Replacement Of Natural Aggregates Research Articles

Eco-efficient steel slag concretes: an alternative to achieve circular economy

Abstract Annually billions of tonnes of aggregates are extracted to apply in civil construction generating environmental impacts and energy consumption. So, based on circular economy principles applying residues as aggregates is a good solution to reduce the mining activity and to generate a more efficient destination for the residues. Thus, this research aims to evaluate the technical, economic, and environmental performance of concretes produced entirely with steel slag aggregates. The concretes were characterized through physical properties, as specific gravity, water absorption, compressive and tensile strength. Durability tests (expansibility) were also conducted. The authors analyzed the cost assessment and environmental impact of steel slag concrete production as well. The incorporation of steel slag increases the compressive and tensile strength of concrete, analyzed in different ages. Additionally, the steel slag does not present expansibility when confined in the concrete matrix. The entire replacement of natural aggregates for steel slag allowed to reduce in 31% the cement consumption, a decrease of 140 kg/m3, for the same strength class. The environmental analysis showed that the incorporation of steel slag aggregates reduced the cement intensity of concrete and its impact. Regarding the cost assessment, the mixtures with steel slag presented a lower cost compared to the conventional one. These results indicate that steel slag aggregates could be used in a cleaner production of concrete, replacing natural aggregates with no injury. This research provides the feasibility of using steel slag aggregates in a cleaner and cheaper concrete production and contribute to the promotion of sustainable solutions for the construction sector through the circular economy principles.

Concrete with partial replacement of natural aggregate by PET aggregate—An exploratory study about the influence in the compressive strength

<abstract> <p>The expansion of cities contributed to the problems related to the accumulation of waste and lack of control over its management, there are still around 2400 dumps or uncontrolled landfills in Brazil. There is a large volume of polyethylene terephthalate (PET) improperly discarded. In turn, the construction industry has been looking for sustainable ways to produce concrete. This work deals with the analysis of the replacement of PET as a fine aggregate in concrete in the proportions of 5% and 15%. PET particles pass more than 75% in the 2.36 mm opening sieve and have more than 99% of their particle size retained in the 0.15 mm opening sieve. Concrete properties, compressive strength, tensile strength, water absorption and void ratio were evaluated and compared with the reference mix. In total, 45 specimens cast in concrete were used to complete the experiment. The results obtained showed that mixture compositions that incorporate PET as fine aggregates decrease compressive and tensile strength, increase water absorption and void index. The results obtained showed that blending compositions that incorporate PET as fine aggregates decrease compressive strength in about 14%, decrease tensile strength in about 7–11%, increased the void ratio in almost 20% and increased the water absorption in about 30%.</p> </abstract>

Compressive behavior of FRP-tube-confined concrete short columns using recycled FRP materials from wind turbine blades: Experimental investigation and analytical modelling

<abstract> <p>A major challenge in today's concrete construction is to lower its carbon footprint to the least possible level. This study provides insights on a new low-CO<sub>2</sub> alternative concrete whereby glass fiber-reinforced polymer (GFRP) materials from waste wind-turbine blades (WWTB)—termed as WWTB-GFRP—was utilized as: (ⅰ) replacement of Portland cement at 0%, 10%, 20%, and as (ⅱ) lightweight aggregate replacement for natural aggregates at 0%, 50%, and 100%. The resulting WWTB-GFRP concretes were used in concrete-filled fibre-reinforced polymer (FRP) tubes (CFFTs) whereby the latter serves as a stay-in-place formwork and external reinforcement. Pristine WWTB-GFRP materials (containing wood) and processed ones (by wood removal) were investigated. Results indicate that while both WWTB-GFRP powder and aggregates adversely affect the compression resistance (due to, respectively, the retarding effect of the powder and the slippery surface of the aggregates leading to reduced bonding with the bulk cementitious matrix), the confinement of WWTB-GFRP concrete with FRP tubes offers an innovative tool to restore the strength loss. In fact, valorizing WWTB-GFRP concrete in CFFTs allowed to increase the compressive resistance by more than 100%. Interestingly, under axial compression, FRP tube confinement shifted the stress–strain response from the conventional brittle response to a ductile one whereby the confinement affected the elastic and plastic responses differently. While FRP confinement increased in the elastic limit at higher WWTB-GFRP aggregate content, it resulted in lower slope of the plastic response at higher WWTB-GFRP aggregate content. An analytical assessment demonstrated that a WWTB-GFRP aggregate content of 55% will be optimum for enhancing both elastic and plastic responses. Building upon the ACI 440.2R-17 model for predicting the compressive response of confined concrete incorporating conventional aggregates, a modified model more sensitive to GFRP aggregates and with higher predictive ability was proposed. Research outcomes will contribute to recycling waste materials while endowing further sustainability to concrete.</p> </abstract>

Performance Evaluation of Plastic Concrete Modified with E-Waste Plastic as a Partial Replacement of Coarse Aggregate.

