scholarly journals Behavior of Various Concrete Mixes with Inclusion of Recycled Coarse Aggregates Based on Durability Point of View

2020 ◽  
Vol 9 (3) ◽  
pp. 817-823
Keyword(s):  
Construction Material ◽  
Concrete Structures ◽  
Recycled Aggregates ◽  
Effect Of Temperature ◽  
Partial Replacement ◽  
Cement Concrete ◽  
Thermal Cycles ◽  
Temperature Variations ◽  
Chemical Attack ◽  
Natural Aggregates

Cement concrete is the most extensively used construction material in the world with about six billion tons produced every year. It has emerged as the dominant construction material for the infrastructure needs of the 21st century. Aggregate is one of the main ingredients in producing concrete i.e. 75% of the concrete mass. The strength of the concrete produced is dependent on the properties of aggregates used, hence there is huge demand for this material. In order to reduce the use of natural aggregates from natural resources, the use of recycled aggregates in concretes is an interesting solution. It helps in reducing the cost of concrete manufacturing and also has numerous indirect benefits such as reduction in land-fill cost, energy saving, and protecting the environment from possible pollution effects. Durability and strength are two most important criteria for any concrete structures. One of the main causes of deterioration in concrete structures is its exposure to temperature variations mainly due to solar radiation and harmful chemicals that may be found in nature such as in industrial effluents. The most aggressive chemicals that affect the long term durability of concrete structures are the magnesium, sulphates and chlorides. These chemicals in presence of water increases the porosity of concrete and leads to loss of weight and strength. Hence this paper investigates the effect of thermal cycles and chemical attack on M20 & M25 grade cement concrete in partial replacement of natural aggregates with recycled aggregates with proportion of 10%, 20% and 30%. The effect of temperature variations were studied by analyzing loss in compressive strength after applying various thermal cycles on concrete cubes at 60o C and 90 o C. The chemical resistance of the concretes was studied through chemical attack by immersing concrete cubes in 5% MgSO4 , H2SO4 and HCl solution and loss in strength and weight were measured at 7, 28, 60 and 90 days. The result shows possible use of RCA as 20% for both M20 & M25 grade concrete, and resistance to thermal cycles and chemical attack shows reduction in strength and weight with time

Mechanism of Cement Paste with Different Particle Sizes of Bottom Ash as Partial Replacement in Portland Cement

2017 ◽  
Vol 68 (10) ◽  
pp. 2367-2372 ◽  
Author(s):  
Ng Hooi Jun ◽  
Mirabela Georgiana Minciuna ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Tan Soo Jin ◽  
Andrei Victor Sandu ◽  
...  
Keyword(s):  
Portland Cement ◽  
Construction Material ◽  
Bottom Ash ◽  
High Volume ◽  
Cement Composite ◽  
Pozzolanic Reaction ◽  
High Specific Surface Area ◽  
Partial Replacement ◽  
Natural Aggregates ◽  
Pozzolanic Properties

Manufacturing of Portland cement consists of high volume of natural aggregates which depleted rapidly in today construction field. New substitutable material such as bottom ash replace and target for comparable properties with hydraulic or pozzolanic properties as Portland cement. This study investigates the replacement of different sizes of bottom ash into Portland cement by reducing the content of Portland cement and examined the mechanism between bottom ash (BA) and Portland cement. A cement composite developed by 10% replacement with 1, 7, 14, and 28 days of curing and exhibited excellent mechanical strength on day 28 (34.23 MPa) with 63 mm BA. The porous structure of BA results in lower density as the fineness particles size contains high specific surface area and consume high quantity of water. The morphology, mineralogical, and ternary phase analysis showed that pozzolanic reaction of bottom ash does not alter but complements and integrates the cement hydration process which facilitate effectively the potential of bottom ash to act as construction material.

scholarly journals Effect of Fibers on the Bond Behavior of Deformed Steel Bar Embedded in Recycled Aggregate Concrete

2020 ◽  
Vol 39 (4) ◽  
pp. 846-858
Author(s):  
Rashid Hameed ◽  
Usman Akmal ◽  
Qasim S. Khan ◽  
Muhammad Ahsan Cheema ◽  
Muhammad Rizwan Riaz
Keyword(s):  
Compressive Strength ◽  
Concrete Structures ◽  
Steel Fibers ◽  
Recycled Aggregates ◽  
Polypropylene Fibers ◽  
Reinforcing Bars ◽  
Bond Behavior ◽  
Pull Out ◽  
Steel Bar ◽  
Natural Aggregates

