Recycled Fine Aggregate Research Articles

Concrete improvement incorporating recycled powder and aggregates treated via a combination of calcination and carbonation: The impact behaviors

Property improvement is a key process for achieving high value-added utilization of recycled powders (RPs), recycled fine aggregates (RFAs) and recycled coarse aggregates (RCAs) in concrete. The purpose of this study is to improve the quality of recycled concrete (RC) incorporating recycled powder and aggregates by optimising the combined calcination and carbonation pretreatment, focusing on the effect of recycled powder and aggregates pretreatment on the impact behavior of RC. For this purpose, a series of impact tests were conducted by using a Ø 100-mm splitting Hopkinson pressure bar apparatus to examine the influence of the reaction conditions on the physical and microstructural properties of the modified RCs. The various tested parameters included the following: (1) calcination temperature (25 °C, 200 °C, 400 °C, 600 °C and 800 °C); (2) carbonation time (0, 3, 6, 12 and 24 h); (3) RP content (0 and 10%); (4) RFA content (0 and 25%); (5) RCA content (0, 50 and 100%) and (6) strain rate (20 s−1 to 120 s−1). In addition, the test results from the impact properties of the modified RCs were compared with those under quasi-static loadings. The results showed that a combination of calcination at 400 °C (for RP at 600 °C) and carbonation for 24 h significantly improved the performance of RPs, RFAs, and RCAs and reduced the negative impact of their addition on the impact resistance of RC. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that the coupling pretreatment was beneficial for the development of the RC microstructure; a stronger bond between the matrix and recycled material was achieved, and the interfacial transition zone (ITZ) was also effectively improved. Finally, a recalibration model based on the RPs, RFAs and RCAs was proposed to predict the dynamic increase factor (DIF) of the RC under impact loading.

Tensile behavior analysis and prediction of steel fiber recycled fine aggregate concrete

This paper investigated the splitting tensile and axial tensile behaviors of steel fiber recycled fine aggregate concrete (SFRFAC). The effects of recycled fine aggregate (RFA) replacement ratio, steel fiber volume fraction, steel fiber type and silica fume content on the tensile properties of SFRFAC were studied. The digital image correlation (DIC) technique was utilized to observe the surface crack development of SFRFAC specimens. The results show that the splitting tensile strength of SFRFAC was greater than the axial tensile strength. Furthermore, the use of RFA decreased the splitting tensile strength, axial tensile strength and axial tensile elastic modulus of SFRFAC, and increased its axial tensile peak strain, while the addition of steel fiber and silica fume enhanced the splitting tensile strength, axial tensile strength, axial tensile peak strain and axial tensile elastic modulus of SFRFAC. Finally, the relationship between splitting tensile strength and axial tensile strength and the relationship for the axial tensile stress–strain of SFRFAC were proposed, respectively. Moreover, the modified damage constitutive model was also proposed by considering the damage threshold and the damage variable correction parameter to make the damage constitutive model more reasonable.

Impacts of biomimetic self-healing of Lysinibacillus boronitolerans immobilized through recycled fine and coarse brick aggregates in concrete

Recycling waste bricks for concrete is cost-effective and eco-friendly but may impact strength and durability. A promising solution is biomimetic self-healing concrete that uses bacteria to repair cracks. The efficacy of this approach is contingent upon the bacterial strain, carrier medium, medium size, and immobilization utilized. Nevertheless, it remains uncertain how carrier size affects biomimetic self-healing concrete when the same carrier substance and immobilization technique are used. This study explored using Lysinibacillus boronitolerans (LBBT) to develop biomimetic self-healing concrete using recycled fine brick aggregate (RFBA) as a carrier medium. Recycled coarse brick aggregate (RCBA) was also employed for the relative evaluation of the impact of carrier size in biocrete. Results revealed that adding LBBT to concrete through RFBA resulted in significant improvements in strength and toughness. Compressive, split tensile, and flexural strength increased by 16.2%, 17.6%, and 22.0% respectively, while compressive and flexural toughness improved by 51.0% and 27.6%. The abundant RFBA particles ensured the even distribution of LBBT throughout the mixture. RCBA immobilization facilitated self-healing, achieving 0.6 mm of crack healing with 89.7% compression strength recovery and a 26.0% healing potential. The achievement can be attributed to the macro-voids and the stiffened structure of RCBA. Additionally, forensic investigations confirm the presence of microbial induced carbonate precipitation. Thus, RFBA is a promising immobilizer for LLBT, exhibiting a greater impact on mechanical performance due to its smaller particle size. In contrast, RCBA facilitates self-healing by entrapping the biomimetic agent, despite its lower abundance.

