Concrete Age Research Articles

Expansion prediction of alkali aggregate reactivity-affected concrete structures using a hybrid soft computing method

The phenomenon of alkali aggregate reactivity (AAR) in concrete structures corresponds to the reaction between aggregates with some ingredients and alkali hydroxide in concretes. This AAR could potentially lead to concrete deformation, micro-cracks and eventually wide visible cracks. In this study, to predict the expansion of the concrete caused by AAR, a novel hybrid model is proposed based on support vector machine (SVM). In the proposed model, the inputs are the aggregate components and concrete age, while the output is the induced expansion in the concrete. To improve the generalisation capacity of the proposed model, the enhanced particle swarm optimisation algorithm is employed to select optimal SVM parameters. The proposed method is evaluated and compared with other conventional soft computing methods based on the experimental data. Finally, the evaluated results endorse the effectiveness of the proposed hybrid model.

Comparison of Compressive, Tensile, and Flexural Creep of Early-Age Concretes under Sealed and Drying Conditions

The compressive creep of concrete is normally adopted to predict the stress or the time-dependent deformation of concrete members, without considering the difference of creep under different loading types, i.e., compressive, tensile, and flexural loads. This will inevitably lead to inaccurate prediction of stress and deformation, particularly at early ages when creep effect is pronounced. This study conducts a systematic creep comparison for early age concrete under different loading types and curing conditions. Three types of creep devices are developed for compressive, tensile, and flexural creep measurements of concrete under both sealed and drying conditions. Low-strength and high-strength concretes with water:cement (w/c) ratios of 0.3, 0.4, and 0.5 are tested at the age of 7 days. The measured creep is compared in terms of loading types and curing conditions (sealed versus drying). The ratios of different types of creep are quantified and compared with the literature. The rationality of using compressive creep to substitute tensile or flexural creep is justified. The results of this study provide quantitatively the creep difference under different conditions, which helps to gain confidence about the predicted stress and the strain when different creep models are used.

AGE AND COMPRESSIVE STRENGTH OF CONCRETE FROM VARIOUS BRANDS OF PORTLAND COMPOSITE CEMENT (PCC)

. Recently it is provided in the construction market several types of cement such as OPC (Ordinary Portland Cement), White Cement and most recently is PCC (Portland Composite Cement). The composition of PCC cement’s raw materials is Clinker, gypsum and additive materials. Additive materials used are limestone, fly ash and Trass. Unlike OPC type which does not use Fly Ash and Trass additives, in PCC it is used additives like Fly Ash and Trass where there is SiO2 compound that can increase the compressive strength. The research was carried out at the Laboratory of Civil Engineering Department of the Bali State Polytechnic using a cylindrical test object with size 15x30 cm of 20 pieces for each concrete age with a compressive strength of 25 MPa plan, tested at the age of  3, 7, 14, 21, 28, 56, and 90 days following PBI'71. The concrete strength of the concrete characteristics of the plan was achieved at the age of 56 days, with the value of the compressive characteristic of the plan reached at age 56 days with consecutive values ​​of 25.82, 27.67, 26.80, 31.20 MPa and 28.81 MPa for Tonasa, Holcim, Bosowa, Merah Putih, and Tiga Roda cements. This value is greater than the value of compressive strength targeted based on the calculation of job mix design, in which it is 25 MPa. Conversion of Age and Compressive Strength Characteristics for the 5 (five) brands of PCC cement.

