Performance Of Concrete Materials Research Articles

Correlating strength of concrete to its early-age temperature rise

Compressive strength is the most commonly used property for characterising the performance of concrete materials. In this study, semi-adiabatic temperature evolutions and compressive strength developments of a series of mortar and concrete mixtures were experimentally investigated. In order to predict compressive strength, it was correlated to the initial temperature rise induced by early-age hydration. The results indicate that both properties are strongly dependent on the raw materials and the water to cementitious materials ratio. Estimated results of temperature rise and strength from the modified equations match well with the measured data. A linear relationship between compressive strength and the peak value of temperature rise is developed and presented. The linear correlation exists for all mixture components and proportions of concrete materials in this study. In conclusion, predicting the strength of concrete materials from their early-age hydration-induced temperature evolutions is enabled.

Performance Based Evaluation of Concrete Strength under Various Curing Conditions to Investigate Climate Change Effects

Recently, the manifestation of global warming-induced climate change has been observed through super typhoons, heavy snowfalls, torrential rains, and extended heat waves. These climate changes have been occurring all over the world and natural disasters have caused severe damage and deterioration of concrete structures and infrastructure. In an effort to deal with these problems due to extreme and abnormal climate changes, studies have been conducted to develop construction technologies and design guidelines. Nevertheless, study results applicable to construction sites continue to be ineffective and insufficient. Therefore, this study proposes ways to cope with climate change by considering the effect of concrete curing condition variations on concrete material performance. More specifically, the 3-, 7- and 28-day compressive and split tensile strength properties of concrete mix cured under various climatic factors including temperature, relative humidity, wind speed, and sunlight exposure time were evaluated to determine whether the concrete meets the current design requirements. Thereafter, a performance based evaluation (PBE) was performed using satisfaction probabilities based on the test values to understand the problems associated with the current mix proportion design practice and to identify countermeasures to deal with climate change-induced curing conditions.

Development of lower shrinkage and reflection material for concrete pavement

This study focuses on the development of a high performance concrete material for concrete paving with lower shrinkage and reflection of sunlight. Based on a literature review, alternative mixes for paving are suggested. The results of the laboratory experiments indicated that the contrast and reflectivity values of the concrete mixes with a variety of black pigment do not significantly vary provided that the mix contains 3% black pigment. When optimised aggregate gradation (OAG) is incorporated into the mix design, the strength and freeze–thaw resistance of the concrete significantly improves. In addition, the use of fly ash in the mix design reduces the dry shrinkage and alkali–silica reaction of the concrete and improves its resistance to the permeation of chloride ion. In summary, the mix design that uses fly ash (25% replacement), black pigment (3% addition) and OAG is found to be the most effective mix for concrete pavement.

Effects of an AMPS-modified polyacrylic acid superplasticizer on the performance of concrete materials

Effects of an AMPS-modified polyacrylic acid superplasticizer on the performance of concrete materials

Frost Damage Mechanism Analysis and Preventive Measures of Bridge

In order to guarantee the safety and smooth of road traffic in low temperature season, deicing salt is usually adopted to solute the problem of bridge deck snow. However, the frequent use of de-icing salt causes the salt frozen erosion damage of concrete, at the same time, it induces to internal corrosion of steel bars and concrete material performance, furthermore, it will also result in the bridge structure durability degradation, shorten the service life of the bridge. Aiming at this phenomenon, this paper analyzes the mechanism of concrete frost damage, and put forward the corresponding prevention measures.

Effect of Steel Fiber on Comprehensive Performance of Concrete Materials

This paper presents the results on the influence of steel fiber on the performance of concrete materials. The performance of steel fiber reinforced concrete was studied through mechanical testing, frost resistance, carbonation and impermeability testing. Experimental results showed that steel fibers can improve compressive and flexural strengths, and especially can significantly improve flexural strength. Frost resistance can also be improved, and the higher the volume of steel fibers added, the more the freeze-thaw cycles that concrete could resist. Furthermore, steel fiber can not only slow down the carbonation rate indirectly, but also improve the impermeability of concrete, and impermeability enhanced with the increase of steel fiber.