Plastic electronic waste (E-waste) is constantly growing around the world owing to the rapid increase in industrialization, urbanization, and population. The current annual production rate of E-waste is 3–4% in the world and is expected to increase to 55 million tons per year by 2025. To reduce the detrimental impact on the environment and save natural resources, one of the best solutions is to incorporate waste plastic in the construction industry to produce green concrete. This study examines the use of manufactured plastic coarse aggregate (PCA) obtained from E-waste as a partial replacement of natural coarse aggregate (NCA) in concrete. Six types of concrete mix with 10%, 20%, 30%, 40%, and 50% substitution of NCA (by volume) with PCA are prepared and tested. This study investigates the effect of manufactured PCA on the fresh and hardened characteristics of concrete. The properties of recycled plastic aggregate concrete (RPAC) studied include workability, fresh density, dry density, compressive strength (CS), splitting tensile strength (STS), flexural strength (FS), sorptivity coefficient, abrasion resistance, ultrasonic pulse velocity (UPV), and alternate wetting and drying (W–D). The results indicate that the CS, STS, and FS of RPAC declined in the range of 9.9–52.7%, 7.8–47.5%, and 11–39.4%, respectively, for substitution ratios of 10–50%. However, the results also indicate that the incorporation of PCA (10–50%) improved the workability and durability characteristics of concrete. A significant decrement in the sorptivity coefficient, abrasion loss, and UPV value was observed with an increasing amount of PCA. Furthermore, RPAC containing different percentages of PCA revealed better results against alternate W–D cycles with respect to ordinary concrete.

Evaluation of the Volume Stability and Resource Benefit of Basic Oxygen Furnace Slag and Its Asphalt Mixture Based on Field Application

Applying basic oxygen furnace (BOF) slag as aggregate in asphalt mixture is continuously investigated due to the increasing shortage of natural aggregate in recent years. However, the negative effect of BOF’s expansion in water greatly limits its further application in pavement construction. To address this problem, this paper studied the volume stability of BOF, and its asphalt mixture relied on actual engineering. The asphalt mixtures contained BOF aggregate was designed by the Marshall method with three different gradation types (AC-16, AC-20, and ATB-25). Besides, both laboratory samples and the core samples from field drilling were investigated in volume expansion rate after curing in a water bath. The economic and resource benefits of BOF replacement of natural aggregates were also analyzed. The results showed that the free calcium oxide content of BOF slag is positively related to the particle sizes. Nevertheless, the expansion rates of both the BOF aggregate and its asphalt mixture were less than 1%, which meant the BOF aggregate applied to the asphalt mixture meets the practical engineering requirements. The maximum allowable free calcium oxide content for large-grain size of steel slag is the smallest; it is also recommended that the expansibility of large-grain steel slag should be the first concern in the application. The resource assessment indicated that the use of steel slag for the construction of a trial section of one kilometer of single lane can save 967 tons of natural aggregates. The economic evaluation showed that the use of steel slag instead of natural aggregates for surface course construction could reduce the investment by 16.87%. The experimental methods and conclusions mentioned in this article provide stable references to enhance the development of sustainable pavement by recycling metallurgical slag in highway construction.

