Traditional stabilization of backfilling material is done by using Portland cement. However, the high price of cement forced mining engineer s to seek cheaper binding materials. Fly ash, which is the indus- trial wast...Traditional stabilization of backfilling material is done by using Portland cement. However, the high price of cement forced mining engineer s to seek cheaper binding materials. Fly ash, which is the indus- trial wast e from thermal power plant, possess the potential activity of jellification, and can b e used in cemented fill as a partial substitute for cement to reduce the fill co s t. Tests were done during the past few years in Xinqiao Pyrite Mine and Phoenix Copper Mine to determine the technology parameters and the suitable content of f ly ash. Specimens with different cement/fly/ash tailings (sands) ratios were tes ted to obtain the strength values of the fill mass based on the analyses of both the chemical composition and physical and mechanical properties of fly ash . The compressive strength of specimens with a ratio of 1∶2∶8 (cement to fly ash to tailings ) can reach 2 MPa after 90 d curing, totally meeting the requiremen t of artificial pillar and reducing the fill cost by 20%-30%.展开更多
In order to study the mechanical properties and micro-mechanism of industrial waste fly ash-reinforced cement calcareous sand(FCS),the triaxial unconsolidated undrained(UU)test and scanning electron microscope tests(S...In order to study the mechanical properties and micro-mechanism of industrial waste fly ash-reinforced cement calcareous sand(FCS),the triaxial unconsolidated undrained(UU)test and scanning electron microscope tests(SEM)were carried out on it.The results of UU test show that the peak stress and energy dissipation of the FCS sample first increase and then decrease with the increase in fly ash content.Fly ash enhances the cement calcareous sand by increasing both the cohesion and internal friction angle,and adding 10%content of fly ash gives the largest values.The SEM test results shows that the hydration products of cement and fly ash filled the pores and cracks on the surface of the calcareous sand,which increased the compactness and structure of the FCS samples.The porosity of cement calcareous sand can be reduced from 27.6%to 12.8%by adding 10%fly ash.A brittleness evaluation index based on energy dissipation is proposed to quantitatively characterize the brittleness of FCS samples.The results show that when the content of fly ash is 5%,the brittleness of FCS samples is the lowest.This study shows that the mechanical properties of cement calcareous sand can be effectively enhanced by adding the appropriate amount of fly ash.展开更多
The compressive stress-strain behavior and other characteristics of treated fly ash based roof tiles have been studied by several experimental tests. This paper attempts to presents the results and observations of a s...The compressive stress-strain behavior and other characteristics of treated fly ash based roof tiles have been studied by several experimental tests. This paper attempts to presents the results and observations of a study and comparison based on the past reported experimental data. Based on the results and observations of the comprehensive experimental study, five “control points” have been identified. The new sets of experiment have been carried out to investigate whether it might be possible the use of fly ash in fly ash based roof tiles for residential construction. In the present study, treated fly ash (TFA) of C category was used with different materials as a replacement of clay for making treated fly ash stone dust roof tiles (TFASDRT). Treated fly ash stone dust roof tiles (TFASDRT) were studied at varying percentages of cement, coarse sand, and radish stone dust (RSD) along with the constant percentage of waste polythene fibre (WPF). A research program was undertaken to evaluate the suitability of such test for assessing the properties of treated fly ash stone dust roof tiles (TFASDRT). The result of this study recommends that the fly ash based roof tiles provides a sustainable supplement to the traditional clay roof tiles, they increase the efficiency of traditional roof tiles and significantly help to reduce the environmental issues associated with the disposal of these waste materials.展开更多
The strength of the mould cavity in sand casting is very much significant to attain high-quality castings. Optimization of green sand process parameters plays a vital role in minimizing casting defects. In the present...The strength of the mould cavity in sand casting is very much significant to attain high-quality castings. Optimization of green sand process parameters plays a vital role in minimizing casting defects. In the present research work, the effect of process parameters such as AFS grain fineness number, water, molasses, bentonite, fly ash, and ramming, and their levels on the resultant mould properties were investigated and optimized using Taguchi based grey relational analysis. The Taguchi L18 orthogonal array and analysis of variance(ANOVA) were used. The quality characteristics viz., green compression strength, permeability, bulk density, mould hardness and shatter index of green sand mould were optimized using grey relational grade, based on the experiments designed using Taguchi's Design of Experiments. ANOVA analysis indicated that water content is the most influential parameter followed by bentonite, and degree of ramming that contributes to the quality characteristics. The results are confirmed by calculating confidence intervals, which lies within the interval limits. Finally, microstructure observations and X-ray diffraction analysis have been performed for the optimal sand parametric combination. Results show that presence of maximum amount of SiO_2, which might be the reason for enhancement of the physical properties of the sand.展开更多
