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Tendons play a pivotal role in facilitating joint movement by transmitting muscular forces to bones. The intricate hierarchical structure and diverse material composition of tendons contribute to their non-linear mechanical response. However, comprehensively grasping their mechanical properties poses a challenge due to inherent variability in biological tissues. This necessitates a thorough examination of uncertainties associated with properties measurements, particularly under diverse loading conditions. Given the cyclic loading experienced by tendons throughout an individual's lifespan, understanding their mechanical behaviour under such circumstances becomes crucial. This study addresses this need by introducing a generalised Paris Erdogan Law tailored for non-linear materials. To examine uncertainties within this proposed framework, Monte Carlo Analysis is employed. This approach allows for a thorough exploration of the uncertainties associated with tendon mechanics, contributing to a more robust comprehension of their behaviour under cyclic loading conditions. Finally, self-healing has been integrated into the fatigue law of tendons through the proposal of a healing function, formulated as a polynomial function of the maximum stress. This approach allows to account for an increase in the number of cycles for each stress value due to self-repair after the damage event generated by long-term cycling load over the individual's life span. • -Development of a Generalised Paris Erdogan law for non-linear materials such as soft tissues. • -Use of Monte Carlo Analysis for robust comprehension of tendon mechanics uncertainties. • -Estimation of mechanical parameters C and m_p for the PE law in tendon cases. • -Introduction of Healing Function to observe increased cycles due to self-healing effect. [ABSTRACT FROM AUTHOR]

The established state-of-the-art for composite solid propellant grain manufacture consists in mix-cast-cure process using hazardous chemicals and specific molds for propellant forming. In most of the cases, polyaddition of oligomers involves isocyanate functional groups. Construction constraints limit the feasibility of propellant geometries, confining the pressure-time history of rocket motors to some established configurations. Composition pot-life becomes one of the most important parameters in the definition of correlated industrial processes. An additive manufacturing process for propellant grain production based on UV curing has been recently proposed for patenting. This technique enables more complex grain geometries, paving the way for new propulsive missions, thanks to customized thrust-time profiles or local composition fine tuning. The new curative method makes innovative use of pre-polymers, replacing isocyanates with UV-sensitive components characterized by lower chemical hazard for operators. The paper illustrates the experimental results obtained during the preliminary test campaign on propellant inert simulators, produced as lab-scale proof of concept. The activity targeted mono-layer samples, focusing on binder properties. Dynamic-mechanical thermal analysis, thermal-gravimetric analysis, and stress–strain tests have been carried out to measure mechanical and physical characteristics of different formulations. Both hydroxyl-terminated polybutadiene (HTPB) and polybutadiene diacrylate (PBDDA) binders have been considered, using ammonium sulfate as substitute of ammonium perchlorate. Aluminized and non-aluminized samples have been manufactured to evaluate the impact of opaque-reflective materials during the UV curing process. The reported analyses show comparable results for both the new UV-cured materials and demonstrate the feasibility of propellants based on isocyanate-free process. • Solid propellants are produced without isocyanates using photo-polymerization. • Photo-polymerization can work with HTPB, PBDDA, and some nonfunctional polymers. • Removal of isocyanates can reduce operator risks and environmental issues. • Photo-polymerization enables additive manufacturing of solid propellant grains. [ABSTRACT FROM AUTHOR]

This study delves into the rheological and mechanical properties of a 3D-printable composite solid propellant with 80% wt solids loading. Polybutadiene is used as a binder with ammonium sulfate, which is added as an inert replacement for the ammonium perchlorate oxidizer. Further additives are introduced to allow for UV curing. An in-house illumination system made of four UV-A LEDs (385 nm) is employed to cure the resulting slurry. Rheological and mechanical tests are conducted to evaluate the viscosity, ultimate tensile strength and strain, and compression behavior. Viscosity tests are performed for both pure resin and complete propellant composition. A viscosity reduction factor is obtained for the tested formulations when pre-heating slurry. Uniaxial tensile and compression tests reveal that the mechanical properties are consistent with previous research. Results emphasize the critical role of temperature and solid loading percentage. Pre-heating resin composites may grant a proper viscosity reduction while keeping mechanical properties in the applicability range. Overall, these findings pave the way for the development of a 3D printer prototype for composite solid propellants. [ABSTRACT FROM AUTHOR]

