Reactive Powder Concrete Columns Research Articles

Axial compressive behavior of partially encased composite reactive powder concrete columns after high-temperature exposure

Replacing ordinary concrete in partially encased concrete (PEC) columns with high-strength and durability reactive powder concrete (RPC) significantly improves their axial capacity and suppresses local buckling of the steel section. To study the axial mechanical performance of partially encased composite reactive powder concrete (PEC-RPC) columns after exposure to high temperatures, axial compression tests of eight PEC-RPC column specimens were designed and conducted. Thermal response, failure modes, axial load-vertical displacement curves, and strain-axial strain curves of different specimens were observed considering the effects of link spacing, cross-sectional dimensions, constant temperature duration, and cooling methods. Results indicate: PEC-RPC columns exhibited whitening on the surface of RPC after high-temperature exposure, specimens with the largest link spacing experienced RPC peeling due to concentrated thermal stress, exacerbated by spraying water, which created a stress difference between the surface and the interior, resulting in RPC peeling. The deeper the thermocouple was embedded, the lower the measured temperature. Additionally, due to the significantly lower thermal conductivity of RPC compared to steel, the temperature at measurement points within the RPC is much lower than that at the steel web. The failure mode of PEC-RPC columns after axial loading was characterized by the crushing of RPC and local buckling of section steel. The larger the link spacing, the more prone it was to multi-layer buckling, and columns with larger cross-sectional sizes tended to exhibit shear failure. The characteristic value of mechanical performance showed higher sensitivity to cross-sectional dimensions, but relatively lower sensitivity to link spacing and constant temperature duration. As the cross-sectional dimensions increased from 150×150 mm to 250×250 mm, the peak load, residual bearing capacity, stiffness, and ductility increased by 72.51–164.86 %, 89.8–173.6 %, 61.85–151.47 %, and 13.72–31.46 %, respectively. Finally, based on partition constraint theory and superposition principle, a simplified method for calculating the axial mechanical performance of PEC-RPC columns after exposure to high temperatures was proposed.

Mechanical Properties of Steel-Reinforced Reactive Powder Concrete Columns with Different Geometrical Dimensions After High-Temperature Exposure

Mechanical Properties of Steel-Reinforced Reactive Powder Concrete Columns with Different Geometrical Dimensions After High-Temperature Exposure

Experiments and analytical model for axial strength of FRP-reinforced reactive powder concrete circular columns under axial compression

Although various experimental studies have been performed in the literature to explore the behavior of glass fiber reinforced polymer (glass-FRP) reinforced conventional concrete columns, no study focused on the axial performance of glass-FRP-reinforced reactive powder concrete (RPC) columns (GRPC columns) subjected to compression. Therefore, the current struggle investigates the behavior of nine GRPC columns through experimental testing, finite element analysis (FEA), and theoretical models on the circular samples with 250 mm diameter and 1000 mm length under axial compression. Steel fibers are added to RPC to minimize brittleness and to improve the strength of RPC. Moreover, a parametric study is planned to utilize the suggested FEA model for exploring the effects of various variables of GRPC columns on axial structural performance. The test findings showed that the GRPC columns become more ductile with the addition of fibers and a reduction in the vertical distance between the glass-FRP hoops/ties. The failure of GRPC columns occurred in the middle region of the samples with the delayed spalling of the concrete cover. The suggested analytical model based on the 600 data points presented higher accuracy than previous theoretical models. The recommended FEM for the axial capacity and associated axial shortening of examined samples portrayed errors of 3.25% and 4.65%, respectively. Considering the axial contribution of glass-FRP longitudinal bars and the transverse confining mechanism of FRP stirrups, the recommended theoretical model for the axial capacity of GRPC column samples performed well for the test findings of the examined samples with R2 = 0.842, MSE = 139.559, MAE = 195.538, and RMSE = 200.756.

