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.

The potency of recycled aggregate in new concrete: a review

2019 ◽  
Vol 19 (4) ◽  
pp. 594-613 ◽  
Author(s):  
Emmanuel Ejiofor Anike ◽  
Messaoud Saidani ◽  
Eshmaiel Ganjian ◽  
Mark Tyrer ◽  
Adegoke Omotayo Olubanwo
Keyword(s):  
Research Work ◽  
Recycled Aggregate Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Mix Design ◽  
Recycled Aggregates ◽  
Demolition Waste ◽  
Aggregate Concrete ◽  
Content Type ◽  
Natural Aggregate

Purpose This paper aims to review the effect of using recycled aggregates (RA) on the properties of recycled aggregate concrete (RAC) following the steady rise in global demand for concrete and the large generation of construction and demolition waste. Design/methodology/approach This study reviewed relevant literature of research work carried out by previous researchers, leading to a deeper understanding of the properties of both RA and RAC. The properties of RA and RAC reported in the various studies were then compared to their corresponding natural aggregate (NA) and natural aggregate concrete, as well as the specifications provided in different codes of practice. In addition, the mix design methods appropriate to RAC and the cost implication of using RA were reviewed. Findings Findings show that the contribution of RA to strength appears inferior in comparison to NA. The shortcoming is attributed to the mortar attached to the RA, which raises its water absorption capacity and lowers its density relative to those of NA. However, it has been reported that the use of regulated quantity of RA, new mixing and proportioning methods, the addition of admixtures and strengthening materials such as steel fibres, can improve both mechanical and durability properties of RAC. Cost evaluation also showed that some savings can be realized by using RA instead of NA. Originality/value This research serves as a guide for future works and suggests that the use of RA as aggregate in new concrete is technically possible, depending on the mix design method adopted.

scholarly journals Mechanical and Durability Properties of Induction-Furnace-Slag-Incorporated Recycled Aggregate Concrete

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Syed Ishtiaq Ahmad ◽  
Md. Shafiqur Rahman
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Modulus Of Elasticity ◽  
Induction Furnace ◽  
Splitting Tensile Strength ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Durability Properties ◽  
Furnace Slag

Most of the steel mills in Bangladesh use induction furnace which produces large quantities of slags that have very little use except land filling. Therefore, feasibility of using this slag is examined in concrete with recycled aggregate, which is another waste product that is generated due to removal of old structures. Concrete with three target strengths, 17.23, 20.68, and 24.13 MPa, was prepared using recycled concrete acquired from a recently demolished building in Dhaka, Bangladesh. Recycled coarse aggregate was replaced with induction furnace slag by 0%, 25%, 50%, 75%, and 100% for each target strength. Samples prepared from these concretes were tested for workability, compressive strength, splitting tensile strength, modulus of elasticity, and durability properties e.g., porosity, absorption, and rapid chloride penetration. Review of test results suggests that workability of concrete was not adversely affected by incorporation of induction furnace slag. For up to 50% of induction furnace slag replacement, both compressive strength and splitting tensile strength increased in recycled aggregate concrete. Further, for all ratios of induction furnace slag replacement, modulus of elasticity increased compared to 100% recycled aggregate concrete. Porosity and absorption also decreased in concrete where up to 50% of recycled aggregate was replaced by induction furnace slag. Considering these, it is concluded that 50% of recycled aggregate can be replaced by induction furnace slag that will result in superior mechanical and durability properties in recycled aggregate concrete.

