Evaluation Of Concrete Strength Research Articles

Self-compacting concrete strength evaluation using fire hawk optimization-based simulations

Self-compacting concrete strength evaluation using fire hawk optimization-based simulations

Ternary blended concrete strength evaluation: experimental and artificial intelligence techniques

Purpose The purpose of this study is to forecast the mechanical properties of ternary blended concrete (TBC) modified with oyster shell powder (OSP) and shea nutshell ash (SNA) using deep neural network (DNN) models. Design/methodology/approach DNN models with three hidden layers, each layer containing 5–30 nodes, were used to predict the target variables (compressive strength [CS], flexural strength [FS] and split tensile strength [STS]) for the eight input variables of concrete classes 25 and 30 MPa. The concrete samples were cured for 3–120 days. Levenberg−Marquardt's backpropagation learning technique trained the networks, and the model's precision was confirmed using the experimental data set. Findings The DNN model with a 25-node structure yielded a strong relation for training, validating and testing the input and output variables with the lowest mean squared error (MSE) and the highest correlation coefficient (R) values of 0.0099 and 99.91% for CS and 0.010 and 98.42% for FS compared to other architectures. However, the DNN model with a 20-node architecture yielded a strong correlation for STS, with the lowest MSE and the highest R values of 0.013 and 97.26%. Strong relationships were found between the developed models and raw experimental data sets, with R2 values of 99.58%, 97.85% and 97.58% for CS, FS and STS, respectively. Originality/value To the best of the authors’ knowledge, this novel research establishes the prospects of replacing SNA and OSP with Portland limestone cement (PLC) to produce TBC. In addition, predicting the CS, FS and STS of TBC modified with OSP and SNA using DNN models is original, optimizing the time, cost and quality of concrete.

Strength Evaluation of Concrete using Over burnt Brick Stone as Replacement of Coarse Aggregate

Abstract: This research highlights on the behavior of concrete, prepared by the partial replacement of regular aggregate with over-burnt brick aggregate (jhama brick) with a replacing percentages of 0% , 35, 50% & 60% over M20 Grade of concrete which reduces the cost of aggregate (upto 30%) with higher strength, which also results in overall cost in building too .The effect of compressive strength, split tensile strength and flexural strength were reported . The received compaction factor is 0.92, 0.89, 0.88, and 0.87 with varying percentage of (0%, 35%, 50%, 60%) Jhama class brick respectively. This research was conducted to study the suitability crushed over burnt bricks as alternative course aggregates for concrete production. The compressive strength of this concrete is found to be 27.12 , 30.41, 26.02, 23.31 for 0%, 35%, 50%, 60% respectively. The concrete cube, beams and cylinders of M-20 grade were thrown in this trail, explore work and try to analyze different properties of concrete with crushed over burnt bricks as an alternative material. The result shows that the aggregate in concrete derived from Over Burnt bricks aggregate attained relatively higher strength upto the certain percentage and decreases after that, than the regular concrete. More detailed and elaborated work is recommended with different mix ratio and a different proportion of Over Burnt aggregates for a better conclusion.

A Study to Improve the Reliability of High-Strength Concrete Strength Evaluation Using an Ultrasonic Velocity Method.

The ultrasonic pulse velocity (UPV) technique, which is an efficient technique for concrete quality evaluation, can be affected by several factors. Many studies have proposed compressive-strength prediction models based on UPV in concrete; however, few studies have investigated the factors resulting in statistically different UPV results for different models. This study examined the difference between compressive strengths of various concrete specimens calculated by age-dependent and temperature-dependent UPV-based prediction models. Furthermore, a statistical analysis was conducted to evaluate the influence of aggregates and water/cement ratio (design compressive strength), which are said to affect UPV, on the compressive-strength prediction models. The experimental results revealed that the residual compressive strength of concrete after high-temperature exposure was about 9.5 to 24.8% higher than the age-dependent compressive strength. By contrast, after high-temperature exposure, UPV tended to be about 34.5% lower. The compressive strengths and UPVs were significantly different with respect to high temperature, aggregate density, and design compressive strength. The compressive-strength prediction model derived from the regression analysis showed a high R2 (average 0.91) and mean error converged to zero compared to the compressive-strength prediction model without considering these factors. Finally, the differences between the age- and temperature-based compressive-strength prediction models were analyzed according to the corresponding microstructures.

