Ultra-high Performance Cementitious Composites Research Articles

Dynamic behaviors of nickel coated carbon nanotubes reinforced ultra-high performance cementitious composites under high strain rate impact loading

Understanding the dynamic mechanical behaviors of materials is a prerequisite for reliably analyzing and predicting the dynamic response of structures, which is of great significance for transportation infrastructure and military engineering subjected to extreme loads, particularly dynamic loads at high strain rates. Nickel coated multi-walled carbon nanotubes (Ni-MWCNTs) show promise as a reinforcement to modify the dynamic mechanical behaviors of ultra-high performance cementitious composites (UHPCC). Because Ni-MWCNTs combine the high tensile strength and large aspect ratio characteristics of fibers with the nano effect of nanomaterials, as well as have excellent dispersibility due to the nickel plating on the CNTs’ surface, they effectively improve the dynamic mechanical properties of UHPCC under impact loading at high strain rates of about 100 s−1/300 s−1/500 s−1 and reduce the brittle damage degree of composites. The maximal increase in dynamic compressive strength and energy absorption capacity of UHPCC reaches 47.9% and 68.2%, respectively. This enhancement effect arises from that Ni-MWCNTs improve the microstructure and form multiple fine cracks, resulting in an increased energy consumption required for crack formation, propagation and coalescence. Additionally, the dynamic mechanical properties of Ni-MWCNTs reinforced UHPCC exhibit noticeable strain rate effects. Consequently, a strain rate-dependent logarithmic functional dynamic increase factor model and dynamic constitutive model of UHPCC filled with Ni-MWCNTs are modified herein for predicting and modeling the dynamic mechanical behaviors of composites.

Physio-chemical, mechanical and fracture analysis of ultra-high performance cementitious composite

The present research aims to develop cost-effective and environmentally friendly Ultra-High Performance Concrete (UHPC) composite using fly ash and quartz powder as a sustainable alternative to cement. The performance of various constituents is examined, and their influence on fresh and hardened properties is investigated for the optimum trial mix design. The results show that a cube compressive strength of 144 MPa was achieved with fly ash content of 20% and 10% quartz powder and other ingredients without any special heat treatment. Advanced characterization studies such as heat of hydration and X-ray diffraction analysis were performed to understand the performance of fly ash blended UHPC. Further, various fracture properties, such as fracture toughness, fracture energy, brittleness number, etc., were investigated considering geometrically similar notched beam specimens for UHPC mix with 1.5% and 2.5% steel fibre content. The optimum UHPC mix achieved good scores in terms of the strength index and the carbon emission index, indicating the concrete is eco-friendly and sustainable.

The Dynamic Compressive Behavior of Waved Fiber-Reinforced Ultrahigh-Performance Cementitious Composites Containing Fly Ash and Ground Granulated Blast-Furnace Slag

The Dynamic Compressive Behavior of Waved Fiber-Reinforced Ultrahigh-Performance Cementitious Composites Containing Fly Ash and Ground Granulated Blast-Furnace Slag

Micro-nano scale pore structure and fractal dimension of ultra-high performance cementitious composites modified with nanofillers

The development of ultra-high performance cementitious composite (UHPCC) represents a significant advancement in the field of concrete science and technology, but insufficient hydration and high autogenous shrinkage relatively increase the pores inside UHPCC, in turn, affecting the macro-performance of UHPCC. This paper, initially, optimized the pore structure of UHPCC using different types and dimensions of nanofillers. Subsequently, the pore structure characteristics of nano-modified UHPCC were investigated by the mercury intrusion porosimeter method and fractal theory. Finally, the fluid permeability of nano-modified UHPCC was estimated by applying the Katz-Thompson equation. Experimental results showed that all incorporated nanofillers can refine the pore structure of UHPCC, but nanofillers with different types and dimensions have various effects on the pore structure of UHPCC. Specifically, CNTs, especially the thin-short one, can significantly reduce the porosity of UHPCC, whereas nanoparticles, especially nano-SiO2, are more conducive to refine the pore size. Among all nanofillers, nano-SiO2 has the most obvious effect on pore structure, reducing the porosity, specific pore volume and most probable pore radius of UHPCC by 31.9%, 35.1% and 40.9%, respectively. Additionally, the pore size distribution of nano-modified UHPCC ranges from 10−1nm–105nm, and the gel pores and fine capillary pores in the range of 3–50 nm account for more than 70% of the total pore content, confirming nanofillers incorporation can effectively weaken pore connectivity and induce pore distribution to concentrate at nanoscale. Fractal results indicated the provision of nanofillers reduces the structural heterogeneity of gel pores and fine capillary pores, and induces homogenization and densification of UHPCC matrix, in turn, decreasing the UHPCC fluid permeability by 15.7%–79.2%.

