Concrete Grade Research Articles

Optimization of Technical Calculation of Precast Wall Application for Kawo Secondary Canal Improvement in Sempor Irrigation Area, Kebumen, Central Java

This study aims to perform technical calculations using precast lining in the repair of secondary channels. The planning data used included a concrete grade of fc 18.68 MPa and a reinforcement grade of fy 500 MPa. The service condition analysis was carried out by taking into account the loading during the most critical condition, where the channel is empty and active soil pressure and external water pressure are the main loads. The fixed load calculation was the main focus, where the active earth pressure (PD) was calculated by considering the soil-specific gravity, soil shear angle, and soil coefficient. The calculation results show that the PD reaches 12.24 kN, which gives an idea of the load that the structure has to bear. Furthermore, the internal force analysis provides a deeper understanding of the moments occurring at specific points in the structure. For example, the maximum negative moment at point A was calculated by considering the moments due to fixed load and transient load, which reached 12.73 kNm. This research contributes to improving efficiency and safety in the application of precast lining for secondary channel improvement.

AN ANN MODEL FOR PREDICTING SLUMP OF CONCRETE CONTAINING CRUSHED GLASS AND NATURAL GRAVEL

This study modelled the slump of concrete containing crushed glass and Bida Natural Gravel (BNG) based on deep learning algorithm using the MATLAB neural network toolbox. A total of 240 (150mm × 150mm × 150mm) cubes were cast from 80 mixes generated randomly using Scheffe’s simplex lattice approach. Slump was measured for each of the experimental points of fresh concrete before filling in the moulds. The resulting batch for each mix was used as input data while the laboratory results for slump was used as output data for the ANN-model. Hence a shallow multilayer supervised Neural Network was developed to model these data. The developed model would be able to predict concrete slump containing 0% - 25% crushed glass as partial replacement for fine aggregate, water- cement ratio ranging from 0.45 – 0.65 and concrete grade M15 – M25. The architecture of the network contained 6 input parameters: water to cement ratio, water, cement, sand, crushed glass and BNG, 20 neurons in the hidden layer and slump in the outer layer. The adequacy of the developed model was measured using Mean Square Error (MSE) and Correlation Coefficient (R). Results showed that 6:20:1 model architecture for slump model had an MSE values for training, validation and testing as: 1.84e-2, 5.81e-3, 3.64e-3, 1.73e-3 respectively. Regression values for training, validation and testing are: 79%, 94%, 96% and 79%. The study concluded that a shallow multilayer Neural Network architecture with 20 neurons in the hidden layer is sufficient for predicting concrete slump.

Using Waste Foundry Sand As Sustainable Construction Material

India's rapid industrialization and urbanization have led to substantial waste generation, posing significant environmental challenges. Among these wastes, the byproducts of metal industries, such as waste foundry sand (WFS), offer potential solutions for sustainable construction. This study investigates the feasibility of using WFS as a partial replacement for fine aggregate in M20 grade concrete. The experimental program involved incorporating WFS at varying percentages (0%, 10%, 20%, 30%, 40%, and 50% by weight) and assessing the impact on the compressive strength of concrete, complemented by the addition of a plasticizer (1% by weight of cement). The results demonstrated that up to 20% replacement of fine aggregate with WFS significantly enhances the compressive strength of concrete, achieving increases of 40.4% and 56.5% for 7 and 28 days of curing, respectively. Beyond 20% replacement, the compressive strength declined. This research highlights the potential for utilizing industrial waste in concrete production, promoting sustainable construction practices by reducing the reliance on natural resources and addressing waste management challenges.