Alkaline solutions, such as sodium, potassium or lithium silicates, appear to be very promising as healing agents for the development of encapsulated self-healing concretes. However, the evolution of their mechanical and acoustic properties in time has not yet been completely clarified, especially regarding their behavior and related kinetics when they are used in the form of a thin layer in contact with a hardened cement matrix. This study aims to monitor, using linear and nonlinear ultrasonic methods, the evolution of a sodium silicate solution interacting with a cement matrix in the presence of localized cracks. The ultrasonic inspection via linear methods revealed that an almost complete recovery of the elastic and acoustic properties occurred within a few days of healing. The nonlinear ultrasonic measurements contributed to provide further insight into the kinetics of the recovery due to the presence of the healing agent. A good regain of mechanical performance was ascertained through flexural tests at the end of the healing process, confirming the suitability of sodium silicate as a healing agent for self-healing cementitious systems. [ABSTRACT FROM AUTHOR]

The paper presents the results of an experimental investigation conducted on clay bricks and different types of restoration products commonly available on the European market, specifically a tixotropic mix for production of mortars and structural plasters, two cement-free binders for dehumidifying mortars, a cement-free grout to be used as filler for voids and cavities in masonry structures, a cement-free dehumidifying mortar for the restoration of damp stone, brick and tuff masonry, and a one-component mortar for plaster repair. Prism-shaped specimens were produced using single materials and coupled materials. They were subjected to static compressive tests for the determination of their mechanical properties and cyclic compressive tests for the analysis of their fatigue behavior; the final aim is to develop an experimental procedure for assessing the effectiveness of strengthening materials. A parameter, α, was defined based on the results of the static compressive tests. It was used for the characterization of the long-term interaction between parent material and restoration mortar. Finally, a simple procedure for selecting an appropriate repair mortar is suggested based on such a parameter. [ABSTRACT FROM AUTHOR]

Abstract: This investigation, conducted at the Non-Destructive Testing Laboratory at the Politecnico di Torino, made it possible to establish an experimental relationship between specific creep values measured in concrete test pieces obtained from different mixes and the decrease in temperature observed in identical test pieces at the end of low-intensity short-duration compressive tests. This relationship is independent of type of mix and therefore has general validity: it can be used to make qualitative predictions about creep without having to perform long duration tests. It may lead to interesting developments in various applications, especially in the field of structural diagnosis. [Copyright &y& Elsevier]

This paper brings a new insight into understanding the influence of macrocapsules in packing systems, which can be useful in designing the inert structure of self-healing concrete. A variety of tubular macrocapsules, in terms of types and sizes, was used to assess the capsules' effect in the packing, together with various aggregate types and fractions. The voids ratios (U) of aggregate mixtures were evaluated experimentally and compared with the prediction via the particle packing model of Dewar. The packing of coarse particles was found to be considerably affected by the presence of macrocapsules, while no capsules' effect on the packing of fine particles was attained. A higher capsule dosage and capsule aspect ratio led to a higher voids ratio. In the formulation of the inert structure, the packing disturbance due to capsules can be minimised by increasing the content of fine aggregates over coarse aggregates. Dewar's model showed a good compatibility with experimental results in the absence of capsules. However, the model needed to be upgraded for the introduction of tubular macrocapsules. Accordingly, the effect of macrocapsules was extensively analysed and a 'U model' for capsules (with some limitations) was finally proposed, offering a high predicting accuracy. [ABSTRACT FROM AUTHOR]

Purpose: One of the main problems of knee replacement is the limit of knee flexion. This study focuses on the knee implant and the patellar component currently in use in total knee arthroplasty, analyzing the influence of patellar thickness on the degree of knee flexion following surgery. Methods: A kinematics study was performed to evaluate whether an optimal patellar thickness can be identified, which enables the maximum flexion angle to be achieved. Using TC images, a healthy model was built. On this basis, a model of a knee joint which had undergone total knee arthroplasty using a Legion PS prosthesis was constructed. Initially, the standard thickness of patellar implant (9 mm) was used to build the model; then several different patellar implant thicknesses (in the range of 5-15 mm) were analyzed. Results: The results show a non-linear trend: a button thickness of less than 9 mm does not change the flexion angle, whereas a button thickness of over 9 mm results in a loss of flexion. The flexion loss is significant in the first two additions of thicknesses but negligible in the last ones. Conclusions: In the case studied, flexion reduction is not linearly proportional to the patellar thickness. The outcome of total knee arthroplasty is considered to be satisfactory with the standard patellar button. The results of this study could be used to compare the kinematics with other total prosthesis and patellar implants, and should enable the optimization of the patellar residue bone thickness to obtain deep flexion. [ABSTRACT FROM AUTHOR]

