An Overview on the Rheology, Mechanical Properties, Durability, 3D Printing, and Microstructural Performance of Nanomaterials in Cementitious Composites

The most active research area is nanotechnology in cementitious composites, which has a wide range of applications and has achieved popularity over the last three decades. Nanoparticles (NPs) have emerged as possible materials to be used in the field of civil engineering. Previous research has concentrated on evaluating the effect of different NPs in cementitious materials to alter material characteristics. In order to provide a broad understanding of how nanomaterials (NMs) can be used, this paper critically evaluates previous research on the influence of rheology, mechanical properties, durability, 3D printing, and microstructural performance on cementitious materials. The flow properties of fresh cementitious composites can be measured using rheology and slump. Mechanical properties such as compressive, flexural, and split tensile strength reveal hardened properties. The necessary tests for determining a NM’s durability in concrete are shrinkage, pore structure and porosity, and permeability. The advent of modern 3D printing technologies is suitable for structural printing, such as contour crafting and binder jetting. Three-dimensional (3D) printing has opened up new avenues for the building and construction industry to become more digital. Regardless of the material science, a range of problems must be tackled, including developing smart cementitious composites suitable for 3D structural printing. According to the scanning electron microscopy results, the addition of NMs to cementitious materials results in a denser and improved microstructure with more hydration products. This paper provides valuable information and details about the rheology, mechanical properties, durability, 3D printing, and microstructural performance of cementitious materials with NMs and encourages further research.

Advantages of Contour Crafting in Construction Applications

: Contour crafting application has been widely used in different industrial, pharmaceutical, medical, and aviation application for more than three decades. Recently, mega-sized 3-D printers were developed, with sufficient capability to print full scale construction projects, including walls, homes, bridges, and multi-story buildings. Successful 3-D printing of projects is accomplished by additive manufacturing (AM) process through the placement of successive layers of construction materials using robotic arms (3-D printers). This layered construction, known as contour crafting, is controlled by computer modelling software. This paper presents the history of contour crafting development, its current application in construction, the advantages of contour crafting applications in construction, and the main impediments to the wide spread of contour crafting in the local construction market. In addition, this paper highlights the current research efforts made to integrate building information modeling (BIM) in contour crafting construction. Based on the recent research findings, contour crafting application in construction improves job site productivity and project sustainability as a result of reduced material waste in construction sites. Finally, the automated construction through the application of contour crafting technique results in improved job site safety and increased overall quality of construction projects due to the increased automation in construction.

Desarrollo de Morteros Sostenibles para su Aplicación en Impresión 3D

En el presente trabajo, correspondiente a la tesis doctoral en curso, se darán a conocer algunos resultados de ensayos mecánicos y físicos de distintos tipos de morteros de geopolímeros y de cemento, cuya finalidad es ser utilizados como material aditivo en una impresora 3D, tipo contour crafting. Los morteros de geopolímeros empleados se componen de fly ash, como precursor, disolución alcalina, como activador, árido calizo, vidrio triturado y conchas marinas, como árido y aditivos. Los morteros de cemento, como su nombre lo indica, se componen de cemento, adiciones, aditivos y distintos áridos (arena caliza, vidrio triturado y conchas marinas). Los ensayos mecánicos corresponden a flexión y compresión en probetas prismáticas de 4 x 4 x 16 cm. Los morteros de geopolímero fueron curados en diferentes condiciones (a temperatura ambiente, en agua -de mar y de grifo- y en estufa a 40 ºC) y se expusieron a diferentes ambientes (ambiente de laboratorio e inmersos en agua); en tanto que los morteros de cemento se curaron a temperatura ambiente y en agua (de mar y de grifo). Se imprimieron elementos de diferentes tamaños, formas y complejidades para comprobar su efectividad como material aditivo, obteniéndose comportamientos satisfactorios. Los resultados mecánicos muestran que los morteros siguen adquiriendo resistencia hasta los 90 días, para cementos y 60 días para geopolímeros; estos últimos presentan menor resistencia comparados con los cementos, los cuales registraron valores entorno a los 70 MPa para los que contienen árido calizo y vidrio triturado, curados en agua.

Role of Polymers in 3D Printing Technology for Drug Delivery - An Overview

Background: 3D printing (3DP) is an emerging technique for fabrication of a variety of structures and complex geometries using 3D model data. In 1986, Charles Hull introduced stereolithography technique that took advances to beget new methods of 3D printing such as powder bed fusion, fused deposition modeling (FDM), inkjet printing, and contour crafting (CC). Being advantageous in terms of less waste, freedom of design and automation, 3DP has been evolved to minimize incurred cost for bulk production of customized products at the industrial outset. Due to these reasons, 3DP technology has acquired a significant position in pharmaceutical industries. Numerous polymers have been explored for manufacturing of 3DP based drug delivery systems for patient-customized medication with miniaturized dosage forms. Method: Published research articles on 3D printed based drug delivery have been thoroughly studied and the polymers used in those studies are summarized in this article. Results: We have discussed the polymers utilized to fabricate 3DP systems including their processing considerations, and challenges in fabrication of high throughput 3DP based drug delivery systems. Conclusion: Despite several advantages of 3DP in drug delivery, there are still a few issues that need to be addressed such as lower mechanical properties and anisotropic behavior, which are obstacles to scale up the technology. Polymers as a building material certainly plays crucial role in the final property of the dosage form. It is an effort to bring an assemblage of critical aspects for scientists engaged in 3DP technology to create flexible, complex and personalized dosage forms.

Effects of mixture ingredients on extrudability of concrete in Contour Crafting

Purpose This paper aims to investigate the extrudability (flow-ability and shape-stability) of concrete mixtures by using contour crafting (CC) as an automated construction process. Design/methodology/approach Several experiments have been performed for flow-ability and shape-stability of concrete mixtures. Experimental results were compared to understand significant factors and their interactions. After developing the empirical model for flow-ability, the model was validated. Findings The experimental investigation of varied combination of concrete components developed a mixture within constrains of the CC nozzle and improved the quality of the extruded part. Originality/value Several experimental samples were fabricated using CC, and the derived empirical model was validated after more than 700 h of work.