Natural Aggregates Research Articles

Unlocking the Secrets of Residential Construction: Investigating Aggregate Properties for Optimal Building Performance

The objective of this study was to find the strength of aggregates from selected three rivers and suggest to use aggregates for construction from the rivers, where better quality and strong aggregates exists. Aggregates from three selected rivers were tested for, size distribution, aggregate impact value (AIV), Los Angeles abrasion test (LAA). Natural and crushed aggregates were collected and tested for preparing the M20 grade concrete. The mean compressive strength of the concrete made from natural aggregates at 7 and 28 days was fond as 16.72 N/mm2, 16.5N/mm2 and 14.11N/mm2 and 26.22 N/mm2 , 24.29 N/ mm2 and 23.69 N/mm2 for Danda, Jharahi and Boulaha rivers respectively. Similarly, mean compressive strength of concrete made from crushed aggregates at 7 and 28 day was found to be 16.06 N/mm2 , 16.43N/mm2 and 15.16N/mm2 and 26.29 N/mm2, 24.95 N/mm2 and 24.36 N/mm2 for Danda Jharahi and Boulaha rivers, respectively. The null hypothesis (H0) was rejected and alternative hypothesis (H1) was accepted that there exist significant difference in mean value of compressive strength among the river aggregates from selected rivers. However no interaction among the river aggregates was found as Fcalc<Fcrit and Value was found > 0.05 hence null hypothesis was accepted. The higher strength aggregates were found in Danda river whereas lower strength aggregates were found in Boulaha river

Effects of cold-bonded artificial aggregate properties on the behaviour of concrete

The study investigates the use of artificial aggregates (AAs), specifically manufactured from ground granulated blast furnace slag (GGBFS) and ordinary Portland cement (OPC), to mitigate environmental harm caused by illegal quarrying due to the scarcity of natural aggregates (NAs). A cold-bonded pelletization technique was employed to produce five types of AAs with varying proportions of GGBFS & OPC as 82.5:17.5, 85:15, 87.5:12.5, 90:10, 95:5. The AAs with maximum OPC content exhibited a density of 1298 kg m−3, water absorption of 4.8%, and crushing and impact values of 28.6% and 26.3%, respectively. The impact of these AAs on concrete properties was assessed, revealing that AAs facilitated the production of workable concrete with low-density ranges between 1700–2337 kg m−3. Despite a decrease in concrete strength with higher AAs content, structural requirements were met, demonstrating AAs’ potential to effectively substitute natural coarse aggregates (NCAs). The concrete microstructure confirmed the formation of a strong interfacial transition zone (ITZ) and strength-developing cement-hydrated products. This research underscores the scientific contribution of AAs to address aggregate scarcity sustainably and recommends its application in structural elements by experimental validation.

Influence of Recycled Coarse Aggregate and Steel Fiber on the Workability and Strength of Self-Compacting Concrete

Abstract Waste materials pose a significant threat to both the environment and human health. On a global scale, the quantity of recyclable material is steadily growing, and its proper disposal is a significant focus of modern study. Concrete debris is a recyclable material that poses challenges for reutilization. Concrete waste refers to the fragments or remains of ready-mix concrete plants and the debris from destroyed structures, including historic buildings and those affected by earthquakes. The objective of this study is to reuse and utilize coarse aggregate formerly used in concrete constructions to create self-compacting concrete (SCC). The purpose is to assess the performance of this recycled aggregate in both its fresh and hardened states. Natural coarse aggregate (NCA) was switched out for recycled coarse aggregate (RCA) at 0, 50, and 100% volume ratios. In contrast, concrete was mixed with steel fibers (SF) at volume percentages of 0 and 0.44. Workability tests, including V-funnel, slump flow, and L-box tests, were conducted to assess the consistency of the mixes in their fresh condition. Additionally, the tensile and compressive strength of the concrete specimens were measured to evaluate their strength in the hardened state. Overall, the experimental findings showed that the fresh qualities of almost all SCC mixes fell within the required range, as outlined in the EFNARC standards. While the steel fiber harmed the fresh characteristics, it resulted in a proportionate enhancement in tensile strength. The findings indicated that including recycled aggregates into the concrete mixture enhanced its strength. The results showed that adding (0.44%) of steel fibers to concrete reduced the decline in compressive strength when the coarse aggregate was replaced entirely with recycled aggregate. In contrast, an equivalent proportion of fibers resulted in a significant improvement in tensile strength, rising from 26% to 54%, when using recycled coarse aggregate as the replacement of natural coarse aggregate. Thus, it can be concluded that using recycled aggregates and steel fibers in concrete production results in a higher quality product than regular concrete. Removing concrete waste has other benefits, such as enhanced financial return and preservation of the environment.