A large volume of concrete debris is being produced in many countries on the globe due to the demolition of old concrete structures and testing of concrete specimens in laboratories. One of the ways to reuse concrete debris is to produce Recycled Aggregates (RA) and use them in new concrete. In recent years, Recycled Aggregates Concrete (RAC) has experienced increasing demand in various non-structural and structural applications. In reinforced concrete structures, one of the sources of brittle failure is sudden loss of bond between reinforcing bars and concrete in anchorage zones. Therefore, for the structural application of any new kind of concrete such as fiber reinforced RAC, knowledge of bond characteristics of reinforcing bars embedded in concrete becomes essential for determining the overall structural response under different modes of loading. In this regard, this study experimentally investigated the effect of fibers on the bond stress-slip behavior of deformed steel re-bar embedded in RAC. Concrete mixes having 0, 50 and 100% RAs were prepared with and without the addition of fibers. Two types of fibers were investigated in mono form: hooked-ends steel and polypropylene fibers. The dosage of steel and polypropylene fibers was kept 40 and 4.4 kg/m3, respectively. Axial compression and standard pull-out tests were performed. Test specimens for pull-out test were prepared using deformed steel re-bars of 19mm (#6) diameter. The results of strength tests confirmed that the compressive strength of concrete is decreased by replacing Natural Aggregates (NA) with RAs. For bond behavior of steel re-bar, the results of this study showed that replacement of 50% NA with RAs did not affect the bond response of steel bar, however, 100% replacement of NA with RAs showed detrimental effect on bond stress slip behavior. The results further showed that the addition of both types of fibers made it possible to recover the loss in compressive strength, bond strengths and bond toughness occurred because of replacing NA with RAs. In case of RA concrete mixes containing hooked-ends steel fibers, strength values were found even greater than the strength values of Natural Aggregates Concrete (NAC). From the results of this study, it was found that it is possible to design a structural concrete mix using 100% RAs and steel fibers at relatively low dosage of 40kg/m3.

scholarly journals Utilization of Iraqi Metakaolin in Special Types of Concrete: A Review Based on National Researches

2021 ◽  
Vol 27 (8) ◽  
pp. 80-98
Author(s):  
Mahmood Fawzi Ahmed
Keyword(s):  
Construction Material ◽  
Cementitious Materials ◽  
Pozzolanic Reaction ◽  
Supplementary Cementitious Materials ◽  
Partial Replacement ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Concrete Technology ◽  
Natural Pozzolans ◽  
Sustainability Issue

Portland cement concrete is the most commonly used construction material in the world for decades. However, the searches in concrete technology are remaining growing to meet particular properties related to its strength, durability, and sustainability issue. Thus, several types of concrete have been developed to enhance concrete performance. Most of the modern concrete types have to contain supplementary cementitious materials (SCMs) as a partial replacement of cement. These materials are either by-products of waste such as fly ash, slag, rice husk ash, and silica fume or from a geological resource like natural pozzolans and metakaolin (MK). Ideally, the utilization of SCMs will enhance the concrete performance, minimize environmental pollution and mitigate the drawbacks of cement production attributed to the highly CO2 emission. In general, MK's ultra-fineness and high pozzolanic activity are exhibited a remarkable performance of concrete in terms of strength and durability. However, the filler effect, acceleration of cement hydration, and the pozzolanic reaction with calcium hydroxide (CH) are the main factors influencing the performance of metakaolin as a cementitious material. Therefore, numerous researches have been undertaken on inclusion MK in concrete and mortar and production of (free-cement concrete) geopolymer concrete. This paper reviews some of previous native researches on effect of using Iraqi metakaolin as a pozzolanic material in different types of concrete. The standpoint of this review will guide the researchers on the importance of utilization of local MK and highlight the missing researches toward completing a comprehensive understanding of incorporation Iraqi-metakaolin in concrete technology.

Production of Concrete Blocks with Residues for Civil Construction

2013 ◽  
Vol 690-693 ◽  
pp. 865-869 ◽  
Author(s):  
Marília Martinês de Camargo ◽  
Rosa Cristina Cecche Lintz ◽  
Luisa Andréia Gachet-Barbosa ◽  
Marta Siviero Guilherme Pires
Keyword(s):  
Value Added ◽  
Construction And Demolition Waste ◽  
Recycled Aggregates ◽  
Partial Replacement ◽  
Structural Function ◽  
Demolition Waste ◽  
Original Product ◽  
Concrete Blocks ◽  
Function Blocks ◽  
Natural Aggregates

