Cement Concrete Structures Research Articles

Acid Attack Resistance of Magnesium Phosphate Cement

Magnesium phosphate cements (MPC) had been used as repair materials for deteriorated Portland cement concrete structures. In this paper a new MPC was prepared and the basic properties including workability and compressive strength were tested. The acid attack resistance of MPC was investigated by immersing the MPC mortars in solutions at pH 3, 5, and 7, for 14d, 28d and 60d respectively. The compressive strength of MPC mortars after acid attack was tested and the microstructure of MPC were examined. The results showed that the compressive strength of MPC decreased after immersion in acid solution for 14d and 28d, however the strength of MPC with suitable materials mixture can recovered again after 60d immersion. The results indicated MPC has high acid attack resistance in static acid solution. The behavior of MPC in flowing acid solutions is need to be studied further.

STRENGTHENING OF RCC STRUCTURES USING FRP COMPOSITE TECHNOLOGY

Fiber reinforced polymer (FRP) composites are gaining wide applications in retrofitting of Reinforced Cement Concrete (RCC) structures owing to its inherent advantages over other conventional methods of strengthening. It finds its use in strengthening of structures having deficiencies arising due to usage, design and other loading changes. The use of Fiber reinforced polymer (FRP) composites as externally bonded reinforcement in the strengthening and retrofitting of Reinforced Cement Concrete (RCC) structures has been presented in this paper. An approach on designing of structures based on the American Codal provisions of ACI.440.2R along with on-site applications has been outlined

Extended synthetic aperture focusing technique for ultrasonic imaging of concrete

Quantitative nondestructive characterization of defects and inclusions in portland cement concrete structures are realized in this paper via extended reconstructions for linear array ultrasound systems. This is accomplished through generalization of traditional Kirchhoff-based synthetic aperture focusing technique migration to mitigate the effects of limited aperture and handle multiple scans as a single virtual array with increased effective aperture. Pearson’s correlation is utilized to account for uncertainty in relative position of individual measurement and mitigate the need for robotic precision when placing adjacent scans. The robustness of the method is demonstrated on artificially generated data as well as in-situ measurements for assessment of internal portland cement concrete characteristics such as inclusions and cracks.

Corrosion Behaviours of High Strength TMT Steel Bars for Reinforcing Cement Concrete Structures

Steel has been used for many decades in structural applications because of its good combination of mechanical properties. As per recent concept to reduce steel consumption in reinforced cement concrete (RCC) structures, designers recommend high strength steel bars. There are various routes for their production such as microalloying, thermomechanical treatment, cold working, etc. For steel bars of thermomechanical treatment (TMT) route, some designers believe these steel bars to be more sensitive to corrosive environment. To verify this, corrosion behaviours of high strength steel bars of 500W (weldable steel bar of yield strength 500MPa) grade of two different local industries have been studied in fresh water and sea water, which were compared with weldable low strength (yield strength 300MPa) bars of the same companies. Experimental results revealed that addition of small amount of alloying elements such as Cr, Ni and Cu improves the corrosion resistance of the steel bars in all test mediums; however, strength levels have no influence the corrosion rate. A relation has also been found between the severity of corrosion damage and the degree of tensile property degradation.

Environmental assessment of road construction and maintenance policies using LCA

This paper proposes an evaluation of pavement maintenance policies relative to their initial construction, through a Life Cycle Assessment (LCA) and in accordance with the framework established by the Society of Environmental Toxicology and Chemistry as well as in the ISO 14040 Standard. The respective influence of initial construction and maintenance operations is investigated for both asphalt concrete and cement concrete pavement structures. Several case studies are analysed using a specific method and tool, called ECORCE (French acronym for “ECO-comparator applied to Road Construction and Maintenance”), dedicated to road pavement LCA. ECORCE takes into account the materials production, mixing and laying processes, in addition to their transport between the production site and the jobsite. This environmental assessment is based on the principles underlying the life cycle assessment methodology. The chosen Functional Unit only considers the service to road users; heavily-trafficked French motorway structures are thus described over a 30-year service period. A set of overall indicators, consisting of raw material and energy consumption, global warming potential and eutrophication potential, is then calculated for two case studies. These environmental indicators highlight the ability to assess pavement designs along with two maintenance policies considered for each case studied. Results are thus able to expose the relative influence of maintenance (1/3 of the entire life cycle). In conclusion, environmental design principles to achieve a reduction in environmental loads are discussed in considering the entire road life cycle.

