Mechanical Property Tests Research Articles

Failure analysis of a large coal chemical reactor exhibiting bulging and cracking

Reactors represent the core components of coal chemical plants. Reactor failures can lead to significant operational hurdles, substantial financial losses, and potential casualties. Given these critical implications of reactor failures, thorough failure analyses of failed reactors are essential. This study investigated a failure incident involving bulging and cracking of a large coal chemical plant reactor. The failure analysis relied on several techniques, including macroscopic inspection, wall thickness measurement, mechanical property testing, hardness testing, metallographic analysis, and scanning electron microscopy analysis. The investigation confirmed that the failure of the reactor was caused by local overheating, which triggered high-temperature short-term creep, ultimately leading to bulging and cracking. To identify the factors responsible for this local overheating, a process analysis involving flow field and structural numerical simulations under abnormal working conditions was performed. The results of the flow field simulation, combined with field investigation data, revealed that the local overheating resulted from deposition or clogging of the distributor disk. Additionally, the extent of overheating was determined through the structural numerical simulation. In this paper, physical and chemical inspection, numerical modeling, and other means are comprehensively used to deduce the failure position through numerical simulation, to find out the failure reason, and to deduce the temperature range of failure. Overall, we hope that the results of this comprehensive failure analysis will provide valuable and experiential insights into the operation and maintenance of coal chemical plant reactors.

66kv Modular Composite Material Emergency Repair Tower Simulation of Mechanical Performance and Experimental Study of Components

Abstract This paper details the design and performance evaluation of a 66kV modular insulated tower, aimed at enhancing the resilience and operational flexibility of power systems in extreme environments. The tower employs advanced composite materials, providing excellent mechanical strength. The design addresses various conditions, including line breaks, high wind speeds, and icing scenarios. Finite element analysis conducted using ANSYS software showed that the safety factor for the pole body is 2.14, indicating that the designed tower meets the safety factor requirements. Additionally, its excellent mechanical properties have been verified through mechanical property tests. The modular design facilitates rapid assembly and disassembly as needed across different contexts, significantly improving the efficiency and flexibility of emergency repair work, thus offering considerable benefits for power grid upgrades, maintenance, and disaster recovery. In summary, the 66kV modular insulated tower demonstrates its broad potential applications within modern power systems. The results of this study provide valuable references for power system design, especially in seeking more efficient and adaptable transmission repair solutions.

Study on road performance of asphalt mixture based on surface modification of coal gangue

In order to solve the problem of coal gangue environmental pollution and the shortage of aggregate resources in road engineering, this paper studies the feasibility of using waste coal gangue as coarse aggregate of asphalt mixture. Through the physical and mechanical properties test, the difference between coal gangue and natural aggregate was compared and analyzed. The surface modification and strengthening treatment of coal gangue aggregate was carried out by using methyl sodium silicate solution, and the best modification scheme was determined. The influence of different content and surface modification on the road performance of coal gangue asphalt mixture was studied by laboratory test. With the help of scanning electron microscope test, the change characteristics of the microstructure of coal gangue asphalt mixture before and after surface modification were explored. The results show that although the indexes of coal gangue are inferior to those of natural aggregate, it can be used to prepare asphalt mixture within the scope of specification requirements. The modification effect of sodium methyl silicate solution with modification time of 6h is the best, which can significantly improve the water absorption, density and crushing value of coal gangue. When the content of coal gangue is controlled within 30%, the performance of asphalt mixture meets the requirements of the specification, and the amount of coal gangue in asphalt mixture can be increased after surface modification. After surface modification, the surface pores and cracks of coal gangue asphalt mixture are reduced, and the surface micro-damage under high temperature immersion and freeze-thaw cycle conditions is improved.

