scholarly journals Effects of Recycled Fine Aggregates and Inorganic Crystalline Materials on the Strength and Pore Structures of Cement-Based Composites

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 587
Author(s):  
Sung-Ching Chen ◽  
Si-Yu Zou ◽  
Hui-Mi Hsu
Keyword(s):  
Internal Structure ◽  
Total Charge ◽  
Hydration Products ◽  
Crystalline Materials ◽  
Concrete Mixtures ◽  
Fine Aggregates ◽  
Binder Ratio ◽  
Harmful Substances ◽  
Natural Aggregates ◽  
Secondary Hydration

Concrete is porous; the partial pores in the internal structure of concrete are generated by hydration products, such as calcium hydroxide, dissolved in water. External harmful substances in the form of gases or aqueous solutions can penetrate concrete. The destruction of the internal structure of concrete leads to problems such as shortening of the service life of concrete as well as the corrosion and poor durability of steel. To improve the pore structure of concrete, a material can be added to concrete mixtures to cause the secondary hydration of the hydration products of cement. This reaction is expected to reduce the pore volume and increase the density of concrete. For existing concrete structures, inorganic crystalline materials can be used to protect the surface and reduce the intrusion of external harmful substances. In this study, the water–binder ratio was 0.4 and 0.6. Three inorganic crystalline materials and recycled fine aggregates (0%, 10%, 20%, and 30% replacement of natural aggregates by weight) were used in the same cement-based composites. The results indicated that all specimens had a high total charge-passed value, and inorganic crystalline material C provided superior protection for green cement-based composites.

Research in the Preparation of Paving Bricks with Construction Garbage

2013 ◽  
Vol 712-715 ◽  
pp. 917-920
Author(s):  
Lian Xi Wang ◽  
Guang Hui Pan ◽  
Fu Yong Li ◽  
Hai Ming Wang ◽  
Guo Zhong Li
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Experimental Results ◽  
Replacement Rate ◽  
Coarse Aggregates ◽  
Waste Concrete ◽  
Fine Aggregates ◽  
Binder Ratio ◽  
Water Binder Ratio

Construction garbage paving bricks were made of recycled coarse and fine aggregates which were prepared by the waste concrete. The influence of replacement rate of recycled coarse aggregates, water-binder ratio and excitation agent dosage on the compressive strength and flexural strength of construction garbage paving bricks were researched. The experimental results show that optimum replacement rate of recycled coarse aggregates, water-binder ratio and excitation agent dosage were 100%, 0.43 and 1.5% respectively. In this proportion, the 7d, 28d compressive strength of the products were 15.6MPa, 37.5MPa respectively, and the 7d, 28d flexural strength were 2.0MPa, 4.3MPa respectively, which fit the requirements of the Cc30 level of compressive strength and the Cf4.0 level of flexural strength involved in JCT 446-2000 "concrete pavers".

Influence de la température minimale du cycle de gel–dégel sur la détérioration du béton par écaillage en présence de sels fondants

1996 ◽  
Vol 23 (3) ◽  
pp. 595-601
Author(s):  
J. Marchand ◽  
M. Pigeon ◽  
L. Boisvert
Keyword(s):  
Test Procedure ◽  
Air Entrainment ◽  
Freezing Temperature ◽  
Freezing And Thawing ◽  
Concrete Mixtures ◽  
Conditioning Period ◽  
Binder Ratio ◽  
Freezing Cycle ◽  
Air Void ◽  
Scaling Resistance

Eight different concrete mixtures were prepared to investigate the influence of the minimum temperature of the freezing and thawing cycle on scaling deterioration due to deicer salt. In addition to the two minimum temperatures studied (−18 and −9 °C), test variables included the type of binder (with or without silica fume), the water/binder ratio (0.35 or 0.45), the characteristics of the air-void network (with or without air entrainment), and the drying temperature during the conditioning period prior to the scaling test (20, 40, or 110 °C). The scaling resistance to deicer salt of all concrete mixtures was assessed according to the prescriptions of the ASTM C672 test procedure using a 3 % NaCl solution. Test results indicate that a reduction of the minimal temperature from −9 to −18 °C significantly increases the scaling deterioration of concrete due to deicer salt. Key words: freezing cycle, scaling resistance, minimal freezing temperature, deicer salts.