A Review on Engineering Behaviour of Sustainable Concrete with Steel Mill Scale and the Effect of Admixture on Workability Improvement

Abstract: The integration of chemical admixtures and alternative materials in concrete production has become a focal point in advancing construction technologies. This study investigates the combined effects of superplasticizers and mill scale on the workability and compressive strength of M30 grade concrete. Three different superplasticizers—Auramix 200, SikaPlast®-3069 NS, and Master Polyheed 8126—are evaluated for their performance enhancements in concrete. Additionally, mill scale, an industrial by-product, is utilized to partially replace sand in varying proportions (0%, 20%, 40%, 60%, 80%, and 100%) to assess its viability as a sustainable aggregate alternative. The experimental phase is divided into three stages: initially assessing the workability and compressive strength of M30 concrete without admixtures; subsequently incorporating mill scale to observe its effect on concrete properties; and finally combining mill scale with each superplasticizer to maintain workability while evaluating the compressive strength. Slump cone tests are conducted to measure workability, and compressive strength tests are performed at 7, 14, and 28 days. Results indicate that the inclusion of superplasticizers significantly enhances workability, with Auramix 200 showing the highest improvement. The addition of mill scale up to 60% replacement level increases compressive strength, with a notable peak at 60% replacement for both plain and superplasticizer mixes. However, higher replacement levels (80% and 100%) result in reduced strength and workability. Among the superplasticizers, Auramix 200 exhibits the best overall performance in conjunction with mill scale. This study concludes that the strategic use of superplasticizers and mill scale can produce high-performance, sustainable concrete. Future research should explore long-term durability aspects and optimize mix designs for broader applications in construction

Engineering Behaviour of Sustainable Concrete with Steel Mill Scale and the Effect of Admixture on Workability Improvement

Abstract: The integration of chemical admixtures and alternative materials in concrete production has become a focal point in advancing construction technologies. This study investigates the combined effects of superplasticizers and mill scale on the workability and compressive strength of M30 grade concrete. Three different superplasticizers—Auramix 200, SikaPlast®-3069 NS, and Master Polyheed 8126—are evaluated for their performance enhancements in concrete. Additionally, mill scale, an industrial by-product, is utilized to partially replace sand in varying proportions (0%, 20%, 40%, 60%, 80%, and 100%) to assess its viability as a sustainable aggregate alternative. The experimental phase is divided into three stages: initially assessing the workability and compressive strength of M30 concrete without admixtures; subsequently incorporating mill scale to observe its effect on concrete properties; and finally combining mill scale with each superplasticizer to maintain workability while evaluating the compressive strength. Slump cone tests are conducted to measure workability, and compressive strength tests are performed at 7, 14, and 28 days. Results indicate that the inclusion of superplasticizers significantly enhances workability, with Auramix 200 showing the highest improvement. The addition of mill scales up to 60% replacement level increases compressive strength, with a notable peak at 60% replacement for both plain and superplasticizer mixes. However, higher replacement levels (80% and 100%) result in reduced strength and workability. Among the superplasticizers, Auramix 200 exhibits the best overall performance in conjunction with mill scale. This study concludes that the strategic use of superplasticizers and mill scale can produce high-performance, sustainable concrete. Future research should explore long-term durability aspects and optimize mix designs for broader applications in construction.

Examination of the stress-strain model for confined concrete considering the impact of corroded spiral bars

To examine the impact of corroded spiral bars on the confinement effect of concrete, a series of dry-wet cyclic accelerated corrosion tests and axial compression tests were performed on 36 RC (Reinforced Concrete) specimens. This study investigated the effects of various factors, including the degree of corrosion in spiral bars, the reinforcement configuration, and the concrete strength grade, on the axial compressive performance of confined concrete. The mechanical behavior of concrete, which was confined by corroded spiral bars, was analyzed by considering the corrosion characteristics, failure patterns, and load-carrying capacity of the specimens. A modified Mander model, which incorporates the influence of corroded spiral bars, was developed. The results indicate that increased corrosion accelerates specimen damage and reduces ductility. Stirrups show pull-off phenomena. A higher stirrup ratio enhances the bearing capacity and deformation capacity of specimen during destruction, while reducing longitudinal reinforcement buckling. Stronger concrete delays vertical cracking, increases bearing capacity, but reduces deformation capacity during destruction. The modified Mander model demonstrates high computational accuracy.

