Portland Cement Production Research Articles

Technologies for the reuse of demolition waste in the production of geopolymer-based building materials: prospects and opportunities

In a climate change scenario that is increasingly affecting our daily lives, it is essential to rethink the reuse of existing resources and avoid the exploitation of raw materials. If we consider the stock of existing buildings in Italy, we cannot ignore the fact that most of them are in a state of decay or in need of major maintenance; the recovery or demolition of these buildings generates a considerable amount of waste that has a negative impact on the environment, from transport to disposal. A sustainable design approach can achieve interesting results in terms of economic, environmental and social impact. Starting from the final phase of the life cycle of buildings, this paper aims to show the possibilities of recovering traditional building materials such as cement, brick and tuff. The use of innovative production technologies will allow the reintroduction of these materials to the market, with consequent benefits in all aspects of the ‘sustainability triad'. The aim of the work is to identify a practical, easy-to-use process for the production of eco-sustainable materials that, while retaining their intrinsic chemical-mineralogical characteristics, can be easily used in the context of the existing built heritage thanks to the compatibility between these new materials and the pre-existing substrate. The innovative results obtained as part of an international research project show how the use of demolition waste for the composition of geopolymer mixtures allows the reuse of large percentages of construction waste, while guaranteeing the mechanical performance of materials produced with traditional techniques, which have a high level of emissions; the production of geopolymers allows an 80% reduction in emissions compared to the production of Portland cement. The paper is intended to serve as a starting point for further in-depth application of the mixtures produced and to provide reflections and future research directions.

Potential use of high-volume of slag in pervious concrete: technical assessment and sustainability analysis

ABSTRACT Large porosity and interconnected pore structure allow pervious concrete to find interesting applications in urban pavement. At the same time, accounting for the exorbitant greenhouse gas emissions associated with Portland cement production, the application of supplementary cementitious materials (SCMs) in pervious concrete has received significant attention in studies. This research investigates the feasibility of developing pervious concrete by substituting a high volume of Portland cement with slag. Different mixtures were made to investigate the effects of high-volume slag content (60% and 80%), fine aggregate incorporation (10% and 15%) and combined use of SCMs (high-volume slag + silica fume) in pervious concrete. Concretes were tested for void content, compressive strength, permeability and abrasion resistance. Based on the results, although the compressive strength of pervious concrete was decreased by the inclusion of high-volume slag, it can be compensated to some extent by increasing the curing age. Furthermore, by decreasing the material cost and CO2 emissions up to 8.2% and 61.2% over plain pervious concrete, respectively, utilisation of high-volume slag can produce relatively more cost-effective and eco-friendly pervious concrete. In general, combined use of slag + silica fume or incorporation of fine aggregate at the optimum replacement ratio can be suggested to obtain higher strength and acceptable permeability in high-volume slag pervious concrete.

Utilization of Eggshell Powder as a Green Mortar Material

Recycling waste in cementitious materials promotes sustainable construction. It helps to prevent the depletion of natural resources while also reusing abundant recyclable wastes. Eggshells are one of these wastes that is being generated in large quantities because eggs are not expensive and have high nutritional value. On the other side, eggshell has a high content of calcium carbonate. It has a similar composition to the limestone powder used to produce Portland cement. This work investigates the effect of replacing a part of the cement with eggshell powder on mortar properties. The substitution rates were 5 %, 10 %, and 15 % of the cement’s mass. The results were compared with those of an ordinary mortar for the following properties: workability, compressive strength, flexural tensile strength, density in the hardened state, water absorption by total immersion, porosity accessible to water, depth of water penetration under pressure and chemical attack by sulfuric acid. The experimental results show that adding eggshell powder as a partial cement substitute up to 10% improved workability, increased compressive strength by about 10 % and flexural tensile strength by about 20 %, reduced density, and produced a more durable mortar by reducing porosity, water absorption, and water penetration depth under pressure. On the other hand, it decreased resistance to chemical attack by sulfuric acid. Thus, eggshell powder could be used in future construction materials to reduce carbon dioxide emissions.

