Uniaxial Compressive Strength Of Concrete Research Articles

Compressive strength prediction of nano-modified concrete: A comparative study of advanced machine learning techniques

This study aims to develop predictive models for accurately forecasting the uniaxial compressive strength of concrete enhanced with nanomaterials. Various machine learning algorithms were employed, including the backpropagation neural network (BPNN), random forest (RF), extreme gradient boosting (XGB), and a hybrid ensemble stacking method (HEStack). A comprehensive dataset containing 94 data points for nano-modified concrete was collected, with eight input parameters: water-to-cement ratio, carbon nanotubes, nano-silica, nano-clay, nano-aluminum, cement, coarse aggregates, and fine aggregates. To evaluate the performance of these models, tenfold cross-validation and a case study prediction were conducted. It has been shown that the HEStack model is the most effective approach for precisely predicting the properties of nano-modified concrete. During cross-validation, the HEStack method was found to have superior predictive accuracy and resilience against overfitting compared to the stand-alone models. This underscores the potential of the HEStack algorithm in enhancing model performance. In the case study, the predicted results were assessed using metrics such as the coefficient of determination (R2), mean absolute percentage error (MAPE), root mean square error (RMSE), the ratio of RMSE to the standard deviation of observations (RSR), and the normalized mean bias error (NMBE). The HEStack model achieved the lowest MAPE of 2.84%, RMSE of 1.6495, RSR of 0.0874, and absolute NMBE of 0.0064. In addition, it attained a remarkable R2 value of 0.9924, surpassing the R2 scores of 0.9356 (BPNN), 0.9706 (RF), and 0.9884 (XGB), indicating its exceptional generalization capability.

The oedometric EOS of equal strength and different mix compositions concrete specimens

The uniaxial compressive strength of concrete is commonly used to characterize concrete properties. The three-dimensional behavior of concrete structures is modelled by the hydrostatic and deviatoric relationships. These relationships are assigned to a given concrete according to its uniaxial compressive strength. Based on high velocity penetration test results at targets with identical concrete strength, that were prepared from different mix designs, the authors conjectured that the slab behavior is not governed by the uniaxial compressive strength but by the concrete composition.This paper presents an experimental investigation of concrete specimens of equal uniaxial compressive strength, that are made from different mix compositions, aiming at examining the equation of state (EOS) and its relationship to the uniaxial compressive strength and to several mix components, in attempt to validate the above conjecture.A set of specimens was prepared characterized by equal uniaxial compressive strength (fc = 56 MPa) measured on 100 mm sided cubes. Several specimen groups were tested, each of them made from a different composition. The mix variables were the weight of water (and the corresponding weight of cement), the aggregates weight and the maximum aggregate size. The specimens were tested in a special triaxial apparatus, to high load-levels (up to 5000 kN), at a quasi-static rate of ∼ 5 kN/sec. Test results show a wide scatter of the EOS curves, depending on the different mix parameters. These results refute the commonly assumed correlation between the uniaxial compression strength and the EOS and validates the conjecture that the EOS depends on the specific concrete mix composition.

Numerical Test and Strength Prediction of Concrete Failure Process Based on RVM Algorithm

Recycled aggregate concrete (RAC) based on the machine learning (ML) method predicts the nonlinear uncertainty relationship between various mixing ratios and strength. Uniaxial compressive strength is one of the important indices to evaluate its performance. Machine learning is one of the essential methods for solving this nonlinear uncertainty relationship. To realize the selection of concrete raw materials and the learning and application of other influencing factors and provide guidance for engineering construction and application, this paper establishes a database of concrete uniaxial compressive strength based on Abaqus simulation software. The simulation results are highly consistent with the actual values. Based on the simulation database, with different water-cement ratios, different curing days, and recycled aggregate replacement rates as the input data set, the uniaxial compressive strength of concrete is the output data set. The data set is divided into a training set and a test set. A prediction model of the uniaxial compressive strength of concrete based on a relevance vector machine (RVM) algorithm is established. The results show that the maximum error between the simulated and experimental uniaxial compressive strength values is only 0.2 MPa. The correlation coefficient R between the predicted and simulated values of the concrete uniaxial compressive strength prediction model based on the RVM algorithm is 0.975. The model can effectively predict the compressive strength of RAC to meet the engineering requirements.