EFFICIENCY OF USING FIBER CONCRETE AS CORE FOR STEEL CONCRETE COLUMNS OF SQUARE CROSS SECTION

The article examines the effectiveness of using fiber concrete as a core for reinforced concrete columns with a square cross-section. For this, at the first stage, the calculation of a steel-concrete column with dimensions of 100×100×3 mm, length of 500 mm was carried out using as a core a cross-section of concrete grade C20/25. At the next stage of the research, based on the conditions of the same bearing capacity of the columns, cross-sections were selected using fiber concrete with steel and basalt fibers at different values of the thickness of the steel shell. Steel fiber "Chilyabinka" was used, which was introduced at the rate of 32,536 kg/m3 of concrete. Basalt fiber was used with a length of 12 mm, and was added in the amount of 0.2% of the mass of cement. The dependence of the area of the concrete core and the area of the steel shell on the thickness of the steel shell is plotted. A comparison of the cost and characteristics of reinforced concrete columns with the use of ordinary concrete and fiber concrete with two types of fibers as a core cross-section was also carried out: steel and basalt. Based on research, the following conclusions can be drawn that the use of fiber concrete as the core of a steel concrete column of rectangular cross-section significantly improves a number of characteristics. Thus, with the same bearing capacity and thickness of the shell, the cost of a column with a core made of steel fiber concrete is reduced by 15%, weight by 26%, cross-sectional size by 13% compared to concrete without fiber. The cost of a column with a core made of basalt fiber concrete is reduced by 12%, weight by 21%, cross-sectional size by 9% compared to concrete without fiber. By changing the thickness of the steel shell, you can also influence the characteristics of the column, in particular, reduce the cross-sectional dimensions and weight. But at the same time, the cost of the column increases. Keywords: fiber concrete, steel concrete, column, bearing capacity

Experimental and theoretical study on the bonding property between PC steel bar and concrete under monotonic and cyclic loading

To study the bond performance of the plain round steel bar for prestressed concrete (PC steel bar) in concrete, the bond tests were carried out on specimens with different concrete strength grades (C30, C40, C50 and C60) and bonding lengths (40 mm, 80 mm and 12 mm) under monotonic and cyclic loading. The test results showed that the bond stress-slip curves of specimens with different concrete strength and bonding lengths were similar under monotonic and cyclic loading, and the shape of hysteresis curves was symmetrical about the origin. The peak bond stress and residual bond stress decreased with the increase of bonding length, which increased with the increase of concrete strength. The slip corresponding to peak bond stress increased with the increase of bonding length and concrete strength. According to the test results, the equations for calculating the bond stress-slip curve, the peak bond stress and its corresponding slip under monotonic loading were obtained, respectively. Then the bond stress-slip model was proposed by providing the skeleton curve, hysteresis paths and rules under cyclic loading. By comparing the calculated results of the model with the test data, it has been proven that the model can predict the bond stress-slip curve between PC steel bar and concrete with different concrete strengths and bond lengths.

Eccentric compressive behavior of T-shaped welded multi-partition composite members

Six T-shaped welded multi-partition composite members were tested under eccentric compression loading by considering the influence of eccentricity and eccentric angle. The test results showed that no weld tearing occurred when the specimen was damaged, indicating that the two vertical welds could ensure the overall working performance of the specimen. The specimens exhibited the smallest bearing capacity when failing along the asymmetric axis, which was the most dangerous situation. The parametric analysis is conducted by a verified finite element model considering the influence of the slenderness ratio, section height-to-width ratio, section depth-to-width ratio, concrete and steel grade, steel ratio, and eccentric angle. If concrete contributes a larger proportion to the bearing capacity, the interaction curve of axial force and bending moment tends to protrude. Conversely, the interaction curve of axial force and bending moment gradually shrinks as the slenderness ratio increases. Based on this observation, a calculation method of T-shaped welded multi-partition composite members under eccentric compressive loading along the asymmetric axis is proposed by considering the effect of the slenderness ratio. Formulas for bearing capacity under biaxial eccentric compression are proposed based on the results of the parametric analysis.