Improvement of mechanical properties and carbonation durability of recycled fine aggregate engineered cementitious composites for structural strengthening

External wrapping with engineered cementitious composite (ECC) extends the service life of concrete structures after reinforcement corrosion, but the low economics of this strengthening measure limits its application. In this study, recycled fine aggregate engineered cementitious composite (RFA-ECC) for structural strengthening was prepared using recycled fine aggregate (RFA) as a 100% replacement for natural fine aggregate (NFA). The effects of fiber and fly ash on the mechanical properties of RFA-ECC were investigated for component optimization design. Additionally, the carbonation durability of RFA-ECC with initial crack damage was investigated by a preloaded carbonation test, and a carbonation model of RFA-ECC was established. The results demonstrated that the compressive strength of ECC decreased by 13.75% when RFA replaced NFA completely, but the flexural strength was still as high as 7.2 MPa. The self-cementing ability of RFA densifies the matrix microstructure, thereby enhancing the fiber bridging stress capacity. The tensile strength of RFA-ECC reached 2.5 MPa at 2% fiber volume fraction, which was 5.77% higher than that of natural ECC. The increased fly ash content enhanced the matrix strain capacity, but the tensile strength decreased significantly. The economic analysis indicates that RFA-ECC, with a 1.5% fiber volume fraction and 40% fly ash content, meets the performance requirements while offering a cost-saving of 15.4%.

Using recycled aggregate and powder from high-strength mortar waste for durable cement-based materials: Microstructure and chloride transport

The large-scale application of high-strength mortar in engineering will inevitably generate a significant amount of high-strength mortar waste in future, but there has been relatively limited research to date on the reuse of high-strength mortar waste as recycled building materials. Therefore, this paper studied the microstructure and chloride transport in cement-based materials using recycled fine aggregate (HCRA) and recycled powder (HCRP) derived from high-strength mortar waste or from high-strength mortar waste separated from high-strength concrete waste recycling. HCRA had much better physical and mechanical properties than ordinary recycled aggregate. HCRP contained some active components, and mixing appropriate HCRP refined paste pore structure; besides, reducing HCRP particle size could further refine the pore diameter of HCRP doped mortar. The strength of mortar first raised and then declined with the increment of HCRA replacement, but the strength decreased as HCRP was incorporated. Incorporating HCRA slightly reduced the chloride migration in mortar, and the mortar with HCRA had better chloride resistance than the mortar with recycled fine aggregate crushed from ordinary mortar waste. Mixing appropriate HCRP could reduce the chloride diffusion coefficient and chloride concentration. Reducing HCRP particle size further declined the chloride transport in HCRP blended mortar, and the mortar with HCRP had superior chloride resistance to the mortar with ordinary recycled powder. Mixing HCRA and HCRP both raise the chloride binding capacity. Particularly, fully recycled mortar with 100% HCRA and 30% HCRP exhibited even better chloride resistance than reference mortar. Incorporating appropriate HCRA and HCRP could prepare durable cement-based materials with good chloride resistance.

