Concrete Production Research Articles

Environment friendly sustainable concrete produced from marble waste powder

<p>Concrete is an indispensable construction material renowned for its versatility and durability, yet its traditional components pose significant environmental challenges. The cement industry is a major emitter of CO2, while the extensive extraction of natural aggregates depletes finite resources. In response, researchers have explored alternative materials like Marble Waste Powder (MWP) as sustainable substitutes in concrete production. This study investigates the feasibility of incorporating MWP as partial replacements for cement and fine aggregate, examining substitution fractions of 25% and 35%. Through experimental analysis, the mechanical properties and cost implications of these modified concrete blends are evaluated. The research findings reveal that integrating MWP into concrete formulations enables the production of high-strength concrete at a reduced cost, offering a promising solution to enhance the sustainability of construction practices. By partially replacing conventional materials with MWP, the environmental impact associated with concrete production can be mitigated, contributing to efforts aimed at reducing carbon emissions and conserving natural resources. Additionally, the study underscores the importance of eco-friendly innovations in construction materials, emphasizing the need for sustainable alternatives to meet the growing demand for infrastructure development while minimizing environmental harm. Overall, this research highlights the novel use of MWP as a sustainable alternative in concrete production, showcasing its potential to address environmental concerns and promote more eco-conscious construction practices. Through the exploration of mechanical performance and economic feasibility, the study provides valuable insights for advancing sustainability in the construction industry and achieving long-term environmental stewardship.</p>

An Experimental Study On Strength Characteristics Concrete by Partial Replacement of Coarse Aggregate with Bethamcherala Waste Stone

In the current research work, as per the best knowledge of the authors, for the first time Bethamcherla stones has been used as a partial replacement of coarse aggregate in concrete mix. The scarcity of natural aggregate as well as finding alternative materials that can maintain or enhance the properties of concrete is crucial for sustainable construction practices. Bethamcherla stones (BS), which mainly comprises by limestone can be a potential substitute for coarse aggregate. Limestone is a common material used in concrete production, and its use as an aggregate could offer advantages such as reducing the demand for traditional aggregates and utilizing local resources efficiently. The concrete specimens, casted using BS, were kept for curing for different durations (7, 21, and 28 days), and the mechanical property was assessed using the compressive strength test, a standard procedure for evaluating concrete performance. Compressive strength is a fundamental parameter that reflects the ability of concrete to withstand loads and pressures, making it an essential property to study. It would be interesting to see the results of this study, especially how the compressive strength of the concrete changes with different replacement levels of coarse aggregate with BS aggregates (10%, 20%, 30%, and 40%). This data would provide insights into the effectiveness of using BS as a substitute and help determine the optimal replacement ratio that balances cost and performance considerations. Additionally, while compressive strength is a critical mechanical property, other properties such as flexural strength, durability, and elevated temperature effect also need to be evaluated to understand how the BS aggregates influence the overall behavior of the concrete. If this experimental study proves successful, it could pave the way for more sustainable and cost-effective construction practices in the Kurnool district of Andhra Pradesh and other regions facing similar challenges with traditional aggregate availability. Remember that the success of this research will depend on the accuracy of testing methods, the representativeness of the specimens, and the relevance of the findings to real-world construction applications. Seeing such innovative efforts toward improving construction materials and practices for a more sustainable future is exciting.

Possibilities of replacing natural sand in concrete

This study explores the potential of using fine recycled aggregate (FRA) to replace natural sand in concrete production. The research was divided into two parts. In the first part, natural aggregate’s complete fine fraction (0‑4 mm) was replaced with FRA in conventional concrete for two strength classes. In the second part, individual fine components of high-performance concrete (HPC) were substituted with a similar fraction of fine recycled HPC and concrete aggregate. The physical and mechanical properties of these mixtures with recycled aggregate were evaluated against reference mixtures that contained only natural aggregate, following European standards. Results showed that while most of the concrete and HPC mixtures with recycled aggregate showed slight decreases in properties compared to the reference mixes, the most significant reduction in mechanical properties was observed in the flexural tensile strength of the concrete mixture with FRA, which decreased by over 50 %. The absorption by immersion increased by up to 85 %. The deterioration in properties must be considered during the design stage and only used in applications where it will not affect the functionality of the structures.

