Waste Rubber Research Articles

Behaviour of Paver Block by Addition of Waste Rubber

Concrete is one of the widely used construction material in the construction industry. The durability and aesthetics aspects of concrete made it to use in making paver blocks which are used in outdoor versatility application as street road, sidewalks, and other Construction places. Paver block has low cost maintenance and easily replace with a newer one at the time of breakage. The quality of concrete used to make paver block may be the major issue, so that the durability of paver block depends on quality of concrete. Rubber is used in different fields throughout the world. But the utilization or disposal of waste rubber after its regular. Thus an attempt is made by inclusion waste rubber into the concrete and to measure how rubber affects the properties of paver block. This research study presents the information about the development of the rubber mould paver block with inclusion waste rubber.

INVESTIGATION OF MODIFICATION OF PETROLEUM BITUMEN BY RUBBER WASTE

According to scientific research in different countries, rubber granules obtained from rubber waste during recycling can improve the properties of the asphalt mixture, thereby extending the service life of the road surface. This paper presents the modification of bitumen with industrial rubber waste. Modification of bitumen for roads is considered one of the most suitable and popular approaches. This research paper describes the details of using different types of rubber granules as bitumen modifiers. The main physical and mechanical characteristics of the modified bitumen were determined after conventional tests, penetration and ductility, softening point, Fraas brittleness point. In order to obtain a rubber-asphalt concrete mixture with improved performance characteristics, the viscoelastic and rheological properties of rubber-bitumen binders and their comparison with polymerbitumen binders were also studied. The research results show that with increasing temperature, the values of viscosity, shear stress and complex shear modulus of all studied bitumen systems decrease, and the values of the phase shift angle increase, and that the size of the rubber particles has a greater influence on the properties of bitumen systems.

STUDY OF NON-FUEL APPLICATION OF BROWN COAL DERIVATIVES FOR BITUME MODIFICATION

The article shows research into the non-fuel use of brown coal derivatives for the modification of bitumen. The work used petroleum road grade bitumen BND 60/90 with a flash point in an open crucible of 260 °C, a softening temperature (using the ring and ball method) of 48 °C, resin after lignite thermal destruction and rubber waste. and powder. Based on the fact that the most relevant technologies for the non-fuel use of brown coal concern areas aimed at obtaining wax, humane preparations, adsorbents, obtaining valuable derivatives in the form of resins, GR, etc., an assessment was made of the non-fuel use of brown coal derivatives for modification bitumen. Analysis of the experimental results showed that the studied quality indicators of the composition samples, which include waste rubber powder, have an increased complex of both thermophysical and physical-mechanical characteristics. This is obviously due to the fact that, as a result of thermal destruction of rubber powder, the swelling process occurs faster compared to crumb rubber with a size of 2.5–4.5 mm. However, the process of destruction and dispersion in both cases does not occur completely, of course, and the volume of edematous rubber particles contains resins and polyaromatic components that affect the value of both thermophysical and physical-mechanical characteristics. Thus, it has been established that the optimal composition for creating effective polymer-modified bitumens with an increased complex of thermo-physical and physical-mechanical characteristics is 40 % by weight of rubber powder and 5 % by weight. brown coal resins after thermal destruction. It is shown that the results of laboratory studies have proven the prospects of using brown coal tar after thermal destruction for the modification of road bitumen. Summarizing research into the direction of non-fuel use of brown coal derivatives in the form of liquid products – tar resins of brown coal after thermal destruction for the modification of bitumen materials, it should be noted that the results obtained are moderate in comparison with existing directions for the production of polymer-modified bitumens. Modification of bitumen with primary and secondary polymers makes it possible to significantly improve their adhesion and performance characteristics compared to brown coal resins after thermal destruction. The use of brown coal resins after thermal destruction is much less effective in improving the elasticity, heat resistance and reducing the fragility of bitumen compositions compared to the use of thermoplastic and thermoelastomer modifiers in the production of polymer-modified bitumens.