Intelligent Design of Building Materials: Development of an AI-Based Method for Cement-Slag Concrete Design.

Cement-slag concrete has become one of the most widely used building materials considering its economical advantage and satisfying uniaxial compressive strength (UCS). In this study, an AI-based method for cement-slag concrete design was developed based on the balance of economic and mechanical properties. Firstly, the hyperparameters of random forest (RF), decision tree (DT), and support vector machine (SVM) were tuned by the beetle antennae search algorithm (BAS). The results of the model evaluation showed the RF with the best prediction effect on the UCS of concrete was selected as the objective function of UCS optimization. Afterward, the objective function of concrete cost optimization was established according to the linear relationship between concrete cost and each mixture. The obtained results showed that the weighted method can be used to construct the multi-objective optimization function of UCS and cost for cement-slag concrete, which is solved by the multi-objective beetle antennae search (MOBAS) algorithm. An optimal concrete mixture ratio can be obtained by Technique for Order Preference by Similarity to Ideal Solution. Considering the current global environment trend of “Net Carbon Zero”, the multi-objective optimization design should be proposed based on the objectives of economy-carbon emission-mechanical properties for future studies.

Experimental study on mechanical properties of precast cracked concrete under different cooling methods

In order to investigate the mechanical properties and crack propagation of concrete after high temperature, the concrete specimens with different angles of prefabricated cracks are treated with different high temperatures and different cooling methods and then subjected to uniaxial compression. The T2 spectrum is performed on the concrete that has experienced different high temperatures to detect its pore changes. Acoustic emission is used to monitor the destruction process of the concrete during the test. The composition of the damaged specimen by scanning electron microscope and X-ray diffraction are analyzed, then the relationship between the stress–strain curve, porosity change and macroscopic and microscopic properties of concrete are compared and analyzed. In this study, a certain range of high temperature significantly increased the uniaxial compressive strength of concrete. Then, the uniaxial compressive strength decreased rapidly when the temperature is higher than a certain level. It is observed that the bonding degree of concrete aggregate and cement inside the damaged specimen is different after high temperatures and cooling methods treated by using scanning electron microscope. The damage degree of concrete caused by high temperature and water cooling is far greater than that of air cooling. The acoustic emission signal and energy release between the normal temperature specimen and the specimen after high temperature treatment in the test process are quite different. This paper explains the mechanical phenomena of cracked concrete specimen after being treated with high temperature and different cooling methods from the microscopic and mesoscopic perspectives.

Prediction of concrete strength from rock properties at the preliminary design stage

This study aims to explore practical and useful equations for rapid evaluation of uniaxial compressive strength of concrete (UCS-C) during the preliminary design stage of aggregate selection. For this purpose, aggregates which were produced from eight different intact rocks were used in the production of concretes. Laboratory experiments involved the tests for uniaxial compressive strength (UCS-R), point load index (PLI-R), P wave velocity (UPV-R), apparent porosity (n-R), unit weight (UW-R) and aggregate impact value (AIV-R) of the rock samples. UCS-C, point load index (PLI-C) and P wave velocity (UPV-C) of concrete samples were also determined. Relationships between UCS-R–rock parameters and UCS-C–concrete parameters were developed by regression analyses. In the simple regression analyses, PLI-C, UPV-C, UCS-R, PLI-R, and UPV-R were found to be statistically significant independent variables to estimate the UCS-C. However, higher coefficients of determination (R2=0.97-1.0) were obtained by multiple regression analyses. The results of simple regression analysis were also compared to the limited number of previous studies. The strength conversion factor (k) values were found to be 14.3 and 14.7 for concrete and rock samples, respectively. It is concluded that the UCS-C can roughly be estimated from derived equations only for the specified rock types.

