Recycled Rubber Aggregate Research Articles

Water Resistance Analysis of New Lightweight Gypsum-Based Composites Incorporating Municipal Solid Waste

Incorporating waste to produce new environmentally friendly construction products has become one of the great challenges of the industry nowadays. The aim of this research is to analyse the behaviour of novel gypsum composites against water action, incorporating recycled rubber aggregates (up to 8.5% vol.) and dissolved expanded polystyrene (up to 10.0% vol.). To this end, a total of 10 dosages have been proposed with the progressive substitution of natural resources by these secondary raw materials. The results show how it is possible to reduce the total water absorption of the gypsum composites by up to 8.3% compared to traditional gypsum material. In addition, it is also possible to reduce water absorption by capillary by up to 52.7%, resulting in lighter composites with good performance against water action. In all composites analysed, the mechanical strengths exceeded the minimum values of 1 MPa in bending and 2 MPa in compression, making them an optimal solution for the development of lightweight prefabricated products for damp rooms.

Mechanical properties investigation on recycled rubber desert sand concrete

The mechanical properties of recycled rubber desert sand concrete were studied to determine the effect of the replacement rate of recycled rubber and desert sand. The replacement rates of recycled rubber aggregates were set to 0 %, 5 %, 10 %, and 15 %, respectively, and for dessert sand aggregates were set to 0 %, 10 %, 20 %, and 30 %, respectively, during concrete preparation. The concrete's compressive, tensile, and freeze-thaw mechanical properties were tested at each replacement rate. The experimental results show that when the replacement rate of desert sand increases from 0 % to 30 %, the replacement rate of recycled rubber is 15 %, and the splitting tensile strength of concrete shows a pattern of first increasing and then decreasing. When the replacement rate for desert sand is 30 %, the replacement rate for recycled rubber rises from 0 % to 15 %, and the splitting tensile strength shows a pattern of first decreasing. With replacement rates of 10 percent for recycled rubber aggregate and 20 percent for desert sand aggregate, the damage to the concrete from external forces is relatively ideal. The compressive strength values are the highest, and the split tensile strength is the best, demonstrating good compressive and tensile strength. The results of CO2 emission analysis show that as the amount of recycled rubber increases, the CO2 emissions per unit volume of concrete also increase. The interface of the micro-optical structure in the concrete is straightforward, the pores are few, and it exhibits good mechanical properties. The concrete undergoes freeze-thaw cycles with relatively stable changes in compressive strength and split tensile strength, demonstrating a solid freeze-thaw resistive mechanical property.

Enhancing the interfacial properties of recycled rubber aggregate mortars through surface modifications with graphene oxide coating

This study explores the potential application of waste rubber (WR) as sustainable recycled rubber aggregates (RRA) in the construction sector. A layer of graphene oxide (GO) was coated on RRA through multiple surface modification techniques, aiming to enhance the interfacial properties in RRA mortars. The C-S-H phases were first tailored through chemical synthesis to better understand the nucleation and growth of hydration products with the presence of GO. Subsequently, a 180 ± 10 nm-thick GO coating was attached to the RRA surface through surface treatment with sodium hydroxide solution, silane coupling agent, and GO suspension. In addition, the mechanical strength, damping performance, water absorption, chloride resistance, and microstructural properties of cement mortars prepared with RRA were further assessed. It was found that the GO coating significantly improves the bonding between RRA and the cementitious matrix due to its hydrophilicity and nucleation effects, which locally facilitate the cement hydration at interfaces. The cement mortars produced with surface-modified RRA exhibit promising high-damping characteristics, accompanied by improved durability and mechanical performance over those prepared with untreated RRA.