Life-cycle assessment of sustainable pavement based on the coordinated application of recycled asphalt pavement and solid waste: Environment and economy

To achieve efficient use of recycled asphalt pavement (RAP) produced during the maintenance and expansion of old roads and to solve the problem of low utilization of steel slag and desulfurization ash generated in the production process of the steel industry, this study designed a sustainable pavement using RAP and waste rubber powder-modified asphalt to form a matrix skeleton with large voids and injects grouting materials prepared with desulfurization ash and steel slag. It was found that the designed sustainable pavement has excellent high-temperature permanent deformation resistance and durability. Compared to traditional asphalt pavement, sustainable pavement's energy consumption and emissions can be reduced by about 45% within a single life cycle, while the economic benefits exceed about 500%. Moreover, sustainable pavement's excellent fatigue resistance will make its energy-saving, emission-reduction effects, and economic benefits more significant than traditional asphalt pavement during the same analysis period.

Flue gas suppression and environmental evaluation of deodorizer-modified rubber asphalt based on radar method

Rubber-modified asphalt (RMA) is associated with impaired storage stability and additional harmful emissions during application. Microwave-oil bath activation of waste rubber powder (WRP) to improve its compatibility with asphalt. The treatment of VOCs and malodorous gas emissions from RMA is carried out using powder deodorizers, liquid deodorizers and their combination. The storage stability, high and low temp rheological behavior of RMA were investigated. The effects and machinations of three deodorants on odor removal and VOCs inhibition of RMA were explored. The emission indexes based on the characteristic pollutants of VOCs and malodorous gases were proposed to conduct a comprehensive environmental impact assessment by the Radar method. The results show that the activated WRP has a fluffier morphology and is better encapsulated by the oil film, which enhances the storage stability of RMA. The incorporation of deodorant has not altered the viscoelastic properties of asphalt. The higher specific surfaced areas and extensive pore structures was contributed to the adsorption of VOCs molecules from asphalt. VOCs and odor gases from asphalt could be inhibited by liquid deodorizers based on Lewis acid-base reactions, addition reactions, catalytic reactions, and redox reactions. LMA was the most effective in decreasing odorant gases, with reductions of up to 92.6% and 90.8% for isobutanol and dimethyl disulfide, respectively. PMA had the optimal inhibitory activity for vinyl chloride, which was 67.7%. The decrease of total concentration of VOCs in RMA by PMA (powder deodorant-modified asphalt), LMA (liquid deodorant-modified asphalt), and CMA (complex deodorant-modified asphalt) could be calculated as 51.7%, 34.1% and 46.7% respectively. RMA had a high load on the environment, and the overall advantage of CMA was greater. The environmental impacts of the four modified asphalts were ranked as CMA < PMA < LMA < RMA. Therefore, the utilization of powder and liquid compounding was recommended to improve the environmental impact of RMA.

Investigation of vibration, flexural, tribological and flame retardant properties on rubber crumb-reinforced polymer composites

This research aims to fabricate polymer matrix composites with improved mechanical, flame retardant, and damping properties by incorporating waste rubber crumbs as the reinforcement. The damping characteristics of the polymer matrix composites reinforced with different weight percentages of rubber crumb such as 0, 2.5%, 5%, and 7.5% were analyzed using a free vibration test. The experimental results confirmed that the addition of rubber crumb significantly improved the damping characteristics of the material. In addition, the rubber crumb-reinforced composites showed improved mechanical and fire-retardant properties. The flexural strength improved exceptionally with the increase in rubber reinforcements up to 7.5%, whereas the tensile strength increased up to 2.5% weight and reduced with the further increase in rubber. Enhanced flame-retardant properties were witnessed in the polymer composites reinforced with rubber crumb than that of the plain Epoxy - Glass fibre composites. Thermogravimetric analysis (TGA) were also used to ascertain the thermal properties. The scanning electron microscope was employed to analyze the surface and fractography of the polymeric composites. The overall results showed the contemporary effect of rubber crumbs on polymer composites.