Modeling a Thermo-Stressed State of the Cast-in-Situ Low Carbon Footprint Alkali Activated Slag Cement Concrete Hardened under Hot Environment

Alkali activated slag cement concretes are low carbon footprint building mateirals, which can meet the requirements for sustainable development. The paper covers the results of modeling a thermo-stressed state of the cast-in-situ massive alkali activated slag cement concrete structure hardened under hot environment to meet the requirements for marine engineering application. The results show that alkali activated slag cement concretes have a substantially lower heat release than that of Portland, are suitable for cast-in-situ massive alkali activated slag cement concrete structure even under hot environment.

Investigation of Factors Affecting PCC Surface Resistivity through Ruggedness Testing

Many entities currently use permeability specifications in Portland cement concrete (PCC) pavements and structures. Recent studies have shown surface resistivity testing correlates well with ASTM C1202 [“Standard Test Method for Electrical Indication of Concrete’s Ability to resist Chloride Ion Penetration,” Annual Book of ASTM Standards, ASTM International, West Conshohocken, PA, 2010] rapid chloride penetration (RCP) testing. The success of this research has led to surface resistivity testing on Portland cement concrete cylinders being implemented in Louisiana. However, many of the studies have questioned the impact of various factors on surface resistivity measurements. This project investigates a ruggedness factorial using many of the factors in question to determine the level of impact of each factor. A partial factorial consisting of 35 combinations of factors was developed using 11 factors and 16 mixtures. Some factors were mixture dependent; therefore, RCP testing was also performed on a portion of the factorial to determine if factors influence the surface resistivity meter or permeability in general. The ruggedness study showed age and aggregate type as significant factors for surface resistivity. Additional comparisons against a control suggested age, calcium nitrite, aggregate size, and aggregate type as significant factors for surface resistivity. However, comparative RCP testing on the same sample sets concluded that all significant factors determined either affect the permeability of the sample in general or will influence rapid chloride permeability as well.

Influences on the Axle Load Stress of the Cement-Concrete Pavement Structure Caused by the Crack or Cutting Crack of the Semi-Rigid Base

Some horizontal cracks will appear during the strength formation of the semi-rigid base, for the influences of dry shrinkage and temperature shrinkage exist, so the engineers often adopt the manual method of equidistant cutting crack to avoid the irregular cracks. In order to analyse the influences on the axle load stress of the cement-concrete pavement slab which caused by the width and position of the base cracks or cutting cracks, the 3D FEM was used to study them under the different working conditions considering the crack, width and position. By the above research, the results show the existing cracks affect the integrity and continuity of the pavement structure; The crack width has no large influence on the stress of the pavement slab, while the base stress decreases apparently with the increasing width, and it becomes stable finally; The stress of the pavement slab is maximum when the crack or cutting crack is located in the middle, while it's small when the crack or cutting crack is located in the one fourth of the pavement slab.

Research on Multi-Parameters Estimation Models of Cement Concrete Compressive Strength

When acoustic wave passes through concrete, it can reflect concrete quality information through velocity of sound, amplitude, and frequency. Because single acoustic parameter is incapable of reflect concrete quality information in full, the paper carry out the research of multi-parameter models of strength estimation of cement concrete. The paper founded multi-parameter mathematic models of strength estimation on based of wave equation with ultrasonic method. These models consist of dual-parameter model I between velocities of sound, attenuation coefficient I and compressive strength , dual-parameter model II between velocities of sound, attenuation coefficient II and compressive strength, and tri-parameter between velocities of sound, attenuation coefficient I, and attenuation coefficient II and compressive strength. Correlation coefficient of strength estimation of dual-parameter and tri-parameter models is higher. When testing distance is equivalent standard test block in detecting structure of cement concrete, these models may be adopted strength estimation of dual-parameter and tri-parameter models apply in Penetrating method of ultrasonic directive wave.