Slurry infiltrated low-quality construction and demolition coarse aggregate waste in concrete – a sustainable construction

Exponential growth in infrastructure projects, stimulated by emerging sophisticated technologies have been instrumental in the salutary proliferation of the construction sector, globally. An indubitable adversity of the rapid boom in the construction industry has been the rampant cumulative fallout of burgeoning waste during the demolition and construction phases of restoration. The current study explored the propriety of replacing natural coarse aggregate by low-quality recycled coarse aggregates (RCA) with varying proportions, along with silica fume (SF) and polypropylene (PP) fibers as admixtures, for the preparation of concrete. As the quality of RCA is determined by the history of its parent demolished structure, this investigation was preceded by assessment of the properties of RCA. A statistical approach using design of experiments, adopted to determine the coherent combinations of RCA and admixtures, yielded 16 combinations. Accordingly, concrete specimens were prepared with various quantities of RCA in place of natural coarse aggregate. Optimum proportions of the ingredients were inferred, based on the compressive strength attained by the concrete specimens. Further strength property evaluation was conducted, using these low-quality RCA treated with cement and silica fume slurry. Based on the strength results, 75% slurry infiltrated RCA, coupled with 10% SF and 0.5% PP, provided better strength in compression, tension and flexure. Scanning electron microscopy study, adopted for characterization of the micro-structural slurry-infiltrated RCA, shows the presence of strong interfacial transition zone in the treated RCA concrete. Thus, this study confirmed the efficacy of low-quality RCA as a promising material for structural construction, concurrent with a solution to various ecological disruptions precipitated by infrastructure construction and demolition wastes.

Synergistic effects of steel fiber and rubberized aggregates on concrete properties

The drive for more sustainable and environmentally friendly construction practices has resulted in revolutionary concrete production methods. One way is to include scrap rubber tires (contributing significantly to environmental pollution) into concrete mixtures to increase deformability. This study investigates the impact of surface-treated waste tire rubber (which partially replaces natural coarse aggregates with 5%, 10%, and 15% by weight) and industrial steel fiber (as reinforcement by including 0.5, 1, and 1.5% volume fractions) in concrete. Twelve concrete mixtures were prepared as test specimens. The replacement percentage was then determined using the compressive strength test results for additional surface treatment with three different alkaline solution (NaOH) concentrations (5%, 10%, and 15%) for 72 h. Thus, the hardened concrete properties were analyzed using compressive strength, flexural strength, and toughness; whereas the fresh qualities of equivalent concrete mixtures were evaluated using concrete slump. The findings revealed that, while partial replacement had a negative impact on the mechanical properties of the concrete, it was possible to produce rubberized concrete with better mechanical properties than conventional concrete when the partial replacement was less than 5%, treated with 10% alkaline solution, and reinforced with 1.5% steel fibers. The study’s findings illustrate the potential of these combinations for use in concrete pavement and slab applications.

Sustainable utilization of mine wastes in mortar production as a part of aggregates: a case study on calcareous wastes of Angoran lead and zinc mine.