Effect of combined waste oils on the chemical, thermal, microscopic, and rheological properties of devulcanized waste tire rubber

This research investigates the influence of combined waste oils process variables, including the mass ratio of waste engine–cooking oil (WECO), medium reaction temperature for a constant reaction time, and waste tire rubber (WTR) mesh size, on the chemical properties, rheological properties, and thermal behavior of combined waste oil devulcanized WTR. The samples' chemical elements and bonding energy changes were characterized and their sol friction, thermal behavior, morphology, and rheological properties were analyzed. Different proportions of mixed WECO can devulcanize WTR under medium temperature. WECO with increased reaction temperature and waste engine oil improves WTR's devulcanization (mesh size: 80). The waste oil content significantly increased the WTR morphology quality and reduced its surface roughness. The de-crosslinked structure produced compound structural changeover. Thus, the rheological effects were significant. For devulcanized waste rubber engine–cooking oil, G* decreased gradually and δ° increased progressively, and its anti-fatigue performance increased as the fatigue factors decreased G* sin δ°.

Evaluation of the effect of rubber waste particles on the rheological and mechanical properties of cementitious materials for 3D printing

The use of 3D printing for cementitious materials is an increasingly viable option technically, economically, and environmentally for civil construction, generating a lower amount of waste. This work aims to evaluate the technical feasibility of using rubber as a fine aggregate in 3D printing mortars and its impact on its rheological and mechanical properties. Tests of compressive and flexural strength, flow-table, rheology and squeeze-flow were conducted to evaluate their fresh and hardened state properties. The total substitution of natural sand for rubber increased the rheological properties of dynamic yield stress (318–479.3 Pa), static yield stress (1604.1–1760.1 Pa) and plastic viscosity (4.15 Pa.s to 5.03 Pa.s). Lower compressive (19.9 MPa) and flexural (5.6 MPa) strengths were obtained for the mortar using rubber waste as aggregate. Also, the replacement of sand with rubber enhanced the anti-thixotropic behavior of 3D printing mortars.

Synthesizing dielectric nanocomposites from recycling rubber waste and agricultural silica: exploring leakage current characteristics for advanced applications

Rubber waste, primarily from discarded tires, is emerging as a significant environmental challenge. As the world produces 1.5 billion tires annually, this creates a vast amount of non-degradable waste. This often results in these tires accumulating in landfills or being burned, both of which pose severe environmental threats. Recognizing this issue, researchers have turned their focus to innovative recycling techniques. One such method involves transforming rubber waste into valuable composites. They are doing this by combining rubber with agricultural silica wastes, such as rice husk ash. This amalgamation results in the creation of environmentally-friendly dielectric materials suitable for electronic and electrical applications. Epoxy resin forms the base of this composite matrix. When supplemented with waste-derived nanofillers, the resin exhibits improved heat conductivity and mechanical resilience. These enhanced nanocomposite insulators have proven superior to their pure epoxy counterparts. The study also delved into insulator designs, evaluating various fin types to optimize high-voltage insulation. For dry environments, Isolator C with its unique fractal fins stood out, while for wet conditions, Isolator B’s serrated fins were ideal. This groundbreaking work showcases that rubber waste, when combined with agricultural by- products, can lead to sustainable advancements in the electronics sector.

Thermomechanical devulcanization of butyl rubber using twin-screw extruder: Process parameters, viscoelastic and compatibility properties

Thermomechanical devulcanization of butyl rubber (BR1), bromobutyl rubber (BR2) vulcanizates, both prepared in laboratory, and a waste commercial butyl rubber (BR3) using a twin-screw extruder is reported. The commercial butyl rubber vulcanizate (BR3) was used as a tire curing bladder and the waste rubber received from a tire manufacturing company. The devulcanization process was carried out at various barrel temperatures and screw speeds (40, 80 and 120 r/min). The lowest sol fraction was obtained for devulcanized waste commercial butyl rubber (D-BR3). According to Horikx theory, devulcanized butyl rubber (D-BR1) presented mainly crosslink breakup while devulcanized bromobutyl rubber (D-BR2) and devulcanized waste commercial butyl rubber (D-BR3) showed a mixture of main chain and crosslink scission. As cure rheographs at 190°C indicated, the addition of devulcanized rubbers to the corresponding virgin ones influenced both scorch and optimal cure times. The tensile properties of devulcanized/virgin rubber blends changed depending on the blend type and virgin rubber. The stress relaxation experiment revealed that the addition of devulcanized rubber to virgin one mostly influenced short relaxation times and also decreased G0. BR1/D-BR3 blends exhibited higher elastic component than BR1/D-BR1 and BR2/D-BR2 samples. The Han plots revealed higher compatibility for BR2/D-BR2 blends.