Predicting the compressive strength of concrete from its compositions and age using the extreme gradient boosting method

The uniaxial compressive strength (UCS) is one of the most important mechanical properties of concrete. This paper aims to demonstrate that the UCS of concrete can be accurately predicted from its compositions and age using the extreme gradient boosting regression (XGB) method. The artificial neural networks (ANN) and the support vector machine (SVM) methods are also considered to compare with the XGB method. A relevant laboratory measurement dataset available in literature is considered to train and test the machine learning (ML) methods. We observe that all the three considered ML methods provide accurate results. However, the XGB method is more robust, faster to train and more accurate than the ANN and SVM methods as well as other existent ML methods presented in literature.

Experimental Study on Uniaxial Compressive Strength of Concrete Incorporated with Cigarette Butts

Mixing cigarette butts into concrete to reduce the urban heat island effect caused by concrete while dealing with cigarette butts waste, the possibility of "one stone catches two birds" provides a new idea for urban environmental protection. The influence of cigarette butts content on the mechanical properties of concrete needs to be studied. The cigarette butts are cleaned and dried, then sealed and hardened by paraffin wax. Cigarette butts are mixed into concrete cubic block according to the content of 0kg/m3, 5kg/m3, 7.5kg/m3, 10kg/m3, 12.5kg/m3, 15kg/m3 and 20kg/m3 respectively. The cubic uniaxial compression test is carried out. With the increase of cigarette butts content, the concrete strength decreased continuously, if the cigarette content is not exceed 10kg/m3, the reduction of strength is slow, and the maximum strength loss is 13%. If the cigarette content is larger than 10kg/m3, the strength reduces faster, when the cigarette butt content achieves 20kg/m3, the strength loses 30%. For the concrete with no cigarette, it crushes into many pieces, with the increase of content of cigarette butts, the failure pattern shows better ductility.

08.48: Double‐steel plate composite shear walls: In‐plane seismic behaviour

ABSTRACTDouble‐steel plate concrete (SC) composite shear walls are a structural system intensively used in nuclear facilities due to its exceptional performance. It consists of a concrete core with exterior steel faceplates serving as reinforcement. These steel faceplates are anchored to the concrete infill using headed steel studs which guarantee the composite action between the two different materials. The focus of this research is the investigation of the seismic performance of rectangular SC composite shear walls for application to buildings. A simple and cost‐efficient form of the SC wall is proposed based on the research conducted by Vazouras and Avdelas [1]. Its efficiency has been proved through extensive numerical analysis using a simplified finite element model developed in ANSYS [2] to simulate the nonlinear cyclic response of SC walls. The accuracy of the developed numerical model was validated using experimental data reported in the literature [3, 4]. The numerical predictions included global force‐displacement responses, strain and stress distributions on each material and damage to the steel plates and concrete. A typical damage pattern of the SC walls included yielding, local buckling and tearing of the steel plates in conjunction with cracking and crushing of the infill concrete. The impact of various parameters on the in‐plane response of SC walls has been investigated including wall aspect ratio, reinforcement ratio, slenderness ratio, wall thickness, yield strength of the steel plates and uniaxial compressive strength of concrete.

Seismic analysis and design of steel-plate concrete composite shear wall piers

This paper presents results of numerical studies on the in-plane monotonic response of steel-plate concrete (SC) composite shear wall piers. Results of finite element analysis of 98 SC wall piers are used to investigate the effects of wall aspect ratio, reinforcement ratio, slenderness ratio, axial load, yield strength of the steel faceplates, and uniaxial compressive strength of concrete on in-plane response, and to formulate (a) predictive equations to establish the trilinear lateral force versus lateral displacement response of SC wall piers up to peak strength, sufficient for seismic analysis of structures including SC wall piers and (b) a mechanics-based design equation for peak flexural strength, which addresses the interaction of co-existing shear and axial force. Design of Experiments is used to select the 98 piers. The baseline finite element model was formally validated using data from reversed cyclic, inelastic in-plane tests of four large-scale SC wall piers.

