Ultra-high Compressive Strength Research Articles

Mechanical, permeability, and optical properties of concrete integrating light-transmitting materials with high contents and large diameters

ABSTRACT The present study focuses on developing LTC panels with high light transmission efficiency by integrating optical fibers or Polymethyl Methacrylate (PMMA) rods at volumes of 10–30% into the concrete. This aims to enhance the percentage of light intensity transmitted through the LTC to approximately 30% from the light source, a significant improvement compared to most previous studies where it was below 10%. Various configurations of these materials, differing in diameter and volume, were tested for their effects on mechanical strength, permeability, and optical properties. Unlike most previous studies using optical fibers smaller than 2.0 mm, the findings indicate that using optical fibers or PMMA rods with larger diameters improves the feasibility of casting LTC panels with ultra-high light transmission capacity and compressive strength above 40 MPa. The mechanical strength of LTC samples can be predicted based on the effective cross-section, excluding the area occupied by light-transmitting materials. The study also reveals that larger PMMA rods increase permeability due to weaker bonds with the surrounding concrete. Additionally, LTC panels can transmit colors and images without altering the original light source color, highlighting LTC’s potential for creative applications, such as smart traffic signal displays on pavements or unique architectural designs.

On novel Ni-rich phase formed during aging of an additively manufactured ultra-high strength CoFeNi alloy

The precipitation mechanism of strengthening phase of a body-centered-cubic (BCC) structured CoFeNi multi-principal element alloy produced by additive manufacturing was studied by transmission electron microscopy (TEM) and atom probe tomography (APT). The hardness of CoFeNi alloy achieved the peak value of 554.79 ± 9.86 HV after aging for 160 h at 400 °C. The CoFeNi alloy exhibited an ultrahigh compressive yield strength and ultimate compressive strength up to 1.8 GPa and 2.3 GPa respectively, whilst maintains a strain of 18.9 %. The microstructure of the alloy exhibited nanoscale lamellar Ni-rich phase with high stability homogeneously distributed in BCC matrix after aging at 400 °C. The novel Ni-rich phase containing about 50 at. % Ni with a hexagonal structure is the mainly precipitation strengthening phase, and has coherent orientation relationship with the BCC matrix in the<101>bcc∥<112¯0>Niand 111bcc∥{0001}Ni. Based on the experimental results, the precipitation mechanisms of the Ni-rich phase were discussed in detail. The current work provides a possible new direction to design high-strength alloy by introducing the novel Ni-rich phase.

Environmental-friendly and fast production of ultra-strong phenolic aerogel composite with superior thermal insulation and ablative-resistance

There is an urgent need for developing “low-carbon” synthesis technology to prepare aerogel composites with both high mechanical strength and efficient thermal insulation for applications of modern aerospace and energy saving. Herein, we propose a strategy for fabricating lightweight phenolic aerogel composites with thick-united connected nano-structure and good aerogel-fiber interfacial compatibility. The specific micro-nano structure and optimized material synergism endow the aerogel composites with an ultrahigh tensile strength (12.84 ± 0.64 MPa), bending strength (24.69 ± 1.96 MPa) and compressive strength (1.7 ± 0.053 MPa under 5 % strain), as well as low thermal conductivity (0.0541 ± 0.0003 W/(m·K)). The aerogel composites behave excellent ablation-resistance under the flame of 1200 °C within 30 min and maintain a cold-side temperature of 56.07 °C without any shape change. The rigid-flexible comminated aerogel composites open up a new technical track for developing lightweight thermal protective composites with high strength, toughness, and efficient thermal insulation demanded in extreme environments.

Development on Self-Compacting Concrete using GGBS

Self-Compacting Concrete (SCC) is a special type of concrete which is capable of flowing into the formwork, without segregation, to fill uniformly and completely every corner of it by its own weight without any application of vibration or other energy during placing. SSC has ultrahigh compressive strength. SSC is made to reduce time efficiency and help to minimize the number of labor required because that can flow and compact by itself. Materials required for SSC are cement, fine aggregate, super plasticizer course aggregate, water and admixtures.

