Wyniki wyszukiwania - BazTech

1

A Review of Biomass-Derived Biochar and Its Potential in Asphalt Pavement Engineering

Zhou Li

Materials Science Poland

|

2024

|

Vol. 42, No. 2

81--99

EN

Biomass-derived biochar has gained significant attention due to its unique properties and potential applications in various fields, including asphalt pavement engineering. However, there has been no comprehensive review to date that systematically examines the state-of-theart research on biochar utilization in asphalt pavements, identifies the key knowledge gaps, and provides recommendations for future research directions. This review aims to fill this gap by providing a novel and critical analysis of the sources and production methods of biochar, the techniques for modifying and characterizing its properties, and its recent applications as an asphalt binder modifier, asphalt mixture additive, and stormwater filter material. The review employs a systematic literature search and analysis methodology, using scientific databases such as Web of Science and Scopus, and keywords related to biochar, asphalt, pavement, and environmental and economic aspects. The selected studies are reviewed and synthesized to identify research gaps, challenges, and future directions, with a focus on the technical, environmental, and economic feasibility of biochar utilization in asphalt pavements. The review also examines the life cycle assessment, carbon sequestration potential, and cost-benefit analysis of biochar utilization. The novelty of this review lies in its holistic approach to assessing state-of-the-art knowledge and its identification of key research needs and opportunities for advancing this emerging field. The review aims to provide valuable insights and recommendations for researchers, practitioners, and policymakers interested in leveraging the benefits of biochar for sustainable and high-performance asphalt pavements.

2

Evaluation of physical and mechanical properties of cement-treated base incorporating crushed waste tires

Mezhoud Samy, Badache Hacene

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

|

2023

|

Vol. 32, No. 4

305--319

EN

Pavements play a pivotal role in facilitating safe and efficient transportation. However, conventional pavement construction consumes substantial virgin resources, necessitating a shift towards sustainable alternatives. This study explores the integration of crushed waste tires as partial replacements for sand and gravel in cement-treated base (CTB) layers, aiming to enhance pavement sustainability. The CTB mixtures were meticulously formulated and tested for their physical and mechanical properties. Results revealed that while the presence of waste tire aggregates affected the fresh-state rheology, the cured-state performance remained satisfactory, often exceeding normative requirements. Notably, the addition of 10% rubber powder enhanced the mechanical performance of the CTB mixtures and overall exhibited acceptable shrinkage values. The findings offer insights into designing resilient and sustainable pavement systems by using crushed waste tires, aligning with modern infrastructure demands.

3

Effect of magnetic treatment of mixing water on the behavior of cement-based materials: A review

Guelmine Layachi

Materials Science Poland

|

2023

|

Vol. 41, No. 3

27--43

EN

Magnetic treatment technology for concrete mixing water is a cost-effective and environmentally friendly approach that can enhance the performance and durability of cement-based materials. This technology aligns with the principles of sustainable development. In their studies, researchers have utilized static magnetic fields (SMF) of varying intensities to treat regular water and produce magnetically treated mixing water (MTMW) for a specific duration. Various research laboratories have successfully employed MTMW in the production of cement-based materials such as cement paste, mortar, ordinary concrete, foam concrete, self-compacting concrete, and rubber concrete. The main objective of this investigation is to review previous research that evaluated the impact of MTMW produced using different methods on the fresh, hardened, durability, and microstructure properties of cement-based materials. Most studies revealed that magnetic treatment technology improves physical and chemical properties of regular water, including solubility, surface tension, and conductivity. Regarding cement-based materials produced with MTMW, most investigations have demonstrated a significant enhancement in mechanical strength, durability, and microstructure. However, it seems that some researchers may have exaggerated their findings regarding the effect of MTMW on mechanical properties. Consequently, further research is needed to validate these results. I recommend considering the utilization of the MTMW technique for all cement-based materials to enhance their mechanical strength and durability performance.