Utilization of high fly ash dosage to reduce cement consumption in concrete formulations

The concrete production is responsible for high proportion of total carbon dioxide emission due to enormous consumption of Portland cement. This traditional binder system is due to high autogenous emission during calcination the main carrier of such negative environmental impact. The effective way to reduce the use of Portland cement is to replace that this binding material exhibiting lower energy demandingness. This paper deals with the utilization of fly ash as Portland cement replacement, which is frequently applied in concrete industry. The paper deals the highest replacement level in accordance with valid regulations. The experimental program was focused on the properties of fresh concrete mixture and basic physical and mechanical properties of hardened concrete. The attained results confirmed good potential of this approach, however the increase of plasticizer dosage was necessary to maintain a similar consistency of fresh mixture. That is why the fresh mixture exhibited lower level of air content.

An Experimental inquiry into Concrete Properties with Partial Cement Replacement Using Alccofine and Metakaolin

In this research work, we delve into the pivotal role of concrete in modern construction practices and its indispensable nature across diverse structures. Concrete's widespread use underscores its significance in the construction industry, where economic considerations heavily rely on material cost efficiency. This study focuses on experimental investigations involving Alccofine and metakaolin, aimed at enhancing concrete strength while concurrently addressing environmental concerns such as CO2 emissions. These materials serve as substitutes for traditional cement in M20 grade concrete, with meticulous mix designs tailored to optimize performance. Metakaolin replaces cement at varying percentages (0%, 5%, 10%, and 15%), while Alccofine remains a constant 10% replacement in cement concrete. Specimens undergo rigorous curing and are subjected to comprehensive 28-day testing for compressive, split tensile and flexural strengths. This investigation aims to provide insights into the feasibility and effectiveness of using Alccofine and metakaolin as sustainable alternatives in concrete production, thus addressing both economic and environmental considerations. Key Words: Alccofine, Metakaolin, Cement, Concrete, Compressive Strength, Split Tensile Strength, Flexural Strength.

The use of concrete slurry waste to improve the properties of the stabilised soil

It is often necessary to use stabilising additives during construction to improve the resulting soil properties to ensure the good quality of civil engineering structures. These additives are often produced at high temperatures and with a high carbon footprint. This paper focuses on soil stabilization with waste concrete slurry, which is produced during the production of fresh concrete. The selected clay soil was stabilized with cement and CSW at 2, 4, and 6 % by weight of soil. Compressive strength, the resistance to freezing and thawing, Initial bearing index (IBI), and California bearing capacity (CBR) were monitored. The research did not confirm better performance of CSW binder even at higher dosage compared to cement, which was due to the high water content of the mixtures. Positive results were achieved especially in Freez-Thaw resistance.

Sustainable Hybrid Lightweight Aggregate Concrete Using Recycled Expanded Polystyrene.

Global concrete production, reaching 14×1013m3/year, raises environmental concerns due to the resource-intensive nature of ordinary Portland cement (OPC) manufacturing. Simultaneously, 32.7×109 kg/year of expanded polystyrene (EPS) waste poses ecological threats. This research explores the mechanical behavior of lightweight concrete (LWAC) using recycled EPS manufactured with a hybrid cement mixture (OPC and alkali-activated cement). These types of cement have been shown to improve the compressive strength of concrete, while recycled EPS significantly decreases concrete density. However, the impact of these two materials on the LWAC mechanical behavior is unclear. LWAC comprises 35% lightweight aggregates (LWA)-a combination of EPS and expanded clays (EC) - and 65% normal-weight aggregates. As a cementitious matrix, this LWAC employs 30% OPC and 70% alkaline-activated cement (AAC) based on fly ash (FA) and lime. Compressive strength tests after 28 curing days show a remarkable 48.8% improvement, surpassing the ACI 213R-03 standard requirement, which would allow this sustainable hybrid lightweight aggregate concrete to be used as structural lightweight concrete. Also obtained was a 21.5% reduction in density; this implies potential cost savings through downsizing structural elements and enhancing thermal and acoustic insulation. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy reveal the presence of C-S-H, C-(A)-S-H, and N-A-S-H gels. However, anhydrous products in the hybrid LWAC suggest a slower reaction rate. Further investigation into activator solution dosage and curing temperature is recommended for improved mechanical performance on the 28th day of curing. This research highlights the potential for sustainable construction incorporating waste and underscores the importance of refining activation parameters for optimal performance.

