External Sulphate Attack on Recycled Concrete: Assessment of the Influence of Recycled Aggregate

2019 ◽  
pp. 45-51
Author(s):  
L. R. Santillan ◽  
Y. A. Villagrán Zaccardi ◽  
C. J. Zega
Keyword(s):  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Sulphate Attack

scholarly journals Experimental Study on the Mechanical Properties and Compression Size Effect of Recycled Aggregate Concrete

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2323
Author(s):  
Yubing Du ◽  
Zhiqing Zhao ◽  
Qiang Xiao ◽  
Feiting Shi ◽  
Jianming Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Size Effect ◽  
Compressive Stress ◽  
Failure Modes ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Substitution Ratio ◽  
The Impact

To explore the basic mechanical properties and size effects of recycled aggregate concrete (RAC) with different substitution ratios of coarse recycled concrete aggregates (CRCAs) to replace natural coarse aggregates (NCA), the failure modes and mechanical parameters of RAC under different loading conditions including compression, splitting tensile resistance and direct shear were compared and analyzed. The conclusions drawn are as follows: the failure mechanisms of concrete with different substitution ratios of CRCAs are similar; with the increase in substitution ratio, the peak compressive stress and peak tensile stress of RAC decrease gradually, the splitting limit displacement decreases, and the splitting tensile modulus slightly increases; with the increase in the concrete cube’s side length, the peak compressive stress of RAC declines gradually, but the integrity after compression is gradually improved; and the increase in the substitution ratio of the recycled aggregate reduces the impact of the size effect on the peak compressive stress of RAC. Furthermore, an influence equation of the coupling effect of the substitution ratio and size effect on the peak compressive stress of RAC was quantitatively established. The research results are of great significance for the engineering application of RAC and the strength selection of RAC structure design.

scholarly journals Discrete Element Simulation Analysis of Biaxial Mechanical Properties of Concrete with Large-Size Recycled Aggregate

2021 ◽  
Vol 13 (13) ◽  
pp. 7498
Author(s):  
Tan Li ◽  
Jianzhuang Xiao
Keyword(s):  
Mechanical Properties ◽  
Stress State ◽  
Strain Curve ◽  
Confining Pressure ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Aggregate Model ◽  
Large Size

Concrete made with large-size recycled aggregates is a new kind of recycled concrete, where the size of the recycled aggregate used is 25–80 mm, which is generally three times that of conventional aggregate. Thus, its composition and mechanical properties are different from that of conventional recycled concrete and can be applied in large-volume structures. In this study, recycled aggregate generated in two stages with randomly distributed gravels and mortar was used to replace the conventional recycled aggregate model, to observe the internal stress state and cracking of the large-size recycled aggregate. This paper also investigated the mechanical properties, such as the compressive strength, crack morphology, and stress–strain curve, of concrete with large-size recycled aggregates under different confining pressures and recycled aggregate incorporation ratios. Through this research, it was found that when compared with conventional concrete, under the confining pressure, the strength of large-size recycled aggregate concrete did not decrease significantly at the same stress state, moreover, the stiffness was increased. Confining pressure has a significant influence on the strength of large-size recycled aggregate cocrete.

Shear response of steel fiber reinforced recycled concrete-filled steel tube columns

2021 ◽  
pp. 136943322110093
Author(s):  
Zhenzhen Liu ◽  
Yiyan Lu ◽  
Shan Li ◽  
Jiancong Liao
Keyword(s):  
Axial Compression ◽  
Steel Fiber ◽  
Steel Tube ◽  
Shear Capacity ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Superposition Method ◽  
Fiber Reinforced ◽  
Concrete Filled Steel Tube ◽  
Shear Span

A comprehensive study of the shear characteristics of steel fiber reinforced recycled concrete-filled steel tube (SRCFST) columns is conducted. 50 CFST stub columns are tested with the variables of steel tube diameter-thickness ratio ( D/t), shear span-to-depth ratio (λ), axial compression ratio ( n), and concrete mix. Two types of cements, three recycled aggregate percentages, three water-cement ratios, and three steel fiber contents are considered in design of concrete mixes. The experimental results show that SRCFST columns present the coincident shear behavior of the ordinary CFST columns. As λ is increased, shear resistance shows a downtrend, while the flexural strength presents an increasing trend. Imposing axial compression or thickening steel tube contributes to an adequate safety margin in plastic period. Based on the contributions superposition method, a predicted model of the shear capacity of SRCFST columns is proposed in consideration of shear-span ratio, axial compression, and self-stress.

scholarly journals Characterisation and Life Cycle Assessment of Pervious Concrete with Recycled Concrete Aggregates

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 209
Author(s):  
Adilson C. Paula Junior ◽  
Cláudia Jacinto ◽  
Thaís M. Oliveira ◽  
Antonio E. Polisseni ◽  
Fabio M. Brum ◽  
...  
Keyword(s):  
Environmental Performance ◽  
Treatment Plant ◽  
Recycled Concrete ◽  
Pervious Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Positive Contribution ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates

