Compressive Strength Of Concrete Increases Research Articles

A novel bio-based water reducer for concrete application: Facile process and techno-economic analysis of xylonate bioproduction from lignocellulosic residues

The xylonate was bioproduced directly from lignocellulosic residues, and the application properties of crude xylonate powder were investigated with a promising potential as a bio-based concrete water reducer. The overall integrated process was evaluated on the view of mass balance and techno-economic analysis using Aspen Plus modeling. 56 g/L of calcium xylonate (XA-Ca) can be obtained within 8 h from acidic corncob hydrolysate (ACH) at a 100 % yield with the whole-cell catalysis of Gluconobacter oxydans. At the addition of 0.2 wt% in the dry concrete content, XA-Ca powder and sodium xylonate powder prepared from pure xylose and ACH could reduce water used in concrete by 15 %, 14 %, 13 %, and 13 %, respectively. XA-Ca from ACH led to a 33% increase in concrete compressive strength and a 24% increase in concrete flexural strength at day 7 compared to the blank group. The techno-economic analysis showed the minimum XA-Ca powder price to be $ 0.806/kg which can be economically feasible. This study provides a practical and economical process prototype for the industrial concrete water reducer application of novel bio-based xylonate produced from lignocellulosic residues.

Variation of dynamic elasticity modulus with experimentally determined concrete compressive strength

In reinforced concrete structures, one of the most important factors for structural safety is the quality of concrete. The first thing that comes to mind for concrete quality is the compressive strength of concrete. However, properties such as elasticity modulus are also among the properties that determine concrete quality. Since concrete is a brittle material, different methods are used to determine dynamic elasticity modulus. In practice, dynamic elasticity modulus of concrete can be identified by utilizing concrete compressive strength value. In this context; compressive strength tests were performed on a series of concretes accordingly relevant standards. Since it is difficult to determine elasticity modulus from the stress and strain relationship, the dynamic elasticity modulus values in this study was calculated using empirical formulas according to TS 500-2000, ACI 318-95 and CEB-FIP 1978 on the basis of experimental data in this study. The relationship between the calculated dynamic elasticity modulus values and concrete compressive strength was analyzed. From the study, it is concluded that as concrete compressive strength increases, dynamic elasticity modulus increases for the concrete specimens.

Evaluation of compressive strength of concrete durability degradation in dry and wet environments using destructive and non-destructive testing

To develop an effective non-destructive testing (NDT) method to assess the strength of concrete in dry and wet cyclic environments, concrete compressive strengths were evaluated of six different mix ratios in this study using ultrasonic method, rebound method and quasi-static compression tests indoors. Firstly, the results of concrete indoor quasi-static compressive strength tests were compared with the NDT results and the optimum NDT methods applicable to different concrete strength classes were determined. Subsequently, an in-situ NDT evaluation of concrete gates exposed to dry and wet environments for a long-term period was carried out based on the results of the laboratory indoor tests, and the degradation mechanism of concrete strength under dry and wet cyclic conditions was revealed by rebound method testing, borehole coring, and industrial computerized tomography (CT) scanning. The results show that the concrete strength obtained by the ultrasonic rebound method is closer to the actual value when the initial strength of concrete is less than 30 MPa; When the initial strength of concrete is between 30 and 40 MPa, the concrete strength obtained by the rebound method is closer to the actual value; When the initial strength of concrete is greater than 40 MPa, the concrete strength obtained by the rebound and ultrasonic rebound methods differ greatly from the quasi-static compressive strength. In addition, the compressive strength of concrete increases and then decreases with the number of dry and wet cycles increases. In the early stage of the dry and wet cycle, the main reason for the increase of the concrete strength is that the filling of the pores by the hydration products reduces the porosity of the concrete; As the number of dry and wet cycles increases, the hydration products absorb water to expand and lose water to shrinkage, which leads to microcracks, and this is the main reason for the decrease of the concrete strength in the late stage of the dry and wet cycle.