Machine learning based evaluation of concrete strength from saturated to dry by non-destructive methods

Machine learning (ML) techniques have been increasingly applied in various scientific fields, including non-destructive testing (NDT), to enhance efficiency and speed up data analysis. In this study, an approach that aims to predict the compressive strength and quality of concrete with NDT and ML algorithms is presented to provide a great advantage in terms of both time and cost and to shorten the long laboratory periods. In the study, we aimed to set up a laboratory environment for determining the strengths of concrete samples by using Schmidt hardness values from NDT, curing times, water contents, and ultrasonic velocities. The data obtained in the laboratory environment was subjected to machine learning algorithms in the next process. In the laboratory environment, which is the first stage of the study, because concrete can be found at a variety of humidity levels depending on where it is used, 63 concrete samples were exposed to curing for 7, 28, and 90 days. Then these samples were put through a pressure test and subsequently exposed to various moisture conditions, from saturated to dry. Thus, the moisture state of concrete samples was evaluated based on their dryness or saturation in tests conducted on concrete samples. Afterwards, the ultrasonic velocities and Schmidt hardness values of these samples were measured. In the second stage, the strengths of concrete samples were classified with LR, MLP, SVM, and k-NN algorithms, and high R values were achieved. As a result of the studies carried out, the best R value (0.89) was achieved in the k-NN algorithm. This study has demonstrated that concrete strength values may be approximated with the k-NN method at high levels using sparse data collected in a laboratory setting.

FFRC and SASW nondestructive evaluation of concrete strength from early ages

Free-Free Resonant Column and Spectral Analysis of Surface Waves are two nondestructive testing techniques which are becoming increasingly relevant in construction engineering, as they offer the possibility of assessing the mechanical properties of the building materials without damaging the sample. In the present study, these two testing methods are applied on concrete samples with increasing curing times, from 9 h to 60 days, estimating the dynamic elastic modulus and proposing relationships to obtain the compressive strength from these values. The nondestructive results are compared with the actual strength of the material obtained via uniaxial compression tests, proving the accuracy of the proposed nondestructive testing methodologies, even for early ages. SASW tests are also carried out on a reinforced concrete sample, concluding that the presence of the reinforcement does not alter the results of the test.

Quality control and safety assessment of prestressed concrete bridge decks through combined field tests and numerical simulation

This paper presents a systematic approach for the quality control and safety assessment of existing bridge decks through combined field tests and numerical simulation. The methodology is described in the context of a case study represented by the Zappulla multi-span viaduct (southern Italy), whose deck is realized with simply supported prestressed concrete girders and overlying reinforced concrete slab. Quality control is carried out through an extensive in-situ testing campaign comprising concrete coring, carbonation tests, sclerometric tests combined with ultrasonic pulse velocity for concrete strength evaluation, as well as pachometer and georadar tests for identification of steel reinforcement and prestressing tendons, respectively. Additionally, field tests including static and dynamic loading tests are performed to investigate the bridge response under serviceability conditions. Field-test results along with experimental findings on the material characterization are used to calibrate a finite element (FE) model of the bridge deck, which is subsequently adopted for structural safety assessment of the bridge deck at ultimate limit state (ULS). Two methods for evaluating the safety conditions at ULS are comparatively investigated, namely the Eurocode-compliant semi-probabilistic partial factor method and a deterministic method that computes the global safety factor of the bridge deck in its actual working conditions based on nominal values of loads and resistances. In addition to linear analysis, incremental non-linear static analysis is performed to determine the push-down response of the bridge deck via a concentrated plasticity approach. The proposed procedure, inherently encompassing both serviceability and ultimate loading conditions and synergistically combining material characterization and field-test results with a critical statistical interpretation, accompanied by numerical FE simulation with an eye to design code requirements, provides a reliable tool for the quality control and safety assessment of other similar existing bridges.

