Characterization of material for civil engineering

Materials are the heart of engineering, which can be defined as the creative and rational use of materials for practical purposes. Materials have had an essential role in the development of civil engineering: from the beginning of human evolution, man has used many different materials to build houses, bridges, roads and countless other structures to make his life easier. Ancient populations used the raw materials at their disposal, such as stone, clay and timber. Over the centuries, the search for new materials became increasingly important to respond to changing human needs, and men learned how to use clay to form artificial stones, cements and concretes, for instance. While hands-on familiarity rooted in tradition and crafting expertise initially drove these human activities, in modern times the need for a scientific understanding of materials prompted the birth of the material science discipline. Material science studies the composition, behavior and properties of materials to solve problems associated with their use. Engineering and material science work together to create functional, durable and beautiful structures. Among the materials used in civil engineering constructions, wood and cement have had the most important role over the centuries and they are still the main components of our infrastructures. Timber was used as a building material even by primitive man, and a few ancient temples, palaces and bridges built of wood can still be seen today. In the 20th century, although materials such as concrete had become competitive, wood retained its significant role in building. The main problem with the use of wood as a construction material concerns its possibly limited lifetime. Wood is characterized by a limited resistance to moisture and fire, the two elements responsible for the destruction of most wooden buildings in the past. Cement, and consequently concrete, is the most often used material today. The term “cement” is now used to mean a modern binder, the so-called Portland cement, patented in England in 1824. Similar binding materials were already being used from very early on ancient Mesopotamia, Egypt, Greece and Rome. Modern cement formulations have changed a great deal and can be adapted to their intended use and the surrounding environment

Properties of anion exchange membrane based on polyamine: Effect of functionalized silica particles prepared by sol–gel method

Membranes of polyamine (PA-SiNH2)m, containing silica reacted with 3-aminopropyltriethoxysilane (APTES) in hydrolytic conditions were prepared via solution casting, followed by methylation and ion exchange process. The influence of amino-functionalized silica (Si-NH2) on the properties of the obtained membrane was investigated. Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance spectroscopy (NMR) were used to investigate the chemical features of the silica and its interaction with the polyamine polymer. The results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) of the modified membrane confirmed it is stable up to 300 °C. The thermal stability is the result of the interaction of modified silica particles and polyamine polymer. It was demonstrated that the performance of the (PA-SiNH2)m anion exchange membrane is greatly improved by incorporation of silica nanoparticles as compared with the anion exchange membrane (PK-PDAPm), which doesn't contain silica. Therefore, the (PA-SiNH2)m is a suitable candidate for electrochemical applications

Comb-Shaped Polymers as Nanostructure Modifiers of Calcium Silicate Hydrate: A ²⁹Si Solid-State NMR Investigation

Calcium silicate hydrate gel (C–S–H) is the complex phase mostly responsible for the binding properties and the mechanical resistance of Portland cement. The clarification of the C–S–H nanostructure and how the presence of organic additives affects it is still an intriguing and not trivial task, especially due to C–S–H scarce crystallinity and intrinsic complexity. In this work, we exploited ²⁹Si solid-state nuclear magnetic resonance (NMR) to investigate the effects of different comb-shaped superplasticizers on the silicate structure. The analysis of ²⁹Si solid-state NMR spectra shows that the additives increase the degree of polymerization and hence the average length of the silicate chains in C–S–H. This finding correlates well with the increase of the globule dimensions estimated by means of small angle scattering techniques showing that the comb-shaped polymers are able to tune the overall dimension of the C–S–H globule. This effect is dependent on the molecular architecture of the superplasticizer and allows a molecular imprinting to the globular structure of the C–S–H gel

(I/O) Hybrid Alkoxysilane/Zirconium-Oxocluster Copolymers as Coatings for Wood Protection

Novel inorganic–organic hybrid copolymers based on vinyl- or (3-mercaptopropyl)-trimethoxysilane and an organically modified zirconium-oxocluster were investigated as a wood preservation treatment. The copolymers were prepared using a modified sol-gel strategy not involving alkoxysilane pre-hydrolysis and were applied on wood through a dip coating method. Even though the copolymers were mainly present on the surface of the wood, EDX analysis showed also a uniform distribution of silicon and zirconium in the cell wall but not in the lumina. The grafting of the copolymers on wood was confirmed through FTIR, ¹³C and ²⁹Si MAS NMR analysis. The copolymer obtained from (3-mercaptopropyl)­trimethoxysilane was post-functionalized with the methacrylic ester of thymol; introduced for testing as a biocide. Preliminary accelerated biological tests against the brown rot fungus <i>Coniophora puteana</i>, showed resistance to the fungus for the samples coated with the vinyltrimethoxysilane copolymer, while uneven results were obtained for the samples coated with the (3-mercaptopropyl)­trimethoxysilane copolymer, even when functionalized with the ester of thymol

Preparation, structure and properties of hybrid materials based on geopolymers and polysiloxanes

New hybrid materials with no phase separation up to nanometric level were obtained by performing the in situ co-reticulation of an aluminosilicate source (metakaolin), a mixture of dialkylsiloxane oligomers with different degrees of polymerization and an alkaline solution. As supported by SEM and NMR analyses, these hybrid materials are characterized by a highly interpenetrated structure due to the chemical similarity between the components, resulting in excellent physical and mechanical properties compared to neat geopolymers. These promising results represent a further step in developing alternative low-carbon binders (as also geopolymers) with improved engineering properties in the concrete technology. The enhanced mechanical properties, along with the high fire resistance, also suggest their utilization for structural applications as heat insulating and heat-resistant panels for the construction industry, and in the production of heat-resistant protective coatings or adhesives for technologically advanced uses

Chloride-based route for monodisperse Cu<inf>2</inf>ZnSnS<inf>4</inf> nanoparticles preparation

A new approach based on hot injection method is proposed to gram-scale Cu2ZnSnS4 nanoparticles production minimizing the use of organic solvents. Nanocrystal synthesis was performed starting from metal chlorides and pure sulphur powder and using Oleylamine as capping agent. As a result, core-shell nanoparticles with a narrow size distribution were obtained

Hydrorepellent finishing of cotton fabrics by chemically modified TEOS based nanosol

Hydrorepellency was conferred to cotton fabrics by an hybrid organic-inorganic finishing via sol-gel. The nanosol was prepared by co-hydrolysis and condensation of tetraethoxysilane (TEOS) and 1H,1H,2H,2H-fluorooctyltriethoxysilane (FOS), or hexadecyltrimethoxysilane (C16), as precursors in weakly acid medium. The application on cotton was carried out by padding with various impregnation times, followed by drying and thermal treatment, varying the FOS add-on from 5 till 30 % on fabric weight or C16 add-on from 5 to 10 %. Treated samples were tested in terms of contact angles, drop absorption times, washing fastness and characterized by SEM, XPS and FTIR-ATR analyses. In the case of FOS modified nanosol applied with an impregnation time of 24 h or C16 modified nanosol, water contact angles values very close or even higher than 150° were measured, typical of a superhydrophobic surface. The application of the proposed sol-gel process yielded also a satisfactory treatment fastness to domestic washing, in particular for FOS modified nanoso