Crushed Concrete Waste Research Articles

Preparation and Properties of Natural Bamboo Fiber-Reinforced Recycled Aggregate Concrete.

To promote resource reuse and the green, low-carbon transformation of the construction industry, this study uses recycled aggregate from crushed waste concrete and natural bamboo fibers to formulate bamboo fiber-reinforced recycled-aggregate concrete. This study investigates the effects of natural bamboo fiber (NBF) content, NBF length, and the water-to-cement ratio on the performance of concrete through an orthogonal experiment to determine the optimal mixing proportions of NBF-reinforced concrete. Additionally, recycled aggregate completely replaced natural aggregate. The mechanism by which NBF influences concrete was also analyzed. The results demonstrate that the NBF-reinforced specimens exhibited good integrity during compression failure, with NBFs effectively tying the concrete together. The optimized parameters for NBF-reinforced concrete were an NBF length of 20 mm, an NBF content of 0.4v%, and a water-to-cement ratio of 0.55. Almost no flaky Ca(OH)2 crystals were observed in the NBF-hardened cement-paste transition zone, indicating effective bonding at the interface.

FEATURES OF USING CRUSHED CONCRETE AS A COARSE AGGREGATE FOR CONCRETE

Problem statement. According to the results of a study by the Kyiv School of Economics as of June 2023 the total amount of direct documented damage to residential and non-residential infrastructure due to destruction and damage as a result of military actions exceeded $150.5 billion. During the post-war reconstruction Ukraine will face the problem of a large number of buildings and structures that will be subject to partial dismantling and demolition. This process will be accompanied by the generation of a significant amount of construction waste, which traditionally in Ukraine is taken to landfills without recycling. On the other hand, there will be a need for a large quantity of construction materials, the share of which in the construction cost may reach 50 %. To reduce the cost of objects, it is advisable to reuse materials from waste generated after dismantling. Such materials are called recycling. The most obvious option is the use of crushed concrete waste as a coarse aggregate for the production of new concrete. The purpose of the article. Identification of the features of recycled coarse aggregates from concrete waste and concrete with their use, determination of the influence of source concrete on the properties of recycled aggregates. Conclusions. The mesoscopic model of concrete with recycled coarse aggregate has been examined. The analysis of the current research results on both recycled concrete aggregates and concrete with their use showed that, in general, with correct calculations of concrete mix compositions that consider the actual physical and mechanical properties of recycled aggregates, the production of structural concrete is possible. At the same time, crushing methods and the grain composition of such aggregates have a significant influence. In order to standardize the approaches to the research of recycled aggregates, it is necessary to create an appropriate methodology or regulatory framework.

PARTICLE-SIZE DISTRIBUTION ASSESSMENT OF THE RECYCLED AGGREGATES FROM CONCRETE REMAINS

The reuse of the remainders of destroyed concrete structures is becoming more and more urgent problem not only in Ukraine, but also in the whole world. According to the current strategy of secondary use of resources, concrete waste is either crushed into recycled aggregate as a substitute for natural aggregate or crushed into recycled powder as a substitute for cement in mortar and concrete. The reuse of construction waste as secondary construction materials can reduce the need for natural resources for construction and free areas from accumulated construction debris. The purpose of the work is to evaluate the particle size composition of aggregates obtained from recycled concrete of waste reinforced concrete railway sleepers. To achieve the goal, the following tasks were set: to grind of sleeper waste in various ways; to determine the granulometric composition of coarse and fine aggregates; compare the obtained data with the standard requirements for concrete aggregates. Destroyed reinforced concrete railway sleepers were used as material for research. After removing the reinforcement, the sleeper parts were first loaded into a jaw crusher with a fixed distance between the working plates at 20 mm. The obtained material was reloaded into a drum mill and grinded for 30 minutes. After that, the mixture was unloaded on a standard set of sieves to determine the particle size distribution. As a result of an experimental study of crushed waste of reinforced concrete sleepers, the following was established. The granulometric composition of particles larger than 5 mm meet the requirements for coarse aggregates to produce concrete mixtures. Fractions with particle sizes less than 5 mm are very fine with a fineness modulus at 0.9 which does not meet the requirements for fine aggregates to produce concrete mixtures. Further research will be aimed at studying other properties that determine the possibility of using aggregates for reuse in concrete mixes, namely moisture content, average density, compressive strength, etc. Also, the ways for usage of fine fractions as fillers will be search for other building materials in order to dispose of crushed concrete waste.