Performance and VOCs emission inhibition of high-content waste rubber powder modified asphalt and its mixture

ABSTRACT The high-content waste rubber powder (WRP)-modified asphalt (WRMA) has poor storage stability and tends to produce many volatile organic compounds (VOCs). This study aimed to research the influence of incorporating high-content WRP on the performance enhancement and VOCs emission of asphalt and its mixtures. The storage stability, rheological properties and cracking resistance of WRMA were tested. Further, the high and low-temperature properties of WRMA mixtures were evaluated. Additionally, the VOCs emission characteristics of WRMA mixtures were analysed . The results indicate that activated WRP has good compatibility with asphalt. The high-content of WRP can significantly enhance the high-temperature rheological properties and low temperature cracking resistance of asphalt binder, and the addition of nanometre calcium carbonate (B3) adsorbent can further enhance the physicochemical properties of asphalt binder. Moreover, compared with 70# asphalt mixture, the dynamic stability of WRMA mixture increases by about 50%, and the immersion residual stability and freeze–thaw splitting strength values increase by 6.34% and 5.98%, respectively. In addition, the B3 adsorbent can significantly reduce the VOCs emission from WRMA mixtures. The corresponding conclusions could provide guidance for the large-scale application of high-content WRMA mixtures and promote cleaner and greener products.

Enhancing performance of rubber mortar and water pollutant capture via fast and facile modification of recycled waste rubber particles

A fast, facile and highly efficient approach was developed in this study for the modification of recycled rubber particles (RP) into modified rubber particles (RP-TA-Fe3+). The incorporation of RP-TA-Fe3+ in cement-based materials effectively counteracted the detrimental effects typically associated with rubber. The TA-Fe3+ metal phenolic network proficiently impeded the leaching of heavy metal ions from the modified rubber and also effectively adsorbed cationic pollutants (MB and Cu2+) from water. The experimental results revealed that the rubber mortar containing RP-TA-Fe3+ exhibited reduced porosity and significantly improved flexural and compressive strength compared to the rubber mortar containing RP. Furthermore, the incorporation of RP-TA-Fe3+ into cement-based materials markedly enhanced their adsorption capabilities for MB and Cu2+.

A Decade Review of Research Trends Using Waste Materials in the Building and Construction Industry: A Pathway towards a Circular Economy

The construction industry is among the most prominent contributors to global resource consumption, waste production, and greenhouse gas emissions. A pivotal step toward mitigating these sectoral impacts lies in the adoption of a circular production and consumption system. The use of alternative waste materials can mitigate landfill accumulation and the associated detrimental environmental effects. To highlight unconventional materials, this study began with a bibliometric assessment via a bibliography analyzis software called “Bibliometrix” (version 4.1.3). The outputs from the analyzis can assist in identifying research trends, gaps in literature and benchmark research performance. The search engine used for sourcing publications was Scopus, using the main criteria as “Waste materials used in building and construction”. The time-period analysed was from 2013 to 2023. The results included publications obtained in journal articles, book chapters and conference proceedings. The assessment reviewed 6238 documents from 1482 sources. The results revealed an array of waste materials; however, rubber, textiles, and ceramics had a significant reduction in research attention. Rubber waste presents promising opportunities in civil concrete construction methods. The preparatory steps of textile fibres in composite materials are frequently disregarded, resulting in structural issues for the end-product. Obstacles persist in ceramic technology due to the absence of transparency, primarily because industry entities closely safeguard proprietary information. While sustainability research often emphasizes emissions, practical trials commonly revolve around integrating materials into current systems. A more comprehensive approach, contemplating the complete lifecycle of materials, could provide deeper insights into fostering sustainable construction practices. Researchers can use these findings when determining trends, research gaps, and future research directions.

