Ceramic Aggregate Research Articles

Ceramic Aggregate Material Formulated with MSWI Fly Ash and Fuel Ash for Use as Filter Media

This study aimed to develop a novel filtering medium ceramic aggregate prepared using municipal solid waste incineration (MSWI) fly ash and the fuel ash from coal power plants, together with small amounts of silicon carbide foaming agent and magnesia flux as additives. For the manufacturing process, the dosage of MSWI fly ash and the sintering temperature were optimized to maximize the performance of the resulting materials. Leaching test results indicated that the heavy metal concentrations in the ceramic aggregate were significantly below the limits proposed by GB5085.3-2007, demonstrating its safety for wastewater treatment. The ammonia nitrogen removal efficiency was assessed, and the removal rate of the developed ceramic aggregate was found to be 16.4% higher than that of zeolite, making it comparable to commercial ceramic aggregate. Scanning electron microscopy and X-ray diffractometer analyses were conducted on the ceramic aggregates. The ammonia-nitrogen-removing mechanism, attributed to adsorption and ion exchange, is discussed based on the microstructural analysis results.

Influence of vacuum infiltration on mechanical properties of polymer concrete filled with lightweight ceramic aggregates

In this paper, the influence of vacuum infiltration of lightweight ceramic aggregates as fillers in polymeric concretes was described. In the first stage of the investigation, a set of ceramic aggregates with a high open porosity of about 27% was produced on the basis of industrial wastes. Ceramic aggregates with a size of 2 to 4 mm, hereinafter referred to as granules, were produced using contaminated glass cullet waste and coal shale. The effectiveness of granule infiltration with epoxy resin in the production of polymer concrete with high mechanical strength and relatively low mass compared to traditional concrete was discussed. The compressive strength of polymer concrete, where the aggregates were infiltrated with resin, is 87 MPa, and the polymer concrete, in which the vacuum infiltration process was not used, reaches a compressive strength of approximately 42 MPa. The resulting concrete, due to its density, is classified as a lightweight high-strength concrete.

Fire-resistance behavior of concrete columns produced with recycled ceramic and silica aggregates: An experimental and numerical approach

This article aims to fully assess the fire-resistance behavior of fiber-reinforced concrete (FRC) columns made with recycled ceramic aggregates when subjected to severe thermal loading. In addition, the effects of fiber reinforcements and ceramic recycled aggregates (RAs) on the thermal behavior of concrete columns were addressed and compared with that of the conventional silica-made concrete columns. In this regard, twelve small-scale FRC columns containing recycled ceramic and silica aggregates are prepared and placed in a heating chamber for 90 min. Next, the columns were axially loaded until failure, and variations in compressive stress and axial strain of the specimens were measured, aiming to capture the thermal effects on the load-carrying capacity, axial strain, and failure modes of the concrete columns. The specimens were exposed to high temperatures of 20 °C, 600 °C, and 1000 °C according to ISO 834 Fire Standard, and were tested in humid and dry environmental conditions. Moreover, the failure modes of the columns (e.g., concrete spalling, crack pattern, etc.) are presented in terms of macroscopic imaging. In addition, in-depth analyses of the effects of fibers (steel and polypropylene) and moisture content on the thermal behavior of concrete columns is addresses utilizing scanning electronic microscope (SEM) technique. The results indicate that below the temperature of 600 °C, the axial behavior of the FRC columns with silica and ceramic aggregate are similar. However, as the temperature rises, the reduction in axial load-bearing capacity of the columns with silica aggregates is higher than that of the columns with ceramic aggregates. Also, it was observed that the environmental humidity negatively affects the overall fire-resisting behavior of the columns. Furthermore, a numerical procedure is presented in ABAQUS to estimate the behavior of FRC columns subjected to thermal loading and validated using the experimental results.