Eccentric bearing capacity of steel reinforced reactive powder concrete columns after high temperature exposure

The three-dimensional nonlinear finite element model of steel reinforced reactive powder concrete (SRRPC) column was created to analyze mechanical properties after high temperature. Effect of temperature on mechanical behaviors of RPC, section steel and steel bars were taken into account in model. Accuracy of the temperature distribution and the prediction of eccentric bearing capacity after high temperature was verified by comparing experimental results with numerical results. Effects of eccentricity, loading angle, RPC strength, section steel strength and steel ratio on eccentric bearing capacity after high temperature were analyzed. Findings indicate that: there are two typical failure modes of SRRPC columns after high temperature under different eccentric loads, including small and large eccentric compression failure. As eccentricity has increased, residual bearing capacity declines obviously. Increase of RPC strength will greatly increase residual bearing capacity, and improve ductility to a certain extent. Increase of section steel strength and steel ratio can improve residual bearing capacity to a certain extent. Residual bearing capacity is mostly unaffected by the loading angle. Finally, the calculation formula of normal section bearing capacity of SRRPC bias column after high temperature was established based on limit state design method, which has high accuracy and can provide reference for identifying and strengthening composite structures following fire.

Axial strength of fibrous reactive powder concrete circular columns

In this paper, a formula is proposed to calculate the nominal axial strength (Po) of fibrous reactive powder concrete (RPC) columns reinforced with steel fibres of different geometries and volume contents. The formula takes into account the effects of concrete, longitudinal reinforcement, transverse constraints, geometry of steel fibres and their volume content. A comparison is made with existing formulations that consider only for concrete and steel reinforcement. The proposed formula has been verified and validated by the experimental results of different types of steel fibre reinforced concrete (SFRC) columns in the literature. The results show that the current formulation considering only concrete and reinforcement significantly underestimatesPo of fibrous RPC columns. Furthermore, it is found that the proposed formula well predicts the nominal axial strength for fibrous RPC columns with an accuracy of 97–99%.

Fire resistance of steel reinforced reactive powder concrete columns

Steel reinforced reactive powder concrete (SRRPC) columns have been widely used in structures due to their excellent mechanical properties. However, owing to inadequate experimental data and a lack of design basis for SRRPC columns at high temperatures, which limits the application and development of this structure in practical engineering. Five SRRPC columns with different loads were experimentally investigated at high temperatures. Additionally, 15 sets of specimens were analyzed by using numerical simulation method of thermo-mechanical coupling, and the rules of steel ratio, rebar ratio, and number of heating surfaces on the fire resistance of SRRPC columns were obtained. The test results revealed that the fire resistance decreased by 52.7% when the axial compression ratio increased from 0.2 to 0.6; The fire resistance increased by 17.79% when the steel ratio increased from 4.08% to 10.21%; The fire resistance increased by 3.24% when the rebar ratio increased from 0.83% to 2.76%; The fire resistance decreased by 28.95% when the number of heating surfaces increased from single-face heating to four-face heating. According to the variation rule of each parameter, the correlation degree of each parameter on the fire resistance was obtained, it concluded that the axial compression ratio had the highest correlation degree, followed by the number of heating surfaces, while the correlation degrees of steel ratio and rebar ratio were relatively small. A formula was proposed to predict the fire resistance of SRRPC columns, which can provide a reference for fire resistance evaluation, repair and reinforcement of SRRPC structures in fire.

Nonlinear-finite-element analysis of reactive powder concrete columns subjected to eccentric compressive load

AbstractStudies on the behavior of reactive powder concrete (RPC) columns under eccentric loading are limited. The effect of materials used in manufacturing these RPC columns has not yet been investigated. This research aimed to perform a nonlinear-finite-element analysis to determine the load-carrying capacity and displacement of RPC columns made of different RPC mixes and subjected to various loading eccentricities. This research investigates two types of parameters. The first parameter is the column’s geometric parameters (the heightLand the load eccentricity distancee). The second is the RPC material parameter (regarding the silica fume or fly ash used as pozzolanic material and the type of fibers used, whether steel or glass fiber). Results indicate that eccentric-loaded slender columns exhibit much less load-carrying capacity than the corresponding short columns. The 2 m-long columns with eccentricity ratioe/t= 0.2 resulted in a 65% average reduction in the ultimate load (Pu) compared to the corresponding 1 m-long columns. Using fly ash as a pozzolanic material instead of silica fume reduces the ultimate load (Pu) of an RPC column by an average of 60%. Using glass fibers instead of steel fibers also reduced Pu by 50%. The average percentage increase in the maximum vertical deflection (Δymax) of the short column (L= 1 m) is found in the range of 18–31% for eccentricity ratioe/t= 0.1 but 45–69% fore/t= 0.2. In contrast, for a slender column (L= 2 m), the percentage increase in Δymaxis in the range of 10–30% for bothe/t= 0.1 and 0.2.