Feasibility of recycling concrete construction waste in environmental and economic sides

n light of the conditions experienced by Syria and due to the destruction and demolition of its buildings built up rubble and occupied a large area of its territory.
 Therefore, it was necessary to develop an appropriate strategy to study these debris and provide the ideal solutions to be able to benefit from them as much as possible and thus mitigate the harmful impact on the environment and the surrounding environment.
 The work is divided into two parts:
 First: The study focuses on one of the mechanisms of benefiting from the recycled aggregate by using them in producing concrete, after studying their characteristics(Sieve Analysis-density- Absorption) and then mixing them with natural aggregate as replacement of natural coarse aggregate at different rates(15-30-45-75-100)%.
 Six concrete cubes were made for each mixture and 3 cubes were broken after 7 days and the other after 28 days .
 it was concluded The relationship between the percentage of recycled aggregates and compressive strength, as well as the relationship between the percentage of stones and the rate of Absorption
 The results showed that the acceptable percentage of replacement of natural aggregates with recycled aggregates may reach 100% with the recording of values of resistance of up to 21.9Mpa .
 Second :The environmental and economic feasibility of using recycled aggregates has been studied the results showed that use 75% of the recycled aggregates in structural concrete works will reduce energy consumption and carbon dioxide emissions by 28% and 33%, respectively, and the economic saving rate is 63.71%. .
 
 Through this study two objectives can be achieved:
 First: removing large quantities of environmental pollution sources resulting from these wastes and thus achieving an environmental goal.
 Second: Provide other sources of concrete aggregates and thus protect the natural quarries and achieve an economic goal.

Evaluating the Possibility of Replacing Natural Fine Aggregates in Concrete with Recycled Aggregates

This paper presents an investigation on the possibility of replacing natural fine aggregates with recycled aggregates in concrete. The studied recycled aggregates were acquired from crushed waste concrete from demolishing works. The rate of replacement of natural fine aggregates was 10%, 20%, and 30% by weight. Compressive and flexural tensile strength of concrete incorporating recycled aggregates was investigated at 28 days of curing. The results show that the compressive and flexural strength of concrete is strongly affected by the percentage of recycled aggregates. It has been found that the strength decreases linearly with increasing recycled aggregate content. So, in order to apply recycled waste to concrete as fine aggregates, it is necessary to perform supplement research with appropriate additives to compensate for the loss of compressive and flexural strength.

Sustainable cement mortar with recycled plastics enabled by the matrix-aggregate compatibility improvement

Use of recycled waste plastics (RWPs) as the aggregates of concrete has attracted increasing attention for sustainable concrete manufacture with great environmental benefits. However, the replacement of natural aggregates by RWPs always results in degradation of mechanical properties due to poor aggregate-matrix compatibility, which greatly limits the uses of RWPs in practical concrete manufacture. In order to overcome this shortage, polymer (ethylene–vinyl acetate, EVA) coated RWPs, i.e. polypropylene (PP) and polyamide (PA), were investigated to tune the aggregate-matrix interactions in cement mortars. Density, strength and ductility were measured to assess the physical and mechanical properties of mortars with RWPs. Microstructure was qualitatively and quantitatively analyzed using scanning electron microscopy (SEM) with backscattered electron (BSE) mode and energy-dispersive X-ray spectroscopy (EDS). Results showed that single EVA addition into cement mortars kept the mortar density, decreased the compressive and flexural strengths, but increased the deformation and energy absorption to an extent of 100% in mortars with high EVA content. While the addition of RWPs witnessed a reduction in density of about 13–16%. The dual mix of 10% RWPs and 5% EVA mitigated the reduction trend in compressive strength and provided a slight increase (1.5%) in flexural strength compared with the mortars with single mix of 10% RWPs. The EVA addition built organic–inorganic interfacial transition zones (ITZs), improving the matrix-RWPs adhesion and coordinate their deformations. The mechanisms of compatibility improvement of EVA on RWP-cement mortar were proposed towards future design and fabrication of green concrete.

Ground Waste Tire Rubber as a Total Replacement of Natural Aggregates in Concrete Mixes: Application for Lightweight Paving Blocks.

The use of waste materials as alternative aggregates in cementitious mixtures is one of the most investigated practices to enhance eco-sustainability in the civil and construction sectors. For specific applications, these secondary raw materials can ensure adequate technological performance, minimizing the exploitation of natural resources and encouraging the circular disposal of industrial or municipal waste. Aiming to design and develop lightweight paving blocks for pedestrian or very light-traffic purposes (parking area, garage, sidewalk, or sports surfaces), this paper presents the material characterization of rubberized cement mortars using ground waste tire rubber (0–1 mm rubber powder and 1–3 mm rubber granules) to totally replace the mineral aggregates. Considering recommended requirements for concrete paving members in terms of mechanical strength, water drainage performance, acoustic attenuation, and dynamic and energy absorption behavior, a comprehensive laboratory testing is proposed for five different formulations varying the sand-rubber replacement level and the proportion ratio between the two rubber fractions. Tests highlighted positive and promising results to convert laboratory samples into pre-cast members. The “hot” finding of the work was to prove the feasibility of obtaining totally rubberized mortars (0 v/v% of sand) with suitable engineering performance and enhanced eco-friendly features.