Compressive Strength Evaluation of Concrete with Palm Tree Ash

Concrete industry produces high carbon dioxide emissions that are harmful to the environment. As cement is the primary artificial component of concrete, most of the past studies focused on reducing the cement content in concrete manufacturing. To enhance the sustainability of concrete production, generally, cement is partially replaced with waste materials with similar characteristics such as silica fume and fly ash. One of the sources of such waste materials in date-producing countries is palm trees since each palm tree produces approximately 23 kg of waste annually. Currently, very limited use of palm tree waste exists in the concrete industry; specifically, palm tree leaves ash (PTA). This study is intending to evaluate the potential of adding PTA to concrete as a cement replacement by evaluating the compressive strength of PTA concrete. Several concrete cylindrical specimens were cast with variable percentages of added PTA. Three dosages of PTA (5%, 10%, and 15%) were added to the concrete as a substitute for cement by weight. The palm tree ash added to concrete was collected from burned palm tree branches and filtered based on its fineness. Assessment of the compressive strength of PTA-based concrete was performed at ages of 7, 28, and 56 days. The results of evaluating the compressive strength of the specimens showed that the concrete mixed with only 5% PTA possesses around 12% higher compressive strength than that without PTA. Further, increasing the dosage of added PTA to concrete yielded unfavorable results in terms of increasing the compressive strength. The addition of more than 10% of PTA to concrete as a replacement for cement triggered a significant reduction in compressive strength of the concrete. The findings of this study encourage partial replacement of cement with PTA in concrete up to 5% to reduce concrete carbon footprint and enhance sustainability of concrete manufacturing process with maintaining desired mechanical properties.

An alternative numerical model for fiber reinforced concrete strength evaluation

An alternative numerical model for fiber reinforced concrete (FRC) compressive and bending tensile strength determination is presented in this paper. Fibers are modeled explicitly by using the Extended Finite Element Method (XFEM). An alternative method for modeling the fiber-matrix interaction, without the need for additional subroutine definition, is proposed. The presented numerical model was evaluated by experimental tests and results are in good agreement. The model was developed for Simulia ABAQUS software, but the proposed modeling procedure is generally applicable. In the end, some possible model improvements and suggested applications are included.

Fuzzy Logic-Based and Nondestructive Concrete Strength Evaluation Using Modified Carbon Nanotubes as a Hybrid PZT–CNT Sensor

Concrete strength and factors affecting its development during early concrete curing are important research topics. Avoiding uncertain incidents during construction and in service life of structures requires an appropriate monitoring system. Therefore, numerous techniques are used to monitor the health of a structure. This paper presents a nondestructive testing technique for monitoring the strength development of concrete at early curing ages. Dispersed carbon nanotubes (CNTs) were used with cementitious materials and piezoelectric (PZT) material, a PZT ceramic, owing to their properties of intra electromechanical effects and sensitivity to measure the electromechanical impedance (EMI) signatures and relevant properties related to concrete strength, such as the elastic modulus, displacement, acceleration, strength, and loading effects. Concrete compressive strength, hydration temperature, mixture ratio, and variation in data obtained from the impedance signatures using fuzzy logic were utilized in the comparative result prediction method for concrete strength. These results were calculated using a fuzzy logic-based model considering the maturity method, universal testing machine (UTM) data, and analyzed EMI data. In the study, for data acquisition, a hybrid PZT–CNT sensor and a temperature sensor (Smart Rock) were embedded in the concrete to obtain the hydration temperature history to utilize the concrete maturity method and provide data on the EMI signatures. The dynamic changes in the medium caused during the phase in the concrete strengthening process were analyzed to predict the strength development process of concrete at early curing ages. Because different parameters are considered while calculating the concrete strength, which is related to its mechanical properties, the proposed novel method considers that changes in the boundary condition occurring in the concrete paste modify the resonant frequency response of the structure. Thus, relating and analyzing this feature can help predict the concrete strength. A comprehensive comparison of the results calculated using the proposed module, maturity method, and cylindrical specimens tested using the UTM proved that it is a cost-effective and fast technique to estimate concrete strength to ensure a safe construction of reinforced cement concrete infrastructures.

