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The utilization of recycled concrete and glass aggregates in concrete production has emerged as a highly promising method to significantly increase the recycling rate of waste materials. However, the interaction between alkaline environment and silica present in concrete detrimentally impacts mechanical properties and durability of the concrete due to the significant silica content of the aggregates. This study aims to develop a high‐performance and sustainable concrete to resist alkali–silica reaction (ASR). The study focuses on the use of a blend of ground granulated blast furnace slag (GGBS) and fly ash (FA) as binder materials to mitigate negative effects of the ASR on the mechanical properties and and durability of concrete made with crushed glass sand and coarse recycled concrete aggregate (RCA). Various tests, including ASR expansion, flow, slump, density, compression, three‐point bending, water absorption, and chloride attack, were conducted. Furthermore, microanalysis using scanning electron microscopy and energy‐dispersive x‐ray spectroscopy was performed. Based on the results, it is found that the GGBS is less effective than the FA in reducing the ASR expansion of the concrete, with only 3%, 9%, and 12% decreased expansion as a result of the addition of 20%, 40%, and 70% GGBS to the concrete containing 30% FA, respectively. It is also shown that combining 20% GGBS with 30% FA in the RCA concrete containing glass sand develops similar compressive and flexural strengths and water absorption compared to that containing natural sand. This can be related to the pozzolanic reaction of the FA and GGBS, which helps to retain the alkalis for reducing the crack development and propagation in the concrete. However, further GGBS content leads to a decrease in the strengths and an increase in the water absorption of the concrete. The results of this study point to the significant potential of combining FA and GGBS at an optimum ratio to mitigate the ASR effect on RCA concretes containing crushed glass sand. This approach helps in minimizing the emission of greenhouse gases and other pollutants generated during cement production, thereby mitigating environmental pollution. Additionally, it helps the preservation of natural resources by reducing the depletion of natural sand and coarse aggregate. [ABSTRACT FROM AUTHOR]

The building sector is responsible for about 37% of the global carbon dioxide emissions, 6% of which result from concrete (and particularly cement) production. Using recycled and supplementary cementitious materials and adopting a whole building life cycle approach can be seen as multi‐beneficial strategies for materials' design. In this framework, this study aims to formulate a green concrete, by replacing 10, 15 and 20% of cement with a secondary raw material constituted of vitrified bottom ash derived from municipal solid waste incineration. The basic physical and mechanical properties were measured up to 365 days, so to evaluate the effects of the cement replacement both on short and long‐term behavior. Life Cycle Assessment was used as a tool to evaluate the environmental performance of the developed green concrete. An Eco‐Mechanical Analysis was also performed to match the environmental impacts with the mechanical behavior, allowing to assess that the concrete produced by replacing 20% of cement with vitrified municipal solid waste incineration bottom ash (if classified as hazardous waste) is the one that leads to optimize the overall sustainability. The approach proposed in this work, which can be easily generalized, contributes to the definition of a route for the implementation of innovative green construction building materials by using waste. [ABSTRACT FROM AUTHOR]

The addition of recycled concrete aggregates together with industrial by‐products for the concrete production is an effective solution to the environmental problems in terms of excess waste materials and massive nonrenewable natural resources consumption. This article investigates the long‐term behavior and microstructure of sustainable self‐compacting concrete (SCC) by substantially substituting natural coarse aggregate with recycled coarse aggregates (RCA) and cement with supplementary cementitious materials (SCM). The influences of RCA and SCM content as well as SCM combination type (fly ash, ground granulated blast furnace slag and/or silica fume) on the mechanical properties and long‐term deformation of recycled aggregate SCC (RA‐SCC) were assessed in detail. Furthermore, scanning electron microscope and x‐ray diffraction were implemented to justify the reasons for improvement on mechanical properties and long‐term behavior of RA‐SCC. The results indicate that the addition of RCA reduces the compressive strength and elastic modulus of RA‐SCC, and increases the creep and shrinkage deformations. However, incorporating SCM with a combination of fly ash, ground granulated blast furnace slag and silica fume compensates for the detrimental effect of RCA and makes considerable improvement in strength and reduction in the long‐term deformations. Microstructure analysis confirms the reasons of improvement, which is mainly attributed to the addition of SCM by adopting a combination type, resulting in a more compact microstructure such as stronger interfacial transition zone. Based on the experimental results, the correction factors of RCA and SCM were introduced in conjunction with fib Model Code 2010 model to evaluate the creep coefficient of RA‐SCC. [ABSTRACT FROM AUTHOR]

Development of thermally and mechanically activated concrete fines as supplementary cementitious material – project presentation and first results In the light of resource demands for construction and limited availability, an efficient recirculation of building materials is essential. For concrete production, this means the use of recycled aggregates as partial replacement of gravel and sand, with the latter being severely restricted. Since crushing yields a concentration of porous hydrated cement in the fine particles, the application of crushed concrete fines as aggregates or milled supplementary cementitious material (SCM) results in limited concrete performance. Present results show that hydrated cement can be reactivated through an additional thermal processing, yielding improved mechanical and durability properties like carbonation or chloride penetration when used as SCM in concrete. The promising results initiated a funded research project, which investigates influencing factors of the thermal‐mechanical processing of crushed concrete sands with varying compositions on the performance as SCM. [ABSTRACT FROM AUTHOR]