Study on the Stress Performance of an Incompletely Prefabricated Profile Steel Reactive Powder Concrete Column in High-Rise Modular Buildings

In this study, 11 PSRPC column specimens were designed and fabricated in order to investigate the stressing performance of incompletely prefabricated steel reactive powder concrete (PSRPC) columns and were subjected to static loading tests. The effects of the strength grade and steel content of reactive powder concrete (RPC) on the axial compression performance of PSRPC columns and the effects of the steel content and eccentricity on the eccentricity performance of PSRPC columns were investigated. The test results show that the external prefabricated RPC, the internal steel section and the internal cast-in-place RPC of the PSRPC column work well together. The damage morphology of the specimens and the load–displacement and strain relationships were analysed, and the damage mechanism and the main factors influencing the compressive load capacity of the PSRPC columns were investigated. The test results are compared with the calculation results of the Chinese code (JGJ 138-2016) and the European and American codes (AISC-LRFD), and the applicability of the existing codes is discussed. Based on the hoop restraint action and limit state design method, formulae for calculating the axial and partial compression load capacity of PSRPC columns were established. The calculated values were in good agreement with the test values, and the calculation errors were within 10%.

Seismic performance of steel-reinforced reactive powder concrete columns

The seismic performance of the innovative steel-reinforced reactive powder concrete (SRRPC) composite columns was evaluated via the cyclic experiments considering the steel shape ratio, axial compression ratio and the stirrup ratio. The SRRPC columns generally exhibited appreciable seismic behavior, great crack-resistance and excellent anti-spalling property. It was found that increasing the steel shape ratio from 4.20% to 5.35% can significantly enhance the ductility and the energy dissipation capacity. As the axial compression ratio increased from 0.1 to 0.3, the peak lateral load increased but the ductility significantly decreased. Increasing the stirrup ratio from 1.57% to 2.52% was not helpful for seismic performance in the pre-peak zone but was beneficial to the strength and ductility in the post-peak zone. Moreover, the average strength loss of the SRRPC columns with low axial compression ratio at the 4.5% drift ratio was less than 12.5%, satisfying the modern seismic drift criteria. Two coefficients, βtu and k, for predicting the equivalent tensile strength were identified and compared to the suggested values from the specifications JGJ/T 465-2019 and T/CCPA 35-2022, respectively. An analytical model was successfully developed to predict the lateral load-bearing capacity. Good agreements were found between the experimental and analytical results.

Compression behavior of reactive powder concrete confined with high‐strength spiral stirrups

AbstractThe lateral confinement of stirrups can improve the load‐bearing capacity and ductility of reactive powder concrete (RPC) columns. To explore the compression behavior of RPC confined with high‐strength stirrups, 45 specimens were prepared and tested under axial compression. The concrete strength was in the range of 99.86–138.24 MPa, the tensile strength of stirrups was Grade 800, Grade 970, and Grade 1270, and the volumetric ratios of stirrups were in the range of 0.9%–2.0%. The results showed that the failure modes of RPC confined with stirrups were shear expansion failure. The compressive strength and ductility of confined RPC were improved with the increase of stirrups volumetric ratios, while stirrups strength slightly affected the compressive strength and ductility. In addition, the peak stress, peak strain, and residual stress prediction models were proposed. Furthermore, the ductility index prediction models were proposed, which can be applied to determine the volumetric ratio of stirrups in stirrups confined concrete columns.