Assessment of Concrete Curing Duration using Bulk Electrical Conductivity and Porosity

Controlling permeability of concrete is essential for enhancing durability and, thus, the service life. Concrete permeability is affected by the total volume of permeable voids and the continuity of the capillary pore structure. Even though concrete strength is the typical performance parameter used to define a wet curing duration, it is important to maintain wet curing until concrete develops a discontinuous capillary pore structure with a minimum volume of total permeable voids to assure durability. Therefore, the required wet curing period can be defined as the longest duration out from the (i) time to achieve the specified strength, (ii) time to develop a discontinuous capillary pore structure, and (iii) time to develop a minimum volume of total permeable voids. Since concrete strength evaluation methods are well developed, there is a need for developing procedures to evaluate concrete pore structure characteristics to decide on the wet curing duration. This study investigated the use of bulk electrical conductivity and porosity test methods described in ASTM C1760 and C642 to evaluate the (i) time to develop a discontinuous capillary pore structure and (ii) time to develop a minimum volume of total permeable voids, respectively. The suggested procedure of wet curing duration assessment is demonstrated for two concrete mixes: one with only Type I cement and the other with Type I cement and slag.

Influential Factors and Determination of strength of in-situ concrete, using twist-off method.

Concrete strength represents by far the most critical property of concrete. It represents the mechanical properties of concrete. On-site evaluation of concrete strength remains the fundamental challenge in the condition assessment of existing infrastructure. Although standard laboratory methods can be typically used but most of these testing methods are costly and time-consuming. Among the in-situ methods, the “twist-off ” method with very slight damage is genuinely a convenient, fast and also low-cost technique that provides accurate results for engineers. In this study, the twist-offmethod has been used for the assessment of in-situ strength of the 30 concrete structures in Qazvin in Iran. The results showed structures studied had a strength of 45 to 600 kg/cm2 and the average is about 200 kg/cm2. The observed variation is very high, as well as a significant difference between the compressive strength of the columns, and the floors of the buildings that all indicate non-standard concrete mixing and inadequate control over construction. However, according to the past experience and results of the samples, some recommendations in this regard have been suggested.

SonReb concrete assessment for spatially correlated NDT data

In this paper the existence of a spatial correlation on the readings of the rebound hammer tests and ultrasonic pulse velocity tests is firstly investigated by means of experimental evaluations on two RC walls. The effect of this correlation is then transferred in the concrete strength evaluation by means of the well known SonReb method. Monte Carlo simulations, carried out to check the goodness of the evaluation with the SonReb standard procedure, highlighted a relevant probability of under- or over-estimation as well as the possibility of not negligible absolute errors of the expected mean compression strengths for the investigated structural elements. A simple modification to the standard procedure is, finally, proposed in order to take into account the concrete spatial correlation and improve the goodness of the SonReb evaluation. This modification, that basically consists in increasing the relative distance between the location of the individual test readings, allows the reduction of the unconservative maximum percentage overestimation error from roughly 15% to 5%.

Laser-induced breakdown spectroscopy for rapid detection of corrosiveness in concrete

Identification of corrosiveness in concrete is necessary for evaluation of building strength. In this study, identification of reinforced concrete corrosion has been successfully conducted using laser-induced breakdown spectroscopy (LIBS) method by identification of sodium element as a fingerprint in the sample. Low-power neodymium yttrium aluminum garnet (Nd:YAG) laser was used (1064 nm, 34mJ, 7ns) as an energy source. The laser beam was focused on concrete sample surface which contains different concentration of sodium-chloride (0.1 % - 1%). The experiment was carried out under atmospheric pressure. The sodium emission line at Na I 589.59 nm was successfully detected. Nice linear calibration curve of sodium line in concrete containing different concentration of sodium chloride (NaCl) was made. The linear curve certified that sodium line can be used as a fingerprint for evaluation of concrete strength.

Evaluation of Concrete Strength for Structures of the Volga Cascade

Calibration curves are plotted to determine the strength of concrete for preliminary evaluation of the concrete structures of the Volga cascade.