Effective diagnostic and monitoring systems are highly needed in the building and infrastructure sector, to provide a comprehensive assessment of the structural health state and improve the maintenance and restoration planning. Vibration-based techniques, and especially ambient vibration testing, have proved to be particularly suitable for both periodic and continuous monitoring of existing structures. As a general requirement, permanent systems must include a sensing network able to run a continuous surveillance and provide reliable analyses based on different information sources. The variability in the environmental and operating conditions needs to be accounted for in designing such a sensor network, but it is mainly the structural typology that governs the optimal sensor placement strategy. Architectural heritage consists of a great variety of buildings and monuments that significantly differ from each other in terms of typology, historic period, construction techniques, and materials. In this paper, the main issues regarding seismic protection and analysis of the modern architectural heritage are introduced and applied to one of the vaulted structures built by Pier Luigi Nervi in the Turin Exhibition Centre. The importance of attaining an adequate level of knowledge in historic structures is also highlighted. After an overview of the Turin Exhibition Centre and its construction innovations, this paper focuses on Hall B, describing the structural design conceived by Pier Luigi Nervi. A seismic assessment of the structures of Hall B is then presented, considering the potential seismic damage to nonstructural elements. Subsequently, the application of an optimal sensor placement strategy is described with reference to two different scenarios: the first one corresponding to the undamaged structure and the second one that considers a possible damage to the infill walls. Finally, a novel damage-scenario-driven sensor placement strategy based on a combination of the two above mentioned is proposed and discussed. One of the major conclusions drawn from the analyses performed is that nonstructural elements undergoing seismic damage or degradation may significantly affect the global dynamic response and consequently the optimal sensing configurations. [ABSTRACT FROM AUTHOR]

Composite solid propellants have used cast molding production technology for many decades, with intrinsic limitations on production flexibility, promptness, and grain geometry, as well as environmental implications on toxicity and global carbon footprint. This traditional method involves the use of toxic chemicals, has a long processing time, requires high temperature, and the products have limited geometries. To overcome those issues, different photo-curable resins have been evaluated as possible matrices. In fact, the UV-curing process is fast and has low energy consumption. The photocuring reaction parameters of six different pristine formulations were evaluated by Fourier transform infrared spectroscopy analysis. After finding the optimal curing parameters, different composites were prepared by adding 75 or 80 wt% ammonium sulfate particles used as an inert replacement for the oxidant. The thermomechanical properties and thermal resistance of the UV-cured composites were characterized via dynamic thermal-mechanical and thermogravimetric analysis. Subsequently, the mechanical properties of the inert propellants were investigated by tensile tests. The most promising resin systems for the production of solid rocket propellants were then 3D printed by an in-house developed illumination system and the obtained object micro-structure was evaluated by X-ray computed tomography. [ABSTRACT FROM AUTHOR]