Study on crack propagation of functionally graded ultra-high performance cementitious composite

This study investigates the damage process and crack propagation of functionally graded ultra-high-performance cementitious composite (FGUHPCC) with different layers (two and three layers) and fibers types (steel and PVA) through four-point bending test. The evolution process of surface displacement and strain of the sample was analyzed by digital image correlation (DIC) technology, and the influence of the top, middle and bottom layers of FGUHPCC on the damage pattern are also investigated by RFPA3D program. The results indicate that functionally graded design improves the equivalent flexural strength and deflection capacity of the specimens compared with the UHPCC with single layer design. FGUHPCC with three layers and mixed steel and polyvinyl alcohol fibers exhibited best flexural behavior. According to the recorded DIC data and corresponding analyses, the crack opening displacement (COD) profile of functionally graded design with three layers is mutable and nonlinear, and the maximum crack propagation speed is 0.096 L/s, which is the lowest compared with other tested specimens, and the largest crack area ratios are about 0.04% and 0.147% at LOP and MOR, respectively. Based on RFPA3D results, with the change of fiber content, the cumulative AE energy growth rate (k) of bottom layer is about 2.7 times and 1.5 times of that of the middle layer and the top layer, respectively.

Feasibility study on preparing economical and environmentally-friendly high-flowability ultra-high performance cementitious composites with original graded stone powder free recycled manufactured sands

With the depletion of river sand and the rising price of quartz sand, more and more researchers are trying to use manufactured sand to prepare ultra-high performance concrete (UHPC). However, due to the large amount of fine particles and high water demand, few studies are available to directly use the manufactured sand in its original state to prepare UHPC. To overcome the above problems, in this study, two locally available recycled manufactured sands are used as aggregates, and an attempt is made to maximize the use of their original gradation to prepare a cleaner construction production integrating high flowability, excellent mechanical performance, high cost-effective and environmentally-friendly property that meets the engineering requirements. The properties of workability, mechanical strengths, volume stability, hydration degree, pore structures, morphology of interfacial transition zone (ITZ), carbon emission and production cost are evaluated and discussed. Results indicate that all the mixtures prepared in this study can be considered to have high flowability except when granite sand is completely used. The mixture containing 75% tuff sand can even reach a compressive strength of 166.2 MPa, which is 10.5% higher than the reference one. A reduction of 28.9% can be observed in the early-age autogenous shrinkage of tuff sand UHPC as compared to the reference specimen. The mercury intrusion porosimetry (MIP) and X-ray computed tomography (X-CT) results demonstrate that the micropore volume, porosity and number of mesopores of UHPC increase to a certain extent when manufactured sand is utilized. The scanning electron microscope (SEM) observation reveals the most compact ITZ between cement paste and waste tuff sand. Additionally, the recycled manufactured sand UHPC can diminish the carbon emission of 19 kg and the cost of 27.4% (granite sand) and 25.5% (tuff sand) per cubic meter, showing excellent environmental and economical benefits.

Flexural behavior of the UHPCC containing glass powder as partial substitute of cement/silica fume

This study aims to achieve the sustainability and environmental protection of ultra-high performance cementitious composite (UHPCC) by substituting cement/silica fume with glass powder (GP), and to investigate the influence of various GP substitution levels on flexural behavior. The damage patterns of GP-UHPCC are also investigated by using digital image control technique and RFPA3D program. The crack opening displacement, crack length, internal damage degree of all test series with various GP substitution levels were quantitatively characterized. The results indicate that GP as partial substitution in UHPCC is able to contribute to improving flexural strength. The energy absorption capacity of the specimen with 20% GP substitution level in all loading phases is the largest among all specimens. In addition, the crack area ratio and AE-accumulative energy of high GP substitution levels (15%–30%) is obviously higher than that of low levels (0%–10%). Generally speaking, GP substitution level of 15%–30% is found the most effective range for improving flexural behavior in this study.

