Bauxite residue is an alkaline waste material in the process of alumina production due to its characteristics of higher salinity and alkalinity,which results in environmental issues and extremely restricts the sustain...Bauxite residue is an alkaline waste material in the process of alumina production due to its characteristics of higher salinity and alkalinity,which results in environmental issues and extremely restricts the sustainable development of alumina industries.In this work,we conduct a column experiment to study the effects of two amendments on aggregate stability and variations in alkaline minerals of bauxite residue.The two amendments are phosphogypsum(PG)and phosphogypsum and vermicompost(PVC).The dominant fraction in aggregate is 1–0.25 mm in diameter on the surface,which takes up 39.34%,39.38%,and 44.51%for CK,PG,and PVC,respectively.Additions of PG and PVC decreased pH,EC,ESP,exchangeable Na^+concentration and the percentage of alkaline minerals,and then increased exchangeable Ca^2+concentration in bauxite residue.There was significant positive correlation between pH and exchangeable Na^+concentration,the percentage of cancrinite,tricalcium aluminate and calcite;while negative correlation was found in pH value versus exchangeable Ca^2+concentration.Theses findings confirmed that additions of phosphogypsum and vermicompost have a stimulative effect on aggregate stability in bauxite residue.In particular,amendment neutralization(phosphogypsum+vermicompost)in column represents an advantage for large-scale simulation of vegetation rehabilitate in bauxite residue disposal areas.展开更多
Soil stabilization has been found to be very effective in upgrading the bearing capacity of weak soils for construction purposes. The stabilizing agent, for cost efficiency, ought to provide a cheaper alternative to o...Soil stabilization has been found to be very effective in upgrading the bearing capacity of weak soils for construction purposes. The stabilizing agent, for cost efficiency, ought to provide a cheaper alternative to other possible processes. With the rapid industrialization efforts around the globe, enormous quantities of waste materials are generated and there has not been adequate mechanism for recycling and re-use of such wastes to reduce the consequent environmental problems and hazardous situations created as a result. The objective of the study is to upgrade expansive soils from Eke Obinagu, Ugwuaji in Enugu State and Egbede in Abia State Nigeria, as constructions material using RHA （rice husk ash）. Expansive clay soils were mixed with this ash, remolded and tested to examine the effect on the OMC （optimum moisture content） and the CBR （California Bearing Ratio）. The characterization of the soils was done in accordance with BS1377 and 1990b, with respect to their engineering properties which include OMC, MDD, Soaked CBR, Liquid Limit, Classification and Sieve Analysis. The rice husk was burnt and prepared in a cylindrical incinerator to form the ash. The results of classification showed A-7-5, A-6, A-2-7 soils for Eke Obinagu, Egbede and Ugwuaji, respectively. The CBR values showed increase from 5% to 29%, 7% to 13% and 5% to 23% for A-7-5, A-6 ~nd A-2-7 respectively at optimal value of 17.5% stabilization. There was also an appreciable increase in the OMC values from 15% to 33%, 14% to 25% and 15% to 31% for A-7-5, A-6 and A-2-7 soils respectively at 17.5% stabilization. Empirical models based on Scheffe＇s model were developed with the experimental results and the equations resulting from the second degree polynomials of Scheffe＇s models were solved using the least square method. The models developed showed close correlation with the experimental results for the A-7-5 and A-6 soils and will form good guide in pavement and foundation designs in the study areas.展开更多
Recent studies have revealed that concrete can be used as a media to contain As （arsenic） removed from drinking water. Concrete, which is a composite material, has been effective in solidifying hazardous wastes and ...Recent studies have revealed that concrete can be used as a media to contain As （arsenic） removed from drinking water. Concrete, which is a composite material, has been effective in solidifying hazardous wastes and contaminated soils. A research project was conducted to study the effects of uncontaminated soil and arsenic contaminated soil on the microstructure of concrete to qualitatively define the mechanisms of the encapsulation of soils containing inorganic material such as arsenic by application of solidification/stabilization technique. This research paper focused on studying the surface morphology of RPC （reactive powder concrete） containing soil.展开更多
Soil in greenhouses is likely to suffer a gradual decline in aggregate stability. Determination of the effects of different fertiliser practices on soil aggregate stability is important for taking advantage of solar g...Soil in greenhouses is likely to suffer a gradual decline in aggregate stability. Determination of the effects of different fertiliser practices on soil aggregate stability is important for taking advantage of solar greenhouses. Soil aggregate stability and iron （Fe） and aluminium （A1） oxide contents were investigated in a 26-year long-term fertilisation experiment in greenhouse in Shenyang, China, under eight fertiliser treatments： manure （M）, fertiliser N （FN）, fertiliser N with manure （MN）, fertiliser P （FP）, fertiliser P with manure （MP）, fertiliser NP （FNP）, fertiliser NP with manure （MNP）, and control without any fertiliser （CK）. A wet sieving method was used to determine aggregate size distribution and water-stable aggregates （WSA）, mean weight diameter and geometric mean diameter as the indices of soil aggregate stability. Different fertiliser treatments had a statistically significant influence on aggregate stability and Fe and A1 oxide contents. Long-term application of inorganic fertilisers had no obvious effects on the mass proportion of aggregates. By contrast, manure application significantly increased the mass proportion of macroaggregates at the expense of microaggregates. All treatments, with the exception of FNP, significantly increased the stability of macroaggregates but decreased that of microaggregates when compared with CK. Aggregation under MP and MN was better than that under M and MNP; however, no significant differences were found among inorganic fertiliser treatments （i.e., FN, FP, and FNP）. A positive relation was found between pyrophosphate-extractable Fe and WSA （r=0.269）, but no significant relations were observed between other Fe and Al oxides and aggregate stability.展开更多
基金Projects(41701587,41877511)supported by the National Natural Science Foundation of China
文摘Bauxite residue is an alkaline waste material in the process of alumina production due to its characteristics of higher salinity and alkalinity,which results in environmental issues and extremely restricts the sustainable development of alumina industries.In this work,we conduct a column experiment to study the effects of two amendments on aggregate stability and variations in alkaline minerals of bauxite residue.The two amendments are phosphogypsum(PG)and phosphogypsum and vermicompost(PVC).The dominant fraction in aggregate is 1–0.25 mm in diameter on the surface,which takes up 39.34%,39.38%,and 44.51%for CK,PG,and PVC,respectively.Additions of PG and PVC decreased pH,EC,ESP,exchangeable Na^+concentration and the percentage of alkaline minerals,and then increased exchangeable Ca^2+concentration in bauxite residue.There was significant positive correlation between pH and exchangeable Na^+concentration,the percentage of cancrinite,tricalcium aluminate and calcite;while negative correlation was found in pH value versus exchangeable Ca^2+concentration.Theses findings confirmed that additions of phosphogypsum and vermicompost have a stimulative effect on aggregate stability in bauxite residue.In particular,amendment neutralization(phosphogypsum+vermicompost)in column represents an advantage for large-scale simulation of vegetation rehabilitate in bauxite residue disposal areas.
