Green Concrete Based on Quaternary Binders with Significant Reduced of CO2 Emissions
TL;DR: In this paper, the authors presented studies of plain concretes prepared based on a quaternary binder containing various percentages of selected supplementary cementitious materials (SCMs) and the possibilities of nanotechnology in concrete technology were also used.
Abstract: The article presents studies of plain concretes prepared based on a quaternary binder containing various percentages of selected supplementary cementitious materials (SCMs). The possibilities of nanotechnology in concrete technology were also used. An additional important environmental goal of the proposed solution was to create the possibility of reducing CO2 emissions and the carbon footprint generated during the production of ordinary Portland cement (OPC). As the main substitute for the OPC, siliceous fly ash (FA) was used. Moreover, silica fume (SF) and nanosilica (nS) were also used. During examinations, the main mechanical properties of composites, i.e., compressive strength (fcm) and splitting tensile strength (fctm), were assessed. The microstructure of these materials was also analyzed using a scanning electron microscope (SEM). In addition to the experimental research, simulations of the possible reduction of CO2 emissions to the atmosphere, as a result of the proposed solutions, were also carried out. It was found that the quaternary concrete is characterized by a well-developed structure and has high values of mechanical parameters. Furthermore, the use of green concrete based on quaternary binders enables a significant reduction in CO2 emissions. Therefore quaternary green concrete containing SCMs could be a useful alternative to plain concretes covering both the technical and environmental aspects. The present study indicates that quaternary binders can perform better than OPC as far as mechanical properties and microstructures are concerned. Therefore they can be used during the production of durable concretes used to perform structures in traditional and industrial construction.
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TL;DR: In this paper , the effect of polyvinyl alcohol (PVA) fiber and exposure temperature on the behavior of PVA fiber-reinforced geopolymer mortar after exposure to high temperatures was evaluated.
Abstract: Polyvinyl alcohol (PVA) fiber-reinforced geopolymer mortar is an eco-friendly construction material with excellent mechanical properties and durability. Visual observation, mass loss measurement, cubic and prism compressive tests , flexural tests, thermogravimetric and differential thermal analysis , scanning electron microscopy, and bubble parameter tests were conducted to evaluate the effect of PVA fiber and exposure temperature on the behavior of PVA fiber-reinforced geopolymer mortar after exposure to high temperatures. The PVA fiber contents were selected as 0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, and 1.2%, and the target temperatures were 25 °C, 200 °C, 400 °C, 600 °C and 800 °C. The results indicate that significant mass loss of the geopolymer mortar could be observed when the exposure temperature increased from 25 °C to 250 °C, whereas slight mass loss occurred from 250 °C to 700 °C, and no mass loss was detected from 700 °C to 800 °C. As the temperature increased, the geopolymer mortar gradually densified, while the geopolymer mortar continuously developed more cracks and pores. The compressive and flexural strengths of the geopolymer mortar improved as the temperature increased from 25 °C to 200 °C, but it decreased significantly as the temperature further increased to 800 °C. In addition, on exposure to 200 °C, the presence of PVA fibers significantly improved the cubic and prism compressive strengths and flexural strength by 50.5%, 29.4%, and 66.3%, respectively, compared with the geopolymer mortar without fibers. As the temperature increased above 200 °C, although the PVA fiber decomposed, the defects left by the melt fibers slightly influenced the strength of the geopolymer mortar.
68 citations
TL;DR: In this article, the authors present results of tests of modified concretes both with the addition of coal fly ash (CFA) ash and with an innovative nanoadmixture (NA) used to accelerate the strength growth in cement composites.
61 citations
TL;DR: In this paper , the fracture mechanics parameters of concretes made of quaternary binders (QBC) were investigated using the digital image correlation (DIC) technique.
56 citations
TL;DR: In this article, a chemical nano-admixture (NA) in the form of seeds of the C-S-H phase was used to accelerate the strength growth in concretes.
Abstract: Siliceous fly ash (FA) is the main additive to currently produced concretes. The utilization of this industrial waste carries an evident pro-ecological factor. In addition, such actions have a positive effect on the structure and mechanical parameters of mature concrete. Unfortunately, the problem of using FA as a Portland cement replacement is that it significantly reduces the performance of concretes in the early stages of their curing. This limits the possibility of using this type of concrete, e.g., in prefabrication, where it is required to obtain high-strength composites after short periods of curing. In order to minimize these negative effects, this research was undertaken to increase the early strength of concretes with FA through the application of a specifically formulated chemical nano-admixture (NA) in the form of seeds of the C-S-H phase. The NA was used to accelerate the strength growth in concretes. Therefore, this paper presents results of tests of modified concretes both with the addition of FA and with innovative NA. The analyses were carried out based on the results of the macroscopic and microstructural tests in five time periods, i.e., after 4, 8, 12, 24 and 72 h. The results of tests carried out with the use of NA clearly indicate the possibility of using FA in a wide range of management areas in sustainable concrete prefabrication.