Early age dynamic mechanical properties of basalt fiber reinforced early strength concrete

AbstractThe dynamic compression test was carried out on basalt fiber reinforced early strength concrete (BFRESC) with ages of 4–24 h by the split Hopkinson pressure bar (SHPB) test system. The effects of curing age and basalt fiber content on dynamic mechanical properties of ESC was analyzed. The result shows that the dynamic compressive strength and specific energy absorption of BFRESC at early ages increase continuously with the increase of fiber content. The dynamic compressive strength of concrete at the early ages increases exponentially with the strain rate. With the increase of curing age, the strain rate sensitivity of dynamic compressive strength of concrete increases gradually, and the strain rate sensitivity of dynamic compressive strength of BFRESC with fiber content of 0.1% is the strongest. The specific energy absorption of concrete at early ages increases linearly with the strain rate. With the increase of curing age, the strain rate sensitivity of specific energy absorption of concrete increases gradually, and basalt fiber can enhance the strain rate sensitivity of specific energy absorption of concrete. Based on the comparison with the formula for dynamic increase factor (DIF) calculation provided by Comite Euro‐International du Beton (CEB), etc., a model of DIF based on the increase of curing age is proposed.

Research on the engineering performance of concrete containing waste liquid crystal glass and volcanic ash in a hot spring environment

The research aims to use industrial by-products such as slag, fly ash, and waste liquid crystal glass as concrete additives to reduce emissions and promote a circular economy. These efforts can contribute significantly to the development of a sustainable spa environment infrastructure. In the study, 40% and 60% high-content waste liquid crystal glass replaced the coarse aggregates, slag replaced part cement, fly ash replaced part of the sand, and according to specific ratios to make the concrete, then to evaluate the workability, hardening, and durability of concrete in hot spring water.The test results show that the workability of the concrete increases with the increase in substitution amount and that the slump increases from 61.1% to 66.7%. The concrete laying time increased by 7.56% but reduced the density by 9.79%. The compressive strength of concrete increases by 11.6%-13.41% and the velocity of the ultrasonic pulse is 4556–4717 m/s. Regarding durability, the chloride ion content is within the specified range between 0.014–0.031 kg/m3, and the surface resistance increases by about 9.95–10.93 times. In summary, we determined the optimal replacement amount that can effectively use the mixing ratio of waste liquid crystal glass, slag powder, and fly ash in concrete in the hot spring environment. This will improve waste reuse to cope with aggregate shortages increase the environmental pollution caused by cement manufacturing and achieve maximum environmental benefits.

Fresh and Hardened Properties of Brick Aggregate Concrete with Maximum Aggregate Sizes of 10 mm to 75 mm

The fresh and mechanical properties of concrete made with brick aggregates of eight different maximum aggregate sizes (MAS), i.e., 10 mm, 12.5 mm, 19 mm, 25 mm, 37.5 mm, 50 mm, 63 mm, and 75 mm, were investigated. The other parameters studied were sand-to-aggregate volume ratio (s/a) (0.40 and 0.45), W/C (0.45, 0.50, and 0.55), and cement content (375 kg/m3 and 400 kg/m3). In total, 80 different concrete mixes were studied; the perimeter of the interfacial transition zone (ITZ) along the brick aggregates was quantified with an image-analysis software and the microstructure along the ITZ was investigated using a scanning-electron microscope (SEM) to corroborate the hardened properties of the concrete. Although larger MAS leads to greater slump in concrete, its effect on hardened properties is linked to other design parameters. For a cement content of 375 kg/m3 and W/C of 0.45 and 0.50, the compressive strength of concrete increases (by up to 5%–15%) with increases in MAS of up to 37.5 mm irrespective of s/a (0.40 and 0.45) and then reduces gradually. For all other cases, the compressive strength of concrete is reduced with increases in MAS. The SEM imaging confirmed the presence of weak and porous ITZ and the deposition of ettringite in the voids left by entrapped bleed water under large aggregates. The compressive strength also increased with increases in s/a from 0.40 to 0.45, predominantly for smaller MAS. Correlations between mechanical properties of concrete and stress–strain curves are proposed for different MAS.