In this paper, dense and lightened geopolymer materials based on calcined kaolin and different alkali activators were prepared and submitted to a physical and mechanical characterization: density measurement, mechanical tests (flexural and compressive tests) and thermal conductivity analysis were carried out. First, pastes were prepared by using both sodium and potassium silicate solutions. It was found that the chemical composition of the alkali solution has a minor effect on the flexural strength, while it significantly affects compressive strength and stiffness in three-point-bending, being the best performance obtained with the sodium silicate solution. Then, starting from this paste formulation, different dense materials were prepared, including mortars and composite samples containing a commercial acrylate emulsion (Primal B60A), used to improve the workability of the pastes and the mechanical properties of the cured samples. The Primal-free dense specimens showed good compressive strengths (20–30 MPa) in line with literature for metakaolin-based materials. However, Primal addition was effective in enhancing the compressive strength up to 46 MPa. Finally, different sets of low-density materials were prepared: lightweight samples, produced with expanded glass spheres (Poraver ® ) and macroporous samples, foamed with hydrogen peroxide in different amounts. All these samples appeared homogenous with very limited segregation phenomena. The thermal conductivity ranged from 0.12 to 0.78 W/m K, in function of the density of the samples: the lowest values, presented by the macroporous materials, were comparable with those of most commonly used building insulation materials. As a whole, this work has shown the versatility of geopolymers towards the elaboration of a variety of materials with different macroscopic features: from pastes, to mortars, to lightweight samples, to macroporous samples. Finally, the feasibility of producing bilayer materials has been assessed: samples made by superimposing a lightened layer over a millimetric layer of geopolymer paste or mortars after its partial curing were successfully prepared. [ABSTRACT FROM AUTHOR]

The aim of this research is to produce self-healing cementitious composites based on the use of cylindrical capsules containing a repairing agent. Cementitious hollow tubes (CHT) having two different internal diameters (of 2 mm and 7.5 mm) were produced by extrusion and used as containers and releasing devices for cement paste/mortar healing agents. Based on the results of preliminary mechanical tests, sodium silicate was selected as the healing agent. The morphological features of several mix designs used to manufacture the extruded hollow tubes, as well as the coatings applied to increase the durability of both core and shell materials are discussed. Three-point bending tests were performed on samples produced with the addition of the above-mentioned cementitious hollow tubes to verify the self-healing effectiveness of the proposed solution. Promising results were achieved, in particular when tubes with a bigger diameter were used. In this case, a substantial strength and stiffness recovery was observed, even in specimens presenting large cracks (>1 mm). The method is inexpensive and simple to scale up; however, further research is needed in view of a final optimization [ABSTRACT FROM AUTHOR]

Epoxy resins, widely used in conservation, still remain controversial materials. Considering some of the drawbacks that currently limit the application of epoxy consolidants, we present the application of the cationic ring opening polymerization as a novel method to cure the epoxy monomer in the restoration field. The cationic polymerization was carried out through a redox system based on the reduction of the iodonium salt in the presence of ascorbic acid catalyzed by a copper salt. The use of this initiator system for carrying out a suitable consolidant for lime plaster is considered. First, the film properties of the cured films were investigated. Then, the formulation was applied on a sample of plaster and its compatibility was verified. Its effectiveness as a consolidant product is explored through the evaluation of chromatic changes, mechanical strength, morphology of the re-aggregated material, and changes of the surface properties. [ABSTRACT FROM AUTHOR]

This review aims to provide a comprehensive assessment concerning alkali activation of natural stone wastes and minerals. In particular, the structure of the review is divided into two main sections in which the works dealing with alumino-silicate and carbonatic stones are discussed, respectively. Alumino-silicate stones are generally composed of quartz and feldspars, while carbonatic stones are mainly made of calcite and dolomite. The role of these minerals in the alkali activation process is discussed, attesting their influence in the development of the final product properties. In most of the works, authors use mineral additions only as fillers or aggregates and, in some cases, as a partial substitution of more traditional raw powders, such as metakaolin, fly ash, and granulated blast furnace slag. However, a few works in which alumino-silicate and carbonatic stone wastes are used as the main active components are discussed as well. Not only the raw materials, but also the entire alkali activation process and the curing conditions adopted in the literature studies here reviewed are systematically analyzed to improve the understanding of their effect on the physical, mechanical, and durability properties of the final products and to eventually foster the reuse of natural stone wastes for the purposes of sustainability in different applications. [ABSTRACT FROM AUTHOR]

Capsule-based self-healing is increasingly being targeted as an effective way to improve the durability and sustainability of concrete infrastructures through the extension of their service life. Assessing the mechanical and durability behaviour of self-healing materials after damage and subsequent autonomous repair is essential to validate their possible use in real structures. In this study, self-healing mortars containing cementitious tubular capsules with a polyurethanic repairing agent were experimentally investigated. Their mechanical behaviour under both static and cyclic loading was analysed as a function of some factors related to the capsules themselves (production method, waterproof coating configuration, volume of repairing agent stored) or to the specimens (number, size and distribution of the capsules in the specimen). Their mechanical performances were quantified in terms of recovery of load-bearing capacity under static conditions and number of cycles to failure as a function of the peak force under cyclic conditions. Positive results were achieved, with a maximum load recovery index up to more than 40% and number of cycles to failure exceeding 10,000 in most cases, with peak force applied during cyclic loading at least corresponding to 70% of the estimated load-bearing capacity of the healed samples. [ABSTRACT FROM AUTHOR]