Influence of Transportation Exhaust and Acid Rain on the Strength of Concrete Bridges and Possible Solutions to Reduce Harmful Effects

The quality control and safety assessment of existing bridge decks as a result of integrated field tests are presented in this work as a systematic technique. The aim of this research is to determine an effective approach for directly protecting concrete bridges exposed to transportation exhaust and acid rain. Mechanical property, permeability, chloride effect and abrasion resistance tests at days 28, 91, 180, 360 and 540 of the concrete specimen were used to evaluate the concrete strength. The results demonstrated the efficacy of the nanomortar, insulating paints and epoxy resin in improving concrete characteristics. In terms of water permeability, the specimen with 0% epoxy resin performed poorly compared with the control. Fuzrthermore, compared with the other combinations, the mixture with epoxy resin presented the lowest water permeability, followed by the mixtures with insulating paints and nanomortars. The specimen with epoxy resin obtained the lowest water penetration (0 mm). The specimen with insulating paint obtained the lowest water penetration (216 mm) at 91 days (with effect). This ratio can be explained by the reduction in permeability of 68.37% with respect to the control. The specimen with nanomortar obtained the lowest water penetration (14.5 mm) at 91 days, with effect.

The Recycling Use of Concrete Waste as Aggregate to Produce Different Types of Concrete

The present study depends on two types of concrete: the first and second samples belong to Portland cement with a high strength of 52.5 R, and ordinary Portland cement with a normal strength of 42.5 N, respectively. The physical tests for these two samples according to Iraqi Standard Specification No. 5 of 2019 were conducted. Whereas the third and fourth samples of concrete waste were taken from Mosul City and Al-Anbar Governorate. The concrete waste samples were broken into different-size particles as a fine and coarse aggregate using a mechanical crusher (Los Angeles). According to the Iraqi Standard Specification No. 45 (1984, the Physical and chemical tests for both fine and coarse natural aggregate and recycled concrete waste were conducted. The physical and mechanical results of the recycled aggregate testing samples were found to be within the limits of specifications, in which a reference concrete was made from the standard cement samples with natural aggregate for comparison. The natural aggregate was replaced with 100% recycled aggregate, and its behavior was studied through mechanical properties tests, including compressive strength, flexural resistance, and direct tensile resistance within 7 and 28 days. The results show a decrease in the compressive, flexural, and direct tensile strength in the subjected samples compared to the reference specimens. The study concluded that a 100% replacement ratio of coarse and fine recycled aggregate can be used successfully with different types of cement to obtain a new type of concrete that can be used in several engineering fields. The mechanical properties of the new concrete depend mainly on the type, class and quality of the natural cement even on the properties of the recycled aggregate.

Effect of agricultural wastes as sugar beet ash, sugarcane leaf ash, and sugarcane bagasse ash on UHPC properties

This research investigates the use of novel agricultural waste ash, such as sugar beet ash (SBA), as partial cement substitutes to produce high-performance and sustainable concrete. In addition to SBA, sugarcane leaf ash and sugarcane residue ash were used as partial cement substitutes at 10 %–50 % by weight. To evaluate the efficiency of the ash used, strength index tests were conducted at 7 and 28 days of age. To evaluate the performance of UHPC incorporating agricultural waste ash, 22 mixtures were implemented. Tests of workability, mechanical, and transport properties, as well as microstructure analysis of UHPC, were performed. In addition, the effect of high temperatures up to 800 °C on compressive strength (CS) was investigated. The experimental results indicated that incorporating agricultural waste as cement substitutes, including SBA, improved the mechanical properties, enhanced its workability, and reduced chloride penetration of UHPC. The mixture containing 10 % SBA showed a CS of 170.8 MPa compared to the reference mixture of 167.2 MPa at 28 days of age. Microstructure analysis revealed that incorporating agricultural waste reduced the pore size and created a denser UHPC structure, which contributed to the improvement of UHPC properties. The results demonstrate the technical feasibility of using SBA as cement substitutes alone or in combination with SLA or SCBA for UHPC production and its potential for wider applications in the construction industry.

