R. Preetha, GVVSR Kishore, Scientific Officer, C. S Pillai, Associate Director, Indira Gandhi Centre For Atomic Research, A. K. Laharia, ADDL. Chief Engineer(c), M. Umashankar, Engineer in Charge Quality Assurance Civil, Nuclear Power Corporation Ltd.

General

Fly ash is a good pozzolanic mineral admixture, which can replace large quantity of cement in the concrete. The positive effects of using fly ash in concrete are better quality of concrete, eco-friendly and preservation of resources. Construction of power plants require huge quantity of concrete and use of fly ash, as pozzolanic material, can improve the durability of structure, thereby enhancing the safety of plants and also economy in the life cycle cost of the plant.

Properties of concrete whether strength or durability depends on constituents, mixing, placing, compaction, curing etc. To get a holistic view on behavior of flyash concrete to be used in major construction of safety structures, study of mixing methods were also included. Mixing method is the specified order in which ingredients of concrete are introduced in the mixer along with the stages of addition, if any, and time of agitation at each stage. Ingredients of Fly Ash based concrete are added into the mixer in different stages and in every stage, it is agitated for a specified period of time.

Mixing is important to achieve desirable homogeneity and performance of concrete mix. Success of a mixing method depends on optimal combination of mixing energy, time, and mixing sequence. However, studying of mixing method of concrete is difficult because there has been no consensus on evaluation criteria for quality of concrete mixing. The material and mixing systems usually mutually interact. It was expected that mixing methods have influence on property of concrete. A study was conducted to assess the impact of mixing method on the fresh state properties, strength and durability of the concrete. Laboratory mixer of 10 x 7 tilting drum types was used for this study.

Identification of Mixing Methods

A multistage mixing sequence with varying time of agitation at each stage was adopted for the study. The details of these mixing methods are given in Table 1.

Effect of Mixing Methods in Behavior of Flyash Concrete

Mixing method I & III are three stage mixing sequence while mixing method II, IV and V are two stage mixing sequence. Coarse Aggregate, Fine Aggregate and Cement was always loaded in the mixer in the first stage itself. Variation was made for Flyash, quantity of water and chemical admixture in the different mixing methods. Mixing method IV and V were identical in terms of loading sequence, the only difference being the time of agitation in second stage. Except mixing method IV, total mixing time in all the methods was maintained as 270 seconds. (4.5 minutes.)

Identification of Mixes

Mix proportions of M50, M35 and M20 grade of concrete with 40%, 50% and 60% cement replacement levels (CRL) respectively for carrying out the study on mixing methods are given in Table 2.

Effect of Mixing Methods in Behavior of Flyash Concrete

Results and Discussion

The properties of fresh and hardened state of concrete mixes produced by different mixing methods for M50, M35 and M20 grade identified mixes are given in Table 3. The results for slump are plotted in figure 1.The compressive strength results of mixes at 14, 28 and 56 days produced by different mixing methods for grade M50, M35 and M20 are given is Figure 2. The RCPT result of these mixes at 28 days and 56 days respectively are given in Figure 3.

Effect of Mixing Methods in Behavior of Flyash Concrete

Effect of Mixing Methods in Behavior of Flyash Concrete
Figure 1: Slump for concrete mixes produced by different mixing methods

Effect of Mixing Methods in Behavior of Flyash Concrete
Figure 2: Compressive strength of concrete mixes produced by different mixing methods

Effect of Mixing Methods in Behavior of Flyash Concrete
Figure 3: RCPT results for concrete mixes produced by different mixing methods

From the mixing method trials for TPC candidate mixes, it is seen that the mixing method IV with duration of 210 seconds was not giving satisfactory results for strength and durability tests hence ruled out. Among the other four, though mixing method of I &V were found to be giving good results when strength and durability tests are considered. Mixing sequence V was found to be satisfactory when fresh, hardened properties and durability aspects are considered together.

Summary

As expected, the mixing method and sequencing has noticeable influence on the behavior of the concrete mixes both in fresh and hardened states. Mixing method, V was finalized for further studies on fly ash concrete, as it is a two stage mixing, and results were satisfactory when fresh, hardened properties and durability aspects are considered together. The optimum mixing method for a given batching plant may be developed before start of the work. The duration of the mixing time corresponding to 270 seconds mixing time for laboratory mixer has to be calculated for equivalent mixing time for automatic batching plant, keeping the mixing energy same.