Effect of steel fiber type and content on the dynamic tensile properties of ultra-high performance cementitious composites (UHPCC)

As one of the most promising construction and building materials in the past 30 years, ultra-high performance concrete (UHPC) has attracted a great deal of attention and the studies on its improvement and dynamic tensile behaviors become more important for its wider use in the related fields. In this contribution, a novel ultra-high performance cementitious composites (UHPCC) was developed with lower cement content, 20% of cement is replaced with fly ash and blast furnace slag, to reduce the raw material cost and carbon emission in production. Uniaxial compression, quasi-static and dynamic splitting tests were carried out to investigate the influences of steel fiber type (straight fiber and waved fiber) and content (volume fraction (0%, 1%, 2%)) on the uniaxial compressive strength, static tensile strength and dynamic tensile behaviors for current UHPCC material. The dynamic splitting tests were conducted on 100 disc specimens (75 mm in diameter and 37.5 mm in thickness) under five different impact pressure at a strain-rate range of 20–110 s−1 to study the strain rate effect by using a Split Hopkinson pressure bar (SHPB) system and the samples’ failure processes were captured by a high-speed camera. Based on the test results, the variations of energy absorption with the fiber type and content under static and dynamic tensile conditions are also analyzed, and combined with the experimental data from previous studies, an improved empirical tensile strength rate sensitivity (DIFft) model is proposed, which agrees well with the experiment results and can be used in the numerical simulation. At last, the failure process and pattern of different types of UHPCCs in the dynamic splitting test are also studied.

Influence of calcination temperature of impure kaolinitic clay on hydration and strength development of ultra-high-performance cementitious composite

Despite the recent considerable interest in sustainable supplementary cementitious materials, the effect of calcined impure clay on ultra-high-performance cementitious composite (UHPC) is insufficiently understood. In this study, three impure kaolinitic clays calcined at 600 °C, 800 °C, and 1000 °C were compared with quartz powder in terms of hydration reaction and strength development of UHPC. As a function of calcination temperature, the clays had different effects on the properties of UHPC. The clays calcined at 600–800 °C increased the initial strength of UHPC (≤3 days) by ∼10–35% but show lower strength by ∼5–9% after 28 days compared to reference sample. It is because the clays accelerated both cement hydration and pozzolanic reaction at an early age of the UHPC, but the premature consumption of water and pore refinement inhibited the long-term pozzolanic reaction. In contrast, the clay calcined at 1000 °C no longer affected the UHPC’s strength after increasing the 1st-day strength by 17%, since it acted as an inert filler after early age (>1 day). However, once heat treatment (at 90 °C for 48 h) was applied to UHPC, all of the clays did not express pozzolanic reactivity because the main initiative for the pozzolanic reaction shifted from metakaolin to silica fume. From these results, it is concluded that the use of calcined clays does not notably reduce the strength of UHPC, as long as impure clays with sufficient kaolinite content (>40%) are used.

Avaliação das propriedades de compósitos cimentícios de ultra-alto desempenho com resíduos de pó de vidro

Abstract Novel developments on concrete technology such as high and ultra-high-performance concrete (HPC and UHPC) are notorious by its high consumption of Portland cement. Supplementary cementitious materials have been used as partial replacement of Portland cement aiming to minimizing clinker content, optimizing the use of binders, reducing CO2 emissions, and increasing durability. Waste glass powder could be an alternative due to its silica-rich nature and wide availability. This work aims to assess the influence Portland cement substitution by finely ground waste glass powder in contents of 10%, 20%, 30% and 50% on physical and mechanical behavior of ultra-high-performance cementitious composites (UHPCC). Results indicates the use of glass powder as substitution up to 50% of Portland cement does not significantly affect the analyzed properties at 28 days.

