scholarly journals Mechanical Properties and Conversion Relations of Strength Indexes for Stone/Sand-Lightweight Aggregate Concrete

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Xianggang Zhang ◽  
Dapeng Deng ◽  
Jianhui Yang
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Poisson’S Ratio ◽  
Lightweight Aggregate ◽  
Poisson's Ratio ◽  
Lightweight Aggregate Concrete ◽  
Replacement Rate ◽  
River Sand ◽  
Aggregate Concrete ◽  
Axial Compressive Strength

This is a study of the basic mechanical properties of specified density shale aggregate concrete, which is based on different replacement rates in stone-lightweight aggregate concrete (stone-LAC) and sand-lightweight aggregate concrete (sand-LAC). They were prepared by replacing the ceramsite and pottery sand with stone and river sand, respectively. Many tests were performed regarding the basic mechanical property indexes, including tests of cube compressive strength, axial compressive strength, splitting tensile strength, flexural strength, elastic modulus and Poisson’s ratio. The failure modes of specified density shale aggregate concrete were obtained. The effects of replacement rates on the mechanical property indexes of specified density shale aggregate concrete were analyzed. Calculation models were implemented for elastic modulus, for the conversion relations between the axial compressive strength and the cube compressive strength, and for the relations between the tension-compression ratio and Poisson’s ratio. It was shown that when the replacement rate of stone or river sand increased from 0% to 100%, the cube compressive strength of stone-LAC and sand-LAC increased, respectively, by 55% and 25%, the axial compressive strength increased, respectively, by 91% and 72%, splitting tensile strength increased, respectively, by 99% and 44%, and the flexural strength increased, respectively, by 46% and 26%. Similarly, the elastic modulus of stone-LAC and sand-LAC increased, respectively, by 16% and 30%. However, Poisson’s ratio for stone-LAC decreased first and then increased, eventually increased by 11%; Poisson’s ratio for sand-LAC only reduced gradually, eventually reduced by 67%. After introducing the influence parameter for the replacement rate, the established calculation models become simple and practical, and the calculation accuracies are favorable.

scholarly journals Study on Mechanical Properties of PET Fiber-Reinforced Coal Gangue Fine Aggregate Concrete

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Yanlin Huang ◽  
An Zhou
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Plain Concrete ◽  
Coal Gangue ◽  
Fine Aggregate ◽  
Replacement Rate ◽  
River Sand ◽  
Aggregate Concrete

In recent years, with the rapid development of the construction industry, the demand for natural river sand has become increasingly prominent. Development of alternatives to river sand has become an interesting direction for concrete research. In this paper, coal gangue was proposed to replace part of the river sand to produce coal gangue fine aggregate concrete, while waste polyethene terephthalate (PET) bottles were used as raw materials to make PET fibers to improve the mechanical properties of coal gangue fine aggregate concrete. There were two parts of the test conducted. In the first part, the compressive strength of the gangue fine aggregate concrete cube, splitting tensile strength, axial compressive strength, and static elastic modulus were studied when the substitution rate of coal gangue increased from 0% to 50%. Referring to the equation of the full stress-strain curve of plain concrete, the stress-strain constitutive equation of coal gangue fine aggregate concrete was analyzed and studied. By comparing with plain concrete, it was found that the coal gangue concrete with a replacement rate of 50% had higher compressive strength and tensile strength, but its brittleness was significantly greater than that of plain concrete in the later stage. In the second part, by studying the effect of different PET fiber content on the mechanical properties of coal gangue fine aggregate concrete with a replacement rate of 50%, it was found that when the addition of PET fiber was 0.1% and 0.3%, not only were compressive strength, splitting tensile strength, static elastic modulus, and flexural strength of the gangue fine aggregate concrete effectively improved but also the brittleness of concrete can be significantly reduced. The study found that after adding 0.3% PET fiber, the coal gangue fine aggregate concrete with a replacement rate of 50% has better mechanical properties and less brittleness.

Compressive Strength Variations in Lightweight Aggregate Concrete Samples Affected by Segregation Caused by Excessive Vibration

2019 ◽  
Vol 821 ◽  
pp. 493-499 ◽  
Author(s):  
Afonso Miguel Solak ◽  
Antonio José Tenza-Abril
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniform Distribution ◽  
Lightweight Aggregate ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Concrete ◽  
Global Properties ◽  
Concrete Failure ◽  
Good Homogeneity ◽  
Cylindrical Samples

Lightweight aggregates used in lightweight aggregate concrete (LWAC) exert an important influence on the compressive strength and elastic modulus of concrete. A good homogeneity of the material is essential in this type of concrete once a non-uniform distribution of aggregates in the mixture may strongly affect the concrete global properties, which are commonly considered as homogenous values for design purposes. LWAC, due to density differences among its components, are susceptive to segregation. The separation of the aggregates from the rest of the mixture increases the risk of cracking and areas where segregation or insufficient compaction occur are mostly the areas where the concrete failure begins. The aim of this study is analysing possible variations caused by segregation on compressive strength (fc) along the height of cylindrical samples, comparing results of four sections extracted from samples segregated intentionally.

