Materiales activados alcalinamente a base de residuos de vidrio y escoria para aislamiento térmico y acústico

Porous alkali activated materials (AAM), can be obtained from waste glass powder and slag mixtures by alkali activation with NaOH solution. To obtain an adequate porous microstructure, the hardened AAM pastes were thermally treated at temperatures ranging between 900°C and 1000°C, for 60 or 30 minutes. Due to the intumescent behaviour specific for this type of materials, an important increase of the volume and porosity occurs during the thermal treatment. The partial substitution of waste glass powder with slag, determines the increase of compressive strength assessed before (up to 37 MPa) and after (around 10 MPa) thermal treatment; the increase of slag dosage also determines the increase of the activation temperature of the intumescent process (above 950°C). The high porosity and the specific microstructure (closed pores with various shapes and sizes) of these materials recommend them to be utilised as thermal and acoustical insulation materials.Los materiales activados alcalinamente porosos (AAM) se pueden obtener a base de polvo de residuos de vidrio y mezclas de escoria mediante activación alcalina con una solución de hidróxido de sodio (NaOH). Para obtener una microestructura porosa adecuada, las pastas de AAM endurecidas se trataron térmicamente a temperaturas que oscilan entre 900°C y 1000°C durante 60 o 30 minutos. Debido al comportamiento intumescente específico de este tipo de material, se produce un aumento significativo en el volumen y la porosidad durante el tratamiento térmico. La sustitución parcial del polvo de residuos de vidrio por escoria conlleva un aumento en las resistencias a compresión previamente evaluadas (hasta 37 MPa) y después (aproximadamente 10 MPa) del tratamiento térmico; el aumento de la dosis de escoria también determina el aumento de la temperatura de activación del proceso intumescente (por encima de 950°C). La alta porosidad y la microestructura específica de estos materiales recomiendan que se utilicen como materiales de aislamiento térmico y acústico

Steel corrosion behavior in light weight fly-ash based Alkali activated mortars

Alkali activated materials as possible sustainable alternative to cementitious binders showed competitive performances in terms of mechanical and durability properties and high temperature stability. For this reason, light weight fly-ash based mortars have already been optimized as passive fire protective coating for steel structures. However, a lack of information about the durability of these innovative systems in terms of steel corrosion resistance is still present. Thus, this study aims at investigating the durability of steel coated with a 20-mm thick light weight mortar layer in a neutral environment (tap water) and in presence of chloride-containing solution (0.2 M NaCl). In addition, the influence of pore solution chemistry and pH was discussed through electrochemical testing in leachate pore solution and NaOH aqueous solutions at different concentrations. It was found that almost complete protection ability of light weight mortar was obtained when coated steel is exposed to neutral solution for 60 days, while in presence of chlorides, steel is more susceptible to corrosion already after 40 days of exposure. In addition, the developed open porosity of the light weight mortars, it was found that pH and the chemistry of the pore solution in contact with steel strongly influenced the steel corrosion resistance

Cement-free building materials: mix design and properties in view of their application in civil engineering

This PhD thesis deals with a new class of cement-free building materials known as geopolymers, obtained through the reaction of a low-calcium solid aluminosilicate source in alkaline conditions. With the aim to go forward on the research on geopolymers and to pursuit sustainable products, this thesis focuses on low-calcium coal fly ash geopolymers activated at room temperature. By varying the type of aggregates, it was possible to test and characterize traditional and lightweight mortars as well as composites for different areas of application. In view of developing products potentially ready for the market, geopolymers were produced, characterized and tested according to the conventional procedures used for cementitious binders. A preliminary investigation of using commercially available superplasticizers to improve the workability of geopolymer mortars and to facilitate the in-situ applications was carried out. The research was then dedicated to the development and characterization of fibre reinforced geopolymer matrix (FRGM) composites for strengthening existing reinforced concrete and masonry structures. An extensive study of thermal properties and high temperature behaviour of geopolymers was reported. The mechanism of cracking induced by high temperature exposure was studied. Afterwards, composites containing recycled refractory particles were developed to enhance the thermal dimensional stability of geopolymers. Furthermore, lightweight mortars were obtained using expanded perlite as fine lightweight aggregate and studied as passive fire protection systems for steel elements. Fly-ash based geopolymers proved to be versatile materials that can be tailored according to the desired final performances. The experimental findings highlighted that in all the investigated cases, optimized fly ash-based geopolymers resulted promising and competitive products. In particular, geopolymers used as both FRGM composites and fireproofing materials showed performances comparable and in some cases better than those of commercial products currently used in these fields

The Improvement of Durability of Reinforced Concretes for Sustainable Structures: A Review on Different Approaches

The topic of sustainability of reinforced concrete structures is strictly related with their durability in aggressive environments. In particular, at equal environmental impact, the higher the durability of construction materials, the higher the sustainability. The present review deals with the possible strategies aimed at producing sustainable and durable reinforced concrete structures in different environments. It focuses on the design methodologies as well as the use of unconventional corrosion-resistant reinforcements, alternative binders to Portland cement, and innovative or traditional solutions for reinforced concrete protection and prevention against rebars corrosion such as corrosion inhibitors, coatings, self-healing techniques, and waterproofing aggregates. Analysis of the scientific literature highlights that there is no preferential way for the production of “green” concrete but that the sustainability of the building materials can only be achieved by implementing simulta-neous multiple strategies aimed at reducing environmental impact and improving both durability and performances