Development of high performance lightweight concrete using ultra high performance cementitious composite and different lightweight aggregates

To reduce the dead load of concrete structures, this study developed a high performance lightweight aggregate concrete (HPLAC) by combining the use of ultra high performance cementitious composite (UHPC) and different types of aluminosilicate lightweight aggregates (LWAs). The physicochemical properties of two types of LWAs (i.e. expanded clay and expanded shale) influencing the HPLAC were elaborated and compared. The composition distribution and micromechanical properties in the interfacial regions of paste and LWAs were revealed by elemental mapping and nanoindentation. The results showed that the incorporation of the clay LWAs or shale LWAs in the HPLAC led to similar density and thermal conductivity values, while the use of the shale LWAs induced a lower water absorption and higher strength of HPLAC as compared to the clay LWAs due to the fine pore structure and higher pozzolanic activity of the former. The internal curing effect provided by the pre-wetted shale LWAs was more efficient in enhancing the hydration of binder, and the Al dissolution from the shale LWAs further densified the interfacial bonding to form a dense rim surrounding LWAs, resulting in improved micromechanical properties at the interface. The X-ray CT results indicated that the adoption of UHPC was beneficial to preventing segregation of the LWAs and steel fibers in the HPLAC. By virtue of the physical-chemical interactions of LWAs, the synergetic use of UHPC and pre-wetted shale LWAs was able to produce an HPLAC with high structural efficiency, good thermal insulation, low autogenous shrinkage and permeability.

Multiscale insights on enhancing tensile properties of ultra-high performance cementitious composite with hybrid steel and polymeric fibers

Ultra-high performance cementitious composite (UHPCC) is an advanced composite material with superior compressive strength. UHPCC with low steel fiber content typically fails in a single-crack mode under tension, resulting in a high risk of catastrophic structural collapse and limiting its wide application. However, high steel fiber content adversely affects the electrochemical corrosion resistance and long-term performance of UHPCC. Therefore, enhancing the tensile performance of UHPCC with low fiber content has attracted great attention. Polyvinyl alcohol (PVA) fiber is characterized by outstanding crack control ability in cementitious materials. In this study, the macroscale flowability, tensile and flexural properties, ductility and failure mode of UHPCC containing steel and PVA fibers at low fiber content level were explored and analyzed. Results indicate that the post-crack energy absorption of UHPCC improved by more than 40% following fibers hybridization. The failure mode of UHPCC with low fiber content shifted from single crack mode to ductile multiple cracks mode. Microscale observations show that PVA fibers can bridge crack and transfer load at the interface after first cracking, and impede slippage between steel fiber and matrix, thus endows UHPCC with desirable ductile multiple cracks failure mode. The findings of this study provide a foundation for designing UHPCC with ductile tensile performance and give an in-depth understanding of underlying mechanisms of hybrid fibers, promoting the application of ductile UHPCC in innovative structures.

Effect of water/cement ratio on micro-nanomechanical properties of the interface between cementitious matrix and steel microfibers in ultra-high performance cementitious composites

abstract: Ultra-high performance concretes with steel microfibers have been studied in depth with the aim of producing more efficient and durable structures. The performance of these materials depends on the characteristics of the interface between microfibers and cementitious matrix. This research investigates the micro-nanomechanical properties of the interfacial transition zone between the steel microfibers and the matrix of ultra-high performance cementitious composite. The effect of the water/cement ratio and distance from the microfiber were analyzed. The results confirm the formation of high-density calcium-silicate-hydrate (HD C-S-H) matrix at higher concentrations than low-density calcium-silicate-hydrate (LD C-S-H) for w/c ratios of 0.2 and 0.3. The properties in cementitious matrix interface with steel microfibers were very similar to that measured for the cement paste, and no significant difference was observed regarding the distance to the microfibers in relation to the elastic modulus, hardness and chemical composition. Thus, the authors can conclude that the formation of a less resistant region does not occur at the interfacial transition zone cement paste/microfibers.

