scholarly journals Nonlinear analysis of lightweight aggregate concrete columns

2020 ◽  
Vol 19 (3) ◽  
pp. 081-091
Author(s):  
Ewelina Kołodziejczyk ◽  
Tomasz Waśniewski
Keyword(s):  
Axial Force ◽  
Bending Moment ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Ultimate Strain ◽  
Nonlinear Material ◽  
Lightweight Aggregate Concrete ◽  
Peak Strain ◽  
Cross Sectional ◽  
Aggregate Concrete

The paper presents a numerical analysis of deformability and load-bearing capacity of lightweight aggregate concrete (LWAC) elements subjected to bending with axial force. The nonlinear material model of LWAC presented in Eurocode 2 (EC2) was assumed. Several different densities and compressive strengths of concrete were taken into account. The investigations included the comparison of the sectional capacity and the behaviour of slender elements made with normal and lightweight aggregate concrete. It was observed that density-dependent mechanical properties of concrete affect the obtained values of the maximum axial force and the bending moment despite the same mean compressive strength. In every case, the capacity of the RLWAC section was lower than the one of normal weight, which was caused by a linear characteristic of the LWAC. Other important factors were the modulus of elasticity and the ultimate strain of concrete. LWAC with the higher density and the lower ultimate strain gave greater stiffness to slender columns but reduced the cross-sectional capacity. It was concluded that the elastic modulus and the peak strain of LWAC which are applied in columns calculations should be verified experimentally.

Permeability of Lightweight Aggregate Concrete with Mineral Admixture

2013 ◽  
Vol 857 ◽  
pp. 105-109
Author(s):  
Xiu Hua Zheng ◽  
Shu Jie Song ◽  
Yong Quan Zhang
Keyword(s):  
Pore Structure ◽  
Lightweight Concrete ◽  
Chloride Ion ◽  
Lightweight Aggregate ◽  
Total Porosity ◽  
Normal Weight ◽  
Mineral Admixture ◽  
Mineral Admixtures ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Concrete

This paper presents an experimental study on the permeability and the pore structure of lightweight concrete with fly ash, zeolite powder, or silica fume, in comparison to that of normal weight aggregate concrete. The results showed that the mineral admixtures can improve the anti-permeability performance of lightweight aggregate concrete, and mixed with compound mineral admixtures further more. The resistance to chloride-ion permeability of light weight concrete was higher than that of At the same strength grade, the anti-permeability performance of lightweight aggregate concrete is better than that of normal weight aggregate concrete. The anti-permeability performance of LC40 was similar to that of C60. Mineral admixtures can obviously improve the pore structure of lightweight aggregate concrete, the total porosity reduced while the pore size decreased.

Influence of Lightweight Aggregate on Durability of High Performance Concrete

2009 ◽  
Vol 405-406 ◽  
pp. 197-203
Author(s):  
Bao Sheng Zhang ◽  
Li Juan Kong ◽  
Yong Ge
Keyword(s):  
Pore Structure ◽  
Cement Paste ◽  
Frost Resistance ◽  
High Performance ◽  
High Performance Concrete ◽  
Bound Water ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Concrete

High performance concrete (HPC) with a water/cement ratio (w/c) of 0.32 and different lightweight aggregate (LWA) contents (0%, 25%, 50%, 75%, 100%) were prepared, and the influence of LWA on concrete frost-resistance and impermeability at different ages were studied, as well as the hydration degree, hydrated product, pattern and pore structure of the paste around aggregate. The results show that, by replacing normal weight aggregate (NWA) with 50% and 100% volume contents of pre-wetted LWA respectively, the chemical bound water of the cement paste surrounding aggregate are increased 12.1% and 22.7% as compared to concrete mixed without LWA. And at 28 days, lightweight aggregate concrete has the highest Ca(OH)2 content, whereas the 90-day Ca(OH)2 content of normal weight concrete is the highest. This proves that, with the increase of LWA content in concrete, both of the internal curing effect of pre-wetted LWA and secondary hydration effect of fly ash (FA) are strengthened, this can also be verified by the SEM study. Furthermore, the pore structure of the cement paste around aggregate can be improved consequently. The performance of frost-resistance of HPC can be improved by mixing LWA, the 90 day-frost-resistance of lightweight aggregate concrete is about 2.5 times of that of concrete mixed without LWA. The influence of LWA on the impermeability of HPC is different from normal concrete. When LWA content is more than 50%, the HPC impermeability decreased obviously, however at later age the difference between them becomes minor.

