Self-compacting Rubberized Concrete Research Articles

Investigation of the static constitutive relationship of rubberized self-compacting concrete after high-temperature exposure

Rubber self-compacting concrete (RSCC), recognized as an environmentally friendly material, possesses excellent resistance to impact. However, the inclusion of rubber particles significantly decreases its compressive strength. This study investigated the compressive properties of RSCC with rubber particles substituting for fine aggregate volume percentages of 0 %, 10 %, 20 %, and 30 % after exposure at 25, 300, 600, and 900 °C for 3 h. The interface conditions among the rubber particles and the mortar were examined using scanning electron microscopy (SEM). The findings reveal that: (1) Both the compressive strength and the modulus of elasticity of RSCC exhibit a pronounced decline as the exposure elevates, with the maximum reduction reaching 84.25 % and 89.42 % respectively (where the substitution percentage of rubber particles is 30 %), compared to values at room temperature. Conversely, the peak strain exhibited an increase of 130.41 % (with the substitution percentage of rubber particles being 30 %). (2) As the substitution percentage of rubber particles increases, the decline in RSCC's compressive strength and elastic modulus after cooling at elevated temperatures is less noticeable than at room temperature, and the peak strain of RSCC exhibits negligible increase after being subjected to high temperatures. (3) Prediction equations and constitutive models for the compressive strength and peak strain of RSCC post-high temperature exposure are proposed in light of the experimental data. The comparison shows an obvious connection between the experimental outcomes and the predictive results.

Optimization of recycled rubber self-compacting concrete: Experimental findings and machine learning-based evaluation

This research aims to assess the rheological and mechanical characteristics of Self-compacting concrete (SCC) incorporating waste tire rubber aggregates (WRTA) as an interim substitute for coarse aggregates. However, the standard experimental modeling approach has significant obstacles when it comes to overcoming the nonlinearity and environmental susceptibility of concrete parts. Therefore, linear regression (LR) and extreme gradient boosting (XGBoost) were used as two standard single machine learning (ML) models to predict the aforementioned rubberized SCC features. In this study, conventional coarse aggregates were supplanted with WRTA at 0%, 5%, 10%, and 20% to uncover the optimal proportion of coarse aggregates substituting rubber. To find the optimum amount of WRTA to use as a substitute, the study follows the impacts of rubber on the self-compacting rubberized concrete's (SCRC) rheological and mechanical characteristics. The consequences on fresh properties were investigated by the slump flow, J-ring, and V-funnel tests, while compressive and splitting tensile strengths tests were conducted to assess mechanical properties. Increasing WRTA test outputs indicated a deterioration in workability and hardened qualities. While a 10% swapping ratio is deemed feasible for producing SCRC, optimal results were achieved by reducing environmental impacts and efficiently managing a significant volume of rubber tire waste with a 5% substitution of rubber within the coarse aggregates. The research findings indicated a noticeable decrease in fresh properties as the WRTA content increased. Notably, after 28 days, a 10% WRTA substitution led to a 34% reduction in compressive strength and a 28% decrease in splitting tensile strength, satisfying ACI standards. Furthermore, XGBoost demonstrated superior predictive performance with the highest R2 values, outperforming the LR model and affirming its efficacy in delivering more accurate predictions.

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.

Evaluation of self-compacting rubberized concrete properties: Experimental and machine learning approach

Diverse negative impacts of waste tire disposal have created a menace to a cleaner environment worldwide. Global awareness on the use of unconventional materials in concrete necessitated the use of solid waste in concrete. Towards sustainable construction and building materials, in this study, powdered waste rubber tires (PWRT) were incorporated into self-compacting concrete as a partial substitute for fine aggregate. The suitability of the self-compacting rubberized concrete (SCRC) was assessed by conducting workability tests (slump flow, T50, and L-box), mechanical tests (compressive, splitting tensile, and flexural strength tests), microstructural analysis, and durability tests. The results showed that an increasing percentage of PWRT had an adverse effect on the workability and flowability of SCRC. Mechanical strength at 3, 7, 21, 28, 56, and 90 days exhibited a reduction with an increasing PWRT content. Furthermore, the microstructural analysis showed weaker adhesion at the interfacial transition zone in the SCRC. A correlation matrix with empirical relationships was also developed. The effect of acid attack on SCRC was measured by immersion in HCL and Na2SO4, and a poor resistance was noticed. Machine learning regression algorithms were employed to predict the SCRC mechanical properties, including linear, ridge, lasso, decision tree, random forest, extreme gradient boosting, and support vector. In addition, evaluation metrics with statistical checks were also used to assess the model's performance. Ridge regression appeared best suited for predicting the compressive strength, while random forest regression best estimates the tensile and flexural strength.