Development and characteristics of ultra high-performance lightweight cementitious composites (UHP-LCCs)

High strength and light weight are two recent opposite development trends of concrete. This study proposed a design concept of an ultra high-performance lightweight cementitious composite (UHP-LCC), which had a compressive strength of higher than 120 MPa and an air-dried density down to around 1800 kg/m3. The UHP-LCCs were innovatively developed by incorporating micro-sized hollow particles with a high strength shell (hollow glass microspheres, HGM) into an ultra-high performance cementitious composite (UHPC). The roles of HGM in the UHP-LCCs were investigated by evaluating the reactivity of the HGM and the mechanisms on achieving the excellent mechanical properties, low density and superior durability were revealed. The Chapelle test results showed that the HGM exhibited some pozzolanic reactivity, which facilitated the reaction between the shell of HGM and the alkali hydration products of the paste matrix. This chemical reaction was conducive to improving the HGM-paste interface and enhancing the mechanical properties. With the use of microspheres with a high stiff shell, the fundamental properties of the UHP-LCCs including thermal insulation, sound absorption, resistance to water ingress and electrical resistivity were improved significantly. The strategies for preparing the UHP-LCCs with high structural efficiency and great performance were proposed. The results of this study provide a new approach for designing and producing a lightweight UHPC, which would be a promising material for long-span structures.

Mechanical characteristics of PET fibre-reinforced green ultra-high performance composite concrete

Experimental investigations were performed to evaluate the effect of waste Polyethylene Terephthalate (PET) fibres on the mechanical properties of Green Ultra-High Performance Cementitious Composites (GUHPCCs). Ultra-fine Palm Oil Fuel Ash (UPOFA) and Silica Fume (SF) were utilised to produce GUHPCCs that consist of up to 50% UPOFA and 20% SF as a partial replacement binder with cement. PET fibres were added to the GUHPCCs at a proportion of 1% of the total mixed volume, to produce Green Ultra-High Performance PET reinforced Cementitious Composites (GUHPPCCs). The mechanical properties and flexural performance of the resulting beams and slabs, including their stress–strain behaviour and ductility, were investigated. Results showed that addition of PET fibres increases the flexural strength of GUHPPCCs beams by approximately 63.24% compared with that of the ultra-high performance concrete control at the age of 90 days. Moreover, significant improvements in the flexural capacity and ductility index of the GUHPPCCs slabs were obtained. These findings may due to the bridging effects of PET fibres. Thus, the combination of UPOFA and SF with PET fibres can produce GUHPPCCs with superior mechanical properties and enhanced ductility.

Eco-friendly ultra-high performance cement pastes produced with quarry wastes as alternative fillers

About 35 billion tons of quarried material are produced annually throughout the world, generating large amounts of waste powders which are usually disposed of in landfills. This work investigated the feasibility of producing eco-friendly ultra-high performance cement pastes with diabase, granite and basalt quarry wastes as alternatives to quartz and limestone conventional fillers. The fresh properties (rheometry and mini slump), hydration (calorimetry, TGA and XRD), 3- and 28-day strength and microstructure (SEM-EDS) of the pastes were investigated. The results showed that granite and diabase fillers increased the yield stress of the pastes by about 1.6 times compared with quartz and limestone, while basalt increased it by 9 times. Only granite increased the apparent viscosity due to the irregular shape and rough texture of its particles. All the pastes presented self-levelling aspect. Calorimetry indicated equivalent hydration kinetics for quartz, granite and basalt, while limestone and diabase shortened the induction period and elevated the 72-h cumulative heat by 5%. XRD and TGA indicated similar compositions for all the pastes (calcium hydroxide and hydrates contents respectively of 6.8 ± 0.4% and 13.4 ± 0.4% at 28 days), and no evidence of pozzolanic activity by the fillers. All the mixes presented 3- and 28-day compressive strengths respectively of 71 ± 3 MPa and 132 ± 2 MPa, indicating that the incorporation of the quarry fillers did not lead to significant differences in strength. In line with that, SEM-EDS indicated similar microstructures. Overall, the alternative quarry powders can be used in the production of ultra-high performance cementitious composites with no impairments on its fresh, hardened and microstructural characteristics, contributing to the eco-efficiency of construction.