Mechanical properties of steel reinforced reactive powder concrete columns under axial compression

With the continuous development of building structures and the increasing demand for use, the composite structure of steel reinforced reactive powder concrete (SRRPC) with excellent bearing capacity, stiffness, ductility, fire resistance and seismic performance was proposed. In this paper, the SRRPC column model was established by finite element software ABAQUS to investigate mechanical characteristics, and consistency within the model and the test results were verified from the aspects of failure phenomenon, load-displacement curve and bearing capacity. On this basis, the influence of calculated length, section steel strength, reinforcing bar strength, stirrup ratio and concrete strength on the mechanical characteristics of SRRPC columns was investigated. The consequences show that: (1) The bearing capacity rose with the rise of concrete strength, section steel strength, reinforcing bar strength and stirrup ratio, and decreased with the rise of calculated length. (2) On the basis of sensitivity analysis of parameters, bearing capacity is highly sensitive to concrete strength and section steel strength, generally to stirrup ratio and calculated length, and minimally to reinforcing bar strength. (3) The load entering the elastic-plastic stage increased with the rise of concrete strength, section steel strength and stirrup ratio, and decreased with the increase of calculated length. (4) The stiffness increased in each phase with the rise of concrete strength, section steel strength, reinforcing bar strength and stirrup ratio, and changed the most in phase C (0.5–0.75 Pu). The stiffness in each phase decreased with the increase of the calculated length, and changed the most in phase B (0.25∼0.5 Pu). Finally, the calculation method of bearing capacity was proposed.

Axial compressive behavior of steel-reinforced reactive powder concrete short columns

The conventional steel-reinforced concrete (SRC) composite columns are successfully applied in the construction of high-rise buildings and infrastructures. However, the further application is significantly limited by problems such as large self-weight and poor crack-resistance. In this study, an innovative steel-reinforced reactive powder concrete (SRRPC) column was developed to be a new alternative to the traditional SRC column. Four SRRPC short columns, considering the effect of longitudinal reinforcement ratio, steel shape ratio and transverse stirrup ratio, were axially loaded. It was found that the SRRPC column has sufficient axial compressive strength which considerably increased with the increase of these test parameters. Furthermore, increasing the stirrup ratio can effectively improve the post-peak strength. The numerical parametric analysis showed that the axial compressive strength was mainly affected by the compressive strength of the reactive powder concrete (RPC). The nominal-strength models of the existing specifications (EC 4, ACI 318, JGJ 138 and AISC 360) exhibited large conservation in predicting the axial compressive strength. A confined model was successfully developed and reasonable agreements were found between the experimental and predicted axial compressive strengths.

Axial compression capacity analysis of prefabricated steel reactive powder concrete columns in prefabricated modular buildings

This article proposes a prefabricated steel reactive powder concrete (PSRPC) component. Axial compression tests are conducted with five 3m full-scale column specimens to investigate the specimen damage and failure process and to measure the axial displacement, strain and ultimate bearing capacity in order to study the influences of the RPC strength and the section steel flange thickness on the mechanical properties of the PSRPC. The tests show the following. The ultimate failure mode of the PSRPC is column end splitting. During the loading process, the RPC and the section steel work compatibly, and their strengths are given full play. The lateral effect of the RPC on the section steel and the composite confinement effect of the stirrups and section steel on the RPC core significantly increase the ultimate bearing capacity of the PSRPC, and these effects increase with an increase in the RPC strength. The confinement effect on the RPC core in the enclosed region increases with an increase in the section steel flange thickness, that is, the thicker the section steel flange, the larger the portion of the load taken by the RPC core and the higher the ultimate bearing capacity of the PSRPC. The finite element analysis of PSRPC specimen is carried out by ANSYS software, and the simulation results are in good agreement with the test results. A method for calculating the axial bearing capacity of a full-scale column is proposed, taking the confinement effect of the stirrups and section steel on the RPC core into account.