Development and characterization of new lightweight waste-based plaster composites for building applications

The development of new environmentally friendly construction materials that incorporate waste as an alternative to traditional raw materials is becoming increasingly important and necessary for the construction sector. Gypsum plasters composites are characterised by their versatility and wide range of applications in precast construction due to their excellent technical performance and low cost. This research presents a new material that incorporates EPS waste in solution and recycled rubber aggregates as secondary raw materials, partially replacing traditional plaster material. In this way, partial mass substitutions of up to 12.5 % have been achieved compared to the reference composites without additions. The results show how the incorporation of EPS in solution allows a more homogeneous integration of the residue in the plaster composite matrix. Although it is true that the incorporation of both residues has slightly reduced mechanical resistance to bending and compression, reaching minimum values of 3.71 MPa and 5.08 MPa respectively, the results obtained greatly exceed the minimum values required by current regulations. On the other hand, in the study conducted with prefabricated false ceiling plates, it has been observed that the combined effect of both residues allows for greater resistance to simple bending than traditional composites, with a reduction in bulk density and thermal conductivity of up to 30.1 % and 26.5 %, respectively. Thus, this work presents a viable alternative for the development of new plaster composites that are more sustainable, lightweight and conducive to advancing towards the industrialisation of the construction sector.

Compressive behavior of sustainable rubberized concrete‐filled steel tube columns having various recycled tire rubber aggregate contents and developing a predictive design model

AbstractAs a sustainable solution, employing recycled tire rubber aggregates in the production of concrete is of considerable interest. However, the applicability of rubberized concretes in construction is restricted due to their relatively low mechanical performance. Using rubberized concrete as a filling material in a steel tube provides a suitable solution for overcoming this issue and for using it effectively as a load‐bearing element. The objective of this study is to examine the impact of the material characteristics of the sustainable rubberized concrete‐filled steel tube (Ru‐CFST) and develop a design model based on ultimate strength prediction for the axially loaded Ru‐CFST stub columns with varying contents of tire rubber aggregate. The model was developed through the gene expression programming (GEP) technique by employing the experimental test results to determine the ultimate compressive strength of Ru‐CFST columns. Based on the principal component analysis, the sectional properties of the load‐bearing element (such as outer diameter, thickness, and length), material strengths (such as rubberized concrete and steel tube strengths), and rubber content were determined as statistically significant parameters affecting the ultimate axial strength of Ru‐CFST stub columns and thus, they were considered in the stage of the model generation. Furthermore, the proposed model's performance was compared to that of available models suggested for traditional CFST columns by commonly employed design codes, namely, ACI, AIJ, AISC, CSA, EC4, and GB. Based on the statistical analysis of the results, it can be concluded that the existing formulations have a relatively acceptable randomness and scatter of observations within the distribution, while the proposed design model gives a more accurate prediction for the ultimate bearing capacity of axially loaded Ru‐CFST columns with the highest R‐squared value of about 0.99 and the comparatively lowest mean absolute percent error of 7.54. It can be stated that the proposed GEP‐based design model will encourage engineers to use such sustainable structural members in their designs and constructions.

Investigation of Materials for Enhanced Vibrational Insulation in Ground Structures Using Concrete Mixtures: A Case Study of Rubber Aggregate Addition.

The reduction of vibrations in concrete has been a topic of discussion among scientists. This article presents research on designing concrete mixes for constructing ground barriers with enhanced vibration isolation using waste materials. This study discusses the design of concrete mixes for the construction of concrete partitions with increased vibration isolation, using the polish standards. The experiments were conducted at the Laboratory of Building Materials Engineering at the Cracow University of Technology as part of the project entitled "Innovative construction of vibration-insulating barriers to protect the environment from transport vibrations and similar sources". The concrete composition utilized blast furnace cement CEM III/A 42.5 N, with mineral and chemical additives. Recycled rubber aggregate from used tires was employed to enhance vibration isolation. Measurement results demonstrated the effectiveness of the concrete in dampening vibrations, confirming its suitability for practical use.

