scholarly journals Utilization of Six Sigma in Quality Improvement of Recycled Aggregates Concrete

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Mohamad Terro ◽  
Moetaz El-Hawary ◽  
Rana Al-Fares ◽  
Mark Goldstein
Keyword(s):  
Process Improvement ◽  
Six Sigma ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Design Parameters ◽  
Established Method ◽  
Coarse Aggregates ◽  
Fine Aggregates

The use of recycled demolished concrete in producing new concrete is an established method to improve sustainability through reducing the environmental impact of using virgin aggregates and through reducing construction waste. Six sigma is a set of tools and strategies for process improvement. In this paper, the six sigma DMAIC methodology is utilized to optimize the design parameters in order to improve and assure the quality of the resulting recycled aggregate concrete. The project aims to produce concrete with compressive strength of 25 MPa without using additives. Five parameters were used in the initial analysis that were reduced to three after refinement. The refined parameters are the ratio of recycled coarse aggregates, the ratio of recycled fine aggregates, and the water/cement ratio. It was concluded that the optimum values for the three parameters are 26%, 30%, and 0.5, in order.

scholarly journals Effect of Design Parameters on Compressive and Split Tensile Strength of Self-Compacting Concrete with Recycled Aggregate: An Overview

2021 ◽  
Vol 11 (13) ◽  
pp. 6028
Author(s):  
P. Jagadesh ◽  
Andrés Juan-Valdés ◽  
M. Ignacio Guerra-Romero ◽  
Julia M. Morán-del Morán-del Pozo ◽  
Julia García-González ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Design Parameters ◽  
Fine Aggregate ◽  
Self Compacting Concrete ◽  
Split Tensile Strength ◽  
Coarse Aggregates ◽  
Fine Aggregates

One of the prime objectives of this review is to understand the role of design parameters on the mechanical properties (Compressive and split tensile strength) of Self-Compacting Concrete (SCC) with recycled aggregates (Recycled Coarse Aggregates (RCA) and Recycled Fine Aggregates (RFA)). The design parameters considered for review are Water to Cement (W/C) ratio, Water to Binder (W/B) ratio, Total Aggregates to Cement (TA/C) ratio, Fine Aggregate to Coarse Aggregate (FA/CA) ratio, Water to Solid (W/S) ratio in percentage, superplasticizer (SP) content (kg/cu.m), replacement percentage of RCA, and replacement percentage of RFA. It is observed that with respect to different grades of SCC, designed parameters affect the mechanical properties of SCC with recycled aggregates.

scholarly journals Quality of Recycled Aggregates and Compressive Strength of No-Fines Recycled-Aggregate Concrete

2021 ◽  
Vol 11 (5) ◽  
pp. 7641-7646
Author(s):  
S. A. Dahri ◽  
B. A. Memon ◽  
M. Oad ◽  
R. Bhanbhro ◽  
I. A. Rahu
Keyword(s):  
Compressive Strength ◽  
Testing Machine ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Sieve Analysis ◽  
Standard Size ◽  
Cement Ratio ◽  
Coarse Aggregates

This research paper presents the laboratory investigations of the compressive strength of no-fines concrete made with demolished waste as coarse aggregates used in percentages from 20% to 100%. The basic properties of aggregates were determined. Sieve analysis of both conventional and recycled aggregates was conducted to ensure the existence of well-graded aggregates in concrete. Nine concrete mixes were designed with an aggregate-cement ratio of 4. Additionally, three batches were prepared (conventional, recycled, conventional no-fines concrete) and the results were compared. For all mixes, the water-cement ratio was equal to 0.5. In each batch, 5 cylinders of standard size (total 60 samples) were prepared and cured for 28 days. The weight of the specimens was determined and compressive strength was checked in a Universal Testing Machine under gradually increasing load. A decrease in weight and compressive strength was recorded for the batches of the proposed concrete. Results show that at 40% replacement level the loss of compressive strength is 19% and the weight reduction of the samples was equal to 9%.

