Papers by Keyword: Geopolymers

Abstract: Geopolymerization has emerged as a promising technology in the pursuit of sustainable and environmentally friendly construction practices. This process involves synthesizing inorganic polymers from natural and industrial by-products such as metakaolin, fly ash, slag, mine tailings, and other aluminosilicate materials using an alkaline hardener solution. Unlike traditional cement production, which involves high-energy consumption and significant carbon emissions, geopolymerization offers a promising avenue towards a cleaner environment by significantly reducing energy consumption, greenhouse gas emissions, industrial waste, and conserving natural resources. This review explores the principle of geopolymerization, its environmental benefits, and its potential applications as a cleaner alternative to traditional cement-based materials, fostering sustainable development and combating climate change thereby addressing the ecological impact of construction activities. The use of geopolymers not only diverts waste from landfills but also mitigates the need for the exploration of virgin raw materials, thus reducing the overall carbon footprint of infrastructural developments.

Abstract: Environmentally friendly building materials known as geopolymers are made by combining high-alkalinity solutions with powder components rich in silica and alumina. It has long been known that adding fibers to the matrix phase can improve the mechanical characteristics of composite materials made for various uses. Among these are SIFCON composites, which are made by first inserting the fibers into the mold and then packing the gaps between the fibers with an extremely fluid matrix phase. The present study looked over the mechanical properties and efficiency of cement-based and geopolymer-based slurry infiltrated fiber concrete SIFCON and G-SIFCON. In the current study, for the production of both SIFCON and G-SIFCON composites, 7.5% steel fiber by volume fraction was utilized for this purpose. Therefore, sets of concrete specimens including cylinders and prisms were prepared and tested in accordance with standard specifications. The results obtained from the conducted tests prove that the 7.5% of steel fiber ratio can be used effectively to improve the mechanical performance of G-SIFCON and SIFCON composites. Furthermore, the cement-based SIFCON can be effectively replaced by fly ash-based geopolymers. Also, for composites made with fly ash-based geopolymers (G-SIFCON), high compressive strength slurries may exhibit more enhancement in mechanical properties than normal strength slurries.

Abstract: Geopolymer is an innovative cement substitute constructed of alkali-activated cementitious materials (AACMs). Researchers interested in improving concrete's structural resistance, toughness, and flexure tensile strength have turned their focus to geo-polymer concrete binders. To completely understand how geopolymer binders act under these circumstances, it is necessary to investigate their behavior when exposed to multiaxial stress states. The purpose of this review is to examine geopolymer cement in depth and to get a better understanding of its mechanical characteristics. In this analysis, we see that Geopolymer concrete, in particular its compressive and tensile strengths, provides higher resilience. GPC is an eco-friendly material since it reduces emissions and requires less water for curing. Incorporating hybrid polypropylene and steel fibers to ternary mixed geopolymer concrete improves its mechanical qualities.

Abstract: The life cycle analysis (LCA) is a methodology that allows us to contemplate the environmental impact of a material during the different stages of the life cycle. The impact categories were used to measure the repercussions caused to the planet due to the high demand generated by construction materials. This study addressed the stages of a life cycle analysis, according to the ISO 14044 [1] standard, with the aim of evaluating, quantifying and comparing the environmental impacts associated with the manufacture of mortar with similar mechanical behavior: A conventional mortar and a geopolymeric mortar, the latter developed from a geopolymerization process of waste from the Peruvian mining industry [2,3]. The scope of the work sought to evaluate the main environmental impacts of both mortars, focusing on a "cradle to door" life cycle analysis. The application of LCA allowed optimizing the manufacturing process, reducing adverse environmental impacts. The results showed that the environmental impacts of the geopolymeric mortar presented better performance in the medium impact categories: Environmental impact and water consumption. On the other hand, the conventional mortar presented better performance in the stratospheric ozone depletion impact category.

Abstract: Alkali activated materials and geopolymers have attracted a lot of attention in the last 20 years thanks to their excellent mechanical performances, durability and sustainability properties, especially for civil applications. These materials also exhibit promising properties as fire- and corrosion-resistant protection systems. In a previous study, a 20-mm coating based on light-weight alkali activated mortar (LWAAM) suitable for the protection of steel structures against fire was successfully developed. To understand if the same coating is also able to ensure corrosion protection to steel structures, this study reports the results obtained in two different chloride-rich environments. The corrosion performance of the new system based on steel coated by LWAAM (using expanded perlite and hydrogen peroxide in the mix) was compared with a steel coated by a traditional alkali activated mortar (NWAAM). Electrochemical tests on steel samples immersed in an alkaline solution simulating the pore environment of the binder or embedded in the two different types of mortars were carried out in presence of different chloride concentrations. It was found that the alkaline environment is able to passivate the steel surface, however, the increasing of chloride ions concentration, affects passive film stability and promotes steel corrosion. In presence of low chloride concentration (i.e., 0.2M NaCl), the increased porosity of the LWAAM did not impair the steel corrosion protection, when compared with NWAAM.

