scholarly journals Study the effect of vibration mixing on the performances of full replacement recycled aggregate concrete

2021 ◽  
Vol 276 ◽  
pp. 02027
Author(s):  
Taotao Li
Keyword(s):  
Compressive Strength ◽  
Solid Waste ◽  
Building Materials ◽  
Engineering Application ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Carbonation Depth ◽  
Aggregate Concrete ◽  
Natural Aggregate ◽  
Splitting Strength

It is an urgent problem that the construction solid waste is difficult to be treated, and its recycling provides a way for its treatment. The quality of construction solid waste recycled aggregate is lower than that of natural aggregate, which limits its extensive application in building materials. In order to provide a new method for engineering application of recycled aggregate concrete, the influence of vibration mixing on the performances of full replacement recycled aggregate concrete were studied. The performance indexes of recycled aggregate concrete under ordinary mixing and vibration mixing were compared and analyzed. The experimental results show that compared with natural aggregate concrete, the slump of full replacement recycled aggregate concrete decreased by 58.8%, and 7d and 28d compressive strength decreased by 12.9% and 16.1%, and the splitting strength decreased by 30.6% and 20.1%, and the carbonation depth decreased by 91.5%; Compared with natural aggregate concrete using ordinary mixing, the slump of full replacement recycled aggregate concrete using vibration mixing decreased by 50.9%, the 7d and 28d compressive strength decreased by 6.9% and 10.9%, and the splitting strength decreased by 16.9% and 12.4%, and the 28d carbonation depth decreased by 34.9%. The results show that compared with ordinary mixing, vibration mixing can improve the performance of recycled aggregate concrete, which provides a reference for engineering application.

scholarly journals Experimental study on the influence of recycled aggregates on the mechanical properties of concrete

2021 ◽  
Vol 283 ◽  
pp. 01033
Author(s):  
Chuangui Li ◽  
Hongkui Zhao ◽  
Jianfeng Wu ◽  
Xiangang Li ◽  
Ya Zhang
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Solid Waste ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Cohesive Force ◽  
Recycled Aggregates ◽  
Replacement Rate ◽  
Aggregate Concrete ◽  
Splitting Strength

Construction solid waste has become an important environmental pollution source in the city, and the treatment and application of construction solid waste has become the focus of attention. Construction waste recycled aggregates have defects such as high water absorption and micro cracks, which affect its extensive application. In order to improve the utilization rate of recycled aggregates, the influence of different replacement rates of recycled aggregates on the mechanical properties of concrete is studied in this paper. The results show that with the increase of replacement rate of recycled aggregates, the 3-day, 7-day and 28-day compressive strength, splitting strength and cohesive force of concrete decrease gradually, but the mechanical properties of concrete decrease slowly at 3 days and 7 days, and decrease obviously at 28 days. Moreover, with the increase of replacement rate of recycled aggregates, the decline trend of mechanical properties is not obvious. Compared with natural aggregate concrete, the 28-day compressive strength, splitting strength and cohesive force of 100% recycled aggregate concrete are reduced by 16.1%, 20.1% and 18.1% respectively, but the mechanical properties meet the requirements of C30 concrete, which provides a reference for engineering application.

scholarly journals Probabilistic Conversion of the Compressive Strength of Cubes to Cylinders of Natural and Recycled Aggregate Concrete Specimens

Materials ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 280 ◽  
Author(s):  
João Pacheco ◽  
Jorge de Brito ◽  
Carlos Chastre ◽  
Luís Evangelista
Keyword(s):  
Compressive Strength ◽  
Conversion Factor ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Structural Behaviour ◽  
Aggregate Concrete ◽  
Coarse Aggregates ◽  
Natural Aggregate ◽  
Using Data ◽  
The Relationship

This paper investigates the effect of recycled coarse aggregate incorporation on the relationship between 150 mm cubic and Փ 150 mm cylindrical compressive strength (the reference strength of standards) by comparing data from recycled and natural aggregate concrete compositions in which both cubes and cylinders were tested. A conversion factor from cubic to cylindrical strength is proposed in two versions: A deterministic and a probabilistic one. Such factor has not been studied before and researchers have been converting cubic data as if natural aggregate concrete were tested. The probabilistic factor is intended for reliability analyses on the structural behaviour of recycled aggregate concrete using data from laboratory cube tests. It was found that the incorporation of recycled coarse aggregates sourced from concrete waste significantly decreases the expected value of the factor but the factor’s scatter is relatively unaffected.

