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 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.

scholarly journals Experimental Evaluation of Shrinkage, Creep and Prestress Losses in Lightweight Aggregate Concrete with Sintered Fly Ash

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3895
Author(s):  
Rafał Stanisław Szydłowski ◽  
Barbara Łabuzek
Keyword(s):  
Fly Ash ◽  
Prestressed Concrete ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Lightweight Aggregate Concrete ◽  
Clear Correlation ◽  
Aggregate Concrete ◽  
Normal Weight Concrete ◽  
Creep Coefficient ◽  
Shrinkage And Creep

The paper presents the experimental results of shrinkage, creep, and prestress loss in concrete with lightweight aggregate obtained by sintering of fly ash. Two concrete mixtures with different proportions of components were tested. Concrete with a density of 1810 and 1820 kg/m3, and a 28-day strength of 56.9 and 58.4 MPa was obtained. Shrinkage and creep were tested on 150 × 250 × 1000 mm3 beams. Creep was tested under prestressing load for 539 days and concrete shrinkage for 900 days. The measurement results were compared with the calculations carried out according to the Eurocode 2 as well as with the results of other research. A very low creep coefficient and lower shrinkage in relation to the calculation results and the results of other research were found. It was also revealed that there is a clear correlation between shrinkage and creep, and the amount of water in the concrete. The value of the creep coefficient during the load holding period was 0.610 and 0.537, which is 56.0 and 49.3% of the value determined from the standard. The prestressing losses in the analyzed period amounted to an average of 13.0%. Based on the obtained test results, it was found that the tested lightweight aggregate concrete is well suited for prestressed concrete structures. Shrinkage was not greater than that calculated for normal weight concrete of a similar strength class, which will not result in increased loss of prestress. Low creep guarantees low deflection increments over time.

On the Durability of Concrete under the Action of Ultra-Low (up to -196 °C) Technological Temperatures

2021 ◽  
Vol 887 ◽  
pp. 406-414
Author(s):  
V.N. Yarmakovsky ◽  
D. Kadiev
Keyword(s):  
Lightweight Aggregate ◽  
Normal Weight ◽  
Air Separation ◽  
Inert Gases ◽  
Lightweight Aggregate Concrete ◽  
Experimental Investigations ◽  
Cryogenic Temperatures ◽  
Aggregate Concrete ◽  
Normal Weight Concrete ◽  
Structural Lightweight Aggregate Concrete

The article presents the physical-chemical bases and as result – the technological bases of concrete resistance to ultra-low cryogenic (up to-196 °C) technical (engineering) temperatures, which is applied to the reinforced concrete structures of engineering constructions such as storage tanks for liquefied gases (in particular, liquid nitrogen and oxygen with cryogenic temperatures), as well as the enclosing structures of blocks (units) for air separation for various inert gases. The above-mentioned physical and chemical bases of concrete resistance to the ultralow cryogenic technical temperatures are developed, using the results of the analysis of modern ideas (hypotheses and theories) about the mechanism of low negative temperatures exposure on structural lightweight aggregate concrete and normal weight concrete due to the characteristics of their macro-and microstructure. The resistance of structural lightweight aggregate concrete in comparison with equal-strength normal weight concrete to the cyclic exposure of cryogenic temperatures was performed by the authors based on the results of the relevant analytical and experimental investigations. The results of these investigations are considered in the article as a modern scientific basis for the development of the main provisions for the manufacturing technology of structural lightweight aggregate concrete and normal weight concrete with high durability (frost resistance and water resistance) in conditions of cyclic exposure to cryogenic temperatures. The results of changes in strength and deformative characteristics of concrete in the process of cyclic freezing and thawing are accepted as evaluation criteria of the resistance of concrete, manufactured using the above-mentioned technologies, to such temperature exposure.

scholarly journals A Review on the Carbonation and Chloride Penetration Resistance of Structural Lightweight Aggregate Concrete