Special Issue on Sustainable Materials and Structures

This special issue consists of extended and revised versions of 10 papers selected from those presented at the First International Conference on Performance-Based and Life-Cycle Structural Engineering (PLSE 2012). The conference was co-organized by the Faculty of Construction and Environment (FCE) and the Research Institute for Sustainable Urban Development (RISUD) of Hong Kong Polytechnic University (PolyU), and was held on December 5–7, 2012, in Hong Kong. PLSE 2012 was organized as the first conference in a series to provide an international platform for scientific exchange and international cooperation in the areas of performance-based and life-cycle structural engineering for a wide range of structures, such as building, bridges, and offshore platforms. Both performance-based and life-cycle structural engineering are important areas of structural engineering research; they have also gained gradual acceptance in structural engineering practice. In particular, performance-based life-cycle structural engineering, based on a full integration of these two areas, offers an exciting new direction for structural engineering within the context of sustainable urban development. The conference program comprised approximately 230 presentations, including nine keynote lectures and 34 invited lectures. Eleven mini-symposia on specialized topics were also organized as part of the conference. As one of the six journal special issues that have arisen from PLSE 2012, this special issue is focused on the topic of “sustainable materials and structures” and primarily addresses the following topics: long-term or lifecycle performance of concrete materials and structures, longterm performance of structures incorporating fiber-reinforced polymer (FRP) composites, and recycling of materials for structural purposes. As Guest Editors of this special issue, we would like to acknowledge the contributions of many individuals to the successful compilation of this special issue. In particular, we would like to thank all authors for their careful preparation of the papers and the reviewers for their prompt and high quality reviews. Sincere thanks are also due to Professor Antonio Nanni, Editor-in-Chief of Journal of Materials in Civil Engineering, for his kind support during the development of this special issue.

Enhancement of Ultrahigh Performance Concrete Material Properties with Carbon Nanofiber

Ultrahigh performance concrete (UHPC) realized distinctly high mechanical, impermeability, and durability characteristics by reducing the size and content of capillary pore, refining the microstructure of cement hydrates, and effectively using fiber reinforcement. The dense and fine microstructure of UHPC favor its potential to effectively disperse and interact with nanomaterials, which could complement the reinforcing action of fibers in UHPC. An optimization experimental program was implemented in order to identify the optimum combination of steel fiber and relatively low-cost carbon nanofiber in UHPC. The optimum volume fractions of steel fiber and carbon nanofiber identified for balanced improvement of flexural strength, ductility, energy sorption capacity, impact, and abrasion resistance of UHPC were 1.1% and 0.04%, respectively. Desired complementary/synergistic actions of nanofibers and steel fibers in UHPC were detected, which were attributed to their reinforcing effects at different scales, and the potential benefits of nanofibers to interfacial bonding and pull-out behavior of fibers in UHPC. Modification techniques which enhanced the hydrophilicity and bonding potential of nanofibers to cement hydrates benefited their reinforcement efficiency in UHPC.

Research on the performance of concrete materials under the condition of freeze-thaw cycles

Durability of concrete has been a social concern due to the poor performance of concrete caused by various environmental conditions. This paper aims to study the effects of damage caused by freeze-thaw cycles which often appeared in cold areas on the performance of concrete with polypropylene fibres, such as strength, carbonation depth and chloride ion diffusion. Concrete samples with different degrees of damage were produced by different freeze-thaw cycles. The concrete sample shows great water absorption after freeze-thaw cycles. Due to damage by freeze-thaw cycles, the total pore volume, porosity and average pore diameter of concrete samples damaged by freeze-thaw cycles were generally larger than that of normal concrete samples. Compressive strength and splitting strength of concrete exposed to freeze-thaw cycles decreased with the number of freeze-thaw cycles and greater damage caused higher loss of strength, especially for the splitting tensile strength. The carbonation depth of the concrete after freeze-thaw cycles was also greater than that of the concrete before freeze-thaw cycles. Chloride ion diffusion rates were evaluated using the free chloride ion concentration titration method and the steady state migration testing method. Results indicated that freeze-thaw cycles could accelerate chloride ion diffusion rates. More severe concrete damage results in greater chloride diffusion.

Review of Mechanical Properties and Durability of Concrete Containing Nano-Particles

As a kind of high performance concrete material in the construction of structure engineering, the concrete containing nanoparticles has been paid more and more attention to and used in the field of high and long span buildings because of good mechanical performance and durability performance. In order to in-depth understand the characteristic of the concrete containing nanoparticles and promote the application of the concrete containing nanoparticles in practical engineering, a series of research works on the mechanical properties and durability of the concrete containing nanoparticles were summarized based on the current study results. Furthermore, the research trend of the concrete containing nanoparticles was presented.

The New Technique of Evaluation of the Early-Age Shrinkage Property of Concrete Material for Airport Pavement by Eddy Current

This article introduces one new measurement technology for evaluation of the early age shrinkage performance of concrete material without constraint conditions. Its exercise of eddy current method could make the airport pavement concrete material tested accurately during concrete early-age from pouring, when the pavement concrete does not harden. It also can evaluate the effects of the influencing factors on the concrete early-age shrinkage, such as fly ash, admixture, and fiber. By this method, the Shrinkage performance of different concrete material can be evaluated when concrete property design for airport pavement is making.