scholarly journals Sulfate Resistance of Recycled Aggregate Concrete with GGBS and Fly Ash-Based Geopolymer

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1247 ◽  
Author(s):  
Jianhe Xie ◽  
Jianbai Zhao ◽  
Junjie Wang ◽  
Chonghao Wang ◽  
Peiyan Huang ◽  
...  
Keyword(s):  
Fly Ash ◽  
Construction Projects ◽  
High Performance ◽  
High Performance Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Aggregate Concrete ◽  
Sulfate Resistance ◽  
Coarse Aggregates

There is a constant drive for the development of ultra-high-performance concrete using modern green engineering technologies. These concretes have to exhibit enhanced durability and incorporate energy-saving and environment-friendly functions. The object of this work was to develop a green concrete with an improved sulfate resistance. In this new type of concrete, recycled aggregates from construction and demolition (C&D) waste were used as coarse aggregates, and granulated blast furnace slag (GGBS) and fly ash-based geopolymer were used to totally replace the cement in concrete. This study focused on the sulfate resistance of this geopolymer recycled aggregate concrete (GRAC). A series of measurements including compression, X-ray diffraction (XRD), and scanning electron microscopy (SEM) tests were conducted to investigate the physical properties and hydration mechanisms of the GRAC after different exposure cycles in a sulfate environment. The results indicate that the GRAC with a higher content of GGBS had a lower mass loss and a higher residual compressive strength after the sulfate exposure. The proposed GRACs, showing an excellent sulfate resistance, can be used in construction projects in sulfate environments and hence can reduce the need for cement as well as the disposal of C&D wastes.

scholarly journals Quality Improvement of Recycled Aggregate Concrete using Six Sigma DMAIC Methodology

2020 ◽  
Vol 5 (6) ◽  
pp. 1409-1419
Author(s):  
Suhas Vijay Patil ◽  
Balakrishna Rao K. ◽  
Gopinatha Nayak
Keyword(s):  
Six Sigma ◽  
Coarse Aggregate ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Lower Grade ◽  
Test Results ◽  
Aggregate Concrete ◽  
Recycled Coarse Aggregate ◽  
Concrete Mix

Recycled aggregates (RA) are obtained from construction and demolished waste, laboratory crushed concrete and concrete waste at RMC plants. The concrete made from recycled aggregate is known as recycled aggregate concrete. The use of recycled aggregate is very beneficial to the environment in civil works. Its usage also helps in financial saving as the cost of transportation and production energy cost of natural coarse aggregate (NCA) is reduced. In India, the recycled aggregate application in lower grade concrete work is observed. However, the effect of recycled aggregate on the strength and durability of concrete restricts its use in higher-grade work. This paper presents a series of tests carried out on recycled coarse aggregate (RCA) and recycled coarse aggregate concrete (RCAC) and test results are compared with the NCA and parent concrete made from NCA. Tests were carried out as per IS code and concrete was prepared using a two-stage mixing approach in the concrete mix design. M30 concrete mix of four RCAC samples was tested at 28 days of curing and in comparison with parent concrete, it is found that on an average compressive strength is decreased by 12.89% at 28 days curing. Adhered mortar increases the porosity of the recycled aggregate and forms a weak zone between aggregate surface and mortar. In addition, test results showed the defects in recycled aggregate and helped to identify the area where concentration is necessary to improve the quality of recycled aggregate using six sigma DMAIC methodology. Total of 12 defects were found in the process and raw material. Statistical analysis was used to evaluate the performance of all the mix made with RCA.