Microstructure change and mechanical property variation of high performance concrete with recycled ceramic aggregate as internal curing material under different environmental temperatures

High performance concrete (HPC) is broadly utilised in various building environmentbecause of its excellent properties. Recycled ceramic aggregate (RCA) is employed as internal curing material for HPC in this study, which introduces extra water to maintain internal humidity and support continuous hydration. In particular, the effect of temperature on the curing efficiency of RCA is investigated for the first time. The physical properties and chemical compositions of RCA are firstly analysed. The microstructure and pore distribution of HPC with various RCA replacement ratios affected by three different curing temperatures are then investigated. Finally, the autogenous shrinkage, splitting tensile strength and compressive strength of HPC are tested at various ages. The experimental results show that a higher curing temperature will generate more micro-cracks and larger porosity inside the HPC. The increase in curing temperature will enhance the early strength of HPC, but the mechanical properties will decrease with the growth of curing time. Besides, the increase in curing temperature will cause more significant autogenous shrinkage.

Studying Thermal and Mechanical Properties of Recycled Concrete by Using Ceramic Aggregate

Ceramic aggregate has the characteristics of light weight, heat insulation, and low cost, and recycled aggregate is a type of green material that realizes the re-crushing of construction waste. This paper studied the impact of replacing natural coarse aggregate with ceramic aggregate and natural sand with recycled fine aggregate, on the physical, mechanical, and thermal properties of concrete. Recycled fine aggregate was used to completely replace natural sand. A total of five concrete mixes (including a reference mix) were prepared with different levels of ceramic aggregate (0%, 30%, 50%, 70%, 100%). Density, compressive strength, thermal conductivity, and thermal inertia index were measured to evaluate the performance of each mixture, and ceramic concrete board and hollow blocks were designed for testing the thermal properties. Results of testing show that density, strength, and thermal performance are interrelated. The smaller the density, the lower the strength, and it indicates that ceramic aggregate has a negative influence on strength in concrete. Meanwhile, the smaller the density, the higher the thermal resistance, and the addition of ceramic aggregate can improve the thermal insulation of concrete. The mechanical and thermal properties are both affected by the ceramic replacement ratio. Ceramic aggregate improves the thermal properties of recycled concrete, and the negative influence of ceramic aggregate on compressive strength can be controlled by the replacement ratio of aggregate in concrete. Based on the overall comparison and analysis, a mix with 50% ceramic aggregate shows relatively better strength and thermal insulation compared to other mixes. The use of ceramic aggregate in combination with recycled fine aggregate can effectively reduce the environmental pollution and make an economical substitute for their natural counterparts.

Pozzolanic Reaction of Recycled Cementitious and Red Ceramic-Waste Aggregates with Hydrated Lime for Pavement Base Layer

Cement addition and pozzolanic reaction in construction and demolition waste recycled aggregates can stabilize the base of pavements chemically. A way to control and explore the maximum benefits of it is necessary. This study establishes a mix between recycled cementitious and red ceramic-waste aggregates with hydrated lime to enhance pozzolanic reactivity in the material and achieve the best mechanical properties compared with those of a portland cement or recycled concrete aggregate itself pavement base layers. Chemical tests (Chapelle and thermogravimetry), physical tests (grain size distribution, density), and mechanical tests [unconfined compressive strength (UCS) and resilient modulus (RM)] were conducted. The increase of hydrates in the fine fraction of the mixes and the recycled aggregate itself correlated with the resulting increase in UCS and RM. The limited contribution of the self-cementing reaction of recycled cementitious aggregates was quantified, resulting in an UCS of 1 MPa and RM of 1,000 MPa. The pozzolanic reaction of cementitious and red ceramic aggregates with hydrated lime achieved an UCS of 8.4 MPa and RM of 2,800 MPa, values closer to those achieved by a portland cement stabilized pavement base (5.4 MPa and 4,500 MPa, respectively).