scholarly journals Influence of Aggregate Gradation on the Engineering Properties of Lightweight Aggregate Concrete

2018 ◽  
Vol 8 (8) ◽  
pp. 1324 ◽  
Author(s):  
How-Ji Chen ◽  
Chung-Hao Wu
Keyword(s):  
Compressive Strength ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Engineering Properties ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Gradation ◽  
Aggregate Concrete ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Expanded Shale

Expanded shale lightweight aggregates, as the coarse aggregates, were used to produce lightweight aggregate concrete (LWAC) in this research. At the fixed water-cement ratio, paste quantity, and aggregate volume, the effects of various aggregate gradations on the engineering properties of LWAC were investigated. Comparisons to normal-weight concrete (NWC) made under the same conditions were carried out. From the experimental results, using normal weight aggregates that follow the specification requirements (standard gradation) obtained similar NWC compressive strength to that using uniform-sized aggregates. However, the compressive strength of LWAC made using small uniform-sized aggregates was superior to that made from standard-grade aggregates. This is especially conspicuous under the low water-cement ratio. Even though the workability was affected, this problem could be overcome with developed chemical additive technology. The durability properties of concrete were approximately equal. Therefore, it is suggested that the aggregate gradation requirement of LWAC should be distinct from that of NWC. In high strength LWAC proportioning, following the standard gradation suggested by American Society for Testing and Materials (ASTM) is optional.

scholarly journals Size Effect in Compressive Strength Tests of Cored Specimens of Lightweight Aggregate Concrete

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1187 ◽  
Author(s):  
Lucyna Domagała
Keyword(s):  
Compressive Strength ◽  
Scale Effect ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Cement Matrix ◽  
Lightweight Aggregate Concrete ◽  
Core Diameter ◽  
Aggregate Concrete ◽  
Normal Weight Concrete ◽  
Strength Tests

The aim of this paper is to discuss the unrecognized problem of the scale effect in compressive strength tests determined for cored specimens of lightweight aggregate concrete (LWAC) against the background of available data on the effect for normal-weight concrete (NWAC). The scale effect was analyzed taking into consideration the influence of slenderness (λ = 1.0, 1.5, 2.0) and diameter (d = 80, 100, 125, and 150 mm) of cored specimens, as well as the type of lightweight aggregate (expanded clay and sintered fly ash) and the type of cement matrix (w/c = 0.55 and 0.37). The analysis of the results for four lightweight aggregate concretes revealed no scale effect in compressive strength tests determined on cored specimens. Neither the slenderness, nor the core diameter seemed to affect the strength results. This fact should be explained by the considerably better structural homogeneity of the tested lightweight concretes in comparison to normal-weight ones. Nevertheless, there were clear differences between the results obtained on molded and cored specimens of the same shape and size.

Pre-Failure Deflection and Residual Load Capacity of Reinforced Lightweight Aggregate Concrete Beams under High-Cycle Fatigue

2010 ◽  
Vol 146-147 ◽  
pp. 926-936 ◽  
Author(s):  
How Ji Chen ◽  
Te Hung Liu ◽  
Chao Wei Tang
Keyword(s):  
Fatigue Testing ◽  
Load Capacity ◽  
Fatigue Behavior ◽  
Lightweight Aggregate ◽  
Fatigue Loading ◽  
Normal Weight ◽  
Lightweight Aggregate Concrete ◽  
Rc Beams ◽  
Aggregate Concrete ◽  
Normal Weight Concrete

The present study experimentally investigated the pre-failure and post-fatigue behavior of reinforced concrete (RC) beams constructed with lightweight aggregate concrete (LWAC) in comparison with that constructed of normal weight concrete (NWC) of the same compressive strength (40 MPa). A total of twelve RC beams were tested under different fatigue loadings. Based on the experimental observations, the midspan total deflection measured in the fatigue testing consisted of the elastic and plastic components. The mechanismof the two deflection components developed with load cycles was different. The experimental results showed that the fatigue resistance of LWAC beams was better than that of NWC beams for the same fatigue loading levels. It was reflected in both the lower evolution of fatigue damage and the smaller growth of midspan residual deflection. After 2 million cycles, an average increase in residual load capacity of about 8% was found in the NWC beams, while that in the LWA beams remained virtually unchanged.

scholarly journals A New Composite Slab Using Crushed Waste Tires as Fine Aggregate in Self-Compacting Lightweight Aggregate Concrete

