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Hm Jafer - One of the best experts on this subject based on the ideXlab platform.
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stabilisation of soft soil using binary blending of high calcium fly ash and palm oil fuel ash
Applied Clay Science, 2018Co-Authors: Hm Jafer, William Atherton, Monower Sadique, Felicite Ruddock, E. LoffillAbstract:Abstract Lime and/or Ordinary Portland cement (OPC) are the traditional Binders used in soft soil stabilisation. However, their manufacture has a negative impact on the environment. This paper reports the results of experimental work for the optimisation of a binary blended Cementitious Binder (BBCB) using two types of fly ash as an alternative for use in soft soil stabilisation. The optimum content of the high calcium fly ash (HCFA) was initially determined along with the effect of grinding activation on the performance of HCFA. Subsequently, the effect of palm oil fuel ash (POFA) pozzolanic reactivity on the engineering properties of soft soil, stabilised with HCFA, was investigated by producing different binary mixtures of HCFA and POFA. Based on the Atterberg limits and unconfined compressive strength (UCS) tests, the combination of POFA with HCFA results in a considerably lower plasticity index (PI) and higher compressive strength than those obtained from the soil treated with HCFA alone. Substantial changes in the microstructure and Binders of the stabilised soil over curing time were evidenced by SEM imaging and XRD analysis. A solid and coherent structure was achieved after treatment with BBCB as evidenced by the formation of C S H, portlandite and ettringite as well as secondary calcite.
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Development of a New Ternary Blended Cementitious Binder Produced from Waste Materials for use in Soft Soil Stabilisation
Journal of Cleaner Production, 2018Co-Authors: Hm Jafer, William Atherton, Monower Sadique, Felicite Ruddock, E. LoffillAbstract:Soil stabilisation using traditional Binders such as Ordinary Portland Cement (OPC), has a serious negative environmental impact, specifically carbon dioxide (CO2) emissions as a result of the manufacture of OPC. Because of this, the use of sustainable Binders has become a critical issue to help reduce cement production through the use of by-product materials. This research seeks to develop a new ternary blended Cementitious Binder (TBCB) to replace cement for soft soil stabilisation. Different ternary mixtures containing wastes i.e., high calcium fly ash (HCFA), palm oil fuel ash (POFA) and rice husk ash (RHA) along with flue gas desulphurisation (FGD) gypsum used as a sulphate activator and grinding agent, were examined. The results illustrate that ternary mixtures improved the engineering and mechanical properties of stabilised soil. The results indicated that the plasticity index (PI) was reduced from 20.2 to 13.0 and the unconfined compressive strength (UCS) increased after 28 days of curing from 202kPa to 944kPa using the optimum non-FGD activated mixture. FGD contributed significantly by increasing the UCS to 1464kPa at 180 days of curing, which surpassed that for the reference cement (1450kPa), and by improving the soil consistency limits; where the PI decreased to 11.7 using TBCB compared with 14.5 for the soil treated with the reference cement. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis revealed substantial changes in the diffraction patterns and microstructure components of the TBCB paste over the curing period, confirming the formation of Cementitious products. A solid, coherent and compacted structure was achieved after treatment with TBCB as evidenced by the formation of C-S-H, CH and ettringite.