Experimental and numerical study of ultra-high performance cementitious composites filled steel tube (UHPCC-FST) subjected to close-range explosion

The blast performance of ultra-high performance cementitious composites filled steel tube (UHPCC-FST) subjected to close-range explosion were investigated experimentally and numerically. Firstly, the field test of four circular UHPCC-FST specimens under the close-range TNT charge explosion with the scaled standoff distance Z of 0.12≤Z ≤ 0.14 m/kg1/3 were conducted, the global and local deformations of specimens were experimentally examined. Then, three methods were applied to analyze the dynamic responses of those specimens, i.e., numerical simulations based on Arbitrary-Lagrangian-Eulerian elements method (ALE method) and velocity loading method (velocity method), as well as the equivalent single degree of freedom method (SDOF method). By comparing the experimental data of the present and existing total nineteen close-range explosion test on CFST (0.14≤Z ≤ 0.58 m/kg1/3), the velocity method is recommended by considering both the accuracy and efficiency of computation. The derived conclusions could provide helpful references for evaluating the blast resistance and designing the CFST under potential close-range explosions.

Hydrophobic modification of ultra-high-performance fiber-reinforced composites with matrices enhanced by aluminum oxide nano-fibers

Aluminum oxide nanoparticles can be used in small quantities to create a high-performance and ultra-high-performance cementitious composites. High volumes, up to 20% of supplementary cementitious materials such as silica fume or metakaolin, are often used to achieve the high strength of up to 150 MPa in high performance and ultra-high performance cementitious composites. This research demonstrates that when aluminum oxide (Al2O3) nano-fibers are used in cement-based composites, compressive strength of up to 175 MPa can be achieved at very low dosages of silica fume and metakaolin. This effect is achieved by using low water to cementitious materials ratio, selection of cement, and utilizing the seeding and reinforcing effects of by the nano-fibers. Furthermore, the ultra-high performance cement-based composite (UHPC) can include polyethylene fibers which provide enhanced strain hardening and multi-cracking behavior. The UHPC was tested to evaluate the effects of superhydrophobic modification. Superhydrophobic modification utilizes siloxane-based admixtures to form a well-dispersed air void system whose voids have hydrophobic properties. The experimental results demonstrate that a superhydrophobic modification may reduce the performance of advanced composites with Al2O3 nano-fibers. High-performance cementitious materials are critical for the next generation of infrastructure. This research evaluates the effects of superhydrophobic admixtures in ultra-high-strength fiber-reinforced composites with Al2O3 nano-fibers. The incorporation of small quantities of aluminum oxide nano-fibers in UHPC may prove to be a viable option for compressive strength enhancement; however, incorporating a superhydrophobic air void structure was not effective for enhancement of ductility.

Effect of graphene oxide on microstructure and strengthened properties of fly ash and silica fume based cement composites

Now a day’s utilization of nano materials have been increased for enhancing the ultrahigh performance cementitious composites. Accordingly, graphene oxide (GO) was found as one of the nanomaterials, which represents an unprecedented range properties with a potential to enhance the strength and toughness of cement based composites. GO is also an appropriate material to react with binder particles as it consists a range of reactive oxygen operational chemical groups. This paper investigates the effect of graphene oxide (GO) on microstructure and strengthened properties of fly ash and silica fume based cement composites, by determining the characteristics of cement composites through mechanical and micro structural studies (SEM and XRD analysis). The Scanning Electron Microscope (SEM) images exhibited that, graphene oxide (GO) converted the structural nature of cement composite from a porous nature to a considerably pore filled nature with the improved mechanical properties. XRD technique was assisted in identifying the crystalline materials and studying the phase composition of cement composites. This significant extensive research provides a new pathway for achieving high performance cement composites.

Response of ultra-high performance cementitious composites filled steel tube (UHPCC-FST) subjected to low-velocity impact

Abstract This paper presents a combined experimental and numerical study on the transverse impact behavior of ultra-high performance cementitious composites filled steel tube (UHPCC-FST). UHPCC-FSTs were firstly fabricated by preparing the UHPCC with the cube compressive strength of 141.5 MPa. Then three specimens were tested in a drop-hammer impact device, and the impact force- and deflection-time histories of specimens under different release heights (5.0, 8.0 and 11.0 m) of the drop hammer were obtained and discussed. Furthermore, by using the commercial finite element (FE) program Hypermesh/LS-DYNA, a FE model was established to predict the impact behavior of UHPCC-FST. K&C constitutive model for concrete was adopted, and the corresponding model parameters for UHPCC were calibrated based on a series of test data (static compressive and direct tensile tests, dynamic compressive and tensile tests, triaxial compressive test, fly plate impact test), which were then validated by the present and existing drop hammer tests.