Ultrastrong and Deformable Aluminum-Based Composite Nanolaminates with Transformable Binary Intergranular Films.

Nanostructured metals with conventional grain boundaries or interfaces exhibit high strength yet usually poor ductility. Here we report an interface engineering strategy that breaks the strength-ductility dilemma via externally incorporating graphene oxide at lamella boundaries of aluminum (Al) nanolaminates. By forming the binary intergranular films where graphene oxide was sandwiched between two amorphous alumina layers, the Al-based composite nanolaminates achieved ultrahigh compressive strength (over 1 GPa) while retaining excellent plastic deformability. Complementing experimental results with molecular dynamics simulation efforts, the ultrahigh strength was interpreted by the strong blocking effect of the binary intergranular films on dislocation nucleation and propagation, and the excellent plasticity was found to originate from the stress/strain-induced crystalline-to-amorphous transition of graphene oxide and the synergistic deformation between Al nanolamellas and the binary intergranular films.

Ultra-high-performance graphene-based bulk materials strengthened by Y-type connection structure

The strategic design and assembly of bulk graphene materials represent a pivotal advancement for harnessing the inherent properties of graphene in practical applications. However, fabricating high-strength graphene-based bulk materials from graphene powders presents a significant challenge, primarily due to interlayer slippage between the graphene layers. Here, a unique Y-type connection structure was found in few-layer graphene synthesized by self-propagating high-temperature synthesis (SHS) and subsequently retained in graphene-based bulk materials prepared by spark plasma sintering (SPS) process. The Y-type connection structure and defect-induced linkages serve to cross-link the graphene-based bulk materials. Consequently, the bulk material exhibited an ultra-high compressive strength, reaching 2.14 GPa, supported by Molecular dynamics (MD) simulations which demonstrated that the Y-type connection structure increases the shear modulus and the load transfer rate. The Y-type connection structure plays a vital role in reinforcing the strength of graphene-based bulk materials, offering valuable insights for the microstructural design and property augmentation of other graphene-derived materials. Besides it’s ultra-high compressive strength, the graphene-based bulk material also performs a low thermal expansion coefficient (0.5 × 10−6 K−1), high electrical conductivity (1.47 × 105 S·m−1) and exceptional EMI shielding capability.

Ultra-high strength ZTA ceramic foams with large amounts of intragranular structures resulting from dual-phase sol

A creative way to overcome the general problem of high-porosity ceramic foams with low intensity has been proposed here. For the first time, zirconia toughened alumina (ZTA) ceramic foams with a large number of intragranular structures have been prepared by particle-stabilized foams using boehmite sol and ZrO2 sol as raw materials. The grain boundary mobility of alumina in ceramic foams is much higher than that of zirconia due to the extremely high sintering activity of the boehmite nanoparticles, and then a typical intragranular structure of alumina grains wrapping around zirconia grains is formed. Based on the strengthening effects of intragranular zirconia grains, the as-prepared ZTA foams have excellent mechanical properties, with ultra-high compressive strength of 10.3–88.0 MPa and high porosity of 91.0–79.1 %. This paper provides a novel strategy for the preparation of high-performance ceramic foams.

Green strategy based on supercritical-fluid foaming for fabricating rigid microcellular thermoplastic polyimide foams with ultrahigh compressive strength

