
process by-products such as coal fly ash (CFA) and wastepaper. In power plants, by-products
such as fly ash is extracted from the exhaust gases and disposed to landfills. The demand for
and consumption of paper in daily life is increasing every year, leading to paper disposal
problems. Waste paper has drawn interest from to researchers as a reinforcement material for
geopolymer due to its properties such as lightweight, affordability, availability, and toughness.
Non-load bearing materials are currently manufactured from gypsum and wood, but these
materials are relatively expensive due to the additional costs incurred by the addition of nonflammable
constituents. CFA and waste paper which are currently causing disposal problems
might provide an alternative and cost-effective route to manufacturing non-flammable,
lightweight, low cost and high strength non-load bearing geopolymeric materials. The chief
aim of this study is to develop lightweight, high strength geopolymeric material using waste
materials such as waste paper and CFA. Specifically, the objectives of this study are to evaluate
the compressive strength, weight, tensile strength, water absorption and shrinkage of the
reinforced geopolymer synthesized using different characterization techniques.
In addition, the impact of waste paper on CFA ratio, NaOH molarity and curing temperature
on compressive strength, geopolymer weight, water absorption and shrinkage properties will
be investigated in order to determine the optimum conditions for the synthesis of reinforced
geopolymers. Characterization of the geopolymer by x-ray diffraction, x-ray fluorescence, and
electron microscopy scanning were included in this analysis. This study will lead to the
development of cheap, lightweight, high strength construction material by making use of waste
paper and fly ash which is currently constituting an environmental nuisance. The result of this
research could find application in the construction industries.
No aggregates, sand or cement were used in any of the formulations developed in this study.
Waste paper content was varied from 10 % to 40 %. The optimum waste paper content was
found to be 20 % as the geopolymer weight was 0.856 kg, compressive strength between 3.8
MPa and 4.5 MPa; the water absorbed after 30 minutes of immersion was 0.360 L and the shrinkage percentage was found to be between 18 % and 20 %. The geopolymer product had
a mass varying from 0.91 to 1.2 kg per 100 mm3 and density of 600 - 1000 kg/m3. The operating
cost was calculated, and it was determined that for a 5 000 kg/year production, one
geopolymer costs ZAR 31.70 and at 160 000 kg/year the block costs about ZAR 5.02.
The optimum formulation used consisted of 2.4 kg of CFA, 0.6 kg of WP, 1.80 kg of H20, 0.64
kg of Na2SiO3 and 0.32 kg of NaOH. The mixture was mixed for a total time of 45 minutes and
the hydraulic pressure used for moulding was 5 MPa. The geopolymer was cured for less than
60 hours and aged for 7 days prior to any tests. Partitioning wallboard manufactured using this
formulation weighed 35 kg/m2 and the lightweight brick manufactured weighed 1.1 kg at 220
mm in length, 110 mm in width and 49 mm in depth. It was concluded that the materials can
be used for non-load bearing construction material and should be installed at 1 m above
ground level to avoid moisture absorption from the ground.
Additional information
Thesis (MEng (Chemical Engineering))--Cape Peninsula University of Technology, 2019
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