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17 pages, 7160 KiB

Open AccessArticle

Influence of Fiber Addition on the Properties of High-Performance Concrete

by Szymon Grzesiak, Matthias Pahn, Milan Schultz-Cornelius, Stefan Harenberg and Christoph Hahn

Materials 2021, 14(13), 3736; https://doi.org/10.3390/ma14133736 - 3 Jul 2021

Cited by 18 | Viewed by 3850

Abstract

High performance fiber-reinforced concrete (HPFRC) has been frequently investigated in recent years. Plenty of studies have focused on different materials and types of fibers in combination with the concrete matrix. Experimental tests show that fiber dosage improves the energy absorption capacity of concrete [...] Read more.

High performance fiber-reinforced concrete (HPFRC) has been frequently investigated in recent years. Plenty of studies have focused on different materials and types of fibers in combination with the concrete matrix. Experimental tests show that fiber dosage improves the energy absorption capacity of concrete and enhances the robustness of concrete elements. Fiber reinforced concrete has also been illustrated to be a material for developing infrastructure sustainability in RC elements like façade plates, columns, beams, or walls. Due to increasing costs of the produced fiber reinforced concrete and to ensure the serviceability limit state of construction elements, there is a demand to analyze the necessary fiber dosage in the concrete composition. It is expected that the surface and length of used fiber in combination with their dosage influence the structure of fresh and hardened concrete. This work presents an investigation of the mechanical parameters of HPFRC with different polymer fiber dosage. Tests were carried out on a mixture with polypropylene and polyvinyl alcohol fiber with dosages of 15, 25, and 35 kg/m³ as well as with control concrete without fiber. Differences were observed in the compressive strength and in the modulus of elasticity as well as in the flexural and splitting tensile strength. The flexural tensile strength test was conducted on two different element shapes: square panel and beam samples. These mechanical properties could lead to recommendations for designers of façade elements made of HPFRC. Full article

(This article belongs to the Special Issue High Performance Concrete)

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17 pages, 23798 KiB

Open AccessArticle

A Numerical Study on Structural Performance of Railway Sleepers Using Ultra High-Performance Concrete (UHPC)

by Moochul Shin, Younghoon Bae and Sukhoon Pyo

Materials 2021, 14(11), 2979; https://doi.org/10.3390/ma14112979 - 31 May 2021

Cited by 10 | Viewed by 3664

Abstract

This numerical study investigates the structural performance of railway sleepers made of ultra high-performance concrete (UHPC). First, numerical concrete sleepers are developed, and the tensile stress-strain relationship obtained from the direct tension test on the UHPC coupons is used for the tensile constitutive [...] Read more.

This numerical study investigates the structural performance of railway sleepers made of ultra high-performance concrete (UHPC). First, numerical concrete sleepers are developed, and the tensile stress-strain relationship obtained from the direct tension test on the UHPC coupons is used for the tensile constitutive model after applying a fiber orientation reduction factor. The numerical sleeper models are validated with the experimental data in terms of the force and crack-width relationship. Second, using the developed models, a parametric study is performed to investigate the performance of the UHPC sleepers while considering various design/mechanical/geometrical parameters: steel fiber contents, size of the cross-section, and diameter and strength of prestressing (PS) tendons. The simulation results indicate that the size of the cross-section has the most impacts on the performance, while the effect of yielding strengths of PS tendons is minimal among all the parameters. Engineers need to pay attention to efficiency and an economical factor when using a larger cross-section, since sleepers with larger cross-sections can be an over-designed sleeper. This study suggests an economical design factor for engineers to evaluate what combination of parameters would be economical designs. Full article

(This article belongs to the Special Issue High Performance Concrete)

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19 pages, 4019 KiB

Open AccessArticle

Study of Combined Multi-Point Constraint Multi-Scale Modeling Strategy for Ultra-High-Performance Steel Fiber-Reinforced Concrete Structures

by Zuohua Li, Zhihan Peng and Jun Teng

Materials 2020, 13(23), 5320; https://doi.org/10.3390/ma13235320 - 24 Nov 2020

Cited by 7 | Viewed by 2331

Abstract

Compared with normal strength concrete (NSC), ultra-high-performance steel fiber-reinforced concrete (UHPFRC) shows superior performance. The concrete damage plasticity (CDP) model in ABAQUS can predict the mechanical properties of UHPFRC components well after calibration. However, the simulation of the whole structure is seriously restricted [...] Read more.

Compared with normal strength concrete (NSC), ultra-high-performance steel fiber-reinforced concrete (UHPFRC) shows superior performance. The concrete damage plasticity (CDP) model in ABAQUS can predict the mechanical properties of UHPFRC components well after calibration. However, the simulation of the whole structure is seriously restricted by the computational capability. In this study, a novel multi-scale modeling strategy for UHPFRC structure was proposed, which used a calibrated CDP model. A novel combined multi-point constraint (CMPC) was established by the simultaneous equations of displacement coordination and energy balance in different degrees of freedom of interface nodes. The advantage is to eliminate the problem of the tangential over-constraint of displacement coordination equation at the interface and to avoid stress iteration of the energy balance equation in the plastic stage. The expressions of CMPC equations of typical multi-scale interface connection were derived. The multi-scale models of UHPFRC components under several load cases were established. The results show that the proposed strategy can well predict the strain distribution and damage distribution of UHPFRC while significantly reducing the number of model elements and improving the computational efficiency. This study provides an accurate and efficient finite element modeling strategy for the design and analysis of UHPFRC structures. Full article