Mechanical, durability and sustainability assessment of rendering mortar with synergistic utilisation of recycled concrete and ceramic insulator fine aggregates

In alignment with Sustainable Development Goals (SDGs) set by United Nation, this study investigates eco-friendly alternatives which can be used in various construction activities. This research explores the potential of utilising recycled concrete fine aggregates (RCFA) and Ceramic Insulator Fine Aggregates (CIFA) as a complete substitute for natural river sand in rendering mortar applications, thoroughly examining mechanical and durability properties. The initial results demonstrated that the mortar mix made using 50% replacement of river sand with RCFA showed comparable results of compressive strength when compared with the control mix containing only river sand. However, the results of shrinkage and durability demonstrated the adverse effects of the use of RCFA in mortar with shrinkage being almost double to that in control mix. In order to enhance the performance of the mortar, the CIFA were added along with 50% RCFA. The addition of 50% CIFA along with 50% RCFA resulted in overall better performance with approximately 25% and 10% increase in compressive and adhesive strength, respectively. Additionally, the waste-incorporated mortar also outperforms the control mix in durability tests involving exposure to 5% HCL and H2SO4 solutions over 180 days. The results showed 2–3% lower mass and compressive strength loss compared to control mix indicating the better mechanical and durability performance of mortar mix. The SEM and XRD microstructure analysis techniques were also made use to further validate the mechanical and durability findings. To assess the sustainability of the mortar mixes, life cycle assessment (LCA) was conducted with a “cradle to gate” boundary condition. Furthermore, the Analytical Hierarchy Process (AHP) was employed to evaluate and rank the various mortar mixes based on their mechanical, functional (shrinkage and adhesive strength) and durability properties, along with sustainability indicator. The results of the AHP reveals that the mortar mix with 100% waste incorporation ranks first among all the other alternatives, highlighting its potential as an effective and sustainable option compared to conventional rendering mortar.

Fresh and mechanical properties of concrete containing recycled fine aggregate as partial sand replacement

Concrete is one of the world's oldest established construction materials, having been employed in the creation of various structures throughout history. Due to increased demand, the materials used in concrete buildings, particularly granite aggregates and natural sand, are rapidly decreasing. Continuous use of these natural resources has a detrimental effect on the ecosystem. Simultaneously, concrete waste from construction and demolition waste (CDW) created landfills and environmental damage. Therefore, recycled fine aggregate (RFA) was utilized in this research to replace natural sand. This experiment used a total of five mixtures. Mixes with RFA replacement amounts of 0%, 10%, 20%, 30%, and 40% were cast and subjected to water curing. The slump test, compressive test, and water absorption test were done for concrete containing various percentages of RFA. Incorporation of RFA up to 20% enhances the concrete strength. Generally, concrete produced using RFA up to 40% exhibits water absorption not exceeding 10% enabling it to be categorized as good quality concrete. The approach of channeling concrete waste to be utilized as recycled fine aggregate would decrease waste dumping at landfill and mining of sand from local rivers.

Effect of using sugarcane leaf ash and granite dust as partial replacements for cement on characteristics of ultra-high performance concrete

A significant quantity of cement is necessary for the production of ultra-high-performance concrete (UHPC). However, some environmental issues are associated with cement production. The worldwide agricultural growth increases ash from agricultural waste (AW). Furthermore, industrial waste (IW) generated throughout the stone-cutting and processing has increased due to the growing demand for granite stone in construction. This research conducted a unique study that involved comparing the use of sugarcane leaf ash (SLA) as AW and granite dust (GD) as IW as partial substitutes for cement in the production of eco-friendly UHPC. The effect of employing SLA and GD with replacement ratios ranging from 20% to 50% on the mechanical and transport properties of UHPC was studied. In addition, this research investigated the effectiveness of partial replacement of natural fine aggregate (NFA) by recycled fine aggregate (RFA) with ratios ranging from 25% to 100% on the UHPC qualities. Moreover, the effect of elevated temperatures on the UHPC and the microstructural examination were investigated. Results demonstrated that the optimum replacement ratio of SLA or GD from cement was 20%, showing the best mechanical characteristics of the UHPC. For example, after 28 days of casting, the compressive strength increased by 12.16% and 8.44% when SLA and GD were added to the UHPC mix, respectively. Additionally, the 25% replacement ratio of RFA from NFA presented the best mechanical and transport properties of the UHPC. The mixes containing SLA positively affected the UHPC higher than those containing GD.