Durability characteristics of recycled high performance concretes under an aggressive environment (sea water)

With the increase of solid construction waste (CSW) due to the acceleration of urbanization in Algeria, many ecological and environmental issues have been raised. Recycling and reuse of construction waste helps to reduce pollution, carbon emissions and preserve resources. Few studies have focused on the durability characteristics of concretes based on fine aggregates recycled from brick and concrete waste. The main purpose of this study is to formulate and analyze the performance of HPC based on waste brick and concrete fines. The substitution of alluvial sand with brick fines, causes the reduction of the heat of hydration and delays the appearance of the thermal flux peaks. while HPC rich in crushed concrete waste increases the heat of hydration. The appearance of heat flux peaks coincides for all mixtures with fines of waste concrete substitution and they will be delayed and prolonged for HPC with sand based on waste brick.

EXPLORING CRUSHED CONCRETE WASTE AS RECYCLED FINE AGGREGATE IN CONCRETE PRODUCTION

Concrete waste is generally a challenge that is left to accumulate in illegal dumping areas and landfills. This research focused on how structural concrete waste could be crushed and used as recycled fine aggregate in the production of concrete. Experiments were carried out to establish the performance of this 0.6 water-cement ratio concrete containing partially recycled fine aggregate. Concrete fluidity and compressive strength tests were carried out at 7 days and 28 days only because the study was exploratory in nature. Results indicated that replacement of 20% natural fine aggregate with recycled fine aggregate resulted in the increase of concrete compressive strength by 8% from 28 MPa to 30 MPa at 28 days. 40% replacement of natural fine aggregate resulted in a drop of compressive strength by 11% yet retaining compressive strength at 25 MPa. 20% and 40% replacement of natural aggregate resulted in the concrete fluidity reduction of 5% and 17%, respectively. The average theoretical density was 2538 kg/m3. The study concluded that normal grade structural concrete can be attained using crushed concrete waste resulting in taking out the concrete waste from landfills and illegal dumping sites. These results established an environmentally friendly mode of handling concrete waste sustainably. Further, this solution would result in slowing down the depletion of natural fine aggregate bodies.

Durability Characteristics of Recycled Aggregates for Physical and Chemical Properties of Concrete

In structural concrete, it becomes essential to perform the comprehensive research work for recycled aggregates (RA) in order to check their material properties as well as assess the influence the second-generation concrete quality. This work has the objective to assess and suggest the technical standards to check the performance and behaviour of concrete as compressive strength developed from recycled aggregates. The demolished crushed waste concrete can provide the RAs. Such aggregates are heterogeneous in composition from a quality point of view as being resultant from diverse adhered mortar and materials. Such properties of RAs must be assessed, as these are utilized in concrete; consequently make an effort to further investigate the RAs characteristics that are needed to be implemented in concrete mixes. This paper presents the characteristics of RAs as physical and chemical properties with further examination on the concrete properties prepared with RAs. It also presents the comprehensive strength to show the durability properties in order to set the standard guidelines. The developed nations such as Japan have even laid down standards for RA usage in concrete. Thus, it becomes essential to make guidelines for the material utilization in construction, especially to match with the local Indian conditions.

Sustainable soil stabilization: the use of waste materials to improve the engineering properties of soft soils

One of the biggest challenges of recent civil engineering is the need to make it sustainable by implementing environmentally friendly and cost-effective solutions. The search for new materials and technologies is an important and current issue also in the strengthening of soft soils. In the soft soil stabilization process, conventional materials (cement and lime) are being replaced by waste materials, such as stone slurry waste, spent coffee grounds, rice husk ash, crushed waste concrete and glass, natural fibers, sawdust, waste tire rubber and plastic waste materials. Appropriate waste admixture content contributes to soil reinforcement by reducing compressibility and increasing maximum density and shear strength. The application of waste as an admixture is an economically and ecologically beneficial method of soil improvement. It eliminates the cost of materials and helps to reduce the problem of waste disposal, which is sometimes very expensive and problematic. The study aims to analyze the effect of waste materials on improving the physical and mechanical properties of soils based on the research results presented in the literature.