Effects of fiber material in concrete manufactured with electric arc furnace slag: Experimental and numerical study

Over recent years, Electric Arc Furnace Slag (EAFS), a by-product of the steel-making industry, has been used as a replacement of natural aggregates to produce high-performance concrete. In EAFS concrete, fibers are normally added to improve post-cracking behavior, thereby prolonging the durability and range of applications of the composite. Despite the rise in its production, the mechanical performance of fiber-reinforced EAFS concrete is still poorly understood, posing important barriers to its daily use.This paper aims to study the effect of fiber materials (steel and synthetic) on EAFS concrete performance. To do so, the paper proposes, firstly, an experimental campaign and, secondly, a numerical simulation to model the effect of fibers both in the pre-cracking and post-cracking stages. Importantly, for the numerical study, an in-house Finite Element (FE) code is developed using interface elements to capture crack propagation. The FE code uses, as input, data obtained in the experimental campaign and is validated against previously unseen experimental results. The overall framework gives important insights on how fibers improve the post-cracking behavior of EAFS concrete and the relevance of fiber material in the overall performance. The validated numerical tool can be used in the future to design EAFS fiber-reinforced concrete structures and therefore increase the applicability of such composite material.

Natural sand substitution by copper mine waste rocks for concrete manufacturing

The management of waste rocks, generated by the mining industry, has become a global concern due to its high quantity, environmental impact, human health risks and high disposal costs. Thus, developing effective and sustainable solutions to properly manage this waste become necessary. In this study, the feasibility of using copper mine waste rocks (CMWR) as a substitute of natural sand in C25 concrete category (25 MPa at 28 days) was evaluated. In The first stage, the physical, chemical, mineralogical, geotechnical, and environmental characterizations of CMWR were conducted. Then, three concretes mixtures were designed and prepared including, reference concrete (CM-0), CMWR based concrete with 50% (CM-50) and 100% (CM-100) of natural sand substitution by CMWR sand. The concrete samples were tested to evaluate the mechanical performance and durability prediction of each mixture. The results showed that physical-mechanical and geotechnical properties of CMWR sand are so close to natural sand used in concrete manufacturing. Moreover, environmental finding confirmed that the CMWR is classified as non-dangerous materials. Furthermore, CMWR-based concretes met the requirements of the C25 concrete grade standard at all replacement levels. In terms of mechanical strength, the values were higher than that required by the standard (25 MPa). For the water absorption rate, which influences the durability of concrete, it was lower than the limit required by the standard (6%). Through the reuse of CMWR in concrete as a replacement for natural aggregates, environmental problems, costs and the depletion of natural resources can be minimized.

EXPERIMENTAL INVESTIGATION OF SCC WITH RECYCLED RUBBER AND RECYCLED CONCRETE AGGREGATE

<jats:p>The replacement of natural aggregates (NA) with alternative aggregates in concrete can contribute to the sustainable development of the construction industry. This paper aims to present research investigating the effects of recycled concrete aggregate (RCA) and crumb rubber (CR) utilization on the performance of Self-Compacting Concrete (SCC) mixtures in both fresh and hardened states. For this purpose, SCC mixtures with three different replacement levels of CR - 0%, 20% and 30% by volume for fine aggregate and 100% coarse RCA were prepared along with the reference mixture containing NA only. To assess the effects of NA replacement, the physical and mechanical tests were conducted on prepared SCC mixtures and corresponding results were analysed and compared.</jats:p>

Microstructural and Pore Skeleton Characteristics of Pervious Concrete Containing RAP Aggregates Using X-Ray Microcomputed Tomography and Scanning Electron Microscope

