scholarly journals Geotechnical Properties and Microstructure of Lime-Fly Ash-Phosphogypsum-Stabilized Soil

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Tebogo Pilgrene Mashifana ◽  
Felix Ndubisi Okonta ◽  
Freeman Ntuli
Keyword(s):  
Fly Ash ◽  
Expansive Soil ◽  
Basic Oxygen Furnace ◽  
Geotechnical Properties ◽  
Magnesium Silicide ◽  
Engineering Properties ◽  
Basic Oxygen ◽  
Basic Oxygen Furnace Slag ◽  
Phosphogypsum Waste ◽  
Furnace Slag

The use of industrial waste as a potential stabilizer of marginal construction materials is cost effective. Phosphogypsum and fly ash are industrial wastes generated in very large quantities and readily available in South Africa. In order to explore the potential stabilization of vastly abundant expansive soil using larger quantity phosphogypsum waste as a potential modifier, composites with a mixture of lime-fly ash-phosphogypsum-basic oxygen furnace slag were developed. However because of the presence of radionuclide, it was necessary to treat the phosphogypsum waste with mild citric acid. The effect of the acid treatment on the geotechnical properties and microstructure of expansive soil stabilized with phosphogypsum-lime-fly ash-basic oxygen furnace slag (PG-LFA-BOF) paste was evaluated, in comparison with the untreated phosphogypsum. Expansive soil stabilized with acid-treated PG-LFA-BOF paste exhibited better geotechnical properties; in particular, the high strength mobilized was associated primarily with the formation of various calcium magnesium silicide and coating by calcium silicate hydrate and calcium aluminate hydrate. The soil microstructure was improved due to the formation of hydration products. The stabilized expansive soil met the specification for road subgrades and subbase. Stabilization of expansive soils with phosphogypsum, fly ash, and basic oxygen fly ash does not only improve engineering properties of soil but also provides a solution in relation to disposal and environmental pollution challenges.

Mechanical Properties and Structure of Fly Ash Modified Basic Oxygen Furnace Slag Based Geopolymer Masonry Blocks

2020 ◽  
Vol 46 (3) ◽  
pp. 372-383
Author(s):  
N.T. Sithole ◽  
F. Okonta ◽  
F. Ntuli
Keyword(s):  
Fly Ash ◽  
Mechanical Performance ◽  
Coal Fly Ash ◽  
Basic Oxygen Furnace ◽  
Curing Temperature ◽  
Basic Oxygen ◽  
Load Bearing ◽  
Minimum Requirement ◽  
Basic Oxygen Furnace Slag ◽  
Furnace Slag

The objective of this research was to investigate the effect of Fly ash as a source of Si and Na on the mechanical performance of the Basic Oxygen Furnace Slag based (BOFS) geopolymer. BOFS has the lowest SiO2, Al2 O3, Na2 O content compared to other aluminosilicate sources (fly ash, metakaolin, granulated blast furnace slag and mine tailings); which have been used to effectively in geopolymer synthesis. SiO2 and Al2 O3, contents of BOFS are respectively 5-7 times and 6-8 times lower than those of fly ash, metakaolin and granulated furnace slag (GBFS). This study evaluated the potential use of fly ash as a source of Si and Al to improve the mechanical performance of a BOFS based geopolymer. The influence of varying amount of Coal Fly Ash (FA) (10–50%) on UCS was studied. The effects of several factors on the UCS of BOFS geopolymer were also investigated. The test variables were molarities of sodium hydroxide (NaOH) (5 M, 10 M and 15 M); the solid to liquid ratio (20 %, 25 % and 30 %); and the curing temperature (20°C, 40°C, 80°C and 100°C). It was established that most favorable conditions for the geopolymer synthesis were FA was 10% of the mixture, 5M NaOH and 80°C curing temperature. Attempts has been made to relate the microstructure of BOFS/FA based composite with properties of geopolymer. Aggregation was identified as the main particulate process as established by the evolution of the particle size distribution (PSD) and its derived moments during the geopolymerisation process. The morphology of the particles appeared flaky and fluffy. The developed composite met the minimum requirement of ASTM C34-13 for a structural clay load bearing non exposed masonry and load bearing exposed side construction masonry.

Basic oxygen furnace slag: Review of current and potential uses

2020 ◽  
Vol 149 ◽  
pp. 106234 ◽  
Author(s):  
Tamlyn Sasha Naidu ◽  
Craig Michael Sheridan ◽  
Lizelle Doreen van Dyk
Keyword(s):  
Basic Oxygen Furnace ◽  
Basic Oxygen ◽  
Basic Oxygen Furnace Slag ◽  
Furnace Slag

scholarly journals Feasibility and Characterization Mortar Blended with High-Amount Basic Oxygen Furnace Slag

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 6 ◽  
Author(s):  
Wei-Ting Lin ◽  
Chia-Jung Tsai ◽  
Jie Chen ◽  
Weidong Liu
Keyword(s):  
Steel Industry ◽  
Setting Time ◽  
Basic Oxygen Furnace ◽  
Cementitious Material ◽  
Partial Replacement ◽  
Supplementary Cementitious Material ◽  
Basic Oxygen ◽  
Basic Oxygen Furnace Slag ◽  
Furnace Slag ◽  
Weight Proportion

Basic oxygen furnace slag (BOFS) was ground to three levels of fineness as a replacement for cement at weight proportions of 10, 30, 50, and 70 wt.%. Fineness and weight proportion were shown to have significant effects on the flowability and setting time of the mortars. The expansion of BOFS mortars increased with an increase in the proportion of cement replaced, thereby exacerbating the effects of cracking. Optimal mechanical properties were achieved when 10 wt.% of the cement was replaced using BOFS with fineness of 10,000 cm2/g. The compressive strength of BOFS mortar is similar to that of ordinary Portland mortar, which makes BOFS suitable for the partial replacement of cement as a supplementary cementitious material. Scanning electron microscopy results revealed that the reaction of CaO with H2O results in the formation of C–S–H colloids, whereas the reaction of SiO2 with Al2O3 produces C–A–S–H colloids. The use of BOFS as a partial replacement for Portland cement could make a tremendous contribution to the steel industry and help to lower CO2 emissions.

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