Life cycle assessment of the climate change impact of magnesium phosphate cements formulated with tundish deskulling waste compared to conventional cement

Ordinary Portland cement (OPC) production significantly contributes to greenhouse gas emissions due to high resource consumption and CO2 output. It is therefore imperative to investigate alternative cements, such as magnesium phosphate cement (MPC), as a potential solution. This study is based on Life Cycle Assessment (LCA) methodology, comparing OPC with alternative magnesium phosphate cements (MPC) developed at the laboratory scale. The novelty of this study considers two types of alternative cements that use two different sources of MgO: MPC-MgO, developed with pure MgO, and MPC-TUN, formulated using tundish deskulling waste from steelmaking industry.The evaluated functional units are 1 tonne of cement, 1 m3 of cement paste, and 1 m3 of mortar, all of them are designed for the same function, which is as non-structural precast elements. The study assesses climate change impacts under two future scenarios: 1) electricity decarbonisation in the background economy using projections from Integrated Assessment Models and 2) electricity decarbonisation and a fuel switch in the cement kilns.The results indicate that MPC-TUN exhibits a lower impact of climate change in terms of CO2 emissions across all functional units and scenarios compared to the other materials. In the most ambitious climate scenario, MPC-TUN mortar exhibits 42% and 56% lower climate change impacts than OPC-CEM I and MPC-MgO mortars, respectively, demonstrating its potential as a more sustainable construction material. Although further research is needed on the applicability of MPC-TUN in construction, regulatory frameworks are advised to simplify barriers to expedite the adoption of sustainable alternative cements.

Characterization of Local Metakaolin Powder for Application as Geopolymer Precursor for Concrete Binder

It is known that metakaolin powder has proved to be a promising alternative concrete binder to Ordinary Portland cement (OPC). Portland cement production contributes about 8% to the global CO2 emission, which is detrimental to the environment and a major contributor to global warming. It is therefore pertinent to develop alternative costeffective and environmentally friendly cement materials. This study examines the performance of a Nigerian metakaolin-based powder as a sustainable material alternative to Portland cement. The Gwaram-Alkaleri Kaolin clay from Bauchi State, Nigeria, was calcined at 800°C for 3 hours as step prior to metakaolin formation. The powder specimens were characterized using XRF, moisture content, specific gravity, density, particle size distribution analysis and specific surface area techniques. Parametric analyses of the values of the specific gravity, density, particle size distribution and specific surface area were undertaken and comparisons and deductions made. The results revealed that Gwaram-Alkaleri metakaolin-powder can serve as a potential sustainable construction material for the Nigerian construction industry because of its availability, affordability, physical and chemical properties values, and significant reduction in CO2 emission, taking cognizance that the results positively indicate that it can be used as an alternative binding powder to cement in concrete and mortar production.

Efficient Management of Asbestos Waste Through Utilization as Mineral Additives in Portland Cement Production.

This article presents research on the effectiveness of utilizing asbestos waste, particularly chrysotile asbestos, in the production of Portland cement. The study aimed to evaluate the feasibility of transforming asbestos cement (Eternit) through thermal treatment and its enrichment with mineral additives, enabling its integration into the clinker synthesis process. Differences in the physicochemical properties of types of cement produced from conventional raw materials and those manufactured using asbestos waste were analyzed. The research findings indicate that the presence of asbestos in cementitious materials leads to a significant mass loss of 29.4% due to thermal decomposition. Chemical analysis revealed the presence of aluminum oxide (Al2O3) and iron oxide (Fe2O3) at levels of 4.10% and 3.54%, respectively, suggesting the formation of brownmillerite, a phase typical of cement clinker. Furthermore, compressive strength tests on asbestos-modified cements demonstrated comparable mechanical properties to reference cement (CEM I), indicating their potential applicability in construction. This study provides essential insights into the mineralogical composition of asbestos cement, which is crucial for developing effective methods for its safe disposal. It represents a significant step toward sustainable asbestos waste management and the promotion of innovative solutions in the construction industry.

Modeling and optimization of calcined bentonite replacement in the mechanical and durability properties of mortar