Study on the properties of ground film paper prepared from lactic acid-modified cellulose

Abstract Lactic acid impregnated ground film paper was prepared using the method of lactic acid impregnation of raw paper. The physical properties, chemical composition, crystallinity, thermal stability, surface morphology of the paper, barrier properties, and light transmittance of the lactic acid paper were investigated using FT-IR, XRD, TGA, SEM, water vapor blocking, oxygen blocking, mechanical properties testing, and optical property testing. Results showed that at room temperature (20 °C), when lactic acid concentration was 100 %, reaction time was 48 h, and 100 °C high temperature drying prepared lactic acid paper, it exhibited superior performance: dry strength of 2.83 IkN/m, wet strength of 0.36 kN/m, Cobb value of 4.50 g/m2, tear of 359.42 mN, water vapor barrier of 693.46 g m−2 24 h−1, and oxygen barrier of 933.43 cm3 m−2 24 h−1. Degradation rate reached 22.94 % after two weeks of soil landfill.

Mechanical properties and energy evolution law of marble under the coupled effects of chemical corrosion and dry-wet cycles.

The main factors affecting the safety of underground structures are groundwater chemical corrosion and water level fluctuations. To investigate the mechanical properties of marble and the energy evolution pattern during the failure process under the coupled effects of chemical corrosion and dry-wet cycling, samples were subjected to 5, 10 and 20 cycles of dry-wet ageing in chemical solutions with pH values of 4, 7 and 10, respectively, followed by mechanical property testing. The energy evolution pattern during the failure process of the specimens was also studied. It was found that there is a strong correlation between number of dry-wet cycles and pH value of chemical solution. Chemical corrosion at the early stage of dry-wet cycling has the greatest effect on the deterioration of the rock. As the number of dry-wet cycles increases, the degree of corrosion in acidic solutions is most evident, with the uniaxial compressive strength and elastic modulus decreasing by 27.88% and 33.52% respectively, followed by alkaline solutions, and the degree of corrosion in neutral solutions is the lowest. In addition, dry-wet cycling and chemical corrosion lead to an increase in the internal pores of the rock samples and a decrease in the energy storage capacity. Nevertheless, the proportion of energy loss increases with the number of dry and wet cycles, with the proportion of energy loss in acidic media increasing from 35.61% to 41.63%, indicating that the plastic deformability of marble increases under the action of chemical corrosion and dry and wet cycles. The research results have certain guiding significance for the design, construction and maintenance reinforcement of underground structures under the conditions of chemical corrosion and dry-wet cycling.

Biodegradable antibacterial food packaging based on carboxymethyl cellulose from sugarcane bagasse/cassava starch/chitosan/gingerol extract stabilized silver nanoparticles (Gin-AgNPs) and vanillin as cross-linking agent

The increasing issue of plastic waste necessitates improved solutions, and biodegradable food packaging is a promising alternative to traditional plastic. In this study, we prepared packaging films using cassava starch (CV), chitosan (CT) and carboxymethyl cellulose (CMC), with glycerol as a plasticizer. However, these films require modifications to enhance their mechanical properties. Therefore, we modified the films by adding vanillin as the crosslinking agent and gingerol extract stabilized silver nanoparticles. The films were fabricated using the film-casting method and characterized by FTIR, XRD, SEM, TGA, mechanical property test, biodegradability test, anti-bacterial test and food packaging evaluation test. Among these films, CT/CV/V/CMC/Gin-AgNPs1 exhibited superior mechanical properties and demonstrated excellent anti-bacterial property both for gram-positive (S. aureus) and gram-negative (E. coli) bacteria and biodegradability, losing over 50% of its weight after 21 days of burial in soil and effectively preserved grapes at 4 °C for 21 days.

