Experimental evaluation of cement mortars with recycled brass fibres from the electrical discharge machining process

This paper aims to evaluate the effect of recycled brass fibres on the physical, thermal and mechanical properties of cementitious mortars. For that purpose, seven different mortars, with the same water/cement ratio but using two different brass fibres were manufactured. Not-machined brass fibres were used as a reference and compared to the waste brass fibres obtained as a by-product of wire cutting methods through electrical discharge machines. Both fibres were added to the mortars in proportions of 0.25%, 0.5% and 1% by volume of mortar. The morphology and presence of elements in the fibres were evaluated by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). In addition, ultrasonic pulse velocity and thermal conductivity were measured to evaluate the mortar quality and the fibre dispersion into the mortar specimens. Mechanical properties were studied through flexural and compression tests. Since the fibres present a reduced length, the effect on both porosity and bulk density is negligible and the reduction on ultrasonic pulse velocity and compression strength and the slight increment on flexural strength is not remarkable due to the limited anchorage provided. Nonetheless, the improvement in the thermal conductivity of the developed mortars with recycled brass fibres, supports focusing on the niche market of heating installations, such as underfloor heating or closed-loop geothermal heat exchangers.This work has been partly financed within the European Horizon 2020 Joint Technology Initiative Shift2Rail through contract no. 826255 (IN2TRACK2). This work has also been co-financed with the project Elkartek 2019 ref. KK-2019/00023 (GOLIAT2). The authors also wish to thank the Basque Government for financial assistance through IT919-16 and IT1314-19

A parametric study on the influence of steel wool fibers in dense asphalt concrete

Environmental conditions combined with traffic loads contribute to premature deterioration of asphalt concrete pavements, reducing their strength and durability over time. To improve it, fibers can be incorporated in the mixture. Additionally, electrically conductive fibers can be used for self-healing purposes. In this context, this paper evaluates the influence of flexible steel fibers (steel wool) on the mechanical and physical properties of dense asphalt concrete. With these purposes, 25 different mixtures, with the same aggregate gradation and amount of bitumen, but with two different fibers lengths, four different percentages, and four different diameters of steel wool have been considered. Additionally, the influence of fibers on test specimens with three different types of damage: water damage, salt water damage and ageing have been evaluated through particle loss tests. Moreover, the influence of different temperatures on the flexural strength of dense asphalt concrete with steel wool fibers has been studied. It was found that steel wool fibers do not significantly improve the mechanical properties and damage resistance of dense asphalt concrete. On the other hand, steel wool fibers can change the air void distribution of a mixture, and therefore even reduce its particle loss resistance. As a recommendation, it is indicated that, for induction heating purposes, short fibers, with big diameters should be used, since they do not seem to alter the original properties of dense asphalt concrete

Thermal and Mechanical Properties of Mortars Reinforced with Recycled Brass Fibres

This paper aims to encourage the circular economy and merge the manufacturing and the construction industries, providing waste fibres from the electrical discharge machining of the former as raw material for the latter. The research analyses the effect on the physical, thermal and mechanical properties of mortars reinforced with brass fibres. The manuscript deals with different fibre length (10 mm, 15 mm and 25 mm) in variable percentages (0.5%, 1%, 2% and 4%). Larger amounts and longer fibres tend to increase the thermal conductivity whereas post cracking flexural strength is more dependent on fibre length.This work has been partly financed within the European Horizon 2020 Joint Technology Initiative Shift2Rail through contract no. 826255 (IN2TRACK2) . This work has also been cofinanced with the project Elkartek 2019 ref. KK-2019/00023 (GOLIAT2) . The authors also wish to thank the Basque Government for financial assistance through IT919-16 and IT131419

Experimental evaluation of cement mortars with recycled brass fibres from the electrical discharge machining process

This paper aims to evaluate the effect of recycled brass fibres on the physical, thermal and mechanical properties of cementitious mortars. For that purpose, seven different mortars, with the same water/cement ratio but using two different brass fibres were manufactured. Not-machined brass fibres were used as a reference and compared to the waste brass fibres obtained as a by-product of wire cutting methods through electrical discharge machines. Both fibres were added to the mortars in proportions of 0.25%, 0.5% and 1% by volume of mortar. The morphology and presence of elements in the fibres were evaluated by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). In addition, ultrasonic pulse velocity and thermal conductivity were measured to evaluate the mortar quality and the fibre dispersion into the mortar specimens. Mechanical properties were studied through flexural and compression tests. Since the fibres present a reduced length, the effect on both porosity and bulk density is negligible and the reduction on ultrasonic pulse velocity and compression strength and the slight increment on flexural strength is not remarkable due to the limited anchorage provided. Nonetheless, the improvement in the thermal conductivity of the developed mortars with recycled brass fibres, supports focusing on the niche market of heating installations, such as underfloor heating or closed-loop geothermal heat exchangers.This work has been partly financed within the European Horizon 2020 Joint Technology Initiative Shift2Rail through contract no. 826255 (IN2TRACK2). This work has also been co-financed with the project Elkartek 2019 ref. KK-2019/00023 (GOLIAT2). The authors also wish to thank the Basque Government for financial assistance through IT919-16 and IT1314-19