This study investigated the feasibility of large-scale utilizing calcareous wastes (CW) of Angoran lead and zinc mine as aggregates in mortar production with the maximum possible substitution of natural aggregates. The main goal was to produce mortar (concrete with fine aggregates as fine as sand or smaller) from Angoran mine's calcareous wastes for maintenance in its underground spaces.Compared to concrete, suchmortars with better fluidity can enter narrow spacesmore easily.In addition,it can be usedto build various structures around the mine. Therefore, multiple samples were prepared by replacing 0% (as the control sample), 20%, 40%, 60%, 80%, and 100% of natural aggregates with CW. Subsequently, compressive strength, flexural strength, water absorption, slump, and TCLP tests were conducted on these samples. The results revealed that the mortar sample with 80% CW exhibited significantly higher compressive strength at 3, 14, 28, and 56days compared to both the control sample and other samples. Specifically, the compressive strength of this sample reached 35.5MPa at 56days, representing an 18.4% increase over the control sample. This indicates that the hydration of cement and the growth of C-S-H gel were enhanced. Analysis of the workability and slump of the samples indicated that as the percentage of natural aggregate replaced by CW increased, the fluidity of the mortar slightly decreased. In addition to mechanical properties like compressive strength, environmental aspects like heavy metal stabilization are also very important. So, TCLP tests conducted on the four heavy metals lead, zinc, copper, and cadmium demonstrated that the released amounts of these elements from all the samples were below the EPA standard limits. These findings confirm the effective stabilization of heavy metals in mortar samples. A comparison of SEM images revealed that the mortar sample made with 20% CW (with minimum compressive strength) exhibited a higher presence of ettringite compared to the sample made with 80% CW (with maximum compressive strength) after 28days.

Community Assistance in the utilization of Nickel Slag in the Morosi Village

Morosi Village located in Konawe Regency is one of the areas in which there is a nickel processing company. The nickel processing produces solid waste, one of which is nickel slag. The amount of nickel slag is accumulating day by day, because each process of refining one ton of nickel product produces 50 times the solid waste, equivalent to 50 tons. So that from the results of quite a lot of waste, research was carried out to use solid waste as a concrete forming material, either as coarse and fine aggregate, or as a cement mixture. Government Regulation No. 101 of 2014 classifies nickel slag as B3 waste hazard category 2 with waste code B403. This means that nickel slag is a waste that has a delayed effect, and has an indirect impact on humans and the environment. Meanwhile, at the end of 2019, the Indonesian National Standard (SNI) concerning the choice of nickel slag material from electric furnaces. This SNI was also prepared by the Ministry of Industry to support the development of nickel slag standards and as a solution for nickel slag management. The existence of SNI is also intended as a reference to optimize the use of nickel slag as aggregate, substitute for natural aggregate and other uses. Some examples of products made from nickel slag include bricks, precast and ready-to-print concrete, road base and field, soil improvers, growing media and fertilizers, mortar and cement slag, composite portland cement, and cement geopolymers. To accommodate the use of nickel slag, assistance is needed to the community, especially in Morosi Village to be able to process with appropriate, effective and efficient technology in accordance with its physical characteristics and chemical characteristics. This will be an alternative to reduce the amount of nickel slag that can pollute the environment, in addition to increasing people's income.

Investigation of the mechanical, microstructure, and durability properties of concrete with fine uniform and non-uniform polyethylene terephthalate (PET) aggregates

Concrete manufacturing is highly resource-intensive and is a major source of greenhouse gas emission. Accelerating depletion of natural resources such as sand, which is the primary material for aggregate in concrete manufacture is a growing problem. At the same time, the disposal of vast volumes of non-biodegradable plastic waste poses a global environmental challenge. The incorporation of aggregates derived from municipal plastic waste to substitute for sand has the potential to help address both issues, while at the same time mitigating greenhouse gas emission. This study examines the potential of municipal polyethylene terephthalate (PET) plastic waste as a fine aggregate in concrete manufacturing. The primary focus was on PET aggregates with non-uniform and uniform shapes ranging in size from 2.36 to 4.75 mm. In the concrete mixtures, 0 %, 30 %, and 50 % of the fine natural aggregate by volume were replaced with fine PET aggregate with a water to cement ratio of 0.40. The obtained results showed a reduction in compressive and splitting tensile strength when compared to control specimens. However, replacing 30 % of fine natural aggregate with PET (both uniform and non-uniform shapes) significantly improved chloride resistance by 13 % and 12 %, respectively, while also enhancing the bond between cement paste and PET particles. This study characterizes the material properties of PET concrete, which represents a promising method for reusing municipal plastic waste and mitigating environmental concerns in concrete production.

