Use Of High Performance Concrete Research Articles

Seismic performance evaluation of precast post-tensioned high-performance concrete frame beam-column joint under cyclic loading

Precast concrete structures have developed rapidly because they meet the requirements of green and low-carbon social development. In this paper, a precast post-tensioned high-performance concrete frame beam-column joint was proposed, and the low-cycle reversed load test was performed on the four proposed joints. The main differences between the four joints are the different prestress values applied by the joints and whether the beam-column joint is provided with L-shaped steel. The seismic performance indexes such as hysteresis curve, stiffness degradation, deformation capacity, energy dissipation capacity and residual deformation of each node were obtained through experiments. By comparing various seismic performance indicators, it could be found that the use of high-performance concrete could effectively avoid the phenomenon of local crushing of concrete due to excessive prestressing. At the same time, it was found that the setting of L-shaped steel plate at the beam-column junction could effectively avoid the early damage at the beam-column junction. On the basis of the test, the three-line restoring force model of the joint was established by the method of experimental regression analysis. The model could better reflect the stress situation of each stage of the joint. Based on the experimental and theoretical analysis, the finite element analysis model of the joint was established, and the model calculation results were in good agreement with the experimental results.

The use of high-performance concrete in dam construction

The use of high-performance concrete in dam construction

Investigation of the Failure Modes of Textile-Reinforced Concrete and Fiber/Textile-Reinforced Concrete under Uniaxial Tensile Tests

Recently, innovations in textile-reinforced concrete (TRC), such as the use of basalt textile fabrics, the use of high-performance concrete (HPC) matrices, and the admixture of short fibers in a cementitious matrix, have led to a new material called fiber/textile-reinforced concrete (F/TRC), which represents a promising solution for TRC. Although these materials are used in retrofit applications, experimental investigations about the performance of basalt and carbon TRC and F/TRC with HPC matrices number, to the best of the authors' knowledge, only a few. Therefore, an experimental investigation was conducted on 24 specimens tested under the uniaxial tensile, in which the main variables studied were the use of HPC matrices, different materials of textile fabric (basalt and carbon), the presence or absence of short steel fibers, and the overlap length of the textile fabric. From the test results, it can be seen that the mode of failure of the specimens is mainly governed by the type of textile fabric. Carbon-retrofitted specimens showed higher post-elastic displacement compared with those retrofitted with basalt textile fabrics. Short steel fibers mainly affected the load level of first cracking and ultimate tensile strength.

The impact of specimen size and alteration of fiber configuration on the flexural performance of high-performance concrete

This study examines the impact of fiber configuration and specimen size on the flexural performance and thus the energy absorption capacity of moderate and high-performance fiber reinforced concrete (FRC). A total of 180 specimens were produced using hooked-end steel fibers in lengths of 30-mm and 60-mm, and 54-mm long macro synthetic fibers. The specimens, in the form of small beams (75 × 75 × 320 mm3), large beams (150 × 150 × 750 mm3), and square panel specimens (600 × 600 × 100 mm3), were tested in accordance with EN14488-5 and ASTM C1609 standards. The results showed that as the amount of fibers increased, the flexural performance of FRC improved significantly, provided that precautions were taken to avoid mixing and placement issues when using higher amounts of fibers. 60-mm hooked-end steel fibers had the best performance among all the fibers tested with higher ultimate and post-cracking flexural strengths. 54-mm synthetic fibers seemed to be a cost-effective alternative with comparable energy absorption performance when compared to 30-mm hooked-end steel fibers. Small beams had a slightly higher ultimate (∼15% more) and post-cracking (∼35% more) flexural strengths than large beams, but the equivalent flexural strength ratio was not significantly affected by the specimen size. No clear relationship between fiber dosage and ultimate flexural strength was observed, but a relationship was observed between the fiber dosage and the equivalent flexural strength ratio, with R2 values ranging from 65% to 93% depending on the concrete matrix and the fiber type. The study also showed strong correlations (R2>91%) between the energy absorption capacity of plate specimens and beam specimens, suggesting that plate specimens can be used to reduce the time and effort required in testing during trial batches and product development. Finally, the use of high-performance concrete does not seem to be necessary, when the target is to improve the energy absorption capacity of FRC, particularly at low fiber volumes.