Strength Development of Seawater Mixed and Cured Concrete with Various Replacement Ratios of Fly Ash

In certain scenario, seawater maybe the only mixing and curing water available. Normally, concrete mixing requires freshwater, a resource which is expected to vastly deplete as a result of global water scarcity. Seawater which covers more than 70 percent of earth surface has potential to replace the freshwater in concrete. Hence, it is necessary to optimize conditions for its application in concrete, because freshwater reserves are either limited or its transport is costly. Further, the effect of various replacement ratios of fly ash needs further studies to determine applicability on concrete with seawater mixing in particular. Thus, this study aims to examine by which seawater can be employed as mixing water for making concrete, especially for plain concrete. The main objective of this study is to investigate the effect of seawater as mixing and fly ash as supplementary binder at 10%, 20% and 30% for Portland Composite Cement replacement on compressive strength, respectively. The water-to-binder ratio was varied at 40%, 50% and 60%. The specimens were cured (continuous immersion) in freshwater and seawater for 91-days. The results indicated that seawater can be used as mixing and curing water. Compressive strength of concrete increase when using seawater as mixing water and freshwater as curing water especially for w/b of 40%. Also, significant strength development up to 91-days was shown by fly ash concrete when using seawater as curing water and freshwater as mixing water . Effectiveness of seawater curing on strength development of fly ash concrete with w/b of 40% is larger in concrete with freshwater mixing than seawater mixing. The results obtained in this study provide an information in development for applicability seawater in concrete.

Assessment of Stone Ash as a Fine Aggregate Material to Meet the Value of Normal Concrete Compressive Strength

The concrete industry in Indonesia is very advanced and developing, so the use of construction materials is increasing. The need for other materials as a substitute for fine aggregate for the manufacture of concrete, namely stone ash comes from the stone slate industry waste. 20% stone ash, 80% sand) and (30% rock ash, 70% sand) with a concrete quality target of Fc' 17.5 Mpa. The method used is the laboratory experimental method referring to the SNI standard. The results showed that the use of stone ash (AB) as a normal concrete mixture affected the compressive strength of concrete. The higher the percentage of stone ash (AB), then the value of the compressive strength of concrete increases. The value of the compressive strength of concrete from stone ash (AB) at the composition of AB 10%, AB 20% and AB 30% was 173.50 kg/cm2, 235.11 kg/cm2 and 239.88 kg/cm2 while normal concrete was 18.59 MPa at 28 days.

Study on the Phosphogypsum Proportion in Foamed Concrete Based on Concrete Strength and Carbon Emission

The production of concrete will produce a lot of carbon dioxide and pollute the environment. Phosphogypsum is a solid waste generated during wet phosphoric acid treatment, and the use of phosphogypsum blending instead of cement in concrete production can effectively reduce carbon dioxide emissions. Then, experiments were conducted for six concrete groups with different phosphogypsum content as 0%~50% to test the strength in 3 days, 7 days, and 28 days. The results show that as the curing day rise, the compressive strength of concrete increases, meanwhile, with the increment of phosphogypsum content, the 28-day strength decreases significantly. The analysis for the consideration of the balance in carbon emission and the strength evolved, and results could be concluded that although the decrement of 28-day strength as well as the carbon dioxide emissions with the increasing phosphogypsum content in concrete, different trends were found. As the strength and emissions vary, a suggested range of content for phosphogypsum in concrete can be found. Based on these results, the proportion of phosphogypsum in concrete is proposed to achieve the purpose of energy saving and emission reduction and improve the utilization rate of phosphogypsum.