The Construction is recognized as one of the most important activities for the economic and social development, and on the other hand, behaves also as a major generator of environmental impacts, either by consumption of natural resources, the modification of the landscape or the generation of construction and demolition waste (CDW). Investing in an implementation of managed clean and healthy in the area of CDW is essential for the environment and for the economy of the cities, who are spending less resources on the collection, cleaning of drains and treatment of diseases. Nowadays, the amount of waste generated is considered large, occupying much space in landfills, and its transportation, depending on the volume and weight, is quite expensive. Recycling and reuse of these wastes are extremely important to control and mitigate environmental problems, as well as produce various materials value-added. Over 90% of waste can be recycled, reused and transformed into aggregates with characteristics very similar to the original product, thus creating environmentally friendly products such as sand, gravel, pebbles. This research concerns the study of the properties of concrete containing CDW, aiming its use in the manufacture of concrete blocks to seal without structural function. Blocks have been molded with partial replacement of natural aggregates by recycled aggregates and later were performed tests of compressive strength in accordance with the standards to prove the technical feasibility of the material for the trait studied.

scholarly journals Influence of Elevated Temperature on Concrete Properties Containing Natural Wastes Treated by Pyrolysis

2020 ◽  
pp. 1-15
Author(s):  
Manal M. Farag ◽  
Magdy El- Yamany ◽  
A. S. Faried ◽  
W. H. Sofi
Keyword(s):  
Natural Fiber ◽  
Construction Material ◽  
Natural Fibers ◽  
Construction Materials ◽  
Effect Of Temperature ◽  
Modern Concept ◽  
Cement Concrete ◽  
Plant Fibers ◽  
Waste Products ◽  
Optimum Result

Concrete is probably the most extensively used construction material in the world. The modern concept of construction is directed at the use of recycled materials, in particular, various waste products. This solves a number of problems -saving the expensive materials; - decreasing CO2 emissions by reducing the production of construction materials, so, these can also be used as refractory materials. Plant fibers are the most abundant fiber among all the natural fibers. Bamboo, palm, sisal, jute, date kernel, flax etc. are the commonly known plant fibers. Plant fibers are also called cellulosic fiber and have quite promising tensile strength. Natural Plant fibers treated by pyrolysis in concrete such as additions; determine the effect of these substances and the effect of temperature on the properties of concrete. The natural fibers in concrete are added accordingly with the percentage of 0.5%, 1%, 1.5% and 2% by weight of cement concrete cubes are tested at the age of 7 and 28 days of curing. Natural waste treated by pyrolysis and different additives on concrete behavior to improve its performance in the future to use in Civil Engineering and Construction World. The optimum result for natural fibers was observed at 1.0% for bamboo and date kernel and 1.5% for palm oil of natural fiber.

scholarly journals Recycled Aggregates Produced from Construction and Demolition Waste for Structural Concrete: Constituents, Properties and Production

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5748
Author(s):  
João Pacheco ◽  
Jorge de Brito
Keyword(s):  
Construction Material ◽  
Mineral Resources ◽  
Heterogeneous Material ◽  
Recycled Aggregate Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Demolition Waste ◽  
Adequate Quality ◽  
Natural Aggregates

This paper concerns the recovery of construction and demolition waste as coarse recycled aggregates for concrete. Coarse recycled aggregates may be used as a partial or total replacement of natural aggregates, contributing to the circular economy and minimizing landfill disposals as well as the consumption of natural mineral resources. However, construction and demolition waste is a heterogeneous material with undefined quality and the processing of this waste into recycled aggregates needs to ensure that the recycled aggregates have suitable properties for concrete. This paper summarizes several aspects related to coarse recycled aggregates, specifically addressing: (i) the typical composition of construction and demolition waste; (ii) the influence of different types of constituents on the properties of recycled aggregates and recycled aggregate concrete; (iii) requirements for recycled aggregates to be used in concrete; and (iv) production methods of recycled aggregates. It is argued that coarse recycled aggregates are a suitable construction material with adequate quality, even when common equipment is used in their production and preliminary separation as a key operation for ensuring the quality of the aggregates is recommended.

scholarly journals Influence of Pozzolan, Slag and Recycled Aggregates on the Mechanical and Durability Properties of Low Cement Concrete

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4173
Author(s):  
Eliana Soldado ◽  
Ana Antunes ◽  
Hugo Costa ◽  
Ricardo do do Carmo ◽  
Eduardo Júlio
Keyword(s):  
Fly Ash ◽  
Mechanical Performance ◽  
Concrete Surface ◽  
Recycled Aggregates ◽  
Partial Replacement ◽  
Natural Pozzolans ◽  
Durability Properties ◽  
Chloride Attack ◽  
Natural Aggregates ◽  
Reduction Of Co2