Theoretical Analysis of Ultimate Main Span Length for Arch Bridge

The advancement of construction techniques and high-performance sustainable materials enables the increase of span length for arch bridge. It is of great importance to study the theoretical ultimate span length of arch bridge. Based on the parabolic and catenary arch axes, the analytical solutions of ultimate span length of arch bridge are solved using theoretical derivation accounting for the strength, in-plane stability and out-plane stability conditions, respectively. Then, the use of high-performance concrete, reactive powder concrete and high-strength steel is considered to study the relationship between theoretical ultimate span length and rise-span ratio as well as material strength for concrete and steel arch bridges. The results show that the theoretical ultimate span length derived by catenary arch axis is smaller by about 2–6% than that obtained by parabolic arch axis, but the difference is insignificant. When the rise-span ratio is 1/5, the theoretical ultimate span length for concrete arch bridge using R200 reactive powder concrete can reach 2000 m (2161 m for catenary arch axis and 2099 m for parabolic arch axis) while the main span of steel arch bridge using Q690 high-strength steel can be longer than 2500 m (2948 m for catenary arch axis and 2865 m for parabolic arch axis).

PENGARUH SUPERPLASTICIZER POLYMER TERHADAP KUAT TEKAN BETON MUTU TINGGI

In construction field, the use of high performance concrete is essential for pre-cast and pre-stress concrete production where the addition of chemical admixture was found effectively contributes in strength. This research presents the results of using Superplasticizer polymer type Ligno C-165 in making high strength concrete. The percentage use of this material is 0.25%, 0.5%, 0.75%, 1%, 1.25% and 1.5% by weight of cement. The concrete samples were tested at the age of 3, 7, 14, 21 and 28 days after water curing. The results show that the addition of 1.5% SP increased the strength of concrete at 28 days with strength value of 64.97 MPa or 166.08% stronger than the target strength of f’c=40 MPa. This is an indication that the increase of Superplasticizer polymer type Ligno C-165 dosage in concrete will also increases the strength that can be due to the effect of SP in reducing the water content that may produces denser matrix concrete with less volume of voids resulted in improving the properties of high strength concrete. From the results, the application of this mixture proportions could be used for producing building construction elements in the field of civil engineering.

Experimental Study of the Thermal and Dynamic Behaviors of Polypropylene Fiber-Reinforced Concrete

The wide use of high-performance concrete (HPC) makes it essential to study its dynamic and thermal behavior. In this study, polypropylene fiber-reinforced high-performance concrete was developed and a series of tests were carried out to obtain its mechanical and thermal properties. Since high-strength HPC has previously been studied intensively, only low-strength HPC—i.e., C30, C40, and C50—was studied in this research. The split Hopkinson pressure bar (SHPB) was employed to carry out the dynamic tests of the HPC under various loading rates and the principles of the SHPB were introduced in detail. Then, the polypropylene fiber-reinforced HPCs were heated to various high temperatures and measures were taken to keep the temperatures relatively constant. It was found that at temperatures lower than 100 °C, the specimen could still be kept in its entirety, although many fractures were produced in the HPC specimen under dynamic loading conditions. However, it was found that at temperatures higher than 200 °C, all the HPC samples were smashed into fragments. In addition, the HPC’s compressive strength was found to be significantly influenced by the temperature. At temperatures lower than 300 °C, the HPC’s compressive strength was found to increase with increases in temperature. At temperatures higher than 300 °C, the HPC’s compressive strength was found to decrease with increases in temperature.

Effect of Supplementary Materials on the Autogenous Shrinkage of Cement Paste.