Development and commercialization of self-healing concrete is hampered due to a lack of standardized test methods. Six inter-laboratory testing programs are being executed by the EU COST action SARCOS, each focusing on test methods for a specific self-healing technique. This paper reports on the comparison of tests for mortar and concrete specimens with polyurethane encapsulated in glass macrocapsules. First, the pre-cracking method was analysed: mortar specimens were cracked in a three-point bending test followed by an active crack width control technique to restrain the crack width up to a predefined value, while the concrete specimens were cracked in a three-point bending setup with a displacement-controlled loading system. Microscopic measurements showed that with the application of the active control technique almost all crack widths were within a narrow predefined range. Conversely, for the concrete specimens the variation on the crack width was higher. After pre-cracking, the self-healing effect was characterized via durability tests: the mortar specimens were tested in a water permeability test and the spread of the healing agent on the crack surfaces was determined, while the concrete specimens were subjected to two capillary water absorption tests, executed with a different type of waterproofing applied on the zone around the crack. The quality of the waterproofing was found to be important, as different results were obtained in each absorption test. For the permeability test, 4 out of 6 labs obtained a comparable flow rate for the reference specimens, yet all 6 labs obtained comparable sealing efficiencies, highlighting the potential for further standardization. [ABSTRACT FROM AUTHOR]

Development and commercialization of self-healing concrete is hampered due to a lack of standardized test methods. Six inter-laboratory testing programs are being executed by the EU COST action SARCOS, each focusing on test methods for a specific self-healing technique. This paper reports on the comparison of tests for mortar and concrete specimens with polyurethane encapsulated in glass macrocapsules. First, the pre-cracking method was analysed: mortar specimens were cracked in a three-point bending test followed by an active crack width control technique to restrain the crack width up to a predefined value, while the concrete specimens were cracked in a three-point bending setup with a displacement-controlled loading system. Microscopic measurements showed that with the application of the active control technique almost all crack widths were within a narrow predefined range. Conversely, for the concrete specimens the variation on the crack width was higher. After pre-cracking, the self-healing effect was characterized via durability tests: the mortar specimens were tested in a water permeability test and the spread of the healing agent on the crack surfaces was determined, while the concrete specimens were subjected to two capillary water absorption tests, executed with a different type of waterproofing applied on the zone around the crack. The quality of the waterproofing was found to be important, as different results were obtained in each absorption test. For the permeability test, 4 out of 6 labs obtained a comparable flow rate for the reference specimens, yet all 6 labs obtained comparable sealing efficiencies, highlighting the potential for further standardization. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) can produce complex vascular network configurations, yet limited testing has been done to characterize the damage and healing behavior of concrete with embedded networks for self-healing. In this study, different AM methods and network wall materials were used to produce vascular networks for self-healing concrete prisms, where their load-response behavior, healing efficiency and microstructure were evaluated using non-destructive techniques: acoustic emission (AE), ultrasonic pulse velocity (UPV), digital image correlation (DIC), and X -ray computed tomography (CT). The types of healing agent release mechanisms that were studied include a ductile-porous network that supplies fluid from its pores and a brittle network that fractures under load to release fluid. DIC coupled with AE verified debonding of ductile-porous networks from the cementitious matrix, and was able to track damage progression as well as healing for all networks with load regains up to 56 % and stiffness regains up to 91 % using polyurethane. [ABSTRACT FROM AUTHOR]