文摘Soil stabilization has been found to be very effective in upgrading the bearing capacity of weak soils for construction purposes. The stabilizing agent, for cost efficiency, ought to provide a cheaper alternative to other possible processes. With the rapid industrialization efforts around the globe, enormous quantities of waste materials are generated and there has not been adequate mechanism for recycling and re-use of such wastes to reduce the consequent environmental problems and hazardous situations created as a result. The objective of the study is to upgrade expansive soils from Eke Obinagu, Ugwuaji in Enugu State and Egbede in Abia State Nigeria, as constructions material using RHA （rice husk ash）. Expansive clay soils were mixed with this ash, remolded and tested to examine the effect on the OMC （optimum moisture content） and the CBR （California Bearing Ratio）. The characterization of the soils was done in accordance with BS1377 and 1990b, with respect to their engineering properties which include OMC, MDD, Soaked CBR, Liquid Limit, Classification and Sieve Analysis. The rice husk was burnt and prepared in a cylindrical incinerator to form the ash. The results of classification showed A-7-5, A-6, A-2-7 soils for Eke Obinagu, Egbede and Ugwuaji, respectively. The CBR values showed increase from 5% to 29%, 7% to 13% and 5% to 23% for A-7-5, A-6 ~nd A-2-7 respectively at optimal value of 17.5% stabilization. There was also an appreciable increase in the OMC values from 15% to 33%, 14% to 25% and 15% to 31% for A-7-5, A-6 and A-2-7 soils respectively at 17.5% stabilization. Empirical models based on Scheffe＇s model were developed with the experimental results and the equations resulting from the second degree polynomials of Scheffe＇s models were solved using the least square method. The models developed showed close correlation with the experimental results for the A-7-5 and A-6 soils and will form good guide in pavement and foundation designs in the study areas.
文摘Recent studies have revealed that concrete can be used as a media to contain As （arsenic） removed from drinking water. Concrete, which is a composite material, has been effective in solidifying hazardous wastes and contaminated soils. A research project was conducted to study the effects of uncontaminated soil and arsenic contaminated soil on the microstructure of concrete to qualitatively define the mechanisms of the encapsulation of soils containing inorganic material such as arsenic by application of solidification/stabilization technique. This research paper focused on studying the surface morphology of RPC （reactive powder concrete） containing soil.
基金supported by the National Natural Science Foundation of China(No.31171997)the Fifth Session of Geping Green Action-123 Project of Liaoning Environmental Research and Education,China(No.CEPF2012-123-1-4)the Innovative Graduate Training Program of Shenyang Agricultural University of China
文摘Soil in greenhouses is likely to suffer a gradual decline in aggregate stability. Determination of the effects of different fertiliser practices on soil aggregate stability is important for taking advantage of solar greenhouses. Soil aggregate stability and iron （Fe） and aluminium （A1） oxide contents were investigated in a 26-year long-term fertilisation experiment in greenhouse in Shenyang, China, under eight fertiliser treatments： manure （M）, fertiliser N （FN）, fertiliser N with manure （MN）, fertiliser P （FP）, fertiliser P with manure （MP）, fertiliser NP （FNP）, fertiliser NP with manure （MNP）, and control without any fertiliser （CK）. A wet sieving method was used to determine aggregate size distribution and water-stable aggregates （WSA）, mean weight diameter and geometric mean diameter as the indices of soil aggregate stability. Different fertiliser treatments had a statistically significant influence on aggregate stability and Fe and A1 oxide contents. Long-term application of inorganic fertilisers had no obvious effects on the mass proportion of aggregates. By contrast, manure application significantly increased the mass proportion of macroaggregates at the expense of microaggregates. All treatments, with the exception of FNP, significantly increased the stability of macroaggregates but decreased that of microaggregates when compared with CK. Aggregation under MP and MN was better than that under M and MNP; however, no significant differences were found among inorganic fertiliser treatments （i.e., FN, FP, and FNP）. A positive relation was found between pyrophosphate-extractable Fe and WSA （r=0.269）, but no significant relations were observed between other Fe and Al oxides and aggregate stability.