(This article belongs to the Special Issue High Performance Concrete)

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19 pages, 8543 KiB

Open AccessArticle

Fibre Distribution Characterization of Ultra-High Performance Fibre-Reinforced Concrete (UHPFRC) Plates Using Magnetic Probes

by Lufan Li, Jun Xia, Chee Chin and Steve Jones

Materials 2020, 13(22), 5064; https://doi.org/10.3390/ma13225064 - 10 Nov 2020

Cited by 13 | Viewed by 2429

Abstract

Ultra-high performance fibre reinforced concrete (UHPFRC) is an innovative cement-based engineering material. The mechanical properties of UHPFRC not only depend on the properties of the concrete matrix and fibres, but also depend on the interaction between these two components. The fibre distribution is [...] Read more.

Ultra-high performance fibre reinforced concrete (UHPFRC) is an innovative cement-based engineering material. The mechanical properties of UHPFRC not only depend on the properties of the concrete matrix and fibres, but also depend on the interaction between these two components. The fibre distribution is affected by many factors and previous researchers had developed different approaches to test the fibre distribution. This research adopted the non-destructive C-shape ferromagnetic probe inductive test and investigated the straight steel fibre distribution of the UHPFRC plate. A simplified characterization equation is introduced with an attenuation factor to consider the different plate thicknesses. The effective testing depth of this probe was tested to be 24 mm. By applying this method, fibre volume content and the fibre orientation angle can be calibrated for the entire plate. The fibre volume content generally fulfilled the design requirement. The fibre orientation angle followed a normal distribution, with a mean value of 45.60°. By testing small flexural specimens cut from the plates, it was found out that the mechanical performance (peak flexural strength) correlates with the product of fibre volume content and cosine fibre orientation angle. Full article

(This article belongs to the Special Issue High Performance Concrete)

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16 pages, 494 KiB

Open AccessArticle

The Influence of Ambient Temperature on High Performance Concrete Properties

by Alina Kaleta-Jurowska and Krystian Jurowski

Materials 2020, 13(20), 4646; https://doi.org/10.3390/ma13204646 - 18 Oct 2020

Cited by 14 | Viewed by 3341

Abstract

This paper presents the results of tests on high performance concrete (HPC) prepared and cured at various ambient temperatures, ranging from 12 °C to 30 °C (the compressive strength and concrete mix density were also tested at 40 °C). Special attention was paid [...] Read more.

This paper presents the results of tests on high performance concrete (HPC) prepared and cured at various ambient temperatures, ranging from 12 °C to 30 °C (the compressive strength and concrete mix density were also tested at 40 °C). Special attention was paid to maintaining the assumed temperature of the mixture components during its preparation and maintaining the assumed curing temperature. The properties of a fresh concrete mixture (consistency, air content, density) and properties of hardened concrete (density, water absorption, depth of water penetration under pressure, compressive strength, and freeze–thaw durability of hardened concrete) were studied. It has been shown that increased temperature (30 °C) has a significant effect on loss of workability. The studies used the concrete slump test, the flow table test, and the Vebe test. A decrease in the slump and flow diameter and an increase in the Vebe time were observed. It has been shown that an increase in concrete curing temperature causes an increase in early compressive strength. After 3 days of curing, compared with concrete curing at 20 °C, an 18% increase in compressive strength was observed at 40 °C, while concrete curing at 12 °C had a compressive strength which was 11% lower. An increase in temperature lowers the compressive strength after a period longer than 28 days. After two years of curing, concrete curing at 12 °C achieved a compressive strength 13% higher than that of concrete curing at 40 °C. Freeze–thaw performance tests of HPC in the presence of NaCl demonstrated that this concrete showed high freeze–thaw resistance and de-icing materials (surface scaling of this concrete is minimal) regardless of the temperature of the curing process, from 12 °C to 30 °C. Full article

(This article belongs to the Special Issue High Performance Concrete)

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13 pages, 12336 KiB

Open AccessArticle

A Study on Initial Setting and Modulus of Elasticity of AAM Mortar Mixed with CSA Expansive Additive Using Ultrasonic Pulse Velocity

by Gum-Sung Ryu, Sung Choi, Kyung-Taek Koh, Gi-Hong Ahn, Hyeong-Yeol Kim and Young-Jun You

Materials 2020, 13(19), 4432; https://doi.org/10.3390/ma13194432 - 5 Oct 2020

Cited by 6 | Viewed by 2540

Abstract

This study investigated the hardening process of alkali-activated material (AAM) mortar using calcium sulfoalumiante (CSA) expansive additive (CSA EA), which accelerates the initial reactivity of AAMs, and subsequent changes in ultrasonic pulse velocity (UPV). After the AAM mortar was mixed with three different [...] Read more.