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Soft Soil Stabilisation Using a Novel Blended Cementitious Binder Produced From Waste Fly Ashes
2017Co-Authors: Hm JaferAbstract:Soil stabilisation is one of the most common techniques used to mitigate the undesirable properties of soft soils such as low compressive strength and high compressibility. Cement is the most commonly used Binder for soil improvement applications in the UK and worldwide due to its high strength performance. However, its manufacture is energy intensive and expensive, contributing approximately 7% of global carbon dioxide (CO2) emissions. Therefore, the search for alternative raw materials, such as waste and by-products, is becoming critical in order to develop cost effective and more environmentally friendly Binders to replace cement and reduce its negative environmental impact. Blended waste material fly ashes have been identified as promising alternatives to traditional Binders (cement CEM-I) in different construction industries including ground improvement. The reuse of waste material fly ashes such as waste paper sludge ash (WPSA), palm oil fuel ash (POFA) and rice husk ash (RHA) has many advantages, specifically in terms of eliminating the cost of their transportation and eventual landfill, their continuous supply and the negligible, or zero, cost of production. This research project details the process of the development of a new Cementitious Binder, produced by blending cement-free WPSA, POFA and RHA under physico-chemical activation using flue gas desulphurisation (FGD) gypsum, for use in soft soil stabilisation. The effects of different Binders produced from unary (WPSA), binary (WPSA and POFA) and ternary (WPSA, POFA and RHA) blended mixtures, along with ground and FGD gypsum activated ternary mixtures, on the geotechnical properties of soft soils, were extensively investigated. Comparisons of Atterberg limits, strength (unconfined compressive strength (UCS)), compressibility characteristics and durability (wetting-drying cycles effect) of untreated soil and soil stabilised with the optimum unary, binary, ternary and activated ternary mixtures and a reference cement treated soil, have been carried out. An investigation of the microstructural and mineralogical composition of the newly developed Binder, in comparison to those of the reference cement, was also carried out using X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) imaging and energy dispersive X-ray (EDX) spectroscopy analysis. The results indicate that the soil stabilised with the ternary mixture activated by FGD gypsum (T+FGD), had the greatest compressive strength, compressibility and durability improvement; the performance of the newly developed Cementitious Binder was comparable to that of the reference cement. This Binder comprises 8% WPSA + 2% POFA + 2% RHA activated with 5% of FGD, by the total mass of Binder. The addition of FGD gypsum has been observed to enhance the pozzolanic reaction, leading to improved geotechnical properties; mainly UCS which increased over time of curing and exceeded that for the soil treated with reference cement, after 180 days. The results obtained from XRD analysis, SEM testing and EDX analysis revealed the formation of hydrated Cementitious products represented by calcium silicate hydrates (C-S-H), Portlandite (CH) and ettringite. The formation of these hydrates reveals the developments gained in the geotechnical properties of the treated soil. A solid, coherent and compacted soil structure was achieved after using T+FGD, as confirmed by the formation of C-S-H, CH and ettringite. Therefore, a new, Cost effect, eco-friendly and sustainable Cementitious Binder has been successfully developed and can be used with confidence for soft soil stabilisation, as a 100% replacement of conventional cement.
E. Loffill - One of the best experts on this subject based on the ideXlab platform.
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stabilisation of soft soil using binary blending of high calcium fly ash and palm oil fuel ash
Applied Clay Science, 2018Co-Authors: Hm Jafer, William Atherton, Monower Sadique, Felicite Ruddock, E. LoffillAbstract:Abstract Lime and/or Ordinary Portland cement (OPC) are the traditional Binders used in soft soil stabilisation. However, their manufacture has a negative impact on the environment. This paper reports the results of experimental work for the optimisation of a binary blended Cementitious Binder (BBCB) using two types of fly ash as an alternative for use in soft soil stabilisation. The optimum content of the high calcium fly ash (HCFA) was initially determined along with the effect of grinding activation on the performance of HCFA. Subsequently, the effect of palm oil fuel ash (POFA) pozzolanic reactivity on the engineering properties of soft soil, stabilised with HCFA, was investigated by producing different binary mixtures of HCFA and POFA. Based on the Atterberg limits and unconfined compressive strength (UCS) tests, the combination of POFA with HCFA results in a considerably lower plasticity index (PI) and higher compressive strength than those obtained from the soil treated with HCFA alone. Substantial changes in the microstructure and Binders of the stabilised soil over curing time were evidenced by SEM imaging and XRD analysis. A solid and coherent structure was achieved after treatment with BBCB as evidenced by the formation of C S H, portlandite and ettringite as well as secondary calcite.