4

Performance of Concrete Containing Partial Granite and Tiling Wastes as Fine Aggregate

Kherraf Leila, Kherraf Sihem, Hebhoub Houria, Belachia Mouloud

Civil and Environmental Engineering Reports

|

2023

|

Vol. 33, no. 2

85--105

EN

The objective of this paper is to study the properties of different compositions of concrete made by substituting sand made of crushed limestone, which is over-exploited in Algeria, by two types of sands produced by the recycling of double-layer tiling and granite waste, respectively, with different mass percentages of 0, 10, 20 and 30%. The physical, mechanical and some aspects of the durability properties of six concretes were evaluated and compared to those of a reference concrete. The results obtained show that the incorporation of granite sand up to a rate of 20% improves the compressive strength and the resistance to acid CH3COOH. For concretes made with tiling sand, the best compressive strength was observed in concrete with an addition rate of 10%. Furthermore, good tensile strength by splitting is obtained with rates of up to 30% of the two recycled sands.

5

Simulation and Heat Treatment Process of Carbon Nanotube Modified Aluminum Alloy (ZL105)

Zhang Zigi, Pan Zhilin, Li Rong, Zeng Qi, Liu Yong, Wu Quan

Archives of Foundry Engineering

|

2023

|

Vol. 23, iss. 3

38--50

EN

To further improve the mechanical properties of carbon nanotubes (CNTs) modified aluminum alloy (ZL105), the first principle was used to build the atomic structure of the alloy system and the alloy system was simulated by the VASP. After that, the heat treatment process of the cast aluminium alloy material with CNTs to enhance the alloy performance by the orthogonal experiment. The results of the research show that: (1) The energy status of the alloy system could be changed by adding the C atoms, but it did not affect the formation and structural stability of the alloy system, and the strong bond compounds formed by C atoms with other elements inside the solid solution structure can significantly affect the material properties. (2) The time of solid solution has the greatest influence on the performance of material that was modified by CNTs. The solution temperature and aging temperature were lower strength affection, and the aging time is the lowest affection. This paper provides a new research method of combining the atomic simulation with the casting experiment, which can provide the theoretical calculations to reduce the experiment times for the casting materials’ performance improvement.

6

Flexural performance of hybrid fiber reinforced cement-based materials incorporating ceramic wastes

Wu Lipeng, Li Xuanhao, Deng Hai

Archives of Civil Engineering

|

2023

|

Vol. 69, nr 3

491--506

EN

Ceramic waste generated by demolition and manufacturing processes is a kind of widely discharged solid waste; its sustainable use can reduce resource extraction, energy consumption, and carbon emissions, thereby reducing the environmental impact. In this study, ceramic powder and ceramic sand were prepared using waste ceramic wall tiles. By using three water-to-binder ratios of 0.30, 0.32, and 0.34, five ceramic powder replacement rates of 10% to 50%, and completely using ceramic sand as the fine aggregate, specimens with large differences in mechanical properties were prepared. Firstly, the compressive strength was investigated. On this basis, hybrid fibers were employed to strengthen the new matrix material, and its bending resistance was experimentally studied. It was found that the incorporation of ceramic powder reduced the compressive strength of the matrix. The water-binder ratio significantly affects compressive strength at an early age. The effect of PVA fiber on improving the ductility of the new composite is distinct. Increasing the amount of steel fiber can effectively enhance the bending bearing capacity. With a ceramic powder dosage of 50%, the new composite has shown ductile failure characteristics, even with low total fiber content. The bending properties of this new composite material, which makes extensive use of ceramic waste, are well adjustable. The bearing capacity and ductility balance can be achieved with the steel fiber content of 1% and the PVA fiber content of 1.2% to 1.50%.