This study investigated the hardening process of alkali-activated material (AAM) mortar using calcium sulfoalumiante (CSA) expansive additive (CSA EA), which accelerates the initial reactivity of AAMs, and subsequent changes in ultrasonic pulse velocity (UPV). After the AAM mortar was mixed with three different contents of CSA EA, the setting and modulus of elasticity of the mortar at one day of age, which represent curing steps, were measured. In addition, UPV was used to analyze each curing step. The initial and final setting times of the AAM mortar could be predicted by analyzing the UPV results measured for 14 h. In addition, the dynamic modulus of elasticity calculated using the UPV results for 24 h showed a tendency similar to that of the static modulus of elasticity. The test results showed that the use of CSA EA accelerated the setting of the AAM mortar and increased the modulus of elasticity, and these results could be inferred using UPV. The proposed measurement method can be effective in evaluating the properties of a material that accelerates the initial reactivity. Full article

(This article belongs to the Special Issue High Performance Concrete)

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15 pages, 3191 KiB

Open AccessArticle

Fresh and Hardened Properties of Portland Cement-Slag Concrete Activated Using the By-Product of the Liquid Crystal Display Manufacturing Process

by Sung Choi and Sukhoon Pyo

Materials 2020, 13(19), 4354; https://doi.org/10.3390/ma13194354 - 30 Sep 2020

Cited by 4 | Viewed by 2911

Abstract

This experimental research investigated the applicability of the liquid crystal display (LCD) by-product of the refining process as a sustainable and alternative alkali activator for ground granulated blast-furnace slag (GGBFS) blended cement concrete. Three levels of binder replacement using the industrial by-product, and [...] Read more.

This experimental research investigated the applicability of the liquid crystal display (LCD) by-product of the refining process as a sustainable and alternative alkali activator for ground granulated blast-furnace slag (GGBFS) blended cement concrete. Three levels of binder replacement using the industrial by-product, and four water/binder ratios were considered in order to evaluate the effects of the replacement in fresh and hardened properties of the blended concrete. XRD and TG analyses confirmed that the by-product that contains abundant alkali compounds promotes the reactivity of GGBFS. The test results indicated that the incorporation of the by-product results in delayed setting and degraded workability due to the highly porous nature of the by-product, yet shows rapid early-age strength development of the blended concrete as conventional alkaline activators for GGBFS. These characteristics shed light on a simple yet effective and practical means of reusing the industrial by-product as an alternative alkaline activator. Full article

(This article belongs to the Special Issue High Performance Concrete)

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20 pages, 4155 KiB

Open AccessArticle

Performance Comparison between Densified and Undensified Silica Fume in Ultra-High Performance Fiber-Reinforced Concrete

by Sung-Hoon Kang, Sung-Gul Hong and Juhyuk Moon

Materials 2020, 13(17), 3901; https://doi.org/10.3390/ma13173901 - 3 Sep 2020

Cited by 25 | Viewed by 4596

Abstract

Silica fume (SF) is a key ingredient in the production of ultra-high performance fiber-reinforced concrete (UHPFRC). The use of undensified SF may have an advantage in the dispersion efficiency inside cement-based materials, but it also carries a practical burden such as high material [...] Read more.

Silica fume (SF) is a key ingredient in the production of ultra-high performance fiber-reinforced concrete (UHPFRC). The use of undensified SF may have an advantage in the dispersion efficiency inside cement-based materials, but it also carries a practical burden such as high material costs and fine dust generation in the workplace. This study reports that a high strength of 200 MPa can be achieved by using densified SF in UHPFRC with Portland limestone cement. Additionally, it was experimentally confirmed that there was no difference between densified and undensified SFs in terms of workability, compressive and flexural tensile strengths, and hydration reaction of the concrete, regardless of heat treatment, because of a unique mix proportion as well as mixing method for dispersing agglomerated SF particles. It was experimentally validated that the densified SF can be used for both precast and field casting UHPFRCs with economic and practical benefits and without negative effects on the material performance of the UHPFRC. Full article

(This article belongs to the Special Issue High Performance Concrete)

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11 pages, 2737 KiB

Open AccessArticle

CO₂ Curing Efficiency for Cement Paste and Mortars Produced by a Low Water-to-Cement Ratio

by Seong Ho Han, Yubin Jun, Tae Yong Shin and Jae Hong Kim

Materials 2020, 13(17), 3883; https://doi.org/10.3390/ma13173883 - 2 Sep 2020

Cited by 27 | Viewed by 3652

Abstract

Curing by CO₂ is a way to utilize CO₂ to reduce greenhouse gas emissions. Placing early-age cement paste in a CO₂ chamber or pressure vessel accelerates its strength development. Cement carbonation is attributed to the quickened strength development, and CO [...] Read more.