In recent years more and more attention has been given to autogenous shrinkage due to the increasing use of high-performance concrete, which always contains supplementary materials. With the addition of supplementary materials—e.g., fly ash and blast furnace slag—internal relative humidity, chemical shrinkage and mechanical properties of cement paste will be affected. These properties significantly influence the autogenous shrinkage of cement paste. In this study, three supplementary materials—i.e., silica fume, fly ash and blast furnace slag—are investigated. Measurements of final setting time, internal relative humidity, chemical shrinkage, compressive strength and autogenous deformation of the cement pastes with and without supplementary materials are presented. Two water-binder ratios, 0.3 and 0.4, are considered. The effects of different supplementary materials on autogenous shrinkage of cement paste are discussed.

New findings in the research of concrete fatigue

An increasing use of high-performance concretes—accompanied by an increasing slenderness of structures—will require a specific fatigue design more often. This holds true especially for structures having to resist very high numbers of load cycles throughout their operating service life. Generally, these are long spanning, slender bridge structures, structures for wind energy turbines or machine foundations. For standard structures—and most common bridges—the fatigue resistance of concrete does not become decisive in design. Before the introduction of Eurocode 2 and CEB/FIP Model Code 1990—with design concepts based on Wöhler-curves—research regarding concrete fatigue was rare and often focused on counting the bearable number of cycles until failure. However, knowledge at time on the gradual deterioration phenomena, which finally results in a fatigue failure, was hardly available. In the time since, design rules were cautiously corrected, for example, in fib Model Code 2010, but, knowledge on the mechanisms of fatigue deterioration is still very limited. With the development of concretes with higher compressive strengths, more slender structures have become possible, in which the ratio of the dead load to the variable loads, relevant for fatigue, has substantially decreased. These concretes often show compressive strengths exceeding 100 MPa, outstanding workability, small maximum grain sizes and additionally contain fiber reinforcement. These concretes are hardly comparable to conventional concrete mixtures. For this reason, research about the phenomena of deterioration of high-performance concrete was intensified over the last decade. Currently, a large joint research project is the Priority Programme 2020 “Cyclic Deterioration of High-Performance Concrete in an Experimental-Virtual Lab” which is funded by the German Research Foundation (DFG). Within various tandem-projects experts in material science, building materials technology and numerical modeling are working together to identify and characterize the damage mechanisms under fatigue loading and to develop quantitative prediction models. On the occasion of the 65th birthday of Professor Ludger Lohaus, Institute of Building Materials Science at Leibniz University of Hannover, Germany, who is the initiator and coordinator of the aforementioned DFG Priority Programme 2020, this issue of “Structural Concrete” is partly dedicated to fatigue and cyclic behavior of concrete and concrete structures. Professor Lohaus has been very active in the research on concrete fatigue and has driven it forward in many regards. It has been his continuing effort to transfer fundamental research results into practice (especially in structures for offshore wind-energy) and standardization, whether for Eurocode 2, fib Model Code 2010 or for the current preparations for fib Model Code 2020. The undersigned congratulate him very warmly on his birthday—also on behalf of the involved researchers of the DFG Priority Programme 2020—and we wish him all the best for the future, especially good health. We hope you enjoy reading this issue and wish you new insights and inspirations. The authors are members of the Programme Committee of the DFG Priority Programme 2020 “Cyclic Deterioration of High-Performance Concrete in an Experimental-Virtual Lab,” funded by the German Research Foundation (DFG).