Thermosetting polyimide (PI) foams (PIFs) are usually synthesized through chemical foaming; however, this approach is environmentally toxic, and it is difficult to regulate the cell structure, remold the foam, and increase the foam compressive strength. The development of microcellular PIFs with ultrahigh compressive strength and high volume expansion ratio remains a challenge. Herein, thermoplastic PI with a branched structure and flexible ether bonds was synthesized through solution polymerization, and microcellular thermoplastic PIFs (TPIFs) with ultrahigh strength were fabricated via supercritical-carbon-dioxide foaming using 2,4,6-triamino pyrimidine (TAP) as a chain-extender monomer. Subsequently, a lattice model of a closed tetrakaidecahedral cell was used to clarify the relation between the foam compressive strength and polymer cell structure. Experimental results indicate that the optimal thermal imidization temperature is 230 °C and that the resulting branched structure considerably improves viscoelasticity, flame retardancy, and foaming performance. A TAP content of 0.75 g results in branched-structure TPIFs with a mean cell size of 16.8 μm. Notably, at high temperatures and pressures, the compressive strength of TPIFs with 0.75 g TAP is more than nine times of that of TPIFs without TAP. Increasing the TAP content beyond 0.75 g results in a crosslinked structure. Backward differentiation shows that TPIF compression is constant at 0.14–0.18 in the [0,0,1] lattice direction. The proposed physical foaming method is environment-friendly and can sustainably produce TPIFs with a high volume expansion ratio, an adjustable microcellular structure, and outstanding mechanical properties.

Ultrastrong and High Thermal Insulating Porous High-Entropy Ceramics up to 2000°C.

High mechanical load-carrying capability and thermal insulating performance are crucial to thermal-insulation materials under extreme conditions. However, these features are often difficult to achieve simultaneously in conventional porous ceramics. Here, for the first time, it is reported a multiscale structure design and fast fabrication of 9-cation porous high-entropy diboride ceramics via an ultrafast high-temperature synthesis technique that can lead to exceptional mechanical load-bearing capability and high thermal insulation performance. With the construction of multiscale structures involving ultrafine pores at the microscale, high-quality interfaces between building blocks at the nanoscale, and severe lattice distortion at the atomic scale, the materials with an ≈50% porosity exhibit an ultrahigh compressive strength of up to ≈337MPa at room temperature and a thermal conductivity as low as ≈0.76W m-1 K-1. More importantly, they demonstrate exceptional thermal stability, with merely ≈2.4% volume shrinkage after 2000°C annealing. They also show an ultrahigh compressive strength of ≈690MPa up to 2000°C, displaying a ductile compressive behavior. The excellent mechanical and thermal insulating properties offer an attractive material for reliable thermal insulation under extreme conditions.

Ultrahigh compressive strength and heat resistance of polystyrene/polyphenylene oxide foams of supercritical carbon dioxide foaming

AbstractPolystyrene (PS) foam materials are lightweight, but suffer from poor compressive strength and heat resistance, among other problems, which limit their application. Herein, a method for preparing PS foam with high compressive strength and high heat resistance using supercritical CO2 is proposed. PS/polyphenylene oxide (PPO) blends were prepared using a corotating intermeshing twin‐screw extruder. The results showed that PPO exhibited excellent molecular‐level compatibility with PS, which substantially improved mechanical properties and heat resistance of PS. Foam samples of PS/PPO blends with the same expansion ratio were prepared via batch foaming experiments, and the compressive strength of different foams was determined at different temperatures. At room temperature, the compressive strength of the PS/PPO‐30% foam increased by 173% compared with pure PS foam. As the testing temperature increased from 30 to 120°C, the compressive strength of pure PS foams decreased rapidly. Nevertheless, PS/PPO foams maintained high compressive strength at high temperatures.

Continuous surface cap model for ultra-high-performance concrete under static and low strain rate loadings: Calibration, experiment, and simulation

The ultra-high compressive strength and ductile tensile behavior of ultra-high-performance concrete (UHPC) make it promising in the application of civil and crashworthy facilities. Although numerous experimental studies have been conducted to investigate the performance of UHPC, studies on the methods for simulating the behavior of UHPC are few. In this paper, an overview of widely used constitutive models of concrete-like materials in hydrocode was presented first, and then a comprehensive calibration of the continuous cap surface (CSC) model was performed to simulate the mechanical behavior of UHPC under static and low strain rate loadings. Four groups of parameters: (1) failure surface parameters; (2) cap and hardening parameters; (c) damage parameters; and (4) strain rate parameters were systematically calibrated via extensive available material test data of UHPC with uniaxial compressive strength ranging from 101 MPa to 238 MPa. A calculation method was proposed to address the inconsistency of existing conclusions regarding the fracture energy of UHPC, which significantly affects the modeling of UHPC damage. Moreover, a method was proposed to convert the engineering uniaxial tensile strain of UHPC to the true uniaxial tensile strain, and so does the tensile fracture energy of UHPC. To validate the accuracy of the calibrated CSC model in simulating the behavior of UHPC under static loading, uniaxial tension and compression tests of UHPC samples and three-point bending tests of steel-UHPC-steel composite beams were conducted and simulated. Existing triaxial compression tests of UHPC cylinders were simulated to validate the accuracy of the calibrated CSC under confinement. Moreover, low-velocity impact tests of UHPC columns were simulated to further validate the reliability of the calibrated CSC model to capture the structural behavior of UHPC members under low strain rate loading. It was found that the calibrated CSC model showed excellence in simulating the material properties of UHPC and the structural behavior of UHPC members under static and low strain rate loadings.