Durability Performance and Thermal Resistance of Structural Self-Compacting Concrete Improved with Waste Rubber and Silica Fume

Waste rubber takes many years to decompose, and thus the increasing number of tires in the world can be characterised as an important environmental issue, which generated the idea of implementing crumb rubber in structural self-compacting concrete (SCC). According to previous studies, up to 15% recycled rubber and 5% silica fume can be used to achieve the required properties of SCC in reinforced structural members with congested reinforcement, both in the fresh and hardened state. Most studies have focused on investigating the mechanical properties of self-compacting rubberised concrete (SCRC), and only a small number of studies investigated the durability and thermal properties, with contradictory findings. This study aims to determine the influence of crumb rubber and silica fume on the durability and thermal properties of SCC, with an emphasis on the selection of environmental exposure classes, the safety of using such a material in reinforced concrete members, and additional serviceability and durability requirements. This was further advanced by investigating the micro-structure of hardened SCC with recycled rubber and silica fume using a scanning electron microscope (SEM). Test results indicate that the combining effect of crumb rubber and silica fume has a positive impact on the thermal and durability properties of SCC.

Experimental and numerical investigation on fracture characteristics of self-compacting concrete mixed with waste rubber particles

Replacing natural aggregates in concrete with waste rubber particles is an effective method to solve environmental problems, but the use of rubber due to its unknown characteristics can change the fracture performance and cracking behavior of self-compacting concrete. Hence, through experimental analysis and discrete element method (DEM) simulation, this paper aims to investigate the influence of different rubber contents (0%, 10%, 20% and 30%) on fracture characteristics of self-compacting concrete. Compared with natural river sand, rubber particles have more flexible structure and stronger deformation ability, and these unique properties enhance the bridging effect between matrices and weaken the stress concentration at the crack tip, which shows that the fracture parameters of self-compacting rubberized concrete (SCRC) increase linearly with the increase of rubber content, and this linear growth rate will increase with the increase of beam size. Moreover, the addition of rubber particles absorbs most of the energy generated in the fracture process, which significantly enhances the anti-cracking ability of SCRC, and this ability to prevent crack propagation will be enhanced with the increase of rubber content, which is manifested by the significant decrease of acoustic emission (AE) activity. Based on the shapes of real aggregates and rubber particles, a universal DEM fracture prediction model for SCRC is established, which can better describe the fracture response of SCRC with different rubber contents and sizes under flexural loads. The evaluation of economic and environmental benefits indicates that adding rubber particles into self-compacting concrete can not only save costs, but also produce considerable environmental benefits.

Experimental Study of Crack Characteristics of Self-Compacting Rubberized Concrete under Four-Point Bending Based on Acoustic Emission Technique

Experimental Study of Crack Characteristics of Self-Compacting Rubberized Concrete under Four-Point Bending Based on Acoustic Emission Technique

Mechanical Properties of Self-Compacting Rubberized Concrete with Different Rubber Types under Triaxial Compression