Bonding characteristics between existing concrete substrate and high ductility geopolymer overlays under direct shear loading

High ductility geopolymer (HDG) looks promising as an exceptional repair material due to the faultless mechanical properties and environmental benefits. The interfacial bonding characteristics between existing normal concrete (NC) substrate and HDG overlay are the vital impact on the overall performance of repaired structures. This study presented the NC-HDG bonding behavior under the direct shear tests, and totally 45 specimens were designed with various concrete strength grades, interface roughness and elongations of HDG. To capture the fracture characteristics, the digital image correlation (DIC) technique was employed. Test results showed that the direct shear bonding strength (τu) had an increasing trend as the NC strength dropped or the interface roughness and elongations of HDG were increased, among the interface roughness affected the τu mostly, with the improvement amount of 185.07 %∼343.28 %. The direct shear strength ratio (defined as the ratio of τu to the inherent shear strength of NC) was ranged as 0.110∼0.489, i.e., at least half of shear strength of NC was lost during repairing. Based on the DIC measured results, the improvement of NC strength, interface roughness and elongations of HDG all delayed the interfacial crack initiation under direct shear loading. Moreover, the upper-bound limit analysis was adopted, a simplified method for predicting the direct shear bonding strength of NC-HDG interface was proposed and showed a sufficient precision.

Analysis of Bonding Properties of Corroded Reinforcement Concrete

In order to investigate the degradation of bonding properties between corroded steel bars and concrete, this study employs the half-beam method to conduct bond-slip tests between corroded steel bars and concrete after impressed-current accelerated corrosion of the steel bars in concrete. The effects of steel corrosion rate, steel bar diameter, steel bar strength grade, and concrete strength grade on the bonding properties between concrete and corroded steel bars were analyzed. The influence of different corrosion rates on specimens’ bonding strength and bond-slip curves was determined, and a constitutive relationship for bond-slip between corroded steel bars and concrete was proposed. The results indicate that the ultimate bonding strength of corroded reinforced concrete specimens decreases with increasing corrosion rate. Additionally, an increase in corrosive crack width leads to a linear decrease in bonding strength. Evaluating the decline in adhesive properties through rust expansion crack width in engineering applications is feasible. Furthermore, a bond-slip constitutive relationship between corroded steel bars and concrete was established using relative bond stress and relative slip values, which aligned well with the experimental findings.

Slenderness effects on concrete-filled square steel tube columns strengthened with CFRP grid-reinforced ECC matrix

This study presents an experimental investigation aim at evaluating the slenderness effects on concrete-filled square steel tube columns strengthened with a carbon fiber-reinforced polymer (CFRP) grid-reinforced engineered cementitious composite matrix. Thirteen columns were subjected to axial compression, with the studied parameters including the length-to-width (L/B) ratio, CFRP grid layer number, concrete strength grade, and width-to-thickness ratio of the steel tube. Test results revealed that slender columns experienced an increase in load-bearing capacity ranging from 27.1 % to 32.4 % after strengthening, while the ductility enhancement reached a peak of 52.0 %. A column with an L/B ratio of 5.87 exhibited slight bending deformation in a localized region upon failed, with CFRP grid ruptured at the corner. While columns with L/B ratios of 7.83 and 9.78 failed due to the loss of stability, displaying overall bending deformation. The increase in L/B ratio accelerated the loss of stability, resulting in a decrease in the ultimate load. As the L/B ratio increased from 2.97 to 5.93, 7.91 and 9.89, the ultimate loads of the strengthened columns decreased by 7.4 %, 9.2 %, and 15.4 %, respectively. A load-bearing capacity calculation model of slender strengthened columns was developed using the fiber element method. Through numerical analysis, a stability coefficient was introduced, and a simplified calculation formula was proposed to predict the stability bearing capacity.

Axial performance of concrete-filled GFRP tube columns jacketed by outer stainless steel tube and sandwiched concrete

The concrete-filled FRP tube (CFFT) column, a prevalent and crucial structural element in marine environments, requires reinforcement measures to enhance its operational performance. This paper introduces a novel strengthening technology involving sandwiched concrete and stainless steel tube jackets. By conducting axial compression tests on two CFFT columns and nine reinforced columns, the failure modes, load-axial deformation curves, and load-strain relationships were analysed in this study. Additionally, the influence of outer steel tube thickness (3.0 mm, 4.0 mm, 5.0 mm) and sandwiched concrete strength grades (C50, C60, C70) on the axial compressive performance of the reinforced columns was investigated. The findings indicated that the proposed reinforcement method effectively mitigated the brittle failure associated with the original CFFT column. The external stainless steel tube played a crucial role in restraining lateral deformation of the internal CFFT column, thereby enhancing the axial compressive bearing capacity. Through theoretical analysis on the components in reinforced columns, a calculation formula for the axial compressive capacity of the reinforced column was derived according to the unified theory and the double-shear unified strength theory.