7

The ability of different types of sand to preserve the integrity of calcium sulfoaluminate cement cement mortar during exposure to elevated temperatures

Tchekwagep Jean Jacques Kouadjo, Zengyao Wang, Fengzhen Yang, Piqi Zhao, Huang Shifeng, Wang Shoude, Cheng Xin Cheng

Materials Science Poland

|

2022

|

Vol. 40, No. 4

64--77

EN

Due to the depletion of natural sand resources, it is urgent to develop synthetic sand that will replace the natural one in the production of concrete. In this study, we carried out descriptive inspection of mortar working performance, mechanical properties and internal cracking under three different application schemes of fine aggregate, including natural, artificial, and basalt sand. Tests showed that the mortar with river sand had more internal cracking and lowest strength as the temperature rises. The artificial and basalt sand had better resistance and less internal cracking than river sand at high temperature. The compressive strength of basalt sand mortar (BSM) was slightly higher than that of artificial sand mortar (ASM), while the compressive strength value of river sand mortar (RSM) was the lowest at room temperature. However, when heated to 100°C, the RSM had 48% loss of strength, followed by the BSM at 45.4% and ASM at 11.6%. Above 100°C, none of the mortar samples meet the requirement of the calcium sulfoaluminate cement 42.5. The average atomic ratios (Ca/Si, Ca/Al, and Ca/Si) for the ASM and BSM increased with the rise in temperature. XRD showed that above 100°C, the diffraction peaks of Ettringite (AFt) disappeared, the number of CaSO4 diffraction peaks decreased significantly, the intensity decreased, and a diffraction peak of CaCO3 appeared.

8

The Use of Waste Ceramic Optimal Concrete for a Cleaner and Sustainable Environment - a Case Study of Mechanical Properties

Najm Hadee Mahommed, Ahmad Shakeel

Civil and Environmental Engineering Reports

|

2022

|

Vol. 32, no. 3

85--115

EN

The present study aims to find out the optimal use of ceramic powder and ceramic aggregate (both fine and coarse) as a possible substitute for Ordinary Portland Cement (OPC 43 grade) and natural aggregate (fine and coarse), respectively, in concrete, where focused on investigating the mechanical properties of waste ceramic concrete. The performance of this modified concrete was evaluated in terms of Compressive Strength (CS), Tensile Strength (TS), Flexural Strength (FS), and Combined Flexural and Torsional strength (FTS) obtained based on various experimental tests conducted on a total of 192 samples (48 cubes, 48 cylinders, 96 beams). The test results showed that ceramic waste material as a partial replacement for natural aggregate, cement, and fine aggregate provides better performance in terms of CS, TS, and FTS at optimal percentages- 20% ceramic aggregate, 10% ceramic powder, and 10% ceramic fine aggregate (Fineness Modulus 2.2) respectively in M25 grade concrete. Using ceramic waste as a partial replacement to prepare concrete has a lot of benefits from the economic, environmental, and technological point of view. Moreover, it offers a possibility for improving concrete's durability, which is vital.

9

Tailoring the mechanical properties of hypereutectic in situ Al–Mg2Si composites via hybrid TiB2 reinforcement and hot extrusion

Moazami Mohammad Rasool, Razaghian Ahmad, Mirzadeh Hamed, Emamy Massoud

Archives of Civil and Mechanical Engineering

|

2022

|

Vol. 22, no. 2

art. no. e87, 1--9

EN

Microstructure and mechanical properties of Al-15Mg 2 Si-xTiB 2 hybrid composites in the as-cast and wrought conditions were studied. TiB 2 addition led to a significant refinement and modification of primary Mg2Si particles (up to 3 wt% TiB 2 addition) via the heterogeneous nucleation mechanism, which improved the as-cast tensile properties. Further additions led to the appearance of coarse needle-shaped Al 3Ti particles with the consequent deterioration of tensile properties. Hot deformation by extrusion process and elevated-temperature exposure resulted in the fragmentation, dispersion, and spheroidization of pseudo-eutectic Mg 2 Si constituents, which led to a significant enhancement of tensile properties. The ultimate tensile strength of the extruded Al-15Mg 2 Si-3TiB 2 composite was 285 MPa with the total elongation of ~ 8%, which revealed a good strength-ductility balance. The corresponding value for the as-cast Al-15Mg 2 Si composite was only 198 MPa%. Accordingly, this study revealed that the presence of optimum amount of TiB 2 combined with high-temperature thermo-mechanical processing could remarkably improve the mechanical properties of the hypereutectic Al-Mg-Si composites in terms of strength-ductility balance, quality index, and tensile toughness.