Influence of recycled rubber and glass aggregates on magnesium sulfate resistance of geopolymers: Physio-mechanical properties and mechanisms

Recycled rubber aggregates (RRA) and recycled glass aggregates (RGA) are sustainable alternatives to natural aggregates. However, the influences of RRA and RGA on the magnesium sulfate resistance of geopolymers remain unclear. Previous studies have focused on the influences of binder type and composition on magnesium sulfate resistance but have neglected the role of aggregates. This study bridges this gap and demonstrates the influences of RRA and RGA on the magnesium sulfate resistance of geopolymers. This study investigated the physical properties, mechanical properties and phases of FA and GBFS-based geopolymers containing 0:10 – 10:0 RRA and RGA after being exposed to 5 % MgSO4 solution for 90 days. The results showed that compared to 100 % RGA, the 90-day length and mass of 100 % RRA increased by 50.48 and 33.22 times, respectively, and the 90-day compressive, flexural and splitting tensile strengths of 100 % RRA decreased by 65 %, 43.28 % and 56.75 %, respectively. However, the changes in length and mass of 100 % RGA were very small, and the mechanical properties even slightly increased rather than decreased. RRA + RGA showed an interval performance between 100 % RRA and 100 % RGA. The different magnesium sulfate resistance of RRA and RGA were attributed to the following mechanisms. RRA caused much higher drying shrinkage of geopolymers than RGA because the soft nature of RRA increased uncoordinated deformation, leading to micro-cracks in the matrix before magnesium sulfate exposure. The pre-existing micro-cracks served as physical transportation paths for external ions to diffuse into the interior of specimens, leading to expansive gypsum crystals formed in these micro-cracks. The accumulation of expansive gypsum crystals enlarged these micro-cracks and facilitated their propagation, leading to the expansion, cracking and degraded mechanical properties. By contrast, RGA reduced drying shrinkage due to its hard nature, which limited the availability of micro-cracks as physical transportation paths for external ions and therefore reduced the formation of expansive gypsum crystals and improved the magnesium sulfate resistance of geopolymers.

Elastic Properties Study of Composite Mortar with Recycled Rubber Aggregates: with and Without Compatibilizing Agents

Elastic Properties Study of Composite Mortar with Recycled Rubber Aggregates: with and Without Compatibilizing Agents

CORRELATION BETWEEN COMPOSITION OF MASONRY BLOCKS USING RECYCLED RUBBER AGGREGATES AND PROFITABILITY OF PRODUCTION LINE

A correlational study between the composition of masonry blocks with recycled rubber aggregates and the profitability of their production line was carried out. Masonry blocks were designed and manufactured with different contents of rubber aggregates from end-of-life tires. We started from a factorial design of experiments with response surface L4 (22). The factors considered were aggregate granulometry, water/cement ratio and rubber content. The outputs of the experiment were the ultimate compressive strength and the profitability of the production line (IRR/NPV). A model was defined that correlates the input factors with the defined responses. Through an ANOVA, the significant factors on the profitability of the production line in different production scenarios were determined. It was found that there is an inversely proportional relationship between the amount of rubber aggregate and the compressive strength. The maximum aggregate content that allows meeting the resistance requirements of the NTE INEN 3066 standard was 10% (p/p). On the other hand, from the economic-financial analysis it is concluded that the maximum economically profitable rubber content is 5% (p/p). These results make it possible to define the limits of profitability of a production line of masonry blocks that comply with current regulations.

Eco-Design and Characterization of Sustainable Lightweight Gypsum Composites for Panel Manufacturing including End-of-Life Tyre Wastes.

The incorporation of rubber recycled aggregates from end-of-life tyres (ELT) in the manufacturing process of sustainable building materials has gained great interest in recent decades as a result of the large volume of this waste being generated annually. In this work, the objective is to make a contribution towards the circularity of construction products by carrying out a physico-mechanical characterisation of new gypsum composites made with the incorporation of these recycled rubber aggregates. To this end, up to 30% by volume of the original raw material has been substituted, analysing the mechanical resistance to bending and compression. Although lower than those of traditional gypsum material, both properties exceed the limits set at 1 and 2 MPa, respectively, by the current regulations. In addition, water absorption by capillarity significantly decreases, and thermal conductivity is reduced by more than 35% with respect to the reference material. Finally, in order to provide the research with a practical application, a prefabricated plate design has been proposed that incorporates the gypsum materials studied and an agglomerated rubber band that increases the thermal resistance and improves the efficiency of the designed construction system. In this way, this research reflects the potential of these novel building materials and explores new avenues for their application in building construction.