The strength of cement substituted mortar decreases with the increase in fly ash amount,whereas the strength increases when the fly ash is blended as sand substitute.A mortar with highest strength(compressive strength...The strength of cement substituted mortar decreases with the increase in fly ash amount,whereas the strength increases when the fly ash is blended as sand substitute.A mortar with highest strength(compressive strength=30.2 Mpa;flexural strength=7.0 Mpa)was obtained when the sand replacement ratio was 0.75%.The k value(cementing efficiency)of fly ash varied between 0.36 and 0.15 for the fly ash fraction in binder between 5%and 25%.The k values of fly ash used for sand replacement were all significantly above that used for cement substitution.The macropores assigned to the gaps between particles decreased when the fly ash was used as sand replacement,providing an explanation for the strength enhancement.The waste-extraction procedure(toxicity-sulphuric acid and nitric acid method(HJ/T 299-2007))was used to evaluate metal leaching,indicating the reuse possibility of fly ash blended mortar.For the mortar with the mass ratio of fly ash to binder of 0.5%,the carcinogenic risks(CR)and non-carcinogenic hazard quotient(HQ)in sensitive scenario for blended mortar utilization were 9.66 x 10 and 0.06,respectively;these results were both lower than the threshold values,showing an acceptable health risk.The CR(9.89 x 105)and HQ(3.89)of the nonsensitive scenario for fly ash treatment exceeded the acceptable threshold values,indicating health risks to onsite workers.The main contributor to the carcinogenic and non-carcinogenic risk is Cr and Cd,respectively.The CR and HQ from inhalation was the main route of heavy metal exposure.展开更多
Incinerator ash was investigated for its potential use as a replacement for sand and cement in concrete interlocking bricks. The physical characteristics of the raw materials were examined. Two sets of mixes were prep...Incinerator ash was investigated for its potential use as a replacement for sand and cement in concrete interlocking bricks. The physical characteristics of the raw materials were examined. Two sets of mixes were prepared. For the first set, sand and water quantities were fixed while incinerator ash was used at 0% to 100% replacement by weight for cement in steps of 10%. In the second set, incinerator ash was used at 0% to 100% replacement by weight for sand while cement and water quantities was fixed. The mixing proportions for cement, sand and water were 1:3:0.7, respectively. Compressive strength and leachability tests were performed on the specimens. Results showed that the replacement of sand by incinerator ash up to 40% exhibited higher compressive strength than the control mix (0% incinerator ash) after 28 days curing. Maximum compressive strength of 33.33N/mm2 was obtained after 28 days curing using using 20% incinerator ash substitution for sand. Replacement of cement by incinerator ash up to 20% exhibited higher compressive strength than the control mix. Compressive strength of 28.2 N/mm2 was achieved after 28 days curing period using a 20% ash substitution for cement. Leaching of heavy metals (Pb and Cd ) present in the ash was observed in concentrated nitric acid.展开更多
Geopolymer, an inorganic aluminosilicate material activated by alkaline medium solution, can perform as an inorganic adhesive. The geopolymer technology has a viability to substitute traditional concrete made of portl...Geopolymer, an inorganic aluminosilicate material activated by alkaline medium solution, can perform as an inorganic adhesive. The geopolymer technology has a viability to substitute traditional concrete made of portland cement (PC) because replacing PC with fly ash leads to reduced carbon dioxide emissions from cement productions and reduced materials cost. Although fly ash geopolymer stimulates sustainability, it is slow geopolymerization reaction poses a challenge for construction technology in term of practicality. The development of increasing geopolymerization reaction rate of the geopolymer is needed. The purpose of this study is to evaluate seeding nucleation agents (NA) of fly ash geopolymer that can accelerate polymerization reactions such that the geopolymer can be widely used in the construction industry. Results from the present study indicate that the use of NA (i.e., Ca(OH)2) can be potentially used to increase geopolymerization reaction rate and improve performance characteristics of the fly ash geopolymer product.展开更多