Currently, pozzolanic materials are mostly recommended to improve the properties of cement composite materials and reduce environmental pollution, challenging the world owing to ordinary Portland cement (OPC) production. Bentonite is mostly available natural pozzolana, however, extensive studies conducted on other clays like kaolin and some studies reported that bentonite exists in a consolidated form which requires heating activation methods. Therefore, it is essential to investigate the properties of bentonite in detail for its sustainable use, and it is novel to model and optimize the optimum bentonite calcination temperature and time for the best performance replacement in mortar. Hence, the present study investigates the optimum bentonite calcination temperature, calcination time, and replacement dose for mortar strength and free lime using the central composite design-response surface method (CCD-RSM). The mortar was prepared by replacing the calcined bentonite with cement weight with different values of the factor variables, bentonite dose, calcination temperature, and calcination time. Durability tests were conducted after 56 days. Thus, the results indicate that the selected model of response variables for compressive strength and free lime were significant, accurate, reliable, and had excellent fitness to the experimental work. Hence, CCD-RSM predicted the optimum for independent factors of bentonite dose 19.99 %, calcination temperature 799.99 °C, and calcination time 135.04 min and experimentally validated, which improved the strength by 24.94% and reduced free lime by 3.08% compared to the control mortar, besides reducing CO2 emissions compared to OPC production, which requires 1450 °C. Furthermore, the optimized bentonite replacement parameters have highly enhanced durability in different environments such as water, acids, salt, and elevated temperature compared to the control mixture at the age of 56 days.

Study of the concordance between various concrete deformation models and experimental data for uniaxial compression cases

There are various equations describing concrete stress-strain curves, each yielding different theoretical curves. An important scientific question is achieving the best correspondence to experimental data. The Geniyev theory inherently includes equations for three components of stress and strain. In contrast, the Eurocode and the Russian Building Code equations are provided for uniaxial stress conditions. This paper presents a comparison of theoretical curves for uniaxial compression based on Eurocode equations, the Russian Building Code, and Geniyev theory with experimental results from tests on prism and cube samples. The analysis includes deviations of the maximum stress points of theoretical curves from the corresponding experimental data. Numerical analysis is provided for both stresses and strains. A distinguishing feature of this work compared to existing research on Geniyev theory equations is that they are presented in a resolute form, incorporating three parameters: concrete compressive strength, tensile strength, and the initial modulus of elasticity. The importance of using secondary resources on the basis of industrial waste is understood by both governments of developed countries and business (production of Portland cement using ground metallurgical slag as a mineral additive at Novotroitsk, Magnitogorsk, Sterlitamak, Katav-Ivanovsk and other plants in the South Urals). The use of secondary raw materials requires the creation of technological infrastructure for processing of secondary raw materials, the costs of which can be quickly recouped due to the cheapness and availability of industrial secondary raw materials and freeing the territory from environmental pollution. In order to recoup the costs of the infrastructure, it is necessary to guarantee full compliance of the quality of pavement elements with the requirements of GOST R 59120-2021. Secondary raw materials have a great variety and laboratory analysis of the quality of pavement elements is required in order to design compositions with the best quality, satisfying all regulatory requirements. In our work the authors present the results of laboratory research and evaluation of the possibility of using clinker-free lime-slag binder based on the mineral product of soda production and metallurgical slags to strengthen and stabilize soils for their use in pavement structures in the construction of roads for various purposes and climatic zones. It is experimentally shown that the addition of lime-slag binder in the amount of 8-10% of the dry weight of both cohesive (loamy soil, loamy sand) and non-cohesive (fine sand) soil allows to obtain reinforced soil with improved strength and elastic-deformative characteristics, which can be used instead of scarce natural crushed stone and gravel in the construction of underlying layers of pavements in the construction and reconstruction of highways. This technology can be used not only in the Russian Federation, but also in a number of other countries, including those with hot dry climates (e.g., the Republic of Egypt).

تطوير معامل المرونة الفعال للخرسانة الصديقة للبيئة القائمة على مسحوق الزجاج

This study aims to develop an effective modulus of elasticity for eco-concrete using glass powder. Various theoretical models, including VOIGT and REUSS-VOIGT, are compared with experimental results. The REUSS-VOIGT model proved most accurate, particularly for cement replacement (5%-20%) and fine aggregate replacement (up to 25%). The REUSS-VOIGT model closely matches experimental results, especially after 56 days. To achieving sustainable development in the production of Portland cement by conserving natural resources and rationalizing their consumption for future generations. Keywords: Homogenization, Effective Modulus of Elasticity, Eco-concrete, Glass Powder, REUSS/VOIGT Model.

