Lightweight Aggregate Concrete Slabs Research Articles

Investigation on the response of steel fiber reinforced lightweight aggregate concrete slab under sequential impact loading

The current study investigates the response of steel fiber-reinforced lightweight concrete slabs under sequential impact loading. The potential damages caused by impact loads which are a threat to many structures and the use of fiber to mitigate them was evaluated experimentally. Moreover, a comprehensive parametric study was conducted using the finite element method to evaluate the effect of influential factors such as fiber content, slab geometry, and energy of impact. The results show that impact loads can cause significant damage to lightweight aggregate concrete slabs, including cracking and spalling. The use of steel fibers in lightweight aggregate concrete can improve its stiffness, energy absorption, overall stability, and prevent crack propagation resulting in the reduction of the damage risk under impact loads, compared to specimen without fiber. The incorporation of fibers resulted in a significant rise in the number of impacts required for failure. In contrast to the control slab, which failed completely after three impacts, lightweight concrete slabs containing steel fibers at volume fraction of 0.5%, 1%, and 1.5% endured 87, 710, and 1213 impacts before failure, respectively. In addition, adding steel fibers causes a more consistent response in terms of stiffness as the frequencies of lightweight concrete slabs containing steel fibers at volume fraction of 0.5%, 1%, and 1.5% remained unchanged until 34%, 17%, and 40% of the total number of impacts resulting in failure. Moreover, the utilization of fibers preserves structural integrity and localizes crack formation. Overall, the current study provides valuable insights into the response of light weight aggregate concrete structures under impact loading and the potential benefits of using steel fiber and lightweight aggregate in concrete.

Application of the Critical Shear Crack Theory for calculation of the punching shear capacity of lightweight aggregate concrete slabs

Application of the Critical Shear Crack Theory for calculation of the punching shear capacity of lightweight aggregate concrete slabs

The Temperature and Pore Pressure Distribution of Lightweight Aggregate Concrete Slabs Exposed to Elevated Temperatures

Concrete has good fire resistance. However, once exposed to rapidly increasing temperatures, concrete may suffer from thermal stress-induced spalling or pore pressure-induced spalling. Compared with normal-weight concrete (NWC), lightweight aggregate concrete (LWAC) has a low thermal conductivity and is more prone to cause a higher temperature gradient under the action of high temperatures. This poses a hidden concern to the fire safety of general LWAC structures. Therefore, this study aimed to investigate the temperature and the pore pressure distribution of LWAC slabs under one-dimensional heating tests and to compare them with NWC slabs. The test variables were the moisture content of the specimen (oven-dried and air-dried), target temperature (600 and 800 °C), and heating rate (5 and 10 °C/min). The temperature and the pore pressure distributions were measured separately by thermocouples and pressure gauges embedded in different positions of the specimen. The test results show that the maximum pore pressure (Pmax) of the LWAC slabs was generally higher than that of the NWC slab at a distance of 10 mm from the heated surface when the specimen was in an oven-dried state. However, at 30 and 50 mm from the heated surface, the Pmax of the NWC slab tended to be higher. This shows that the Pmax distribution of the LWAC slab was closer to the heated surface when the specimen was in an oven-dried state, while the Pmax of the NWC slab occurred further from the heated surface. Further, as the heating rate increased, a higher pore pressure was generated inside the specimen and the pressure rose more rapidly. In particular, at a target temperature of 800 °C and a heating rate of 10 °C/min, the corner spalling phenomenon appeared on the air-dried LWAC slab.