Influence of curing system on static and dynamic mechanical properties of fly ash concrete

This paper investigates the effect of curing conditions on the static mechanical properties of fly ash concrete such as compressive strength and stress–strain behavior, and utilizes the split Hopkinson pressure bar (SHPB) device to characterize the dynamic mechanical responses of steam-cured concrete under different strain rates. Experimental results reveal that the strength of static concrete decreases with the increase of fly ash (FA) content and increases first and then decreases with the increase of steam curing temperature. The substitution of fly ash for cement reduces water consumption, weakens the hydration degree of cement, and affects the development of static concrete strength. The steam curing temperature plays a role in promoting cement hydration within a certain range, but high temperature leads to the destruction of concrete microstructure, thus inhibiting the development of strength and leading to the instability of concrete performance. The steam curing temperature effects on the dynamic compressive strength of concrete is receded with the increase of strain rate. When the steam curing temperature is constant, the dynamic compressive strength of concrete increases gradually with the increase of strain rate, and the influence of strain rate on the dynamic compressive strength of concrete is greater than that of steam curing temperature. The analysis of the scanning electron microscope (SEM) confirmed that the decrease of concrete strength was due to the change of temperature and fly ash content, which increased microstructure pores, thus affecting the development of strength. This study has important guiding significance to improve the safety of engineering facilities and adapt to the development of modern engineering towards heavy load, long span, and harsh environment.

Application of consistency-based water-to-binder ratio to compensate workability loss in concrete modified with rice husk ash

Rice husk ash is a material that has the potential to replace cement partially. Many research works concluded that besides having some environmental advantages, the use of rice husk ash (RHA) also improves the hardened properties of concrete. This experimental study addresses the effect of the RHA on the basic properties of ordinary Portland cement by evaluating the standard consistency, initial setting time, and final setting time of RHA-added cement. This study also presents the fresh and hardened properties of concrete modified with RHA. The replacement of cement was done with five different percentages (0%, 5%, 10%, 15%, and 20%) of RHA. Samples were also segregated based on the two different methods of the selection of water to binder (w/b) ratio. In the first method w/b ratio was kept constant at 0.45 for all cement replacement percentages (RHA%). In the second method, the w/b ratio was selected based on the standard consistency of the modified cement. The findings of the experimental study show that standard consistency is increased with the increment in RHA%. A small increase in the initial setting time can be noticed with lower RHA% (5% and 10%), however, higher RHA% causes a decrease in the initial setting time. No significant change in the final setting time was found due to the addition of RHA. The workability of the concrete decreases significantly with respect to RHA% in the case of constant w/b ratio samples. But in consistency-based w/b ratio samples, RHA% has an insignificant effect on workability. The compressive strength of concrete increases with the increase in RHA% up to a 10% value for the constant w/b ratio samples. However, an insignificant change was noticed due to RHA% when the consistency-based w/b ratio had been applied. The study concludes that the strength of concrete can be improved by cement replacement with RHA with some sacrifice in terms of workability. But if we add extra water to compensate for the workability loss, we can replace cement with RHA without any significant strength loss.