Examining the Impact of Micro Silica Gel Additive on the Compressive Strength and Water Absorption of Roller Compacted Concrete Pavement

<p>Roller compacted concrete pavement (RCCP) is one of the different types of concrete pavements which is considered as a new developing technology due to its rapid installation. However, RCCP is difficult to install in high thickness; therefore, it is essential to reduce the thickness of pavement while maintaining strength. Flexural strength and fatigue resistance are the most important parameters effective on design of thick pavements. These parameters are directly related to uniaxial compressive strength of concrete. Hence, this study determines and evaluates the compressive strength of 7-day and 28-day specimens. Given the durability of concrete pavements, particularly their penetrability against water, corrosive materials and minerals, the most important parameter is to reduce water absorption of RCCP. In order to increase strength and reduce water absorption of RCCP, different additives as well as a proper mix design can be significantly effective. This study examines the effect of various mix designs and different percentages of micro silica gel on RCCP. The suggested mix design is continuous aggregation and addition of 7% micro silica gel, which increases strength and durability of RCCP.</p>

Influence of the composition of powder-type SCC on conversion factors for compressive strength

Depending on practical considerations and standards, different types of test specimens are used for the determination of the uniaxial compressive strength of concrete. Appropriate conversion factors, also referred to as shape factors, are needed to convert the compressive strength as determined on one type of specimen to the equivalent compressive strength of another type of specimen. As such shape factors for vibrated concrete are influenced by the composition of the concrete, questions arise concerning the factors that affect the shape factors for powder-type self-compacting concrete (SCC). This paper describes the findings of an extensive research programme performed by three laboratories on the influencing parameters of the shape factors for SCC. Concrete composition parameters such as powder content, cement/powder ratio, water/cement ratio and the type of coarse aggregates, cement, filler and plasticiser appear to have little effect on the experimentally obtained shape factors. Any possible influence on compressive strength was overshadowed by experimental scatter.

Triaxial Behavior of Concrete Subjected to Dynamic Compression

AbstractExperimental research is presented in this paper to investigate the hydrostatic behavior of concrete under dynamic compression. By using the MTS servohydraulic testing system, strain rates from 10−5 to 3.5×10−2 s−1 were achieved. A hydrostatic pressure up to the uniaxial compressive strength of concrete was applied to the specimen with the help of the triaxial loading cell. A series of complete stress-strain curves was obtained for the specimens subjected to different combinations of strain rates and confining pressures, and significant enhancements of the material strength were observed. In particular, the experimental results suggest a clear coupling effect between the enhancements induced by the strain rate and the confining pressures. Finally, a set of empirical formulas is proposed to describe the enhancement of the compressive strength of concrete under different strain rates and relatively low confinement levels. The calculated results agree well with the data of the low confining pressure ...

Compressive Strength of Concrete in Flexural Critical Region of Reinforced Concrete Beam-Column Members

The compressive strength of concrete in flexural critical regions of reinforced concrete beam-column members is investigated experimentally and in terms of three-dimensional finite element predictions. Reinforced concrete beam-column members subjected to an axial load combined with single or double curvature bending were manufactured with special stirrups that minimize the confining effect of concrete by stirrups. Due to the existence of a beam-column joint near the flexural critical section at both ends of the members, the concrete on the compression fibers around the joint is subject to multiaxial compressive stress states; and the compressive stress in the region exceeds the uniaxial compressive strength of concrete. In the case of double curvature bending, the load-carrying capacities of the beam-column members which are measured experimentally and predicted by means of finite element analysis greatly exceed the moment and axial force interaction curve obtained from the uniaxial stress-strain curve of concrete.