Effect of combination between hybrid fibers and rubber aggregate on rheological and mechanical properties of self-compacting concrete

Rubber aggregate recycled from waste tires are added to self-compacting concrete to improve some of its properties, such as durability, toughness, and concrete resistance to impact and vibrations. In this study, modified hybrid rubberized self-compacting concrete (SCC) was produced by utilization of recycled tire rubber aggregate, plastic waste (PET), and steel fibers. Rubber was used as a partial substitute for sand, with only 10%, while the fibers were utilized in two different proportions of 0.25% and 0.35% (volume). Several tests were achieved to evaluate the rheological properties of the modified hybrid fiber rubberized SCC such as slump flow, T500, V-funnel, L-box, and segregation resistance. In addition, the hardened properties such as density, compressive, tensile strengths, and modulus of elasticity were evaluated. Microstructural evaluation of rubberized mixes was conducted. The results showed that the addition of rubber aggregate at 10% content reduces the rheological properties of SCC. The T500 mm was influenced significantly up to 15% increase. Moreover, compressive strength decreased by about 14% at same amount of rubber aggregate, while the addition of hybrid fibers improves the mechanical properties despite the negative effect on the rheological properties of rubberized SCC. The tensile strengths increased significantly by the inclusion of 0.35% hybrid fibers. The positive action of the two types of fibers led to this increase. The combination of rubber aggregate and the hybrid fibers in SCC could affect its mechanical properties positively by balancing the weakness in strength due to the lack in of bonding between rubber aggregate and cement paste and to avoid the severe deterioration in tensile strength, improve the ductility, and enhance the energy absorption capacity, especially for members subjected to earthquake effects.

Enhancing sustainability and performance in alkali-activated mortars with recycled rubber aggregates subjected to varied curing methods

Rubber waste represents a significant waste stream that can be used as a substitute for natural aggregates in concrete. The main objective of this innovative study is to evaluate the effectiveness of alkali-activated mortars (AAM) incorporating recycled rubber aggregates in the development of an environmentally friendly construction material. Different replacement rates of sand with rubber particles (10%, 20%, and 30% by volume) are analysed. Rubberized alkali-activated mortars (RAAM) were produced using a combination of 10 M sodium hydroxide (NaOH) and a Na_2 SiO_3/NaOH ratio of 3. Additionally, the influence of three curing methods on the properties of RAAM is also examined: air drying, curing in a climate chamber, or in an oven. The properties of RAAM were evaluated through tests including the flow table test, density test, water absorption test, and compressive strength test. Furthermore, the study also assessed the cost-effectiveness and environmental impact of RAAM. This variable study is complemented by an ANOVA parametric analysis. The results show a decrease in the compressive strength and flowability of AAM proportionally to the increase in R content. Experimental and statistical analysis reveal that curing in an oven at 60°C significantly optimizes compressive strength by approximately 50.52%. It is worth noting that this curing method of RAAM has demonstrated superior economic and environmental benefits compared to OPC mortar. The study highlights the strong potential of RAAM cured at 60°C or in a humid chamber, combining mechanical performance with reduced CO_2 emissions, as a sustainable and eco-friendly solution to replace traditional concrete.

Optimization of the Impact of Dune Sand, Recycled Rubber Aggregates, and Clay Brick Waste on Eco-Mortar Mechanical Strength by the Taguchi Method

Utilizing local materials and recycling waste has the potential to yield both ecological and economic advantages in the field of construction materials. In this context, the object of this work is to apply Taguchi's design of experiments on cement eco-mortar, which were designed using an L-9 orthogonal array, to optimize and model the effect of dune sand of the El Oued region, rubber aggregates, and crushed clay brick waste on the mechanical strength at 28 days. The different interactions were also investigated between the factors targeted in our study, namely: dune sand (DS) content, rubber aggregates (RA) content, and brick waste (BW) content. The results of the analysis of variation (ANOVA) as well as the mathematical models developed in this study showed that the BW factor content has a positive effect on compressive strength and a negative effect on flexural strength. In addition, the interactions between DS and BW contents and between RA and BW contents have a negative effect on the compressive strength of eco-mortar. With regard to flexural strength, the results showed that the interaction between the factors DS and RA contents has a negative effect on flexural strength, in contrast to the interaction between the RA and BW contents, which has a positive effect.