Leaching behaviour of municipal solid waste incineration bottom ash: From granular material to monolithic concrete

2017 ◽  
Vol 35 (9) ◽  
pp. 978-990 ◽  
Author(s):  
Sabrina Sorlini ◽  
Maria Cristina Collivignarelli ◽  
Alessandro Abbà
Keyword(s):  
Municipal Solid Waste ◽  
Solid Waste ◽  
Bottom Ash ◽  
Waste Incineration ◽  
Municipal Solid Waste Incineration ◽  
Concrete Mixtures ◽  
Concrete Production ◽  
Critical Issues ◽  
Leaching Behaviour ◽  
Natural Aggregates

The aim of this work was to assess the leaching behaviour of the bottom ash derived from municipal solid waste incineration (MSWI) used in concrete production. In particular, the release of pollutants was evaluated by the application of different leaching tests, both on granular materials and monolithic samples (concrete mixtures cast with bottom ash). The results confirmed that, according to Italian regulations, unwashed bottom ashes present critical issues for the use as alternative aggregates in the construction sector due to the excessive release of pollutants; instead, the leachate from washed bottom ashes was similar to natural aggregates. The concentration of pollutants in the leachate from concrete mixtures was lower than regulation limits for reuse. The crushing process significantly influenced the release of pollutants: this behaviour was due both to the increase in surface area and the release of contaminants from cement. Moreover, the increase in contact time (up to 64 days) involved more heavy metals to be released.

Influence of Artificial Aggregates on the ITZ's Microstructure of Recycling Concrete

2013 ◽  
Vol 743-744 ◽  
pp. 180-185
Author(s):  
Jun Hua Zhang ◽  
Zong Hui Zhou ◽  
De Cheng Zhang ◽  
Xin Cheng
Keyword(s):  
Fly Ash ◽  
Mineral Composition ◽  
High Performance ◽  
Raw Materials ◽  
Steel Slag ◽  
Interfacial Transition Zone ◽  
Hydration Products ◽  
Ordinary Concrete ◽  
Natural Aggregates ◽  
Furnace Slag

Artificial aggregates with high-performance were prepared by the methods including steel slag, furnace slag, fly ash and coal gangue, and the recycling concrete was prepared by artificial aggregates instead of natural aggregates. This kind of concrete abandoned was able to completely regenerate cement, which will make the reuse of concrete possible. The composition and characteristics of the artificial aggregates will produce a significant effect on the interfacial transition zone (ITZ) in recycling concrete. The morphological features and mineral composition of three artificial aggregates were analyzed by SEM and XRD, and the ITZ of three recycling concrete and one ordinary concrete was investigated by SEM and EDS. The results showed that compared with ordinary concrete, although the recycling concretes ITZ had a small amount of CH crystal, most of the space was filled with dense hydration products. The interface width was 40μm, which less than 50μm of ordinary concrete. Artificial aggregates with different ratio of raw materials had a great effect on recycling concretes ITZ. The ITZ of recycling concrete prepared with 30% steel slag, 50% furnace slag, 20% fly ash had the smallest Ca/Si and much more C-S-H. the structure of ITZ was much denser and the microstructure was relatively better.

Image Analysis Evaluation of Aggregates for Asphalt Concrete Mixtures

1998 ◽  
Vol 1615 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Chun-Yi Kuo ◽  
Reed B. Freeman
Keyword(s):  
Image Analysis ◽  
Asphalt Concrete ◽  
Morphological Characteristics ◽  
Engineering Properties ◽  
Natural Sand ◽  
Coarse Aggregates ◽  
Concrete Mixtures ◽  
Fine Aggregates ◽  
Pavement Engineering ◽  
Recent Developments

The performance of asphalt concrete mixtures is influenced by the properties of the included aggregates, such as grading, shape (angularity and elongation), and texture (roughness). Complete and accurate quantification of aggregate properties is essential for understanding their influence on asphalt concrete and for selecting aggregates to produce high-quality paving mixtures. Recent developments in the use of digital image analysis techniques for quantifying aggregate morphological characteristics in asphalt concrete are summarized. Image morphological characteristics were used to quantify flatness and elongation of coarse aggregates, to estimate the proportion of natural sand in fine aggregates, and to correlate aggregate characteristics with engineering properties of asphalt concrete mixtures. Image analysis of sections also revealed information about the grading, shape, and orientation of coarse aggregates in a mixture. An overview is presented of the broad range of useful pavement engineering applications of this relatively new approach for evaluating aggregate characteristics.