Evaluating the Influence of Carbon Fiber on the Mechanical Characteristics and Electrical Conductivity of Roller-Compacted Concrete Containing Waste Ceramic Aggregates Exposed to Freeze-Thaw Cycling

Traditional methods of removing snow and ice from pavements using chemicals are combined with mechanical removal that involves a lot of manpower, advanced machinery, chemicals that are harmful to the environment, and damage to pavements. Furthermore, annually, large quantities of ceramic materials become waste due to their fragile nature during processing, transport, and installation, and their accumulation in the nature has brought about environmental and health-related concerns. Therefore, the study aims to investigate the effect of using waste ceramic as a replacement for fine aggregate in roller compacted concrete (RCC) and the application of carbon fiber to improve the mechanical properties and electrical conductivity of RCC. To achieve this goal, several tests such as compressive strength, indirect tensile strength, electrical resistance, chloride ion penetration, specific gravity, and skid resistance tests were carried out on the fabricated samples before and after freeze-thaw cycling exposure. The experimental results illustrated that replacing waste ceramics with fine-grained aggregate increased the compressive strength and tensile strength of RCC. Furthermore, carbon fiber increased tensile strength but had no noticeable influence on compressive strength. Freeze-thaw conditioning led to a reduction in the compressive and tensile strength regardless of the aggregate type and carbon fiber utilization. In the samples containing waste ceramic aggregate, the electrical conductivity was reduced, and by adding carbon fiber, its electrical conductivity was increased. Exposure to freeze-thaw cycling resulted in an increase in electrical resistance and the passing charge. Waste ceramic incorporation created a similar mixture in terms of skid resistance, while in contrast, the carbon fiber slightly reduced the skid resistance. In addition, freeze-thaw conditioning resulted in an increase in the skid resistance. Besides, in this study, kernelized support vector regression (KSVR) and radial bias function (RBF) neural network models were proposed to estimate the indirect tensile strength (ITS) and compressive strength (CS) values. The results showed that both models have high performance in estimating these values, but RBF was a more efficient model.

Safe environmentally friendly reuse of red mud modified phosphogypsum composite cementitious material

Phosphogypsum (PG) and red mud (RM) are solid wastes produced by chemical enterprises when producing phosphoric acid and alumina. Therefore, the harmless utilization of them is of great significance to the environment. This study explored the effect of the synergistic activity enhancement effect of solid waste on the macroscopic properties and internal microstructure of RMPS, and explored the optimal ratio of composite cementitious materials and ceramic aggregate. Based on the synergistic enhanced activation effect of multiple solid wastes, it is necessary to evaluate the human health and ecological security risks of heavy metals in the prepared red mud modified phosphogypsum system (RMPS) to ensure the environmental safety of the product. The results showed that the optimum ratio of PG, RM, FA, quicklime and cement in the preparation of cementitious materials by RMPS were 46.9 %, 26.5 %, 4.1 %, 12.2 % and 10.2 %, respectively. Under the water-binder ratio of 0.33, the 14 days compressive strength of the mortar specimen could reach 19.0 MPa, the 14 days flexural strength could reach 4.3 MPa. The optimum ratios of PG, RM, FA, quicklime, cement and river sand in the prepared ceramic aggregate were 36.5 %, 20.6 %, 19.5 %, 3.2 %, 7.9 % and 22.2 %, respectively. The raw materials were mixed and prepared into ceramsite, which was placed in a drying oven and cured at 20 °C for 14 days. The 14 days cylinder compressive strength of ceramic aggregate could reach 2.4 MPa, which met the standard requirements of “Lightweight aggregates and its test method-Part 1: Lightweight aggregates” (GB/T 17431.1–2010). With 10 % cementitious materials content, the road water-stable layer materials was prepared by using ceramic aggregate to replace 4.75 mm crushed stone in equal volume. The 7 days unconfined compression strength of the cylinder specimen was 4.7 MPa, and the 7 days splitting tensile strength was 0.6 MPa, which met the strength requirements of the highway water-stable layer in the “Specification for design of highway asphalt pavement” (JTG D50-2017). The risk assessment of heavy metals in RMPS was carried out. The single factor index indicates that more attention should be paid to Hg and Cd. The geo-accumulation index showed that Hg in the system had a high environmental pollution risk. At the same time, in accordance with the result of human health risk assessment, Cr in RMPS can cause carcinogenic effects through oral intake and need to be controlled. Finally, based on the risk assessment model constructed in this study, the limit values of RMPS applied to three heavy metals in road water stability layer were given and the safety and environmental protection control model of heavy metals in RMPS was proposed.