10

Mechanical performance of ultra-high-performance strain-hardening cementitious composites according to binder composition and curing conditions

Kim Min-Jae, Oh Taekgeun, Yoo Doo-Yeol

Archives of Civil and Mechanical Engineering

|

2022

|

Vol. 22, no. 2

art. no. e63, 1--12.

EN

This study investigated the mechanical properties and microstructures of three ultra-high-performance strain-hardening cementitious composites (UHP-SHCCs) with different mix proportions and curing conditions. The binders comprised ordinary Portland cement (OPC), silica fume, and ground granulated blast furnace slag (GGBS); the specimens were cured under air and wet curing conditions for 28 and 91 days, respectively. Compressive and direct tensile tests were performed, along with subsequent microstructural analyses using the particle packing theory and scanning electron microscopy, on the composite matrix and reinforcing polyethylene (PE) fibers. The test results indicate that the inclusion of GGBS, more than 50% (by weight of OPC), leads to a decrease in compressive and tensile strength by up to 35.7% but an increase in ductility by up to 55.9%. In addition, a higher content of GGBS resulted in larger deviations based on the curing conditions. The wet curing condition was more effective for the development of a higher energy absorption capacity than the air curing condition at a curing age of 28 d. By contrast, 91 d of wet curing resulted in the lowest strain energy in this study, mainly because of the considerably reduced strain capacity.

11

Mechanical and hygrothermal performance of fly-ash and seashells concrete: in situ experimental study and smart hygrothermal modeling for Normandy climate conditions

Bouasria Manal, Benzaama Mohammed-Hichem, Pralong Valéry, El Mendili Yasmin

Archives of Civil and Mechanical Engineering

|

2022

|

Vol. 22, no. 2

art. no. e100, 1--22

EN

The aim of this study is to investigate the effect of partial substitution of cement by a smart mixture of waste materials, fly ash and Crepidula shells. The cement is replaced by fly ash and Crepidula accordingly in the range of 5, 10 and 15% by weight. This study focuses on three steps: (i) find the best formulation in terms of compression and hygrothermal behavior, (ii) build a prototype and follow the hygrothermal behavior with sensors, (III) data collection and development of a neural network model to predict the hygrothermal behavior of the prototype. The results showed that for a fly ash-Crepidula incorporation rate up to 10%, the mechanical properties are higher than the control mortar. Furthermore, the cement substitution by fly ash and Crepidula improves the thermal conductivity of concrete. With the cement replacement of 30%, a prototype was built to monitor the hygrothermal behavior. The data collected from the wireless sensors placed in the prototype are used to train and validate the artificial neural network model. The model used in this study is conducted with eight inputs and two outputs data. The investigation of the condensation risk and the mould growth shows that the chosen concrete mixture can avoid the condensation phenomenon. Indeed, the smart fly ash-Crepidula mixture provides high silica, aluminate, and calcium contents, which react with water originating from humid ambient air to form additional hydrates as a result of pozzolanic reaction and lead to a continuous strengths enhancement.

12

Mechanical performance of glulam beam-to-column connections with coach screws as fasteners

