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Additive manufacturing (AM) is the term for a number of processes for joining materials to build physical components from a digital 3D model. AM has multiple advantages over other construction techniques, such as freeform, customization, and waste reduction. However, AM components have been evaluated by destructive and non-destructive testing and have shown mechanical issues, such as reduced resistance, anisotropy and voids. The build direction affects the mechanical properties of the built part, including voids of different characteristics. The aim of this work is an extended analysis of void shape by means of X-ray computed tomography (CT) applied to fused deposition modeling (FDM) samples. Furthermore, a relation between the tensile mechanical properties and digital void measurements is established. The results of this work demonstrate that void characteristics such as quantity, size, sphericity and compactness show no obvious variations between the samples. However, the angle between the main void axis and the mechanical load axis α shows a relation for FDM components: when its mean value μ(α) is around 80 (degrees) the yield strength and Young’s modulus are reduced. These results lead to the formulation of a novel criterion that predicts the mechanical behavior of AM components.

The experimental setup is devised to simulate the presence of vertical cracks with varying widths within concrete structures. Co-polarimetric ground-penetrating radar (GPR) surveys are carried out to acquire the “VV” and “HH” polarization data. The time-varying centroid frequency attribute is employed to describe the vertical variation in the center frequency of the radar wave, unveiling a gradual vertical decay in the centroid frequency at the locations of vertical cracks. An improved time-varying centroid frequency attribute based on the adaptive sparse S-transform (ASST) is proposed and tested by a finite-difference time-domain model and co-polarimetric GPR data, which can offer better resolution compared to that of the conventional S-transform. By analyzing the waveform and centroid frequency properties of the two polarizations, we conclude that the “VV” polarization is relatively sensitive to centimeter scale cracks, while the “HH” polarization is more sensitive to millimeter scale cracks.

This study aimed to experimentally investigate the compressive strength and air voids of cement pastes with varying dosages of Superabsorbent Polymer (SAP) and water-to-cement (w/c) ratios. Cement pastes were prepared using three different w/c ratios of 0.4, 0.5, and 0.6, along with different dosages of SAP ranging from 0.2% to 0.5% by weight of cement. Additionally, SAP was introduced in two forms: dry and wet. After casting the cubes, two distinct curing conditions were employed: curing at a temperature of 20 °C with a Relative Humidity (RH) of 60% (Curing 1), and water curing (Curing 2). The results revealed that the addition of SAP increased early strength when subjected to Curing 1, followed by a decrease in later strength. On the other hand, samples with SAP and water curing exhibited higher strength compared to those without SAP, especially with w/c ratios of 0.4 and 0.5. However, at a w/c ratio of 0.6, nearly all samples showed a reduction in strength compared to those without SAP. Furthermore, air void analysis was performed on all samples cured for 28 days using an image analysis technique. The samples containing wet SAP resulted in a higher total air content compared to the samples with dry SAP. Additionally, the incorporation of wet SAP in cement paste led to lower specific surface areas and a higher spacing factor than the samples with dry SAP. These findings suggest that the clumping of wet SAP particles during presoaking resulted in coarser air voids compared to the samples containing dry SAP.

Recent studies have shown promising potential for using Glass Pozzolan (GP) as an alternative supplementary cementitious material (SCM) due to the scarcity of fly ash and slag in the United States. However, comprehensive studies on the freeze–thaw (FT) resistance and air void system of mixtures containing GP are lacking. Therefore, this study aimed to evaluate GP’s effect on FT resistance and characterize mixtures with different GP contents, both macro- and microscopically. In this study, six concrete mixes were considered: Three mixes with 20%, 30% and 40% GP as cement replacements and two other comparable mixes with 30% fly ash and 40% slag, as well as a mix with 100% Ordinary Portland cement (OPC) as a reference. Concrete samples were prepared, cured and tested according to the ASTM standards for accelerated FT resistance for 1000 cycles and corresponding dynamic modulus of elasticity (Ed). All the samples showed minimal deterioration and scaling and high F/T resistance with a durability factor of over 90%. The relationships among FT resistance parameters, air-pressured method measurements of fresh concretes and air void analysis parameters of hardened concretes were examined in this study. X-ray micro-tomography (micro-CT scan) was used to evaluate micro-cracks development after 1000 freeze–thaw cycles and to determine spatial parameters of air voids in the concretes. Pore structure properties obtained from mercury intrusion porosimetry (MIP) and N2 adsorption method showed refined pore structure for higher cement replacement with GP, indicating more gel formation (C-S-H) which was verified by thermogravimetric analysis (TGA).

Polymorphism is a prevalent occurrence in pharmaceutical solids and demands thorough investigation during product development. This paper delves into the crystal growth and structure of a newly synthesized polymorph (TPT)2[CoII(NCS)4], (1), where TPT is triphenyl tetrazolium. The study combines experimental and theoretical approaches to elucidate the 3D framework of the crystal structure, characterized by hydrogen-bonded interactions between (TPT)+ cations and [Co(NCS)4]2− anions. Hirshfeld surface analysis, along with associated two-dimensional fingerprints, is employed to comprehensively investigate and quantify intermolecular interactions within the structure. The enrichment ratio is calculated for non-covalent contacts, providing insight into their propensity to influence crystal packing interactions. Void analysis is conducted to predict the mechanical behavior of the compound. Utilizing Bravais-Friedel, Donnay-Harker (BFDH), and growth morphology (GM) techniques, the external morphology of (TPT)2[CoII(NCS)4] is predicted. Experimental observations align well with BFDH predictions, with slight deviations from the GM model. Quantum computational calculations of the synthesized compounds is performed in the ground state using the DFT/UB3LYP level of theory. These calculations assess the molecule’s stability and chemical reactivity, including the computation of the HOMO-LUMO energy difference and other chemical descriptors. The study provides a comprehensive exploration of the newly synthesized polymorph, shedding light on its crystal structure, intermolecular interactions, mechanical behavior, and external morphology, supported by both experimental and computational analyses.