Curing by CO₂ is a way to utilize CO₂ to reduce greenhouse gas emissions. Placing early-age cement paste in a CO₂ chamber or pressure vessel accelerates its strength development. Cement carbonation is attributed to the quickened strength development, and CO₂ uptake can be quantitatively evaluated by measuring CO₂ gas pressure loss in the pressure vessel. A decrease in CO₂ gas pressure is observed with all cement pastes and mortar samples regardless of the mix proportion and the casting method; one method involves compacting a low water-to-cement ratio mix, and the other method comprises a normal mix consolidated in a mold. The efficiency of the CO₂ curing is superior when a 20% concentration of CO₂ gas is supplied at a relative humidity of 75%. CO₂ uptake in specimens with the same CO₂ curing condition is different for each specimen size. As the specimen scale is larger, the depth of carbonation is smaller. Incorporating colloidal silica enhances the carbonation as well as the hydration of cement, which results in contributing to the increase in the 28-day strength. Full article

(This article belongs to the Special Issue High Performance Concrete)

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16 pages, 4133 KiB

Open AccessArticle

Characterization of Porous Cementitious Materials Using Microscopic Image Processing and X-ray CT Analysis

by Jinyoung Yoon, Hyunjun Kim, Sung-Han Sim and Sukhoon Pyo

Materials 2020, 13(14), 3105; https://doi.org/10.3390/ma13143105 - 12 Jul 2020

Cited by 22 | Viewed by 3959

Abstract

The use of lightweight concrete has continuously increased because it has a primary benefit of reducing dead load in a concrete infrastructure. Various properties of lightweight concrete, such as compressive strength, elastic modulus, sound absorption performance, and thermal insulation, are highly related to [...] Read more.

The use of lightweight concrete has continuously increased because it has a primary benefit of reducing dead load in a concrete infrastructure. Various properties of lightweight concrete, such as compressive strength, elastic modulus, sound absorption performance, and thermal insulation, are highly related to its pore characteristics. Consequently, the identification of the characteristics of its pores is an important task. This study performs a comparative analysis for characterizing the pores in cementitious materials using three different testing methods: a water absorption test, microscopic image processing, and X-ray computed tomography (X-ray CT) analysis. For all 12 porous cementitious materials, conventional water absorption test was conducted to obtain their water permeable porosities. Using the microscopic image processing method, various characteristics of pores were identified in terms of the 2D pore ratio (i.e., ratio of pore area to total surface area), the pore size, and the number of pores in the cross-sectional area. The 3D tomographic image-based X-ray CT analysis was conducted for the selected samples to show the 3D pore ratio (i.e., ratio of pore volume to total volume), the pore size, the spatial distribution of pores along the height direction of specimen, and open and closed pores. Based on the experimental results, the relationships of oven-dried density with these porosities were identified. Research findings revealed that the complementary use of these testing methods is beneficial for analyzing the characteristics of pores in cementitious materials. Full article

(This article belongs to the Special Issue High Performance Concrete)

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21 pages, 5353 KiB

Open AccessArticle

Reactive Powder Concrete Containing Basalt Fibers: Strength, Abrasion and Porosity

by Stefania Grzeszczyk, Aneta Matuszek-Chmurowska, Eva Vejmelková and Robert Černý

Materials 2020, 13(13), 2948; https://doi.org/10.3390/ma13132948 - 1 Jul 2020

Cited by 22 | Viewed by 3007

Abstract

The paper presents the test results of basalt fiber impact on a compressive and flexural strength, resistance to abrasion and porosity of Reactive Powder Concrete (RPC). The reasons for testing were interesting mechanical properties of basalt fibers, the significant tensile strength and flexural [...] Read more.

The paper presents the test results of basalt fiber impact on a compressive and flexural strength, resistance to abrasion and porosity of Reactive Powder Concrete (RPC). The reasons for testing were interesting mechanical properties of basalt fibers, the significant tensile strength and flexural strength, and in particular the resistance to high temperatures, as well as a relatively small number of RPC tests performed with those fibers and different opinions regarding the impact of those fibers on concrete strength. The composition of the concrete mix was optimized to obtain the highest packing density of particles in the composite, based on the optimum particle size distribution curve acc. to Funk. Admixture of basalt fibers was used in quantity 2, 3, 6, 8 and 10 kg/m³, length 12 mm and diameter 18 µm. A low water-to-binder ratio, i.e., from 0.24, was obtained through application of a polycarboxylate-based superplasticizer. The introduction of up to 10 kg/m³ of basalt fibers to RPC mix was proved to be possible, while keeping the same w/c ratio equal to 0.24, with a slight loss of workability of the concrete mix as the content of fibers increased. It was found that the increase of the fiber content in RPC to 10 kg/m³, despite the w/c ratio was kept the same, caused reduction of the concrete compressive strength by 18.2%, 7.8% and 13.6%, after 2, 7, and 28 days respectively. Whereas, the flexural strength of RPC increased gradually (maximum by 15.9%), along with the fiber quantity increase up to 6 kg/m³, and then it reduced (maximum by 17.7%), as the fiber content in the concrete was further increased. The reduction of RPC compressive strength, along with the increase in basalt fibers content, leads to the increase of the total porosity, as well as the change in pore volume distribution. The reduction of RPC abrasion resistance was demonstrated along with the increase of basalt fibers content, which was explained by the compressive strength reduction of that concrete. A linear relation between the RPC abrasion resistance and the compressive strength involves a high determination coefficient equal to 0.97. Full article

(This article belongs to the Special Issue High Performance Concrete)

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14 pages, 3349 KiB

Open AccessArticle

Effect of Pre-Wetted Zeolite Sands on the Autogenous Shrinkage and Strength of Ultra-High-Performance Concrete

by Guang-Zhu Zhang and Xiao-Yong Wang

Materials 2020, 13(10), 2356; https://doi.org/10.3390/ma13102356 - 20 May 2020

Cited by 29 | Viewed by 3242

Abstract

In this study, the carrier effect of zeolite sands in reducing the autogenous shrinkage and optimizing the microstructure of ultra-high-performance concrete (UHPC) is studied. Pre-wetted calcined zeolite sand (CZ), calcined at 500 °C for 30 min, and natural zeolite sand (NZ), with 15 [...] Read more.