Different rubber aggregates lead to changes in the effect of stress conditions on the mechanical behavior of concrete, and studies on the triaxial properties of self-compacting rubber concrete (SCRC) are rare. In this study, 35 cylindrical specimens taking lateral stress and rubber type as variables were prepared to study the fresh properties and mechanical behaviors of SCRC under triaxial compression, where the rubber contains two types, i.e., 380 μm rubber powder and 1–4 mm rubber particles, and four contents, i.e., 10%, 20% and 30%. The test results demonstrated that SCRC exhibited a typical oblique shear failure mode under triaxial compression and had a more moderate descending branch compared with self-compacting concrete (SCC). The presence of lateral stress can significantly improve the compression properties, including initial elastic modulus, peak stress and peak strain, with an improvement range of 3%–73% for peak stress. While rubber aggregates mainly targeted the deformation abilities and toughness for improvement, and the peak strain improvement ranges were 0.1–3.1 times and 0.1–1.0 times for SCRC containing rubber powder and SCRC containing rubber particles, respectively, relative to SCC. At a high lateral stress of at least 12 MPa, the loss of strength due to the addition of rubber can be controlled within 10%, in which case the content of rubber powder and rubber particles was recommended to be at most 20% and 30%, respectively. Based on the Mohr-Coulomb theory, the failure criteria of SCRC with different rubber types were established. For analysis and design purposes, an empirical model was proposed to predict the stress-strain behavior under triaxial compression, considering the influence of different rubber content and lateral stress. The results obtained in this study can provide a valuable reference for the design and application of self-compacting rubberized concrete in practical projects, especially those involving three-way compression states and requiring high-quality deformation and energy dissipation.

Fracture behavior investigation of self-compacting rubberized concrete by DIC and mesoscale modeling

The Digital Image Correlation technique recorded the process of self-compacting rubberized concrete (SCRC) under a pre-notched three-point bending beam. Load-crack opening displacement curves were measured, and the fracture process zone and crack opening displacement were comparatively analyzed to investigate the effect of rubber content and notch depth. The test results show that the incorporation of rubber increases the fracture toughness and fracture energy of the self-compacting concrete, and the increased amount is related to the incorporation amount of rubber. The fracture pattern of the specimen has also changed due to the incorporation of rubber. Finally, a mesoscopic model was proposed and verified by comparing the numerical simulation and test results.

A comprehensive review of the features of self-compacting rubberized concrete in the fresh and hardened states

A comprehensive review of the features of self-compacting rubberized concrete in the fresh and hardened states

Experimental and mesoscopic investigation of self-compacting rubberized concrete under dynamic splitting tension

Self-compacting rubberized concrete (SCRC) has gained extensive investigations due to its good impact resistance and environmental friendliness, while the dynamic splitting tensile properties of SCRC are seldom studied. In this study, river sand in SCRC was replaced by three rubber volume fractions (5%, 10%, 15%). The experiments indicated that the static compressive strength, static tensile strength, elastic modulus and dynamic splitting tensile strength declined with the increase of rubber content. The dynamic splitting tensile strength, dynamic increase factor (DIF) and failure mode of SCRC were sensitive to strain rate. SCRC with a higher rubber volume had a greater DIF. The critical strain rate of different SCRC was obtained by piecewise fitting, which decreased with the enhancement of rubber content. Meanwhile, a three-dimensional mesoscopic model of SCRC was established. The rubber particles were generated by a random polyhedron algorithm and randomly thrown into the sample by the take and place algorithm. The numerical calculation suggested that the mesoscopic model could exhibit the fracture process of SCRC under high strain rates. The propagation of cracks bypassed the rubber particles and produced a mass of branch cracks under high strain rates, dissipating a large amount of energy and elevating the DIF, which is consistent with the macroscopic failure pattern. In addition, the effect of strain rate and rubber volume on DIF was discussed combined with the mesoscopic model.

Investigation on Bond Behavior between Self-compacting Rubberized Concrete and Rectangular Steel Tubes

Investigation on Bond Behavior between Self-compacting Rubberized Concrete and Rectangular Steel Tubes

Preparation and properties of integrally hydrophobic self-compacting rubberized concrete

Brittleness and water invasion are critical reasons for the deterioration and failure of ordinary self-compacting concrete (SCC). To enhance the deformability and water repellency of SCC, integrally hydrophobic self-compacting rubberized concrete (HSCRC) was prepared by adding crumb rubber (CR) and a hydrophobic agent (HA) into ordinary SCC. Furthermore, the combined effect of CR and HA on the fresh properties, hydrophobicity and mechanical properties of HSCRC were comprehensively studied. The results showed that the addition of CR resulted in a decline in the flowability, filling ability and passing ability and an enhancement in the viscosity and anti-segregation properties. However, the effect of adding HA on the fresh properties was opposite to that of adding CR. The surfaces of the samples mixed with the HA obtained contact angles greater than 130°, and the 48-hour capillary water absorption and the 48-hour immersion water absorption of these samples were significantly reduced. Moreover, the compressive strength, splitting tensile strength, axial compressive strength and elastic modulus of the concrete samples decreased gradually with the increase of CR and HA content. Multiple regression models between different mechanical properties and CR and HA contents, as well as the conversion formulas between different mechanical properties, were obtained.