EXPLORATION AND COMPARISON BETWEEN REGULAR CONCRETE AND CONCRETE WITH MINERAL ADDITIVES

Concrete is a fundamental building material with critical properties such as durability, strength, and versatility. In recent years, there has been increasing interest in enhancing concrete performance and sustainability by incorporating mineral additives such as fly ash, slag, and silica fume. This study explores and compares the characteristics of regular concrete and concrete with mineral additives to evaluate their suitability for various construction applications. The research focuses on the mechanical properties, durability, and environmental impacts of both types of concrete. Laboratory tests will be conducted to compare the compressive strength, tensile strength, resistance to freeze-thaw cycles, chemical attacks, and workability of regular concrete and concrete with mineral additives. Additionally, life cycle assessments will be performed to analyze the environmental implications of using mineral additives in concrete production. One of the main advantages of mineral additives is their potential to improve the strength and durability of concrete. Fly ash, slag, and silica fume have been shown to enhance long-term strength, reduce permeability, and increase resistance to chemical attacks in concrete mixtures. Furthermore, using mineral additives can reduce the reliance on cement, a primary component of concrete with a significant carbon footprint, leading to reduced greenhouse gas emissions and resource depletion. Index Terms – Concrete, Mineral additives, Durability, Strength.

Performance of Sustainable Green Concrete Incorporating Quarry Dust and Ferronickel Slag as Fine Aggregate.

This paper presents a study on the combined use of two by-products, namely quarry dust (QD) and ferronickel slag (FNS), as a full substitute for natural sand to improve the greenness of concrete production. Quarry dust was used in increments of 25% to a maximum of 75% substitution, where nickel slag was used as the remaining proportion of fine aggregate. All the combinations of quarry dust and nickel slag were found to be compliant with AS 2758.1 and they showed notably better grading than 100% sand. In this research, standard concrete tests, such as the slump test for fresh concrete, and compression, tensile and shrinkage tests for hardened concrete, were conducted. Scanning electron microscopy and X-ray diffraction analysis were also conducted for microstructural investigation. The results concluded that the combinations of quarry dust and nickel slag in concrete as a whole substitution of sand provide similar results for these properties. Specifically, 25% quarry dust with 75% nickel slag proved to be the most promising alternative to sand, with compressive and splitting tensile strengths of 62 and 4.29 MPa, respectively, which were 16% and 20% higher than those of the control mix. Also, lower drying shrinkage was observed for this combination compared to the control mix. The higher strength is attributed to the rough texture and angular shape of both quarry dust and nickel slag providing a better mechanical interlocking. The validity of this result has also been confirmed through image analysis of micrographs from various specimens. In microstructural investigations, specimens with QD and FNS exhibited fewer voids and a more compact surface compared to the control specimen. This shows the potential for further research into the use of quarry dust and nickel slag in the production of green concrete.

Microstructural and Residual Properties of Self-Compacting Concrete Containing Waste Copper Slag as Fine Aggregate Exposed to Ambient and Elevated Temperatures