Comparative Study of Concrete Using Recycled Fine Aggregate

Abstract: Waste handling and management is the major problem faced by countries in the modern era. Concrete demolition waste has been one of the sources of creating environmental pollution. There have been many strength and durability studies taking place to analyze the concrete made with fine aggregate which has been recycled from old concrete structures and proved high strength compared to the concrete made with new materials. Those research works are limited in analyzing finer divisions of the concrete made with the aggregates which have been recycled. This paper concentrates on the applications of recycled Fine Aggregate (RFA) as a partial replacement instead of the fine aggregates available naturally to prepare the concrete. With a view to the above needs, the present study is aimed to determine the strength properties of RFA concrete depending on the various content of RFA and to compare them to the strength properties of concrete made with natural fine aggregates (NFA). Fine aggregates of high FM of 2.6 were used for recycled and natural concrete. After performing the compressive strength test with partial replacements of 30%, 40%, 50%,60%,70% and 80%of RFA with NFA, it was found that concrete made with the following replacements RFA has less strength than concrete made with NFA but with not much difference. So, RFA can be used as a replacement for NFA in concrete production. In addition, partial replacement of RFA can be used in structures of less importance such as temporary walls, the base of roads, light traffic roads, pavements in college campuses etc.

A green ultra-high performance geopolymer concrete containing recycled fine aggregate: Mechanical properties, freeze-thaw resistance and microstructure

The shortage of natural aggregate poses challenges and offers new opportunities for the construction industry. Under this background, the emergence of recycled aggregates sheds new lights on building aggregate. In this study, a green ultra-high performance geopolymer concrete (UHPGC) containing recycled fine aggregate (RFA) was prepared. To assess the feasibility of RFA and reveal the reaction mechanism of UHPGC, the reaction process, mechanical properties, freeze-thaw resistance and microstructure were systematically studied. The heat evolution results indicate that the control of reaction process could be achieved by adjusting the precursor component. A compact microstructure with extremely low porosity could be formed in the UHPGC specimens, which contributes to their good mechanical properties and freeze-thaw resistance. Good compatibility in the interface transition zone between fiber, paste and RFA could be observed, indicating great potential in the manufacture of UHPGC by alkali-activation technology. A considerable environmental benefit could be obtained in UHPGC when compared to ordinary ultra-high performance concrete (UHPC). This study is expected to offer more insights into the application of recycled aggregate and the manufacture of green UHPC.

Using limestone calcined clay cement and recycled fine aggregate to make ultra-high-performance concrete: Properties and environmental impact

A comprehensive investigation concerning the mechanical properties and microstructural characteristics of ultra-high-performance concrete (UHPC) using different dosages of limestone calcined clay cement (LC3) and recycled fine aggregate (RFA) was conducted. Results demonstrated that the compressive strength using 15% LC3 and 30% RFA is comparable to the control group, and the tensile strength of UHPC using 30% LC3 is comparable to the control mix-ID. Incorporation of LC3 generates additional hydration products. The addition of LC3 improved the pore size distribution and reduced porosity. The results of nanoindentation testing showed that using LC3 and RFA improved the performance of interfacial transition zone, contributing to the achievement of considerable mechanical resistance. Finally, life cycle analysis revealed that using LC3 and RFA could reduce the environmental impact.

Development of Sustainable Engineered Cementitious Composites by Incorporating Local Recycled Fine Aggregate.

In this study, sustainable engineered cementitious composites (ECC) exhibiting high tensile strength as well as high tensile strain capacity were successfully developed by incorporating polyethylene (PE) fiber, local recycled fine aggregate (RFA), and limestone calcined clay cement (LC3). The improvement in tensile strength and tensile ductility was attributed to the self-cementing properties of RFA as well as the pozzolanic reaction between calcined clay and cement. Carbonate aluminates were also generated owing to the reaction between calcium carbonate in limestone and the aluminates in both calcined clay and cement. The bond strength between fiber and matrix was also enhanced. At the age of 150 days, the tensile stress-strain curves of ECC containing LC3 and RFA shifted from a bilinear model to a trilinear model, and the hydrophobic PE fiber exhibited hydrophilic bonding performance when embedded in RFA-LC3-ECC matrix, which could be explained by the densified cementitious matrix as well as the refined pore structure of ECC. Moreover, the substitution of ordinary Portland cement (OPC) by LC3 resulted in energy consumption and equivalent CO2 emission reduction ratios of 13.61% and 30.34%, respectively, when the replacement ratio of LC3 is 35%. Therefore, PE fiber-reinforced RFA-LC3-ECC demonstrates excellent mechanical performance as well as considerable environmental benefits.