Confinement-based direct design of square normal and high strength steel tube confined concrete (STCC) short columns

In this paper, a confinement-based direct design model is developed to estimate the axial compression resistance of square steel tube confined concrete (STCC) short columns, which differ from standard concrete-filled steel tube (CFST) columns in load application. While the load in CFST columns is applied to the entire section, it is applied to concrete only in case of STCC columns. Accordingly, STCC columns show superior confinement effect to the concrete core, which will be used directly in the design model. First, the experimental test results of axially-loaded STCC short columns were collected from the literature. The test resistances of the columns were then compared with the predictions obtained by EC4 (2004), American specifications (ANSI/AISC (2010) and ACI 318 R (2014)), AIJ (2001), British standard BS5400 (2005) and CISC (2007), as well as the available design models in the literature. This comparative study showed that all design codes as well as other design models are highly conservative and all do not have the same accuracy over the full range of steel tube slenderness. Then, the resistances of test specimens were used to propose a formula that evaluates the lateral confinement pressure (frp) provided by the steel tube on the concrete core. Finally, the confinement-based direct design model was proposed to estimate the strengths of square STCC short columns. The results of the proposed design model far outperform the available design predictions regardless of the slenderness ratio of the steel tube for all grades of steel and concrete.

Seismic Performance of Steel-Reinforced High Strength Concrete Joints Considering Bond Slip Effect

This study presents a solution for push-out failure for the staged bond-slip constitutive relationship between the structural steel and high strength concrete, taking into account the concrete strength grade, anchoring length, and stirrup ratio. The critical point coordinates for different stages are determined by the tests of 14 steel-reinforced high strength concrete (SRHSC) specimens. It is observed that with the increase in the concrete strength grade and anchorage length, the ultimate load of the specimens increased significantly, but the influence on the residual bond strength was not significant. The effect of the stirring ratio was mainly manifested in a slight increase in the initial bond strength. The formula for calculating SRHSC characteristic bond strength and characteristic slip value is established, and the bond-slip constitutive relation of SRHSC is proposed based on the tests. The material constitutive model considering the effect of bond-slip is implanted into the software in the case of the ABAQUS finite element platform. The material is applied to the numerical simulation analysis of the SRHSC exterior joints. The rationality and accuracy of the new material are verified by comparing the simulation results with the test results.

Compressive behaviour of self compacting concrete column strengthened by hybrid confinement of fibre reinforced polymer sheet and fibre rope

AbstractThe compressive behavior of self-consolidating concrete columns strengthened by hybrid confinement of polypropylene fiber rope and glass fiber-reinforced polymer sheet was investigated experimentally. We cast and tested eight column specimens under axial compression load. (Six confined SCC columns and two conventional SCC columns.) The concrete grade utilized is SCC M40. For reinforcement, the SCC columns are enclosed with GFRP wrap and polypropylene fiber rope in various volumetric ratios. The compressive resistance of a confined SCC column, strength enhancement, stress-strain relationship, ductility ratio, and load deflection relationship are the parameters studied. The results are compared to establish the adequacy of the confinement. The wrapping of GFRP increases the load-carrying capacity and modulus of elasticity.

Evaluation of Structural Stability of Four-Storied building using Non-Destructive Testing Techniques

This paper mainly dealt with the evaluation of the structural stability of four storied building using non-destructive on-destructive testing methods. During the construction stage, there are many tests available to assess the excellence of concrete. The quality of concrete mainly depends on the quality of materials, concrete grade, and water-cement ratio. In the case of existing structures, to check the quality of concrete destructive tests are not possible, meanwhile, concrete quality will be assessed by using non-destructive testing (NDT) techniques such as rebound hammer, ultrasonic pulse velocity (UPV) etc. In this present study, an attempt has been made to check the quality of concrete in an existing four-storied building using non-destructive testing methods such as rebound hammer test and ultrasonic pulse velocity test. Moreover, the stability of the structure was also assessed. Non-destructive testing method was chosen since existing information of the structure was unavailable. Test results showed that the basement (B1) was susceptible to corrosion, and the compressive strength was not in the recommended range. Ultrasonic pulse velocity (UPV) results also proved that the average quality of the concrete was poor. Hence, significant suggestions were given for necessary retrofitting measures to improve the stability of the structure.