Damage evaluation during installation of geosynthetics used in asphalt pavements

Geosynthetics are commonly used as anti-reflective cracking systems in asphalt pavements. The rehabilitation design methods use the characteristics of as-received geosynthetics as inputs. However, these materials undergo physical damage during their installation due to mechanical and thermal loads which currently are not taken into account in the design processes. These loads can produce a reduction in geosynthetic strength and therefore, it is necessary to know the secant modulus after installation in order to improve the pavement design incorporating these materials. The secant modulus of a material indicates its initial stiffness. This paper describes an experimental study of damage due to installation of five different geosynthetics using three different procedures: (i) mechanical damage induced in the laboratory considering the action of aggregates, (ii) in situ mechanical and thermal damage due to actual installation in a test section, and (iii) a new mechanical and thermal damage experimental test developed with the aim of reproducing the real installation conditions. The main results of the study indicate that the obtained secant modulus of the tested geosynthetics reduced after applying the three damage procedures, and the loss of properties differed depending on the type and constitutive material and on the applied damage procedure.This investigation was supported by the research Project ‘Rehabilitation of roads and highways (REHABCAR)’ file number IPT-370000–2010–029, led by DRAGADOS (ACS Group), in collaboration with GEOCISA and ASFALTOS AUGUSTA among others. The project has been funded by the Ministry of Economy and Competitiveness (MINECO) within the National Plan for Scientific Research, Development and Innovation 2008–2011 (INNPACTO 2010) and the European Union under ERDF Funds (European Regional Development Fund)

A parametric study on the influence of steel wool fibers in dense asphalt concrete

Environmental conditions combined with traffic loads contribute to premature deterioration of asphalt concrete pavements, reducing their strength and durability over time. To improve it, fibers can be incorporated in the mixture. Additionally, electrically conductive fibers can be used for self-healing purposes. In this context, this paper evaluates the influence of flexible steel fibers (steel wool) on the mechanical and physical properties of dense asphalt concrete. With these purposes, 25 different mixtures, with the same aggregate gradation and amount of bitumen, but with two different fibers lengths, four different percentages, and four different diameters of steel wool have been considered. Additionally, the influence of fibers on test specimens with three different types of damage: water damage, salt water damage and ageing have been evaluated through particle loss tests. Moreover, the influence of different temperatures on the flexural strength of dense asphalt concrete with steel wool fibers has been studied. It was found that steel wool fibers do not significantly improve the mechanical properties and damage resistance of dense asphalt concrete. On the other hand, steel wool fibers can change the air void distribution of a mixture, and therefore even reduce its particle loss resistance. As a recommendation, it is indicated that, for induction heating purposes, short fibers, with big diameters should be used, since they do not seem to alter the original properties of dense asphalt concrete.ISSN:1359-5997ISSN:0025-5432ISSN:1871-687

Effect of metallic waste addition on the electrical, thermophysical and microwave crack-healing properties of asphalt mixtures

This paper aims to evaluate the effect of metallic waste addition on the electrical, thermophysical and microwave crack-healing properties of asphalt mixtures. With this purpose, asphalt mixtures with two different types of metallic waste, steel wool fibres and steel shavings, added in four different contents, were tested. Electrical and thermophysical properties of asphalt mixture specimens with, and without, metallic waste were measured. The spatial distribution of the metallic waste inside the asphalt mixture samples was evaluated by using X-ray computed tomography. In addition, crack-healing properties of asphalt samples using microwave radiation heating were assessed at two different healing times, 30 s and 40 s. To quantify the efficiency of the healing process, five healing cycles were carried out for each asphalt sample. The main results showed that asphalt mixtures with shavings presented lower air void contents than mixtures with fibres. Moreover, fibres produced an increase in the electrical conductivity of the mixtures because long fibres in the mixtures form electrically conductive channels. In contrast, shavings did not have significant effect on the electrical properties of the mixtures. Likewise, it was proven that metallic waste reduced the thermal conductivity and the specific heat capacity of asphalt mixtures. Conversely, shavings decreased the thermal diffusivity of asphalt mixtures regardless of their content. Overall, it was found that the healing level reached by the asphalt mixtures tested by microwave radiation depends on the healing time and the type and content of metallic waste used. CT-scans results proved that the spatial distribution of metallic waste inside the asphalt mixture samples was not uniform and played an important role in the asphalt self-healing properties using microwave radiation heating.</p