An Experimental Investigation of Light Weight Concrete Using Pumice Aggregate for Short Wall Panel Under the Application of Axial Load

The project study with the special concrete such as light weight concrete by using pumice aggregate (Natural aggregate). One of the disadvantages of conventional concrete is having high self weight. This heavy self-weight will make it to some extent an uneconomical structural material. Light weight concrete having low density reduces dead load and increase the thermal insulation. The reduction in density is produced by using it as a replacement of coarse aggregate partially in concrete. In this Study an attempt has been made to find the compressive strength of light weight aggregate concrete using mix M25 with poly carboxyl ether admixture under the application of axial load on short wall panel. Light weight concrete is made by replacement of Coarse Aggregate of Pumice aggregates.

Characterization of heat-processed artificial lightweight aggregates from polyethylene terephthalate plastic waste

Plastic waste is an undeniable source of pollution that threatens the existence of the earth’s flora and fauna. The bulk of plastic waste generated globally does not go through the proper methods of disposal but is carelessly discarded into the aquatic or terrestrial environment. Current recycling efforts are largely inadequate and disposal in landfills is still fraught with environmental and land use challenges. The proper disposal of plastic waste, as well as mitigating the environmental, social, and health impacts of extracting natural aggregates can be achieved by incorporating plastic waste as aggregates in the construction industry. This paper presents a characterization of aggregates manufactured from polyethylene terephthalate plastic waste using thermal/mechanical methods. From the cost analysis, 24,341.67 Ugx (6.09 USD) was spent to produce 1 kg of PET aggregates. Morphological, intrinsic and mechanical characteristics of the produced aggregates were established using standard procedures and equipment. The results of morphological characterization indicate an irregular shaped aggregate with smooth surface, a dense graded aggregate with a fineness modulus of 4.25, flakiness index of 26%, elongation index of 16% and particle index of 13. Intrinsic characterization yielded particle density of 1330 kg/m3, bulk density of coarse aggregates of 715 kg/m3 and water absorption of 0.445%. Mechanical characteristics of aggregates were evaluated, with compressive strength of 50Mpa, Aggregate Crushing Value of 37%, Ten Percent Fines Value of 71KN, Aggregate Impact Value of 24% and Aggregate Abrasion Value of 20%. The characteristics of PET aggregates confirm their suitability for application in structural lightweight concrete and rigid pavement. The produced PET aggregates can be considered in mix design as a total or partial replacement of natural aggregates in concrete.

Analysing the Influence of Recycled Concrete Aggregate and Expanded Perlite on Mortar Performance

With population growth and rapid urbanisation leading to excessive waste generation in the construction sector and the scarcity of natural resources, such as natural fine aggregates, the demand for recycled alternatives has increased. In exploring the potential of recycled materials for construction materials, the present study investigated the performance of recycled concrete aggregate (RCA) and expanded perlite in mortar as a partial replacement for fine aggregates. Different percentages of RCA and expanded perlite were used. A consistent percentage of perlite was used: 0%, 10%, 15%, 20%, 25%, 30% and 35%. The RCA and expanded perlite were then mixed with other materials such as cement, water and fine aggregate. Flowability, compressive strength and flexural strength tests were carried out. It was found that a 90% replacement of RCA for each increasing percentage of perlite in the mortar mix resulted in a significant reduction in flow diameter. The compressive and flexural strength of the mortar increased with age. However, the flexural strength of the control mortar, which contained neither RCA nor perlite, consistently exceeded that of the mortar with these additives. The results provide valuable insights for the production of new materials in the construction industry, for waste management and for lightweight yet durable construction solutions.