Microstructure and mechanical properties of L12-strengthened CoFeMnNiMo0.2Alx high-entropy alloys

Developing alloys with excellent strength-ductility combination is urged desirable for advanced structural application. However, it still remains challenging in spite of years' efforts. Face centered cubic (FCC) high-entropy alloys (HEAs) commonly exhibit superb ductility. However, the low strength and hardness would limit the development of the FCC-structured materials. Here, the FCC + L12 + BCC structured CoFeMnNiMo0.2Alx were designed and prepared. The CoFeMnNiMo0.2Al0.5 HEA displays outstanding compressive properties, whose ultra-high compressive strength is 1900 MPa and the fracture strain is 39.6%. The nano-hardness of the CoFeMnNiMo0.2Al0.5 HEA is nearly 8 GPa. Moreover, the relationship between phase evolution, mechanical property, strengthening mechanism, and Mo, Al concentration are systematically discussed. These findings will shed light on exploring novel HEA systems with high performance for future usage.

Bridging graphene sheets to ultra-high-performance graphene-based bulk materials via Si-C bonding and Y-type carbon structure

Graphene is the strongest material ever identified. However, the fabrication of graphene-based bulk materials from graphene powders presents a significant challenge. Here, a new strategy to fabricate high performance graphene based bulk materials by introducing silicon nanoparticle is proposed. Consequently, ultra-high compressive strength and high flexural strength are achieved, measuring as high as 1102 MPa and 455 MPa, respectively. The compressive strength at the microscale even reaches a remarkable 5.17 GPa. The superior strength of the bulk material is primarily attributed to the Y-type carbon structure and Si-C bonds. The Y-type carbon structures in graphene, produced by the self-propagating high-temperature synthesis (SHS) method, and the Si-C covalent bonds formed at the interface between graphene and SiC contribute to a tight linkage of graphene sheets, thereby preventing slippage of graphene sheets. In addition, the microstructure evolution process of Si-SHS-graphene bulk material is clarified. With the introduction of silicon nanoparticles, the oxidation resistance of graphene based bulk materials is substantially improved, the weight loss is around 6% after oxidized at 1000 °C. This study carries extensive implications for understanding the impact of Y-type carbon structures and the effect of Si-C bonds in graphene-based bulk materials.

Intelligent data-driven compressive strength prediction and optimization of reactive powder concrete using multiple ensemble-based machine learning approach

In recent years reactive powder concrete (RPC), also known as ultrahigh-performance concrete, emerged as one of the most efficient building materials due to its ultrahigh compressive strength (usually greater than 150 MPa), ductility, and durability. The existing literature presents a wealth of experimental data exploring the intricate interactions among the various components within RPC mixtures, emphasizing the requirement for a potent and efficient model to optimize, simulate, and enrich the understanding of RPC mixture characteristics. This study presents a notable attribute utilizing a multilayer stacked model that harnesses the potential to harmoniously seamlessly integrate and synergize various machine learning (ML) algorithms. An extensive dataset from reliable resources in the literature was used to develop a new ML model for predicting the compressive strength of RPC. It was found that there is a strong positive correlation between the RPC’s compressive strength and the dosage of silica fume, fiber dosage, and age of concrete. In contrast, water content and dosage of GGBFS were observed to have a low correlation with the compressive strength of the RPC. The most significant features were age, fiber dosage, silica fume content, cement content, HRWR dosage, fine aggregate content, and water content. Further, in this study, predictive efficacy identifies the stacking algorithm as optimal, followed by XGBoost, RF|ETR, and KNN. Notably, R2 strengths vary: stacking achieves 0.96, XGB sustains 0.954, RF and ETR hold 0.95, while KNN reaches 0.77.