The great potential of Extrusion Additive Manufacturing (EAM) for structural prototyping in the automotive industry is severely limited by the directional bias in the build direction. The layerwise fabrication leads to reduced mechanical properties at the layer-to-layer interface compared to the bulk of the strand. Especially for the often-used semi-crystalline thermoplastics, the mechanical properties strongly depend on the processing parameters, even more so if short fibers are used as fillers. Therefore, ideal processing windows in which the mechanical strength and modulus in the z-direction reach their maximum can be identified for these parameters, resulting in a reduced directional bias. The influence of the EAM processing parameters on mechanical strength has already been investigated, correlating strength with thermal conditions during printing. However, these considerations did not distinguish between the thermal effect on the polymer properties, the formation of voids and pores at the layer interface, and the resulting fiber orientation for different strand proportions. Therefore, in this study, the effect of different processing temperatures and layer heights on the pore size and distribution, as well as the fiber orientation in the different regions of the mesostructure was investigated using X-ray Computed Tomography (XCT).

This article presents the results of fatigue testing and assessment of the mechanical and physical properties of the concrete pavement of the A6 motorway, which was put in service in 1938. After 82 years of operation under heavy traffic loading conditions, the pavement was fully recycled by crushing of the existing concrete and reuse of the reclaimed material in the new courses of pavement placed as part of the motorway renewal project. The main objective of this research was to determine the properties of the tested concrete, including compressive strength, water absorption and freeze-thaw resistance after 150 cycles of alternate freezing and thawing. The resistance of the concrete to the action of de-icing products was also checked. The article also presents the results of petrographic analysis of the aggregates. Additionally, concrete sampled from the pavement was evaluated for freeze-thaw resistance in relation to the determined porosity characteristics. The tested concrete, which was subjected to over 80 years of traffic loading on the A6 motorway, was found to meet the highest requirements as currently applied for the extra heavy-duty pavements. With a compressive strength value in excess of 50 MPa, the tested concrete can be rated at least CC40, according to EN 13877-2:2013-08. The samples were found to satisfy the freeze-thaw resistance requirements of an F150 rating. The air void analysis showed that the analyzed concrete contained 1.6% of micropores, i.e., air voids smaller than 300 μm (A300). The spacing factor, in turn, was below 0.200 mm (L = 0.185 mm). The example of the A6 motorway renewal project served to demonstrate that reclaimed concrete aggregate, obtained by crushing the entire pavement, can be used for production of the new pavement courses.

Manufacturing is a significant process for the engineering industries to convert raw materials into a complete product. Apart from other manufacturing processes, forming is one of the efficient methods to develop the product. Single Point Incremental Forming [SPIF] process is a forming method that can produce components with reduced die cost compared to other conventional forming methods but it has a drawback of consuming more time to complete the forming process. A new multipoint tool is proposed in this paper to overcome the drawback by reducing the processing time and resulting high quality product. In addition, the newly designed multipoint tool improvises the formability of the sheet metal with good surface finish. The Austenitic stainless steel of grade 202 is used to compare the outputs obtained during Multi-Point Incremental Forming [MPIF] process and SPIF process. The formability of the sheet metal is evaluated along with the surface roughness using the Forming Limit Diagram [FLD] and void analysis. The roughness value of the sheet metals formed were analysed using the Three Dimensional (3D) surface roughness tester. Based on the results obtained, it is identified that higher formability and better surface finish are obtained by multipoint forming tool compared to single point forming tool.

In many applications, voids in metals are observed as early degradation features caused by fatigue. In this publication, electropolishing is presented in the context of a novel sample preparation method that is capable of accessing voids in the interior of metal thin films along their lateral direction by material removal. When performed at optimized process parameters, material removal can be well controlled and the surface becomes smooth at the micro scale, resulting in the voids being well distinguishable from the background in scanning electron microscopy images. Compared to conventional cross-sectional sample preparation (embedded mechanical cross-section or focused ion beam), the accessed surface is not constrained by the thickness of the investigated film and laterally resolved void analyses are possible. For demonstrational purposes of this method, the distribution of degradation voids along the metallization of thermo-mechanically stressed microelectronic chips has been quantified.

Durability and long-term performance of concrete exposed to deleterious ions and environmental conditions are major concerns. The rapid chloride permeability (RCP) test is commonly used in specifications in the United States to evaluate the permeability of concrete. To evaluate the critical factors that control the service life of structures, the investigation of various concrete mixtures is required. In this paper, the performance of 54 concrete mixtures containing three types of water-reducing admixtures, two types of aggregates, and two levels of cement contents are evaluated in the RCP and freezing-and-thawing tests and the air void structure of selected mixtures are analyzed. It was found that the use of supplementary cementitious materials (SCMs) significantly enhances the performance of concrete mixtures in the RCP test. In addition, mixtures containing up to 30% of Class C fly ash and 50% slag content achieved exceptional durability performance in both RCP and freezing-and-thawing (F-T) tests. The \"very-low\" RCP values were found for mixtures containing Class F fly ash and polycarboxylate ether (PCE) admixture. Keywords: air void analysis; chemical admixtures; durability; freezing and thawing (F-T); rapid chloride permeability (RCP); supplementary cementitious materials (SCMs).