Study on the mechanism of waterborne polyurethane modified ultrafine ground calcium carbonate and its properties in polypropylene plastics

AbstractGround calcium carbonate (GCC) has the effect of reducing the incremental cost and improving the application performance as a plastic filler. In this study, waterborne polyurethane (WPU) was employed as a novel modifier for the wet modification of GCC. Polypropylene (PP)‐based composites incorporating GCC were then prepared for mechanical properties testing. The oil absorption value, wetting contact angle, and settling time in kerosene indicated that the modified GCC achieved an excellent modification effect with a WPU dosage of 2.0 wt%. The X‐ray Diffraction, Fourier Transform Infrared Spectroscopy, and X‐ray Photoelectron Spectroscopy results indicate that WPU was successfully coated on the surface of the GCC. SEM images revealed improved wettability and compatibility of GCC in the composites after modification. The mechanical tests showed that the GCC‐WPU/PP composites exhibited enhanced properties, including a flexural strength of 107 MPa, impact strength of 9.54 kJ/m2, tensile strength of 29.7 MPa, and an elongation at break of 30.9%.Highlights WPU was innovatively used as a modifier of GCC. An optimal modification effect was gained at the low dosage (2.0 wt%). GCC has excellent compatibility and wettability in PP composites. The obtained PP‐based composites have better mechanical properties. The study has the potential to apply GCC in plastics and other industries.

Assessing environmental impacts of various solvent-dissolution routes for the pelletization of mixed plastic waste

The vast majority of mixed plastic waste (MPW) does not degrade, thereby contributing to permanent environmental pollution. To address this, solvent-dissolution processes have been developed to recycle MPW into usable materials like blended pellets. This study evaluates five solvent-dissolution pathways, with a focus on mixed polyolefin, which constitutes about 60 % of MPW. The pathways explored include xylene, paraffin waxheptane, paraffin waxhexane, mineral oilheptane, and mineral oilhexane. Although paraffin wax and mineral oil are considered environmentally friendly, their recovery processes involve hexane or heptane, leading to higher energy use and carbon emissions. The xylene-based pathway, however, showed about four times lower energy consumption (48 MJ) and significantly reduced emissions (1.24 kg CO2 eq.) compared to fossil fuel-derived methods. In addition, mechanical property tests were conducted on the HD-PP blends which revealed a tensile modulus of 762 MPa and a tensile strength of 24 MPa, rendering them potentially advantageous for applications necessitating moderate elasticity and strength. Additionally, the study identifies dissolution and extrusion as the key stages affecting the life cycle assessment (LCA) and suggests powder production as a more cost-effective and sustainable alternative to pelletization, with lower carbon emissions. These findings offer valuable insights for improving MPW recycling through solvent-dissolution.

Experimental and Numerical Investigation on the Bearing Capacity of Axially Compressive Concrete-Filled Steel Tubular Columns with Local Corrosion

This study aims to examine the effects of local corrosion on the axial compression performance of concrete-filled steel tubular (CFST) members. Nineteen CFST short columns with local corrosion were designed and fabricated to undergo axial compression mechanical property tests, with the radial corrosion depth of the local corrosion area as the key test parameter. The failure mechanism and mechanical property change laws of CFST axial compression short columns with circumferential full corrosion at the ends and middle were studied. Combined with finite element modeling, the influence laws of the three-dimensional geometrical characteristics of the local corrosion zone, i.e., the axial length, the annular width and the radial depth, on the structural bearing performance were thoroughly explored and discussed. The results revealed that the main reason for the reduction in load-carrying capacity of circular CFST axial columns due to local corrosion is attributed to the reduction of the effective cross-sectional area of the steel tube in the corrosion area. When local corrosion occurs at different axial positions, the variation range of the bearing capacity of CFST columns is within 10%. Regarding the impact of the three dimensions of local corrosion on the axial load-carrying capacity of CFST, the radial corrosion depth was identified as the most influential factor, followed by the annular corrosion width, and finally by the axial corrosion length. When the axial corrosion length exceeds 20% of the specimen length, its further influence on the load-carrying capacity is considered limited. Finally, a practical calculation formula for the bearing capacity of locally corroded CFST columns is proposed. The predicted results of this formula fit well with the test results and can quickly estimate the remaining bearing capacity of the structure by measuring the geometric parameters of the local corrosion area, providing a reference for the assessment and maintenance of CFST structures.