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.

scholarly journals Experimental Research on the Mechanical Characteristics and the Failure Mechanism of Coal-Rock Composite under Uniaxial Load

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Ke Yang ◽  
Zhen Wei ◽  
Xiaolou Chi ◽  
Yonggang Zhang ◽  
Litong Dou ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Elastic Modulus ◽  
Crack Propagation ◽  
Failure Mechanism ◽  
Poisson’S Ratio ◽  
Mechanical Characteristics ◽  
Poisson's Ratio ◽  
Energy Value ◽  
Coal Rock

Due to the influence of the component structure and combination modes, the mechanical characteristics and failure modes of the coal-rock composite show different characteristics from the monomer. In order to explore the effect of different coal-rock ratios on the deformation and the failure law of the combined sample, the RMT rock mechanics test system and acoustic emission real-time monitoring system are adopted to carry out uniaxial compression tests on coal, sandstone, and three kinds of combined samples. The evolution rules of the mechanical parameters of the combined samples, such as the uniaxial compressive strength, elastic modulus, and Poisson’s ratio, are obtained. The expansion and failure deformation characteristics of the combined sample are analyzed. Furthermore, the evolution laws of the fractal and acoustic emission signals are combined to reveal the crack propagation and failure mechanism of the combined samples. The results show that the compressive strength and elastic modulus of the combined sample increase with the decrease of the coal-rock ratios, and Poisson’s ratio decreases with the decrease of the coal-rock ratios. The strain softening weakens at the postpeak stage, which shows an apparent brittle failure. The combined sample of coal and sandstone has different degrees of damages under load. The coal is first damaged with a high degree of breakage, with obvious tensile failure. The acoustic emission energy value presents different stage characteristics with increasing load. Crackling sound occurs in the destroy section before the sample reaches the peak, along with small coal block ejection and the partial destruction. The energy value fluctuates violently, with the appearance of several peaks. At the postpeak stage, the coal samples expand rapidly with a loud crackling sound in the destroy section, and the energy value increases dramatically. The crack propagation induces the damage in the sandstone; when the energy reaches the limit value, the instantaneous release of elastic energy leads to the overall structural instability.

Test Research on Elastic Modulus and Poisson’s Ratios of Long Age Recycled Aggregate Concrete

2012 ◽  
Vol 174-177 ◽  
pp. 1051-1055 ◽  
Author(s):  
Wei Ning Li ◽  
Dong Hui Zhan ◽  
Jin Jun Xu ◽  
Wen Zhang ◽  
Zong Ping Chen
Keyword(s):  
Elastic Modulus ◽  
Time Effect ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Compression Tests ◽  
Replacement Rate ◽  
Aggregate Concrete ◽  
Axial Compressive Strength ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

In order to reveal the constitutive behavior of recycled aggregate concrete (RAC) which is related to time effect, 33 prismatic specimens were designed to have uniaxial compression tests. The changing variation of elastic modulus and Poisson’s ratios of RAC specimens which were placed two years in the lab were inspected, and a related correction formula was put forward to describe the elastic modulus. The results show that with the aggregate replacement rate growing, the RAC brittleness was relatively obvious. Since time effect played a great role, the axial compressive strength and elastic modulus were larger than those of normal concrete and the standard age concrete which is calculated. Poisson's ratio did not change significantly and the values were relatively stable, while the higher replacement rate is, the lower values are.

scholarly journals Fresh and Mechanical Properties of Self-Compacting Rubber Lightweight Aggregate Concrete and Corresponding Mortar

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Jing Lv ◽  
Qiang Du ◽  
Tianhua Zhou ◽  
Zuoqian He ◽  
Kunlun Li
Keyword(s):  
Compressive Strength ◽  
Shear Stress ◽  
Lightweight Aggregate ◽  
Segregation Ratio ◽  
Plastic Viscosity ◽  
Lightweight Aggregate Concrete ◽  
Replacement Ratio ◽  
Aggregate Concrete ◽  
Waste Tires ◽  
Rubber Particles

Increasing amount of waste tires caused huge environment issues in recent years. Recycling concrete is an effective way. In this paper, waste tires are crushed into particles and incorporated in lightweight aggregate concrete to prepare a special concrete (self-compacting rubber lightweight aggregate concrete (SCRLC)). A detailed experimental research of effects of rubber particles on the properties of SCRLC and corresponding mortar is conducted. The results show that increasing the rubber particles replacement ratio leads to a raising of yield stress and plastic viscosity of mortar pastes. Flowability, filling capacity, and passing ability of SCRLC decline and the segregation resistance property of SCRLC improves as the rubber particles replacement ratio increases. Well, linear correlations between slump flow of SCRLC and shear stress of corresponding mortar pastes and segregation ratio of SCRLC and plastic viscosity of corresponding mortar pastes are obtained. In order to ensure that rubber lightweight aggregate concrete can compact by itself, the upper limit of shear stress of corresponding mortar pastes is 231.7 Pa and the lower limit of plastic viscosity of corresponding mortar pastes is 3.72 Pa·s. Compressive strength, splitting tensile strength, flexural strength, and elastic modulus of SCRLC and compressive strength of corresponding mortar decrease as the rubber particles replacement ratio increases. The 28-day compressive strength of SCRLC can meet the requirements of lightweight aggregate concrete structures until the rubber particles replacement ratio reaches 50%.

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