In recent times, with rapid development in the construction sector, the use of enormous amounts of materials is required for the production of concrete. Fire penetrates concrete, leading to chemical contamination, small cracks, and lightening. These effects can significantly change the properties of concrete’s structure, reduce its strength and durability, and also change the behavior of the structure and lead to effects on the environment. An attempt was made to study the effects of elevated temperature on the mechanical characteristics of self-compacting concrete (SCC) with by-products including fly ash as a partial replacement for cement and waste copper slag as a partial replacement for fine aggregate at 0%, 10%, 20%, 30%, 40%, 50%, 60%, and 70%. The SCC specimens were subjected to elevated temperatures ranging from 200, 400, 600, and 800 °C, respectively, for a steady-state of two hours in a digital muffle furnace. The residual compressive strength, mass loss, ultrasonic pulse velocity, and residual density along with a visual inspection of cracks and color changes were observed. In this study, with over 400 °C temperatures, surface fractures appeared. The residual compressive strength (R-CMS) of all the individual temperatures of the SCC-WCS% mixes exhibited a gain in strength range from 31 to 34 MPa at 400 °C, 26 to 35 MPa at 600 °C, and 22.5 MPa to 33.5 MPa at 800 °C, respectively. Microstructural analysis of SCC-WCS% mixtures subjected to elevated ambient temperatures is carried out with a scanning electron microscope (SEM) and X-ray diffraction (XRD).

Soft computing techniques for analysing the mechanical properties of egg shell powder-based concrete

The construction industry is increasingly focused on sustainability to reduce environmental impact. Researchers are actively exploring alternative materials to replace clinker-based binders. This study specifically investigates the use of eggshell powder (ESP) as a sustainable substitute in construction. Portland slag cement (PSC) is partially replaced by ESP in concrete production for this purpose. To assess the effectiveness of ESP in enhancing binder properties, the study analyses experimental data for compressive and flexural strength. Artificial Neural Network (ANN) modelling is employed for this analysis to predict material performance. The model undergoes training and testing using input data to ensure accuracy and reliability. The success of the study is demonstrated by high R2 values, with 0,9915 for compressive strength and 0,9921 for flexural strength, indicating that the ANN model closely matches actual material performance. Additionally, error analysis confirms the model's remarkable accuracy in predicting real-world results. Furthermore, the research highlights the exceptional potential of the developed ANN model, which can effectively predict the mechanical properties of construction materials containing ESP.

Assessment of flexural response of RC beams and unrestrained shrinkage of fiber-reinforced high-volume fly ash-based no-aggregate concrete and self-compacting concrete

The use of industrial byproducts as a substitute for cement in concrete production to improve its properties is becoming a widespread practice in producing sustainable concrete. Although research around the world emphasizes higher substitution levels of fly ash (FA) to accrue the benefits from the microstructure refinement, no attempt has been made to study the deflection behavior and drying shrinkage of concrete that is devoid of aggregates while supplementing 80% of cement with class F fly ash (F-FA). Two types of concrete are used to cast full-scale reinforced concrete (RC) beams of size 150×300×2200 mm. The first type is a novel no aggregate concrete (NAC) made up of 80% F-FA and 20% ordinary Portland cement (OPC). The second type is high-volume fly ash self-compacting concrete (HVFASCC), which has 60% F-FA as a cement supplement and is equivalent in compressive strength to NAC. The NAC is reinforced with polypropylene fibers (PF) in three varying volume fractions: 0.6%, 0.8%, and 1.0%. All the beams are tested under a simply supported four-point loading condition. The drying shrinkage strain and mass loss are measured for prisms of size 75×75×300 mm up to 220 days exposed at 20% relative humidity (RH) and 50 ºC temperature in a humidity oven for all the mixes. The mechanical properties are also assessed along with the water absorption (sorptivity). The results indicate that adding PF to the beams with NAC delays the formation of the first crack and improves the peak load, the ultimate load, and the ductility of the NAC beam. Additionally, the beams with PF exhibit lower mid-span deflection and ductile failure mode, improving the overall structural performance. Regarding drying shrinkage, the HVFASCC prisms record the lowest shrinkage strains of all mixes. Adding PF to NAC increases the initial and ultimate drying shrinkage strains. However, adding PF to NAC inhibits the rate of shrinkage strain over the test duration. This research enhances understanding of how PF affects no-aggregate concrete behavior, paving the way for more comprehensive construction materials.