On Properties of Recycled Coarse Aggregate from Repeatedly Recycling Waste Concrete

2011 ◽  
Vol 368-373 ◽  
pp. 2185-2188
Author(s):  
Ping Hua Zhu ◽  
Xin Jie Wang ◽  
Jin Cai Feng
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Fine Aggregate ◽  
Recycled Coarse Aggregate ◽  
Coarse Aggregates ◽  
Recycled Fine Aggregate ◽  
Waste Concrete

The properties of recycled coarsee aggregates from repeatedly recycling waste concrete were determined. In this study, five series of concrete mixtures using coarse and fine natural aggregates were prepared, which have the same objective slump value from 35mm to 50mm and different compressive strengths ranging from 25MPa to 60 MPa. These five concretes were crushed, sieved, washed with water, hot treatmented at 300°C before they were used as recycled aggregates. After that, recycled aggregate concrete (RAC) was produced with an objectively compressive strength of 30MPa, in which the recycled coarse aggregate was used as 30%, 70% and 90% replacements of natural coarse aggregate and recycled fine aggregate as 10%, 20%, and 30% replacements of natural fine aggregate. After that, these recycled concretes were used as second recycled aggregates to produce RAC with the same objectively compressive strength of 30MPa. The physical properties of coarse aggregates including apparent density, water absorption, attached mortar content and crushing value were tested and their mineral characteristics were analyzed. The results showed that the quality of recycled coarse aggregates from twicely recycling waste concrete reached the requirements from structural concrete.

scholarly journals Preliminary Analysis of the Use of Construction Waste to Replace Conventional Aggregates in Concrete

Buildings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 81
Author(s):  
Fernando A. N. Silva ◽  
João M. P. Q. Delgado ◽  
António C. Azevedo ◽  
António G. B. Lima ◽  
Castorina S. Vieira
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Recycled Aggregate Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Fine Aggregate ◽  
Demolition Waste ◽  
Fine Aggregates ◽  
Mechanical Strengths

This work aims to study the influence of using construction and demolition waste in the replacement of coarse and fine aggregate to produce recycled aggregate concrete (RAC). A moderate compressive strength concrete made with usual fine and coarse aggregate was used as a benchmark material. Compressive and split tensile tests were performed using 120 cylindrical concrete specimens with 150 mm diameter and 300 mm length. Four-point flexural tests in reinforced beams made with conventional concrete and RAC were performed. The results obtained showed that the use of recycled fine aggregates, in both percentages of substitution investigated—50% and 100%— did not generate any deleterious influence on the values of compressive strength and split tensile strength of the RACs produced. Tin fact, the mechanical strengths of RACs produced with recycled fine aggregate were equal or higher than those from the reference concrete. The same behavior was not observed, however, when the recycled coarse aggregate was used. For this case, decreases in concrete mechanical strengths were observed, especially in compressive strength, with values around 35% lower when compared to the reference concrete. Tensile mechanical tests results confirmed the excellent behavior of all RACs made with replacement of usual fine aggregates by recycled. Bending tests performed in reinforced RAC beams had as objective to evaluate the deformation profile of the beams. The obtained results showed that RAC beams with full replacement of usual fine aggregate by the recycled aggregates have presented little changes in the global behavior, an aspect that encourages its use.

scholarly journals Concrete produced with recycled aggregates

2012 ◽  
Vol 5 (5) ◽  
pp. 692-701 ◽  
Author(s):  
J. J. L. Tenório ◽  
P. C. C. Gomes ◽  
C. C. Rodrigues ◽  
T. F. F. de Alencar
Keyword(s):  
Coarse Aggregate ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Hardened Concrete ◽  
Specific Mass ◽  
River Sand ◽  
Recycled Coarse Aggregate ◽  
Coarse Aggregates ◽  
Natural Aggregates

This paper presents the analysis of the mechanical and durable properties of recycled aggregate concrete (RAC) for using in concrete. The porosity of recycled coarse aggregates is known to influence the fresh and hardened concrete properties and these properties are related to the specific mass of the recycled coarse aggregates, which directly influences the mechanical properties of the concrete. The recycled aggregates were obtained from construction and demolition wastes (CDW), which were divided into recycled sand (fine) and coarse aggregates. Besides this, a recycled coarse aggregate of a specific mass with a greater density was obtained by mixing the recycled aggregates of the CDW with the recycled aggregates of concrete wastes (CW). The concrete was produced in laboratory by combining three water-cement ratios, the ratios were used in agreement with NBR 6118 for structural concretes, with each recycled coarse aggregates and recycled sand or river sand, and the reference concrete was produced with natural aggregates. It was observed that recycled aggregates can be used in concrete with properties for structural concrete. In general, the use of recycled coarse aggregate in combination with recycled sand did not provide good results; but when the less porous was used, or the recycled coarse aggregate of a specific mass with a greater density, the properties of the concrete showed better results. Some RAC reached bigger strengths than the reference concrete.