He Minjuan, Li Minmin, Li Zheng, He Guirong, Sun Yongliang

Archives of Civil and Mechanical Engineering

|

2021

|

Vol. 21, no. 2

180--196

EN

The mechanical performance of beam-to-column connections plays an essential role in the design of post-and-beam glulam structures. This paper presents an investigation into the mechanical performance of glulam beam-to-column connections with coach screws as fasteners. A series of monotonic and reversed cyclic loading tests were conducted on the beam-to-column connections with coach screws, and the failure modes, moment-resisting capacity, stiffness, ductility and energy dissipation of the connections were analyzed. Results showed that the use of coach screws was an effective way to increase the initial stiffness, ductility and energy dissipation of the glulam beam-to-column connections. The strength of coach screws and glulam members was fully developed, and the moment-resisting capacity of the beam-to-column connections was improved due to the adoption of the coach screws. It was noted that the rotational deformation and energy dissipation of the beam-to-column connections was mainly governed by the mechanical performance of the screwed connections. Moreover, a separating analytical method and a finite element model were established for the tested glulam beam-to-column connections, and results indicated that the stress distribution, deformation and moment–rotation relationships of the connections can be predicted efficaciously versus the test results.

13

Influence of curing conditions on the mechanical performance of ultra-high-performance strain-hardening cementitious composites

Kim Min-Jae, Oh Taekgeun, Yoo Doo-Yeol

Archives of Civil and Mechanical Engineering

|

2021

|

Vol. 21, no. 3

607--617

EN

This study investigated the influence of curing conditions and the inclusion of ground granulated blast furnace slag (GGBS) on the mechanical performance of ultra-high-performance strain-hardening cementitious composites (UHP-SHCC). Air- and wet-curing conditions were applied for 28 and 91 days, respectively. Compressive strength and direct tensile tests were performed, and the microstructure of the tested cementitious matrix and surface of the polyethylene (PE) fibers were inspected using scanning electron microscopy. The results showed that 3 months of wet-curing notably deteriorated the tensile performance of UHP-SHCC with or without GGBS as compared to those at the curing age of 1 month, whereas the 3 months of air-curing further enhanced the tensile performance. Therefore, the 3 months air-cured specimens, using binders consisting only of ordinary portland cement (OPC) or OPC with GGBS, could develop the highest tensile strength and strain capacity of up to 12.1 MPa and 9.1% or 13.6 MPa and 9.1%, respectively. The inclusion of GGBS led to a higher rate of stress development as well as tensile strength at the air-curing age of 3 months, resulting in the highest energy absorption capacity of 985 kJ/m3 measured in this study.

14

A study of the durability of concrete reinforced with hemp fibers exposed to external Sulfatic attack

Ziane Sami, Khelifa Mohammed-Rissel, Mezhoud Samy

Civil and Environmental Engineering Reports

|

2020

|

Vol. 30, no. 2

158--180

EN

The purpose of this paper is to study the durability of concrete reinforced with hemp fibers in the face of external Sulfatic attack. For this purpose, five types of concrete were formulated; three types of concrete reinforced with hemp fibers (HC-0.25, HC-0.5, and HC-1) at 0.25%, 0.5%, and 1 % of hemp fibers in volume, respectively. And two control concretes, being ordinary concrete (OC) and polypropylene fiber reinforced concrete (PC). To assess the sulfatic attacks, the described concrete types underwent two aging protocols: 1) a complete immersion in 12.5 % Sodium Sulfate (Na2SO4) solution, and 2) an accelerated aging protocol consisting of immersion/drying in the same sulfate solution at a temperature of 60°C. The results show that concrete reinforced with 0.25 % of hemp fibers is the optimal amount compared to control concretes in terms of physico-mechanical performance and durability under sulfate attack. This number of fibers could enable the production of green and durable structural concretes based on untreated hemp fibers.

15

The effect of limestone fineness on ternary cement fresh-state and early-age properties

Ammar N., Zeghichi L.