Thermal behaviour of metakaolin/fly ash geopolymers with chamotte aggregate

Geopolymers are generally appreciated for their good resistance against high temperatures. This paper compares the influence of thermal treatment with temperatures ranging from 200–1200 °C on the mechanical properties and microstructure of geopolymers based on two different aluminosilicate precursors, metakaolin and fly ash. Moreover, the paper is also aimed at characterizing the effect of chamotte aggregate on the performance of geopolymers subjected to high temperatures. Thermal treatment leads to a deterioration in the strength of metakaolin geopolymer, whereas fly ash geopolymer gains strength upon heating. The formation of albite above 900 °C is responsible for the fusion of geopolymer matrix during exposure to 1200 °C, which leads to the deformation of the geopolymer samples. Chamotte aggregate improves the performance of geopolymer material by increasing the thermal stability of geopolymers via sintering of the aggregate particles with the geopolymer matrix in the contact zone

Improving the thermal stability and fire safety of PVC formworks

This study examines the impact of materials and compositions on the fire design considerations of plastic formworks, focusing on the influence of building materials on the fire resistance of buildings, the safety of occupants, and the environment. The study investigates the chemical properties of formworks, including heat resistance, UV resistance, and smoke suppressant properties, which are essential for developing and optimizing formwork products. The research covers three key areas for improving thermal behaviour of PVC: (a) the development and evaluation of new metal complexes with dipentaerythritol, (b) cementitious compositions as a novel class of thermal stabilizers, and (c) the development and evaluation of a new synergistic thermo stabilizer based on sodium hexametaphosphate. To investigate the thermal degradation procedures of each additive for fire retardancy workability, the study utilizes advanced techniques such as thermal gravimetric analysis (TGA), fourier transform infrared spectroscopy (FT-IR), X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). The results demonstrate that hydrated cementitious materials are more effective in stabilizing PVC than metal chelates of dipentaerythritol or synergistic stabilizers based on sodium hexametaphosphate. Moreover, the study found that zinc, as a metal complex with dipentaerythritol, is more effective than traditional stabilizers. The research on cementitious compositions also revealed their highly economical, environmentally friendly, and compatible nature, making them an attractive option for use in the PVC formwork construction industry. The study also highlights the positive impact of calcium metaborate and sodium hexametaphosphate in improving the thermal behaviour of PVC. The study emphasizes the significance of fire-resistant materials in ensuring the safety of occupants and the environment, and the need for innovative solutions to enhance their effectiveness. In conclusion, this research underscores the importance of materials and compositions in the fire design considerations of plastic formworks. The study's findings can imply the development of more effective and sustainable fire-resistant materials and promote safer buildings

Review of the Application of Hydrotalcite as CO2 Sinks for Climate Change Mitigation

In recent decades, the environmental impact caused by greenhouse gases, especially CO2, has driven many countries to reduce the concentration of these gases. The study and development of new designs that maximise the efficiency of CO2 capture continue to be topical. This paper presents a review of the application of hydrotalcites as CO2 sinks. There are several parameters that can make hydrotalcites suitable for use as CO2 sinks. The first question is the use of calcined or uncalcined hydrotalcite as well as the temperature at which it is calcined, since the calcination conditions (temperature, rate and duration) are important parameters determining structure recovery. Other aspects were also analysed: (i) the influence of the pH of the synthesis; (ii) the molar ratio of its main elements; (iii) ways to increase the specific area of hydrotalcites; (iv) pressure, temperature, humidity and time in CO2 absorption; and (v) combined use of hydrotalcites and cement-based materials. A summary of the results obtained so far in terms of CO2 capture with the parameters described above is presented. This work can be used as a guide to address CO2 capture with hydrotalcites by showing where the information gaps are and where researchers should apply their efforts

Introduction to nanotechnology in eco-efficient construction

This chapter briefly reviews recent developments on the field of nanotechnology. Patent production by top countries are reviewed.  Some nanotech limitations are highlighted. The case of nanotechnology influence on the development of eco-efficient construction and building materials and its contribution for 2030 agenda for sustainable development is briefly addressed. A book outline is included.(undefined)info:eu-repo/semantics/publishedVersio

Palm Oil Clinker as a Waste by-Product: Utilization and Circular Economy Potential

Conservation of natural resources to create ecological balance could be significantly improved by substituting them with waste by-products. Palm oil industry operations increases annually, thereby generating huge quantity of waste to be dumped into the landfill. Palm oil clinker (POC) is a solid waste by-product produced in one of the oil palm processing phases. This chapter is designed to highlight the generation, disposal problems, properties and composition of POC. The waste to resource potentials of POC would be greatly discussed in the chapter starting with the application of POC in conventional and geopolymer structural elements such as beams, slabs, columns made of either concrete, mortar or paste for coarse aggregates, sand and cement replacement. Aspects such as performance of POC in wastewater treatment processes, fine aggregate and cement replacement in asphaltic and bituminous mixtures during highway construction, a bio-filler in coatings for steel manufacturing processes and a catalyst during energy generation would also be discussed. Circular economy potentials, risk assessment and leaching behavior during POC utilization would be evaluated. The chapter also discusses the effectiveness of POC in soil stabilization and the effect of POC pretreatment for performance enhancement. Towards an efficient utilization, it is important to carry out technical and economic studies, as well as life cycle assessments, in order to compare all the POC areas of application described in the present review article. POC powder has proven to be pozzolanic with maximum values of 17, 53.7, 0.92, 3.87, 1.46, for CaO, SiO2, SO3, Fe2O3 and Al2O3. Therefore, the present chapter would inspire researchers to find research gaps that will aid the sustainable use of agroindustry wastes. The fundamental knowledge contained in the chapter could also serve as a wake-up call for researchers that will motivate them to explore the high potential of utilizing POC for greater environmental benefits associated with less cost when compared with conventional materials