Microscopic Analysis and Experimental Research on Thermal Mechanical Behavior of Natural Aggregate Concrete

2010 ◽  
Vol 129-131 ◽  
pp. 1039-1042
Author(s):  
H.Q. Yan ◽  
Q.Y. Wang
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
Mechanical Behavior ◽  
Microscopic Analysis ◽  
Test Methods ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Strength Analysis ◽  
Aggregate Concrete ◽  
Natural Aggregate

Reinforced concrete construction is very common recently and extensively used both in industrial and commercial buildings. With the gradual rise in occurrences of fire accidents in recent years, a more thorough and quantitative understanding of the damage phenomenon in concrete structures is required. However, the mechanical behavior of concrete could actually be more complex under high temperature conditions than at room temperature. Restoration and reinforcement of the structures exposed to fire may have to be based on residual strength analysis and therefore require a correlation between temperature and mechanical properties. Thus, in order to meet the modern challenges of rapid engineering advances and societal development, further research on the concrete material and its structural behavior at high temperatures becomes extremely important. The present paper deals with investigations on the effect of high temperature exposure on the compressive strength of natural aggregate concrete. Experiments were conducted to study the compressive strength variations with increasing temperatures, up to 700 °C, and the subsequent cooling modes such as natural and spray cooling. Results show that the compressive strength gradually decreases with increasing temperatures. And micro-structural observations of the concrete specimens by means of scanning electron microscopy (SEM) were obtained. These test methods and results can be used for analyzing and investigating the behavior of recycled aggregate concrete with increasing temperatures.

scholarly journals Utilization of Demolished Waste as Coarse Aggregate in Concrete

2019 ◽  
Vol 5 (3) ◽  
pp. 540 ◽  
Author(s):  
Abdulsamee M Halahla ◽  
Mohammad Akhtar ◽  
Amin H. Almasri
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Recycled Concrete ◽  
International Standards ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Test Results ◽  
Aggregate Concrete ◽  
Natural Aggregate ◽  
Concrete Building

Demolishing concrete building usually produces huge amounts of remains and wastes worldwide that have promising possibilities to be utilized as coarse aggregate for new mixes of concrete. High numbers of structures around the world currently need to be removed for several reasons, such as reaching the end of the expected life, to be replaced by new investments, or were not built by the local and international standards. Maintaining or removal of such structures leads to large quantities of concrete ruins. Reusing these concrete wastes will help in saving landfill spaces in addition to more sustainability in natural resources. The objective of this study is to investigate the possibility of using old recycled concrete as coarse aggregate to make new concrete mixes, and its effect on the evolution of the compressive strength of the new concrete mixes.  Core samples for demolished concrete were tested to determine its compressive strength. The core test results can be thought of as aggregate properties for the new concrete. Then, the compressive strength and splitting tensile strength of the new recycled aggregate concrete (RAC) were determined experimentally by casting a cubes and cylinders, respectively. It was found that the evolution of compressive strength of recycled aggregate concrete is similar in behavior to the concrete with natural aggregate, except that it is about 10% lower in values. It was also seen that water absorption for recycled aggregate is noticeably higher than that for natural aggregate, and should be substituted for in the mix design.

scholarly journals Mechanical Performance of Recycled Aggregate Concrete Containing Lathe Waste Steel Fibre

2021 ◽  
Vol 17 (4) ◽  
pp. 306-311
Author(s):  
S.A. Alabi ◽  
C. Arum
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Building Materials ◽  
Steel Fibre ◽  
Mechanical Performance ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Concrete Aggregate ◽  
Aggregate Concrete