ВПЛИВ КІЛЬКОСТІ ФІБРИ І СУПЕРПЛАСТИФІКАТОРУ НА МІЦНІСТЬ БЕТОНІВ ЖОРСТКИХ ДОРОЖНІХ ПОКРИТТІВ

According to the optimal plan, an experiment was conducted in which the following factors of the concrete composition of rigid pavements were varied: the amount of Portland cement (from 350 to 450 kg/m3), the amount of polypropylene fiber with a fiber length of 39 mm and an equivalent diameter of 0.45 mm (from 0 to 3 kg/m3), the amount of superplasticizer based on polycarboxylates (from 1 to 2%). All concrete mixtures had equal mobility S1. Equal mobility was achieved by selecting the amount of water in the composition with appropriate adjustment of the concrete composition. It was established that with an increase in the amount of Portland cement in the concrete composition, the W/C of mixtures of equal mobility decrease. By increasing the amount of superplasticizer from 1 to 2% of the weight of cement, the W/C of the mixture decreases by 10-12%. When polypropylene fiber is introduced in the amount of up to 1.5 kg/m3, the W/C of the mixture practically does not change. But when the amount of fiber is increased to 2.5-3 kg/m3, the W/C of the mixture significantly increases. The strength of concrete and fiber concrete was determined at the age of 3 and 28 days. It was established that at the age of 3 days, the compressive strength of the tested concretes is 63-69% of its strength at the design age. By increasing the amount of superplasticizer to 2%, the compressive strength increases by 4.5-6 MPa at the age of 3 days, and increases by 7-9 MPa at the age of 28 days. In the early and design age, when the amount of polypropylene fiber increases to 1.5-1.8 kg/m3, the compressive strength of concrete increases by an average of 3 MPa. A further increase in the amount of fiber already has a negative effect on the strength of concrete. At an early age, the influence of the amount of cement on the flexural strength of concrete is more noticeable than at the design age. Due to the increase in the amount of Portland cement from 350 to 450 kg/m3 at the age of 3 days, the flexural strength increases by an average of 1.4 MPa, and at the age of 28 days it increases by 0.5 MPa. Concretes with amount of superplasticizer 1.7-1.8% have the highest flexural strength. Thanks to the application of dispersed reinforcement, the tensile strength of the tested concretes increases by 0.3-0.5 MPa. When using a rational amount of additives and fiber, the flexural strength of the tested concretes is at least 6 MPa, which corresponds to the class Bbtb4.8. According to the requirements of DBN B.2.3-4:2015, such concrete can be used for rigid pavements of any category.

Mechanical properties of high strength concrete incorporating chopped basalt fibers: experimental and analytical study

Many civil engineering structures are constructed in terms of aspect like economy, strength and serviceability requirement. The fibres play a prominent role in bridging the micro cracks at the early stage of crack propagation and makes the structure ductile. The impact of chopped basalt fibre on high-strength reinforced concrete composites is the focus of this research. The chopped basalt fibre hardened property of concrete was investigated and compared it with controlled concrete. Moreover, physical property of concrete i.e. slump cone and compaction factor incorporating chopped basalt fibre volume fraction in variation of 0%,0.75%,1.5%,2.25%,3% to the total volume of concrete mix was also investigated. To analyse the hardened properties of chopped basalt fibre high strength concrete, 135 test samples were made and cured for 7, 14, and 28 days. The test findings show that increasing the volume percentage of fibres reduces slump from 135 mm to 132 mm for BFHS0.75 but does not result in a significant increase in concrete compressive strength of 77.1 MPa for BFHS0.75 However, on addition of chopped basalt fibres at 2.25% (BFHS2.25) the percentage increment of flexural strength increases by 72.8% (10.3 MPa) with control mix (5.96 MPa) and after that it decreases when 3% fibres were incorporated. Similarly, split-tensile strength increases at all fibre dosage and fibre addition of 3% (BFHS3) increases by 12.28% (5.65 MPa) with controlled concrete (5.04 MPa). The analytical results and suggested regression model could be used in real-world situations with fiber reinforced high strength concrete related issues. There is a significant relationship between mechanical property and independent variable through ANOVA in SPSS.

EXPLORING CRUSHED CONCRETE WASTE AS RECYCLED FINE AGGREGATE IN CONCRETE PRODUCTION

Concrete waste is generally a challenge that is left to accumulate in illegal dumping areas and landfills. This research focused on how structural concrete waste could be crushed and used as recycled fine aggregate in the production of concrete. Experiments were carried out to establish the performance of this 0.6 water-cement ratio concrete containing partially recycled fine aggregate. Concrete fluidity and compressive strength tests were carried out at 7 days and 28 days only because the study was exploratory in nature. Results indicated that replacement of 20% natural fine aggregate with recycled fine aggregate resulted in the increase of concrete compressive strength by 8% from 28 MPa to 30 MPa at 28 days. 40% replacement of natural fine aggregate resulted in a drop of compressive strength by 11% yet retaining compressive strength at 25 MPa. 20% and 40% replacement of natural aggregate resulted in the concrete fluidity reduction of 5% and 17%, respectively. The average theoretical density was 2538 kg/m3. The study concluded that normal grade structural concrete can be attained using crushed concrete waste resulting in taking out the concrete waste from landfills and illegal dumping sites. These results established an environmentally friendly mode of handling concrete waste sustainably. Further, this solution would result in slowing down the depletion of natural fine aggregate bodies.

