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The purpose of the study is regarding the development of eco-oriented technologies for obtaining the building gypsum materials with the involvement of industrial by-products or waste.

The scanning electron microscopy, X-ray microanalysis and IR spectral analysis were used to study the structure of gypsum matrix. The method of comparison of modified and unmodified gypsum matrix was used. Physical modeling of gypsum matrix crystallization is used to study changes in the morphology of hydration products.

The experimental results show that the addition of technical soot into a gypsum binder leads to a change in the morphology of crystalline hydrates of calcium sulfate dihydrate. Results of the scanning electron microscopy, X-ray microanalysis and IR spectral analysis confirm the change of physical and mechanical characteristics of the gypsum binder due to the structural modification of the gypsum matrix with ultrafine carbon soot. The achieved degree of the structural modification of the gypsum matrix is compatible with the results obtained when the gypsum binder was modified with dispersions of carbon nanotubes.

The morphology of the crystalline hydrates of the gypsum matrix with the addition of 0.04%, 0.06% and 1% of the carbon soot is characterized by the transition of the classical needle-like structure of gypsum dihydrate to the lamellar structure of increased density. One can observe the formation of intergrowths around ultrafine carbon soot particles. The studied carbon additive can improve strength characteristics of the gypsum matrix.

The purpose of present paper is to enlarge the knowledge about the performance of gypsum powder to realize complex molds or cores for aluminum casting.

The research was divided into two activities: simple; and complex-part production capability. In the simple-part step, the performance of gypsum powder and the minimum mold thickness that would withstand the casting process. In the complex-part step, the authors first investigated the powder removability as a function of geometry complexity and then binder jetting performance was evaluated for the case of lattice-structure fabrication.

All the geometries tested withstand the casting process demonstrating the benefits in terms of complexity part design; however, the process suffers of all the typical defect of casting as misrun, porosity and cold shut.

The results found in this research improve the benefits related to additive manufacturing application in industrial environment and in particular to the binder jetting technology and the rapid casting approach.

The purpose of this study is to quantify the vertical shrinkage rates and the mechanical strength of three-dimensional (3D) printed parts for a variety of wood-based materials for liquid deposition modeling.

The overall hypothesis was that a well-chosen combination of binders, fibers and fillers could reduce shrinkage in the Z dimension and increase compressive and flexural strength (DIN 52185, 52186). To test this assumption, eight sub-hypotheses were formulated. Mixtures of the ingredients were chosen in different ratios to measure the performance of prints. For time efficiency, an iterative heuristic approach was used – not testing all variations of all variables in even increments, but cutting off lines of testing when mixtures were clearly performing poorly.

The results showed that some mixtures had high dimensional accuracy and strength, while others had neither, and others had one but not the other. Shrinkage of 3D printed objects was mainly caused by water release during drying. An increase of the wood as well as the cement, sand, salt and gypsum content led to reduced vertical shrinkage, which varied between 0 and 23%. Compressive and flexural strength showed mixed trends. An increase in wood and salt content worsened both strength properties. The addition of fibers improved flexural, and the addition of cement improved compression strength. The highest strength values of 14 MPa for compressive and 8 MPa for flexural strength were obtained in the test series with gypsum.

This paper is an important milestone in the development of environmentally friendly materials for additive manufacturing. The potential of many ingredients to improve physical properties could be demonstrated.

The purpose of this study was to prepare water-based binders, which aimed to avoid printhead blockage and to improve dimensional accuracy of inkjet 3D printing (3DP) technology, and a feasible algorithm of full-color printing was realized.

A self-developed color 3D printer was made by using a piezoelectric printhead of Epson Dx-5. Several water-based binders and corresponding gypsum composite powders were prepared, and the optimum binder-powder assembly was then determined through elementary adhesive testing and roller paving testing. Full-color printing was implemented based on halftoning algorithms that used different threshold matrices for different ink channels, and the performances of various algorithms were evaluated in terms of both subjective and objective indices.