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3456 ◽  
Author(s):  
José Alexandre Bogas ◽  
Sofia Real
Keyword(s):  
Service Life ◽  
Life Prediction ◽  
Current Knowledge ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Service Life Prediction ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Concrete ◽  
Normal Weight Concrete ◽  
Structural Lightweight Aggregate Concrete

This paper presents a comprehensive review on structural lightweight aggregate concrete (SLWAC) durability. The main transport properties and degradation mechanisms of reinforced concrete are addressed, namely, carbonation and chloride attack. The influence of the main composition parameters, such as type of aggregate, type of binder and water/binder ratio, as well as the influence of cracking, are also analysed. Finally, the current knowledge of SLWAC’s service life prediction is assessed. Although the knowledge of SLWAC’s durability behaviour is still limited, investigation works performed either in laboratory or in real environments indicate that SLWAC can have similar to better durability performance than normal weight concrete, especially when the same strength level is considered. The importance of the quality of the paste over the characteristics of the lightweight aggregates is highlighted. Durability standardization regarding SLWAC is still insufficient and is one of the main gaps of current knowledge. The objective of this review is to foster a better understanding on the durability and service life prediction of SLWAC, contributing to a greater confidence in using this type of concrete.

scholarly journals Post-peak Behaviour of Composite Column Using a Ductile Lightweight Aggregate Concrete

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Mohammad Reza Hamidian ◽  
Payam Shafigh
Keyword(s):  
Load Capacity ◽  
Compressive Load ◽  
Lightweight Aggregate ◽  
Steel Tube ◽  
Normal Weight ◽  
International Standards ◽  
Lightweight Aggregate Concrete ◽  
Green Composite ◽  
Composite Column ◽  
Normal Weight Concrete

AbstractOil palm shell (OPS) concrete filled steel tube (CFT) columns are acknowledged to be a new type of sustainable composite column. In this type of column, the conventional coarse aggregate was partially replaced with OPS lightweight aggregate to provide a green composite column. This type of CFT column showed higher energy absorption and flexibility compared to CFT columns with normal weight concrete. This research studied the effect of the strength of OPS concrete on the axial compressive behaviour of CFT columns for two grades of OPS concretes. The behaviour was comparable to that of CFT columns with two grades of normal concrete. The results showed that the CFT columns with OPS concrete achieved a new post-peak behaviour. The experimental results of the axial compressive load were compared with the estimation of two international standards. EC4-1994 and ACI318-14 showed a reliable and conservative estimation of the axial load capacity of CFT columns, respectively.

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.

scholarly journals Efficiency factor and modulus of elasticity of lightweight concrete with expanded clay aggregate

2010 ◽  
Vol 3 (2) ◽  
pp. 195-204 ◽  
Author(s):  
W.G Moravia ◽  
A. G. Gumieri ◽  
W. L. Vasconcelos
Keyword(s):  
Compressive Strength ◽  
Modulus Of Elasticity ◽  
Large Scale ◽  
Lightweight Concrete ◽  
Weight Ratio ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Lightweight Aggregate Concrete ◽  
Empirical Methods ◽  
Normal Weight Concrete

Nowadays lightweight concrete is used on a large scale for structural purposes and to reduce the self-weight of structures. Specific grav- ity, compressive strength, strength/weight ratio and modulus of elasticity are important factors in the mechanical behavior of structures. This work studies these properties in lightweight aggregate concrete (LWAC) and normal-weight concrete (NWC), comparing them. Spe- cific gravity was evaluated in the fresh and hardened states. Four mixture proportions were adopted to evaluate compressive strength. For each proposed mixture proportion of the two concretes, cylindrical specimens were molded and tested at ages of 3, 7 and 28 days. The modulus of elasticity of the NWC and LWAC was analyzed by static, dynamic and empirical methods. The results show a larger strength/ weight ratio for LWAC, although this concrete presented lower compressive strength.

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.

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