Utilizing bio-based and industrial waste aggregates to improve mechanical properties and thermal insulation in lightweight foamed macro polypropylene fibre-reinforced concrete

This research intends to examine the potential of incorporating waste materials in place of coarse aggregates to augment the mechanical characteristics and thermal insulation of lightweight foamed concrete (LWFC), along with the inclusion of polypropylene (PP) fibres. The PP fibre exhibits excellent tensile strength and enhancement on thermal insulation properties of cementitious materials. In this study, eco-friendly bio-based oil palm shell (OPS) and robust solid polyurethane (SPU) aggregates derived from industrial waste were utilized as substitutes for conventional aggregates. Additionally, silica fume was partially incorporated as supplementary cementitious materials. The addition of PP fibre impacted the workability of the LWFC with the inverted slump value decreased by 1.7 %–17.5 %. The inclusion of PP fibre proportion increased from 0 % to 0.5 % revealed a positive result in mechanical properties and thermal insulation performance. The OPSSPU/0.5 showed the significantly increment of 40.4 % compressive strength, 102.9 % of splitting tensile strength, and 70.8 % flexural strength, respectively. The optimum result was obtained in the OPSSPU/0.5 mixture, which exhibited 3.74 MPa residual compressive strength. Furthermore, utilizing PP fibres brought about a significant reduction in thermal conductivity in the environmentally sustainable LWFC, leading to improvements ranging from 0.2 % to 16.3 % when compared to the control composition. Thus, these findings are essential for encouraging the adoption of such practices in the construction industry and contributing to the reduction of environmental impacts associated with sustainable concrete production.

Performance of foam concrete developed from construction and demolition waste

Unconscious industrialization, urbanization and consumption of natural resources pose a serious threat to the environment. The threat can be reduced by upcycling construction and demolition waste (CDW) in the production of foam concrete, which is a special type of concrete used especially for thermal insulation purposes. This study aims to use of CDW as a source of fine aggregate (0–4 mm) in the production of foam concrete mixtures. A series of mixtures with target density values between 500 and 900 kg/m3 were designed with various recycled aggregate and foam contents to investigate the physical, mechanical and thermal properties of the mixtures. Findings of the study reveal that mixtures with an elevated foam content possess a greater number of larger pores, which, as observed through microscopy, form interconnected structures that are porous. On the other hand, adding more fine recycled material (FRM) makes the matrix denser, which reduces the overall porosity and increases the packing density. In contrast to increased content of FRM, correlation coefficient of (−0.77) reveal a more powerful inverse relationship between risen level of foam content (−0.67) and the reduction ratio of fresh-to-dry density and the increase in compressive strength from 7 to 28 days. It is also known that mixes with more foam have better thermal insulation because they trap more air, while mixes with more FRM show an increase in thermal conductivity. The sensitivity analysis showed that changes in thermal conductivity are almost three times as sensitive for FRM content, which means they have a bigger effect than changes in foam content. Employing the Taguchi method, (R_0.714) emerges as the most efficient tested combination indicative of superior overall performance. Notably, the Taguchi method predicts the untested combination (0.100-F/C ratio + 0.714-R/C ratio) as potentially more efficient, suggesting avenues for further exploration and optimization. This study furnishes valuable insights into sustainable construction practices by reutilizing CDW in foam concrete production, thereby contributing to both environmental conservation and enhanced structural outcomes.

Exploring the synergistic effect of recycled glass fibres and agricultural waste ash on concrete strength and environmental sustainability