Recycled Aggregate Concrete Mixture Proportion Method Based on Pulp Content

2014 ◽  
Vol 584-586 ◽  
pp. 1425-1431
Author(s):  
Qing Han ◽  
Zong Ming Jia ◽  
Dong Ye Sun
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Splitting Tensile Strength ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Concrete Mixture ◽  
Concrete Compressive Strength ◽  
Aggregate Concrete ◽  
Proportion Method ◽  
The Relationship

Putting forward a new recycled aggregate concrete mixture proportion method based on the pulp content by researching the effect of pulp content on recycled coarse aggregate physical properties .Research on the cube compressive strength and splitting tensile strength of recycled aggregate concrete by the proposed method and results showed that:The proposed method can reduce the dosage of cement and sand, and increase the recycled aggregate concrete compressive strength and splitting tensile strength ;Establishing the relationship formula between splitting tensile strength and compressive strength of recycled aggregate concrete upon a large number of experimental data.

scholarly journals Analysis of Compressive Fatigue Failure of Recycled Aggregate Concrete

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4620
Author(s):  
Fan You ◽  
Surong Luo ◽  
Jianlan Zheng ◽  
Kaibin Lin
Keyword(s):  
Fatigue Life ◽  
Fatigue Failure ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Recycled Aggregate Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Cycle Fatigue ◽  
Demolition Waste ◽  
Aggregate Concrete

Using recycled aggregate in concrete is effective in recycling construction and demolition waste. It is of critical significance to understand the fatigue properties of recycled aggregate concrete (RAC) to implement it safely in structures subjected to repeated or fatigue load. In this study, a series of fatigue tests was performed to investigate the compressive fatigue behavior of RAC. The performance of interfacial transition zones (ITZs) was analyzed by nanoindentation. Moreover, the influence of ITZs on the fatigue life of RAC was discussed. The results showed that the fatigue life of RAC obeyed the Weibull distribution, and the S-N-p equation could be obtained based on the fitting of Weibull parameters. In the high cycle fatigue zone (N≥104), the fatigue life of RAC was lower than that of natural aggregate concrete (NAC) under the same stress level. The fatigue deformation of RAC presented a three-stage deformation regularity, and the maximum deformation at the point of fatigue failure closely matched the monotonic stress-strain envelope. The multiple ITZs matched the weak areas of RAC, and the negative effect of ITZs on the fatigue life of RAC in the high cycle fatigue zone was found to be greater than that of NAC.

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.

The Properties of Fine Recycled Aggregate Concrete Containing Recycled Bricks from Construction and Demolition Waste

2018 ◽  
Vol 760 ◽  
pp. 193-198 ◽  
Author(s):  
Kristina Fořtová ◽  
Tereza Pavlů
Keyword(s):  
Recycled Aggregate Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Partial Replacement ◽  
Fine Aggregate ◽  
Demolition Waste ◽  
Natural Sand ◽  
Aggregate Concrete ◽  
Freeze Thaw ◽  
Recycled Fine Aggregate

This paper presents research results of recycled fine aggregate concrete testing. The main aim of this contribution is verification of properties of fine aggregate concrete with partial replacement of fine natural aggregate by recycled masonry aggregate originated from construction and demolition waste. The influence of partial replacement of natural sand to mechanical properties and freeze-thaw resistance is described. The compressive strength and flexural strength were tested at the age of 28 and 60 days and after 25, 50, 75 and 100 freeze-thaw cycles. Partial replacement of natural sand was 0, 25 and 50 % for all these tests. Prismatic specimens were examined.

Shear strength of reinforced concrete beams with recycled aggregates

2019 ◽  
Vol 22 (8) ◽  
pp. 1938-1951 ◽  
Author(s):  
George Wardeh ◽  
Elhem Ghorbel
Keyword(s):  
Tensile Strength ◽  
Shear Strength ◽  
Strain Softening ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Opening Displacement ◽  
Aggregate Concrete ◽  
Natural Aggregate ◽  
Hinge Model