Effect of recycled ceramic aggregate on hydration heat and permeability of high performance concrete

The application of recycled ceramic aggregate (RCA) in concrete construction has attracted increasing attention recently. In this study, the effect of RCA on the exothermic reaction in HPC is investigated, which reveals the mechanism underlying the role RCA plays in regulating hydration heat output and permeability of HPC for the first time. The porosities and the pore distributions of three types of RCA are investigated through microscopic test, and the internal structures of HPC with different types of RCA are also analysed. Hydration heat test is then carried out to measure the maximum temperature obtained during exothermic process and the time at peak temperature. Finally, chloride ion penetration experiment is conducted to further investigate the effect of RCA on the permeability of HPC. It is found that RCA can lower the temperature during exothermic reaction and prolong the cement hydration process, while the permeability of HPC is increased.

Design of a non‐shrinking silica fume high‐performance concrete with recycled ceramic tile aggregate

AbstractInternal curing (IC) process introduced via a water‐entraining agent using lightweight and porous aggregate has become an essential component in designing high and ultra‐high‐performance concrete (HPC/UHPC). This paper presents experimental results demonstrating the effectiveness of using recycled ceramic tile aggregates (RCTA) derived from waste ceramic tiles as an IC agent for high‐performance structural elements. Previous studies by the author have confirmed the efficiency of both the pre‐saturated recycled porous ceramic coarse aggregate (RPCA) as an IC and shrinkage compensating agents in mitigating autogenous shrinkage and the induced internal self‐stress in HPC mixtures. The main objective of this study is to investigate the effect of two different curing systems (internal curing using the waste ceramic aggregate combined with shrinkage compensating agents) on silica fume (SF) HPC behavior. The shrinkage compensating agents include a combination of shrinkage‐reducing agent (R) and expansive additive (E). The influence of this combined ternary curing system on the mechanical properties, including compressive, flexural, and splitting tensile strengths, modulus of elasticity, autogenous shrinkage, and internal self‐induced tensile stress, were investigated. The obtained results indicate a substantial reduction in the autogenous shrinkage strains magnitude and, consequently, the internal self‐induced tensile stress in the HPC mixtures designed with these two curing systems. It was also found that this combination of the two curing systems resulting in a hybrid curing system, performs much better than the single incorporation of shrinkage‐compensating agents. Besides, a long‐term strengths improvement was recorded for mixtures designed with the RPCA. Incorporating recycled aggregate in the design and production of HPC could further promote concrete sustainability by reducing the amount of virgin extracted non‐renewable minerals, reducing the energy required to extract and process natural aggregates and the CO2 generated, and also reducing solid waste materials disposal.

Mechanical properties and flow characteristics of dolomite-based porous supports for catalysts using different pore-forming agents

Three kinds of pore-forming agents (corn flour, starch, and biochar) were selected to prepare dolomite-based porous ceramic catalyst carriers with good mechanical properties. Pore-forming agents occupy space within preformed agglomerates, such that after the pyrolysis and sintering have been completed there are spaces within the resulting ceramic material. Porous ceramic samples prepared with biochar exhibited high apparent porosity and water absorption. By contrast, the apparent porosity of the porous ceramic samples prepared with starch as the pore-forming agent was low. When the ratio of the dolomite to quartz sand in the ceramic aggregate was changed from 4:6 to 3:7, the change of the apparent porosity of the porous ceramic samples made with starch as a pore-forming agent was very small, with high bulk density and compressive strength. Compared with corn flour and biochar, starch was less suitable as a pore-forming agent for porous ceramics. The apparent porosity and water absorption of the porous ceramics prepared with biochar as a pore-forming agent decreased slightly. But its bulk density and thermal conductivity were increased. This is mainly attributable to the fact that biochar is lighter, but it performs well in terms of mechanical strength and thermal conductivity.