Early-age concrete strength monitoring using smart aggregate based on electromechanical impedance and machine learning

It is crucial to monitor the real-time strength development of early-age concrete, which is related to the structure safety and construction efficiency of concrete. This paper proposed a new method to predict and monitor concrete strength development. The basic idea is using embedded smart aggregates (SAs), combining the electromechanical impedance (EMI) technology and machine learning to monitor the strength development of early-age concrete. An EMI model of the embedded SA was firstly established and the relationship between the conductance resonant frequency (CRF) and conductance resonant peak (CRP) of the SA and the development of concrete strength was investigated. The conductance signatures were continuously monitored and the compressive strength of the specimens at different ages was tested. Hence, the EMI model results that the CRF decreases but CRP increases as the compressive strength of concrete increases were verified by analyzing the collected data. The four different models of a linear regression model (LR), a convolutional neural network (CNN), a hybrid (LR-CNN) model, and an empirical equation were established. The conductance of SAs as the developed models inputs, the compressive strength of specimens as outputs. Finally, these four models were compared with each other. Meanwhile, the performance indicators of the LR-CNN model and other hybrid models were compared. The results show that the LR-CNN model has excellent performance and successfully achieves quantitative prediction of concrete strength development. The proposed method for evaluating and predicting the compressive strength of concrete is simple, accurate, quantitative and reliable, and has promising application.

Analisis Pengaruh Pencampuran Serat Karbon Terhadap Kekuatan Beton dalam Menahan Beban Desak, Beban Tarik dan Beban Lentur

This study aims to overcome the weaknesses of concrete, namely the nature of concrete which is classified as brittle so that it has a negative impact on the concrete in resisting bending and splitting, while it also has a high density (2.3-2.4 T / m3). So that this research will add fiber to concrete in the form of carbon fiber, carbon fiber that is very strong and is known to be very light is expected to increase the tensile strength and flexural concrete significantly and without adding weight to itself. Calculation of concrete mix planning using normal concrete mixture calculations (SNI 03-2834-2000) with a planned compressive strength is 20 MPa, carbon fiber mixed in the form of fiber pieces with variations in fiber length, namely 5mm, 10mm and 15mm with a composition of 0.4% of normal concrete weight. Tests are carried out when the concrete sample is 28 days old. While waiting for the concrete age to reach 28 days, the concrete is treated in the form of soaking in water. And the results of this study indicate a significant increase in concrete compressive strength of 45.32%; concrete tensile strength of 73.24%; and the flexural strength of the concrete was 78.83% but it also managed to maintain the density of concrete at 2.3 T / m3. For further discussion and more detail will be presented in the following research report.

Analytical investigations of concrete beams reinforced with FRP bars under static loads

Fiber Reinforced Polymer (FRP) bars have appeared as a preferable alternative to ordinary steel bars in reinforced concrete (RC) members due to their higher ultimate tensile strength-to-weight ratio and corrosion resistance. The previous studies have mainly focused on laboratory tests and finite element modeling approaches for FRP-RC beams; however, only limited analytical studies have been conducted. Therefore, this study was designed to present analytical investigations of full-scale concrete beams longitudinally reinforced with Glass-Fiber Reinforced Polymer (GFRP) bars. The Strips Analysis Method (S-A-M) was used to implement the analytical investigations using stress–strain models for concrete and reinforcement. The beams, having the cross-sectional dimensions of 150 mm width × 200 mm height, were statically analyzed under different-point bending. The analytical results were verified with the results of experimentally tested GFRP-RC beams, and the outcomes showed excellent agreements. Also, the analytical method used in this study exhibited much efficiency and reliability compared with the traditional procedures used for the analysis of ordinary reinforced concrete members. A parametric study was, in addition, conducted to investigate the effects of concrete compressive strength, different-point bending, and scale of beams on the performance of GFRP-RC beams. It was found that the structural efficiency of GFRP-RC beams can be enhanced with the increase in concrete compressive strength and significantly influenced by the scale size of beams.