Recycling of Construction Waste Concrete as a Stabilizer for Gypseous Soils

This study presents the possibility of recycling Crushed Waste Concrete resulting from the demolition of buildings, and making practical use of these abundantly available materials, by grinding them and adding them in different proportions to gypseous soils to increase their maximum bearing capacity and reduce compressibility. A laboratory model with dimensions (300*300 *600mm) of galvanized steel, 4 mm thick, was used to study the effect of mixing (0%, 2%, 4%, 6%, and 8%) Crushed Waste Concrete with three types of water-flooded natural gypseous soils with different percentages of gypsum (30%, 46%, and 66%). Loading tests were carried on square steel footing (70*70mm) and 9mm thick, placed on these soils. More than 15 tests were conducted on the laboratory model, in addition to the usual classification tests on the soils used in the study. All tests were carried after submerging gypseous soils due 24 hours. The study showed a clear improvement in the susceptibility of the three gypseous soils using all the addition percentages of concrete powder, the best percentage was 8%, while the improvement rates were less using 2%, 4%, and 6%. As the bearing capacity of the soil increased after mixing it with this ratio due to filling the voids formed as a result of melting gypsum during the water immersion process, which compensated for it at this stage. Mixing gypseous soil with crushed waste concrete by 8% increases ultimate bearing stress about 8 times, while it is 2.5 times for model mixed with 2% of this additive, compared with the untreated one.

Insights on the Corrosion Resistance of Reinforced Recycled Aggregate Concrete

Recycled aggregate produced from crushed waste concrete is suitable for use in structural concrete. It reduces the demand for non-renewable resources and also for energy in general. However, RA is more porous than most natural aggregates. The porosity of the concrete cover defines the corrosion resistance of reinforced concrete, and it is therefore disputed how the use of recycled aggregate may affect the durability of reinforced concrete. This paper describes the corrosion-related performance of reinforced concrete with recycled aggregates in the initiation stage (determined by the carbonation and chloride ingress) and propagation stage (determined by the electrical resistivity and cracking) of corrosion. The aspects of interest are not only the porosity of RA but also its effects on the chloride binding, carbonation, electrochemical properties and corrosion cracking development.

In situ disposal of crushed concrete waste as void fill material at UK nuclear sites: Leaching behavior and effect of pH on trace element release

The leaching behavior of stockpiled crushed concrete waste is important in determining its suitability for in situ disposal at UK nuclear sites. Sand sized particles from surface (0–0.1 m) and subsurface (2.5–2.7 m) samples were composed of silica and calcite grains in a matrix of calcium alumina-silicate hydrate (C-(A)-S-H) with Ca/Si ratios of 0.5 ±0.3 and 0.9 ±0.3 respectively. Calcite content was also higher in surface samples indicating a greater degree of weathering and carbonation. This resulted in lower leachate pH for the surface samples (pH 8–9.6) compared to subsurface samples (pH 10–11.3). The waste displayed a high acid buffering capacity but low alkaline buffering capacity. Element release as a function of pH was similar for surface and sub-surface samples and between different size fractions. Leaching of contaminant metals was close to minimum values at the pH values produced by the crushed concrete but increased by several orders of magnitude at pH <5 (for Al, Pb, Cr and V) and pH >12 (for Al and Pb). Weathering and carbonation during long-term stockpiling, therefore, has a positive impact by producing a waste with stable pH and low metal leaching potential suitable for in-situ disposal as a void fill material.

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.

Developing carbon-neutral construction materials using wastes as carbon sink

Developing ecofriendly and low-carbon construction materials is essential to meet the ambitious target of global net zero emission by 2050. The concept of using wastes as carbon sink is taking advantage of alkaline solid wastes, which are rich in calcium or magnesium as a medium for absorbing carbon dioxide (CO2), and allowing manufacturing thermodynamically stable carbonate minerals for construction applications. Today, the major practical and successful applications of CO2 in the construction industry are through accelerated carbonation of granulated aggregates and precast concrete blocks manufactured with different proportions of calcium-rich waste materials. CO2 is also used as an activator in speciality nonhydraulic carbonate-binders or directly injected (in a liquid form) into fresh ready-mix concrete to produce a construction material with higher strength and lower carbon footprint. In addition, accelerated carbonation has become a promising approach to improve the quality of crushed concrete waste, and can be reused in new concrete to attain a sustainable concrete life cycle. In this paper, the progress in academic research of using CO2 in wastes and cement-based products as well as the key advantages and limitations related to the large scale application in the construction industry have been discussed in detail.