Lightweight Concrete with Agglomerated Aggregate Based on Fly Ash

The production of lightweight concrete is mainly carried out in the traditional way using lightweight ceramic aggregates. The aim of the pilot research was to verify the possibility of producing lightweight concrete based on artificial aggregate in the form of agglomerated aggregate from high temperature fly ash. A representative of such aggregate is the artificial aggregate referred to as aploporite. This aggregate is characterised by comparable grain strength to ceramic aggregates but, on the other hand, has a relatively high absorption rate of up to 30 %. Concrete formulations with up to 50% replacement of natural aggregate by aploporite have been proposed in order to achieve the volumetric weights characteristic of lightweight concrete. The results obtained confirmed that it is possible to produce lightweight concrete with this aggregate and to achieve strengths comparable to those of ordinary concrete.

The Use of Waste Ceramic Optimal Concrete for a Cleaner and Sustainable Environment - A Case Study of Mechanical Properties-

The present study aims to find out the optimal use of ceramic powder and ceramic aggregate (both fine and coarse) as a possible substitute for Ordinary Portland Cement (OPC 43 grade) and natural aggregate (fine and coarse), respectively, in concrete, where focused on investigating the mechanical properties of waste ceramic concrete. The performance of this modified concrete was evaluated in terms of Compressive Strength (CS), Tensile Strength (TS), Flexural Strength (FS), and Combined Flexural and Torsional strength (FTS) obtained based on various experimental tests conducted on a total of 192 samples (48 cubes, 48 cylinders, 96 beams). The test results showed that ceramic waste material as a partial replacement for natural aggregate, cement, and fine aggregate provides better performance in terms of CS, TS, and FTS at optimal percentages- 20% ceramic aggregate, 10% ceramic powder, and 10% ceramic fine aggregate (Fineness Modulus 2.2) respectively in M25 grade concrete. Using ceramic waste as a partial replacement to prepare concrete has a lot of benefits from the economic, environmental, and technological point of view. Moreover, it offers a possibility for improving concrete's durability, which is vital.

Reactive ceramic aggregates in mortars from ancient water infrastructure serving Rome and Pompeii

Throughout the ancient Roman empire, crushed ceramics were commonly used as additives for surface mortars that were in continuous or frequent contact with freshwater. Inspired by the long-term durability of these materials and employing multi-scale correlative characterization approaches that combine electron microscopy and Raman microspectroscopy-based techniques, we demonstrate the role of these ceramics as a long-term source of reactive aluminosilicates. By mapping the spatial distribution of both pozzolanic and post-pozzolanic phases, our analyses reveal the presence of a hybrid binder consisting of cementitious hydrates and calcite at the interface between the ceramics and the surrounding matrix and provide evidence of post-pozzolanic densification and the filling of pores and cracks. The analysis of a wide range of ancient Roman structures used for the distribution and storage of freshwater demonstrates the ubiquity of ceramic additives for these applications and points to the opportunity for creating more robust modern analogs of these ancient concrete formulations. • Ancient Roman concretes used ceramic fragments as a source of reactive aluminosilicates • C-A-S-H is formed at the ceramic-cement interface, further strengthening these materials • These results pave the way for developing more durable modern concrete formulations Seymour et al. describe how the ancient Romans used crushed ceramics as additives in their mortars and concretes and provide insights into their underlying millennial-scale durability. Analysis of a wide range of ancient freshwater-related mortars points to the opportunity for creating more robust modern analogs of these ancient concrete formulations.