A green and efficient method to prepare oleic acid–modified CaCO3/reHDPE composites

Industrial recycling of waste plastics frequently utilizes mechanical recovery and recycling. However, plastics recycled through mechanical recovery tend to have reduced properties, limiting their applications. In this study, modified calcium carbonate (OA-CaCO3) was prepared using different amounts of oleic acid (OA) (0.5, 1.0, and 2.0 wt%). Infrared spectroscopic characterization showed OA was successfully adsorbed on the CaCO3 surface. Particle size, micromorphology, oil absorption value, and activation tests indicated that CaCO3 modified with 1.0 wt% OA yielded optimal results. Melt blending 1.0 wt% OA-modified CaCO3 with recycled high-density polyethylene (reHDPE) produced composites. Scanning electron microscopy results showed OA modification enhanced interfacial compatibility between the two phases. Mechanical property tests revealed at high filling levels, the impact strength of OA-modified composites increased considerably, reaching 42.6 kJ/m2 with 40 wt% OA-CaCO3 filling. Melt flow rate test results showed that OA-modified composites had increased melt flow and modified processing properties. Filling OA-CaCO3 to compensate for reHDPE properties caused by mechanical recycling is essential to expand mechanical recycling applications in plastics recycling.

Crystallization, thermal, and compatibility performances of poly (butylene succinate) (PBS)/poly((R)‐3‐hydroxybutyrate‐co‐(R) 3‐hydroxyhexanoate) (PHBHHx) blends

AbstractBiodegradable materials provide protective properties comparable to conventional plastics while diminishing reliance on nonrenewable resources. Environmentally friendly polymer blends were prepared by melting poly(R)‐3‐hydroxybutyrate‐co‐(R)‐3‐hydroxyhexanoate) (PHBHHx) with poly (butylene succinate) (PBS). PBS was synthesized through esterification and polycondensation using 1,4‐butanediol and succinic acid, with tetrabutyltitanate as the catalyst. The PHBHHx is supplied by Bulepha®PHA Company of China, model number BP330. The effects of PHBHHx content on thermal behavior, compatibility, and thermal stability of PBS/PHBHHx blends were systematically investigated. Differential scanning calorimetry (DSC) results indicated that the addition of PHBHHx influenced the crystallization behavior, the crystallization temperature (Tc) of PBS decreased meanwhile, the crystallization half‐time of PBS is reduced to 1.5 min compared with neat PBS (5 min) after isothermal is crystallized at 95°C. Polarized Optical Microscopy (POM) images also revealed that crystallization rate accelerated in the blend with increasing PHBHHx content. Rheological and Scanning Electron Microscopy (SEM) analysis demonstrated that incorporating a significant content of PHBHHx reduced compatibility between PBS and PHBHHx. Mechanical property testing indicates that the addition of PHBHHx reduced the toughness of blends. Additionally, the addition of a small amount of PHBHHx imparts a higher crystallinity (56%) and heat resistance of the PBS/PHBHHx blends (78°C) was higher than neat PBS (74°C).Highlights Laboratory synthesis of high molecular weight PBS. Optimal ratios improved crystallinity and thermal stability of blends. A systematic study of the crystallization properties of blends.