An efficient three-dimensional solid finite element dynamic analysis of reinforced concrete structures

Most of the finite element analyses of reinforced concrete structures are restricted to two-dimensional elements. Three-dimensional solid elements have rarely been used although nearly all reinforced concrete structures are under a triaxial stress state. In this work, a three-dimensional solid element based on a smeared fixed crack model that has been used in the past mainly for monotonic static loading analysis is extended to cater for dynamic analysis. The only material parameter that needs to be input for this model is the uniaxial compressive strength of concrete. Steel bars are modelled as uniaxial elements and an embedded formulation allows them to have any orientation inside the concrete elements. The proposed strategy for loading or unloading renders a numerical procedure which is stable and efficient. The whole process is applied to two RC frames and compared against existing experiments in the literature. Results show that the proposed approach may adequately be used to predict the dynamic response of a structure. Copyright © 2005 John Wiley & Sons, Ltd.

Application of Neural Networks for Estimation of Concrete Strength

The uniaxial compressive strength of concrete is the most widely used criterion in producing concrete. Although testing of the uniaxial compressive strength of concrete specimens is done routinely, it is performed on the 28th day after concrete placement. At this point, it is too late to make improvements if the test result does not satisfy the required strength. Therefore, the strength estimation before the placement of concrete is highly desirable. This study presents the first effort in applying neural network-based system identification techniques to predict the compressive strength of concrete based on concrete mix proportions. Back-propagation neural networks were developed, trained, and tested using actual data sets of concrete mix proportions provided by two ready-mixed concrete companies. The compressive strengths estimated by the neural networks were verified by laboratory testing results. This study demonstrated that the neural network techniques are effective in estimating the compressive strength of concrete based on the mix proportions. Application of these techniques will contribute significantly to the concrete quality assurance.

Role of Silica Fume in Compressive Strength of Cement Paste, Mortar, and Concrete

Controversy exists as to why silica fume increases the strength of concrete when it is used as a partial replacement for cement. Some evidence supports the view that the increase in strength is due to an increase in the strength of the cement paste constituent of concrete. However, contradictory evidence exists that shows no increase in the strength of cement paste, but substantial increases in concrete strength, when silica fume is used. The latter evidence is used to support the theory that silica fume strengthens concrete by strengthening the bond between cement paste and aggregate. This study is designed to explain the contradictory evidence and establish the role played by silica fume in controlling the strength of concrete and its constituent materials. These goals are accomplished using cement pastes, mortars, and concretes with water-cementitious material ratios ranging from 0.30 to 0.39. Mixtures incorporate no admixtures, a superplasticizer only, or silica fume and a superplasticizer. The research demonstrates that replacement of cement by silica fume and the addition of a superplasticizer increases the strength of cement paste. It also demonstrates that cement paste specimens, with or without silica fume, can exhibit reduced strength compared to other specimens with the same water-cementitious material ratio if the material segregates during fabrication, thus explaining some earlier experimental observations. The segregation of cement paste is caused by high superplasticizer dosages that do not cause segregation of concrete with the same water-cementitious material ratio. Concrete containing silica fume as a partial replacement for cement exhibits an increased compressive strength because of the improved strength of its cement paste constituent. Changes in the paste-aggregate interface caused by silica fume appear to have little effect on the uniaxial compressive strength of concrete.

Discussion: Cube tests and the uniaxial compressive strength of concrete

Discussion: Cube tests and the uniaxial compressive strength of concrete

Cube tests and the uniaxial compressive strength of concrete

Summary The cube is undoubtedly the most convenient specimen to use when large numbers of crushing tests are required for concrete control purposes. The cylinder, or prism, on the other hand can give a much better estimate of the uniaxial compressive strength of concrete. The recent tendency has been to favour the adoption of the cylinder as the standard specimen, despite its shortcomings regarding convenience. The paper shows that variable differences can occur between the cube crushing strength and the uniaxial compressive strength, and then indicates how these differences can be greatly minimized by a suitable modification of the testing technique. This simple modification to the cube test enables the uniaxial strength to be determined very readily. The extremely convenient cube specimen can therefore now be used for uniaxial compressive strength determinations as well as for normal control purposes. The continued use of the cube as the standard form of test specimen is therefore recommended.