In today's age, finding harmony between construction endeavors and safeguarding the environment is of utmost importance. Consequently, there is a substantial requirement to explore the feasibility of utilizing waste materials as a replacement for traditional construction substances. Unfortunately, there is a lack of information regarding the possibilities of incorporating recycled glass, rice husk, and sugarcane bagasse ash into concrete production. This study investigated the viability of integrating recycled glass fibres and agricultural waste ash into concrete to bolster its strength and sustainability. When evaluating mechanical and durability properties across five mixtures, the concrete formulations ranged in fibre content percentages from 1% to 3% and in ash content percentages from 10% to 20%. Specifically, Mixtures 1, 2, 3, 4, and 5 contained 1% fibre and 10% ash, 2% fibre and 15% ash, 2.5% fibre and 20% ash, 3% fibre and 12% ash, and 1.5% fibre and 18% ash respectively. Mixture 2 and Mixture 5, boasting heightened fibre and ash content, showcased outstanding compressive strength at 38.5 MPa and 37.2 MPa, respectively, indicating a positive correlation between these materials and concrete strength. Conversely, Mixture 3, burdened with excessive fibre and ash content, witnessed diminished strength, underscoring the necessity for meticulous optimization. In terms of tensile and flexural strength, Mixture 2 and Mixture 5 displayed commendable performance, while Mixture 3 suffered setbacks from excessive content. Durability assessments unveiled Mixture 1 and Mixture 4's superior freeze-thaw resistance, with minimal mass loss (1.5% and 1.8%, respectively) and no visible damage, rendering them favorable choices for sustainable construction. Contrastingly, Mixture 3 exhibited poorer freeze-thaw resistance and higher environmental impact, highlighting the need for careful consideration in material selection. Overall, this study underscores the importance of optimizing concrete formulations through the integration of recycled materials, paving the way for stronger, more durable, and environmentally friendly construction practices.

Improving the mechanical performance of railway concrete sleepers using recycled materials: An experimental and numerical study

This paper explores the use of three waste materials available in vast quantities, including waste tires, glass bottles and bamboo furniture, in the manufacture of railway sleepers. Mechanical properties of recycled concrete have been studied to establish an optimal mix suitable for concrete railway sleeper manufacturing. Thus, 5%, 10%, 15% and 20% recycled rubber sands (RRS) by volume of fine aggregate are used instead of 30# and 60# mesh sizes of fine aggregate. Moreover, 20%, 40%, 60%, 80% and 100% of aggregate volume are replaced by recycled glass aggregate (RGA) particles. Furthermore, different percentages of recycled bamboo fibers (RBF) have been used as 1%, 2% and 3% by volume of concrete. According to the optimal concrete mixtures of RRS, RGA and RBF, twelve concrete railway sleepers are manufactured and tested for middle and rail seat bending strengths. Results show that ref. sleeper has almost 16% and 24% lower strengths than RGA sleeper in middle and rail seat, respectively, while ref. sleeper have higher strengths by 16% and 13%, and 18% and 7% than RRS sleeper (M60-R5) and RBF sleeper (B2) in middle and rail seat, respectively. The FEM results show that the ([Formula: see text]) of the RGA sleeper is the minimum ratio by 1.11 and 1.13 for rail seat and middle of sleeper, respectively, which is the best performance. In RBF sleeper FEM model, Bamboo fiber can only bear 5% and 8% of total stress in middle and rail seat, respectively, due to low mechanical properties of fibers.

Curing parameters development and long-term performance of ohmic heating cured conductive cementitious composites: A comparative study on fiber fraction

Ohmic heating (OH) curing is a new method for concrete production in cold areas, while the changing regularity for the curing parameters including electric voltage, current, resistivity and curing temperature during the curing process, and the long-term performance evolution law are still unrevealed. In this research, this method was used to fabricate carbon fibers (CFs) reinforced conductive cementitious composites under −20 °C, the early-age curing parameter and the long-term performance evolution law of the specimen were clarified. Higher CFs dosage showed benefits on the electrical conductivity and heating performance of OH pre-cured specimens. To be specific, simulation and experimental results evidenced that the electrical conductivity of fresh mixture was much improved with 0.6 vol% CFs with the electrical resistivity decremental ratio of 74.82 %. Also, the curing temperature was enlarged in the presence of 0.75 vol% CFs with the incremental ratio around 50 %, indicating the much-improved heating efficiency. Strength test results showed that 1-day OH pre-cured specimens possessed the comparable 150-day strength with RT prepared specimens. Moreover, the hydration products and pore structure test results further verified the feasibility of OH curing with high hydration forming ability and denser microstructure at longer duration. In addition, the “RER” was introduced to evaluate the variation law of electrical resistivity in further curing process, and the corresponding prediction equation was derived.