Quality control of high-performance concrete in high-rise construction during operation

With onset of the XXI century, the demand for construction of high-rise buildings with the load-bearing framework made of high-performance cast-in-situ concrete has increased many-fold in the construction sector. Specific features of the high-performance concrete of bearing structures in the situation of real operation of high-rise buildings are continuously studied by scientists and specialists all over the world, and regulatory and methodological documents are being complemented and adjusted. High-performance concretes and structures made of them possess some specific features that should be taken into account in quality control. The methods of concrete inspection and concrete strength evaluation described in GOST 18105 “Concretes. Guidelines on Testing and Evaluation of Strength” and GOST 22690 “Concretes. Evaluation of Strength by Mechanic Non-Destructive Test Methods” were written when precast reinforced concrete was predominantly used in the construction sector and were limited to the functions of intra-factory quality control of reinforced concrete products. At present, instruments for non-destructive testing using indirect methods are usually calibrated with the help of local destructions, as a rule, a pull out or rib shear test. The said methods are in fact indirect since they indicate the force of destruction of the surface layer of a structure.

Evaluation of Concrete Strength By Partially Replacing Cement by Red Mud Fly Ash

Evaluation of Concrete Strength By Partially Replacing Cement by Red Mud Fly Ash

Destructive and Non Destructive Strength Evaluation of Concrete Exposed to Fire

In this investigation concrete of different compressive strength is exposed to fire for various duration similar to natural fire occurring in buildings. A total of 72 Concrete cubes have been cast from three different concrete mixes then exposed to fire up to 10000C for three different durations (15,30 and 60 minutes) then tested using non- destructive methods like hammer rebound test and Ultra-Sonic Pulse velocity test. Then the cubes were tested to destruction to measure their compressive strength. The results have shown that the unit weight, compressive strength and actual residual strength decreases with the increase of firing exposure duration similar to concrete exposed to steadily rising temperature. The correlation between the cube compressive strength and RN of the hammer test is very close, however the correlation coefficient of the cube strength with the UPV results is less. Using the combined method of the NDT, the relation between the cube strength and the NDT improves. Equations of relation betweencompressive strength and NDT tests are proposed for use in practice.

RESEARCH OF THE STRESS STATE OF A MODIFIED IN-SITU CONCRETE

Purpose. The article focuses on investigation of the stress state of a modified in-situ concrete of natural hardening. Methodology. To achieve the aim, the research of the microstructure of the modified cement matrix of concrete, as well as the mechanism of structure formation of modified concrete with natural hardening was conducted; the methods for reliable evaluation of concrete strength were defined. Findings. The development of internal stresses affects the properties of concretedifferently. With an increase in temperature-shrinkage deformations in time and, thus, with increasing structural stresses in the cement sheath around the grains of the filler two opposite processes may develop: zone of plastic flow or cracking. Originality. It was established that the structural features complex of the modified concrete when the load transfer leads to the formation of extensive zones of prefracture which is able to absorb a significant amount of elastic strain energy that provides the design deformation properties of the concrete for special purposes. Ideas about the definition of the criteria of cracking modified concrete, hardening under natural conditions had further development. Practical value. The resulting equations allow to solve the problem about the minimum level of structural stress in monolithic concrete in a saturated large placeholder, as well as to assess the influence of structural stresses on the properties of concrete. In normal concrete with a relatively thin cement sheath at temperature-shrinkage deformations, high tangential and low radial tension occur. In vivo, this stress is higher as a result of higher values of Δε(τ), which is not observed in the modified concrete. In the modified concretes only tangential stresses are the greatest danger to structures. The change of shrinkage stress with time is straightforward. The total temperature-shrinkage deformations have a sawtooth graph. For modified concrete the amplitude is 48…53% less. This will allow solving a number of technological challenges in the construction of monolithic buildings.

Concrete strength evaluation in an early-age curing process using SVM with ultrasonic harmonic waves

Concrete strength evaluation in an early-age curing process using SVM with ultrasonic harmonic waves