THE EFFECT OF RECYCLED RUBBER AGGREGATES AND DUNE SAND OF EL-OUED REGION ON THE COMPRESSIVE STRENGTH OF CEMENTITIOUS MORTAR: OPTIMIZATION USING TAGUCHI METHOD

This study optimizes the effect of recycled rubber aggregates and dune sand of El-Oued's region by maximizing the compressive strength of cementitious mortar using Taguchi's design experiments. The experiments were designed using an L9 orthogonal array to see the different relationships between the factors targeted in our research, namely: water/cement (W/C) ratio, rubber aggregates (RA) content, and dune sand (SD) content, with the levels of each factor in the mortar mixture. The samples were tested at 28 days in each of the nine trial conditions for two responses: compressive strength and ultrasonic pulse velocity. The results of the analysis of variation (ANOVA) show that RA content is the factor that has the largest effect on the two tests, and the second factor affecting the two tests is the W/C ratio. Then, the analysis shows that the SD content has no significant effect on the mechanical resistance of the mortar for the two tests. And from the mathematical models investigated in this study, we conclude that the factors RA content and W/C ratio have a negative influence on the responses of the compression test and the ultrasonic test together

Mechanical behaviour of wollastonite-based cement composites incorporating fibres and recycled rubber aggregates

Calcium phosphate cement (CPC) is a wollastonite-based inorganic cement that hardens at room temperature to a brittle cementitious material with low fracture behaviour. Recycled rubber aggregates from end-of-life tyres were incorporated up to 17.5 wt% into the CPC matrix to produce high-strength composites with improved strain capacities for structural repair purposes. Furthermore, the effects of 0.75% and 1.5% volume fibre content (Vf) of macro polypropylene, amorphous metallic and recycled carbon fibres on the flexural behaviour of CPC were studied. The synergy between the rubber aggregates and the selected corrosion-resistant fibres in improving the fracture properties of the plain CPC was investigated. The changes in other mechanical properties of CPC such as modulus of rupture, compressive and splitting tensile strength due to the inert inclusions (i.e. rubber aggregates and/or fibres) were determined. It was found that increasing the quantity of inert inclusions in the cement matrix improved the fracture energy of the plain CPC. Incorporating 1.5% Vf of macro polypropylene, amorphous metallic, and recycled carbon fibres into the CPC matrix produced cementitious composites with fracture energies that were 11.8 times, 63.4 times, and 75.8 times that of plain cement, respectively. For the rubberised fibre-reinforced CPC composites, a positive synergistic relationship was observed between rubber aggregates and macro polypropylene fibres while a negative synergistic relationship was found between rubber aggregates and the other fibres (amorphous metallic and recycled carbon fibres). The rubber aggregates decreased the flexural, compressive and splitting tensile strengths of the plain CPC, while the fibre inclusions improved these properties.

Prediction of diffusion properties of cement-based materials incorporating recycled rubber aggregates: Effect of microstructure on macro diffusion properties

In recent years, significant progress has been made in the development of new, eco-friendly, cement-based materials. However, predicting their durability from the new material composition is still a challenging task. There have been very few studies of micromechanical models based on micro-geometric features on cement-based materials incorporating recycled rubber aggregates. In this context, a multiscale model using the microstructural characteristics is proposed to predict their diffusion properties. After the description of the physically-based approach, its accuracy is evaluated by comparing the model predictions with experimental results from mortars with different types of aggregates (natural sand and rubber). In the study, it is assumed that diffusion of ionic species occurs primarily through the porous network of the cement matrix, but also takes place at the matrix-aggregate interface transition zone (ITZ). The method used for modelling is based on homogenization schemes and the spherical n-phase inclusion model which allow the ITZ to be taken into account.