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Development of a New Ternary Blended Cementitious Binder Produced from Waste Materials for use in Soft Soil Stabilisation
Journal of Cleaner Production, 2018Co-Authors: Hm Jafer, William Atherton, Monower Sadique, Felicite Ruddock, E. LoffillAbstract:Soil stabilisation using traditional Binders such as Ordinary Portland Cement (OPC), has a serious negative environmental impact, specifically carbon dioxide (CO2) emissions as a result of the manufacture of OPC. Because of this, the use of sustainable Binders has become a critical issue to help reduce cement production through the use of by-product materials. This research seeks to develop a new ternary blended Cementitious Binder (TBCB) to replace cement for soft soil stabilisation. Different ternary mixtures containing wastes i.e., high calcium fly ash (HCFA), palm oil fuel ash (POFA) and rice husk ash (RHA) along with flue gas desulphurisation (FGD) gypsum used as a sulphate activator and grinding agent, were examined. The results illustrate that ternary mixtures improved the engineering and mechanical properties of stabilised soil. The results indicated that the plasticity index (PI) was reduced from 20.2 to 13.0 and the unconfined compressive strength (UCS) increased after 28 days of curing from 202kPa to 944kPa using the optimum non-FGD activated mixture. FGD contributed significantly by increasing the UCS to 1464kPa at 180 days of curing, which surpassed that for the reference cement (1450kPa), and by improving the soil consistency limits; where the PI decreased to 11.7 using TBCB compared with 14.5 for the soil treated with the reference cement. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis revealed substantial changes in the diffraction patterns and microstructure components of the TBCB paste over the curing period, confirming the formation of Cementitious products. A solid, coherent and compacted structure was achieved after treatment with TBCB as evidenced by the formation of C-S-H, CH and ettringite.
Paramita Mondal - One of the best experts on this subject based on the ideXlab platform.
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physico chemical interaction between mineral admixtures and opc calcium sulfoaluminate csa cements and its influence on early age expansion
Cement and Concrete Research, 2016Co-Authors: Piyush Chaunsali, Paramita MondalAbstract:Abstract The present study aims at examining the physico-chemical factors influencing the expansion characteristics of OPC–CSA blend in the presence of mineral admixtures. Three different admixtures: Class ‘F’ fly ash (‘F’FA), Class ‘C’ fly ash (‘C’FA) and silica fume (SF) were used as 15%, 15% and 5% replacement of total Cementitious Binder. Longitudinal expansion of cement pastes prepared at w/cm – 0.44 showed that the Class ‘F’FA increased the expansion whereas the Class ‘C’FA and SF reduced the expansion. The pore solution of the OPC–CSA cement pastes was extracted at different ages to monitor the concentration of various ionic species. The saturation level of ettringite was determined using a geochemical modeling program (GEMS). Furthermore, an upper bound of crystallization stress was estimated. The expansion behavior in the presence of Class ‘F’FA and SF was found to be influenced by the changes in the stiffness, whereas the expansion of the Class ‘C’FA-based mixture was governed by faster hydration of ye'elimite.
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influence of calcium sulfoaluminate csa cement content on expansion and hydration behavior of various ordinary portland cement csa blends
Journal of the American Ceramic Society, 2015Co-Authors: Piyush Chaunsali, Paramita MondalAbstract:Calcium sulfoaluminate (CSA) cements have lower carbon footprint than that of portland cement, which makes them a suitable alternative as a sustainable Cementitious Binder. Early-age expansion of CSA cements can be exploited to induce compressive stress in restrained concrete which can later counteract tensile stress developed during drying shrinkage, thus enhancing the resistance against shrinkage cracking. However, a proper understanding of the expansion behavior is critical to eliminate any risk related to expansion-induced cracking. This study examines the expansion and hydration characteristics of various ordinary portland cement (OPC)-CSA blends. Early-age expansion of paste samples was monitored. The increase in CSA cement content increased the extent of expansion. Samples having the highest CSA content (30% by mass) exhibited excessive expansion which led to their cracking. Quantitative X-ray diffraction, pore solution extraction, porosity, tensile strength, and dynamic modulus tests were performed to monitor the physico-chemical changes in OPC-CSA blends. It was shown that the ettringite supersaturation in the investigated systems gave rise to the crystallization stress, responsible for the expansion. Thermodynamic models enabled a reasonable prediction of tensile failure, particularly in the blends with the higher CSA content.
Togay Ozbakkaloglu - One of the best experts on this subject based on the ideXlab platform.