Ekosemen Sebagai Media Perekat Pengganti Semen Untuk Beton

Waste is a serious problem faced at this time. A lot of pollution and diseases caused by waste, therefore many efforts are made so that waste can be utilized even contain economic value. One of the utilization of waste is as an eco-cement used as a substitute for cement.
 This study used the concrete quality of the plan fc '= 10 MPa and fc' = 20 MPa, the making of concrete utilized waste ash in lieu of cement in predetermined quantities, waste ash obtained from organic waste and inorganic waste that was burned to ash and then filtered using 100 and 200 sieves. Variations of ash addition of 0%, 10%, 20%, 30%, 40% and 50% of the volume ratio. Age of concrete testing was 7, 14 and 28 days. The results obtained from the test indicate that the material used met a predetermined standard, with the variation of the concrete weight mixture of concrete unchanged. From the concrete strength test result for fc '= 10 MPa, the best concrete mixed variation is 20% with compressive strength equal to 12,76 MPa at 28 day age, fc = 20 MPa concrete quality with best mix variation 20% has compressive strength of 17.29 MPa, the largest compressive strength value compared with the compressive strength of concrete containing ash, the compressive strength difference of 13.8% lower than the normal compressive strength of the concrete, while the effect of each mixture variation on the age of concrete is linear; with the increase of the age, the compressive strength tends to increase.

Experimental determination of the initial compressive strength of concrete using a rebound test hammer

This paper deals with rebound hammer testing of concrete in the early stage of ageing. Six types of concrete were produced for the purpose of the presented experiment and differed in the water/cement ratio and were otherwise identical as to the input components. SilverSchmidt PC L test hammer was used to determine the rebound coefficient Q and compressive strength of cube test specimens. The aim of the experiment was to verify the possibility of creating a conversion relationship between the determined parameter of the used non-destructive method and the real compressive strength of concrete in the first days of ageing of concrete. Based on the conducted experiment, it may be stated that the SilverSchmidt PC L test hammer with a mushroom plunger is a suitable instrument for determining the initial compressive strength of concrete, starting from the value of about 5 N/mm2. An important conclusion is the fact that it is possible to create a regression model with relatively high accuracy, in this case approximately ± 3 N/mm2.

Investigation of Tensile Creep of a Normal Strength Overlay Concrete.

The present contribution deals with the experimental investigation of the time-dependent behavior of a typical overlay concrete subjected to tensile stresses. The latter develop in concrete overlays, which are placed on existing concrete structures as a strengthening measure, due to the shrinkage of the young overlay concrete, which is restrained by the substrate concrete. Since the tensile stresses are reduced by creep, creep in tension is investigated on sealed and unsealed specimens, loaded at different concrete ages. The creep tests as well as the companion shrinkage tests are performed in a climatic chamber at constant temperature and constant relative humidity. Since shrinkage depends on the change of moisture content, the evolution of the mass water content is determined at the center of each specimen by means of an electrolytic resistivity-based system. Together with the experimental results for compressive creep from a previous study, a consistent set of time-dependent material data, determined for the same composition of the concrete mixture and on identical specimens, is now available. It consists of the hygral and mechanical properties, creep and shrinkage strains for both sealed and drying conditions, the respective compliance functions, and the mass water contents in sealed and unsealed, loaded and load-free specimens.

Application of Crack Identification Techniques for an Aging Concrete Bridge Inspection Using an Unmanned Aerial Vehicle.

Bridge inspection using unmanned aerial vehicles (UAV) with high performance vision sensors has received considerable attention due to its safety and reliability. As bridges become obsolete, the number of bridges that need to be inspected increases, and they require much maintenance cost. Therefore, a bridge inspection method based on UAV with vision sensors is proposed as one of the promising strategies to maintain bridges. In this paper, a crack identification method by using a commercial UAV with a high resolution vision sensor is investigated in an aging concrete bridge. First, a point cloud-based background model is generated in the preliminary flight. Then, cracks on the structural surface are detected with the deep learning algorithm, and their thickness and length are calculated. In the deep learning method, region with convolutional neural networks (R-CNN)-based transfer learning is applied. As a result, a new network for the 384 collected crack images of 256 × 256 pixel resolution is generated from the pre-trained network. A field test is conducted to verify the proposed approach, and the experimental results proved that the UAV-based bridge inspection is effective at identifying and quantifying the cracks on the structures.

Dynamic Measurements for Determining Poisson’s Ratio of Young Concrete

Abstract Knowledge of the elastic properties of concrete at early age is often a pre-requisite for numerical calculations. This paper discusses the use of a laboratory technique for determining Poisson’s ratio at early concrete age. A non-destructive test set-up using the impact resonance method has been tested and evaluated. With the method, it has been possible to obtain results already at 7 hours of concrete age. Poisson’s ratio is found to decrease sharply during the first 24 hours to reach a value of 0.08 and then increase to approximately 0.15 after seven days.

