Use Of High Performance Concrete Research Articles

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.

High-Performance Concrete for Thin-Walled Members

The new production method for mixing and placing of high-performance concrete for thin-walled members has been transferred from laboratory to manufacturing plant and applied on real-scale elements. Planar and spatial precast elements were produced. The new technology is applicable in both building and transportation structures (panels for horizontal and vertical load-bearing structures, bridge elements, leave-in-place formwork, foundation slabs, street furniture). The material used enables significant reduction of thickness of the elements. This leads to lower weight, easier transportation and handling on the construction site, which decreases transportation and assembling costs. Further savings are possible thanks to minimized number of reinforcement bars. High durability of structures is guaranteed by the use of high-performance concrete, leading to reduced life cycle costs.

Superplasticizer for High Strength Concrete

ABSTRACTIn the early 1970s, experts predicted that the practical limit of ready-mixed concrete would be unlikely to exceed a compressive strength greater than 90 MPa [1]. Over the past two decades, the development of high-strength concrete has enabled builders to easily meet and surpass this estimate. The primary difference between high-strength concrete and normal-strength concrete relates to the compressive strength that refers to the maximum resistance of a concrete sample to applied pressure. Although there is no precise point of separation between high-strength concrete and normal-strength concrete, the American Concrete Institute defines high-strength concrete as concrete with a compressive strength greater than 45 MPa. Manufacture of high-strength concrete involves making optimal use of the basic ingredients that constitute normal-strength concrete. When selecting aggregates to obtain high-strength concrete, we consider strength, optimum size distribution, surface characteristics and a good bonding with the cement paste that affect compressive strength. Selecting a high-quality Portland cement and optimizing the combination of materials by varying the proportions of cement, water, aggregates, and admixtures is also necessary. Any of these properties could limit the ultimate strength of high-strength concrete. Pozzolans, such as fly ash and silica fume along with silicic acid, are the most commonly used mineral admixtures in high-strength concrete. These materials impart additional strength to the concrete by reacting with Portland cement hydration products to create additional Calcium Silicate Hydrate (CSH) gel, the part of the paste responsible for concrete strength; finally the most important admixture is polycarboxylate ether as super plasticizer. It would be difficult to produce high-strength ready-mixed concrete without using chemical admixtures. In this paper we study the use of high performance concrete (HPC) to obtain very narrow strong pre-fabricated elements for water conducting channels.

The Use of High Performance Cement Composite in Renovation and Restoration of Architectural Elements of Buildings Facades

The problem of restoration of architectural monuments and facade of historical buildings is very timely over the world. Accelerated degradation of facades is caused by climatic factors and environmental pollution. The paper discusses the possibilities for use of high performance concrete for restoration and sculptures creating in historical buildings. Elaborated mix composition provides high workability of the mix, self-compacting effect and ability of perfect reproducing small elements during moulding. Laboratory testing of samples proved high mechanical strength, low water absorption and enhanced frost resistance. Created and installed sculptural elements perform perfect surface and shape and promise to be more durable comparing to production technology using traditional cement and lime mortar.

Optimized Cost of High Performance Concrete in the Build

The objective of this work is an analysis of the use of high performance concrete and it impact on the morphology and structure costs. The use of high performance concrete (HPC) in the construction of buildings and civil engineering works offers advantages in terms of durability, ease of implementation, reduction of deformation and shrinkage, increase the resistance of reinforced concrete structures. The economic benefits of the use of high performance concrete, compared to conventional concrete are illustrated by the reduction of the following costs: the implementation of concrete, the geometric sections of bearing elements of the built space and the maintenance of structures. The cost of high performance concrete, for the resistance inferior to 80 Mpa, gives a significative advantage comparatively to the steel and the ordinary concrete. The generalized use of this type of concrete in many countries has been stimulated by a national plan.

Flexural Members with High-Strength Reinforcement: Behavior and Code Implications

High-strength steel reinforcement provides various benefits to the concrete construction industry, including a more efficient use of high-performance concrete, reduction of reinforcing bar congestion, and materials savings. Prior to the 2013 interim revisions of the AASHTO LRFD Bridge Design Specifications, the value of reinforcing steel yield strength used in design was limited to being no greater than 517 MPa (exceptions were permitted with owner approval for cases with a yield strength of less than 414 MPa). In 2007, National Cooperative Highway Research Program Project 12-77 was initiated to evaluate the AASHTO specifications with respect to the use of high-strength reinforcing steel and other grades of reinforcing steel having no discernible yield plateau. Among the objectives of this project was the investigation of ductility and crack control of flexural members using high-strength reinforcement. This research led to a number of recommendations that were subsequently incorporated into the 2013 interim revisions of the specifications. The flexural behavior and design of members reinforced with high-strength steel are presented. This paper also provides the background information for the AASHTO specification revisions related to strength reduction factors for flexure. The research demonstrates that the strain limits for high-strength reinforcement must be changed to achieve the curvature ductility comparable to that implicit with the current use of Grade 414 reinforcing steel. Moreover, the service load stresses in steel should be limited to 60% of the yield strength.