Improvement of Soft Clay Soil Using Different Types of Additives

This study deals with the evaluation of the stabilization of several samples of soft soil with some chemical and physical additives. The intention is to amend the weak properties of these soils summarized in low bearing capacity and high settlement. The used stabilizers are quicklime, class F fly ash activated by cement, rock powder, crushed waste concrete, and tire crumb rubber. The paper investigated the effects of these stabilizers by unconfined compression test that considers very effective geotechnical test for measuring the ability of soils to bear structures constructed on them especially when used additives. This test was carried out on three samples of soils. They were classified by (UCSC) as (CL) soft soils. They were also classified by (AASHTO) as (A-7-6), (A-6), and (A-6) are rated as fair to poor subgrades in (AASHTO). The results of (UCS) test for each of the five additives used were compared according to the responding of each soil samples used. The (UCS) test was conducted in this study on sixty samples of soils before and after treatment and under the basics of the Proctor compaction test at optimum moisture content and maximum dry density. The results showed that the rock powder was the most suitable stabilizer that gave best results of improvement reached to 900% at 25% percent by dry weight of soil, crushed waste concrete came after it that gave treatment 683% at 15%, class F fly ash activated by cement followed the two formers which increased strength 533% at 15%, quicklime after that in an amendment 517% at 9% and finally tire crumb rubber that stabilized the soil 500% at 4%. In the literature, these materials founded to be very efficient in the stabilization of soils in their physical and chemical properties like increasing bearing capacity and reducing settlement of soil.

Hydraulic conductivity and undrained shear strength of clay-construction and demolition solid waste materials mixtures

The study aims to investigate the effects of three different construction and demolition materials (CDMs), including crushed waste asphalt (CWA), crushed waste bricks (CWB), and crushed waste concrete (CWC), on some geotechnical properties of low plastic clayey soil, particularly, the undrained shear strength (Su) and the hydraulic conductivity (k). A set of experimental tests were performed on clayey soil and on clayey soil-CDM mixtures at mixing ratios of 5%, 10%, 15%, and 20% by dry weight. The results show that the soil plasticity decreases as the CDMs increase. Quantitatively, it is found a maximum of 12%, 6%, and 6% decrease in the liquid limits (LL) and a maximum of 9%, 4%, and 6% decrease in the plasticity limit (PI) of the mixtures with 20% of CWA, CWB, and CWC, respectively. The results of the Su estimated empirically from the fall cone tests show that the Su decreases as the CDMs increase. The Su reduces by approximately 10% and 2% of the mixtures with 20% CWA and CWB, respectively. But the Su is not affected by the CWC additive for water content lower than approximately 35%. The k value increases as the CDMs increase. The results show that the reported k value increases by 75%, 79%, and 247% of the mixtures with 20% of CWA, CWB, and CWC, respectively. Additionally, the k values obtained from the consolidation test confirm the findings of the effect of the CDMs on the coefficient of hydraulic conductivity.

Improving California Bearing Ratio (CBR) Using Chemical and Physical Treatments for Diyala Soils

Gets in the world at this time continued growth and rapid development in the whole aspects of life. The urgent needing accomplished that is in civil engineering demands like the construction of houses, schools, hospitals, roads, and other structures. Because of that and for economic and security reasons; classifying soil and knowing its bearing capacity appeared to be very necessary conditions that offer a large domain of benefits that could not be counted. This study focused on classifying and determining the bearing capacity of some samples of soil that classified as soft soils of Baquba city the center of Diyala governorate in Iraq. Then trying to increase their bearing capacity. The California Bearing Ratio (CBR) was used in the paper to define soil strength because it is considered a force measuring parameter. Five elected physical and chemical treatments were used in predetermined percents taken from the literature and suited the kind of soil. They were quicklime, class F fly ash activated by cement, rock powder, crushed waste concrete, and crumb rubber of tires. The treatment that was the best among the five used methods was by the rock powder that improved CBR value by 570% in soil samples A used

Compressive and Flexural Strength Property Enhancement for Fibre Reinforced M30, M50 and M80 Grade Concrete Using Foundry Sand (FS) and Crushed Concrete Waste (CCW)

Now days, many research works are carried for all grades of concrete to make the concrete most economical and durable there by adding the supplementary cementitious materials and alternative replacement aggregates. In this research work deals with the experimental investigation of mechanical properties of the M30, M50 and M80 grade concrete by replacing the fine and coarse aggregate by foundry sand and crushed concrete waste respectively. Mix design procedures were followed as per IRC44:2017 guidelines and recommendation. Proper dosage of super plasticizer (SP) was maintained in the concrete to make it better performed. In this present investigation, a Poly Propylene fibre (PPF) of 0.3% by weight of the cement is used. Mechanical properties such as Compressive strength and Flexural Strength were determined by preparing the respective mould sizes for specific test and are cured for 7, 14 and 28 days and result obtained for respective days were tabulated and discussed.