The Different Road Surface Structure Combination Stress Contrast Analyse under the Axis Load

Based on the multi-layer elastic system theory , a large general used finite element software is used to analysis in the paper. To the asphaltum concrete surface layer pavement structure, the basic layer shares more load for surface layer along with the basic layer rigidity increasing. To the cement concrete surface layer pavement structure, the basic layer shares less load for surface layer along with the surface layer rigidity increasing. Whichsoever, the soil ground equivalent stress below subgrade 2m deep is almost not affected from the pavement structure layer rigidity change, but it will increase with the load increasing.

Effects of Flexible Functional Layer on the Load Stress of Cement Concrete Pavement Structure

The vehicle load stresses of the cement concrete pavement structure with/without flexible functional layer were contrastively analyzed by numerical simulation with using ANSYS software. The results showed that the load stress of the cement concrete pavement structure with flexible functional layer was much lower than that without flexible functional layer under the vehicle load. Consequently, the force condition of the pavement structure was effectively improved by the flexible functional layer.

Effects of Flexible Functional Layer Incorporated with Rubber Powder on the Vibration Reduction of Cement Concrete Pavement

Small sized specimen of cement concrete pavement structure was prepared indoors. By utilizing the dynamic signal tester and obtaining the vibration frequency domain signals through the falling-ball vibration impact test method, the attenuation rules of the vibration response of the pavement structure were analyzed and the effects of the flexible functional layer on the vibration-reduction and energy-absorption were studied. The results showed that, after compared with the normal flexible functional layer, the flexible functional layer incorporated with rubber powder resulted in the pavement structure having the better capacities of vibration-reduction energy-absorption and impact resistance. Accordingly, the rupture failure of the cement concrete pavement induced by vehicle load can be reduced.

규사코팅 FRP와 콘크리트 부착특성에 동결융해가 미치는 영향

As fiber reinforced polymer (FRP) material is appled for a curved structure such as tunnel, FRP material must has a curved shape. Until now, the curved FRP material has been producted by hand-lay-up or filament winding work. It is impossible for mass production of the curved FRP material by these methods. Also, the quality of product by these methods is lower than that by pultrusion method. New pultrusion method and equipment had been developed for production of FRP material with steady curvature. The objective of this study is to evaluate the effect of freezing and thawing on adhesion of cement concrete with coarse-sand coated FRP in repair and reinforcement of cement-concrete structure using curved FRP material.

Finite Element Modeling of a Multi-Storeyed Retrofitted Reinforced Concrete Frame

In the present study, the non-linear response of RC frame using FE modeling under the incremental loading has been carried out in the first phase of analysis to study the response and load-carrying capacity of a four storeyed RC frame using non-linear finite element analysis. In the second phase of study an analysis model for retrofitted RC frame using finite element method using software ATENA is presented. The results obtained from FE analysis in both cases are compared with the experimental data for four storeyed RC frame tested by BARC at CPRI. The results from finite element analysis were calculated at the same location as used in experimental test. The accuracy of the finite element model is assessed by the comparison with experimental results which are to be in good agreement. The base shear/ displacement curves from finite element analysis agree well with the experimental results in linear range. The maximum difference in base shear is observed to be 7.9%. I. Introduction In order to evaluate the margin of safety of RC structures against failure an accurate estimation of the ultimate load is very important and the project of the load-deformation behavior of the structure throughout the range of elastic and inelastic response is desirable.There are various factors which are accountable for these deteriorations, such as increasing load, corrosion of steel, earthquake, environmental effects and accidental impacts on the structure. The increase in scale of modern structures is closely related to the extent and impact of disaster in terms of human and economical loss in the happening of structural failure (1). As a result, careful and detailed structural safety analysis becomes more and more crucial. The purpose of such an analysis is the investigation of the behavior of the structure under all probable loading conditions, both, monotonic and cyclic The static pushover analysis is becoming a common tool for seismic performance assessment of existing and new structures. The pushover analysis provides adequate information on seismic demands imposed by the design ground motion on the structural system and its components. The purpose of pushover analysis is to evaluate the projected performance of structural systems by estimating performance of a structural system by estimating its strength and deformation demands in design earthquakes by means of static inelastic analysis, and comparing these demands to available capacities at the performance levels of interest. The inelastic static pushover analysis can be viewed as a method for predicting seismic force and deformation demands, which accounts in an approximate manner for the redistribution of internal forces that no longer can be resisted within the elastic range of structural behavior (2). Up-gradation of reinforced concrete structures is required for many different reasons. The concrete may have become structurally inadequate for example, due to deterioration of materials, poor initial design and/or construction, lack of maintenance, upgrading of design loads or accidental events such as earthquakes. That's why repair and rehabilitation has become an increasingly important challenge for the reinforced cement concrete structures in recent years. The major goals of the retrofitting are to strengthening the retrofitted structures for life safety and the protection of the structures. The existing deficient structures are retrofitted to improve their performance in the event of any natural disaster and to avoid large scale damage to life and property. Evaluation of behaviour of structures after retrofitting is more important. 1.1 Importance and Historical Background of Finite Element Modeling The complicated analytical modeling of the complex behaviour of reinforced concrete in its non-linear zone has led engineers in the past to rely heavily on empirical formulas which were derived from numerous experiments for the design of reinforced concrete structures. The finite element method makes it achievable to take into account the non-linear response. Finite element method of analysis has become a powerful computational tool with the introduction of digital computers, which allows complex analyses of the nonlinear response of RC structures to be carried out in a regular mode. Though FEM is useful for obtaining the load