In this study, the carrier effect of zeolite sands in reducing the autogenous shrinkage and optimizing the microstructure of ultra-high-performance concrete (UHPC) is studied. Pre-wetted calcined zeolite sand (CZ), calcined at 500 °C for 30 min, and natural zeolite sand (NZ), with 15 wt.% and 30 wt.% in UHPC, are used to partially replace standard sands. On that basis, a series of experiments are executed on the developed UHPC, including compressive strength, autogenous shrinkage, X-ray diffraction (XRD), and isothermal calorimetry experiments. With the increase of the zeolite sand content, the autogenous shrinkage of UHPC decreases gradually. Moreover, when the added CZ content is 30 wt.% (CZ30 specimen), it is effective in reducing autogenous shrinkage. Meanwhile, at the age of 28 days, the compressive strength of CZ30 is 97% of the control group. In summary, it is possible to effectively reduce the autogenous shrinkage of UHPC containing 30 wt.% CZ, without sacrificing its mechanical properties. Full article

(This article belongs to the Special Issue High Performance Concrete)

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18 pages, 5479 KiB

Open AccessArticle

Modeling and Design of SHPB to Characterize Brittle Materials under Compression for High Strain Rates

by Tomasz Jankowiak, Alexis Rusinek and George Z. Voyiadjis

Materials 2020, 13(9), 2191; https://doi.org/10.3390/ma13092191 - 10 May 2020

Cited by 28 | Viewed by 3671

Abstract

This paper presents an analytical prediction coupled with numerical simulations of a split Hopkinson pressure bar (SHPB) that could be used during further experiments to measure the dynamic compression strength of concrete. The current study combines experimental, modeling and numerical results, permitting an [...] Read more.

This paper presents an analytical prediction coupled with numerical simulations of a split Hopkinson pressure bar (SHPB) that could be used during further experiments to measure the dynamic compression strength of concrete. The current study combines experimental, modeling and numerical results, permitting an inverse method by which to validate measurements. An analytical prediction is conducted to determine the waves propagation present in SHPB using a one-dimensional theory and assuming a strain rate dependence of the material strength. This method can be used by designers of new SPHB experimental setups to predict compressive strength or strain rates reached during tests, or to check the consistencies of predicted results. Numerical simulation results obtained using LS-DYNA finite element software are also presented in this paper, and are used to compare the predictions with the analytical results. This work focuses on an SPHB setup that can accurately identify the strain rate sensitivities of concrete or brittle materials. Full article

(This article belongs to the Special Issue High Performance Concrete)

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12 pages, 3214 KiB

Open AccessArticle

Effective Bio-Slime Coating Technique for Concrete Surfaces under Sulfate Attack

by Keun-Hyeok Yang, Hee-Seob Lim and Seung-Jun Kwon

Materials 2020, 13(7), 1512; https://doi.org/10.3390/ma13071512 - 26 Mar 2020

Cited by 11 | Viewed by 3170

Abstract

The service life of concretes exposed to sulfate decreases as the concrete body expands due to the formation of gypsum and ettringite. Bacteria-based repair coating layers, which have been studied lately, are aerobic and very effective on the sulfate attack. In this study, [...] Read more.

The service life of concretes exposed to sulfate decreases as the concrete body expands due to the formation of gypsum and ettringite. Bacteria-based repair coating layers, which have been studied lately, are aerobic and very effective on the sulfate attack. In this study, bio-slime repair coating layers were fabricated using bacteria, and chloride diffusion experiments were performed. In addition, the service life of concrete under sulfate attack was evaluated using time-dependent diffusivity and a multi-layer technique. Chloride diffusivity was compared with sulfate diffusivity based on literature review, and the results were used to consider the reduction in the diffusion coefficient. In the analysis results, the service life of concrete was evaluated to be 38.5 years without bio-slime coating layer, but it was increased to 41.5–54.3 years using it. In addition, when the thickness of the bio-slime coating layer is 2.0 mm, the service life can be increased by 1.31–2.15 times if the sulfate diffusion coefficient of the layer is controlled at a level of 0.1 ~ 0.3 × 10⁻¹² m²/s. Eco-friendly and aerobic bio-slime coating layers are expected to effectively resist sulfate under appropriate construction conditions. Full article

(This article belongs to the Special Issue High Performance Concrete)

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13 pages, 4374 KiB

Open AccessArticle

Compressive Behavior Characteristics of High-Performance Slurry-Infiltrated Fiber-Reinforced Cementitious Composites (SIFRCCs) under Uniaxial Compressive Stress

by Seungwon Kim, Seungyeon Han, Cheolwoo Park and Kyong-Ku Yun

Materials 2020, 13(1), 159; https://doi.org/10.3390/ma13010159 - 1 Jan 2020

Cited by 11 | Viewed by 2725

Abstract

The compressive stress of concrete is used as a design variable for reinforced concrete structures in design standards. However, as the performance-based design is being used with increasing varieties and strengths of concrete and reinforcement bars, mechanical properties other than the compressive stress [...] Read more.