Investigating the use of high performance concrete in partially prestressed beams and optimization of partially prestressed ratio

The main objective of this study is to investigate the behaviour of partially prestressed concrete (PPC) beams subjected to pure flexure. The test beams were produced using both high performance concrete (HPC) and traditional concrete (TC). Test beams were compared with each other for strength, strain and cracking cases. The comparison was done by theoretical and experimental methods. Test measurements included failure loads, deflections, strains in concrete and steels, failure moments and service moments, experimental safety coefficients, number of cracks, crack widths, curvatures. Thus, optimum partially prestress ratio was determined for HPC and TC. Advantages of using HPC in partially prestressed beams were brought out. According to the results of the study, optimum partially prestress ratio for PPC beams produced using traditional concrete is ~ 60%; while it is ~ 70% when HPC is used. The test results are shown that the usage of HPC in PPC beams is more convenient than the TC under some boundaries and conditions.

Investigating the use of high performance concrete in partially prestressed beams and optimization of partially prestressed ratio

The main objective of this study is to investigate the behaviour of partially prestressed concrete (PPC) beams subjected to pure flexure. The test beams were produced using both high performance concrete (HPC) and traditional concrete (TC). Test beams were compared with each other for strength, strain and cracking cases. The comparison was done by theoretical and experimental methods. Test measurements included failure loads, deflections, strains in concrete and steels, failure moments and service moments, experimental safety coefficients, number of cracks, crack widths, curvatures. Thus, optimum partially prestress ratio was determined for HPC and TC. Advantages of using HPC in partially prestressed beams were brought out. According to the results of the study, optimum partially prestress ratio for PPC beams produced using traditional concrete is ~ 60%; while it is ~ 70% when HPC is used. The test results are shown that the usage of HPC in PPC beams is more convenient than the TC under some boundaries and conditions.

Development of Mix Proportion for High-Performance Concrete Using Locally Available Ingredients Based on Compressive Strength and Durability

Keywords: High Performance Concrete, mix proportions, compressive strength , and durability Abstract. The use of concrete materials to date, remain a key ingredient in such construction work on the construction of building, bridges and infrastructure. One indicator is the increased production of readymix concrete which is nearly 16 billion tons in 2010. But the increased used of concrete, apparently bring the impact of environmental damage. This is due to the fact that production of raw materials contributes greatly to CO2 in the air. One effort to reduce such impact is to use of high performance concretes. Mix proportion of High Performance Concrete are strongly determined by the quality and availablity of local materials. The implications of research result from other countries can‘t be directly used. Therefore is need to the research on development of High Performance Concrete mix using locally available materials. In this research the mix proportions for f’c : 60 and 80 MPa are developed using local materials that are commonly used by readymix producers. The high Performance Concrete is developed based on compressive strength and durability. The result is expected to be applied to readymix industry particularly for construction use in Indonesia.

Shrinkage and cracking studies of high performance concrete for bridge decks

Restrained shrinkage cracking is a critical issue that raises the concern of widespread use of high-performance concrete (HPC) in bridge deck. Present studies were undertaken to compare the different HPC and propose concept to use local field data to define a threshold for cracking potential. We developed 18 HPC mixtures, suitable for bridge decks in shrinkage-prone locations, using supplementary cementitious materials – fly ash, slag, silica fume, and metakaolin; and local aggregates with three different w/cm: 0.40, 0.35, and 0.30. Basic properties as well as shrinkage and cracking properties were evaluated. In addition to comparing among HPC performance, a correlation was made between commonly measured parameters such as strength, shrinkage, and modulus of elasticity with cracking onset obtained from ring tests. Finally, field data from no-crack and well performing bridges were used to define a threshold safe limit. This concept can be used for design of HPC mixtures to reduce cracking potential from materials point of view for any other locations.