文摘Traditional stabilization of backfilling material is done by using Portland cement. However, the high price of cement forced mining engineer s to seek cheaper binding materials. Fly ash, which is the indus- trial wast e from thermal power plant, possess the potential activity of jellification, and can b e used in cemented fill as a partial substitute for cement to reduce the fill co s t. Tests were done during the past few years in Xinqiao Pyrite Mine and Phoenix Copper Mine to determine the technology parameters and the suitable content of f ly ash. Specimens with different cement/fly/ash tailings (sands) ratios were tes ted to obtain the strength values of the fill mass based on the analyses of both the chemical composition and physical and mechanical properties of fly ash . The compressive strength of specimens with a ratio of 1∶2∶8 (cement to fly ash to tailings ) can reach 2 MPa after 90 d curing, totally meeting the requiremen t of artificial pillar and reducing the fill cost by 20%-30%.
基金This research was funded by the National Natural Science Foundation of China(41772311,51968019).
文摘In order to study the mechanical properties and micro-mechanism of industrial waste fly ash-reinforced cement calcareous sand(FCS),the triaxial unconsolidated undrained(UU)test and scanning electron microscope tests(SEM)were carried out on it.The results of UU test show that the peak stress and energy dissipation of the FCS sample first increase and then decrease with the increase in fly ash content.Fly ash enhances the cement calcareous sand by increasing both the cohesion and internal friction angle,and adding 10%content of fly ash gives the largest values.The SEM test results shows that the hydration products of cement and fly ash filled the pores and cracks on the surface of the calcareous sand,which increased the compactness and structure of the FCS samples.The porosity of cement calcareous sand can be reduced from 27.6%to 12.8%by adding 10%fly ash.A brittleness evaluation index based on energy dissipation is proposed to quantitatively characterize the brittleness of FCS samples.The results show that when the content of fly ash is 5%,the brittleness of FCS samples is the lowest.This study shows that the mechanical properties of cement calcareous sand can be effectively enhanced by adding the appropriate amount of fly ash.
文摘The compressive stress-strain behavior and other characteristics of treated fly ash based roof tiles have been studied by several experimental tests. This paper attempts to presents the results and observations of a study and comparison based on the past reported experimental data. Based on the results and observations of the comprehensive experimental study, five “control points” have been identified. The new sets of experiment have been carried out to investigate whether it might be possible the use of fly ash in fly ash based roof tiles for residential construction. In the present study, treated fly ash (TFA) of C category was used with different materials as a replacement of clay for making treated fly ash stone dust roof tiles (TFASDRT). Treated fly ash stone dust roof tiles (TFASDRT) were studied at varying percentages of cement, coarse sand, and radish stone dust (RSD) along with the constant percentage of waste polythene fibre (WPF). A research program was undertaken to evaluate the suitability of such test for assessing the properties of treated fly ash stone dust roof tiles (TFASDRT). The result of this study recommends that the fly ash based roof tiles provides a sustainable supplement to the traditional clay roof tiles, they increase the efficiency of traditional roof tiles and significantly help to reduce the environmental issues associated with the disposal of these waste materials.
基金financially supported by the National Institute of Technology,Manipur,India
文摘The strength of the mould cavity in sand casting is very much significant to attain high-quality castings. Optimization of green sand process parameters plays a vital role in minimizing casting defects. In the present research work, the effect of process parameters such as AFS grain fineness number, water, molasses, bentonite, fly ash, and ramming, and their levels on the resultant mould properties were investigated and optimized using Taguchi based grey relational analysis. The Taguchi L18 orthogonal array and analysis of variance(ANOVA) were used. The quality characteristics viz., green compression strength, permeability, bulk density, mould hardness and shatter index of green sand mould were optimized using grey relational grade, based on the experiments designed using Taguchi's Design of Experiments. ANOVA analysis indicated that water content is the most influential parameter followed by bentonite, and degree of ramming that contributes to the quality characteristics. The results are confirmed by calculating confidence intervals, which lies within the interval limits. Finally, microstructure observations and X-ray diffraction analysis have been performed for the optimal sand parametric combination. Results show that presence of maximum amount of SiO_2, which might be the reason for enhancement of the physical properties of the sand.