The compressive stress of concrete is used as a design variable for reinforced concrete structures in design standards. However, as the performance-based design is being used with increasing varieties and strengths of concrete and reinforcement bars, mechanical properties other than the compressive stress of concrete are sometimes used as major design variables. In particular, the evaluation of the mechanical properties of concrete is crucial when using fiber-reinforced concrete. Studies of high volume fractions in established compressive behavior prediction equations are insufficient compared to studies of conventional fiber-reinforced concrete. Furthermore, existing prediction equations for the mechanical properties of high-performance fiber-reinforced cementitious composite and high-strength concrete have limitations in terms of the strength and characteristics of contained fibers (diameter, length, volume fraction) even though the stress-strain relationship is determined by these factors. Therefore, this study developed a high-performance slurry-infiltrated fiber-reinforced cementitious composite that could prevent the fiber ball phenomenon, a disadvantage of conventional fiber-reinforced concrete, and maximize the fiber volume fraction. Then, the behavior characteristics under compressive stress were analyzed for fiber volume fractions of 4%, 5%, and 6%. Full article

(This article belongs to the Special Issue High Performance Concrete)

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11 pages, 3525 KiB

Open AccessArticle

Tensile Behavior Characteristics of High-Performance Slurry-Infiltrated Fiber-Reinforced Cementitious Composite with Respect to Fiber Volume Fraction

by Seungwon Kim, Dong Joo Kim, Sung-Wook Kim and Cheolwoo Park

Materials 2019, 12(20), 3335; https://doi.org/10.3390/ma12203335 - 13 Oct 2019

Cited by 15 | Viewed by 2615

Abstract

Concrete has high compressive strength, but low tensile strength, bending strength, toughness, low resistance to cracking, and brittle fracture characteristics. To overcome these problems, fiber-reinforced concrete, in which the strength of concrete is improved by inserting fibers, is being used. Recently, high-performance fiber-reinforced [...] Read more.

Concrete has high compressive strength, but low tensile strength, bending strength, toughness, low resistance to cracking, and brittle fracture characteristics. To overcome these problems, fiber-reinforced concrete, in which the strength of concrete is improved by inserting fibers, is being used. Recently, high-performance fiber-reinforced cementitious composites (HPFRCCs) have been extensively researched. The disadvantages of conventional concrete such as low tensile stress, strain capacity, and energy absorption capacity, have been overcome using HPFRCCs, but they have a weakness in that the fiber reinforcement has only 2% fiber volume fraction. In this study, slurry infiltrated fiber reinforced cementitious composites (SIFRCCs), which can maximize the fiber volume fraction (up to 8%), was developed, and an experimental study on the tensile behavior of SIFRCCs with varying fiber volume fractions (4%, 5%, and 6%) was carried out through direct tensile tests. The results showed that the specimen with high fiber volume fraction exhibited high direct tensile strength and improved brittleness. As per the results, the direct tensile strength is approximately 15.5 MPa, and the energy absorption capacity was excellent. Furthermore, the bridging effect of steel fibers induced strain hardening behavior and multiple cracks, which increased the direct tensile strength and energy absorption capacity. Full article

(This article belongs to the Special Issue High Performance Concrete)

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12 pages, 1422 KiB

Open AccessArticle

Experimental Study on the Shrinkage Behavior and Mechanical Properties of AAM Mortar Mixed with CSA Expansive Additive

by Sung Choi, Gum-Sung Ryu, Kyeong-Taek Koh, Gi-Hong An and Hyeong-Yeol Kim

Materials 2019, 12(20), 3312; https://doi.org/10.3390/ma12203312 - 11 Oct 2019

Cited by 11 | Viewed by 2569

Abstract

In this study, a calcium sulfoaluminate-based expansive additive (0%, 2.5%, 5.0%, and 7.5% by the mass of the binder) was added to compensate for the shrinkage of alkali-activated material (AAM) mortar. Modulus of elasticity curves based on the ACI 209 model were derived [...] Read more.

In this study, a calcium sulfoaluminate-based expansive additive (0%, 2.5%, 5.0%, and 7.5% by the mass of the binder) was added to compensate for the shrinkage of alkali-activated material (AAM) mortar. Modulus of elasticity curves based on the ACI 209 model were derived for the AAM mortar mixed with the additive by measuring the compressive strength and modulus of elasticity. Moreover, autogenous shrinkage and total shrinkage were measured for 150 days, and drying shrinkage was calculated by excluding autogenous shrinkage from total shrinkage. For the autogenous and drying shrinkage of AAM mortar, shrinkage curves by age were obtained by deriving material constants using the exponential function model. Finally, shrinkage stress was calculated using the modulus of elasticity of the AAM mortar and the curves obtained using the shrinkage model. The results showed that the calcium sulfoaluminate-based expansive additive had an excellent compensation effect on the drying shrinkage of AAM mortar, but the effect was observed only at early ages when the modulus of elasticity was low. From a long-term perspective, the shrinkage compensation effect was low when the modulus of elasticity was high, and thus, shrinkage stress could not be reduced. Full article

(This article belongs to the Special Issue High Performance Concrete)

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16 pages, 3059 KiB

Open AccessArticle

Effects of a Short Heat Treatment Period on the Pullout Resistance of Shape Memory Alloy Fibers in Mortar

by Min Kyoung Kim, Dong Joo Kim, Young-Soo Chung and Eunsoo Choi

Materials 2019, 12(14), 2278; https://doi.org/10.3390/ma12142278 - 16 Jul 2019

Cited by 12 | Viewed by 2715

Abstract

The feasibility of the crack closure of cementitious composites reinforced with shape memory alloy (SMA) fibers was investigated by performing single-fiber pullout tests. To demonstrate the fast crack closing ability, in this study, a heat treatment (300 °C) was applied for a short [...] Read more.