Mining Science

|

2017

|

Vol. 24

195--208

EN

During cement production, a significant amount of CO2 is released into the atmosphere, it is estimated that the production of each ton of clinker free about a ton of second carbon oxide. The use of additions as constituents of cement reduces the amount of clinker, where CO2 emissions are reduced. The combination of two or three additions with Portland cement can develop new types of binders (ternary or quaternary cement) with improved physical and mechanical properties compared to Portland cement alone. The objective of this work involves the study of the effects of the fineness of limestone on the physical and mechanical properties of ternary cements containing pozzolan and limestone with specific area of 3500, 5500 and 11000 cm2/g, respectively. The amount of clinker is fixed at 65% , that of limestone is varied from 10 to 35% by weight of cement, the remain is constituted of pozzolanic addition. The results showed that increasing the surface area of limestone could be with a favorable effect on the physical properties in particular the setting time and the shrinkage; further to good strength, mainly at early ages. The higher dosages of pozzolan reaching 25 % gave better mechanical performances among all other mixtures. It can be concluded that the use of combined mineral additions, limestone and pozzolan could be beneficial to formulate ternary cements with improved physical and mechanical properties for mortars based on such binders.

16

Benefits of using amorphous metallic fibers in concrete pavement for long-term performance

Yang J. M., Shin H. O., Yoo D. Y.

Archives of Civil and Mechanical Engineering

|

2017

|

Vol. 17, no. 4

750--760

EN

This study aims to examine the implications of amorphous metallic fibers on the mechanical and long-term properties of concrete pavement. Two different amounts of amorphous metallic fibers were incorporated into concrete, and plain concrete without fibers was also adopted as comparison. Test results indicated that the overall mechanical properties of concrete were improved by including the fibers, and the improvement increased when a higher amount of fibers was used. In particular, the equivalent flexural strength and flexural strength ratio were substantially improved by incorporating the amorphous metallic fibers. This may enable the thickness of airfield concrete pavement to decrease. The resistance to surface cracking of concrete pavement by repeated wheel loading was also improved with the addition of amorphous metallic fibers. In addition, by adding 5 kg/m3 and 10 kg/m3 amorphous metallic fibers in concrete pavement, roughly 1.2 times and 3.2 times longer service life was expected, respectively, as compared to their counterpart (plain concrete). Based on a life cycle cost analysis, the use of amorphous metallic fibers in concrete pavement was effective at decreasing the life cycle cost compared to plain concrete pavement, especially for severe traffic conditions.

17

Effect of modified calcium carbonate on the thermal and mechanical properties of biodegradable poly(L-lactic acid)

Cai Y.-H., Zhang Y.-H., Zhao L.-S.

Polimery

|

2015

|

T. 60, nr 2

95--99

EN

Modified calcite CaCO3 (M-CaCO3) was synthesized from calcium nitrate, sodium carbonate, ethylene diamine tetraacetic acid and sodium dodecyl sulfate. Then, poly(L-lactic acid) (PLLA)/ M-CaCO3 composites were fabricated using melt blending and hot-press forming technologies. The effect of M-CaCO3 on the thermal and mechanical performance of PLLA was investigated. The results showed that the crystallization temperature and M-CaCO3 content significantly affected the crystallization of PLLA but the effect of M-CaCO3 on the crystallization of PLLA was very complicated. Compared to neat PLLA, 1 % M-CaCO3 decreased the t1/2 from 3999.4 s to 342.7 s at 100 °C. The melt index measurements indicated that a small amount of M-CaCO3 could block the fluidity of PLLA. However, the addition of a high content M-CaCO3 increased the fluidity of PLLA. The results of tensile strengths and elongation at break of PLLA/M-CaCO3 composites showed that both M-CaCO3 content and defective modification CaCO3 affected the mechanical performance of the PLLA/M-CaCO 3composites.

