There are high costs in paving services in the Brazilian Amazon region, mainly due to the lack of coarse aggregate--pebble or crushed stone---in addition to the elevated rainfall and the high geographic expanse of the...There are high costs in paving services in the Brazilian Amazon region, mainly due to the lack of coarse aggregate--pebble or crushed stone---in addition to the elevated rainfall and the high geographic expanse of the region. The natural coarse aggregate often used in that region is extracted from the riverbeds a distance no less than 500 km from the major cities. In search of a technical, economic and environmental alternative to work around the problem, using an unconventional material that could replace the pebble or crushed stone, a study was carded out on natural clay, considered an abundant mineral resource, especially in the Amazon Basin. A manual mill was used for this purpose, consisting of four square metal nozzles of dimensions 12.7 mm, 9.5 mm, 4.8 mm and 2.0 mm, used for moulding the wet ribbon clay. After that, firing was carried out at temperatures of 780℃, 850℃, 950℃, 1,050 ℃ to 1,150℃ A comparative analysis between conventional hot mixed asphalt--using pebble as coarse aggregate--and that employing synthetic aggregate was made. In a general way, hot mixed asphalt using synthetic aggregate showed excellent results of physical and mechanical properties, in relation to the conventional mixture, mainly at higher temperature of aggregate calcination.展开更多
The railway network is increasingly becoming central to socio-economic development and the decarbonisation of transport,supporting its growth in compliance with the emission reduction targets set by the 2050 European ...The railway network is increasingly becoming central to socio-economic development and the decarbonisation of transport,supporting its growth in compliance with the emission reduction targets set by the 2050 European Green Deal.Thus,several programmes for the major network renewals and the construction of safe,resilient,and efficient high-speed(HS)lines have been implemented.In this scenario,some construction solutions have been introduced to enhance the durability and functionality of the railway infrastruc-ture,particularly for the ballasted track one.Among these design techniques,the asphalt or bituminous sub-ballast has emerged as a proven technology capable of improving the rail-way performance and durability.Derived from the road construction approach,asphalt sub-ballast has been used in the European HS and high-capacity(HC)lines since the 1970s,providing both structural and functional benefits.This article offers a critical review of the current knowledge on the asphalt sub-ballast applications,highlighting its technical characteristics and long-term performances.Functional,structural,and economic advan-tages have been assessed and analyzed based on laboratory scale and on-field experiences.Experimental data indeed confirm the effectiveness of asphalt sub-ballast in improving the track stability and load distribution,in providing better water drainage and in reducing fatigue induced phenomena.These enhanced properties lead to lower maintenance costs and operations,particularly those related to ballast tamping,as well as to an extended ser-vice life of the whole infrastructure.From the circular economy perspective,the re-use or recycle of wastes and by-products in these mixes amplifies the cost-benefit ratio,also improving their sustainability.展开更多
文摘There are high costs in paving services in the Brazilian Amazon region, mainly due to the lack of coarse aggregate--pebble or crushed stone---in addition to the elevated rainfall and the high geographic expanse of the region. The natural coarse aggregate often used in that region is extracted from the riverbeds a distance no less than 500 km from the major cities. In search of a technical, economic and environmental alternative to work around the problem, using an unconventional material that could replace the pebble or crushed stone, a study was carded out on natural clay, considered an abundant mineral resource, especially in the Amazon Basin. A manual mill was used for this purpose, consisting of four square metal nozzles of dimensions 12.7 mm, 9.5 mm, 4.8 mm and 2.0 mm, used for moulding the wet ribbon clay. After that, firing was carried out at temperatures of 780℃, 850℃, 950℃, 1,050 ℃ to 1,150℃ A comparative analysis between conventional hot mixed asphalt--using pebble as coarse aggregate--and that employing synthetic aggregate was made. In a general way, hot mixed asphalt using synthetic aggregate showed excellent results of physical and mechanical properties, in relation to the conventional mixture, mainly at higher temperature of aggregate calcination.
基金Project funded under the National Recovery and Resilience Plan(NRRP),Mission 4 Component 2 Investment 1.4−Call for tender No.3138 of 16/12/2021 of Italian Ministry of University and Research funded by the European Union–NextGener-ationEU.Award Number:Project code CN00000023,Concession Decree No.1033 of 17/06/2022 adopted by the Italian Ministry of University and Research,CUP D93C22000400001,“Sustainable Mobility Center”(CNMS).Spoke 4–Rail Transportation.
文摘The railway network is increasingly becoming central to socio-economic development and the decarbonisation of transport,supporting its growth in compliance with the emission reduction targets set by the 2050 European Green Deal.Thus,several programmes for the major network renewals and the construction of safe,resilient,and efficient high-speed(HS)lines have been implemented.In this scenario,some construction solutions have been introduced to enhance the durability and functionality of the railway infrastruc-ture,particularly for the ballasted track one.Among these design techniques,the asphalt or bituminous sub-ballast has emerged as a proven technology capable of improving the rail-way performance and durability.Derived from the road construction approach,asphalt sub-ballast has been used in the European HS and high-capacity(HC)lines since the 1970s,providing both structural and functional benefits.This article offers a critical review of the current knowledge on the asphalt sub-ballast applications,highlighting its technical characteristics and long-term performances.Functional,structural,and economic advan-tages have been assessed and analyzed based on laboratory scale and on-field experiences.Experimental data indeed confirm the effectiveness of asphalt sub-ballast in improving the track stability and load distribution,in providing better water drainage and in reducing fatigue induced phenomena.These enhanced properties lead to lower maintenance costs and operations,particularly those related to ballast tamping,as well as to an extended ser-vice life of the whole infrastructure.From the circular economy perspective,the re-use or recycle of wastes and by-products in these mixes amplifies the cost-benefit ratio,also improving their sustainability.
