Chloride Diffusion of Concrete on Using GGBS as a Partial Replacement Material for Cement and Without and With Superplasticiser

V.S.Tamilarasan, Research Scholar and Assistant Professor, Department of Civil Engineering, Dr.Sivanthi Aditanar College of Engineering, Tiruchendur and Dr. P.Perumal, Professor & Head, Department of Civil Engineering, Government College of Engineering, Salem

Increase in environmental awareness over the past decade, resulted in increasing attention to individual pollution and waste management control. The use of recycled waste cementitious materials is becoming of increasing importance in construction practice.

In India, we produce about 7.8 million tonnes of blast furnace slag, which is a by-product of steel. The disposal of GGBS as a landfill is a problem, which leads to serious environmental hazards. GGBS can be incorporated in cementitious materials to modify and improve certain properties for specific uses.

An attempt is made to replace partially GGBS for cement in concrete of M20 & M25 grades and study its Chloride diffusion. GGBS is replaced for cement in the level of 10%, 20%, 30%, 40%, 50% and 60%. The study results showed that, with the increase in percentage of GGBS, the Chloride diffusion of concrete decreases. Also it is found that the Chloride diffusion in the M25 concrete is less than M20 concrete.

The partial replacement of GGBS for cement in concrete has great potential economical benefits in all areas of construction industry. The GGBS will also make a significant contribution to sustainable development.

Introduction

In recent years there is an increasing awareness regarding environmental pollution due to domestic and industrial waste. Now pollution control board is formed to regulate environmental degradation due to industrial waste. The development and use of blended cement is growing in Asia, mainly due to considerations of cost saving, energy saving, environmental protection and conservation of resources.

Ground Granulated Blast furnace Slag is a by-product obtained in the manufacturing of pig iron in the blast furnace. It is a non-metallic product consisting essentially of silicates and aluminates of calcium and other bases. The molten slag is rapidly chilled by quenching in water to form a glassy sand like granulated material. GGBS is recognized as a desirable cementitious ingredient of concrete and as a valuable cement replacement material that imparts some specific qualities to composite cement concrete.

In India, we produce about 7.8 million tonnes of blast furnace slag and it is available separately as GGBS. The disposal of such slag even as a waste fill is a problem and makes serious environmental hazards with the projected economic growth and development in the steel industry, the amount of production is likely to increase many folds and environmental problem will thus pose a larger threat.

It is seen that high volume eco-friendly replacement by such slag leads to the development of concrete, which not only utilizes the industrial wastes but also saves a lot of natural resources of energy. While using the GGBS in concrete, it reduces heat of hydration, refinement of pore structure, permeability and increase the resistance to chemical attack.

Chloride Permeability of concrete is the relative ease with which chloride ion can penetrate into the pores of concrete. The study of chloride permeability in concrete is of importance when concrete is subjected to chlorine atmosphere such as saline nature, chlorine-manufacturing plants etc. The penetration of chlorine ions into concrete may lead to the corrosion of reinforcement and hence weaken the structures and also adversely affect durability of concrete. Therefore a detailed study has been required to find the chloride permeability of concrete.

The factors affecting chloride permeability are as follows
  • Physico-chemical properties of the mass transport system
  • Chloride source concentration
  • Addition of mineral and chemical admixtures
  • Water binder ratio

Materials Used

Cement

Ordinary Portland cement of 53 grade was used, which has the fineness modulus 1.5, Specific gravity 3.08, Consistency 37%, Initial setting time 2hrs 30 min and Final setting time 3hrs 30min.

Coarse aggregate

Angular shape aggregate of size of 20 mm was used and it has the following properties: Specific gravity 2.935, Flakiness index 100%, Abrasion value 20.4%, Crushing value 30.02%, Impact value 23.6%, Bulk density 1.42 x 103 Kg/m3 and Water absorption 1.01%.

Fine aggregate

River sand conforming to zone III of IS: 383 – 1970 was used and its properties are found as follows: Specific gravity 2.68, Moisture content 0.71 and Fineness modulus 2.75.

GGBS

Physical properties of GGBS are: Specific gravity 3.44 and Fineness modulus 3.36, and the chemical composition of GGBS is Carbon (C) 0.23%, Sulphur (S) 0.05%, Phosphorous (P) 0.05%, Manganese (Mn) 0.58%, Free silica 5.27% and Iron (Fe) 93.82%.