Experimental and application of waste rubber low‐temperature green regeneration through ultrasound‐assisted method

AbstractCombining a traditional mixer and a custom‐built ultrasonic generator, low‐temperature green regeneration of waste rubber was realized. Through orthogonal experiments, the optimal process parameters for the low‐temperature green regeneration through the ultrasound‐assisted (LTGRTUA) method were explored. Results showed that the self‐developed reclaimed rubber exhibited the best performance under the following conditions: rotor speed of 70 rpm, regeneration temperature of 85°C, ultrasonic power of 700 W, and ultrasonic loading time of 240 s. Additionally, the bond‐breaking types of the reclaimed rubber were evaluated through the measurements of sol fraction and desulfurization rate, as well as by using the Horikx curve. The self‐developed reclaimed rubber showed better retention of the main chain structure of waste rubber compared to the commercially reclaimed rubber which was prepared by the traditional vulcanization tank high‐temperature regeneration (TVTHTR) method. Moreover, blending experiments were conducted, in which different proportions of the reclaimed rubber replaced natural rubber (NR) for the purpose of producing tread rubber for radial tires. Performance tests of the final products revealed that the self‐developed reclaimed rubber performed better than commercially reclaimed rubber, which provides an effective basis for the subsequent industrial application and promotion.Highlights Low‐temperature green regeneration of waste rubber was realized by the LTGRTUA method. The main chain structure of waste rubber is well preserved by the LTGRTUA method. The self‐developed reclaimed rubber has better properties and industrial application prospects.

Assessment of the effect of different pulping by-products on enhancing the reuse of rubber waste in producing of cement-mortar

This work deals with avoiding the pollution risks from paper pulping liquors and rubber wastes that result from routine disposal tools; moreover, finding an approach to minimize the drawback of incorporating the rubber waste in weakening the strength of building materials. In this respect, pulping black liquors (BLs) is assessed as a treating agent for rubber waste and substituting the water in cement mortar formulation. The assessment was achieved by testing the mechanical properties, water resistance (reduction in water absorption and dimensional change against water), and morphology. The results showed that all BLs from different pulping agents, used in mixtures with water, provided improvements in both strength and water resistance properties. Kraft black liquor is most effective in providing improvements in compressive strength and flexural strength, as well as resistance to water absorption and change in dimension after exposure to water for 24 h, where the improvements were 688.2 %, 494.3 %, 27 %, and 65.3 %, respectively. It is interesting to note that this investigated route provided improvements in the impact resistance property of mortar. This last property is essential for minimizing accidents on the highway.

Recycling of landfill waste tyre in construction materials: Durability of concrete made with chipped rubber

The goal of current research is to study the effect of waste tyre as a replacement for coarse aggregate at high levels in concrete for non-structural applications to address one of the serious environmental concerns. To reach this aim, waste rubber in a size range of 10–15 mm which needs less energy and cost for grinding compared to fine rubber was used. The total volume of coarse aggregate was substituted by rubber at the rates of 25%, 50%, 60%, 70% and 80%. Mechanical properties were studied through compressive and flexural strength and hardened density tests. Moreover, durability was comprehensively investigated via water absorption, drying shrinkage, electrical resistivity, chloride migration, carbonation resistance and resistance against acid attack tests. Sound absorption performance of different mixes at low and high frequencies were also compared to monitor the impact of rubber content. The results indicated that by the addition of rubber mechanical properties reduced, nevertheless, durability improved. Using rubber enhances the concrete ductility and reduces the density making it appropriate for lightweight concrete. The chloride migration coefficient was reduced up to 80% and electrical resistivity increased up to 87%, by using 80% rubber. Besides, rubberised concrete developed in this research demonstrated superior functional advantages over plain concrete in terms of acoustic performance and sustainability. Despite having lower strength by using rubber in concrete, rubberised concrete made with high content of cost-effective coarse rubber particle is appropriate for non-structural usages particularly in regions where either possibility of aggressive environment is a concern or noise attenuation is critical.