Quality Evaluation System for Description of Recycled Concrete Aggregates and Verification of its Functionality

2017 ◽  
Vol 902 ◽  
pp. 14-19 ◽  
Author(s):  
Iveta Nováková ◽  
Iveta Hájková
Keyword(s):  
Evaluation System ◽  
Quality Evaluation ◽  
Recycled Concrete ◽  
Demolition Waste ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Concrete Mixtures ◽  
Natural Aggregates ◽  
Set Up ◽  
Quality Evaluation System

Article presents quality evaluation system for description of recycled concrete aggregates (RCA), verification of RCA properties and subsequent application in to concrete mixtures as a partial or total replacement of natural aggregates (NA). Modernization and rehabilitation of constructions is accompanied by creation of demolition waste from old buildings and structures. The necessity of recycling is unavoidable, because volume of construction and demolition waste (C&DW) is increasing and the landfills are reaching their maximum capacity. Nowadays, there are numerous research teams focused on analysis of characteristics and application of RCA into new concrete as a replacement of NA. Test samples of RCA have always different source, grain composition and other physical and mechanical properties, which are variously described in each different paper. Up to now, there is no any uniform quality evaluation system for description of recycled concrete aggregates, which can easily describe their source and assumed properties. Our aim is to set up rules for description of RCA and simplify the evaluation of properties of various RCA. Qualification system will be applied on three different samples of RCA and verified by the selected properties tests. Tested samples of RCA will be than used as a replacement of natural aggregates in concrete mixtures. The replacement amount was set up on 20%, 40% and 100% according to the reviewed literature, to have a comparable replacement amount and valuable results for discussion. The results of RCA testing and testing of concrete with partial and total replacement of NA showed that the evaluation system is working properly. It can be concluded, that accuracy of the quality evaluation system for description of recycled concrete aggregates is sufficient, but more tests on RCA should be done to prove all connections in between description of RCA and their properties.

scholarly journals KARAKTERISTIK MEKANIS BETON YANG MENGGUNAKAN IRON SLAG SEBAGAI AGREGAT HALUS

2020 ◽  
Vol 20 (3) ◽  
pp. 223-230
Author(s):  
Hijriah ◽  
Nur Hadijah Yunianti
Keyword(s):  
Test Object ◽  
Environmentally Friendly ◽  
Fine Aggregate ◽  
Iron Slag ◽  
Concrete Mixtures ◽  
Fine Aggregates ◽  
Materials Used ◽  
Slag Waste ◽  
Test Objects ◽  
Research Analysis

The demand for environmentally friendly concrete mixtures is currently increasing due to an increase in global temperatures. Therefore, innovation is needed in the world of Civil Engineering to produce structures that can reduce global warming. One alternative that can be taken is by utilizing materials from environmentally friendly products such as Iron Slag. This study aims to determine the characteristics of the aggregate and to analyze the strength of the concrete mixture using Iron Slag as a substitute for fine aggregate. This research is an experimental study which was conducted in the Laboratory of Concrete and Structural Materials, Bosowa University. Variations in the test object were the levels of addition of Iron Slag with levels of 0%, 25% and 50%. The test object will be observed at the age of 28 days, where the number of test objects is 29 pieces. The tests carried out include testing the characteristics of the materials used, both coarse and fine aggregates, as well as testing the compressive strength of the concrete. Based on the results of the research analysis, it was concluded that Iron Slag waste met the criteria as fine aggregate for concrete mixtures.

scholarly journals Polyethylene Terephthalate (PET) Bottles Waste as Fine Aggregate in Concrete