Chloride Permeability

For reinforced concrete bridges, one of the major forms of environmental attack is chloride ingress, which leads to corrosion of the reinforcing steel and a subsequent reduction in the strength, serviceability, and aesthetics the structure. This may lead to early repair or premature replacement of the structure. A common method of preventing such deterioration is to prevent chlorides from penetrating the structure to the level of the reinforcing steel bar by using relatively impermeable concrete. The ability of chloride ions to penetrate the concrete must then be known for design as well as quality control purposes. The penetration of the concrete by chloride ions, however, is a slow process. It cannot be determined directly in a time frame that would be useful as a quality control measure. Therefore, in order to assess chloride penetration, a test method that accelerates the process is needed, to allow the determination of diffusion values in a reasonable time.

Principle

This test method consists of measuring the amount of electrical current passed through 50 mm thick slices of 100 mm nominal diameter cores or cylinders during a 6-h period. A potential difference of 60-voltage dc is maintained across the ends of the specimen. One of which is immersed in a sodium chloride solution, the other in a sodium hydroxide solution. The total charge passed, in coulombs, found to be related to the resistance of the specimen to chloride ion penetration.

Significance and use

This test method covers the laboratory evaluation of the electrical conductance of concrete samples to provide a rapid indication of their resistance to chloride ion penetration. The test method is suitable for evaluation of materials and material proportions for design purposes and research development.

Methodology

10%, 20%, 30%, 40%, 50% and 60% of cement was replaced by means of GGBS, which is the by-product of steel. The mix grades used were M20 and M25. For each level of replacement, 3 cylindrical specimens were cast by using thoroughly mixed cement, fine aggregate, coarse aggregate and water in the mixer machine. All the specimens were kept for curing in the water for a period of 28 days and specimens were arranged in RCPT testing machine and test is carried out for 6 hrs. Afterwards, using formulae, total charge passed was found out. The results are tabulated as shown in tables from 1 to 5 and the conclusions are made.

Test specimen

The specimen was cylindrical shape, size of 100mm diameter, 50mm length. Three cylindrical specimens were used for each percentage of replacement of slag for determining chloride ion penetration.

Procedure

The apparatus consists of two cells. The specimen was mounted as shown in Fig 1 and fixed between the cells in such a way that the round edge surface should touch with the solution. After fixing the specimen, the negative side of the cell was filled with 3% NaCl solution. The positive side of the cell was filled with 0.3M NaOH solution till the top surface of the concrete immerses in the solutions. Leakage was checked. Copper rods were used as electrodes. The wires, electrodes, power supply are connected.

AASHTO T277
Figure 1: AASHTO T277 (ASTM C1202) test setup

A D.C supplier was used to give electrical potential of 12v. The –ve terminal of D.C.S was connected with electrode of NaCl solution. The +ve terminal of D.C.S was connected with electrode of NaOH solution.

As per electro - chemistry principle, due to the applied voltage, the negative ion i.e. the chloride ion was attracted towards positive terminal i.e. NaOH reservoir. Therefore the chloride ion moves through the concrete specimen. Also the positive ion passes towards the negative terminal i.e. NaCl reservoir through the concrete specimen.

Due to the movement of positive and negative ions current was produced. This current was shown in D.C supplier. Reading was taken immediately after voltage supplied at every 30 minutes. This procedure was done for 6 hours duration. Decrease in charge passed values indicates that the concrete has more resistance to chloride ion penetration

Formulae

The total charge passed is a measure of the electrical conductance of the concrete during the period of the test. If the current is recorded at 30 min interval, the following formula, based on the trapezoidal rule, can be used with an electronic calculator to perform the integration:

Q=900(I0+2I30+2I60+……………. +2I300+2I330+I360)

Where:
Q= charge passed (Coulombs)
I0 = current (Amperes) immediately after voltage is applied, and
It = Current (Amperes) at t min after voltage is applied.

Correction:
If the specimen diameter is other than 3.75 inch (95 mm) the value for total charge passed must be adjusted. The adjustment is made by multiplying the value by the ratio of the cross-sectional areas of the standard and the actual specimens. That is:

Qs = Qx x (3.75/X) 2

Qs = charge passed (coulombs) through a 3.75-inch (95-mm) diameter specimen.

Qx = charge passed (coulombs) through X in diameter specimen and

X = Diameter (inch) of the nonstandard specimen.

Mix proportions

Mix proportions are calculated for M20 & M25 grade concrete. The mix ratio for M20 grade concrete is 0.5:1:1.6:3.559 & the mix ratio for M25 grade concrete is 0.44:1:1.326:3.11

Test results

The experimental procedure is conducted on various types of mix containing partial replacement of cement by GGBS. The values of charge passed are tabulated as shown in Table 1 to 5.