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influence of silica fume on stress strain behavior of frp confined hsc
Construction and Building Materials, 2014Co-Authors: Jia C Lim, Togay OzbakkalogluAbstract:Abstract Confinement of high-strength concrete (HSC) columns with fiber reinforced polymer (FRP) composites has been receiving increasing research attention due to the advantageous engineering properties offered by the composite system. The use of silica fume as a concrete additive is a widely accepted practice in producing HSC. However, the influence of the presence and amount of silica fume on the efficiency of FRP confinement is not clearly understood. This paper presents the results of an experimental study on the influence of silica fume on the compressive behavior of FRP-confined HSC. 30 FRP-confined and 30 unconfined concrete cylinders containing different amounts of silica fume were tested under axial compression in two phases. In the first phase of the study, specimens with a constant water–Cementitious Binder ratio were tested. The results of this phase indicate that for a given water–Cementitious Binder ratio, the compressive strength of unconfined concrete increases with an increase in the amount of silica fume. It is found that this increase in strength leads to an increased concrete brittleness, which adversely affects the effectiveness of FRP confinement. In the second phase, water–Cementitious Binder ratios of the specimens were adjusted to attain a constant unconfined concrete strength for specimens containing different amounts of silica fume. The results of these tests indicate that for a given unconfined concrete strength, strength enhancement ratios of FRP-confined HSC specimens are not influenced by the silica fume content of the concrete mix. On the other hand, it is found that the silica fume content influences the axial strain enhancement ratios of these specimens. In addition, the transition zones of the stress–strain curves of FRP-confined HSC are observed to be sensitive to the amount of silica fume used in the mix.
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Influence of silica fume on stress–strain behavior of FRP-confined HSC
Construction and Building Materials, 2014Co-Authors: Jia C Lim, Togay OzbakkalogluAbstract:Abstract Confinement of high-strength concrete (HSC) columns with fiber reinforced polymer (FRP) composites has been receiving increasing research attention due to the advantageous engineering properties offered by the composite system. The use of silica fume as a concrete additive is a widely accepted practice in producing HSC. However, the influence of the presence and amount of silica fume on the efficiency of FRP confinement is not clearly understood. This paper presents the results of an experimental study on the influence of silica fume on the compressive behavior of FRP-confined HSC. 30 FRP-confined and 30 unconfined concrete cylinders containing different amounts of silica fume were tested under axial compression in two phases. In the first phase of the study, specimens with a constant water–Cementitious Binder ratio were tested. The results of this phase indicate that for a given water–Cementitious Binder ratio, the compressive strength of unconfined concrete increases with an increase in the amount of silica fume. It is found that this increase in strength leads to an increased concrete brittleness, which adversely affects the effectiveness of FRP confinement. In the second phase, water–Cementitious Binder ratios of the specimens were adjusted to attain a constant unconfined concrete strength for specimens containing different amounts of silica fume. The results of these tests indicate that for a given unconfined concrete strength, strength enhancement ratios of FRP-confined HSC specimens are not influenced by the silica fume content of the concrete mix. On the other hand, it is found that the silica fume content influences the axial strain enhancement ratios of these specimens. In addition, the transition zones of the stress–strain curves of FRP-confined HSC are observed to be sensitive to the amount of silica fume used in the mix.
Mridul Garg - One of the best experts on this subject based on the ideXlab platform.
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Waste gypsum from intermediate dye industries for production of building materials
Construction and Building Materials, 2010Co-Authors: Mridul Garg, Neeraj JainAbstract:Abstract Paper presents the studies on characterization, beneficiation and utilization of H-acid gypsum, a waste material produced by the neutralization of free sulphuric acid collected during the formation of intermediate dyes. The waste gypsum contains impurity of organic matter like nitro compounds, naphthalene etc. The removal of impurities and improvement in colour was carried out by scrubbing with water, centrifuging and drying. The beneficiated H-acid gypsum was calcined to form β-hemihydrate plaster. The plaster was tested and evaluated for engineering properties such as compressive strength, bulk density, water absorption and porosity. These properties suggest the use of beneficiated H-acid gypsum for making building and ceramic grade plasters and for casting building blocks, board and Cementitious Binder. Data showed that Cementitious Binder of low water absorption (9.5%) and adequate compressive strength (19.6 MPa at 28 days) can be produced for use as construction material. The use of waste gypsum will definitely benefit environment and sustainable development.