Alkali-fusion as an effective method for activating low-reactivity silicate wastes: A comparative study

Silicate wastes are used as supplementary cementitious materials (SCM) in Portland cement production, and as precursors to produce alkali-activated materials such as geopolymers to lower the environmental impact of construction. The high crystallinity of some of these wastes lowers their reactivity and hence the production of cementing hydrates. This paper includes a comparative analysis of the efficiency of alkali-fusion to activate three distinct types of silicate waste sourced from diverse sectors. The paper underscores the robustness of this method and its applicability in a wide composition range. It provides a solid foundation for the application of alkali-fusion across a wide spectrum of industrial waste types. Fly ash (FA), crop bottom ash (CBA) and aluminium processing sludge (APS); were fused with NaOH at 600 °C. XRD and FTIR analyses revealed that alkali-fusion disrupts highly cross-linked Si-O-Si structures transforming them into more reactive phases (sodium aluminosilicate and sodium silicates). Alkali-fusion is efficient even at low NaOH dosage(15 %). 15 % NaOH-fusion increased the mechanical activity index of FA, CBA and APS by 108.19 %, 494.61 % and 27.96 % respectively. The mineral composition of the wastes changed at 50 % alkali content: quartz was largely digested, and sodium silicate emerged as the dominant phase. After alkali-fusion, dense and compact matrices with rich hydrates were found evidencing the enhancement of the pozzolanic reaction. Alkali-fusion at relatively low temperature (600 °C) is successful in activating low-reactivity silicate waste, transforming the waste into valuable SCMs.

Цементное производство в России: заинтересованные стороны и эффективность регионального бизнеса в конце XIX века

The activities of “Petersburg Company for the production of Glukhoozersky Portland cement and other building materials” between 1879 and 1899, although only a initial period segment in its history, provides a holistic overview of phase that enterprise underwent on their path to becoming a large industrial firm. This study aims to improve and expand knowledge about the capacity and difficulties of industrial company to adapt to market changes and maintain their competitiveness, interregional coherence and organizational flexibility. This article explores changes in ownership and management structure and application of new technological practices during this period, which in turn led this enterprise to the status of the leader in the cement industry in capital. A case study of key group of shareholders (military engineers) tests the effectiveness of model of reconciliation of interests on results of twenty years of work of the company.

Alkali-Activated Slag as Sustainable Binder for Pervious Concrete and Structural Plaster: A Feasibility Study.

In the realm of sustainable construction materials, the quest for low-environmental-impact binders has gained momentum. Addressing the global demand for concrete, several alternatives have been proposed to mitigate the carbon footprint associated with traditional Portland cement production. Despite technological advancements, property inconsistencies and cost considerations, the wholesale replacement of Portland cement remains a challenge. This study investigates the feasibility of using alkali-activated slag (AAS)-based binders for two specific applications: structural plaster and pervious concrete. The research aims to develop an M10-grade AAS plaster with a 28-day compressive strength of at least 10 MPa for the retrofitting of masonry buildings. The plaster achieved suitable levels of workability and applicability by trowel as well as a 28-day compressive strength of 10.8 MPa, and the level shrinkage was reduced by up to 45% through the inclusion of shrinkage-reducing admixtures. Additionally, this study explores the use of tunnel muck as a recycled aggregate in AAS pervious concrete, achieving a compressive strength up to 20 MPa and a permeability rate from 500 to 3000 mm/min. The relationship between aggregate size and the physical and mechanical properties of no-fines concretes usually used for cement-based pervious concrete was also confirmed. Furthermore, the environmental impacts of these materials, including their global warming potential (GWP) and gross energy requirement (GER), are compared to those of conventional mortars and concretes. The findings highlight that AAS materials reduce the GWP from 50 to 75% and the GER by about 10-30% compared to their traditional counterparts.

Development of eco-efficient limestone calcined clay cement (LC3) mortars by a multi-step experimental design

Calcined clays and calcium carbonates can be used to reduce clinker factor in blended cements, offering significant economic and environmental benefits. Limestone calcined clay cements (LC3) combine them as supplementary cementitious materials (SCMs) for delivering a sustainable alternative to conventional Ordinary Portland Cement products, with envisioned applications in construction and rehabilitation of historical buildings.This study reports a chemometric approach to the development of LC3 mortars, targeting to minimize clinker content while maintaining or improving the technical characteristics. To evaluate their performance, apparent density, modulus of elasticity, open porosity, water absorption, flexural and compressive strength have been considered as responses. Multiple Linear Regression (MLR) and Principal Component Analysis (PCA) were employed in a three-step mixture-process design allowing to obtain LC3 mixtures with a 21 wt% reduction in clinker while achieving notable enhancements in the physical properties (open porosity −9% and water absorption −10 %), along with commendable increases in compressive strength (+17 %) when compared to benchmark mortars produced without SCMs. The successful integration of multivariate techniques in designing sustainable building materials is showcased, highlighting the potential of chemometric methodologies to reduce the environmental impact as well as to increase the performance of building materials.