The optimum binder-powder assembly can solve the jamming problem of printhead and realize agreeable dimensional accuracy with the relative error less than 2.5% owing to the satisfying boundary diffusion control ability. And the determined halftone algorithm was verified to be agreeable for 3D color printing.

The prepared approach of water-based binders and gypsum composite powders can be applied to similar 3DP systems even if different materials are introduced. And the used halftone algorithms provide feasible guidelines to the implementation of 3D full-color printing.

Evaluating mechanical properties of simply made samples by 3D printing technology at nanoscale provides a clear path to better understand larger-scale responses of complex natural rocks. Therefore, to realize the similarity between synthetically manufactured materials and natural geomaterials, this study focused on nanoscale mechanical characterization of a 3D printed object with only two constituent components (gypsum powder and infiltrant).

The study method includes nanoindentation technique combined with numerical simulation via discrete element method (DEM).

Four typical load-displacement curves were identified from nanoindentation of total test points indicating a typical elastic-plastic behavior of the 3D printed gypsum rock sample. Mechanical parameters such as Young’s modulus and hardness were calculated by energy-based methods and a positive correlation was observed. The infiltrant was found to considerably be responsible for the majority of the sample nano-mechanical behavior rather than the gypsum particles, thus expected to control macroscale properties. This was decided from deconvolution and clustering of elastic modulus data. Particle flow modeling in DEM was used to simulate the nanoindentation process in a porous media yielding rock-alike mechanical behavior.

The results show a matching load-displacement response between experimental and simulation results, which verified the credibility of simulation modeling for mechanical behavior of 3D printed gypsum rock at nanoscale. Finally, differential effective medium theory was used to upscale the nanoindentation results to the macroscale mechanical properties, which provided an insight into the geomechanical modeling at multiscale.

The aim of this paper is to determine the thermal conductivity of a protective layer of alkali-activated cement and the possibility of performing fire protection with fireclay sand and Lightweight mortar. Unprotected steel structures have generally low fire resistance and require surface protection. The design of passive protection of a steel element must consider the service life of the structure and the possible need to replace the fire protection layer. Currently, conventional passive protection options include intumescent coatings, which are subject to frequent inspection and renewal, gypsum and cement-based fire coatings and gypsum and cement board fire protection.

Alkali-activated cements provide an alternative to traditional Portland clinker-based materials for specific areas. This paper presents the properties of hybrid cement, its manufacturability for conventional mortars and the development of passive fire protection. Fire experiments were conducted with mortar with alkali-activated and fireclay sand and lightweight mortar with alkali-activated cement and expanded perlite. Fire experiment FE modelling.

The temperatures of the protected steel and the formation of cracks in the protective layer were investigated. Based on the experiments, the thermal conductivities of the two protective layers were determined. Conclusions are presented on the applicability of alkaline-activated cement mortars and the possibilities of applicability for the protection of steel structures. The functionality of the passive fire layer was confirmed and the strengths of the mortar used were determined. The use of alkali-activated cements was shown to be a suitable option for sustainable passive fire protection of steel structures.

Eco-friendly fire protection based on hybrid alkali-activated cement of steel members.

Fixed structures in prosthetic dentistry are highly customized products, manufactured individually for patients who have missing teeth. When choosing the technology for fixed dental structure manufacturing, three viable options are available (precise casting, milling and selective laser melting [SLM]). All these technologies can be used to produce a dental structure from CoCr alloy. Besides materials and availability of technologies, economic efficiency is an important factor when choosing a production method. The purpose of this study is to develop an estimation model for achievable productivity of selective laser melting and compare the results with the productivity of conventional manufacturing.

Results presented in this paper are based on manufacturing time analysis of an individual case with each of the technologies mentioned above. Because of the efficiency of SLM is highly dependent on how efficiently the work space of the machine is used, this issue was also included in the research. Data used for research were acquired from practical use of each technology in dental applications.