UHPFRC hidden capitals as an alternative method for increasing punching shear resistance of LWAC flat slabs

Due to outstanding strength properties of contemporary ultra-high performance fiber reinforced concretes (UHPFRC), they can be successfully used to improve the punching shear resistance of flat slabs made from lightweight aggregate concrete (LWAC). However, the relatively high cost of UHPFRC means that the application is usually limited to the support zone or the subsurface layer of the slab.The paper presents the results of experimental investigations on application of the UHPFRC hidden capitals to increase punching shear capacity of LWAC slabs. The study was a continuation of the previous experimental program and included a total of three 200 mm thick slabs with the same longitudinal reinforcement ratio, equal to 1.23%. One was the control specimen made entirely from LWAC, while in the others 130 mm thick capitals from UHPFRC with 2.5% and 5.0% fiber content were cast. The application of hidden capitals allowed to increase the stiffness and reduce deflections of the slabs by about 16 ÷ 20%. The residual strength of UHPFRC was found to be the key feature. In case of the slab with capital from UHPFRC with 2.5% fibre content, shear crack formed at the edge of the column and crossed the capital. However, the contribution of UHPFRC strength allowed to increase the punching shear capacity by 29% with respect to the control specimen. The doubling of fiber content to 5.0% changed the failure mechanism, because the shear cracks formed at the edge of the capital, what was similar to observed in slabs failed outside punching shear reinforced area. This translated into a significant increase in the load capacity by 82% in comparison to the control slab.The performed analysis demonstrated the usefulness of the Critical Shear Crack Theory (CSCT) and the Variable Engagement Model (VEM) for the assessment of the punching shear resistance of LWAC slabs with hidden capitals from UHPFRC. A good agreement of load-rotation response and ratios of theoretical to experimental load equal to 0.87 and 1.16 were obtained. The calculations allowed for correct prediction of the failure mode – punching within or outside the capital.

Load deflection behaviour and properties of sustainable lightweight aggregate concrete slabs

This research has been conducted to investigate the effect of partial replacement of coarse aggregate by lightweight aggregate on different characteristics and load deflection behaviour of concrete. Natural aggregate was replaced once by waste walnut shell and then by porcelinate aggregate. And both types are considered lightweight aggregate. Percentages of replacement by volumetric rates ranging between 25% to 100% were adopted. In addition, cement was replaced by 10% waste glass powder. Compressive strength, splitting tensile strength, and dry density were made. Also, one-way slab was cast for 50% replacement and tested under four point flexural test. Results showed that replacement of natural aggregate with lightweight aggregate regardless of its source decrease density, compressive strength and splitting strength. While an increase in the deflection at failure was noticed for slabs incorporating lightweight aggregate compared to the reference one. Concrete containing 50% porcelinate demonstrated a slight increase in strength compared with the reference slab by 8.91% concrete containing 50% WA demonstrated a clear reduction in strength compared with the reference slab by 62.57%. The width of crack at failure for concrete incorporating walnut coarse aggregate was wider for the reference one. While concrete incorporating porcelinate failed with finer cracks than the reference one.

Load deflection behaviour and properties of sustainable lightweight aggregate concrete slabs

Load deflection behaviour and properties of sustainable lightweight aggregate concrete slabs

Finite Element Analysis on Core-Assembled Lightweight Aggregate Concrete Slab

In this paper, the structural form of the core-assembled lightweight aggregate concrete slab has been changed, and the non-linear finite element analysis is carried out using ABAQUS software, which is compared with the experimental value. The damage model of ABAQUS found that the cracks in the simulation process are almost the same as the cracks in the test. The ABAQUS software is suitable for the flexural performance test of the core-assembled lightweight aggregate concrete slab. Finite element analysis provides a certain reference.

Punching shear behaviour of solid and bubble reinforced light Weight aggregate concrete two-way slabs

Punching shear is the most important problem in flat slabs, which usually required reducing the self-weight of the slab. A lightweight concrete as well as the bubble deck technology were used to allow for lighter self-weight of the structure. This study aims to investigate the use of lightweight aggregate concrete (LWAC) with the bubble deck technology in flat slab. The behavior of two- way LWAC voided slab (with and without shear reinforcement) under punching shear effect with respect to solid normal weight and solid LWAC specimen were studded. The behavior of six specimens having the same dimensions, slab thickness and flexural steel reinforcement were studded. The main changed variables were concrete type, percent of void and punching shear reinforcement existence. The results show that the load carrying capacity for light weight aggregate concrete voided slab without shear reinforcement decreased by (60%, 53%) with respect to solid normal weight and solid LWAC slabs without shear reinforcement respectively. In addition, the load carrying capacity for LWAC voided slab with shear reinforcement decrease by (67%, 47%) with respect to solid normal weight, solid LWAC slabs with shear reinforcement respectively. Also, for lightweight aggregate concrete, solid and voided slab, shear reinforcement existence did not significantly increase the slab capacity for punching shear. But cause a reduction in maximum deflection with respect to slabs without shear reinforcement.