Resilience and Trends of Concrete-Polymer Composites in Japan

On March 11, 2011, a massive earthquake with a magnitude of 9.0 struck Sanriku Coast, Japan. The ensuing tsunami swept across many cities and villages along the Pacific coast of the Tohoku district, causing tremendous human and structural damage. These disasters gave a good chance to review the relationship between infrastructures and sustainability in Japan from the viewpoints of concrete structures and concrete-polymer composites. The article introduces essential defects of cement concrete structures and discusses different state-of-the-art concrete-polymer composites and the properties of ultra high strength fiber reinforced concrete.

Influence of Curing Time on the Pore Structure of the Phosphoaluminate Cement Concrete

Influence of Curing Time on the Pore Structure of the Phosphoaluminate Cement Concrete

Applying Research on Testing Compressive Strength of High Performance Concrete with Rebound Method

In order to grasp timely and accurately quality of high performance concrete, detection of compressive strength of high performance concrete can be non-destructively, rapidly and accurately tested that is very testing index. The paper did some research on compressive strength of high performance concrete applying redound method that it established several estimation models between rebound value and compressive strength. Experiment shows that rebound method can effetely test compressive strength of high performance concrete. Construction quality of Cement concrete structure can timely grasp applying the method.

Applying Research on Testing Technique of High Performance Concrete

In order to master timely and accurately construction quality of high performance concrete, detection of compressive strength of high performance concrete can be tested non-destructively, rapidly and accurately. The paper did preliminary research on high performance concrete with redound method, furthermore, it established estimation model between rebound value and compressive strength. Experiment shows that rebound method can effetely test compressive strength of high performance concrete. Construction quality of Cement concrete structure or component can timely grasped in period of construction with the method.

Numerical Simulation of the Process of Partial Void Formation under Cement Concrete Pavement Slab

The damage of void under cement concrete slab is one of the main diseases in cement concrete pavement. By finite element method, a 3-D model of cement concrete pavement structure was established to simulate the partial void under the cement concrete pavement slab with different loading conditions. The process of the division between the subgrade and the slab with a soft area under the slab are reappeared. The changing rules of the void size with the number of cycle load in case of different tie pressure and loading location (at the center, edge or corner of the slab).

Research on Effects of Inhibitors on Anti-Corrosion Performance of Reinforced Bar in the Concrete

The corrosion behavior of reinforcing bars in concrete was studied by simulating the 4×4 wire-beam electrode array. Different inhibitors were added to reinforced concrete. By measuring the open-circuit potential of an iron wire, the impact of different inhibitors on the corrosion of rebar in the concretes was studied after immersion in NaCl solution. The result showed that best protection was achieved by adding NaNO2 and aniline as inhibitors jointly to the concrete, as this combination maintained the open-circuit potential within the passivation range at all times, so ensuring the integrity of the passive membrane. By addition of this combination of the inhibitors, the compactibility of the cement concrete structure can be increased, thereby protecting the reinforcing bar against the external corrosive media.