Influence of polypropylene fibre on the mechanical performance and durability of concrete materials

Concrete is the most commonly used structural material in the world. This paper evaluated the influence of polypropylene fibre on the performance of concrete materials. The performance of concrete materials was determined by testing the compressive, flexural, and splitting tensile strengths, as well as the freeze-thaw resistance, impermeability, and restrained shrinkage cracking. These results indicate that the use of polypropylene fibres can significantly improve the flexural and splitting tensile strengths of concrete materials. The freeze-thaw resistance and impermeability were improved due to the addition of polypropylene fibre. When the volume of the added polypropylene fibres was increased, the concrete was able to resist more freeze-thaw cycles. Polypropylene fibres can also reduce cracking, and improve the cracking resistance of concrete materials.

Effect of Steel Fiber on the Performance of Concrete Materials

This paper presents the results of testing performed to evaluate the influence of steel fiber on the performance of concrete materials. The performance of concrete materials was studied through frost resistance, carbonation testing and restraint cracking testing. Experimental results show that the steel fibers can improve the frost resistance and carbonation of concrete, compared with plain concrete. Steel fibers can also reduce cracking, and improve the cracking resistance of concrete materials.

Study on the Mechanical Property of Concrete Materials under High Temperature (Fire)

The performance of concrete materials under high temperature is more complex than that under room temperature. This paper, by analyzing the mechanical property of concrete materials under high temperature(fire), probes into the changing law of the concrete materials' compressive strength under different temperatures (16 °C-800 °C) and different static placing time and makes a comparison on the concrete materials' strength between natural cooling and water cooling; illustrates the relationships of concrete materials' compressive strength and temperature, holding time and cooling and other factors under high temperature(fire).

Dumbbell Test Method for Evaluation of the Early Age Cracking Property of Concrete Material by Stress Risers

This article develops one new test technology, dumbbell test method, for evaluation of the early age cracking property of Concrete Material under constraint conditions. Its exercise of stress risers could lead concrete to crack quickly, providing a quick method to evaluate the early age crack performance of concrete material and to perform simulated test at job site conveniently. By this method, the anti-cracking performance of different concrete material can be evaluated quickly in the construction site.

Development of satisfaction curves to evaluate concrete mix design performance using a Bayesian probabilistic method

Due to the restrictions of the current prescriptive design methods and standards, structural and material engineers sought to find an innovative design method to implement creative and novel approaches in designing. One type of design method receiving a keen interest in civil engineering field is performance based design (PBD) method. Presently, PBD is used in seismic design of structures and is specified in the code standards of earthquake resistant design. One specific approach in structural seismic design and damage evaluation is called fragility method developed by Shinozuka. Fragility method is developed based on Bayesian method, which is presented as the conditional probability of exceeding some limit state (minor, moderate, major, and collapse) for a given ground motion. In this study, the focus is to apply the Bayesian approach for the evaluation of concrete mixture design in assessing concrete material performance based on selected conditional parameters (i.e., safety, durability, etc.). The performance based evaluation of concrete mix proportion is presented as a satisfaction probability percentage (e.g., 0–100%) as a function of specified material parameter (i.e., water, water-to-cement ratio, cement content, etc.) for a specified performance criterion value (i.e., compressive strength, slump, elastic modulus, etc.). This relationship curve is titled satisfaction curve (SC). The paper presents a detailed explanation of developing and drawing SC based on Bayesian method, an example of application of SC, and result comparisons between the results obtained using our SC method with ACI 214R-02 normal distribution probability method. The result verification shows that concrete mix proportion performance evaluation using SC is reliable and the difference is within an acceptable range of accuracy of 5% difference.