Shear strength of 50 MPa longitudinally reinforced concrete beams made with coarse aggregates from low strength recycled waste concrete

Crushed waste concrete is a viable source of recycled coarse aggregates (RCA) to produce concrete. The RCA generally has less favorable properties relative to natural coarse aggregates (NCA), which can affect the shear strength of the concrete. This paper reports the results of an experimental study of the shear behavior of seven shallow longitudinally reinforced beams containing seven ercentages of replacement (PR) of NCA with RCA ranging from 0 to 100%. The target cylinder compressive strength (fcyl) of the concrete was 50 MPa and the longitudinal reinforcement ratio (ρL) was about 1%. The results indicate that all the beams failed in shear. The use of RCA did not change their mode of failure and did not directly affect the characteristics of the critical diagonal failure cracks. In addition, it was found that, on average, the recycled aggregate concrete (RAC) beams had a normalized shear strength that was 12% higher than that of the natural aggregates concrete (NAC) control beam. The difference in strength amongst the RAC beams with various PR was also limited. It is to be noted that the literature reports numerous cases where the RAC beams resisted higher strengths than their NAC control beams. Finally, the observed ultimate strengths of the beams were compared to the shear strength calculations of the ACI, CSA, EC2, and MC2010 codes and the Modified Compression Field Theory (MCFT). The calculated strengths were found to be conservative for the RAC beams.

In Situ Disposal of Crushed Concrete Waste as Void Fill Material at UK Nuclear Sites: Leaching Behaviour and Effect of Ph on Trace Element Release

In Situ Disposal of Crushed Concrete Waste as Void Fill Material at UK Nuclear Sites: Leaching Behaviour and Effect of Ph on Trace Element Release

EFFECT OF REPLACING CRUSHED STONE IN STONE COLUMNS BY WASTE MATERIAL ON SOIL IMPROVEMENT RATIO

Many researchers’ studies have shown that stone column is the best material to use to improve the bearing capacity of clayey soils. There are millions of waste volumes resulting from daily human activities. This excess waste leads to disposal problems and also causes environmental contamination and health risks. Demolished concrete is such one waste material that is produced from building demolition in Baghdad, Iraq. This paper describes experimental work conducted at the University of Technology that was carried out to investigate the improved bearing capacity of soft clay using crushed stone, followed by replacing crushed stone with concrete waste with the same relative density and grain size. The replacement was carried using waste concrete with different percentages corresponding to 25%, 50%, 75%, and 100%. The main conclusion drawn is that the bearing capacity increased to 119% by using crushed stone column, while the bearing capacity increased to 155% by using 100% of crushed concrete waste.

Properties of Papercrete Concrete Containing Crushed Concrete Waste As Coarse Aggregate

Researches on the effect of waste recycling in the concrete industry are increasing due to its low cost as well as considering it as a significant method for protecting the environment by minimizing solid waste. This research evaluates the possibility of using concrete waste as partial replacement with coarse aggregate in Papercrete, and its effect on some concrete properties which include compressive strength, splitting tensile strength and heating resistance. Wasted paper used in this study as an additional material with three various ratios (5%, 10% and 15% by weight of cement) was mixed with concrete which have 0, 10%, 20% and 30% of concrete waste as a partial replacement of the coarse aggregate to produce twelve concrete mixtures. As compared with the plain mixture, it was found that workability decreasing with the increasing of both wasted paper and wasted concrete content. The study illustrated that the optimum percentage of adding wasted paper and wasted concrete replacement are 5% and 10% respectively, due to increasing in both compressive and tensile strength by 11.99% and 13.54% respectively compared with the plain mix. The residual strength of concrete after heat exposure was affected significantly by the increasing of wasted paper content.