This article presents an experimental program on the shear behavior of beams without transversal reinforcement manufactured with natural aggregate concrete and 100% recycled aggregate concrete. The beams were tested under four-point bending for a shear span-to-depth ratio ( a/ d) equal to 1.5 and 3.0. The mechanical properties of two mixes were characterized in terms of compressive strength, splitting tensile strength, and elastic modulus. Three-point bending tests were performed on plain pre-notched samples in order to determine the fracture properties by an inverse analysis of experimental force–crack mouth opening displacement curves using the analytical nonlinear hinge model and a power law strain-softening relationship. The strain-softening law is described by two parameters being, respectively, the power n and the critical crack opening displacement wc. The experimental results show that, for the same class of compressive strength, tensile strength, fracture energy, and the shear strength of recycled aggregate concrete are lower than natural aggregate concrete. The decrease in the fracture energy and the shear strength is consistent with the decrease in the splitting tensile strength of the recycled aggregate concrete mixes compared to the natural aggregate concrete. Critical shear crack theory was adopted to model the shear behavior of beams tested with a/ d = 3.0. For an accurate evaluation of the deformation capacity of tested beams, the nonlinear hinge model for recycled concrete members was extended to recycled concrete sections. For deep beams ( a/ d = 1.5), the strut-and-tie model was used. Finally, comparisons of prediction models to a wide range of experimental data are presented.

scholarly journals Performance of Recycled Aggregate Concrete for M25 Grade Concrete

2019 ◽  
Vol 9 (2) ◽  
pp. 4694-4700
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Aggregate Concrete ◽  
Inorganic Particles ◽  
Natural Aggregates

Recycled aggregates (RCA) are the aggregates which are made up of crushed, inorganic particles that are obtained from the construction demolition debris. Now a day’s protection of environment is the ultimate challenge to the society. So the usage of RCA’s is the best alternative for the aggregates which are obtained naturally in the construction activity. The scope of using these recycled concrete aggregates is increasing day by day. It reduces the cost effectively as we are using waste concrete as recycled aggregates. The main focus of this paper is to use find the strength qualities of recycled aggregates so as to use it as an alternative for the natural aggregates in high strength concrete for various construction activities. Comparison of workability, compressive strength, tensile strength, elastic modulus and flexural strength of recycled aggregate concrete is made with natural aggregate concrete. Here M25 grade concrete is taken and the natural aggregates were replaced with recycled aggregates in various percentages of 0%, 25%, 50%, 75% and 100%. The mix design for these replacement ratios are done by using code of IS 10262-2009. In order to determine the properties which were mentioned above a total of 60 cubes, 10 beams and 40 cylinders were casted. The compressive strength and tensile strength of RCA concrete have been determined for 7 days and 28 days where as the modulus of elasticity and the flexural strength of RCA concrete are determined after curing for the period of 28 days. The tests done on RCA concrete are compared with concrete which is obtained by natural aggregates As per IS codification the parameters which were determined are reducing moderately as the amount of aggregates which are recycled is being raised

scholarly journals Experimental study on mechanical properties and microstructures of steel fiber-reinforced fly ash-metakaolin geopolymer-recycled concrete

2021 ◽  
Vol 60 (1) ◽  
pp. 578-590
Author(s):  
Zhong Xu ◽  
Zhenpu Huang ◽  
Changjiang Liu ◽  
Xiaowei Deng ◽  
David Hui ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Fly Ash ◽  
Steel Fiber ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Mix Proportion ◽  
Optimal Mix

Abstract Geopolymer cementitious materials and recycled aggregate are typical representatives of material innovation research in the engineering field. In this study, we experimentally investigated a method to improve the performance of geopolymer-recycled aggregate concrete (GRAC). The recycled concrete aggregates and steel fiber (SF), fly ash (FA), metakaolin (MK), and sodium silicate solution were used as the main raw materials to prepare fiber-reinforced geopolymer-recycled aggregate concrete (FRGRAC). First, the orthogonal test was carried out to study the GRAC, and the optimal mix proportion was found. Second, building on the optimal mix proportion, the effects of the SF content on the slump, 7 and 28 days compressive strength, tensile strength, and flexural strength of FRGRAC were further studied. Finally, the microscopic mechanism of FRGRAC was studied by scanning electron microscopy (SEM). The study results indicate that the slump continues to decrease as the fiber content increases, but the compressive strength, tensile strength, and flexural strength increase to a certain extent. Through SEM analysis, it is found that SF restrains the development of cracks and improves the strength of concrete.

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