A novel thermoplastic material: Pre‐polymerized PMMA liquid resin and continuous glass fiber‐reinforced composite initiated by benzoyl peroxide/N,N‐dimethylaniline

AbstractThermoplastic PMMA was rarely exploited in continuous fiber‐reinforced composites due to its viscous high‐temperature molten fluid as well as pessimistic wettability into fiber fabric. Redox‐active polymerization is a green route to develop a new liquid PMMA resin at room temperature to provide an in situ curing with the advantages of energy saving and consumption reduction. In this paper, BPO/DMA was adopted as a redox initiator pair, and the effect of MMA:BPO:DMA ratio on curing time, Mn, Tg, and mechanical properties of PMMA were systematically studied. When the ratio of MMA:BPO:DMA is 200:1.2:1, PMMA‐200 achieved optimistic mechanical properties at 20°C (tensile strength, 64.7 MPa; tensile modulus, 3352 MPa; bending strength, 125.3 MPa; bending modulus, 3023 MPa). Moreover, the mechanical properties were further improved at low temperatures. The maximum tensile strength and tensile modulus were up to 97.43 and 4297 MPa (−40°C) respectively. The tensile strength (0°, 1103 MPa; 90°, 52.3 MPa) and tensile modulus (0°, 47.5 GPa; 90°, 14.2 GPa) of glass‐fiber‐reinforced PMMA composite at 20°C were found to be comparable with epoxy resin‐based composites and even higher at lower temperature. In summary, redox‐initiated PMMA and its fiber‐reinforced composites are promising thermoplastic materials as new lightweight alternatives.Highlights Preparation method of PMMA resin and glass fiber composite. Research on the mechanical properties, molecular weight, glass transition temperature, curing time, etc. of PMMA resin. Testing of mechanical properties of PMMA glass fiber composites at room temperature and low temperature. Current applications and prospects of PMMA glass fiber composites.

A numerical simulation study on the characteristics of wrap shell lightweight aggregate concrete based on random aggregate model

It is a way to reuse solid waste by using dredged silt as raw material to prepare unburned wrap shell lightweight aggregates and replacing crushed stone aggregate to prepare unburned wrap shell lightweight aggregates concrete specimen. In order to understand the characteristics of wrap shell lightweight aggregates concrete, this paper adopts the method of combining laboratory test and numerical simulation to design the mix ratio test scheme of concrete specimens with different substitution rates of wrap shell aggregate (0 %, 25 %, 50 %, 75 %, 100 %), and conducts indoor mechanical properties test and numerical simulation simulation test on them, so as to obtain and analyze the mechanical properties and failure characteristics.The results show that:(1) The peak stress intensity of concrete specimens decreases linearly with the increase of the substitution rate of wrap shell aggregate.(2) The peak stress of concrete under different wrap shell round aggregate substitution rates is normally distributed, and the dispersion of peak strength decreases with the increase of wrap shell aggregate substitution rate. When the substitution rate is 0 %, the dispersion of peak strength is the largest.(3) Under the uniaxial compression simulation test, the failure mode of concrete specimens changes with the addition of the substitution rate of wrap shell aggregate. When the crack failure occurs, natural coarse aggregate with high strength is chosen to bypass, while when it comes to wrap shell aggregate with low strength, it is chosen to penetrate. With the continuous addition of round aggregate, the stress concentration phenomenon inside concrete can be effectively improved and the number of micro-cracks can be reduced.But at the same time, the penetration cracks gradually increase and gradually tend to be straight.The fractal dimension is negatively correlated with the compressive strength and positively correlated with the substitution rate of wrap shell aggregate.The above research can provide theoretical basis for the popularization of recycled concrete with wrap shell aggregate.

Synthesis of Gold Nanoparticles by Pulsed Laser Ablation and its Study Physical and Mechanical Properties