Ultimate pressure capacity of nuclear reactor containment buildings under unaged and aged conditions

Using ABAQUS, a non-linear finite element analysis (FEA) was performed to evaluate and compare the effects of degradation mechanisms by aging on the ultimate pressure capacity (UPC) of APR1400 reactor containment building (RCB). As the primary degradation mechanisms, prestress loss, concrete aging, rebar corrosion, and liner corrosion were simulated in the modelling and calculations. The results for unaged reactor containment buildings showed that the failure sequence by the internal pressure build-up consisted of 4 stages and reinforcement yielding strain of reinforced concrete would be the most important factor governing the UPC of RCBs. Among the four degradation mechanisms, corrosion occurring on the outer and inner rebar layers was identified as the main degradation mechanism affecting most significantly the ultimate pressure capacity of the APR1400 reactor containment building.

STRUCTURAL HEALTH MONITORING USING PZT A REVIEW

Due to the involution of damage occurring in the structure it is difficult to monitor structural health. Electromechanical Impedance technique (EMI) is used for the damage detection in the structural member experimental results are obtained by the applying piezoceramic patches surface bonded and embedded PZT (Lead Zirconate Titanate) patchs are used for the detection of structure failure. This papers reviews online strength gain monitoring of early age concrete is detected with the help of EMI sensing technique. By using this methods detection s well as location, severity estimation is also possible. The piezoceramic materials performs the both works sensor as well as actuator. The proposed method of damage detection are quit effective and sensitive to concrete.

Aggregate Effect on the Concrete Cone Capacity of an Undercut Anchor under Quasi-Static Tensile Load.

In the last decades, fastening systems have become an essential part of the construction industry. Post-installed mechanical anchors are frequently used in concrete members to connect them with other load bearing structural members, or to attach appliances. Their performance is limited by the concrete related failure modes which are highly influenced by the concrete mix design. This paper aims at investigating the effect that different aggregates used in the concrete mix have on the capacity of an undercut anchor under tensile quasi-static loading. Three concrete batches were cast utilising three different aggregate types. For two concrete ages (28 and 70 days), anchor tensile capacity and concrete properties were obtained. Concrete compressive strength, fracture energy and elastic modulus are used to normalize and compare the undercut anchor concrete tensile capacity employing some of the most widely used prediction models. For a more insightful comparison, a statistical method that yields also scatter information is introduced. Finally, the height and shape of the concrete cones are compared by highly precise and objective photogrammetric means.

Accounting for realistic Thermo-Hydro-Mechanical boundary conditions whilst modeling the ageing of concrete in nuclear containment buildings: Model validation and sensitivity analysis

The prediction of large concrete structures behavior such as bridges, dams and Nuclear Containment Buildings (NCB) is a key issue with regards to the evaluation of their durability, safety and the safety of their surrounding environment. In this work, a weakly coupled Thermo-Hydro-Mechanical (THM) modeling strategy is presented within the serviceability state of large structures. It aims at (a) defining and predicting the temperature, the relative humidity, the strains and the stresses in ageing concrete structures under variable and realistic THM loads and (b) qualitatively assessing the damage risk using a stress-based criterion. With that aim in view, the effect of concrete drying on its long term behavior is highlighted by using a revisited description of drying creep adapted to variable hydric conditions. The concrete’s response to variable THM boundaries is also compared to the one where mean and constant ones are considered in the case of NCBs. Two concrete types and three scales are considered for the THM study: the specimen scale for concrete properties identification, the 1:3 and 1:1 (full) scales of Representative Structural Volumes (RSV) for predictive and structural analyses. Through the FE sensitivity analysis, it is shown that the spatial variation of the temperature along the NCB’s height has more effect on the concrete’s ageing than its variation in time. Whereas, the temporal variation of hydric boundaries has a negligible effect away from the drying-exposed surfaces. Finally, it is demonstrated that, due to initial prestressing loads, the ageing kinetic within the NCB’s wall is heterogeneous and cannot be described using constant prestressing loads. Therefore, it is recommended to account for the spatial THM boundaries’ variation when predicting the global concrete ageing in large concrete structures.