SHAPE CHARACTERIZATION OF CONCRETE AGGREGATE

As a composite material, the performance of concrete materials can be expected to depend on the properties of the interfaces between its two major components, aggregate and cement paste. The microstructure at the interfacial transition zone (ITZ) is assumed to be different from the bulk material. In general, properties of conventional concrete have been found favoured by optimum packing density of the aggregate. Particle size is a common denominator in such studies. Size segregation in the ITZ among the binder particles in the fresh state, observed in simulation studies by concurrent algorithm-based SPACE system, additionally governs density as well as physical bonding capacity inside these shell-like zones around aggregate particles. These characteristics have been demonstrated qualitatively pertaining also after maturation of the concrete. Such properties of the ITZs have direct impact on composite properties. Despite experimental approaches revealed effects of aggregate grain shape on different features of material structure (among which density), and as a consequence on mechanical properties, it is still an underrated factor in laboratory studies, probably due to the general feeling that a suitable methodology for shape characterization is not available. A scientific argument hindering progress is the interconnected nature of size and shape. Presently, a practical problem preventing shape effects to be emphasized is the limitation of most computer simulation systems in concrete technology to spherical particles. New developments at Delft University of Technology will make it possible in the near future to generate jammed states, or other high-density fresh particle mixtures of non-spherical particles, which thereupon can be subjected to hydration algorithms. This paper will sketch the outlines of a methodological approach for shape assessment of loose (non-embedded) aggregate grains, and demonstrate its use for two types of aggregate, allowing evaluation of usefulness of the various methods.

Experimental Study of Stress-Strain Curves of Lightweight Aggregate Concrete

According to the contrast test of LC30, LC40 lightweight aggregate concrete and C30, C40 common concrete , the text researched the mechanical property of lightweight aggregate concrete and ordinary concrete in the same strength grade and obtained the regularity of stress-strain curve of lightweight aggregate concrete in different strength grade. Then we contrasted the experimental results and planning model, analysed the difference, and suggested that the standards should improve the descent stage of the stress-strain curve of lightweight aggregate concrete combined with correlative experiments data, and give the equation of the descent stage of stress-strain curves. Concrete material in axial compression is the basic physical mechanical performance of concrete material, and is the main basis for researching bearing capacity and deformation of concrete construction. The stress-strain relationship is all-around macroscopic reaction of basal compressive property . There have been many experiments work about the stress-strain relationship of lightweight aggregate concrete at home and abroad , and found the peak strain of lightweight aggregate concrete is higher than that of ordinary concrete in the context of same peak stress .In this paper, on the basis of experimental investigations of lightweight aggregate concrete , aim at the stress-strain relationship ,we have take comparison experiment about LC30,LC40 lightweight aggregate concrete and C30,C40 ordinary concrete , and sort out stress-strain curve under the condition of the shaft center being compressed, so get the average tress-strain curve of LC30,LC40 lightweight aggregate concrete , and analyse the curve.

Bayesian 통계법을 활용한 성능기반형 콘크리트 배합설계방법 개발

최근 내구수명기간 동안 요구되는 성능을 만족시키는 차세대 구조설계 연구의 일환으로 PBD 방법에 대한 관심이 증가하고 있다. 성능의 유효여부를 결정하는 방법 중의 하나인 Bayesian 방법은 일반적으로 내진해석 및 설계에서 많이 사용되어왔다. 이 방법은 어느 지진가속도로 인해 발생할 수 있는 구조물의 한계상태(i.e. 붕괴)의 초과확률을 체계적으로 계산할 수 있는 통계방법이다. 이 연구에서는 Bayesian 방법을 활용하여 콘크리트 배합에 대한 강도, 워커빌리티, 탄산화 등과 같은 재료성능의 만족도를 만족 비율로 계산할 수 있는 PBD 개념을 개발하고자 한다. 설계 또는 분석에 사용될 수 있는 Bayesian 방법은 다양한 재료의 특성을 고려하여 만족도 곡선 작성 과정을 설명하고 작성된 만족도 곡선을 사용하는 방법을 제시하고자 한다.

A fully generalised, coupled, multi-phase, hygro-thermo-mechanical model for concrete

A detailed and fully generalised (3D) hygro-thermo-mechanical model for concrete is presented. The model captures the complex behaviour of this composite material through the adoption of a multi-phase material description which captures the strong coupling between the separately considered solid, liquid and gas fields. Heat and mass transport of the fluid phases are modelled in a coupled manner such that an accurate description of the fluid transport processes in concrete is possible, illustrating in particular the redistribution of liquid and the increases in vapour content and pore pressure associated with the application of elevated temperatures. The mechanical behaviour of the solid skeleton is modelled by way of an isotropic thermo-mechanical damage model in which the degradation of the material due to both mechanical and thermal loading is taken into account. Coupling with the hygro-thermal components of the model allows for the effects of material degradation on mass transport to be captured. The model is validated over a wide range of capability through the reproduction of two sets of separate and differing experimental results concerning isothermal drying and high temperature problems. For these two problems, the model is shown to reproduce accurately values for total moisture mass losses, moisture distributions, temperatures and pore pressures developed in both time and space in various types of both ordinary and high performance concrete materials. A further parametric study is then presented where the model is used to investigate the roles of various mechanical behaviours in the overall hygro-thermo-mechanical response of the concrete under high temperature conditions. The implications of the results are discussed in detail.