Modelling of concrete perforation

The analysis of penetration of warheads in concrete protective structures is an important part of the study of weapon effects on protective structures. This type of analysis requires that the design load in the form of a warhead is determined, and its characteristic and performance within a protective structure is known. Constitutive equations for concrete subjected to weapon effects have been a major area of interest for a long time, and several material models for concrete behaviour are developed. However, it is not until recent years that it has been possible to use finite element (FE) analyses to simulate the behaviour of concrete targets during projectile penetration with acceptable results. The reason for this is a combination of several factors, e.g. development of suitable material models for concrete, enhancement of numerical methodology and affordable high capacity computer systems. Furthermore, warhead penetration has primary been of interest for the armed forces and military industry, with a large part of the conducted research being classified during considerable time. The theoretical bases for concrete material behaviour and modelling with respect to FE analyses of projectile penetration are treated in the thesis. The development of weapons and fortifications are briefly discussed in the thesis. Warheads may be delivered onto a protective structure by several means, e.g. artillery, missiles or aerial bombing, and two typical warhead types were used within the study. These warhead types were artillery shells and unitary penetration bombs for the use against hardened targets, with penetration data for the later warhead type almost non-existing in the literature. The penetration of warheads in concrete protective structures was therefore studied through a combination of experimental work, empirical penetration modelling and FE analyses to enhance the understanding of the penetration phenomenon. The experimental data was used for evaluation of empirical equations for concrete penetration and FE analyses of concrete penetration, and the use of these methods to predict warhead penetration in protective structures are discussed within the thesis. The use of high performance concrete increased the penetration resistance of concrete targets, and the formation of front and back face craters were prevented with the use of heavily reinforced normal strength concrete (NSC) for the targets. In addition, the penetration depths were reduced in the heavily reinforced NSC. The evaluated existing empirical penetration models did not predict the behaviour of the model scaled hardened buried target penetrators in concrete structures with acceptable accuracy. One of the empirical penetration models was modified to better describe the performance of these penetrators in concrete protective structures. The FE analyses of NSC gave reasonable results for all simulation cases, with the best results obtained for normal impact conditions of the penetrators.

Evaluation of Autogenous Deformation of Concrete at Early Ages

Autogenous shrinkage, significant primarily in concretes with a low water-cementitious material ratio (w/cm), has received more attention in recent years due to increasing use of high-performance concretes (HPCs). In this study, autogenous shrinkage was quantified in both unrestrained and restrained concrete. The specimens were sealed and kept at a constant isothermal temperature of 20°C (68°F) to prevent deformation due to temperature change or moisture loss. Various materials were evaluated to compare their effectiveness in reducing autogenous deformation and stress development, including saturated lightweight aggregates, shrinkage-reducing admixtures, and a shrinkage-compensating additive (based on calcium sulfoaluminate). The data obtained also provides insight into mechanisms behind autogenous shrinkage and the resulting stress development in restrained members and quantify effects of methods used to reduce autogenous shrinkage and resultant stresses.

Physical and Chemical Properties of Nano-slag Mixed Mortar

As buildings have become higher and larger, the use of high performance concrete has increased. With this increase, interest in and use of ultra fine powder admixture is also on the rise. The silica fume and BSF are the admixtures currently being used in Korea. However, silica fume is exclusively import dependent because it is not produced in Korea. In the case of BFS, it greatly improves concrete fluidity and long-term strength. But a problem exists in securing early strength. Furthermore, air-cooled slag is being discarded, buried in landfills, or used as road bed materials because of its low activation energy. Therefore, we investigated in this study the usability of nano-slag (both rapidly-chilled and air-cooled) as an alternative material to the silica fume. We conducted a physic-chemical analysis for the nano-slag powder and performed a mortar test to propose quality standards. The analysis and testing were done to find out the industrial usefulness of the BFS that has been grinded to the nano-level.

Strength properties of HPC using binary, ternary and quaternary cementitious blends

Use of high-performance concrete for structural applications has grown substantially in recent years. This paper focuses on studying the effect of different supplementary cementitious materials (silica fume, fly ash, ground granulated blast furnace slag, and their combinations) on strength characteristics of high-performance concrete. An experimental test programme was conducted to study the effect of such admixtures on compressive strength at 7 days and 28 days, splitting tensile and flexural tensile strengths at 28 days for high-performance concrete. A set of 60 different concrete mixtures were cast and tested with different cement replacement levels (0, 10, 20 and 30% by weight of cement) by various combinations of fly ash and ground granulated blast furnace slag with silica fume as addition (0, 2·5, 5, 7·5, 10 and 12·5% by weight of cement) for each combination. Super plasticiser was added at different dosages to achieve a constant range of slump for desired workability with a constant water–binder (w...

Effect of Curing Methods on Autogenous Shrinkage and Self-Induced Stress of High-Performance Concrete

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Modelling of concrete at early ages: Application to an externally restrained slab

In view of the growing use of High Performance Concrete, with large hydration-induced volumetric changes (both thermal and shrinkage related), numerical modelling of concrete at early ages has become an important issue, regarding the possible formation of cracks, with undesirable consequences on aesthetics and structural durability. In this paper a thermo-mechanical model based on the framework of finite element techniques is presented, and involves the consideration of phenomena such as the heat production induced by the cement hydration, the evolving properties of concrete during hydration and early-age creep. A numerical application is presented, focused on the thermo-mechanical behaviour of a slab strongly restrained by the supporting piles, which has been monitored during the construction phase. For this particular problem it is shown that by making a reasonable thermal and mechanical characterization of concrete, the thermo-mechanical model provides results that are well correlated with the observed in situ measurements, namely the temperatures and the strains.