The increasing demand, diminishing supplies, and growing pressure on natural resources have necessitated recycling and reusing waste. Several kinds of research have been done on the reuse and recycling of debris from building projects. Thus, with a view to the reuse of waste materials, the elimination of environmental contamination, the reduction of overhead costs of concrete, and the extension of the service life of concrete structures, this research aimed to study the feasibility of utilizing recycled concrete aggregate (RCA) with constant inclusion of waste steel fibre (LWSF) in concrete by evaluating its workability, compressive and splitting tensile strengths. A concrete mix ratio of 1:2:4 by weight of cement, sand, and granite was adopted with a water-cement ratio of 0.45. Five different concrete mixes were prepared in this study; one normal aggregate concrete (NAC) and four (4) other mixes with 25%, 50%, 75%, and 100% recycled aggregate content with a constant 1.5% addition of LWSF. The result of workability shows a reduction with an increase in the percentage replacement level. The recycled aggregate concrete (RAC) was characterized by lower compressive strength as compared with the NAC. When the replacement ratio increased from 25% to 50%, a significant reduction of about 14% and 30% were observed in the compressive strength at 7-days, but at 28-days slight increase in the compressive strength was observed. Also, a decrease in splitting tensile strength as the percentage replacement of crushed granite (CG) with RCA is increased was observed. Overall, the findings showed that the RAC-containing LWSF is environmentally sustainable and would significantly reduce the global greenhouse impact and building materials' overall quality. Keywords: Recycled concrete, lathe waste, steel fibre, compressive strength, tensile strength

Carbonation Depth of Recycled Aggregate Concrete Incorporating Fly Ash

2011 ◽  
Vol 261-263 ◽  
pp. 217-222 ◽  
Author(s):  
Fang Tian ◽  
Wei Xin Hu ◽  
He Ming Cheng ◽  
Ya Li Sun
Keyword(s):  
Fly Ash ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Carbonation Depth ◽  
Aggregate Concrete ◽  
Natural Aggregate ◽  
Gray Theory

This paper addresses the efficiency of using recycled concrete as an aggregate by systematically presenting results on the influence of fly ash on recycled aggregate concrete (RAC) properties. The percentage of recycled aggregate replacements of natural aggregate used by weight was 50%. Fly ash (FA) was used as 0, 10, 20, 30, and 40% by weight replacement of cement. The results showed that an increase in the W/B decreased the resistance to carbonation depth. Nevertheless, the use of FA as a substitute for cement decreased the carbonation depth of the recycled aggregate concrete. Being analyzed on the basis of Gray Theory, it can be seen that the biggest influence on the depth of carbonation of the recycled aggregate concrete comes from W/B, then the carbonation age and FA content affects the least.

Effect of nanocomposite slurry on strength development of fully recycled aggregate concrete

2021 ◽  
pp. 136943322199248
Author(s):  
Tao Meng ◽  
Song-lin Yu ◽  
Huadong Wei ◽  
Sheng Zhu
Keyword(s):  
Compressive Strength ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Strength Development ◽  
Aggregate Concrete ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Natural Aggregate ◽  
Enhancement Method

Recycled concrete has been widely used in construction because of the gradual shortage of natural aggregate resources and the large amount of construction waste. In this study, concrete with 100% recycled aggregate was prepared, and its properties, microtopography, and potential enhancement method were investigated. The results indicated that the mechanical properties of the fully recycled aggregate concrete (FRC) were significantly inferior to the natural aggregate concrete. The compressive strength of the FRC with a water-cement ratio of 0.6 was noticeably improved by spraying a nanocomposite slurry on recycled aggregate, whereas this had little influence when the water-cement ratio was 0.3. The compressive strength of the FRC with a water-cement ratio of 0.3 could be improved by mixing with strengthening materials. The best improvement in the compressive strength of the concrete was observed at 28 days because a membrane covered the surface of the aggregate, creating a bond between the aggregate and cement, filling the pores between them, and compacting the concrete. This paper reports a prospective method for improving the properties of FRC, which will promote the application of recycled aggregate in industry.