Eco-efficient low binder high-performance self-compacting concretes

The use of high-performance concrete (HPC) is widespread as an eco-efficient building solution because it provides greater durability and, hence, a longer lifetime than conventional concrete, reducing the need for repairs and demolitions. In addition, HPCs require lower binder contents per unit of compressive strength. However, self-compacting HPCs (HPSCCs) generally require high binder contents to ensure the fresh state stability of the concretes, which could hinder the ecological advantage. Thus, this work aimed to produce HPSCCs with low binder contents. A mix design method was proposed to optimise the material proportions. A fine fly ash was used to replace Portland cement from 0 to 30%. The rheological properties of the SCCs were evaluated by the workability tests slump flow, T500, V-funnel, L-box and VSI. Compressive strength, resistance to chloride ion penetration, volume of permeable voids and capillary water absorption were determined at 28 and 91 days. Finally, the CO2 intensity (kg CO2/m3·MPa) of the mixtures produced was estimated and compared to those of HPSCCs reported in the literature. The mix design method allowed for the production of SCCs with 365 kg of binder/m3 of concrete, with slump flow of 700 ± 25 mm and stable in the fresh state (VSI of 0 or 1). The fly ash-containing concretes showed compressive strengths up to 59 MPa at 28 days (10% fly ash) and 71 MPa at 91 days (20 and 30% fly ash), with good indicators of durability: down to 403 Coulombs for RCPT and up to 41.8 kΩ·cm for surface electrical resistivity. The CO2 intensity of the concretes produced are among the lowest reported in the literature for HPSCCs (down to 4.7), together with the lowest binder content reported for this type of concrete (365 kg/m3 of concrete).

Thermal-Humidity Parameters of 3D Printed Wall

The purpose of the external walls is to secure the internal microclimate of the building. External walls not only must have proper strength and durability but also prevent heat escape, overheating during summer, protect from noise and increase of humidity. The main parameter that describes the thermal properties of external walls is the heat transmission coefficient U [W/(m2⋅K)] determined in accordance with EN ISO 6946:2008. One of most recent technology of constructing walls is the additive manufacturing. The aim of the study is to determine the thermal properties of wall printed with use of High Performance Concrete and insulated with mineral wool. The study determines the temperature and vapour pressure inside the wall and presents calculations of thermal factor. The study compares the characteristics of traditional walls with 3D printed elements. The tests have shown that insulating printed structures does not pose any difficulty. Corrugated structure of printed walls increases the adhesion of adhesive mortar. Proposed tests are the starting point for further studies on the thermal-humidity of 3D printed structures. The main goal is to propose a solution for cheap, efficient insulation technology for 3D printed structures.

Challenges and opportunities for assessing transport properties of high-performance concrete

In this paper, a review of techniques is given so that both, the challenges and opportunities for assessing transport properties of high-performance concrete, are highlighted. A knowledge of performance of structural concrete is required for design and compliance purposes. One driving force for the use of high performance concretes (HPC) is enhanced durability yet it would be wrong to assume that all HPCs can deliver the desired performance level. In situ characterisation of the permeation properties of concrete is the most viable means for assessing durability and has become increasingly important over the past 20 years. A variety of methods exist that provide a range of parameters, e.g. air permeability, water absorption rate, sorptivity and chloride migration coefficient.

A hierarchical nano to macro multiscale analysis of monotonic behavior of concrete columns made of CNT-reinforced cement composite

There is an increasing demand for the use of high performance concrete in buildings to reduce significant damage due to extreme loadings. Carbon nanotubes (CNT) with their superior properties are among new materials, which can be used in concrete members. A hierarchical multiscale approach is adopted in this research to obtain the monotonic behavior of CNT-reinforced concrete, noting that, to the best knowledge of the authors, no experimental results are available for its monotonic behavior. At the nano scale, the mechanical properties of carbon nanotubes (CNT) is derived by the molecular dynamics approach. Afterwards, a micromechanical finite element method is adopted at the micro scale to determine the stress-strain curve of CNT-reinforced cement. The whole structure of a concrete sample, including all its major phases, is simulated at the meso scale by the finite element method. Finally, at the macro scale, the monotonic behavior of a concrete column made of CNT-reinforced cement is studied. The results of simulations indicate that by increasing the volume fractions of CNTs, the energy absorption capacity, the curvature ductility and the ultimate moment capacity of the CNT-reinforced concrete columns increase significantly.