Symbiotically engineered crystalline-amorphous nanostructure in a strong-yet-stable Al alloy with large twinning-induced plasticity

High performance structural materials with combinations of excellent yet often mutually exclusive properties such as high yield strength, ductility and thermal stability are primarily accessed by synthesizing heterogeneous microstructures. Age-hardened Al alloys with hierarchical nanoprecipitates manifest a good combination of strength and ductility compared to fully amorphous Al alloys, however their thermal stability is in general low, stem from the fast-diffusion element-driven coarsening of nanoprecipitates at elevated temperature. Utilizing the sluggish-diffusion element Cr in the Al matrix, we propose a novel strategy of architecting symbiotically crystalline-amorphous nanostructure (CANS) endowed with self-assembled Cr segregation at crystalline/amorphous interfaces, to develop thermally stable, ultrastrong and ductile Al alloys. The symbiotic CANS-AlCr alloys with homogeneous twinning-induced plasticity of ∼15% strains at room temperature have ultrahigh compressive yield strength of ∼1.75 GPa and outstanding thermal stability up to ∼623 K, simultaneously superior to the parent nanocrystalline and amorphous Al alloys. The interfacial Cr segregation not only promotes twinning-induced plasticity of crystals but also triggers dynamic elemental partitioning between interfaces and amorphous nanolayers, which is critical to their thermodynamic and mechanical stabilization of symbiotic CANS-AlCr alloys. Our strategy advances efficient creation of hierarchical nanostructure and offers a facile route that is regulated across atomic and nanoscopic scales to achieve desirable materials with diverse-yet-precise performances.

Cartilage-like protein hydrogels engineered via entanglement.

Load-bearing tissues, such as muscle and cartilage, exhibit high elasticity, high toughness and fast recovery, but have different stiffness (with cartilage being significantly stiffer than muscle)1-8. Muscle achieves its toughness through finely controlled forced domain unfolding-refolding in the muscle protein titin, whereas articular cartilage achieves its high stiffness and toughness through an entangled network comprising collagen and proteoglycans. Advancements in protein mechanics and engineering have made it possible to engineer titin-mimetic elastomeric proteins and soft protein biomaterials thereof to mimic the passive elasticity of muscle9-11. However, it is more challenging to engineer highly stiff and tough protein biomaterials to mimic stiff tissues such as cartilage, or develop stiff synthetic matrices for cartilage stem and progenitor cell differentiation12. Here we report the use of chain entanglements to significantly stiffen protein-based hydrogels without compromising their toughness. By introducing chain entanglements13 into the hydrogel network made of folded elastomeric proteins, we are able to engineer highly stiff and tough protein hydrogels, which seamlessly combine mutually incompatible mechanical properties, including high stiffness, high toughness, fast recovery and ultrahigh compressive strength, effectively converting soft protein biomaterials into stiff and tough materials exhibiting mechanical properties close to those of cartilage. Our study provides a general route towards engineering protein-based, stiff and tough biomaterials, which will find applications in biomedical engineering, such as osteochondral defect repair, and material sciences and engineering.