Durability of Sustainable Self-Consolidating Concrete

Supplementary cementitious materials such as fly ash, silica fume and ground granulated blast furnace slag (GGBS) have been used widely to partially replace cement in producing self-consolidating concrete (SCC). The production of cement is associated with emission of significant amounts of CO2 and increases the human footprint on the environment. Fly ash, silica fume, and GGBS are recycled industrial by-products that also impart favorable fresh and hardened properties on concrete. This study aims to assess the effect of the amounts of fly ash and silica fume on strength and chloride penetration resistance of concrete. Rapid Chloride Penetration Test (RCPT) was used to assess the ability of SCC to resist ingress of chlorides into concrete. SCC mixes with different dosages of fly ash and silica fume were developed and tested at different curing ages. Test results showed that replacing 20% of cement with fly ash produced the highest compressive strength of 67.96 MPa among all fly ash-cement binary mixes. Results also showed that replacing15% of cement with silica fume produced the highest compressive strength of 95.3 MPa among fly ash-cement binary mixes. Using fly ash and silica fume consistently increased the concrete resistance to chloride penetration at the early ages. Silica fume at all dosages results in low or very low levels of chloride penetration at all curing ages of concrete.

A Study on the Influence of Stage Load on Health Monitoring of Axial Concrete Members Using Piezoelectric Based Smart Aggregate

Piezoceramic based smart aggregate (SA) has been employed to monitor the strength development of early age concrete. The validity of SA-based active sensing method was tested and verified with loading and unloading conditions. However, the early age concrete in buildings is subjected to many load increments during the construction process. The influence of incremental load on the properties of the propagating waves is still unclear. This study aims to investigate the effects of axial stage loads on the signal response of the SA. The concrete specimens that are embedded with SA’s were loaded step by step, and the amplitude and wave velocity of the sensing signals were measured at each stress state. The experimental results indicated that the amplitude of the received signal decrease with the increase of the stress level. As for the velocity of the propagated stress wave, however, the velocity shows an increasing trend before a sharp decline at high stress level.

Statistical validation of new maturity functions for high-strength self-consolidating concrete mixes

A research project was performed to characterize both the setting and hardening of three high-strength self-consolidating concrete mixes used in the production of precast combined pile-cap and column elements (column footings) of the Elevated Highways in Mexico City. By monitoring an eighteen-meter-high column footing during its production, the wide range of internal concrete temperatures experienced by this massive structure at an early age was registered, from 5 to 90 °C. Concrete maturity method was applied to the equivalent mortars after ASTM C1074-11. The analysis of the experimental results allowed the statistical validation of new maturity functions for the equivalent mortar mixtures, which provided better predictions for the relative strength than the deterministic procedure of ASTM C1074-11 for the concrete ages and the wide range of curing temperatures tested. The maturity functions make up the cross-over effect, namely the influence of the internal temperature experienced by concrete on its long-term compressive strength.

Pengaruh Substitusi Abu Cangkang Sawit Terhadap Kuat Tekan Beton

This research was conducted to determine the effect of substitution of palm shell ash mixture on concrete compressive strength. In this case the use of the mixture was made with as many as 9 tests and using 2 variations of concrete age 3 days and 28 days with concrete quality planning f'c = 20 mpa. Based on the results of research in the laboratory, the concrete compressive strength using Palm Shell Ash at 28 days is 20.59 mpa. The robustness of a building is greatly influenced by the quality of the concrete quality, in order to know the quality of a concrete first there is a more careful planning and supervision of the materials to be used. So far, no research has been carried out in the Pagar Alam City Area by removing the Palm Shell Ash.