Heuristically known at least since the first half of XIX century, the self-healing capacity of cement-based materials has been receiving keen attention from the civil engineering community worldwide in the last decade. As a matter of fact, stimulating and/or engineering the aforementioned functionality via tailored addition and technologies, in order to make it more reliable in an engineering perspective, has been regarded as a viable pathway to enhance the durability of reinforced concrete structures and contribute to increase their service life. Research activities have provided enlightening contributions to understanding the mechanisms of crack self-sealing and healing and have led to the blooming of a number of self-healing stimulating and engineering technologies, whose effectiveness has been soundly proved in the laboratory and, in a few cases, also scaled up to field applications, with ongoing performance monitoring. Nonetheless, the large variety of methodologies employed to assess the effectiveness of the developed self-healing technologies makes it necessary to provide a unified, if not standardized, framework for the validation and comparative evaluation of the same self-healing technologies as above. This is also instrumental to pave the way towards a consistent incorporation of self-healing concepts into structural design and life cycles analysis codified approaches, which can only promote the diffusion of feasible and reliable self-healing technologies into the construction market. In this framework the Working Group 2 of the COST Action CA 15202 “Self-healing as preventive repair of concrete structures – SARCOS” has undertaken the ambitious task reported in this paper. As a matter of fact this state of the art provides a comprehensive and critical review of the experimental methods and techniques, which have been employed to characterize and quantify the self-sealing and/or self-healing capacity of cement-based materials, as well as the effectiveness of the different self-sealing and/or self-healing engineering techniques, together with the methods for the analysis of the chemical composition and intrinsic nature of the self-healing products. The review will also address the correlation, which can be established between crack closure and the recovery of physical/mechanical properties, as measured by means of the different reviewed tests. [ABSTRACT FROM AUTHOR]

The use of capsule-based technology for self-sealing and self-healing cementitious systems has been extensively investigated for both macro- and microencapsulated additions. In this study, macrocapsules, produced using a novel technique were characterised and compared, evaluating mechanical triggering, bonding with the cementitious matrix, and self-sealing efficiency upon integration into cementitious mortar specimens. Macrocapsules containing a commercially available water repellent agent were produced in two ways. Stereolithographic additive manufacturing (3D printing) was used to produce novel rigid acrylate macrocapsules as well as alumina ones. Cementitious macrocapsules produced with a rolling technique were also used as a comparison. The capsules were characterised in terms of watertightness, water uptake, and shell morphology. Following this, the capsules were integrated into cement mortar prisms and subjected to controlled cracking by three-point bending to evaluate the triggering and subsequent self-sealing effect. The results highlighted influential process parameters that can be optimised and explored for further capsule-based self-sealing in structural applications. [ABSTRACT FROM AUTHOR]

Impressive amounts of wastes are produced yearly by extraction and transformation of natural stones. This work addresses the finest fraction of these wastes, named stone muds, and particularly those with a siliceous composition. The disposal in dump of these muds implies high costs, whereas their surface landing poses serious challenges, since they can damage the environment, create necrotic conditions for flora and fauna, and endanger human health. Therefore, the reemployment of these wastes is today an urgent need. In this work, a mud (QM) composed by quartz, feldspars, biotite and dolomite, is used for producing dense and foamed alkali-activated materials through an innovative and simple process, in which a mixture of mud and alkaline solution (plus foaming agent, when needed) is produced, cast in moulds and cured at 80 °C for 48 h. Another mineral powder (SRM), having a similar composition but carbonates-free, was also used, to prove the key role of alumino-silicates in producing dense alkali-activated materials, with excellent mechanical properties. Also, the foamed samples showed good mechanical properties, plus low thermal conductivity. These results demonstrate that alumino-silicate wastes could serve as source materials for producing materials suitable to be used for dense and cellular building elements, providing an effective alternative to mud disposal and related issues. [ABSTRACT FROM AUTHOR]

Concrete sensors, which are manufactured by mixing conductive fibres (such as carbon nanotubes (CNTs)) with concrete, are one of the most significant and economical types of sensor. Two main factors affecting the performance of concrete sensors are the amount of CNTs and the quality of their dispersion in the mixture with regard to the combined effects of the surfactant composition and CNTs dispersed with different levels of energy. The goal of this research was to evaluate the effects of the main parameters affecting concrete sensor performance using various criteria (sensitivity of the sensor, standard deviation of the prediction error, repeatability, cross-correlation and hysteresis) in both static and dynamic loading regimes. Dynamic criteria such as sensitivity, internal repeatability, cross-correlation and hysteresis showed that the energy levels for the dispersion of CNTs have a greater effect on improving sensor performance than the amount of CNTs. On the contrary, the repeatability indicated that the amount of CNTs has a greater effect on sensor performance than the dispersion quality (energy level) of the CNTs. On the whole, the sensor produced with 0·15 wt% (by weight of cement) CNTs, superplasticiser and sodium dodecyl sulfate as a surfactant using the maximum energy level (ultrasonic bath for 2 h and 90 min of probe's ultrasonication) offered the best performance both in the static and dynamic load regimes. [ABSTRACT FROM AUTHOR]