Experimental and analytical study on the mechanical properties of rubberized self-compacting concrete

Rubberized self-compacting concrete (RuSCC) is a newly developed material with the advantages of smaller environmental pollution and improved properties. Validated prediction models of mechanical properties are vital for RuSCC’s application in engineering structures and functional facilities. This paper aims to investigate the influence of rubber aggregates on RuSCC’s mechanical properties by experimental and analytical studies. The experiments explore the mechanical properties of RuSCC with a larger range of rubber ratio than existing studies. The results show that RuSCC with the largest rubber volume ratio of 80% coarse aggregate has the compressive strength, elastic modulus and splitting strength of 14.3%, 25.5% and 16.9% of reference self-compacting concrete (SCC). Increase in RuSCC’s toughness and gradient of post-peak slope is observed from compressive stress-strain curves, indicating higher ductility of RuSCC. Prediction models for RuSCC’s mechanical properties are developed and validated by a database built from reported experiment results. The models show that the decrease of RuSCC’s relative compressive strength is related to the increase of rubber’s ratio and reference SCC’s compressive strength, as well as the replacement of coarse aggregate and the incorporation of supplementary cementitious materials that are not fly ash. Compressive stress-strain constitutive model for RuSCC is developed by modifying SCC’s model and the model predicts the stress-strain curves with good accuracy. The advantages and limitations of proposed model are also discussed following a comparative assessment of its performance on predicting RuSCC’s mechanical properties.

Creep Behavior of Self-Compacting Rubberized Concrete at Early Age

Creep Behavior of Self-Compacting Rubberized Concrete at Early Age

Experimental and Numerical Investigation of Fracture Behaviors of Steel Fiber–Reinforced Rubber Self-Compacting Concrete

This paper presents the experimental and numerical studies of flexural-fracture behaviors of steel fiber–reinforced rubber self-compacting concrete (SRSCC) materials. The scrap-tires rubber aggregate was used to partially (10%, 15%, and 25%) replace the fine aggregate based on its volume for SRSCC samples, and the microsteel fiber was introduced with an addition ratio of 0.2% based on the entire mixture volume. The plain self-compacting concrete (SCC) and the rubberized SCC specimens were produced for comparison. The three-point bending test on the single-edge notched beam showed the increased flexural strength and total fracture energy of SRSCC samples by adding steel fiber and rubber. The critical fracture parameters including initial fracture energy (Gf) and fracture toughness (KІc) were determined based on the Load-CMOD curves and two parameters fracture model. With these properties, the bilinear tension-softening model (aggregate interlock effect) and trilinear tension-softening model (aggregate interlock and fiber-bridging effects) were calibrated for normal SCC and SRSCC, respectively. The tension-softening functions were utilized in the FEM model to predict the flexural-fracture behaviors of corresponding specimens, and the numerical simulation results showed reasonable agreement with experiments. Overall, the experimental testing data and numerical simulation model can reveal the detailed fracture behavior of SRSCC for future improved material design.

Investigation on the dynamic compressive behavior of waste tires rubber-modified self-compacting concrete under multiple impacts loading

The rubberized self-compacting concrete (RSCC) combines the better ductility and toughness of rubber aggregates and the better working performance of self-compacting concrete (SCC), and has gained popularity. In practice, concrete structures often suffer multiple impacts loading during their service life. Therefore, this work investigates the dynamic compressive properties of RSCC under multiple impacts loading by the split Hopkinson bar technique (SHPB) and takes the influences of rubber content, impact velocity, and thermally treated temperature into consideration. The results indicate that the incorporation of rubber aggregate gives the SCC better ductility and toughness, especially by a rubber content of 20%. The resistance to multiple impacts loading, the resistance to deformation, and the ability to absorb energy are all enhanced by the rubber aggregates. Furthermore, the thermal treatment shows a slight strengthening effect on the dynamic resistance of SCC but SCC still maintain its characteristic of brittleness. The thermal treatment shows a significant attenuation effect on the dynamic response of RSCC.