Assessing the Impact of Fly Ash and Recycled Concrete Aggregates on Fibre-Reinforced Self-Compacting Concrete Strength and Durability

Driven by the insatiable demand for construction materials, excessive quarrying for natural aggregates and the demand for raw materials for cement production pose significant environmental challenges, including habitat loss and resource depletion. To address these concerns, this study investigates the use of fibre-reinforced self-compacting concrete (FR-SCC) with high-volume fly ash (HVFA) and varying levels of recycled concrete aggregates (RCA) as substitutes for fine and coarse aggregates. This approach aims to simultaneously address environmental concerns by reducing reliance on virgin resources by utilizing the recycled aggregates and enhancing the performance of concrete through the combined benefits of fly ash and fibre reinforcement. In this study, Self-Compacting Concrete (SCC) mixes were created with 50% of fly ash replaced with conventional cement content, which was taken from the previous literature. Fine and coarse aggregate utilized in this investigation were replaced with processed recycled aggregates at varying levels from 0% to 100% at an interval of 25%, offering a promising solution to alleviate the environmental burden associated with excessive quarrying while contributing to sustainable construction practices. Additionally, replacement levels of aggregate synthetic polypropylene fibres (PF) were added into the concrete matrix up to 1% at an interval of 0.25%. This research contributes to the development of sustainable construction practices by promoting resource efficiency and minimizing environmental impact. The study found that SCC mixes with fibres and recycled aggregates maintained self-compactability, with polypropylene fibres and fly ash improving workability and cohesion. With this combination of materials, the highest strength value of 55.31 MPa was observed and the study promotes sustainable construction by reducing reliance on virgin resources and minimizing environmental impact.

Experimental study on impact performance of seawater sea-sand concrete with recycled aggregates

On islands distant from the mainland, obtaining raw materials for concrete production is often more challenging. To achieve sustainable development in island reef engineering, using discarded marine concrete and coral waste generated during island construction as recycled aggregates are of considerable significance. The preparation of Recycled Coral Aggregate Concrete (RCAC) for island reef engineering thus holds substantial importance. In this study, RCAC and Natural Aggregate Concrete (NAC), both designed with a compressive strength of C60, were prepared. Initially, the fundamental physical properties of the recycled coarse aggregate, such as apparent density, water absorption, and crushing index, were determined. Subsequently, a comparative analysis of the quasi-static mechanical properties of RCAC with varying proportions of recycled coral coarse aggregate (RCCA) was conducted. Furthermore, the impact compression mechanical properties of different RCAC specimens under various strain rates were examined using the Ф100mm Split Hopkinson Pressure Bar (SHPB) apparatus. The microstructure and long-term drying shrinkage performance of RCAC were also analyzed using Scanning Electron Microscopy (SEM) and a drying shrinkage apparatus. The finding indicated that the 28-day compressive strength of RCAC specimens with 100% coarse aggregate replacement reached a maximum of 62.4 MPa. The quasi-static compressive strength of RCAC specimens with 50% and 100% RCCA replacement was only 11.5% and 14.2% lower than that of NAC, respectively. Under impact loading, the dynamic compressive strength of RCAC specimens increased with the strain rate, with peak stress exhibiting an approximately linear relationship with the strain rate. The energy dissipation of RCAC specimens generally occurred in three stages, with the reflected and absorbed energies of the specimens increasing linearly with strain rate. At the same strain rate, the transmitted energy of RCAC specimens was higher than that of NAC specimens. Microstructural analysis revealed that the morphology of recycled coral aggregate is characterized by its porous and rough surface. The interfacial transition zone between the recycled coral aggregate and the cement mortar was relatively dense. Incorporating recycled coarse aggregate significantly affected the drying shrinkage properties of the concrete, with higher contents of RCCA leading to greater drying shrinkage rates.

Investigation of physical properties of microalgae‐pectin‐based bio‐composite with addition of pine needle for environmental application

AbstractPolymers and biopolymers have gained significance due to their applicability and use in industry reducing the negative impact of polymers based on petroleum. A possible solution for the conventional polymer's biodegradability is bio‐composites, which contain natural fibers or aggregates such as microalgae. Hence, microalgae biomass has a promising application to address the biodegradability issue of conventional polymers. In this study, Chlorella vulgaris biomass was mixed with pectin for control samples with glycerol as plasticizer. The mixture microalgae‐pectin‐glycerol, and the addition of pine needles was used to evaluate the tensile strength and compression of the bio‐composite. This bio‐composite showed a higher Young's modulus of 95.66 MPa for blend C2 and a higher strength with 20% of pectin concentration in the mixture. Additionally, the pine needle addition did not have a low effect between the compression results. On the other hand, analysis on elasticity showed that the full recovery of the bio‐composite happened after 10 min in all the blends. Also, the bio‐composite showed a slow release of nitrogen and phosphorous after 5 days of water addition, indicating an effective slow release for blend B for both nutrients. Water uptake capacity and loss of soluble material was studied using pullulan, chitosan, and cetyltrimethylammonium bromide additives. These cationic surfactants demonstrated their potential for reduction of water solubility of the bio‐composite.