Ultrahigh strength-ductility of nanocrystalline Cr2AlC coating under micropillar compression

MAX phases gain increasing attention as protective coatings due to superior anti-corrosion and oxidation resistance for harsh high-temperature applications. However, the lower strength and strength-ductility trade-off in bulk MAX phases still pose an enormous challenge arising from the large ratio of c/a lattice parameters and less activated slips. Here, nanocrystalline Cr2AlC coating with high-purity was fabricated using a hybrid arc/sputtering technique with subsequent thermal annealing. Cylindrical micropillar compression test was conducted by FIB milling to identify the mechanical properties of the coating under deformation. The stress-strain curves demonstrated that an ultrahigh compressive strength of 5.3 GPa with strain beyond 12.5% was surprisingly achieved for Cr2AlC coating, which was 5 times larger than all the reported bulk MAX phases before. Specifically, the extraordinary ductility at RT is ascribed to the synergy of the fundamental basal slip, additional non-basal slip and deformation twinning stimulated by ultra-refinement effect of nano-crystalline Cr2AlC coating.

A novel seismic strengthening method for RC frames: Precast ultra-high performance concrete braces

A novel bracing method to strengthen the seismic behavior of reinforced concrete (RC) frames was developed in the study. The brace was made using steel reinforced ultra-high performance concrete (UHPC). UHPC is a class of tensile strain-hardening cementitious composites and has ultra-high compressive strength of greater than 120 MPa. To utilize the capacity of the UHPC brace prior to the onset of major inelastic response of the RC frame, a design method for the UHPC brace was established. In the developed strengthening method, the in-situ construction process was simplified by conveniently installing the precast UHPC brace using the UHPC connections that was constructed in-situ to link the UHPC brace to the frame. The performance of the UHPC bracing method was evaluated using cyclic loading tests on two frame specimens, i.e., a bare RC frame and a UHPC brace-strengthened RC frame. The test results showed that the UHPC brace effectively enhanced the initial stiffness, peak strength, and energy dissipation capacity of the original frame. Moreover, it successfully preserved the capacity of the columns when the UHPC brace was active without magnifying the shear demand in the columns. As a result, the strengthening method allowed the original columns to utilize their full force resisting capacity after the capacity of the UHPC brace was depleted. In addition to the experimental study, an analytical model, which was derived based on equilibrium, compatibility, and suitable material constitutive laws, was developed to reasonably evaluate the load-displacement response of RC frames strengthened with UHPC braces.

Experimental investigation on the progressive collapse resistance of UHPC-RC composite beam-column structures

An innovative technique for enhancing the structural anti-progressive collapse performance was proposed by utilizing ultra-high-performance concrete (UHPC) in reinforced concrete (RC) structures. To this end, three UHPC-RC specimens with different UHPC application locations or thicknesses and one RC specimen were tested based on an alternative path method to investigate the improvement effect and mechanical mechanism of UHPC. The experiments demonstrated that the UHPC-RC structures experienced three resistance mechanisms, including flexural action (FA), compressive arch action (CAA), and catenary action (CA). Moreover, UHPC at the beam top or bottom significantly improved the FA and CAA capacities. UHPC at the beam top delayed the first rupture of steel bars. Additionally, the numerical simulation was performed for eight UHPC-RC specimens, and the influence of UHPC location and thickness on structural robustness is further discussed. Based on the experimental and numerical results, seven enhancing mechanisms by UHPC are revealed, namely ultra-high compressive strength, good tensile properties, excellent toughness, large elastic modulus, fine and dense multi-slit cracking characteristics, interface constraint effect on cracks, and passive confinement effect on ordinary concrete. Finally, based on the research findings, the suggestion that UHPC at the beam bottom (not more than 40% of the beam height) is superior to that at the beam top for the improvement of structural robustness is propounded.

Microstructure characterization and mechanical properties of AB-typed high-entropy intermetallics with high strength and thermal stability

In this work, we developed a new system of AB-typed high-entropy intermetallics (HEIs) based on CoHf-like B2 crystal structure. The microstructure and mechanical properties of the targeted CoxCuxTiZrHf alloys were detailedly investigated. With the increase of CoCu content, the alloys’ structure changes from multiphase to single phase. In particular, the multi-principal Co1.7Cu1.7TiZrHf alloy with single B2 crystal structure shows ultrahigh compressive yield strength of 1.77 Gpa and fracture strength of 2.15 Gpa at room temperature, as well as high elastic strain limit of approximately 1.5%. Moreover, it can maintain single-phase B2 structure and high strength after annealing at 900 °C.