Experimental Analysis of Light Weight Concrete by Using of Light Weight Aggregat

This project investigates light weight concrete by replacing coarse aggregate with Light weight Aggregate (LWA). The methodology involves meticulous data collection, analysis, material selection, and the design of M30 grade concrete. It aims to evaluate how different proportions of LWA replacement affect concrete properties. Beginning with data gathering on conventional concrete mixes and LWA properties, material selection balances structural integrity with light weight characteristics. Varying percentages of LWA replacement (0%, 20%, 40%, and 50%) are then incorporated into the design phase, followed by precise mixing to maintain consistency. Concrete specimens undergo tests including slump, compaction factor, cube casting, and rebound hammer testing to evaluate workability, compact ability, and compressive strength. The project highlights the importance of the compressive test in determining concrete strength. Through meticulous analysis, it discusses LWA's effects on properties like workability, density, and durability, contributing insights into sustainable construction practices and emphasizing empirical analysis for engineering material selection. Key words LWA-Light Weight aggregate, LWC- Light Weight concrete, LECA- Light Weight expended clay aggregate, conplast SP430(G), Fosroc, SSD – Saturated Surface Dry, DRY WEIGHT – Dry Weight of Material.

Experimental Study on the Bonding Performance between Shaped Steel and High-Strength Concrete

The integration of steel fibers into high-strength concrete (HSC) offers a solution to address the brittleness and limited ductility typically associated with conventional HSC structures. To investigate the bonding properties between shaped steel and high-strength concrete with steel fiber (SFRC), thirteen tests of the shaped steel/SFRC specimens are conducted to explore the effects of various factors such as steel fiber volume ratio, concrete strength grade, reinforcement ratio, steel embedment depth, and cover thickness on bond–slip behavior. Three distinct failure modes, such as pushout failure, bond splitting, and yielding failure of steel, are identified during the pushout tests. Three different types of bond strength, such as the initial bond strength, the ultimate bond strength, and the residual bond strength, are observed from the load–slip curves between the shaped steel and concrete. By incorporating nonlinear spring elements, a numerical model for accurately simulating the bond performance between the shaped steel and SFRC specimens is developed. The bond strength between the shaped steel and concrete increase as the concrete strength, cover thickness, steel fiber volume ratio, and stirrup ratio increase, while it decreases as the steel embedment depth increases. A model for the bond strength between shaped steel and SFRC is developed, and it agrees well with the test data.

Economic and Environmental Benefit Analysis between Crumb Rubber Concrete and Ordinary Portland Cement Concrete

Although manifold empirical studies have identified the mechanical properties of crumb rubber concrete (CRC), a comparative analysis of economic and environmental benefits between CRC and ordinary Portland cement concrete (OPCC) is not explored. In this paper, a quantitative meta-analysis between CRC and OPCC is conducted to explore optimized design strength, and a comparative analysis of the economic and environmental benefits of the two materials is undertaken. Considering cost price as the economic index and CO2 emissions per cubic meter of concrete as the environmental index in the materialization stage, CRC and OPCC were compared with different mix designs to achieve grades of similar strengths. Upon replacing less than 20% of natural fine aggregates in concrete with crumb rubber, while retaining the cement content, an increase of 6% in the cost price was achieved for CRC with 30–40 MPa strength grade. Apart from the aspect of mining and transportation of natural aggregates, the reduction of CO2 emissions by means of CRC adoption was verified in the treatment process of waste tire incineration. The results show that CO2 emissions from CRC decreased by 15–17% when compared with OPCC for 30~40 MPa grade concrete. The research conclusion can serve as a theoretical basis for the engineering application of CRC with the same strength, and make certain contributions to the industrial application of crumb rubber aggregates and the sustainable treatment of waste tires.