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Development of alpha plaster from phosphogypsum for Cementitious Binders
Construction and Building Materials, 2009Co-Authors: Mridul Garg, Neeraj Jain, Manjit SinghAbstract:Abstract Efforts have been made to make high strength alpha plaster from phosphogypsum, a by-product of phosphoric acid industry. Phosphogypsum was autoclaved in slurry form (phosphogypsum 50% + water 50%, by wt.) in the laboratory at different steam pressures for different durations in presence of chemical admixtures. It was found that with small quantity of chemical admixture (sodium succinate/potassium citrate/sodium sulphate), alpha plaster of high strength can be produced. The optimum pressure and duration of autoclaving was found to be as 35 psi and 2.0 h, respectively. The alpha plaster was examined for making Cementitious Binders by admixing hydrated lime, fly ash, granulated blast furnace slag, marble dust and chemical additives with alpha plaster. Data showed that Cementitious Binder of compressive strength of 22.0 and 30 MPa (at 28 days of curing at 40° and 50 °C) and low water absorption was produced. DTA and SEM studies of the Binder showed formation of CSH, ettringite and C 4 AH 13 as main Cementitious products to give strength.
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Strength and durability of Cementitious Binder produced from fly ash-lime sludge-Portland cement
Indian Journal of Engineering and Materials Sciences, 2006Co-Authors: Mridul Garg, Manjit SinghAbstract:In this paper, investigations have been undertaken to produce Cementitious Binders by blending 60-70% fly ash with calcined phosphogypsum, hydrated lime sludge, Portland cement and chemical activator in different proportions. The results show that strength development of Binders takes place through formation of ettringite, C-S-H and wollastonite. The durability of Cementitious Binder has been studied by its performance in water and by accelerated aging, i.e., alternate wetting and drying as well as by heating and cooling cycles at temperatures from 27 to 50°C. The results indicate that the strength of the Binder decreased with increasing cyclic studies at different temperatures. The maximum fall in compressive strength has been noted at 50°C.
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Cementitious Binder from fly ash and other industrial wastes
Cement and Concrete Research, 1999Co-Authors: Manjit Singh, Mridul GargAbstract:Abstract In this paper, investigations were undertaken to formulate Cementitious Binder by judicious blending of fly ash with Portland cement as well as by admixing fly ash with calcined phosphogypsum, fluorogypsum, lime sludge, and chemical activators of different finenesses. The effect of addition of calcined clay in these types of Binders was studied. Data showed that Cementitious Binders of high compressive strength and water retentivity can be produced. The strength of masonry mortars increased with the addition of chemical activators. The strength development of Binders takes place through formation of ettringite, C-S-H, and C4AH13. The Binders are eminently suitable for partial replacement (up to 25%) of the cement in concrete without any detrimental affect on the strength. The results showed that fly ash can be used in the range from 45% to 70% in formulating these Binders along with other industrial wastes to help in mitigating environmental pollution.
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Durability of Cementitious Binder derived from industrial wastes
Materials and Structures, 1997Co-Authors: Manjit Singh, Mridul GargAbstract:The durability of Cementitious Binder hydrated at 27°C and 50°C under high humidity was examined by alternate wetting and drying, as well as heating and cooling, cycles at temperatures ranging from 27°C to 60°C and by performance in water. The results show that Cementitious Binder hardened at 50°C possesses higher water resistance and lower porosity than the Binder hardened at 27°C. A decrease in the strength of the Cementitious Binder was observed with an increase in temperature and in the wetting and drying and heating and cooling cycles. The maximum decrease in strength occurred at 60°C. The Cementitious Binder cured at 27°C showed a much smaller decrease in strength with a rise in temperature and in weathering cycles. The changes in strength of the Cementitious Binder were monitored by differential thermal analysis and microscopy. On a examiné la durabilité des matériaux liants hydratés à 27°C et à 50°C sous haute humidité, au moyen de cycles alternés d'humidification/dessiccation, ainsi que des cycles de chauffage/refroidissement, à des températures allant de 27°C à 60°C. Leur performance dans l'eau a également été évaluée. Les résultats montrent qu'un liant durci à 50°C possède une meilleure résistance à l'eau et une plus faible porosité qu'un liant durci à 27°C. Une chute de la résistance du liant a été observée avec l'accroissement de la température et des cycles humidification/dessiccation et chauffage/refroidissement. La perte de résistance maximale a été atteinte à 60°C. Le liant durci à 27°C montre une plus faible perte de résistance avec l'accroissement de la température et les cycles de vieillissement. Les changements de la résistance du liant ont été contrôlés par des analyses thermiques différentielles et microscopiques.