Effects of Polyethylene Terephthalate Particle Size on the Performance of Engineered Cementitious Composites.

This study utilizes polyethylene terephthalate (PET) aggregate of different particle sizes (21 μm, 107 μm, and 244 μm) to replace natural aggregate in the preparation of PET-modified engineered cementitious composite (P-ECC). The impact of PET aggregate particle size on the performance of P-ECC is examined herein from micro to macro levels. The focus is on the influence patterns and mechanisms of P-ECC's workability, its basic mechanical properties, and its microstructure. Crack parameters are processed to quantitatively analyze crack development patterns. Using microscopic techniques, the interfacial transition zone (ITZ) between different aggregates and the cement matrix is compared, and the failure mechanism of P-ECC is analyzed. The results show that the incorporation of PET aggregate can improve P-ECC's workability and reduce its self-weight, but incorporation has a negative effect on compressive strength. Additionally, the particle size of PET aggregate significantly affects the uniaxial tensile performance of P-ECC. Compared to conventional ECC, the tensile strength of P-S (21 μm PET) increased the most markedly (18.1%), and the ultimate tensile strain of P-M (107 μm PET) increased the most markedly (66.0%), with both demonstrating good crack control and deformation energy dissipation capabilities. The uniaxial tensile performance of P-L (244 μm PET) was lower than that of the conventional ECC. Microscopic tests revealed that the increase in PET aggregate particle size enlarges the ITZ width and its surrounding pores. Appropriate pore enlargement is beneficial for enhancing tensile ductility, while excessive pores have a negative effect. The study results reveal the impact of PET aggregate particle size on the performance of P-ECC, providing new insights for the performance optimization of ECC.

Tension Lap Splices in Recycled-Aggregate Concrete Strengthened with Steel–Polyolefin Fibers

The bond strength of tension lap splices in recycled-coarse-aggregate-reinforced concrete strengthened with hybrid (steel–polyolefin) fibers was experimentally investigated. This study was conducted with the help of twelve lap-spliced beam specimens. The replacement level of coarse natural aggregates with recycled concrete aggregate (RCA) was 100%. The following variables were investigated: various ranges of steel–polyolefin fibers—100–0%, 75–25%, 50–50%, 25–75%, and 0–100%—in which the total volume fraction of fibers (Vf) remains constant at 1%; and two lengths of lap splices for rebars of 16 mm diameter (db): 10 db and 15 db. The test results showed that the best range of steel–polyolefin fibers that gave the highest bond strength was 50–50%. The ductility of the fiber-reinforced recycled-aggregate (FR-RA) concrete was significantly improved for all the cases of various relative ratios of steel and polyolefin fibers. The bond strength was also predicted using three empirical equations proposed by Orangun et al., Darwin et al., and Harajli. This study showed that the Harajli equation gave a more accurate estimation of the bond strength of reinforcing bars embedded in FR-RA concrete than those proposed by Orangun et al. and Darwin et al.

Multi response optimization of recycled aggregate based alkali-activated concrete using Taguchi-Grey Relational Analysis Method

The use of cement in construction causes large amounts of CO2 emissions into the atmosphere. Moreover, the use of large amounts of natural coarse aggregate causes environmental damage, and the availability of such natural aggregate is also depleting. The present experimental study explores and optimizes the impact of various parameters on the fresh, mechanical, and durability properties of recycled waste concrete coarse aggregate (RWCA)-based geopolymer concrete (GPC) in combination with ground-granulated blast furnace slag (GGBFS) and fly ash (FA) using the Taguchi-Grey Relational Analysis Method (TGRAM). The coarse aggregates in GPC were fully replaced with RWCA produced by crushing waste concrete. The effects of FA inclusion (%), Na2SiO3/NaOH ratio (SS/SH), molarity of NaOH (SH), dosages of superplasticizer (%), and alkaline solution to binder (Al/Bi) ratio are investigated under ambient curing conditions. The obtained maximum compressive strength and split tensile strength along with minimum water absorption of GPC at 28 days were 67.90 MPa, 3.85 MPa and 2.92 % respectively. The microstructural studies of GPC having low, high, and optimal strength are carried out using XRD, FE-SEM, and EDAX analysis. These studies confirmed the presence of calcium-based hydration products such as CSH and N(C)ASH, which makes the matrix of optimized GPC more compact.