Pervious concrete is special class of concrete that has application in reducing stormwater runoff and mitigation of urban heat islands (UHIs). This paper studied the morphological and pore structure characterization of pervious concrete (PC) mixes when reclaimed asphalt pavement (RAP) aggregates are used as a replacement of natural coarse aggregates. Scanning electron microscope (SEM) and X-ray microcomputed tomography (XRT) were used to quantify the three-dimensional (3D) changes in the pore structure of PC mix when RAP aggregates are used. SEM investigation conducted on 100% RAP validated that the involvement of RAP aggregates on PC mixes causes asphalt cohesion failure, which will be predominant in reducing the structural and functional properties of PC mixes. The 3D pore structure showed the large number of spheroid-shaped pores when binary-graded PC mix was used. These new findings on the pore morphology will assist in optimizing the use as well as selection of RAP aggregates when used in PC.

Determination of the Physical-Mechanical Characteristics of Non-Cohesive Soils Stabilized with Fly Ash (Part II)

Abstract The unprecedented scale of road network development programs in our country requires the consumption of materials (natural aggregates, binders), often non-renewable and expensive, which are difficult to secure from traditional sources. Alternative solutions for the replacement of natural aggregates, binders, as viable alternatives to classical technologies, the adoption and continuous development of recycling technologies are concerns of researchers, designers and road builders. So, the stabilized mixtures successfully form the sub-grade layers of the rigid road structures or both the sub-grade layers and the base layers of the semi-rigid structures (Zarojanu, 1976). Compared to traditional, untreated, thick foundations, the stabilized foundations, consisting of a series of thinner layers (assizes), with considerably increased rigidity, ensure a more judicious distribution of traffic loads for lower overall thicknesses of the road structure (Boboc, 1995).

Experimental Study on Properties of Concrete Using Shredded Plastic Waste and M-Sand as Partial Replacement of Fine Aggregate

Disposal of large quantity of plastic causes land, water, and air pollution etc.., so a study is conducted to recycle the plastic in concrete. This work investigates about the replacement of natural aggregate with non-biodegradable plastic aggregate made up of mixed shredded plastic waste in concrete. Several tests are conducted such as compressive strength of cube, compressive strength of cylinder, flexural strength test of prism to identify the properties and behavior of concrete using shredded plastic aggregate. Replacement of fine aggregate weight by 0%, 5%, 10%, 15%, 20% with shredded plastic fine (PF) aggregate and manufactured sand (M-Sand). Totally 30 cubes, 30 cylinders and 30 prisms are casted to identify the compressive strength, cylindrical compressive strength, and flexural strength respectively. Casted specimens are tested at 7, 14 and 28 days. The identified results from concrete using shredded plastic aggregate are compared with conventional concrete. Result shows that initially there is increase in mechanical properties then there is reduction in mechanical properties due to addition of shredded plastic aggregate added concrete. This reduction in strength is mainly due to poor bond strength between cement and shredded plastic aggregate.

Utilization of Crushed Pavement Blocks in Concrete: Assessment of Functional Properties and Environmental Impacts.

Production of concrete is connected to extensive energy demands, greenhouse gases production or primary sources depletion. Reflecting current economical, social, or environmental trends, there is strong pressure on mitigation these requirements and impacts. The exploitation of secondary- or waste materials in production processes has therefore a great potential which is not related solely to binders but also to fillers. In this light, this paper aims at thorough investigations of concrete mixtures with crushed concrete pavements as partial or full replacement of natural coarse aggregates. The research combines experimental techniques to quantify the influence of the substitution on basic physical, mechanical, and heat/moisture transport/storage parameters. The experimental data obtained are further exploited as input data for computational prediction of coupled heat and moisture transport to assess the influence of the aggregates substitution on hygrothermal performance of the built-in concretes. In the last step, the environmental impacts are assessed. Since the changes in the hygrothermal performance were found to be insignificant (i), the compressive strength were improved by up to 25% (ii) and most of the environmental impact indicators were decreased (iii) at the same time, the findings of the research presented predeterminate such a reuse strategy to wider application and use.