The feasibility of the crack closure of cementitious composites reinforced with shape memory alloy (SMA) fibers was investigated by performing single-fiber pullout tests. To demonstrate the fast crack closing ability, in this study, a heat treatment (300 °C) was applied for a short time (10 min). A short heat treatment was applied for 10 min, after the slip reached 0.5 mm, to activate the shape memory effects of cold-drawn SMA fibers. Two types of alloys were investigated, NiTi and NiTiNb, with two geometries, either smooth or dog-bone-shaped. During the heat treatment, the pullout stress of the SMA fibers initially decreased due to thermal extension, and then increased after heating for 1–3 min, resulting from the shape memory effects. However, their pullout stress recovery during and after the heat treatment was different for the different alloys and fiber geometries. The NiTi fibers generally produced a higher and faster recovery in terms of their pullout stress than the NiTiNb fibers, while the dog-bone-shaped fibers showed a faster pullout stress recovery than the smooth fibers. Full article

(This article belongs to the Special Issue High Performance Concrete)

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11 pages, 4684 KiB

Open AccessArticle

The Influence of Steel Fiber Tensile Strengths and Aspect Ratios on the Fracture Properties of High-Strength Concrete

by Won-Chang Choi, Kwon-Young Jung, Seok-Joon Jang and Hyun-Do Yun

Materials 2019, 12(13), 2105; https://doi.org/10.3390/ma12132105 - 30 Jun 2019

Cited by 55 | Viewed by 4223

Abstract

Steel fiber embedded in concrete serves to reduce crack development and prevent crack growth at the macroscopic level of the concrete matrix. Steel fiber-reinforced concrete (SFRC) with high compressive concrete strength is affected primarily by the dimensions, shape, content, aspect ratio, and tensile [...] Read more.

Steel fiber embedded in concrete serves to reduce crack development and prevent crack growth at the macroscopic level of the concrete matrix. Steel fiber-reinforced concrete (SFRC) with high compressive concrete strength is affected primarily by the dimensions, shape, content, aspect ratio, and tensile strength of the embedded steel fiber. In this study, double-ended hook steel fiber was used in SFRC with a concrete compressive strength of 80 MPa. This fiber was used for the study variables with two aspect ratios (64, 80) and tensile strength values up to 1600 MPa. The flexural performance of the SFRC specimens was evaluated using crack mouth open displacement tests, and the test results were compared with code provisions. A modified reinforcement index was also used to quantify the flexural performance based on comparisons with fracture energy. Full article

(This article belongs to the Special Issue High Performance Concrete)

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13 pages, 3059 KiB

Open AccessArticle

Influence of Na₂O Content and Ms (SiO₂/Na₂O) of Alkaline Activator on Workability and Setting of Alkali-Activated Slag Paste

by Sung Choi and Kwang-Myong Lee

Materials 2019, 12(13), 2072; https://doi.org/10.3390/ma12132072 - 27 Jun 2019

Cited by 31 | Viewed by 3891

Abstract

The performance of alkali-activated slag (AAS) paste using activators of strong alkali components is affected by the type, composition, and dosage of the alkaline activators. Promoting the reaction of ground granulated blast furnace slag (GGBFS) by alkaline activators can produce high-strength AAS concrete, [...] Read more.

The performance of alkali-activated slag (AAS) paste using activators of strong alkali components is affected by the type, composition, and dosage of the alkaline activators. Promoting the reaction of ground granulated blast furnace slag (GGBFS) by alkaline activators can produce high-strength AAS concrete, but the workability might be drastically reduced. This study is aimed to experimentally investigate the heat release, workability, and setting time of AAS pastes and the compressive strength of AAS mortars considering the Na₂O content and the ratio of Na₂O to SiO₂ (Ms) of binary alkaline activators blended with sodium hydroxide and sodium silicate. The test results indicated that the AAS mortars exhibited a high strength of 25 MPa at 24 h, even at ambient temperature, even though the pastes with an Na₂O content of ≥6% and an Ms of ≥1.0 exhibited an abrupt decrease in flowability and rapid setting. Full article

(This article belongs to the Special Issue High Performance Concrete)

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14 pages, 2901 KiB

Open AccessFeature PaperArticle

Behavior of Colloidal Nanosilica in an Ultrahigh Performance Concrete Environment Using Dynamic Light Scattering

by Douglas Hendrix, Jessica McKeon and Kay Wille

Materials 2019, 12(12), 1976; https://doi.org/10.3390/ma12121976 - 19 Jun 2019

Cited by 19 | Viewed by 4642

Abstract

The dispersion quality of nanosilica (NS) is an essential parameter to influence and control the material characteristics of nanosilica-enhanced concrete. In this research, the dispersion quality of colloidal nanosilica in simulated concrete environments was investigated using dynamic light scattering. A concrete environment was [...] Read more.