Acknowledgment

Authors are grateful to the management of NPCIL for financing the project "Development of FLY Ash Concrete Suitable for NPP Structures," BHAVINI for providing the facilities and AERB, NPCIL for manpower and guidance.
Click Here
To Know More or to Contact the Manufacturer
Please let us know your name.
Invalid Input
Please let us know your Designation.
Please let us know your Contact Number.
Please let us know your email address.
Please brief your query.
Our other Value-Added Services:

To receive updates through e-mail on Products, New Technologies & Equipment, please select the Product Category(s) you are interested in and click 'Submit'. This will help you save time plus you will get the best price quotations from many manufacturers, which you can then evaluate and negotiate.

Invalid Input
Invalid Input
Invalid Input
Innovation and entrepreneurship are essential ingredients in building a successful commercial venture. The ways in which these two concepts fuel enterprise are something entrepreneur's never stop exploring. There is no doubt that innovation were

Read more ...

Alite and belite are the predominant phases of Portland cement formulation. Alite is impure tricalcium silicate (C3S) and belite is impure dicalcium silicate (C2S). The impurities are an integral part as cement is manufactured

Read more ...

Concrete is a versatile construction material and day by day its consumption is increasing globally. It is second only to water in the global consumption. No civil engineering structure is feasible without using concrete

Read more ...

The use of Graphene with concrete has been talked about and researched ever since Graphene was invented in 2010 which grabbed its inventors a Nobel prize. Nanospan is the first company in the world to break technological and commercial

Read more ...

Fosroc is the foundation of the JMH Group. It employs over 1700 employees in 17 operating companies based in Europe, the Gulf & Middle East, India, South Asia, and China. Through FGT, its trading company, it services another 50 countries

Read more ...

Established in 1983 by French expatriate entrepreneurs, the Dextra Group has a long history of growth and development, driven by strong entrepreneurship and innovation. It has diversified into three main activities: manufacturing, trading and freight forwarding

Read more ...

Jyotirmoy Mishra, Ph.D. Scholar, Department of Civil Engineering, Veer Surendra Sai University of Technology, Burla, Odisha, presents his research on the feasibility and compressive strength performance of geopolymer concrete

Read more ...

As every one ton of Cement (OPC) produced, emits 0.96 tons of CO2, there is an urgent need to promote blending materials (ex. GGBS &PSC) and screened slag, to achieve lower CO2 emissions, reduce greenhouse gas effect, reduce exploitation

Read more ...

In most of the developing countries, demand for steel for use as a reinforcing material is increasing day by day. However, when steel is in short supply, one can consider bamboo as an alternative material for reinforcement

Read more ...

There is high demand for white cement in countries with hot climates, as more heat is reflected from white concrete surfaces as compared to standard grey concrete. As a value-added product, white cement is becoming

Read more ...

Garry Martin, Director - Major Projects, Low & Bonar Construction Fibres, presents a new examination of the benefits of micro fibres in both the plastic and hardened state of concrete and their contribution to increased sustainability.

Read more ...

An integrated material and structural design strategy of strength through durability is the need of the hour since structures are designed for ductility and structural integrity. Dr. S. B. Hegde, President – Manufacturing

Read more ...

The demand for structural strengthening of ageing structures is growing rapidly in buildings, industrial structures, infrastructure projects like bridges, dams, etc. Structural Strengthening also

Read more ...

Durability and strength are two most important criteria and requirements for the long-term performance of concrete structures against weathering action, chemical attack and abrasion. Any deficiency

Read more ...

Cement is a key binder component of concrete production in the building industry. It is a complex hydraulic binder, made up of four main clinker components; alite (Ca3SiO5), belite (Ca2SiO4)

Read more ...

FAIRMATE manufactures a complete range of construction chemicals and provides cost-effective solutions and world-class services to the Speciality Construction Chemicals Industry in alliance with leading

Read more ...

Corrosion of concrete is a major issue and many concrete structures on adverse environment have experienced unacceptable losses in terms of serviceability, ultimately requiring replacement

Read more ...

Cement is the most used industrial commodity required for development, but it is also responsible for high GHG emissions; so there is a need to create a balance between the nation’s growth and environment sustainability

Read more ...

Cement concrete is the most consumed materials on the earth next only to water. The ingredients used in preparing concrete are not sustainable. The ingredients are responsible for causing global warming. The most

Read more ...

India’s ready-mix concrete (RMC) market is projected to witness a 7-9% CAGR in the next five years. This growth is predominantly driven by the increased investments in the development of infrastructure throughout

Read more ...

×
Sign-up for Free Subscription
'India Construction Week'
Weekly e-Newsletter on Construction Industry
Get the latest news, product launches, projects announced / awarded, government policies, investments, and expert views.