PL

Z zastosowaniem azotanu wapnia, węglanu sodu, kwasu etylenodiaminotetraoctowego idodecylosiarczanu sodu syntezowano modyfikowany kalcyt (M-CaCO3), a następnie mieszając składniki wstanie stopionym wytwarzano kompozyty poli(kwas L-mlekowy)/M-CaCO3. Badano zależność właściwości termicznych i mechanicznych wytworzonych kompozytów (z matrycą polilaktydową) od zawartości M-CaCO3.Wykazano, że istotny wpływ na krystalizację PLLA wywiera temperatura oraz zawartość modyfikowanego kalcytu. W temperaturze 100 °C czas połowicznej krystalizacji (t1/2) kompozytu z udziałem 1 % M-CaCO3 znacznie się zmniejszył (342,7 s) w porównaniu do wartość t1/2 czystego PLLA (3999,4 s). Pomiar masowego wskaźnika szybkości płynięcia (MFR) dowodzi, że dodatek modyfikowanego kalcytu (powyżej 3 %) do matrycy polilaktydowej wpływa na zwiększenie wartości MFR. Wyniki wytrzymałości na rozciąganie i wydłużenia przy zerwaniu kompozytów PLLA/M-CaCO3 wykazały, że zarówno zawartość węglanu wapnia, jak i jego modyfikacja wpływają na wytrzymałość mechaniczną wytworzonych kompozytów PLLA/M-CaCO3.

18

Development, fashion, quality and innovations from SSM to rheocasting processes

Rosso M.

Archives of Materials Science and Engineering

|

2015

|

Vol. 71, nr 1

16--26

EN

Of this paper is to give an overview concerning some alternative methods for the production of enhanced performance light alloys components for critical industrial applications and to present an analysis of a new rheocasting process suitable fpr the manufacturing of high performance industrial components. Design/methodology/approach: Innovative design of some automotive parts, their characterization throught radiographic analysis to verify the integrity of the samples from metallurgical point of view. OM and SEM microstructural characterization, optical microscope, mechanical characterization based on samples machined from the produced parts. Findings: Semi-solid metal (SSM) processes demonstrated their capability to reduce the existing gap between casting and forging and during such a processes there are the opportunity to better control the defect level. Research limitations/implications: The produced parts possess excellent properties, some criticises are related to the use of ceramic cores. There is the need of innovation in industrial design to open the mentalities to new advantageous solutions. Practical implications: The principal goal to improve the competitiveness and energy savings associated to the production in high performance cars was fully accomplished. Originality/value: A study on the feasibility was included opening the route for prototype production characterized by an adequate strength as well as by higher esthetical appearance than the element produced by gravity casting process. The presence of the defects does not negatively influence or compromise the employment of the callipers neither in extreme condition, favouring their use on a very high performance cars. In the future, extension of the proposed process for the production of other important applications are expected.

19

Improvement of the mechanical performances of concrete cylinders confined actively or passively by means of SMA wires

Tran H., Balandraud X., Destrebecq J. F.

Archives of Civil and Mechanical Engineering

|

2015

|

Vol. 15, no. 1

292--299

EN

The present study deals with crush tests of concrete cylinders confined by shape memory alloy (SMA) wires. Two cases were considered. First, an active confinement was achieved by wrapping a wire previously prestrained in martensitic state and then subjected to the memory effect. Second, a passive confinement was obtained by using the same SMA, but in austenite state. For comparison purpose, an unconfined cylinder was also tested. The influence of the unwrapped zones of the confined cylinders was also investigated, leading to the use of a specially designed device to avoid premature failure in these zones. The comparison between active and passive confinements was investigated. The test results show that stiffness, strength and ductility are significantly improved in the case of the active confinement.

20

A new lightweight masonry block: Thermal and mechanical performance

Sousa L. C., Sousa H., Castro C. F., Antonio C. C., Sousa R.

Archives of Civil and Mechanical Engineering

|

2014

|

Vol. 14, no. 1

160--169

EN

The concerns with masonry building envelope performance, particularly thermal efficiency, are causing major changes in masonry solutions, mainly in south European countries, where traditionally the mild winter climate justified the use of high thermal masonry wall performance. The new European Directives regulations require different solutions. This paper describes the development a new masonry system, based on lightweight concrete units, intended for construction of large single leaf external walls without thermal insulation materials. A detailed analysis and optimization has been performed by FEM, under thermal point of view. This work was followed by a set of experimental tests in order to characterize the mechanical behavior of single units and masonry specimens. The concerns with productivity and ergonomics are also considered according their importance to the solution cost.