Seismic Behavior of GFRP Tube Reactive Powder Concrete Composite Columns With Encased Steel

To obtain the seismic behavior of glass fiber–reinforced polymer (GFRP) tube reactive powder concrete composite columns with encased steel (GRS), a total of 17 full-scale GRS columns were designed in this study. The parametric studies were conducted to explore the influence of factors such as the diameter of GFRP tube (D), thickness of GFRP tube (t), number of fiber winding layers (n), fiber winding angle (θ), axial compression ratio (λ), compressive strength of reactive powder concrete (fc), the area of encased steel (As), and strength of encased steel (fsy) on the seismic behavior of the composite columns. The finite element models of this kind of columns were established by ABAQUS finite element software, and the seismic behavior analysis for GRS composite columns was carried out. The results show that all the specimens exhibit good ductility and strong deformation ability. The stiffness degradation of specimens significantly slows down with the increase of D, fsy, and λ. The energy dissipation capacity of specimens can be improved by increasing D and λ, while the increase of As and fsy leads to the decrease of the energy dissipation capacity. By observing the failure mode of such composite columns, local bulging occurs in the foot area of the columns. Based on the statistical analysis of the calculated results, the restoring force models for GRS composite columns are proposed, which agree well with the simulated results. The restoring force models can provide reference for the elastic-plastic seismic response analysis of this kind of composite columns.

Discrete finite element model of reactive powder concrete columns confined with fiber reinforced polymer

Numerous finite element methods have been widely used to predict the response of normal/high strength concrete columns confined with Fiber Reinforced Polymer (FRP) under different loading conditions. In this regard, simulating the response of FRP-confined reactive powder concrete (RPC) columns has been less emphasized. The present study aimed to propose a finite element model based on fiber finite element methodology in order to predict the behavior of FRP confined RPC columns under axial compressive load with different eccentricities. The columns were modeled with a nonlinear beam-column element with two nodes with distributed plasticity. In addition, the proposed finite element model in the present study indicated its simplicity, low computational efforts, and flexibility by adopting a perfect bond between RPC and FRP. Further, the obtained results from the finite element analysis were compared to those from available tested specimens. Based on the comparisons, the proposed model can provide highly satisfactory predictions. Finally, the proposed model can be useful for efficient applications in practical engineering projects.

Experimental investigation on the post-fire performance of reactive powder concrete columns

The increased use of reactive powder concrete (RPC) in concrete structures has attracted attention towards the structural behavior of RPC in fires. This work examines experimentally the performance of RPC and NSC columns subjected to 25% of the ultimate load and exposed to direct fire flame for a period of 30 and 60 min at various temperature levels. The paper aims to evaluate the maximum temperature level and fire duration that can be withstood by this type of concrete columns. The results show that the failure mode of RPC columns without reinforcement is a sudden shear failure, whereas the failure mode of reinforced RPC columns is a crushing failure with rupture of certain ties. The RPC columns at high temperatures spall intensively; additionally, the ultimate strength clearly decreases compared to the NSC columns at the same conditions.

Experimental research on seismic behavior of concrete-filled reactive powder concrete tubular columns

Concrete-filled reactive powder concrete (RPC) tube (CFRPCT) is a cement-based tubular composite column system, which combines the excellent compressive strength and the toughness of RPC and the lateral confining action from hoops. The novel composite system has the potential to be used in severe environment. To evaluate the seismic performance of CFRPCT columns, a series of low-cycle lateral loading tests were performed on eight model columns, including a bench-mark conventional reinforced concrete specimen and seven CFRPCT model columns, subjected to combine constant axial load and quasi-statically applied cyclic lateral loading. Volumetric hoop ratio, configuration of hoops, compressive strength of inner concrete and lateral loading procedure were selected as test parameters. Experimental results show that contrast to conventional hoop-confined concrete column, the failure of CFRPCT columns is characterized with well distributed cracks, without severe RPC cover spalling or crushing. The CFRPCT columns exhibited significantly higher initial stiffness, lateral load carrying capacity, ultimate lateral displacement, energy dissipation and smaller residual deformation as compared with those of the control column. An analytical model was also proposed for predicting the flexural strength of CFRPCT columns by considering the confinement effects.