2019 ◽  
Vol 8 (6S4) ◽  
Keyword(s):  
Natural Resources ◽  
Polyethylene Terephthalate ◽  
Construction Material ◽  
Fine Aggregate ◽  
River Sand ◽  
Recycled Pet ◽  
Pet Bottles ◽  
Fine Aggregates ◽  
New Construction ◽  
Natural Aggregates

Concrete construction industry is one of the major sector utilizing natural resources to produce concrete for building constructions. The rapid increase in building constructions and the demand for natural aggregates has resulted in depletion natural resources at an alarming rate. Uncontrolled mining activity worsens the situation. Thus serious awareness has been taken into consideration, has to be identified as a potential river sand substitution for fine aggregates replacement in concrete. For this review, utilizing recycled material are described as a fine aggregate replacement to river sand, particularly recycled Polyethylene Terephthalate (PET) bottles. Recycled PET Bottles are categorized as nonbiodegradable waste materials which are injurious to health. Recycled PET bottles in concrete are economical and help in reducing disposal problems. Recycled PET bottles are pondered as the best eco-friendly alternative not only for resolving the problem of disposal but as a new construction material for concrete

scholarly journals Empirical relationships between compressive and flexural strength of concrete containing recycled asphalt material for pavement applications using different specimen configurations

2021 ◽  
Vol 71 (342) ◽  
pp. e249
Author(s):  
C.R. Marín-Uribe ◽  
R. Navarro-Gaete
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Prediction Models ◽  
Reclaimed Asphalt Pavement ◽  
Empirical Relationships ◽  
Recycled Asphalt ◽  
Reclaimed Asphalt ◽  
Concrete Mixtures ◽  
Power Models ◽  
Natural Aggregates

The flexural strength of pavement concrete is generally deduced by testing beams or by applying empirical equations. In this investigation, concrete mixtures were manufactured, incorporating 0, 20, 50 and 100% Reclaimed Asphalt Pavement (RAP), by weight, as a replacement for natural aggregates. The compressive strength was measured using cubic specimens and the flexural strength was measured for three types of specimens; beam, semicircular (SCB) and modified beam. This study proposes logarithmic and power equations that allow the estimation of the flexural strength of a concrete mix that incorporates RAP as a function of its compressive strength. Linear or power models are proposed to predict beam flexural strength from SCB specimens and a logarithmic model for modified beam specimens. Statistical analyses show that the proposed prediction models can be considered sufficiently accurate and their use is justified.

scholarly journals Effect of Nano-CaCO3 on the Mechanical Properties and Durability of Concrete Incorporating Fly Ash

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yanqun Sun ◽  
Peng Zhang ◽  
Weina Guo ◽  
Jiuwen Bao ◽  
Chengping Qu
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Second Phase ◽  
Fly Ash Concrete ◽  
Concrete Mixtures ◽  
Orthogonal Experiments ◽  
Mix Proportion ◽  
Electron Microscopy Analysis ◽  
Binder Ratio ◽  
Durability Of Concrete

Concrete mixtures consisting of nanomaterials and fly ash have been shown to be effective for improving the performance of concrete. This study investigates the combined effects of nano-CaCO3 and fly ash on the mechanical properties and durability of concrete; the mix proportion is optimized through orthogonal experiments. In the first phase, nine concrete mixtures were prepared with three water-to-binder ratios (0.4, 0.5, and 0.6), three fly ash contents (15%, 20%, and 25% replacement of the cement weight), and three nano-CaCO3 contents (1%, 2%, and 3% replacement of the cement weight). Based on the orthogonal analysis, the optimal concrete mix proportion was determined as a water-to-binder ratio of 0.4, 20% fly ash, and 1% nano-CaCO3. In the second phase, further investigations were carried out to examine the superiority of the optimal concrete and evaluate the synergistic effect of nano-CaCO3 and fly ash. The results showed that nano-CaCO3 contributed to increasing the compressive strength of fly ash concrete at the early ages, but its effect was quite limited at later ages. Furthermore, the scanning electron microscopy analysis revealed that the seeding effect, filling effect, and pozzolanic effect were the primary mechanisms for the improvement of concrete performance.

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