The search for environmental preservation and conservation of natural resources gives rise to new concepts and viable technical solutions on the path to sustainable development. In this context, this study’s main objective is to analyse the influence of recycled concrete aggregates (RCAs) on the development of pervious concrete, whose use as a floor covering represents an excellent device to mitigate the urban soil sealing phenomena. For this, mechanical and hydraulic tests were carried out, in addition to microstructural analyses and the assessment of its environmental performance. The results obtained were compared to reference studies also involving the incorporation of recycled aggregates. A pilot-scale case study was conducted, involving a parking space lined with pervious concrete moulded “in situ”. In laboratory tests, permeability coefficients and mechanical strengths compatible with the literature and above the normative limit for light traffic were found. The case study demonstrated higher permeability than in the laboratory, but the flexural strength was lower, being indicated only for pedestrian traffic. The environmental assessment showed that the RCA represents a positive contribution to the environmental performance of pervious concrete. Still, attention should be given to the recycled aggregate transport distance between the concrete plant and the RCA treatment plant.

scholarly journals Strength and Water Absorption of Sustainable Concrete Produced with Recycled Basaltic Concrete Aggregates and Powder

2021 ◽  
Vol 13 (11) ◽  
pp. 6277
Author(s):  
Ibrahim Sharaky ◽  
Usama Issa ◽  
Mamdooh Alwetaishi ◽  
Ahmed Abdelhafiz ◽  
Amal Shamseldin ◽  
...  
Keyword(s):  
Water Absorption ◽  
Edge Length ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Partial Substitution ◽  
Small Reduction ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Sustainable Concrete

In this study, the recycled concrete aggregates and powder (RCA and RCP) prepared from basaltic concrete waste were used to replace the natural aggregate (NA) and cement, respectively. The NA (coarse and fine) was replaced by the recycled aggregates with five percentages (0%, 20%, 40%, 60% and 80%). Consequently, the cement was replaced by the RCP with four percentages (0%, 5%, 10% and 20%). Cubes with 100 mm edge length were prepared for all tests. The compressive and tensile strengths (fcu and ftu) and water absorption (WA) were investigated for all mixes at different ages. Partial substitution of NA with recycled aggregate reduced the compressive strength with different percentages depending on the type and source of recycled aggregate. After 28 days, the maximum reduction in fcu value was 9.8% and 9.4% for mixtures with coarse RCA and fine RCA (FRCA), respectively. After 56 days, the mixes with 40% FRCA reached almost the same fcu value as the control mix (M0, 99.5%). Consequently, the compressive strengths of the mixes with 10% RCA at 28 and 56 days were 99.3 and 95.2%, respectively, compared to those of M0. The mixes integrated FRCA and RCP showed higher tensile strengths than the M0 at 56 d with a very small reduction at 28 d (max = 3.4%). Moreover, the fcu and ftu values increased for the late test ages, while the WA decreased.

Study on the Basic Mechanical Properties of Recycled Concrete Hollow Block Masonry

2013 ◽  
Vol 438-439 ◽  
pp. 749-755 ◽  
Author(s):  
Tong Hao ◽  
Dong Li
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Shear Behavior ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Test Results ◽  
Aggregate Concrete ◽  
Mortar Strength ◽  
Hollow Block

By the experimental studying on the basic mechanical properties of recycled concrete hollow block masonry, the compressive and shear behavior of recycled aggregate concrete hollow block masonry under different mortar strength were analyzed. Research indicated that the compressive and shear behavior of recycled aggregate concrete hollow block masonry was similar to that of ordinary concrete hollow block masonry. The normal formula was recommended to calculate the compressive strength of the masonry. The shear strength of the masonry was affected by the mortar strength. The shear strength calculation formula of recycled concrete hollow block masonry was proposed according to the formula of masonry design code. The calculating results were in good agreement with the test results.

Study on the Mechanical Properties and Frost Resistance of Recycled Concrete Prepared by Village Construction Wastes

2011 ◽  
Vol 418-420 ◽  
pp. 406-410
Author(s):  
Jun Liu ◽  
Yao Li ◽  
Dan Dan Hong ◽  
Yu Liu
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Frost Resistance ◽  
Cement Mortar ◽  
Strength Loss ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Replacement Rate ◽  
Concrete Mechanical Properties ◽  
Better Than

Abstract. Recycled aggregate—rural building material wastes pretreated by cement mortar—are applied into concrete with different replacement rates: 0, 25%, 50%, 75%, and 100%. Results from measurements of compressive strength, cleavage tensile strength, mass loss after fast freeze-thaw cycles, and compressive strength loss indicate that a different recycled aggregate replacement rate certainly influences concrete mechanical properties and frost resistance. Recycled aggregate replacement rates less than 75% performs better than common concrete. Data from the 100% replacement rate is worse than that of rates less than 75% but still satisfy the general demands of GB standard on C30 concrete.