The dispersion quality of nanosilica (NS) is an essential parameter to influence and control the material characteristics of nanosilica-enhanced concrete. In this research, the dispersion quality of colloidal nanosilica in simulated concrete environments was investigated using dynamic light scattering. A concrete environment was simulated by creating a synthetic pore solution that mimicked the ionic concentration and pH value of ultrahigh-performance concrete in the fluid state. Four colloidal nanosilica samples were used, ranging in particle sizes from 5 to 75 nm, with differing solid contents and stabilizing ions. It was found that the sodium stabilized 20 nm NS sol remains dispersed at a solid concentration of 2 wt % through a variety of pH values with the inclusion of potassium ions. Calcium ions are a major contributor to the agglomeration of NS sols and only small concentrations of calcium ions can drastically affect the dispersion quality. Full article

(This article belongs to the Special Issue High Performance Concrete)

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Review

Jump to: Research

24 pages, 1553 KiB

Open AccessFeature PaperReview

The Role of Supplementary Cementitious Materials (SCMs) in Ultra High Performance Concrete (UHPC): A Review

by Sungwoo Park, Siyu Wu, Zhichao Liu and Sukhoon Pyo

Materials 2021, 14(6), 1472; https://doi.org/10.3390/ma14061472 - 17 Mar 2021

Cited by 128 | Viewed by 7750

Abstract

Although ultra high-performance concrete (UHPC) has great performance in strength and durability, it has a disadvantage in the environmental aspect; it contains a large amount of cement that is responsible for a high amount of CO₂ emissions from UHPC. Supplementary cementitious materials [...] Read more.

Although ultra high-performance concrete (UHPC) has great performance in strength and durability, it has a disadvantage in the environmental aspect; it contains a large amount of cement that is responsible for a high amount of CO₂ emissions from UHPC. Supplementary cementitious materials (SCMs), industrial by-products or naturally occurring materials can help relieve the environmental burden by reducing the amount of cement in UHPC. This paper reviews the effect of SCMs on the properties of UHPC in the aspects of material properties and environmental impacts. It was found that various kinds of SCMs have been used in UHPC in the literature and they can be classified as slag, fly ash, limestone powder, metakaolin, and others. The effects of each SCM are discussed mainly on the early age compressive strength, the late age compressive strength, the workability, and the shrinkage of UHPC. It can be concluded that various forms of SCMs were successfully applied to UHPC possessing the material requirement of UHPC such as compressive strength. Finally, the analysis on the environmental impact of the UHPC mix designs with the SCMs is provided using embodied CO₂ generated during the material production. Full article

(This article belongs to the Special Issue High Performance Concrete)

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40 pages, 17171 KiB

Open AccessReview

Recent Progress in Nanomaterials for Modern Concrete Infrastructure: Advantages and Challenges

by Karla P. Bautista-Gutierrez, Agustín L. Herrera-May, Jesús M. Santamaría-López, Antonio Honorato-Moreno and Sergio A. Zamora-Castro

Materials 2019, 12(21), 3548; https://doi.org/10.3390/ma12213548 - 29 Oct 2019

Cited by 112 | Viewed by 11032

Abstract

Modern concrete infrastructure requires structural components with higher mechanical strength and greater durability. A solution is the addition of nanomaterials to cement-based materials, which can enhance their mechanical properties. Some such nanomaterials include nano-silica (nano-SiO₂), nano-alumina (nano-Al₂O₃), [...] Read more.

Modern concrete infrastructure requires structural components with higher mechanical strength and greater durability. A solution is the addition of nanomaterials to cement-based materials, which can enhance their mechanical properties. Some such nanomaterials include nano-silica (nano-SiO₂), nano-alumina (nano-Al₂O₃), nano-ferric oxide (nano-Fe₂O₃), nano-titanium oxide (nano-TiO₂), carbon nanotubes (CNTs), graphene and graphene oxide. These nanomaterials can be added to cement with other reinforcement materials such as steel fibers, glass, rice hull powder and fly ash. Optimal dosages of these materials can improve the compressive, tensile and flexural strength of cement-based materials, as well as their water absorption and workability. The use of these nanomaterials can enhance the performance and life cycle of concrete infrastructures. This review presents recent researches about the main effects on performance of cement-based composites caused by the incorporation of nanomaterials. The nanomaterials could decrease the cement porosity, generating a denser interfacial transition zone. In addition, nanomaterials reinforced cement can allow the construction of high-strength concrete structures with greater durability, which will decrease the maintenance requirements or early replacement. Also, the incorporation of nano-TiO₂ and CNTs in cementitious matrices can provide concrete structures with self-cleaning and self-sensing abilities. These advantages could help in the photocatalytic decomposition of pollutants and structural health monitoring of the concrete structures. The nanomaterials have a great potential for applications in smart infrastructure based on high-strength concrete structures. Full article

(This article belongs to the Special Issue High Performance Concrete)

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