56 citations
TL;DR: In this article , the fracture mechanics parameters of new concrete composites based on quaternary blended cements (QBC) have been investigated and a composition of the two most commonly used mineral additives, i.e., fly ash (FA) and silica fume (SF), in combination with nanosilica (nS), has been proposed as a partial replacement for ordinary Portland cement (OPC) binder.
Abstract: This study presents test results and in-depth discussion regarding the measurement of the fracture mechanics parameters of new concrete composites based on quaternary blended cements (QBC). A composition of the two most commonly used mineral additives, i.e., fly ash (FA) and silica fume (SF), in combination with nanosilica (nS), has been proposed as a partial replacement for ordinary Portland cement (OPC) binder. Four series of concrete were made, one of which was the reference concrete (REF) and the remaining three were QBC. During the research, the main mechanical parameters of compressive strength (fcm) and splitting tensile strength (fctm), as well as fracture mechanics parameters and the critical stress intensity factor KIcS, along with critical crack-tip opening displacements (CTODc) were investigated. Based on the tests, it was found that the total addition of siliceous materials, i.e., SF + nS without FA, increases the strength and fracture parameters of concrete by approximately 40%. On the other hand, supplementing the composition of the binder with SF and nS with 5% of FA additive causes an increase in all mechanical parameters by approximately 10%, whereas an increase by another 10% in the FA content in the concrete mix causes a significant decrease in all the analyzed factors by 10%, compared to the composite with the addition of silica modifiers only.
53 citations
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TL;DR: The use of silica-rich SCMs influences the amount and kind of hydrates formed and thus the volume, the porosity and finally the durability of these materials.
1,920 citations
TL;DR: The concrete industry is known to leave an enormous environmental footprint on Planet Earth as discussed by the authors, which contributes to the general appearance that concrete is not particularly environmentally friendly or compatible with the demands of sustainable development.
Abstract: The concrete industry is known to leave an enormous environmental footprint on Planet Earth. First, there are the sheer volumes of material needed to produce the billions of tons of concrete worldwide each year. Then there are the CO2 emissions caused during the production of Portland cement. Together with the energy requirements, water consumption and generation of construction and demolition waste, these factors contribute to the general appearance that concrete is not particularly environmentally friendly or compatible with the demands of sustainable development. This paper summarizes recent developments to improve the situation. Foremost is the increasing use of cementitious materials that can serve as partial substitutes for Portland cement, in particular those materials that are by-products of industrial processes, such as fly ash and ground granulated blast furnace slag. But also the substitution of various recycled materials for aggregate has made significant progress worldwide, thereby reducing the need to quarry virgin aggregates. The most important ones among these are recycled concrete aggregate, post-consumer glass, scrap tires, plastics, and by-products of the paper and other industries.
1,120 citations
TL;DR: In this article, the authors evaluated the environmental impact of four cement manufacturing processes: (1) the production of traditional Portland cement, (2) blended cement (natural pozzolans), (3) cement where 100% of waste cement kiln dust is recycled into the kiln process, and (4) Portland cement produced when CKD is used to sequester a portion of the process related CO2 emissions.
994 citations
TL;DR: In this paper, three strategies of CO2 reduction including energy saving, carbon separation and storage as well as utilizing alternative materials in detail have been reviewed and the barriers against worldwide deployment of such strategies are identified and comprehensively described.
903 citations
TL;DR: A review of the current state-of-the-art and standards underpinning the production and use of OPC-based cements and concretes can be found in this paper.
Abstract: The cement industry faces a number of challenges that include depleting fossil fuel reserves, scarcity of raw materials, perpetually increasing demand for cements and concretes, growing environmental concerns linked to climate change and an ailing world economy. Every tonne of Ordinary Portland Cement (OPC) that is produced releases on average a similar amount of CO2 into the atmosphere, or in total roughly 6% of all man-made carbon emissions. Improved production methods and formulations that reduce or eliminate CO2 emissions from the cement manufacturing process are thus high on the agenda. Emission reduction is also needed to counter the impacts on product cost of new regulations, green taxes and escalating fuel prices. In this regard, locally available minerals, recycled materials and (industry, agriculture and domestic) waste may be suitable for blending with OPC as substitute, or in some cases replacement, binders. Fly ash, Blast furnace slag and silica fumes are three well known examples of cement replacement materials that are in use today that, like OPC, have been documented and validated both in laboratory tests and in practice. The first is a by-product of coal combustion, the second of iron smelting and the third of electric arc furnace production of elemental silicon or ferro silicon alloys. This paper presents a concise review of the current state-of-the-art and standards underpinning the production and use of OPC-based cements and concretes. It outlines some of the emerging green alternatives and the benefits they offer. Many of these alternatives rely on technological advances that include energy-efficient, low carbon production methods, novel cement formulations, geopolymers, carbon negative cements and novel concrete products. Finally, the economics of cement production and the trends in the UK, US and the Gulf Cooperation Council (GCC) Region are presented, to help guide and inform future developments in cement production based on maximizing the value of carbon reduction.
582 citations