Carbonated wollastonite clinker (CS) may be suitable as supplementary cementitious material (SCM) for mortar and concrete. The microstructure of unground CS clinker, carbonated CS slurry and a mortar blended with carbonated CS are investigated by scanning electron microscopy. Additionally, a reference mortar with pure Portland cement and one with a cement replacement level of 30 mass‐% by carbonated CS are produced to assess its contribution to compressive strength development. The calcium silicates are decalcified during carbonation resulting in CaCO3 and amorphous SiO2. The latter reacts when used as SCM in mortar influencing the Ca/Si ratio of calcium‐silicate‐hydrate and contributing to compressive strength development. [ABSTRACT FROM AUTHOR]

In the cement industry, it is usual to use calcined clays due to structural changes caused by thermal activations; however, there are other activation methods, such as mechanical activation by grinding. This method is not so common and has been relegated to the second level. Thus, in this work, the physical and mechanical changes in the structure of clays, induced by comminution processes, of standard clays and a low‐grade kaolinitic multicomponent clay, derived from weathering of metamorphic rock, were evaluated. These changes were measured using X‐ray fluorescence, X‐ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, specific surface area (SSA) by Brunauer–Emmett–Teller method, and lime fixing as a measure of pozzolanic activity. It was found that the milling process modified the structure of the clays and the pozzolanic activity, since the main reflection (001) disappeared, the dehydroxylation temperature decreased to a maximum differential of 150°C with 120 s of milling time, especially in T:O:T clays, and the SSA increased along with the lime fixing to a maximum of 119 m2/g and 46%, respectively. In this way, the milling process is effective for the mechanical activation of the clay, especially in multicomponent clay, making it interesting for use as supplementary cementitious material. [ABSTRACT FROM AUTHOR]

Calcined clay blended cements play a major role in cement industry's strategy to reduce CO2 emissions. During their hydration, an accelerated aluminate reaction is often observed to affect the sulfate balance. The objective of this study was to provide insights into the influence of different calcined clays on the hydration of cubic tricalcium aluminate (C3A). A cementitious model system consisting of cubic C3A, quartz powder, calcium sulfate and a model pore solution was investigated. The influence of three different calcined clays and one nanolimestone was examined by a successive replacement of the quartz powder and variation of the calcium sulfate. Heat flow and hydrate phase development were followed by isothermal calorimetry and quantitative in‐situ X‐ray diffraction. Accelerated ettringite formation and sulfate depletion were observed for all calcined clays, while the nanolimestone exhibited the opposite effect. It was found that adsorption of SO4 ions and/or Ca‐SO4‐complexes at the surface of calcined clay particles is the main factor inhibiting retardation of the C3A hydration in absence of a silicate reaction. In the Al‐rich systems a retardation through sulfate adjustment seems to be impeded by additional Al ions, which react with Ca adsorbed onto and leached from the C3A surface. [ABSTRACT FROM AUTHOR]

The reuse and reincorporation of waste generated in the production processes are becoming increasingly important in the world, due to the double effect that it has in terms of sustainability. The first one is the environmental factor, since the impact generated is reduced by reducing the amount of wastes. The second one is the financial factor, since new products are developed that companies did not initially have, generating financial profitability. Therefore, this research evaluates the possible reuse of waste from gravel and sand wash mud of an aggregate plant as a supplementary cementitious material (SCM) after being thermally activated, seeking to promote the circular economy in the construction materials sector. The physical, chemical, and mineralogical characterization of the waste is presented and its pozzolanic activity was evaluated by means of the SAI‐strength activity index. It was found that despite its low content of clay minerals, the thermally activated waste had very good performance as SCM with SAI between 81 and 106 with a tendency to increase with the age of cure. Showing that this can be a very promising potential use for this kind of waste. [ABSTRACT FROM AUTHOR]

The principal air pollution within the concrete enterprise is cement in charge of roughly 5–7% of manufactured CO2 emissions. For reducing CO2 emissions and improving concrete properties, new types of natural cementitious materials have been served in concrete throughout the last two decades. In this study, a mineral powder (MP) as a type of supplementary cementitious material has been introduced and the chemical and physical properties of this MP and mechanical properties of the produced concrete were investigated. In this regard, the total number of 24 concrete mixes with 0 to 40% replacement of Portland cement (PC) with MP was designed. Concrete samples were tested for compressive, flexural, splitting tensile strengths, and elastic modulus at the age of 7, 28, 42, and 90 days. The experimental results indicate that the maximum compressive, flexural, and splitting tensile strengths are obtained by replacing about 5% PC with MP. Finally, the amount of CO2 emission reduction for concrete specimens containing MP was evaluated. [ABSTRACT FROM AUTHOR]

The free water in calcined phyllosilicate–water mixtures exhibits a distinctly different behaviour in its X‐ray amorphous scattering contribution as opposed to fly ash– or limestone powder–water mixtures. While fly ash and limestone powder yield a continuous increase in the scattering contribution when water is added, the scattering contribution stagnates for calcined phyllosilicates over a wide range of water addition. There is a direct correlation between the consistency of the sample and the X‐ray amorphous scattering contribution caused by the water. The same correlation can also be found in in situ X‐ray diffraction measurements of hydrating systems. As long as the sample has a pasty consistency, the scattering contribution of the water decreases with progressive reaction. After the transition from fresh paste to final set, there is no further reduction of the X‐ray amorphous scattering contribution caused by the free water, which means that the free water cannot be quantified correctly from this point in time. The scattering contribution of free, not chemically bound water in different water–solid mixtures as well as the changes of the scattering contribution due to the reaction progress of hydrating systems is examined. Rietveld analysis with a combination of the G factor and PONKCS (partial or no known crystal structure) method is used for quantification. [ABSTRACT FROM AUTHOR]