Performance evaluation of sustainable recycled aggregate concrete with colloidal nano-silica

The use of recycled coarse aggregate (RCA) in concrete is a sustainable thing in the concrete industry. But during the recycling process of concrete waste for RCA, some mortar will be adhered to it and the coarse aggregate may have got fractured; if it was used in making the recycled aggregate concrete (RAC), it may produce inferior-quality RAC. To enhance its mechanical and microstructural characteristics of RAC, an admixture in the form of colloidal nano-silica (CNS) which are highly reactive in producing C-S-H gel with the hydrated cement and effectively fill the microvoids and crack in RAC and improves the interfacial transition zone (ITZ) was considered in the present experimental investigation with 100% replacement of natural coarse aggregate (NCA) with RCA and partially replacing the cement with CNS (0%, 1%, 2% and 4% by weight). The detailed analysis of the experimental results revealed that the replacement of cement with CNS in both the NAC and RAC mixes has enhanced the mechanical and microstructural characteristics; most notably, reduction in voids and improvement in the ITZ. The concrete mixes even with 100% RCA and partial replacement of cement with CNS satisfies the design requirements for its application in the construction industry.

Combined Freeze-Thaw and Chloride Attack Resistance of Concrete Made with Recycled Brick-Concrete Aggregate.

The objective of this study was to investigate the physico-chemical properties of concrete made with recycled brick-concrete aggregate, which was the mixture from waste concrete and waste clay brick in a 7:3 ratio. Specifically, this paper investigated the mechanical properties, freeze-thaw resistance, and distribution of water-soluble chloride ions of concrete containing RBCA and fly ash (FA) against combined freeze-thaw and sodium chloride attack. Concrete containing RBCA replacement of natural coarse aggregate and fly ash replacement of Portland cement was subjected to 45 freeze-thaw cycles containing sodium chloride solution. It was discovered that the mechanical properties and freeze-thaw resistance to sodium chloride attack gradually decreased with increasing RBCA content. At the same time, a replacement level of 15% FA by weight resulted in significant improvements in compressive strength and resistance to combined freeze-thaw and chloride attack. Furthermore, using a replacement of 30% FA by weight markedly improved the resistance to chloride ion penetration of concrete due to the lowest water-soluble chloride content.

Rubberized Geopolymer Composites: Value-Added Applications

The discovery of an innovative class of inorganic polymers has brought forth a revolution in the history of construction technology. Now, no energy-intensive reactions at elevated temperatures are essential, as found in the case of contemporary cement production. In addition to their attributes of low energy and a mitigated carbon footprint, geopolymeric composites can incorporate diversely originated and profound wastes in their manufacturing. As of today, profoundly accessible landfills of rubber tyre waste negatively impact the environment, water, and soil, with many health hazards. Their nonbiodegradable complex chemical structure supports recycling, and toxic gases are emitted by burning them, leading to aesthetic issues. These, altogether, create great concern for well-thought-out disposal methods. One of the achievable solutions is processing this waste into alternative aggregates to thus generate increased economic value whilst reducing primary aggregate consumption through the incorporation of these vast automobile solid wastes in the manufacturing of geopolymer construction composites, e.g., binders, mortar, concrete, etc., produced through the process of geopolymerization as a replacement for natural aggregates, providing relief to the crisis of the degradation of restricted natural aggregate resources. Currently, tyre rubber is one of the most outstanding materials, extensively employed in scores of engineering applications. This manuscript presents a state-of-the-art review of value-added applications in the context of rubberized geopolymer building composites and a review of past investigations. More significantly, this paper reviews rubberized geopolymer composites for their value-added applications.

Resistance to the alkali-aggregate reaction of sustainable mortars produced with scheelite tailings in replacing natural sand aggregates

This work produced coating mortars with scheelite tailings (ST) in total replacement of natural sand aggregate. The chemical and mineralogical composition of the scheelite tailings was determined by X-ray diffraction (XRD) and X-ray fluorescence (XRF). Mortar samples with a mass proportion of 1:2:9 (cement: lime: sand/scheelite tailings) were prepared with and without the scheelite tailings. The mortars were evaluated by mercury intrusion porosimetry and compressive and flexural strength tests. The resistance to the alkali-aggregate reaction was assessed from the bar expansion test and by scanning electron microscopy (SEM) in the crack and pore regions. The results indicate that until the 22nd day, the scheelite tailings were not reactive; however, in 28 days, the expansion was deleterious. SEM images did not detect the presence of amorphous alkaline gel characteristic of the alkali-aggregate reaction. Therefore, although the mortar with scheelite tailings aggregate has shown the deleterious potential to 28 days, mechanical tests indicate that it has the potential to be used as a coating mortar.