In this work, the pulsed laser ablation technique was used, which is considered a good and distinctive method. Gold nanoparticles (AuNP) were prepared using an Nd-YAG laser with specific parameters, wavelength 1064 nm, constant ablation energy 1000 mJ, frequency 1 Hz, and different number of pulses (300, 600, and 900 pulse/sec). Deionized water was used as the medium liquid. The purpose of this study was to examine the change in these parameters on AuNP using a variety of Xrd, FESEM, Uv-Vis, force-hardness, and compression measurements. The pure cubic crystal structure of gold nanoparticles was analyzed using XRD. Subsequent FESEM images (average diameters 78.07nm, 49.15nm, 37.67nm) indicate that the particles had highly spherical and quasi-spherical shapes. Using ultraviolet analysis, the absorption band of gold nanoparticles was found and the wavelength was (518, 519, 524) nanometers, respectively. There were three different power gaps (1.895, 2.005, and 2.084) eV. In addition, mechanical property tests were conducted, where 2 ml of gold nanoparticles were mixed with (3 grams) of traditional dental filling. The hardness value increased by (3%). The results also showed an increase in the stress and strain value and an increase in Young’s modulus. Hence, an increase in the compressive strength. This indicates that AuNP affects the mechanical properties and enhances their effectiveness.

Effect of cryogenic rolling on the microstructure and properties of C70250 copper alloy

The application of cryogenic rolling technology serves to enhance the strength of a material by increasing the density of dislocations and refining the grain size. However, a high density of dislocations can lead to a reduction in its ductility. In this study, cryogenic rolling at low strain followed by subsequent aging treatment at temperatures between 450 and 550 ℃ was employed to introduce deformation twins into C70250 Cu alloys, aiming to balance both strength and electrical conductivity. The microstructural evolution and property changes of the alloy were examined throughout the cryogenic rolling and aging process using SEM, TEM, XRD, and various mechanical and electrical property tests. The results indicate that alloys subjected to cryogenic rolling and aging exhibit significantly improved strength compared to those treated at room temperature. The introduction of twinning through cryogenic rolling significantly enhances the efficiency of dislocation multiplication during rolling. This high dislocation density facilitates the nucleation of precipitated phases during the subsequent aging process, leading to superior mechanical properties. Within the integrated cryogenic rolling and aging treatment, the precipitated phases, dislocations, and twin boundaries collectively exert a synergistic reinforcing effect, resulting in exceptional yield and tensile strengths, reaching up to 685 MPa and 744 MPa, respectively. The findings in this study contribute to the development of novel methods for fabricating high-strength, high-conductivity copper alloys.

INFLUENCE OF FIRECLAY GRANULES ON CALCIUM ALUMINATE CEMENT HYDRATION AND PROPERTIES AFTER FIRING

The article investigates the effect of granules, produced from dispersive fireclay using liquid glass as a binder, on the hydration process of calcium aluminate cement (CAC). Peculiarities of the hydration process were evaluated from the results of calorimetry, thermal analysis, XRD, SEM, and mechanical properties tests, as well as the relative viscosity of the cement pastes. It is determined that the granules are capable of entrapping water and releasing it later, shortening the incubation period and increasing the maximal heat release rate during the CAC crystallization stage and total cumulative heat as compared with the control samples with the same active cement part and containing dispersive fireclay particles, which are cement-inert. The redistribution of water due to granules’ addition results also in more hydrates C2AH8 and AH3 in CAC pastes containing granules than in those containing dispersive fireclay. Due to the reaction between the water solution containing dissolved cement minerals and sodium silicate film (dried liquid glass), the hydrogel-like phases form inside the granule during the hydration, which fill the gaps between the fireclay particles and after firing at 1100 °C form a glassy phase enveloping the fireclay particles and binding them to each other, providing the granule integrity and contributing to their strength. The specific structure formed due to the addition of fireclay granules does not change dramatically the density of the obtained composite, provides 7.4–18.5% higher strength after drying with 7.5–15% granule addition and ∼11% higher strength after sintering at 1100 °C with 5% granule addition (as compared with compositions containing dispersive fireclay). 30% granule addition can be considered as too much, causing significant strength loss.

Mechanical Properties Test and Failure Analysis of Composite Foam Sandwich Structure in Ramp-Down Zone

Mechanical Properties Test and Failure Analysis of Composite Foam Sandwich Structure in Ramp-Down Zone