Large quantities of natural aggregates(NA)are required in the manufacturing of asphalt mixtures for pavements.The extraction of NA generates high environmental impacts that negatively affect environmental preservation...Large quantities of natural aggregates(NA)are required in the manufacturing of asphalt mixtures for pavements.The extraction of NA generates high environmental impacts that negatively affect environmental preservation and conservation.Diverse alternative materials obtained in construction and demolition processes in civil construction worked have been studies as possible replacements for NA,with the purpose of reducing these environmental impacts.The foregoing study presents a state of knowledge review referring to the use of recycled concrete aggregates(RCA)when these are used in the manufacturing of asphalt mixtures(mainly hot-mix asphalt HMA type).Environmental aspects are presented,as well as possible benefits and limitations of using RCA as replacements for NA in asphalt mixtures.However,it is not possible to establish a behavior pattern,since the characteristics of the RCA are very heterogeneous and vary from the original source of the concrete.It is highlighted from the literature that RCA has a wide potential for use in the manufacture of asphalt mixtures,since in most studies,the mixtures with these materials comply the quality requirements contemplated by the construction specifications,mainly in low-volume roads.Additionally,based on the literature review,some recommendations and suggestions are presented for future research.展开更多
基金Supported by Science and Technology Program of Jiangxi Provincial Department of Education(No.GJJ(2007) 341)National Natural Science Foundation of China(No.31160179)the First Round Students'Scientific Research Training Program of Nanchang Institute of Technology~~
文摘Large quantities of natural aggregates(NA)are required in the manufacturing of asphalt mixtures for pavements.The extraction of NA generates high environmental impacts that negatively affect environmental preservation and conservation.Diverse alternative materials obtained in construction and demolition processes in civil construction worked have been studies as possible replacements for NA,with the purpose of reducing these environmental impacts.The foregoing study presents a state of knowledge review referring to the use of recycled concrete aggregates(RCA)when these are used in the manufacturing of asphalt mixtures(mainly hot-mix asphalt HMA type).Environmental aspects are presented,as well as possible benefits and limitations of using RCA as replacements for NA in asphalt mixtures.However,it is not possible to establish a behavior pattern,since the characteristics of the RCA are very heterogeneous and vary from the original source of the concrete.It is highlighted from the literature that RCA has a wide potential for use in the manufacture of asphalt mixtures,since in most studies,the mixtures with these materials comply the quality requirements contemplated by the construction specifications,mainly in low-volume roads.Additionally,based on the literature review,some recommendations and suggestions are presented for future research.
文摘采用野外调查和室内分析相结合的方法，研究不同植茶年限茶园土壤微团聚体的组成及其分形特征。结果表明：茶园土壤微团聚体组成以0.25～0.05 mm粒级为主，占微团聚体总量的41.95%～55.44%，0.05～0.01 mm粒级次之，占23.54%～25.66%，＜0.001 mm 粒级所占比例最小，为5.80%～8.71%，随植茶年限增加，0.25～0.05 mm粒级土壤微团聚体含量显著升高，0.05～0.01 mm 和0.01～0.005 mm 粒级含量变化不明显，而0.005～0.001 mm和＜0.001 mm粒级含量则显著降低；随植茶年限增加，土壤微团聚体平均质量比表面积值、分形维数值和土壤特征微团聚体组成比例（＜0.005 mm）/（0.25～0.05 mm）值均逐渐减小，而土壤微团聚体平均质量直径值则逐渐增大；不同植茶年限土壤微团聚体分形维数值和土壤特征微团聚体组成比例值均与土壤有机质含量、全氮含量、碱解氮含量、全磷含量和有效磷含量极显著负相关。长期植茶可促进土壤较小粒级微团聚体向较大粒级微团聚体转化，从而提高土壤微团聚体稳定性，土壤微团聚体分形维数值和土壤特征微团聚体组成比例值均可作为定量化描述茶园土壤肥力状况的指标。