Study on mechanical properties and microstructure of recycled fine aggregate concrete modified by Nano-SiO2

Study on mechanical properties and microstructure of recycled fine aggregate concrete modified by Nano-SiO2

Basic creep behavior and modeling of recycled coarse and fine aggregate concrete

This paper aimed to experimentally investigate the influence of fine recycled aggregate (FRA) replacement ratio on the basic creep of RAC with different coarse recycled aggregate (CRA) replacement ratios and water-to-cement ratios (w/c), i.e., the compounding effect among FRA, CRA and w/c. To achieve this, fifteen groups of specimens were prepared for long-term tests to measure the final basic creep value and basic creep development trend for concretes with different FRA/CRA replacement ratios and w/c. Test results showed that the FRA, CRA and w/c had a significant compounding effect on the basic creep behavior of RAC. Based on the traditional B4 model by Bazant (2014), a new basic creep model was derived to account for all the aforementioned influences. The model was then benchmarked against all the collected test data.

Testing of precast recycled aggregate concrete shear wall with pressed sleeve connection subjected to cyclic loading

AbstractThe pressed sleeve connection is a new type of connection technique reported in China recently. To explore the possibility of combining the advantages of pressed sleeve connections and recycled aggregate concrete (RAC) in precast concrete, the seismic performance of precast shear walls with pressed sleeves and recycled fine aggregate (RFA) concrete was investigated through a thorough experimental programme. A total of seven precast shear wall specimens and one cast‐in‐situ specimen were fabricated and tested under lateral cyclic loading, considering the effects of the aspect ratio, the axial compression ratio, and the RFA content. The failure modes, hysteretic behavior, bearing capacity, energy dissipation, stiffness and shear distortion of the specimens, as well as the strains of the steels, were reported and discussed. The test results demonstrated that the pressed sleeve connections were capable of transmitting both tensile and compressive forces between reinforcements, and the precast shear walls with pressed sleeve connections exhibited the same hysteresis behavior, strengths, ductility coefficient and energy dissipation capacity as the cast‐in‐situ counterpart. Moreover, the seismic behavior of the precast specimens with the RFA content of 30% was almost the same as those with natural aggregate concrete (NAC). The increase in the axial compression ratio and aspect ratio led to higher peak loads of the precast shear walls. Finally, existing design methods of ordinary reinforced concrete shear walls were evaluated for their application to the design of precast RFA concrete shear walls with pressed sleeves. Overall, the evaluation results revealed that the examined design methods offer generally accurate strength predictions for the proposed shear walls.

Effect of partial replacement of aggregate with granulated polyethylene terephthalate (pet) on compressive strength of concrete

This paper is aimed at the development of appropriate combination of composite materials such as cement, aggregates and inclusion of Polyethylene Terephthalate (PET) in varying proportion in order to determine the optimal measure for the optimal strength. The study also, investigated the effect of PET aggregate on the compressive strength of concrete. Mix design targeting grade 25 concrete strength, using the Department of Environment (DOE) approach was adopted. Five different concrete samples were prepared accordingly, using natural aggregate as control mix and four others which consist of PET aggregate as partial replacement of fine aggregate at 5%, 10%, 15%, and 20% ratios respectively. The recycled fine aggregate (PET) was processed from bottle water waste, it was crushed, pressed and processed into finely material having river sand resemblance i.e., well distributed within sieve sizes of 0.075 and 2.00. The batching was done by weight. Cubes specimens were prepared, cured for 7, 14, and 28days and tested for compression. The results of the tests were analyzed statistically using regression method (Mintab) to establish optimal strength require mixture. The results and analysis established that there were reduction in compressive strength of the concrete containing PET aggregate and reduction rates increased with increase in the amount of PET inclusion in the concrete. The compressive strength values for 5%, 10%, 15% and 20% replacement of sand with PET at 28-day were 29.70N/mm2 , 25.95N/mm2 , 24.28N/mm2 and 23.23N/mm2 respectively. When compared with the control concrete specimens with an average value of 33.08N/mm2 gave 11.38%, 27.48%, 36.24% and 42.40% reduction in strength respectively. It was recommended that, though, the use of PET aggregate in the production of concrete does not have significant appreciable effect on the concrete strength, its use will protect the environment and as well help to conserve natural resources used as materials in production of concrete elements which currently undergo excessive depletion.