PROPERTIES OF CONCRETE MADE WITH RECYCLED COARSE AGGREGATES FROM OLD CONCRETE CUBES

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
I. H. Adebakin ◽  
J. T. Adu ◽  
O. M. Ofuyatan
Keyword(s):  
Compressive Strength ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Low Grade ◽  
Aggregate Concrete ◽  
Coarse Aggregates ◽  
Natural Aggregate ◽  
Absolute Volume ◽  
Close Proximity ◽  
Volume Method

Sustainability in the construction industry is a global concern, and one way of handling this is the idea of recycling old concrete rubbles in the production of fresh concrete. Recycled aggregate concrete is normally classified as light weight concrete and recommended for use in production of low-grade non-structural elements. This study examined the properties of crushed old concrete cubes as replacement for natural aggregate. Five specimens 150x150mm concrete cubes with varying percentages of coarse recycled aggregate of 0 %( control), 25, 50, 75 and 100% were prepared. All the mixes were proportioned using the absolute volume method with a targeted compressive strength of 30N/mm2 and varying w/c ratio. The result shows that with up to 75% replacement of natural aggregate with recycled aggregate, the 28 days compressive strength of concrete is in close proximity with that of normal concrete. While the strength of exclusive recycled aggregate concrete is about 15% lesser than that of exclusive natural aggregate. The result of this research confirms that crushed old concrete cubes can be safely used in the production of high grade concrete.

The Durability of Fine Recycled Aggregate Concrete

2017 ◽  
Vol 1144 ◽  
pp. 59-64 ◽  
Author(s):  
Magdaléna Šefflová ◽  
Tereza Pavlů
Keyword(s):  
Compressive Strength ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Carbonation Depth ◽  
Natural Sand ◽  
Conventional Concrete ◽  
Aggregate Concrete ◽  
Freeze Thaw ◽  
Concrete Mixtures

This paper is focused on the durability of recycled aggregate (FRA) concrete. The durability of FRA concrete is connected with many uncertainties and doubts. This paper presents results of long-term of compressive strength, freeze – thaw resistance and carbonation depth of FRA concrete. The FRA was originated from crushed old concrete structures. There were prepared a total four concrete mixture. The first mixture was reference with natural sand. In other concrete mixtures, natural sand was replaced by the FRA in various replacement ratios, specifically 10 %, 20 % and 30 %. All prepared concrete mixtures were designated with the same parameters for clear comparison. It is possible to say that according to the durability, the FRA concrete is possible to used in the same applications as conventional concrete. However it is necessary to verify this results.

scholarly journals Feasibility of Using Nanoparticles of SiO2 to Improve the Performance of Recycled Aggregate Concrete

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Khaleel H. Younis ◽  
Shelan M. Mustafa
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Water Absorption ◽  
Splitting Tensile Strength ◽  
Recycled Aggregate Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Demolition Waste ◽  
Aggregate Concrete ◽  
Natural Aggregate

The aim of this paper was to examine the feasibility of using nanoparticles of SiO2 (nanosilica) to improve the performance of recycled aggregate concrete (RAC) containing recycled aggregate (RA) derived from processing construction and demolition waste of concrete buildings. The examined properties include compressive strength, splitting tensile strength, and water absorption. The study also includes examining the microstructure of RA and RAC with and without nanoparticles of SiO2. In total, nine mixes were investigated. Two mixes with RA contents of 50% and 100% were investigated and for each RA content; three mixes were prepared with three different nanoparticles dosages 0.4%, 0.8%, and 1.2% (by mass of cement). A control mix with natural aggregate (NA) was also prepared for comparison reasons. The results show that nanoparticles of silica can improve the compressive strength, tensile strength, reduce the water absorption, and modify the microstructure of RAC.

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