Thin Lightweight Panels Made of Textile Reinforced Concrete

Use of high performance concrete with reinforcement made of technical textile is increasing and new applications are being found. This paper presents new technology for the lightening of the panels made of textile reinforced concrete, which is being developed. The main focus of this research is to produce concrete elements suitable for use as facade panels with the least possible weight and environmental impact. Mechanical characteristics were measured on testing specimens with thickness of 18 mm with lightening representing 47% of their volume. Minimum thickness of concrete was 4 mm and therefore the reinforcement was covered by approximately 1.5 mm of concrete matrix. The strength of experimental test panels was measured in four-point bending stress test. Due to one-sided lightening and asymmetrical cross-section therefore, the tests were performed in both directions. For better interpretation of the results were the specimens of lightened panels tested alongside non-lightened specimens with the same thickness. Based on measured values, maximal dimensions of lightened facade panels were designed.

Tensile creep and cracking resistance of concrete with different water-to-cement ratios at early age

With the widely use of high-performance concrete, the lower and lower water-to-cement (w/c) ratio is applied in practice. This low w/c ratio can offer high strength and low permeability, however, coming with other drawbacks, such as high self-desiccation and high temperature rise, both of which can increase the early-age cracking potential of concrete. Creep is important to evaluate the early-age cracking resistance of concrete. Although studies on the influence of w/c ratio on the creep of mature concrete have been conducted, investigations on the influence of w/c ratio on the early-age tensile creep remain lacking. Therefore, investigations on the influence of w/c ratio on the tensile creep and cracking resistance of early-age concrete must be conducted. Experimental studies on the influence of w/c ratio (0.33, 0.40, and 0.50) on the temperature change, autogenous shrinkage, restrained stress, tensile creep, and cracking resistance of early-age concrete under adiabatic condition and at full restraint degree were conducted using Temperature Stress Test Machine. The test results indicate that (1) the temperature rise under adiabatic condition increased by 32.6%, and 74.2% when w/c ratio decreased from 0.50 to 0.40, and 0.33, respectively; (2) the restrained tensile stress rate under adiabatic condition and at full restraint degree increased by 16.7%, and 33.3% when w/c ratio decreased from 0.50 to 0.40, and 0.33, respectively; (3) the early-age specific basic tensile creep and basic tensile creep/shrinkage under adiabatic condition and at full restraint degree increased with the decrease of w/c ratio; (4) the early-age cracking potential under adiabatic condition and at full restraint degree increased with the decrease of w/c ratio according to the integrated criterion.

Effects of High Temperature on the Properties of High Performance Concrete (HPC)

Recent years have seen a tendency towards increasingly slender structures designed with the use of high performance concrete. Application of high performance concrete is also growing in tunnel construction. One of the most important challenges is to control explosive spalling of concrete and the method recommended by Eurocode 2 is addition of polypropylene fibres to the mix. The purpose of the research described in this paper was to evaluate the changes of the physical and mechanical properties of HPC exposed to the effect of high temperature. The tests were carried out on three types of high-performance concrete: air-entrained concrete, polypropylene fibre-reinforced concrete and reference concrete having constant water/cement ratio. The properties of hardened concrete including compressive strength, tensile splitting strength, flexural strength and E-modulus were studied. The latter tests were carried out on both on concrete cured at 20̊C and concrete subjected to high-temperature conditions at 300̊C, 450̊C and 600̊C. The results enabled us to evaluate the effect of high-temperature conditions on the properties of high-performance concrete and compare the effectiveness of the two methods designed to improve the high-temperature performance of the concrete: addition of polypropylene fibres and entrainment of air.