The sustainability of the construction sector demands the reduction of CO2 emissions. The optimization of the amount of cement in concrete can be achieved either by partially replacing it by additions or by reducing the binder content. The present work aims at optimizing the properties of concrete used in the production of reinforced concrete poles for electrical distribution lines, combining the maximization of compactness with the partial replacement of cement by fly ash, natural pozzolans, and electric furnace slags. Natural aggregates were also partially replaced by recycled ones in mixtures with fly ash. Two types of concrete were studied: a fresh molded one with a dry consistency and a formwork molded one with a plastic consistency. The following properties were characterized: mechanical properties (flexural, tensile splitting, and compressive strengths, as well as Young’s modulus) and durability properties (capillary water absorption, water penetration depth under pressure, resistance to carbonation, chloride migration, and concrete surface resistivity). The service life of structures was estimated, taking the deterioration of reinforcement induced by concrete carbonation or chloride attack into account. Results revealed that mixtures with fly ash exhibit higher mechanical performance and mixtures with fly ash or pozzolans reveal much higher durability results than the full Portland cement-based mixtures.

Possibilities of Recycled Concrete Aggregate in Cement-Based Flowscreed

2014 ◽  
Vol 897 ◽  
pp. 247-251
Author(s):  
Adam Hubáček ◽  
Luc Boehme ◽  
Iveta Nováková
Keyword(s):  
Mechanical Properties ◽  
Recycled Concrete ◽  
Experimental Results ◽  
Recycled Aggregates ◽  
Partial Replacement ◽  
Concrete Aggregate ◽  
Rheological Characteristics ◽  
Test Results ◽  
Recycled Concrete Aggregate ◽  
Natural Aggregates

This paper presents some test-results of using fine recycled concrete as a partial replacement of natural aggregates in cement-based flowscreed. Special attention is given to describing and studying rheological characteristics and mechanical properties of cement-based flowscreed. Experimental results indicate that it is possible to prepare flowscreed with partial replacement of natural aggregates by recycled aggregates and obtain a quality that meets the requirements. This study was partially connected to the research-project RecyFlowscreed [1].

scholarly journals Bottom Ash based Steel Fiber Reinforced Concrete

2020 ◽  
Vol 8 (6) ◽  
pp. 5459-5463
Keyword(s):  
Reinforced Concrete ◽  
Steel Fiber ◽  
Construction Material ◽  
Bottom Ash ◽  
Fiber Reinforced Concrete ◽  
Recycled Aggregates ◽  
Fine Aggregate ◽  
Fiber Reinforced ◽  
Steel Fiber Reinforced Concrete ◽  
Natural Aggregates

Concrete is the most significant material for construction and by incorporation of various industrial by products may improve its properties. Normally fine aggregates have been obtained from natural sources like river beds, now days there is a lot of scarcity for getting natural aggregates. So to overcome this problem, aggregates are partially replaced with alternative materials like bottom ash, recycled aggregates and some natural aggregates .In present study, fine aggregate was replaced with bottom ash and steel fibres are used to improve strength characteristics of concrete. M25 grade concrete was prepared for control specimens, and also bottom ash based fiber reinforced concrete specimens were prepared in different proportions 0%, 10%, 20%, 30% and 40% with bottom ash by weight of fine aggregate and a 1.0% and 1.5% of steel fibers were added by weight of cement. To examine bottom ash based steel fiber reinforced concrete specimens were tested under flexural, split tensile, and compression. The mechanical property of bottom ash based steel fiber reinforced concrete was compared with control mix to examine optimal combination of bottom ash and fibers. It was noticed that 10% replacement of bottom ash has shown the maximum improvement in Compressive, split tensile and flexural strength. Hence, bottom ash based steel fiber reinforced concrete can be used as construction material.

scholarly journals Study of the Compressive Strength of Concrete with Partial Replacement of Recycled Coarse Aggregates

2021 ◽  
Vol 11 (3) ◽  
pp. 7191-7194
Author(s):  
X. H. Vu ◽  
T. C. Vo ◽  
V. T. Phan
Keyword(s):  
Compressive Strength ◽  
Recycled Aggregate ◽  
Concrete Mixture ◽  
Recycled Aggregates ◽  
Partial Replacement ◽  
Replacement Rate ◽  
Coarse Aggregates ◽  
Compressive Strength Of Concrete ◽  
Natural Aggregates

This paper presents a study on the compressive strength of concrete using recycled aggregates. The concrete was designed to have a 25MPa compressive strength and an 8cm slump. The rates of replacing natural aggregates with recycled coarse were 0%, 10%, and 20%. The test samples were compressed to determine their compressive strength value after 7, 14, and 28 days of curing. The results showed that the concrete slump did not change effectively at a 10% replacement rate. When using 20% recycled aggregates, the concrete was too hard and the homogeneity of the concrete mixture could not be guaranteed. The compressive strength slightly decreased using 10% of recycled aggregates and decreased significantly using 20%. Therefore, 20% of recycled aggregate replacement is not suitable. The results showed that using recycled aggregates at a rate of 10% is optimal.

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