Compressive Strength Study on Reactive Powder Concrete with 30% Quartz Sand and Variations in Fly Ash Composition as Partial Substitution of Cement

The concrete industry is considered environmentally unfriendly and unsustainable due to the significant consumption of natural materials. Currently, the industry predominantly uses Portland cement as its main ingredient, leading to an increase in Portland cement production. However, the use of fly ash can help make the concrete industry more sustainable in the future. Fly ash can be used as a partial replacement for Portland cement in concrete production. This study aims to determine the effect of fly ash variations on the compressive strength of reactive powder concrete. The research method used is experimental. The concrete mix design includes 30% quartz sand and fly ash variations of 0%, 5%, 10%, 15%, 20%, and 25%. The compressive strength test specimens are cylindrical with a diameter of 7.5 cm and a height of 15 cm. The resulting test specimens have a compressive strength of more than 41.4 MPa, thus qualifying as high-strength concrete. The compressive strength test results for fly ash variations of 0%, 5%, 10%, 15%, 20%, and 25% are 62.62 MPa, 66.27 MPa, 75.59 MPa, 68.78 MPa, 66.21 MPa, and 63.70 MPa, respectively.

Mechanical performance of eco-friendly self-compacting concrete (SCC) mixtures and two-way slabs partially containing cement kiln dust as cement replacement and internally reinforced with waste plastic mesh

A large quantity of cement kiln dust (CKD) is produced annually during the production of Portland cement. The majority of the produced CKD remains unused except in specific cases related to soil stabilization projects. The current research investigates the production of self-compacting concrete (SCC) mixtures, in which CKD is used as a substitute for cement in different weight proportions, 3 %, 6 %, 9 %, 12 %, and 15 %. The hardened mechanical properties of SCC, such as compressive strength, splitting tensile strength, and flexural strength, as well as the fresh state characteristics (i.e., slump flow diameter, T500, V-funnel, and L-box tests), were recorded and compared with the control mixture which was entirely cast using cement. Results revealed that with an increase in the CKD content beyond 6 %, the slump flow diameter of SCC mixtures significantly decreased. Also, the increase ratios in the V-Funnel flow time for self-compacting concrete mixtures, when replacing cement with CKD ratios of 3 %, 6 %, 9 %, 12 %, and 15 %, were 13.3 %, 30 %, 46 %, 58 %, and 66.7 % respectively, compared with the reference mixture. Additionally, the impact behavior of two-way SCC slabs cast using CKD ratios ranging from 3 to 15 % and internally strengthened using various patterns of recycled plastic mesh was investigated. Strengthening the SCC slabs using two layers of recycled plastic grids proved to be effective in preventing the projectile from penetrating the whole thickness of the SCC slabs, regardless of the CKD content.

Properties of fresh and hardened cement-based materials with waste glass as supplementary cementitious material: A review

The demand for cement is constantly growing; however, the industry is facing many challenges due to the excessive extraction of raw material, water demand, and CO2 emissions. To mitigate these challenges, cement can be partially substituted by recycled materials such as waste glass with pozzolanic properties. This substitution allows for the production of Portland cement (PC)-based materials that are more ecologically friendly and deliver similar or better performance than those containing only PC. In this context, the present paper provides an exhaustive review and analysis of the properties of fresh and hardened cement-based materials incorporating waste glass as a supplementary cementitious material. Substituting cement with waste glass produces PC-based materials with contrasting properties in the fresh state; however, waste glass improves both mechanical properties and durability. Despite the advantages of waste glass as a partial replacement for cement, research on the mechanical properties and durability at long term ages, as well as life cycle analysis, is essential.

Mechanical properties of blended cements affected by impurities in thermally activated clays

Abstract With the scarcity of raw materials, energy intensiveness and environmental burden connected with producing Portland cement, there is a growing need to find substitute binders. Thermally activated clay also appears to be a suitable material for partial cement replacement. However, not all clays are the same. It depends very much on the place of collection, its chemical and phase composition, and the activation temperature. This study compared six different types of clays fired at 600 °C in terms of quantitative phase analysis and mechanical strength results. In addition to the fineness of grinding and firing temperature, the clay composition had an immense impact on mechanical properties. Content of illite up to 20% was found to be beneficial, as this clay reached the highest mechanical strengths. Regarding the quartz, its presence did not harm the overall performance of thermally activated clays and the presence of calcite could cause the improvement of the mechanical strengths. However, the clay with the most miscellaneous composition caused the deterioration of compressive strength but reached much higher bending strength compared to pure cement.