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2551 ◽  
Author(s):  
Jing Lv ◽  
Tianhua Zhou ◽  
Hanheng Wu ◽  
Liurui Sang ◽  
Zuoqian He ◽  
...  
Keyword(s):  
Ultimate Load ◽  
Bending Moment ◽  
Lightweight Aggregate ◽  
Lightweight Aggregate Concrete ◽  
Flexural Properties ◽  
Aggregate Concrete ◽  
Composite Slab ◽  
Yield Load ◽  
Composite Slabs ◽  
Rubber Particles

A composite slab comprised of self-compacting rubber lightweight aggregate concrete (SCRLC) and profiled steel sheeting is a new type of structural element with a series of superior properties. This paper presents an experimental research and finite element analysis (FEA) of the flexural behavior of composite slabs consisting of SCRLC to develop a new floor system. Four composite slabs specimens with different shear spans (450 mm and 800 mm) and SCRLC (0% and 30% in rubber particles substitution ratio) are prepared, and the flexural properties including failure modes, deflection at mid-span, profiled steel sheeting, and concrete surface stain at mid-span and end slippage are investigated by four-point bending tests. The experimental results indicate that applying SCRLC30 in composites slabs will improve the anti-cracking ability under the loading of composite slabs compared with composite slabs consisting of self-compacting lightweight aggregate concrete (SCLC). FEM on the flexural properties of SCRLC composites slabs show that the yield load, ultimate load, and deflection corresponding to the yield load and the ultimate load of composite slabs drop as the rubber particles content increases in SCRLC. The variation of SCRLC strength has less impact on the flexural bearing capacity of corresponding composite slabs. Based on the traditional calculated method of the ultimate bending moment of normal concrete (NC) composite slabs, a modified calculated method for the ultimate bending moment of SCRLC composite slabs is proposed.

Fire Performance and Thermal Insulation of Reinforced Lightweight Aggregate Concrete

2011 ◽  
Vol 287-290 ◽  
pp. 1065-1069 ◽  
Author(s):  
Hsien Sheng Peng ◽  
How Ji Chen ◽  
Chao Wei Tang ◽  
Yu Ping Chen
Keyword(s):  
Thermal Conductivity ◽  
Coefficient Of Thermal Expansion ◽  
Fire Behavior ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Superior Performance ◽  
Resistance Testing ◽  
Lightweight Aggregate Concrete ◽  
Equivalent Thickness ◽  
Aggregate Concrete

Structural lightweight aggregate concrete (LWAC) members have demonstrated greater fire endurance periods than equivalent thickness members made with normal-weight aggregates. Superior performance is due to a combination of lower thermal conductivity, lower coefficient of thermal expansion, and the inherent thermal stability developed by aggregates that have been exposed temperature greater than 1050°C during preprocessing. Furthermore, LWAC exhibits relatively high thermal insulating value, of which the thermal conductivity can be half as much as that of ordinary normal-weight concrete (NWC). Therefore, the main objective of this paper is to implement fire resistance testing for structural and non-structural elements made of LWAC and NWC to assess and compare their fire behavior.

Structural Lightweight Aggregate Concrete by Incorporating Solid Wastes as Coarse Lightweight Aggregate

2015 ◽  
Vol 749 ◽  
pp. 337-342 ◽  
Author(s):  
Muhammad Aslam ◽  
Payam Shafigh ◽  
Mohd Zamin Jumaat
Keyword(s):  
Oil Palm ◽  
Lightweight Concrete ◽  
Negative Impact ◽  
Raw Materials ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Lightweight Aggregate Concrete ◽  
Lightweight Aggregates ◽  
Aggregate Concrete ◽  
Structural Lightweight Aggregate Concrete

Structural lightweight aggregate concrete offers several benefits as compared to the normal weight concrete. Most common methods of producing structural lightweight concrete is by using artificial lightweight aggregates. However, the cost of the production of artificial lightweight aggregates is high due to energy and raw materials consumption. The use of waste and by-product materials as lightweight aggregate in concrete can provide a better solution to reducing the negative impact of the concrete industry. This paper reports an investigation to produce structural lightweight aggregate concrete by utilizing the locally available solid waste materials, namely oil palm shell (OPS) and oil-palm-boiler clinkers (OPBC) as coarse lightweight aggregates. Two different mix proportions were studied. In the first concrete mix, just OPS was used as coarse aggregate. However, 40% of OPS (by volume) of the first mix was replaced with OPBC in the second mix. The test results showed that by replacing OPS with OPBC, it directly affects the characteristics of the lightweight concrete. The 28-days compressive strength of the blended coarse lightweight aggregate concrete was significantly increased compared to OPS concrete.

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