Experimental investigations on punching shear of lightweight aggregate concrete flat slabs

Lightweight aggregate concrete due to the relatively low bulk density is used for casting the flat slabs of multi-story buildings. However, a significant concentration of internal forces within support zones result in the need for placing an additional punching shear reinforcement. Despite the fact that double-headed studs are the most popular type of transverse reinforcement, the European technical approvals (ETA) do not apply for using that in flat slabs made of lightweight aggregate concrete.In order to verify the efficiency of shear reinforcement in the form of double-headed studs in the lightweight aggregate concrete slabs in the Research Laboratory of the Department of Concrete Structures (KBB) experimental investigations were carried out. The tests included a total of 9 elements of 2400 × 2400 mm dimensions in a plane and the thickness of 200 mm. The variable parameters were the longitudinal reinforcement ratio and the cross-section of punching shear reinforcement. Very high efficiency of double headed-studs has been found. Their application allowed for increase in the load carrying capacity reaching from 16 to 73% (depending on the reinforcement ratio) with respect to the specimens without transverse reinforcement.

ANSYS Analysis of Prefabricated Light Aggregate Concrete Slab with Grouting

In this paper, through the relevant references of grouted concrete slabs, combined with the comparative analysis of lightweight aggregate concrete, a kind of “grouted assembled lightweight aggregate concrete slabs” is proposed. And design the size and reinforcement of prefabricated slabs. The mix ratio of lightweight aggregate concrete is calculated. The normal section bearing capacity of lightweight aggregate concrete slabs is calculated by theoretical formula. Combining with ANSYS software, get the analysis and comparison. According to the construction technology, four key quality control points and flow chart are put forward., which provides a deep reference for the construction of the assembled lightweight aggregate concrete slab with core filling in the future.

Investigation on mechanical performance of flat steel plate-lightweight aggregate concrete hollow composite slab

An innovated type of the flat steel plate-lightweight aggregate concrete hollow composite slab was presented in this paper. This kind of the slab is composed of flat steel plate and the lightweight aggregate concrete slab, which were interfaced with a set of perfobond shear connectors (PBL shear connectors) with circular hollow structural sections (CHSS) and the shear stud connectors. Five specimens were tested under static monotonic loading. In the test, the influence of shear span/height ratios and arrangements of CHSS on bending capacity and flexural rigidity of the composite slabs were investigated. Based on the test results, the crack patterns, failure modes, the bending moment-curvature curves as well as the strains of the flat steel plate and the concrete were focused and analyzed. The test results showed that the flat steel plate was fully connected to the lightweight aggregate concrete slab and no obvious slippage was observed between the steel plate and the concrete, and the composite slabs performed well in terms of bending capacity, flexural rigidity and ductility. It was further shown that all of the specimens failed in bending failure mode regardless of the shear span/height ratios and the arrangement of CHSS. Moreover, the plane-section assumption was proved to be valid, and the calculated formulas for predicting the bending capacity and the flexural rigidity of the composite slabs were proposed on the basis of the experimental results.

Experimental Investigations on Punching Shear of Flat Slabs Made from Lightweight Aggregate Concrete

Abstract In the paper the results of experimental investigations concerning flat slabs made from reinforced lightweight concrete with sintered fly ash aggregate CERTYD were presented. In the research program 6 models made in a natural scale were included. The main variable parameter was slab longitudinal reinforcement ratio. The aim of investigation was the experimental verification of efficiency of double-headed studs as punching shear reinforcement. In the existing technical approvals such kind of reinforcement was allowed only in normal concrete slabs. It was demonstrated that double-headed studs can be an effective transverse reinforcement of lightweight aggregate concrete slabs. The use of double-headed studs resulted in increase in the ultimate load from 19% to 44%, depending on the slab reinforcement ratio which ranged from 0.5% to 1.2%. The comparative analysis showed that the Eurocode 2 provisions were conservative in relation to the experimental results, which were on average 42% higher than the theoretical ones however with a very low 7% coefficient of variation.