SAVING ENERGY RESOURCES DURING THE HEAT TREATMENT OF CONCRETE DUE TO THE USE OF ADDITIVES

Purpose of the work is heat treatment (steaming) of concrete and reinforced concrete products as an effective method of accelerating concrete hardening. Heat treatment of concrete is one of the most responsible construction processes. There are known cases when, due to the increased temperature of the concrete and large temperature differences, excessive temperature stresses arose, as a result of which cracks were formed. When choosing a method of heat treatment of concrete, you must first consider the possibility of using an energy saving method. Its extension is the introduction of additives – concrete hardening accelerators and cements of increased heat release (fast-acting and high-quality), as well as plasticizers and superplasticizers. Methodology. To reduce the duration of heat treatment or reduce the temperature of isothermal heating, it is proposed to use an additive obtained on the basis of the sludge of metal processing enterprises. The work uses standard research methods to determine the physical and mechanical properties of reinforced concrete and the quality of complex additives in accordance with DSTU 9208:2022, DSTU B V. 2.7-2.7-114-2002, DSTU B V.2.7-215:2009, DSTU B V. 2.7-214:2009. Findings. The effect of a complex slurry-based additive on the properties of reinforced concrete was investigated. The proposed additive increases the strength of concrete in all accepted heat treatment modes compared to the strength of concrete without such an additive. Originality of the obtained results is the following, theoretically substantiated and experimentally confirmed complex additive to concrete based on sludge (cake) of metal processing enterprises. The effect of the additive on the strength characteristics of concrete subjected to heat treatment under different regimes and natural hardening concrete is shown. Practical value. The results of the work are implemented in the production of reinforced concrete products and structures.

Modelling Wear Phenomena Specific to Mixer Blades in Concrete Production Plants

In the cement concrete manufacturing industry, mixers are critical pieces of equipment that play an essential role. Mixers ensure, by mechanically mixing the materials that make up the concrete, the homogeneity of the mixture. Since the active elements of the mixer in the concrete industry—the mixing blades—come into permanent contact with the mineral aggregates in the mixture formed by water and cement, they are permanently subjected to a strong abrasive–erosive wear process. The authors of this article were concerned with the establishment of tribological models for studying the wear of mixing blades, in order to identify the influence of their constructive parameters on the wear intensity. A complex model (Kraghelsky–Nepomnyashchi model) was adopted for the study. The modeling results revealed that the wear intensity decreases with an increasing blade angle of attack and increases linearly with increasing speed, as well as with an increasing friction coefficient. The modeling results confirm that the wear intensity is lowest when the mixing blade is inclined at a 60° angle, while the highest value is recorded for 30°. By identifying the angle at which the greatest wear of blades occurs, interventions can be made in the design of a more durable mixer (with the optimal installation angle of the mixer blades), thus requiring fewer corrective maintenance interventions. Based on these findings, we conclude that the complex model used in the experiment can provide a convenient and efficient tool for the study of erosive–abrasive phenomena.

Introducing a Novel Concept for an Integrated Demolition Waste Recycling Center and the Establishment of a Stakeholder Network: A Case Study from Germany

Using recycled aggregates has many positive environmental impacts because of the conservation of natural resources and minimization of waste. The use of recycled aggregates in downcycling processes is already common in Germany, whereas utilizing them to produce high-quality recycled concrete is rarely applied in practice. The reasons behind this lag have been investigated based on surveys and interviews with stakeholders. Miscommunication and missing information were identified in all stakeholder groups. Therefore, establishing a robust network and facilitating knowledge transfer by specifying the demand for recycled aggregates in the case study region have been considered as prerequisites. Therefore, the paper presents a novel concept of a stakeholder network for an integrated construction and demolition waste center. The conceptualization integrates the recycling companies and construction product manufacturers in one venue with research, service, and educational divisions. The design of the facilities is based on calculations regarding future construction activities and the demand for concrete production. The proposed concept aims to supply the region in the west of Germany with high-quality recycled products while also establishing a robust network that offers benefits in terms of logistical optimization and knowledge transfer.