ANALYSIS OF COST CONTROL, TIME, AND QUALITY ON CONSTRUCTION PROJECT

This research aims to analyze the relationship of delay time and costs with estimated that causes increased costs from perspective of management fees project with earned value method and to analyze the influence of the variables associated with the quality control at each stage of the work concreting. Secondary data collection i.e. the draft budget, the curve S, financing and weekly reports the progress of the project. Primary data i.e. questionnaires to 30 respondents. The cost control and time used earned value methods, and quality control with multiple linear regression. The results of the research project performance until the 27th week of aspects of cost and time projects implementation are not experiencing excess costs, but suffered delays. Regression analysis a very influential determinant variables of each job of making concrete to install formwork: concrete level marking and dimensions for formwork, ironing: the connection reinforcement iron and iron a clean free from rust, oil, and dry concrete, for concreting: checking of slump test and the amount of labor, and to uninstall the formwork: concrete age and concrete level according to plan.

Early age mechanical behaviour of 3D printed concrete: Numerical modelling and experimental testing

A numerical model was developed to analyse the mechanical behaviour of fresh, 3D printed concrete, in the range of 0 to 90 min after material deposition. The model was based on a time-dependent Mohr-Coulomb failure criterion and linear stress-strain behaviour up to failure. An experimental program, consisting of unconfined uniaxial compression tests and direct shear tests, was set-up and performed to obtain the required material properties. The material tests showed that the Young's modulus and cohesion linearly increase with fresh concrete age, as do the compressive and shear strength. The Poisson's ratio and angle of internal friction, on the other hand, remain constant. Subsequently, the model was validated by comparison to printing experiments. Modelling of the printed samples reproduced the experimental results qualitatively, but the quantitative agreement with the print experiments could be improved. However, the deviations can well be explained and the type of failure-deformation mode was predicted accurately.

Bond behavior of steel-fiber-reinforced self-stressing and self-compacting concrete-filled steel tube columns for a period of 2.5 years

The aim of this study is to explore the influence of concrete age on the bond behavior of steel-fiber-reinforced self-stressing and self-compacting concrete-filled steel tube (FSSCFST) columns. The push-out tests of 36 FSSCFST columns are conducted at ages corresponding to 28 d or 2.5 y. All specimens with an age of 2.5 y are tested under four cycles of repeated loading. The variables considered in the test are as follows: (a) concrete age (28 d and 2.5 y); (b) thickness of the steel tube (2.5 mm, 3.5 mm, and 4.25 mm); (c) steel-fiber volume percentage (0% and 1.2%). The experimental results indicate that an increase in the concrete age increases the bond strength and corresponding slip (Su) of FSSCFST columns. The addition of steel fibers improves the bond behavior at an early age and it generally loses its effect with increases in the concrete age. With increases in the loading cycle, the bond strength in the same direction exhibits a decreasing trend. However, steel fibers delay the degradation in bond strength.

Effect of coarse aggregate type on chloride ion penetration in concrete

Long-term durability and sustainability of crucial infrastructure systems such as bridges and pavements are of utmost importance for the economic health of any society. Understanding factors that affect long-term deterioration of reinforced concrete structures can help enhance durability and sustainability of these systems. This paper investigates the effect of the type of coarse aggregate used in concrete on chloride ions penetrability. Twelve coarse aggregate types of different geologic formations (sedimentary, igneous, and metamorphic) were used to prepare fresh concrete in which silica fume and class C fly ash were used. All mix parameters including gradation and volumes of different aggregates were held constant in different mixes with the only variable being the aggregate type. The Rapid Chloride Penetration Tests were conducted on concrete specimens made with various aggregate types at ages of 28, 56, 91 and 365 days. Analysis of test results showed that the aggregate type as well as aggregate absorption rates have significant influence on the electrical charges passed through concrete, especially in early ages of concrete containing aggregates with sedimentary rock origin and relatively high absorption. These specimens exhibited the highest RCPT results indicating higher capacity to allow chloride ion penetration when compared to specimens with igneous and metamorphic rock aggregate of lower absorption values. This influence (discrepancy) diminishes with time for both aggregate type and absorption rates in terms of the magnitude of measured total charge passed.