Biocompatible and biodegradable polymers represent the future in the manufacturing of medical implantable solutions. As of today, these are generally manufactured with metallic components which cannot be naturally absorbed within the human body. This requires performing an additional surgical procedure to remove the remnants after complete rehabilitation or to leave the devices in situ indefinitely. Nevertheless, the biomaterials used for this purpose must satisfy well-defined mechanical requirements. These are difficult to ascertain at the design phase since they depend not only on their physicochemical properties but also on the specific manufacturing methods used for the target application. Therefore, this research was focused on establishing the effects of the manufacturing methods on both the mechanical properties and the thermal behavior of a medical-grade copolymer blend. Specifically, Injection and Compression Molding were considered. A Poly(L-lactide-co-D,L-lactide)/Poly(L-lactide-co-ε-caprolactone) blend was considered for this investigation, with a ratio of 50/50 (w/w), aimed at the manufacturing of implantable devices for tendon repair. Interesting results were obtained. [ABSTRACT FROM AUTHOR]

Self-healing concrete has the potential to optimise traditional design approaches; however, commercial uptake requires the ability to harmonize against standardized frameworks. Within EU SARCOS COST Action, different interlaboratory tests were executed on different self-healing techniques. This paper reports on the evaluation of the effectiveness of proposed experimental methodologies suited for self-healing concrete with expansive mineral additions. Concrete prisms and discs with MgO-based healing agents were produced and precracked. Water absorption and water flow tests were executed over a healing period spanning 6 months to assess the sealing efficiency, and the crack width reduction with time was monitored. High variability was reported for both reference (REF) and healing-addition (ADD) series affecting the reproducibility of cracking. However, within each lab, the crack width creation was repeatable. ADD reported larger crack widths. The latter influenced the observed healing making direct comparisons across labs prone to errors. Water absorption tests highlighted were susceptible to application errors. Concurrently, the potential of water flow tests as a facile method for assessment of healing performance was shown across all labs. Overall, the importance of repeatability and reproducibility of testing methods is highlighted in providing a sound basis for incorporation of self-healing concepts in practical applications. [ABSTRACT FROM AUTHOR]

• Extruded cementitious capsules are suitable to carry different healing agents. • Capsule waterproofing coating can be applied either internally or externally. • Active crack control allows to get a low crack width variability during pre-cracking. • The sealing efficiency is assessed via water flow and water absorption tests. • The sealing efficiency is up to 79% under water flow and 92% under water absorption. The intensive use of cement-based building materials is a growing concern in terms of environmental impact, since they significantly contribute to the global anthropogenic CO 2 emissions. The development of self-sealing cementitious materials could be a possible approach to improve the structural durability and thus reduce overall cost and environmental impact. In the present work, the efficiency of a self-sealing system using extruded cementitious capsules was experimentally investigated, and different healing agents were tested (specifically, a water-repellent agent, a polyurethane precursor and a solution of silica gel immobilized ureolytic bacteria). The self-sealing efficiency was evaluated in terms of capability to autonomously seal localized cracks induced in a controlled way. An active crack width control technique was adopted during the cracking procedure, in order to reduce the variation of the crack width within a series of specimens. Water permeability and capillary water absorption tests were performed to quantify the crack sealing ability, along with qualitative visual analysis of the crack faces. Positive results were achieved when using the water-repellent agent in water absorption tests, the bacterial agent in water-flow tests and the polyurethane precursor in both cases. This suggests that the proposed self-sealing system is sufficiently versatile to be used with different healing agents and that it can be effective in prolonging the material functionality by selecting the most appropriate agent for the real operating conditions. [ABSTRACT FROM AUTHOR]