Abstract: Old and seismically prone buildings are in need of strengthening in order to comply with the latest building codes and to prolong their service life. For over two decades fiber-reinforced polymers (FRP) have been successfully used for this purpose. However, the poor performance in high temperatures of organic matrices has led researchers to investigate the use of inorganic matrices. Consequently, textile-reinforced mortars (TRM) have been opted for strengthening, since they incorporate textiles impregnated in inorganic cementitious matrices. Lately, in order to promote sustainability and lower the high carbon emissions of cement, alkali-activated mortars, also called geopolymers, have been investigated as an alternative. Their high performance and fireproof properties have made them excellent candidates as matrices in advanced composites for strengthening. This study aims to provide an overview of research in the field of advanced composites with alkali-activated matrices used for strengthening of concrete members. Systems implementing either fiber sheets or meshes have been used so far to strengthen reinforced concrete members, indicating promising results of the new advanced composite.

Abstract: Geopolymers are known to be environmentally – friendly construction materials that can be used in different applications including concretes and mortars, fire – resistant coating materials, road pavements and masonry units. Despite the economic and environmental – related benefits of utilizing geopolymer products, the production of these materials is also associated with some challenges and difficulties that need to be resolved for the technology to gain recognition and acceptability in the construction industry. In this paper, publications were reviewed to provide some understanding of the problems and challenges of geopolymer brick production. Composition of alkali activator along with curing temperature, are major factors that significantly influence the production cost of geopolymer bricks. Also, incorporation of calcium - rich co - binders into geopolymer mixtures, may lead to reduction in durability resistance of the brick product.

Abstract: The prospects of implementing the mechanochemical activation method of volcanic silicate and aluminosilicate rocks - perlites, tuffs, pumice, etc. are being considered for the production of a wide range of building materials using energy-conserving technologies. The thermodynamic and kinetic parameters of interaction in the systems of aluminosilicate – NaOH have been presented, indicating low-temperature sintering of volcanic rocks with sodium hydroxide. According to the degree of activity, the rocks have the following order: perlites, tuffs, obsidian, microcline. Kinetic parameters are presented: concentration, temperature, conversion degree, reaction rate constant, time of complete reaction and product layer thickness.

Abstract: The civil engineering projects that includes soft clay within its activities has a serious concern of hazards, such hazards can be overcame by treating the existing soils by certain materials which are named as "stabilizers". The common materials that are highly used in this field are ordinary Portland cement, fly ash, lime and rice husk ash, etc. Each one of these stabilizers has its known shortcomings. The alkali activation of any alumina silicate source produces some kind of cost effective primary binding gel which is known as "Geopolymers". This study is devoted to investigate the role of liquid over fly ash ratio to some soil – FA based Geopolymers geotechnical properties. Such ratio is taken as 2.71, 3.167, 3.8 and 4.75 respectively within the experimental program and the investigated geotechnical properties are the specific gravity, liquid and plastic limit, compaction characteristics and California bearing ratio. The tests results showed that the maximum dry density decreased about 42 % at 2.71 liq/FA whereas this the specific gravity decreased 27 % at the same this ratio. In addition, the 3.8 and 4.75 of such limits revealed no plastic behavior due to the high presence of liquid.

Abstract: This article focuses on the compression strength of lightweight concrete based on alkaline-activated waste materials. The problem is important not only because of the possibility of disposal of excessive amount of building or industrial waste, but also because of the decreasing amount of natural aggregate deposits. Apart from the problem of the decreasing amount of natural aggregate deposits, there is also a problem related to the emission of greenhouse gases from cement production processes. It is estimated that the synthesis of alkaline-activated composites is twice as energy-intensive as the production of Portland cement and generates 4-8 times less carbon dioxide. Alkaline-activated concrete production can therefore lead to a significant reduction in environmental impact. The paper presents a thesis that there is a possibility of a monolithic combination of an alkaline activated mineral binder with an artificial ash-porbit aggregate, which will contribute to the improvement of the compression strength of light concrete based on alkaline activated energy waste materials and elimination of Portland cements.