基金The authors gratefully acknowledge the support from the National Natural Science Foundation of China(Grant No.NSFC21107062)the Key Laboratory for Solid Waste Management and Environment Safety(Tsinghua University)Foundation(Grant No.SWMES 2015-10).
文摘The strength of cement substituted mortar decreases with the increase in fly ash amount,whereas the strength increases when the fly ash is blended as sand substitute.A mortar with highest strength(compressive strength=30.2 Mpa;flexural strength=7.0 Mpa)was obtained when the sand replacement ratio was 0.75%.The k value(cementing efficiency)of fly ash varied between 0.36 and 0.15 for the fly ash fraction in binder between 5%and 25%.The k values of fly ash used for sand replacement were all significantly above that used for cement substitution.The macropores assigned to the gaps between particles decreased when the fly ash was used as sand replacement,providing an explanation for the strength enhancement.The waste-extraction procedure(toxicity-sulphuric acid and nitric acid method(HJ/T 299-2007))was used to evaluate metal leaching,indicating the reuse possibility of fly ash blended mortar.For the mortar with the mass ratio of fly ash to binder of 0.5%,the carcinogenic risks(CR)and non-carcinogenic hazard quotient(HQ)in sensitive scenario for blended mortar utilization were 9.66 x 10 and 0.06,respectively;these results were both lower than the threshold values,showing an acceptable health risk.The CR(9.89 x 105)and HQ(3.89)of the nonsensitive scenario for fly ash treatment exceeded the acceptable threshold values,indicating health risks to onsite workers.The main contributor to the carcinogenic and non-carcinogenic risk is Cr and Cd,respectively.The CR and HQ from inhalation was the main route of heavy metal exposure.
文摘Incinerator ash was investigated for its potential use as a replacement for sand and cement in concrete interlocking bricks. The physical characteristics of the raw materials were examined. Two sets of mixes were prepared. For the first set, sand and water quantities were fixed while incinerator ash was used at 0% to 100% replacement by weight for cement in steps of 10%. In the second set, incinerator ash was used at 0% to 100% replacement by weight for sand while cement and water quantities was fixed. The mixing proportions for cement, sand and water were 1:3:0.7, respectively. Compressive strength and leachability tests were performed on the specimens. Results showed that the replacement of sand by incinerator ash up to 40% exhibited higher compressive strength than the control mix (0% incinerator ash) after 28 days curing. Maximum compressive strength of 33.33N/mm2 was obtained after 28 days curing using using 20% incinerator ash substitution for sand. Replacement of cement by incinerator ash up to 20% exhibited higher compressive strength than the control mix. Compressive strength of 28.2 N/mm2 was achieved after 28 days curing period using a 20% ash substitution for cement. Leaching of heavy metals (Pb and Cd ) present in the ash was observed in concentrated nitric acid.
文摘Geopolymer, an inorganic aluminosilicate material activated by alkaline medium solution, can perform as an inorganic adhesive. The geopolymer technology has a viability to substitute traditional concrete made of portland cement (PC) because replacing PC with fly ash leads to reduced carbon dioxide emissions from cement productions and reduced materials cost. Although fly ash geopolymer stimulates sustainability, it is slow geopolymerization reaction poses a challenge for construction technology in term of practicality. The development of increasing geopolymerization reaction rate of the geopolymer is needed. The purpose of this study is to evaluate seeding nucleation agents (NA) of fly ash geopolymer that can accelerate polymerization reactions such that the geopolymer can be widely used in the construction industry. Results from the present study indicate that the use of NA (i.e., Ca(OH)2) can be potentially used to increase geopolymerization reaction rate and improve performance characteristics of the fly ash geopolymer product.