All-Precast Substructure Accelerates Construction of Prestressed Concrete Bridge in New Hampshire

This article describes a bridge project in New Hampshire that replaced two existing spans with a 115 ft (35.1 m) single-span precast, prestressed concrete box beam superstructure and precast concrete substructure. The Mill Street Bridge (Epping, New Hampshire) project integrated the use of high performance concrete (HPC) and precast/prestressed concrete components. The contract required the bridge to be assembled and ready for traffic in two weeks. The contractor accomplished the task in only eight days. This article focuses on the substructure details and how the project schedule, design, specifications, and contractual arrangements for a conventional bridge-replacement project are affected by specifying rapid bridge construction. The authors describe some of the reasons for the New Hampshire Department of Transportation’s (NHDOT) choice of rapid construction of bridges; these include minimizing construction-related traffic delays and improving work zone safety. The authors summarize with a list of seven conclusions: the precast concrete substructure detailed for use has promise; accelerated construction improves work zone safety; precast elements can be used to address labor limitations; accelerated construction minimizes construction related traffic delays on high volume roads; accelerated construction increases initial cost; grouted joints between precast elements should not be a weak link; and the best delivery concept may be to substitute precast substructure components for cast in place (CIP) elements. The article includes full-color photographs of the bridge project from beginning to completion.

Effect of Relative Humidity on Absolute and Differential Shortening of Columns and Walls in Multistory Reinforced Concrete Buildings

In tall, multistory reinforced concrete buildings, absolute and differential shortening between adjacent vertical members has become a significant problem during the recent past due to the use of high performance concrete and more advanced design techniques that resulted in smaller member sizes. The failure of nonstructural elements such as claddings has been observed in several structures constructed in the past few decades. The factors that cause these problems could be identified as time-dependent creep and shrinkage coupled with elastic shortening. Both creep and shrinkage depend on the relative humidity of the surrounding environment. This paper discusses the effect of relative humidity on absolute and differential shortening of vertical elements in reinforced concrete buildings.

Instrumentation and Analysis of High-Performance Concrete Bridge Decks

The use of high-performance concrete (HPC) for transportation structures was the subject of a 3-year study that involved field investigation, laboratory experiments, analysis, and modeling. The field study involved instrumentation and analysis of six HPC bridge decks. The laboratory component characterized early-age thermal, shrinkage, creep, and cracking behaviors. A three-dimensional finite element model was used in conjunction with material models to analyze and predict creep and shrinkage behavior and to investigate structural and material interactions. This paper focuses on the field component of the project and discusses the instrumentation, deformation measurements, and analysis of bridge decks in Illinois. The bridges were instrumented to understand the development of shrinkage and thermal stress in concrete bridge decks with the use of various materials and structural components. The results indicate that the stress development due to daily temperature cycles and long-term temperature changes are relatively small compared with the stress development due to drying shrinkage. According to model simulations, a 15% to 40% reduction in shrinkage would reduce the stress level enough to prevent most cracking. Although drying shrinkage is the major driving force for stress development, the interaction of concrete shrinkage and structural restraint influences the magnitude of the stress and is linked to the propensity for early-age cracking.

Instrumentation and Analysis of High-Performance Concrete Bridge Decks

The use of high-performance concrete (HPC) for transportation structures was the subject of a 3-year study that involved field investigation, laboratory experiments, analysis, and modeling. The field study involved instrumentation and analysis of six HPC bridge decks. The laboratory component characterized early-age thermal, shrinkage, creep, and cracking behaviors. A three-dimensional finite element model was used in conjunction with material models to analyze and predict creep and shrinkage behavior and to investigate structural and material interactions. This paper focuses on the field component of the project and discusses the instrumentation, deformation measurements, and analysis of bridge decks in Illinois. The bridges were instrumented to understand the development of shrinkage and thermal stress in concrete bridge decks with the use of various materials and structural components. The results indicate that the stress development due to daily temperature cycles and long-term temperature changes are relatively small compared with the stress development due to drying shrinkage. According to model simulations, a 15% to 40% reduction in shrinkage would reduce the stress level enough to prevent most cracking. Although drying shrinkage is the major driving force for stress development, the interaction of concrete shrinkage and structural restraint influences the magnitude of the stress and is linked to the propensity for early-age cracking.