Effects of electrolytic manganese residue (EMR) to co‐sintering mechanism of ceramic aggregate

AbstractThe influences of co‐sintering temperature on the physical properties of EMR (electrolytic manganese residue) ceramic aggregate were investigated over the gradient of co‐sintering by EMR, CFA (coal fly ash), and P (perlite) that were used as raw materials. Seven EMR samples were prepared to sinter at different temperatures that were decided by the data of a thermal mass spectrometer, and four ceramic aggregate embryos were sintered at 1120, 1140, 1160, and 1180°C. The mechanisms of co‐sintering temperature action on performance were determined by means of X‐ray diffraction and scanning electron microscopy with energy‐dispersive X‐ray spectroscopy. The optimal temperature of 1160°C and the temperature increment lead to an enhancement of cylinder compressive strength and a damping of 1‐h water absorption, softening coefficient, and grain shape coefficient was discovered. Gypsum of EMR dissolved and exhausted gas during co‐sintering resulted in CaO. The crystalline transformation of wollastonite and gehlenite produced anorthite, which boosts the strength of aggregate and the content of anorthite, was proportional to the co‐sintering temperature and the pressure strength of cylinder. The liquid phase of “overfiring”‐coated crystal contributed to the further improvement of strength, but the aggregate sphere deformation generated a reduction of comprehensive performance. The formation of bustamite calcian in co‐sintered ceramic aggregate realized the solidification of Mn, and the solidification rate of leaching toxicity test was 99.92%, and the absence of radioactivity was demonstrated.

Eco-friendly geopolymer concrete based on metakaolin and ceramics sanitaryware wastes

The sanitary ceramics industry generates huge quantities of wastes notwithstanding all the efforts made to improve the manufacturing process. The aim of the present work is to investigate the potential reuse of sanitary ceramics wastes as an aggregate to manufacture metakaolin based geopolymer concrete. The effect of granulometry and added quantity of SCW on the properties of metakaolin based geopolymer matrix was assessed via physical, mechanical and microstructural properties. the results indicate that the developed concretes exhibit higher mechanical performance compared to conventional concretes and to reference geopolymer. It was also shown that the increase in aggregate particle size had a significant influence on the compressive strength as well as the density and porosity. The microstructure in the interfacial transition zone (ITZ) between the recycled ceramic aggregate and the paste was observed to be more compact.

Investigation on the comprehensive durability and interface properties of coloured ultra-thin pavement overlay

Coloured pavement provides benefits for improving functionality and safety in pavement infrastructure. In this investigation, a coloured ultra-thin pavement overlay was prepared with a resin-based binder and artificial coloured ceramic aggregates. The overlays were prepared in various binder thicknesses (0.8 mm, 1.2 mm, and 1.6 mm) and aggregate spreading ratios (50 %, 75 %, and 100 %). The specimens were experimentally tested with a wheel abrasion tester followed by the analysis of apparent colour loss, rutting depth, mass loss, and skid resistance in accordance with a proposed comprehensive durability evaluation method. The colour-cooling performance was evaluated with the sunlight simulation test. In addition, the interface properties were tested based on the flexural toughness test, pull-off test, and shear test. The comprehensive durability evaluation results indicated that coloured overlay with 1.2 mm binder depth and 75 % aggregate spreading ratio had the highest durability score among all samples. The sunlight simulation test results verified the positive cooling effect of the coloured overlay on the pavement structure. The bottom-up cracking resistance based on the flexural toughness test was also improved with overlays by comparing that with specimens without covering. The pull-off test and shear test results illustrated that the interface adhesion was correlated to environmental temperature and binder thickness. This study provided a comprehensive durability scoring method for coloured ultra-thin functional overlays, and the optimized material compositions enhanced the durability and interface adhesion, which could be utilized for future field applications of coloured ultra-thin functional overlays and contribute to infrastructure sustainability.