Producing Sustainable Roller Compacted Concrete by Using Fine Recycled Concrete Aggregate

One-third of the total waste generated in the world is construction and demolition waste. Reducing the life cycle of building materials includes increasing their recycling and reuse by using recycled aggregates. By preventing, the need to open new aggregate quarries and reducing the amount of construction waste dumped into landfills, the use of recycled concrete aggregate in drum compacted concrete protects the environment. Four samples of PRCC were prepared for testing (compressive strength, tensile strength, flexural strength, density, water absorption, porosity) as the reference mix and (10, 15, and 20%) of fine recycled concrete aggregate as a partial replacement for fine natural aggregate by volume. The mix is designed according to (ACI 327-15) with the specified cylinder compressive strength (28 MPa). The results showed a decrease in mechanical properties with an increase in partial replacement compared to the reference mixture and an increase in water absorption and porosity at 28 days. This is because old cement mortar on the surfaces of fine recycled concrete aggregates leads to higher porosity and water absorption than fine natural aggregates. At 90 days, results improved slightly. This is due to the non-aqueous cement in the recycled fine concrete aggregate.

Effect of binary and ternary blending of cement on properties of recycled aggregate concrete

Escalating the growth of industrialization and urbanization in the world demands the development of advanced infrastructure which in turn required a higher quality of raw materials. As cement is one of the major raw materials in concrete construction its demand for rising with the development of society. But the increased production of cement produces lots of environmental problems. So, there is a high requirement for a sustainable alternative of cement that have similar cementitious properties as cement. To address this problem experimental study is designed to use the binary blending of cement with rice husk ash (5%, 10%, 15% and 20%) as a replacement for cement. The study is further extended to analyse the effect of ternary blending of cement using further (5%, 10% and 15%) replacement of cement by sugarcane bagasse in optimum binary blended combination. Also, 25% of recycled fine aggregate is used in experiment as fine aggregate replacement throughout the mixes to achieve sustainability. Workability, compressive strength and flexural strength test were performed on concrete sample. The result of the study reveals that the workability of concrete mixes decreases with increases in the percentage of replacement both in binary and ternary mixes. In binary blending optimum strength is achieved at 15% replacement of cement with rice husk ash whereas in ternary blending 10% replacement by sugarcane bagasse ash with 15% rice hush ash was found optimum. Further, concrete shows 17.7% increase in compressive strength and 16% increase in flexural strength under the permissible value of workability. Study concluded that binary blending improve strength property and ternary blending further improve strength of concrete resulting in sustainability in construction.

Performance assessment of sustainable mortar mixes using recycled fine aggregate obtained from different processing techniques

Performance assessment of sustainable mortar mixes using recycled fine aggregate obtained from different processing techniques

Potential pozzolanic reactivity of recycled aggregates and waste powders as cement mortar component

ABSTRACT In this study, the use of recycled fine aggregates and waste powders in mortar was discussed, in which the pozzolanic reaction and the effect on strength properties of the resulting mortar were experimentally investigated. Test results showed that the compressive strengths of mortars with fine recycled brick and tile particles were lower than those of the control mortar at age of 7 days in the range of 72–92%, but reached 82–98% at age of 90 days, respectively. Because of the cement reduction, the mortars with waste powder cannot reach the strength level of the control mortar, and the strength of the mortars decreased with the increase in the cement replacement ratio. The strength efficiency of cement in mortar with the waste powders mortars increases with the increase of waste powder replacement ratio at later ages (56 and 90 days). This may be interpreted by the waste powders, being composed of major acidic oxides, could trigger the pozzolanic reaction to provide additional strength gains for mortar.