Use of alternative waste materials in producing ultra-high performance concrete

In a corrosive environment similar to that of the Arabian Gulf, use of high-performance concrete is one of the options to ensure a target service life of concrete structures. However, in absence of good quality coarse aggregates, it is a challenging task to produce high-performance concrete. Recently, the possibility of producing ultra-high-performance concrete (UHPC) has been widely reported in the literature. UHPC is produced without coarse aggregates at very low water to cementitious materials ratio, high amounts of cement, mineral admixtures, and superplasticizer along with fine quartz sand as aggregate, quartz powder as micro-filler, a nd steel fibres for fracture toughness. In the present work, an effort was made to utilize local waste materials as alternative mineral admixtures and local dune sand as aggregate in producing different UHPC mixtures without addition of quartz powder. The mechanical properties, shrinkage, and durability characteristics of the UHPC mixtures were studied. Test results indicate that it is possible to produce UHPC mixtures using alternative waste materials, which would have targeted flow, strength, toughness, and resistance against reinforcement corrosion. The information presented in the paper would help in optimum selection of a mixture of UHPC considering the availability of local materials, exposure conditions and structural requirements.

Durability of High Performance Concrete (HPC) Subject to Fire Temperature Impact

AbstractIn the recent years a tendency for design of increasingly slender structures with the use of high performance concrete has been observed. Moreover, the use of high performance concrete in tunnel structures, subject to high loads with possibility of extreme loads occurrence such as fire, has an increasing significance.Presented studies aimed at improving high performance concrete properties in high temperature conditions (close to fire conditions) by aeration process, and determining high temperature impact on the concretes features related to their durability.In this paper it has been proven that it is possible to obtain high performance concretes resistant to high temperatures, and additionally that modification of the concrete mix with aerating additive does not result in deterioration of concrete properties when subject to water impact in various form.

Influence of Supplementary Cementitious Materials on Shrinkage, Creep, and Durability of High-Performance Concrete

Use of high performance concrete (HPC) with locally available supplementary cementitious materials (SCMs) has been increasing the world over. The difficulties associated with different indigenous cementitious materials lies in variation in its physical/chemical/mineralogical properties which may greatly influence the time-dependent properties like shrinkage and creep in HPC. A reasonably accurate estimation of actual shrinkage and creep is an important design parameter to ensure that structures built in such concrete perform satisfactorily especially in long-term, and it does not exhibit unduly large deformation or any distress like cracking during its anticipated service life. Further, very old and limited percentage of NU-ITI/RILEM data are for concrete with SCMs, and, hence, all the existing prediction models based on regression analysis of entire/partial data may not ensure satisfactory prediction of shrinkage and creep of modern HPC, in general, and especially for local geographic conditions. Towards this, four different HPC mixes of M50 grade using different SCMs, namely fly ash (FA), silica fume (SF), and ground granulated blast-furnace slag (GGBS) along with ordinary portland cement (OPC) have been prepared to investigate the microstructural and micromechanical concrete properties.

Sandwich panels with high performance concrete thin plates at elevated temperatures: numerical studies

Performance of conventional load-carrying sandwich structures made of concrete can be improved by the use of high performance concrete (HPC) plates of thin sections (30 mm), linked by shear connectors ensuring the composite behaviour of the structure. This paper proposes the application of a coupled heat and mass transfer (HMT) model to HPC thin plates to study their behaviour at elevated temperatures, predicting temperature and pore pressure distributions. The same model was applied to a sandwich structure including thin plate, stiffening rib, and insulation layer. A last simulation concerned HMT modelling and elastic stress analysis with non-linear temperature effects of a full size loaded sandwich wall, qualitatively assessing the location of critically stressed zones. Modelling output was compared to published experimental results. The model reproduced experimental temperature recordings satisfactorily, except phase changes of water at low heating rates. It was suggested that the function governing moisture evolution with temperature and pressure should be updated for HPC. Pore pressure was found critical for sandwich structures due their higher temperatures. Adding polypropylene (PP) fibres for pressure release is recommended. Stress analysis showed the stiffening rib assumes the major load-carrying role. The thin plate was found largely sensitive to heat, its thermal bowing restrained by shear connectors creating high localised tensile stresses. It was suggested to anchor the shear connectors in the ribs. Geometric discontinuities were also found critical; therefore separation of rib and plate is advised for hazardous situations such as fire events.