Study on the compression performance of steel reactive powder concrete columns

In this study, the mechanical properties and failure characteristics of steel reactive powder concrete columns with different strength grades were investigated through compression testing. Six steel reactive powder concrete columns were tested; three columns underwent axial compression testing and three columns underwent eccentric compression testing. The results of the axial compression testing showed that steel and reactive powder concrete could work cooperatively at the initial stage, and the final column failure mode was primarily splitting failure at the end of the column, with the formation of a main crack in the longitudinal direction extending to the middle of the column. The results of the eccentric compression testing showed that the eccentrically loaded steel reactive powder concrete columns had comparatively strong deformability. The columns presented ductile failure mode under the eccentric load with 0.2 eccentricity. The final failure of the column involved a sudden increase in the horizontal crack width on the tension side, the steel flange on the tension side reached the yield state, the reactive powder concrete in the middle of the compressive side was crushed, and the reactive powder concrete surface layer burst open and partially spalled off. According to the test results and with reference to the relevant standards, equations for calculating the approximate ultimate bearing capacities of axially and eccentrically compressed reactive powder concrete columns were proposed.

The Fire Exposure Effect on Hybrid Reinforced Reactive Powder Concrete Columns

This paper offers an experimental investigation of the fiber reinforced reactive powder concrete columns' behavior after exposure to fire and improvements made to improve column resistance against fire. This study is mainly aimed to study the experimental behavior of hybrid reinforced columns produced by reactive concrete powder (RPC) and exposure to the flame of fire at one side and subjected to eccentric load. The experimental methodology consists of sixteen RC columns that organized into four groups based on the variables used in this research: (SF) steel fibers, (PP) polypropylene fibers, (HB) hybrid fibers, (PPC-SF) hybrid cross-section (steel fiber reactive powder concrete core with polypropylene fiber reactive powder concrete cover). All columns were tested under 60 mm eccentric load and the burn columns were exposed to fire for different duration (1, 1.5 and 2) hours. The results indicated that (SF-RPC, PP-RPC, HB-RPC, PPC-SFRPC) columns exposed to a fire flame for the period 2 hours, lost from their load capacity by about (54.39, 40.03, 34.69 and 30.68) % respectively. The main conclusion of this paper is that the best fire resistance of the column obtained when using a hybrid cross-section (steel fiber reactive powder concrete core with polypropylene fiber reactive powder concrete cover).

Behavior of hybrid reinforced concrete columns

This paper involves an experimental investigation to study the behavior of short rectangular columns cast with hybrid concrete, to compare the strength, stiffness and toughness provided by the hybrid structural system and the results collected may be used as basic data for future development of design models for this combination of materials.Seven columns were cast and tested under concentric loading; the variables studied included the diameter of steel bars for both longitudinal and lateral reinforcement. The dimensions of rectangular columns were: 100 mm x 200 mm x 740 mm high. Two columns were cast as full conventional concrete and full reactive powder concrete columns acted as control specimens. The remaining five were cast as hybrid columns having the conventional concrete at the core and surrounded by a 40 mm thickness of reactive powder concrete, with 1% micro steel fiber.The combination of these two types of concrete into the hybrid concrete columns was very useful because it enhanced the ultimate capacity of the columns with respect to the conventional concrete in about 179% compared to the enhancement produced due to using the reactive powder concrete alone which was 203%, therefore, it was concluded that using this hybrid concrete combination in concrete industry would be more economical than the use of reactive powder concrete; moreover, based on the mode of failure observed, it would be safer to use the hybrid structural system because of the destructive type of failure for columns cast with conventional concrete. Increasing the diameter of the main reinforcement gave an average increase in the percentage of the failure load with respect to the conventional concrete column of about 179% compared to the increase in the diameter of the ties which gave an average increase of 185%; which leads to the conclusion that the effect of lateral reinforcement was more pronounced than the effect of the longitudinal reinforcement in hybrid columns, due to the increase in confinement produced by both the reactive powder concrete cover in the hybrid concrete columns and the ties represented by the lateral reinforcement.