Effect of the Incorporation of Recycled Rubber Aggregates on the Behavior of Self-Compacting Concrete

Effect of the Incorporation of Recycled Rubber Aggregates on the Behavior of Self-Compacting Concrete

Energy Dissipation and Dynamic Fragmentation of Alkali-Activated Rubber Mortar under Multi-Factor Coupling Effect.

Recycled rubber aggregate (RRA) made from ground tire rubber has been promoted for its light weight and shock resistance. The high alkalinity of alkali-activated slag mortar has a modification effect on the surface of RRA. This paper studies the performance of alkali-activated slag mortar using RRA as aggregate (RASM), which has significance for applications in low-carbon building materials. The orthogonal test analysis method was used to analyze the significance and correlation of the main variables of the test. The dynamic energy absorption capacity and crushing state of RASM under the synergistic effect of various factors were studied using the separating Hopkinson pressure bar (SHPB) test system. The energy absorption characteristics and failure modes of RASM were analyzed by SEM and microscopic pore characterization. The results show that the increase of the alkali equivalent of the mix ratio will increase the peak value of the absorption energy of the specimen. When the size of the RRA is between 0.48 mm~0.3 mm, the dynamic energy absorption of the specimen will reach its peak value. Although the increase in the total volume of RRA will reduce the energy absorption capacity of RASM specimens, its crack resistance is enhanced.

Evaluation of the effect of recycled rubber aggregate size on concrete for sustainable applications of rubberised concrete in impact resistant structures: Experimental and numerical study

Rubberised concrete has been suggested for structures subjected to dynamic loadings, such as impact and blast, however, the understanding of the dynamic behaviour with rubber replacement and the influence of the particle size is still limited. This paper investigates the impact behaviour of rubberised concrete using both experimental and numerical studies. Split Hopkinson Pressure Bar tests under higher strain rates up to 181 s−1 were used to analyse the experimental dynamic behaviour using concrete specimens with a low volume of coarse and fine aggregates replaced by tyre shreds (15 mm) and tyre crumbs (2–4 mm), respectively. Under the same impact, rubberised concrete specimens demonstrated ductile failures, high dynamic increase factors, and increased normalised toughness moduli. Furthermore, rubberised concrete with the larger tyre particles showed increased ductility and normalised toughness moduli than that with the smaller tyre particles. Conversely, the specimens with smaller tyre particles were revealed to have higher dynamic strengths and dynamic increase factors. The numerical model in LS-DYNA, using the Karagozian and Case material model, was calibrated to reflect the observed rubberised concrete experimental performance. The calibration technique was validated by accurately predicting the dynamic tyre particle size effect of rubberised concrete numerically. The results proved that low-level rubber replaced concrete can be potentially used in impact resistant structures as there is a good balance between quasi-static and increased dynamic impact resistance for more sustainable constructions.

Experimental and Statistical Investigation to Evaluate Impact Strength Variability and Reliability of Preplaced Aggregate Concrete Containing Crumped Rubber and Fibres.

The proper disposal of used rubber tires has emerged as a primary concern for the environment all over the globe. Millions of tires are thrown away, buried and discarded every year, posing a major environmental concern owing to their slow decomposition. As a result, it is advantageous to use recycled waste rubber aggregates as an additional building resource. Recycling crushed rubber would lead to a long-term solution to the problem of decreasing natural aggregate resources while conserving the environment. This study examines the impact strength variability and reliability of preplaced aggregate concrete containing crumped rubber and fibres. Ten different mixtures were prepared by replacing natural aggregate with crumped rubber (5, 10, 15 and 20%). The crumped rubber was pretreated by the water with sodium hydroxide dilution for 30 min before usage. Hooked-end steel fibres were used at a dosage of 1.5%. The compressive strength, impact strength, impact ductility index and failure pattern were examined and discussed. In addition, a statistical method called Weibull distribution is used to analyze the scattered experimental results. The results showed that when the crumb rubber content was raised, the retained first cracking and failure impact numbers increased. As a result of substituting crumb rubber for 20% of the coarse aggregate in plain and fibrous mixes, the percentage development in first crack and failure was between 33% and 76% and 75% to 129%, respectively.