Dynamic properties of frozen rubber-reinforced expansive soils under confining pressure

In recent years, waste rubber has been increasingly utilized to enhance the performance of expansive soil foundations. This study aims to investigate the influence of rubber powder on the dynamic characteristics of frozen rubber-reinforced expansive soils (RRES) in permafrost regions. Temperature-controlled dynamic triaxial tests were conducted on RRES samples, varying rubber content, freezing temperatures, and confining pressures. The key findings are as follows: (1) A modified Hardin model with freezing temperature and rubber content as correction factors was established, which was verified to be useful for describing the dynamic stress-strain relationship. (2) Under the confining pressure, the dynamic shear modulus decreases with increasing rubber content. When the rubber content changes from 5% to 10%, the dynamic shear modulus decreases by about 20 MPa; the change becomes less obvious after the content exceeds 20%, and the RRES tends to show the characteristics of rubber. (3) As the rubber content increases, the damping ratio rises and shows the phenomenon of increasing and then decreasing with increasing confining pressure, and reaching a maximum at 0.4 MPa. (4) A prediction model for the maximum dynamic shear modulus with rubber content, freezing temperature and confining pressure is proposed.

Optimization of the composition of polyvinyl chloride based composite materials with rubber matrices and fly ash additions respectively

The main objective of this research was to analyze the possibilities of using rubber waste (reclaimed rubber and rubber powder), polyvinyl chloride (PVC), and fly ash (FA) to create composite materials with high performance. Composite materials were manufactured and tested, with the proportion of waste gradually increasing from 50 to 150 parts per hundred rubber (phr). These composite materials underwent testing for both structural homogeneity and physical-mechanical properties. The research included scanning electron microscopy (SEM) analysis and thermogravimetric analysis (TGA and DTGA). Additionally, we examined the behavior of the composite materials during artificial aging and conducted a topography analysis of the surface layer of the test samples. The research results demonstrated that composite materials with excellent structural homogeneity can be obtained, along with an opportunity to improve the surface layer topography by optimizing the composition of these composite materials. Furthermore, the presence of a coupling agent of the KWQ-EL type was found to contribute to better material homogeneity. Coupling agent KWQ-EL has a composition based on hexadecyltrimethoxysilane (HDS). It was also observed that incorporating both PVC and FA into the composite materials influenced the kinetics of the processes during TGA (DTGA) analysis. Additionally, optimizing the proportion of FA and PVC led to an enhancement in the surface layer's topography.In conclusion, this research has shown that sustainable composite materials, which are economically, socially, and environmentally viable, can be successfully produced, boasting excellent performance characteristics.

Evaluation on the characteristics of homogeneous catalytic hydrothermal gasification of waste rubber based on ReaxFF-MD simulation

Massive waste tires unrecycled will pose a significant threat to the urban environment. Hydrothermal gasification (HTG) is a promising technology converting polymer wastes into H2-rich syngas. The homogeneous catalytic hydrothermal gasification behavior of natural rubber (NR) and styrene-butadiene rubber (SBR) was estimated based on reactive force field molecular dynamics (ReaxFF-MD). KOH had the highest catalytic performance in enhancing the degradation efficiency (22.5 %) and H2 yield (27.4 %) in HTG of NR, and K2CO3 demonstrated the most optimal alkaline catalyst for SBR to enhance the degradation efficiency (27.2 %) and H2 yield (37.9 %). K2CO3 loading with 6 wt% manifested the optimum amount for lifting DE and H2 yield in HTG of SBR, while 10 wt% K2CO3 loading represented the best effect for lifting DE (26.5 %) and H2 yield (42.6 %) in HTG of NR. The activation energy of SBR in HTG was about 259 kJ/mol, which was about 72 kJ/mol higher than that of NR. With 6 wt% K2CO3, the activation energy of SBR and NR in HTG decreased to about 143 kJ/mol and 122 kJ/mol, respectively. The present work could provide essential theoretical support and fundamental data for the application of the homogeneous catalysts in HTG recycling of waste rubber materials.

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.