Study on the sintering mechanism and properties of porous ceramics prepared by silicon carbide abrasive particles with multi-mineral sintering additives and silica sols

Reducing the sintering temperature of SiC ceramics while maintaining performance has been a significant challenge. This study proposes the preparation of SiC porous ceramics at lower sintering temperatures using industrial-grade SiC abrasives, instead of expensive high purity SiC ceramic particles, as ceramic aggregates by combining two process routes, namely liquid-phase sintering and additive doping, with industrial silica sol as the liquid-phase binder and three common minerals, namely kaolin, talc, and bentonite, as sintering additives. SiC ceramic precast blanks were first prepared by a semi-solid injection moulding process. The reasonable SiC sintering temperature was determined to be 1400 °C by studying the effect of sintering temperature on the component composition and microscopic morphology of the blanks. Then, SiC porous ceramics with macroscopic and microscopic pore structures were successfully prepared using an organic foam impregnation-high temperature sintering process, in which the maximum compressive load was 210.2 N at a porosity of 72.66%. Finally, the rationality of this process route was determined, which shows that this technology can reduce the complexity and production cost with cheaper raw materials and lower sintering temperature without atmosphere protection.

Heat-resistant concretes containing waste carbon fibers from the sailing industry and recycled ceramic aggregates

The article describes a new model of the production of heat-resistant concrete in which waste recycled materials were used. The aim of the work was to compose a composite that would have high strength parameters despite being loaded with rapidly rising temperatures. The simulation of such conditions was aimed at analyzing the possibility of using this composite in tunnel construction.Aluminous cement was used as the binder for the concrete. The aggregate used was ceramic waste from industrial sanitary ceramic waste. Carbon fibers from the production of carbon fiber sailing equipment were used as an additive to modify the properties of the concrete. The comparative modifier of the composite was polypropylene fibers normally used in this type of applications. All concretes were tested for basic properties such as consistency, bulk density, water absorption, compressive and tensile strength without and after annealing. The test samples were also subjected to microscopic examination.All the composites studied were characterized by similar values of consistency, density and absorbability. In the aspect of testing the composites not annealed in the case of analysis of tensile strength, the addition of all types of fibers was positive. In the case of testing of non-annealed composites in the aspect of compressive strength, the effect of the addition on this feature was small. The differences in the tested strengths were up to 2%. The mentioned parameters tested after annealing indicated a significant role played by the additives. The most favorable parameters were evaluated for composites with waste carbon fibers. The value of tensile strength of samples with carbon fiber additives after annealing was 3.1 times higher than that of samples with comparative polypropylene fibers. The investigated compressive strength value for the composite with the recycled additive was 30% higher than that for the composites with the traditional additive. Microscopic analyses explained the reasons of the changes occurring in the composites.The research allowed to recommend the use of waste carbon fibers in the production of refractory composites resistant to thermal shocks. The properties evaluated in the research work also allowed to propose the use of this type of composites in concrete tunnel construction.

Flexural Behavior of Reinforced Concrete Beams under Instantaneous Loading: Effects of Recycled Ceramic as Cement and Aggregates Replacement

The flexural behavior of five reinforced concrete beams containing recycled ceramic as cement and aggregate replacement subjected to a monotonic static load up to failure was studied. A full-scale, four-point load test was conducted on these beams for 28 days. The experimental results were compared with the conventional concrete as a control specimen. The cross-section and effective span of these beams were (160 × 200 mm) and 2200 mm, respectively. The data recorded during the tests were the ultimate load at failure, steel-reinforcement bar strain, the strain of concrete, cracking history, and mode of failure. The beam containing 100% recycled aggregates displayed an ultimate load of up to 99% of the control beam specimen. In addition, the first crack load was almost similar for both specimens (about 14 kN). The deflection of the beam composed of 100% of the recycled aggregates was reduced by 43% compared to the control specimen. Regardless of the recycled ceramic aggregates ratio, quantities such as service, yield, and ultimate load of the proposed beams exhibited a comparable trend. It was asserted that the ceramic wastes might be of potential use in producing high-performance concrete needed by the structural industry. It might be an effective strategy to decrease the pressure on the environment, thus reducing the amount of natural resources usage.