Recycling of Waste Concrete and Fly Ash for Recycled Aggregate Concrete: Fundamental Characteristics Evaluation

2009 ◽  
Vol 620-622 ◽  
pp. 255-258 ◽  
Author(s):  
Cheol Woo Park
Keyword(s):  
Fly Ash ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Experimental Program ◽  
Concrete Aggregate ◽  
Fine Aggregate ◽  
Recycled Concrete Aggregate ◽  
Aggregate Concrete ◽  
Waste Concrete

As the amount of waste concrete has been increased and recycling technique advances, this study investigates the applicability of recycled concrete aggregate for concrete structures. In addition fly ash, the industrial by-product, was considered in the concrete mix. Experimental program performed compressive strength and chloride penetration resistance tests with various replacement levels of fine recycled concrete aggregate and fly ash. In most case, the design strength, 40MPa, was obtained. It was known that the replacement of the fine aggregate with fine RCA may have greater influence on the strength development rather than the addition of fly ash. It is recommended that when complete coarse aggregate is replaced with RCA the fine RCA replacement should be less than 60%. The recycled aggregate concrete can achieve sufficient resistance to the chloride ion penetration and the resistance can be more effectively controlled by adding fly ash. It I finally conclude that the recycled concrete aggregate can be successfully used in the construction field and the recycling rate of waste concrete and flay ash should be increased without causing significant engineering problems.

scholarly journals Use of Bioproducts Derived from Mixed Microbial Cultures Grown with Crude Glycerol to Protect Recycled Concrete Surfaces

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2057
Author(s):  
Lorena Serrano-González ◽  
Daniel Merino-Maldonado ◽  
Manuel Ignacio Guerra-Romero ◽  
Julia María Morán-del Pozo ◽  
Paulo Costa Lemos ◽  
...  
Keyword(s):  
Water Absorption ◽  
Crude Glycerol ◽  
Protective Layer ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
World Population ◽  
Management Problem ◽  
Waste Glycerol ◽  
Microbial Cultures ◽  
Mixed Microbial Cultures

The large increase in the world population has resulted in a very large amount of construction waste, as well as a large amount of waste glycerol from transesterification reactions of acyl glycerides from oils and fats, in particular from the production of biodiesel. Only a limited percentage of these two residues are recycled, which generates a large management problem worldwide. For that reason, in this study, we used crude glycerol as a carbon source to cultivate polyhydroxyalkanoates (PHA)-producing mixed microbial cultures (MMC). Two bioproducts derived from these cultures were applied on the surface of concrete with recycled aggregate to create a protective layer. To evaluate the effect of the treatments, tests of water absorption by capillarity and under low pressure with Karsten tubes were performed. Furthermore, SEM-EDS analysis showed the physical barrier caused by biotreatments that produced a reduction on capillarity water absorption of up to 20% and improved the impermeability of recycled concrete against the penetration of water under pressure up to 2.7 times relative to the reference. Therefore, this bioproduct shown to be a promising treatment to protect against penetration of water to concrete surfaces increasing its durability and useful life.

scholarly journals Shear Behavior of Steel-Fiber-Reinforced Recycled Aggregate Concrete Deep Beams

Buildings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 423
Author(s):  
Nancy Kachouh ◽  
Tamer El-Maaddawy ◽  
Hilal El-Hassan ◽  
Bilal El-Ariss
Keyword(s):  
Shear Behavior ◽  
Shear Capacity ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Steel Fibers ◽  
Recycled Aggregate ◽  
Shear Reinforcement ◽  
Deep Beams ◽  
Control Beam ◽  
Shear Response

Results of an experimental investigation aimed at studying the effect of steel fibers on the shear behavior of concrete deep beams made with a 100% recycled concrete aggregate (RCA) are presented in this paper. The study comprised testing of seven concrete deep beam specimens with a shear span-to-depth ratio (a/h) of 1.6. Two beams were made of natural aggregates (NAs) without steel fibers, two beams were made of a 100% RCA without steel fibers, and three beams were made of RCA-based concrete with steel fibers at volume fractions (vf) of 1, 2, and 3%. Two of the beams without steel fibers included a minimum shear reinforcement. Test results showed that the beam with a 100% RCA without steel fibers exhibited a lower post-cracking stiffness, reduced shear cracking load, and lower shear capacity than those of the NA-based control beam. The detrimental effect of the RCA on the shear response was less pronounced in the presence of the minimum shear reinforcement. The addition of steel fibers significantly improved the shear response of the RCA-based beams. The post-cracking stiffness of the RCA-based concrete beams with steel fibers coincided with that of a similar beam without fibers containing the minimum shear reinforcement. The use of steel fibers in RCA beams at vf of 1 and 2% restored 80 and 90% of the shear capacity, respectively, of a similar beam with the minimum shear reinforcement. The response of the RCA specimen with vf of 3% outperformed that of the NA-based control beam with the minimum shear reinforcement, indicating that steel fibers can be used in RCA deep beams as a substitution to the minimum shear reinforcement. The shear capacities obtained from the tests were compared with predictions of published analytical models.

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