경량골재 콘크리트 바닥판의 펀칭전단강도의 실험적 평가

This paper investigates the punching shear strength of lightweight aggregate concrete (LWAC) slabs through a series of experimental study. Five full scale slabs were constructed using normal concrete and four different types of LWAC. Each lightweight aggregate (LWA) used in this study had different sources (clay, shale, or slate) and shapes (crushed or spherical shape). Based on the test results, the effect of the lightweight aggregates (LWA) on the punching shear behavior was investigated. From the test results, it was found that the punching shear failure surface of LWAC slab with spherical shape coarse aggregate was less inclined than that with crushed shape coarse aggregate, which resulted in an increase of the area of the shear failure surface. As a result, it leads to the increased punching shear strength of the slab. On the other hand, the failure surfaces of LWAC slab with crushed shape coarse aggregate and normal coarse aggregate were inclined similarly. Finally, the test results of this study were compared with the punching shear strength obtained from current design models, such as ACI and CEB-FIP, to examine the validation of current design model to predict the punching shear strength of the LWAC slab.

Punching shear failure of slab with lightweight aggregate concrete (LWAC) and low reinforcement ratio

This paper presented the punching shear resisting capacity of lightweight aggregate concrete (LWAC) slabs having low reinforcement ratio. Five full scale slabs were constructed using normal concrete and four different types of LWAC. The experimental study was then performed to study the effect of LWAC on the punching shear resisting capacity of slabs. The nonlinear finite element analysis was also conducted for each slab specimen to analyze the failure mechanism of LWAC slabs with low reinforcement ratio, by demonstrating the cracks formation and propagation. Finally, from the test results of this study and previous researches, a simple design equation to predict the punching shear resisting capacity of LWAC slabs was proposed considering the reinforcement ratio of the slab. The proposed equations provided good prediction of the punching shear resisting capacity of LWAC slabs with different reinforcement ratios.

Behavior of High-Strength Lightweight Aggregate Concrete Slabs under Column Load and Unbalanced Moment

Behavior of High-Strength Lightweight Aggregate Concrete Slabs under Column Load and Unbalanced Moment

Punching shear resistance of lightweight aggregate concrete slabs

Provisions for the use of structural lightweight aggregate concrete are included in British codes of practice, but limitations are applied as to the design values that may be used. This Paper is concerned with the strength in shear of slabs subjected to punching, which is limited in the codes to 80% of that for normal-weight concrete of the same compressive strength. Tests on slabs made with five different lightweight aggregates are described; on the basis of the results it is concluded that the code provisions are unnecessarily conservative.

On the Flexural Strength of Structural Lightweight Aggregate Concrete Slabs

The object of this study is to examine the strength and deformation characteristics of reinforced concrete slabs made of structural lightweight aggregate (Lionite sand and gravel-pelletized type), in order to ascertain the adequate safety of the composite slab structures to which the material is applied. Twelve slab specimens having 3/5 scale to standard design dimensions, and sixteen beam specimens were tested under static load to failure with various support and loading conditions. Normal concrete specimens were also tested for the purpose of comparing the characteristics of lightweight ones. This limited investigation indicates that the Lionite concrete has almost the same strength properties as normal one and may be used with sufficient safety. As to the deformation, lionite concrete specimens showed a little larger deflection than normal concrete. However, the discrepancy of their deflection was much smaller than that of modulus of elasticity. Two-span continuous slab specimens were considered to have failed in punching shear, though the corresponding simple slab specimens were in bending moment. This indicates that the carrying capacity of slab structures should be examined for punching shear rather than for bending moment when the degree of restrainment becomes higher.

Sheer Strength of Reinforced Structural Lightweight Aggregate Concrete Slabs

Sheer Strength of Reinforced Structural Lightweight Aggregate Concrete Slabs