Binary and Ternary Blended Portland Cements Containing Different Types of Rice Husk Ash.

Rice husk ash (RHA) is agricultural waste with high silica content that has exhibited proven technical feasibility as a pozzolanic material since the 1970s. Notwithstanding, its use in mortars and concrete is limited by the standards currently utilized in some countries where RHA production is high and the aforementioned pozzolanic material is not standardized. This is the case in Spain, one of the main rice producers in Europe. Nowadays, the high pressure placed on the Portland cement production sector to reduce its energy use and CO2 emissions has given rise to a keen interest in mineral admixtures for cement manufacturing. In this research, we intended to establish the contributions of different RHA types to the final blended Portland cement properties ("H" is used to identify RHA in standardized cements). The experimental results demonstrated that RHA with good pozzolanic properties (large specific surface and high amorphous silica content) had to be limited to 10% cement replacement because of the severe reduction in workability at higher replacement percentages. RHA with lower reactivity, such as crystalline RHA, or fly ash (FA) can be used to prepare binary and ternary blended cements with reactive RHA. It is possible to design the following cements: CEM II/A-H and CEM II/A-(H-V). It would also be possible to design cement (CEM II/B-(H-V) with replacement values of up to 30% and the same 28-day mechanical performance as observed for the Portland cement without mineral addition.

Enhancement of Perlite Concrete Properties containing Sustainable Materials by Incorporation of Hybrid Fibers

Utilizing waste resources in concrete manufacturing, while employing alternative components and minimizing the Ordinary Portland Cement (OPC) production, is a matter of great importance owing to several environmental and stability considerations. OPC is the fundamental component implemented in the conventional concrete production process. However, the OPC industry has raised environmental concerns since it produces mass amounts of carbon dioxide (CO2). A more sustainable substance, utilizing metakaolin as pozzolanic material and local ash as a filler can serve as an OPC substitute, thereby reducing the CO2 release into the environment. This work examines the impact of incorporating sustainable recycled copper fibers as well as alkali resistance glass fibers on the properties of perlite structural lightweight aggregate concrete containing local, sustainable materials. The research includes slump, density, and thermal conductivity tests along with tests conducted during the 7, 28, and 60 days of curing for compressive, flexural, and split tensile strength. The concrete was reinforced with 1% hybrid fibers by volume. The results reveal that adding fibers to lightweight concrete reduces the slump and increases density and thermal conductivity, while it also increases the compressive, flexural, and split tensile strengths.

Bond Stress Behavior of a Steel Reinforcing Bar Embedded in Geopolymer Concrete Incorporating Natural and Recycled Aggregates

The rise in greenhouse gases, particularly carbon dioxide (CO2) emissions, in the atmosphere is one of the major causes of global warming and climate change. The production of ordinary Portland cement (OPC) emits harmful CO2 gases, which contribute to sporadic heatwaves, rapid melting of glaciers, flash flooding, and food shortages. To address global warming and climate change challenges, this research study explores the use of a cement-less recycled aggregate concrete, a sustainable approach for future constructions. This study uses fly ash, an industrial waste of coal power plants, as a 100% substitute for OPC. Moreover, this research study also uses recycled coarse aggregates (RCAs) as a partial to complete replacement for natural coarse aggregates (NCAs) to preserve natural resources for future generations. In this research investigation, a total of 60 pull-out specimens were prepared to investigate the influence of steel bar diameter (9.5 mm, 12.7 mm, and 19.1 mm), bar embedment length, db (4db and 6db), and percentage replacements of NCA with RCA (25%, 50%, 75%, and 100%) on the bond stress behavior of cement-less RA concrete. The test results exhibited that the bond stress of cement-less RCA concrete decreased by 6% with increasing steel bar diameter. Moreover, the bond stress decreased by 5.5% with increasing bar embedment length. Furthermore, the bond stress decreased by 7.6%, 7%, 8.8%, and 20.4%, respectively, with increasing percentage replacements (25%, 50%, 75%, and 100%) of NCA with RCA. An empirical model was developed correlating the bond strength to the mean compressive strength of cement-less RCA concrete, which matched well with the experimental test results and predictions of the CEB-FIP model for OPC. The CRAC mixes exhibited higher costs but significantly lower embodied CO2 emissions than OPC concrete.