Eco-friendly concrete: Combining treated wastewater and recycled aggregates.

The concrete industry is a significant consumer of drinking water and natural aggregates, such as sand and gravel. However, the scarcity of water and aggregate resources and the challenges associated with the disposal of construction and demolition waste prompted the exploration of alternative materials. This study investigates the feasibility of incorporating secondary treated wastewater from UASB reactors followed by trickling filters and mixed recycled aggregates as potential alternatives. To assess the viability of these alternatives, the study considered the replacement of 100% potable water with treated wastewater, as well as varying proportions of recycled gravel (20, 40, 60, 80, and 100%) and recycled sand (10, 20, 30, 40, and 100%). Physical and mechanical properties were negatively affected, but it was possible to reach compressive results over 40 MPa and splitting tensile strength over 4 MPa for almost all mixes. Regarding physical properties, the use of alternative materials caused poorer outcomes for density, water absorption, and air-void ratio. The limited magnitude of these detrimental effects indicates the potential of manufacturing concrete with the addition of combined treated wastewater and recycled aggregate as a viable strategy while enhancing reuse practices.

Assessment of the durability of cement-bound granular mixtures using reclaimed concrete aggregate and coconut fiber

In transport infrastructures, the cement-bound granular mixtures (CBGM) for base and sub-base of pavement layers can be built using mostly recycled materials. Recycled aggregates (RA) can replace the natural aggregates (NA) and coconut fiber (CF), obtained from discarded coconut husk, can be introduced to promote a reinforcement effect. Currently, the use of CF in CBGM is new, and regarding the use of RA in CBGM, the literature about its durability is still limited. Thus, there is a gap in knowledge regarding the durability of these solutions.Building on previous validation of mechanical performance, this work is among the first to evaluate the durability of CBGM incorporating RA and CF. For a comprehensive evaluation, three test methods were selected: wetting-and-drying, freezing-and-thawing, and a strength ratio using the indirect tensile strength test. The results highlight the feasibility of RA to replace NA, as both led to similar CBGM durability levels. The introduction of CF promoted gains in durability (on average reducing the mass loss by 42 % in the wetting-and-drying tests and by 20 % in the freezing-and-thawing tests), enhanced toughness, and allowed for a better response of the CBGM in the post-cracking phase.

Comparative assessment of recycled concrete and recycled asphalt aggregate in pervious concrete: emphasis on strength and life cycle assessment

ABSTRACT Pavements create an impermeable layer, contributing to a decrease in groundwater recharge and a rise in flood frequency in urban areas. Pervious concrete pavement (PCP) is considered one of the solutions to address the problems associated with impermeability. Due to the low-strength applications of PCP and to address the environmental issues associated with recycled concrete aggregate (RCA) and recycled asphalt pavement (RAP), studies have used them as replacements for natural aggregate (NA). Past studies recommended the optimum RCA or RAP content based on mechanical and durability investigations. This study investigates strength and environmental aspects of using RCA and RAP in PC by replacing NA with RCA and RAP at 30, 60, and 90% by volume. The compressive strength of RCA-PC mixtures at 7 days was found to be higher than that of RAP-PC mixtures, while RAP-PC mixtures displayed better abrasion resistance. Total embodied energy (TEE) and greenhouse gas emissions (GHG) with 90% replacement of RCA and RAP were 6.5–7.5% and 12.5–13.42% lower than control mixtures for different transportation distances, respectively. The cost-per-strength ratio indicated that RCA-PC mixtures were more preferred than RAP-PC mixtures. Overall, the study recommends 30% RCA/RAP content in PC, considering strength, cost, and environmental aspects.