Equivalent CO2 Emission and Cost Analysis of Green Self-Compacting Rubberized Concrete

Global warming and climate changes are the major environmental challenges globally. With CO2 emission being one of the main greenhouse gases emitted to the environment, and cement and concrete production amounting to about 10% of the global CO2 emission, there is a need for the construction industry to utilize an environmentally sustainable material as an alternative to cement. This study analyzed the cost, CO2 emission and strength properties of green self-compacting concrete (SCC) ternary blend containing fly ash, calcium carbide residue (CCR), and crumb rubber (CR) as a replacement material by volume of cement, cementitious material, and fine aggregate, respectively. Cement was replaced with fly ash at 0% and 40% by volume. CCR was used as a replacement at 5% and 10% by volume of cementitious materials, CR replaced fine aggregate in proportions of 10% and 20% by volume. The result indicated that the mix with 0% fly ash and 20% CR replacement of fine aggregate was the most expensive and had the highest CO2 emission. However, the mix with 10% CR, 40% fly ash, and 10% CCR had the lowest CO2 emission and was therefore the greenest SCC mix. The 28-day maximum compressive strength of 45 MPa was achieved in a mix with 0% CR, 0% fly ash, and 10% CCR, while the utmost 28-day splitting tensile strength of 4.1 MPa was achieved with a mix with 10% CR, 0% fly ash, and 5% CCR, and the highest flexural strength at 28 days was 6.7 MPa and was also obtained in a mix with 0% CR, 0% fly ash, and 5% CCR. In conclusion, a green SCC can be produced by substituting 40% cement with fly ash, 10% fine aggregate with CR, and 10% CCR as a replacement by volume of cementitious material, which is highly affordable and has an acceptable strength as recommended for conventional SCC.

Modeling of Compressive Strength of Self-Compacting Rubberized Concrete Using Machine Learning.

This paper gives a comprehensive overview of the state-of-the-art machine learning methods that can be used for estimating self-compacting rubberized concrete (SCRC) compressive strength, including multilayered perceptron artificial neural network (MLP-ANN), ensembles of MLP-ANNs, regression tree ensembles (random forests, boosted and bagged regression trees), support vector regression (SVR) and Gaussian process regression (GPR). As a basis for the development of the forecast model, a database was obtained from an experimental study containing a total of 166 samples of SCRC. Ensembles of MLP-ANNs showed the best performance in forecasting with a mean absolute error (MAE) of 2.81 MPa and Pearson’s linear correlation coefficient (R) of 0.96. The significantly simpler GPR model had almost the same accuracy criterion values as the most accurate model; furthermore, feature reduction is easy to combine with GPR using automatic relevance determination (ARD), leading to models with better performance and lower complexity.

Acoustic emission characteristics of fatigue failure process of self-compacting rubberized concrete pavement slabs

ABSTRACT To explore the fatigue characteristics of self-compacting rubberized concrete (SCRC) pavement, notched slabs with a 10% rubber content were fabricated. Monotonic and fatigue tests were carried out, including incremental amplitude tests controlled by crack mouth opening displacement (CMOD), load, and alternative constant and incremental amplitude loads. Meanwhile, the fracture process was dynamically monitored with acoustic emission (AE), and the failure characteristics were analyzed based on AE parameters. Under monotonic loads, cracks mainly develop along with the interface between aggregates or rubber particles and cement. The cumulative ring counts and damage evolution show a three-stage distribution. The b-value fluctuates dramatically initially and less in the middle and later stages under monotonic tests. Under fatigue loads, brittle fractures are significant and fatigue life increases. Only one inflection point appears in the cumulative ringing counts curve and damage evolution curve, the critical damage is lower. The fluctuation range of the b-value are higher. The cumulative ringing counts, AE signal intensity, damage parameter based on AE energy, and b-value can dynamically reflect the crack growth and damage evolution of SCRC slabs. The fracture mode analysis based on AF-RA manifests cracks are mainly tensile, and the fracture mode is the type I.