Analysis of achievable SLM manufacturing speeds is based on the previous research into manufacturing speeds of additive manufacturing technologies. The presented results present a model that can be used to estimate the productivity of the SLM technology.

Research was limited to a specific SLM machine type with a fixed workspace volume. Nevertheless, the results show that any SLM machine has to be used as efficiently as possible to be able to be competitive regarding the conventional manufacturing technologies.

The presented results show clearly at least a rough estimation of what kind of parts and in what volume will be manufactured with an SLM machine prior to buying one.

Results can help to widen the economically efficient way of running SLM machines, replacing conventional manufacturing for medical applications especially with complicated cases.

A method is presented to adapt the estimation model to a particular real-life production scenario. This method can be used to establish how efficiently selective laser sintering can be used and if using SLM machine instead of conventional manufacturing would be economically viable.

This paper aims to present a new curing protocol which improves part strength and provides better repeatability for full-part infiltration by varying binder saturation levels. The fully infiltrated parts were then investigated for their resistance to water.

Cylinders and spheres generated using various curing procedures and binder saturation levels were subjected to uniaxial compression to determine the effects on the resulting part strength. Additionally, fully cured parts were submerged in water for varying durations to determine the resistance to water. Parts were also weighed prior to and after submersion in water to determine any change in mass.

Increased part infiltration and improved strength were achieved using a modified curing protocol with a higher oven temperature during curing. Spheres cured following the modified curing protocol resulted in a 300 per cent increase in the average force required to crush spheres. Parts were shown to have repeatable infiltration depths from 8.8 mm to 10.1 mm. Additionally, fully cured parts submerged in water for durations longer than 12 hours developed a reduction in strength.

This study provides key methods to improve part strength and demonstrates a limitation on maximum dimensions of parts which should be considered to behave homogeneously. Parts generated following these guidelines can be effectively used in laboratory and engineering applications where high strength and homogeneous behavior is important.

The purpose of this paper is to study the effect of different parameters (layer thickness, jetted binder volume per layer and type of binder and temperature) on the mechanical properties of parts made with an experimental 3D printing (3DP) process. This 3DP device built for this project is based on the spiral growth manufacturing (SGM) device previously introduced by Hauser et al. at The University of Liverpool. It differs from the common 3DP in that it generates the different parts using only one rotating piston instead of two non‐rotating ones.

Several parts are produced using this device according to an experimental design, repeating each run three times. The experimental machine is able to make every part needed without major issues, demonstrating that it is possible to build a functional device using common and standard components.

Experimental analysis of the printed parts shows that the layer thickness has the highest effect on apparent density, hardness and fracture strength of the parts made.

Empirical information is provided about mechanical behavior (e.g. apparent density, hardness and fracture strength) of parts made under different processing factors (e.g. binder type, layer thickness, quantity of binder and chamber temperature) using a SGM‐based 3DP experimental device.

The paper seeks to bridge the already familiar benefits of 3D printing (3DP) to the rehabilitation of cultural heritage, still based on the use of complex and expensive handcrafted techniques and scarce materials.

A compilation of different information on frequent anomalies in cultural heritage buildings and commonly used materials is conducted; subsequently, some innovative techniques used in the construction sector (3DP and 3D scanning) are addressed, as well as some case studies related to the rehabilitation of cultural heritage building elements, leading to a reflection on the opportunities and challenges of this application within these types of buildings.

The compilation of information summarised in the paper provided a clear reflection on the great potential of 3DP for cultural heritage rehabilitation, requiring the development of new mixtures (lime mortars, for example) compatible with the existing surface and, eventually, incorporating some residues that may improve interesting properties; the design of different extruders, compatible with the new mixtures developed and the articulation of 3D printers with the available mapping tools (photogrammetry and laser scanning) to reproduce the component as accurately as possible.

This paper sets the path for a new application of 3DP in construction, namely in the field of cultural heritage rehabilitation, by identifying some key opportunities, challenges and for designing the process flow associated with the different technologies involved.