scholarly journals Durability Indicators in High Absorption Recycled Aggregate Concrete

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Luis F. Jiménez ◽  
Eric I. Moreno
Keyword(s):  
Fluid Transport ◽  
Coarse Aggregate ◽  
Chloride Ion ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Concrete Mixtures ◽  
Concrete Production ◽  
High Absorption

The use of recycled aggregates in structural concrete production has the inconvenience of increasing the fluid transport properties, such as porosity, sorptivity, and permeability, which reduces the resistance against penetration of environmental loads such as carbon dioxide and chloride ion. In this paper, behavior of ten concrete mixtures with different percentages of coarse aggregate replacement was studied. The recycled material was recovered by crushing of concrete rubble and had high absorption values. The results showed that it is possible to achieve good resistance to carbonation and chloride penetration with up to 50% replacement of recycled coarse aggregate for 0.5 water/cement ratio. Finally, new indexes for porosity and sorptivity were proposed to assess the quality of concrete.

scholarly journals A Study of Concrete Made with Fine and Coarse Aggregates Recycled from Fresh Concrete Waste

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Mamery Sérifou ◽  
Z. M. Sbartaï ◽  
S. Yotte ◽  
M. O. Boffoué ◽  
E. Emeruwa ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fresh Concrete ◽  
Gradual Decrease ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Experimental Program ◽  
Coarse Aggregates ◽  
Concrete Properties ◽  
Fine Aggregates

This paper deals with the possibility of using fresh concrete waste as recycled aggregates in concrete. An experimental program based on two variables (proportion of fine aggregates replacement and proportion of coarse aggregates replacement) was implemented. The proportions of replacement were 0%, 50%, and 100% by mass of aggregates. Several mechanical properties were tested as compressive and tensile strengths. The results show a good correlation between aggregates replacement percentage and concrete properties. Concerning mechanical properties, a gradual decrease in compressive, splitting, and flexural strengthn with the increase in recycled aggregate percentage is shown.

scholarly journals Mechanical Properties of Basalt-Based Recycled Aggregate Concrete for Jeju Island

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5429
Author(s):  
Hong-Beom Choi ◽  
Jin-O Park ◽  
Tae-Hyun Kim ◽  
Kyeo-Re Lee
Keyword(s):  
Mechanical Performance ◽  
Drying Shrinkage ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Superior Performance ◽  
Recycled Aggregates ◽  
Replacement Ratio ◽  
Volume Percentage ◽  
Air Content

Recycled aggregate is essential to protect Jeju Island’s natural environment, but waste concrete, including porous basalt, is a factor that lowers the quality of recycled aggregate. Therefore, an experiment was conducted to analyze the properties of concrete application of basalt-based recycled aggregate (B-RA) through quality improvement. The absorption of the B-RA ranged from 3–5%; restricting its absorption to less than 3% was challenging owing to its porosity and irregular shape. However, the increase in the solid volume percentage of the concrete when replacing 25 or 50% of fresh basalt aggregate with recycled basalt aggregate improved the mechanical performance of the concrete, especially at 25%, for which a compressive strength of 55.9 MPa and modulus of elasticity of 25.9 GPa exceeded those of concrete with fresh basalt aggregate. Moreover, increasing the replacement ratio of the fresh basalt with recycled aggregate reduced the slump and decreased the air content, consequently increasing the concrete drying shrinkage. However, the replacement of fresh basalt aggregate with recycled basalt aggregate unaltered the mechanical performance of the concrete. The results indicate that efficient use of recycled aggregates can yield superior performance to that of fresh basalt, irrespective of aggregate quality.

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