Numerical verification for concrete beams reinforced with CFRP subjected to pure torsion

Torsional behavior of concrete beams reinforced with longitudinal Fiber reinforced polymers (FRP) bars and FRP transverse stirrups has not been well-defined in various international codes and design guidelines as evidenced from the discrepancies in design equations. Such discrepancies are due to the complex behavior of beams subjected to torsional stresses and the limited research available in the literature; especially for FRP reinforced beams. A non-linear finite element (FE) analysis is conducted using ATENA software to generate a numerical model to predict and verify the failure loads and strains of beams of a compiled database from literature. This paper presents a comparison between the results of the experimental data and analytical models in order to verify the efficiency of the proposed numerical model for predicting failure load/strains in longitudinal FRP bars, FRP stirrups, and rotation angle of the tested beams. The comparison showed good agreement between experimental and analytical models in ultimate torque with difference of 6.5 % and the model is used in a parametric study to investigate the effect of concrete compressive strength, longitudinal reinforcement ratio, and beam depth under pure torsion in addition to the effect of concrete contribution to the torsional resistance. The numerically computed cracking and ultimate torques are compared with results from theory of elasticity, skew-bending theory and code equations such as: ACI-318 and CSA-S806-12. Based on this study, CSA-S806 gives acceptable prediction of ultimate torque, while ACI code is found to be more conservative. The increase of concrete compressive strength can enhance the cracking and ultimate torque. The increase of longitudinal reinforcement ratio has an insignificant effect on ultimate torque but increases the twist capacity of Reinforced concrete (RC) beams. The increase of longitudinal reinforcement can improve also the twist ductility.

Nonlinear 3D Finite Element Model for Square Composite Columns Under Various Parameters

Composite columns are frequently used in constructing high-rise structures because they can minimize the size of the building's columns while increasing the floor plan's usable space. This study aims to create a nonlinear 3D finite element model for square composite columns designed for solid and hollow columns with various multi-skin tubes subjected to loads at eccentricities of (30 and 60) mm, compressive strength, and mesh size using the ABAQUS software. The comparison was based on the experimental data of six references of composite columns. While the compressive strength of concrete increases, the stiffness of the composite column rise. The ratio of concrete compressive strength values for composite column increased by (0, 12.3, 17.8, and 26.7 percent) for (fc'=25, 31.96, 35, and 40) MPa, respectively. The results of the different mesh sizes (20, 40, and 60) mm are showing; The experimental results and the finite element solution developed using the (20 X20) mm element correspond well. The nonlinear finite element analysis method was used, and the finite element outputs results were confirmed to be in favorable agreement with the experimental data

Study of the structural-functional lightweight concrete containing novel hollow ceramsite compounded with paraffin

In this paper, a structural-functional lightweight aggregate concrete (LWAC) with novel hollow ceramsite (HC) compounded with paraffine was prepared and studied. The mechanical and thermal properties of LWAC with HC-Paraffin are investigated and multiple thermal cycles are tested to evaluate the stability of this novel energy storage concrete. Results show that, the energy storage density (Des) of HC-paraffin is 85.23 J/g in the temperature range 15 °C–45 °C and the latent heat of HC-paraffin is 51.09 J/g. Compressive strength of LWAC with HC-Paraffin is 41.9 MPa which fully meets the requirements of structural building application. The amount of paraffin (8.1 wt%) introduced by HC is relatively advantageous in the current energy storage concrete researches. Compare to control group, the peak temperature and temperature fluctuation of LWAC panel with HC-Paraffin reduce about 5.2 °C and 7.6 °C respectively during the thermal test. Morever, the LWAC with HC-Paraffin shows good stability of mechanical and thermal property. The compressive strength of concrete increases about 8.6 % and the thermal regulation ability of concrete panel has no obvious degradation after 100 thermal cycles. This research gives a new method for the shape stable PCMs which can be directly used in building envelope, providing an alternative for the application of PCMs in buildings.