Diffusion of Concrete

Diffusion of Concrete

Diffusion of Concrete

Diffusion of Concrete

Diffusion of Concrete

Graphs

Graphs (Fig 2 to 9) are plotted by taking % of replacement of GGBS in x-axis and charge passed in Y-axis for M20 & M25 grades.

Chloride Permeability of M20 Grade
 
Chloride Permeability of M25 Grade
Figure 2: Chloride Permeability of M20 Grade With GGBS Concrete
 
Figure 3: Chloride Permeability of M25 Grade With GGBS
Chloride Permeability of M20 Grade
 
Chloride Permeability of M25 Grade
Figure 4: Chloride Permeability of M20 Grade Super Plasticiser Added GGBS Concrete
 
Figure 5: Chloride Permeability of M25 Grade Super Plasticiser Added GGBS Concrete
Comparision of M20 & M25
 
Comparision of M20 & M25
Figure 6: Comparision of M20 & M25 GGBS Concrete
 
Figure 7: Comparision of M20 & M25 Grade Super Plasticiser Added GGBS Concrete
Comparision of Concrete
 
Comparision of Concrete
Figure 8: Comparison of M20 grade GGBS Concrete & Super Plasticiser Added GGBS Concrete
 
Figure 9: Comparision of M25 Grade GGBS Concrete & Super Plasticiser Added Ggbs Concrete

Results & Discussion

The Chloride diffusion tests in M20 & M25 grade concrete were conducted using RCPT testing machine. The results are stated as below:

For conventional concrete, the Charge passed for M20 and M25 grade concrete are 407 Coulombs and 318 Coulombs respectively.

For grade M20 with GGBS the Charge passed values varies from 358 Coulombs to 292 Coulombs and for grade M25 with GGBS the Charge passed values varies from 298 Coulombs to 170 Coulombs.

For grade M20 Superplasticiser added GGBS concrete, the Charge passed values varies from 553 Coulombs to 345 Coulombs and for grade M25 Superplasticiser added GGBS concrete, the Charge passed values varies from 378 Coulombs to 185 Coulombs.

Conclusion

For both the grades of GGBS concrete and Superplasticiser added GGBS concrete, as the replacement level increases, the chloride permeability value decreases which improves the chloride penetration resistance of the concrete and durability of concrete.

By using GGBS as a replacement material for cement, the cost of construction will be reduced. Use of GGBS in concrete also prevents the environment from degradation.

M25 grade concrete has less chloride permeability than the M20 grade concrete. So, the permeability value also depends upon the mix grade of the concrete.

Bibliography

  • Adakhar, "Compatibility of super plasticizer slag added concrete in sulphate resistance and chloride penetration," Advances in Civil Engineering Materials and construction technology, vol.33, 2001.
  • Balamurugan, P. and Perumal, P., "Behaviour of High Performance Concrete under elevated temperature and chloride penetration." Proceedings of the National seminar on Futuristic in concrete and construction Engineering, SRM Engineering College, Kattankulathur, pp 8.1-8.11. 2003
  • Chung-Chia Yang, "Relationship between Migration Coefficient of Chloride Ions and Charge Passed in Steady State," ACI Material Journal, pp. 124-129, March – April 2004.
  • IS: 456-2000, Code of practice for Plain and Reinforced Concrete.
  • IS: 10262-2004, Code of Practice for Concrete Mix Design.
  • Rajamane, N.P. and Annie peter, J. et.al, "Improvement in Properties of High Performance Concrete with Partial Replacement of Cement by Ground Granulated Blast Furnace Slag," IE(I) Journal-CV, Vol.84, pp38-41, May 2003.
  • Shetty, M.S. "Concrete Technology." S.Chand & Co, New Delhi 2002.
  • "Standard Test Method for Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration," ASTM, pp. 646-651.
  • Suvimol Sujiavanich et.al., "Chloride Permeability and Corrosion Risk of High-Volume Fly Ash Concrete with Mid-Range Water Reducer," ACI Material Journal, pp. 177-182, May – June 2005.
  • Tiewei Zhang and Odd E.Gjorv., "Effect of Chloride Source Concentration on Chloride Diffusivity in Concrete,' ACI Material Journal, pp. 295-298, Sep – Oct 2005.
Concrete Rheology - Unveiling the Secrets of Concrete
Concrete is a heterogeneous composite complex material, and its hardened property is influenced by its fresh property. Concrete today has transformed into an advanced type with new and innovative ingredients added - either singly or in

Read more ...

ICRETE: Making Concrete Economical
ICRETE offers many benefits apart from reducing cement content and giving high grades saving to ready-mix concrete companies; it helps reduce shrinkage and permeability in concrete slabs, increases the durability of concrete, and also works

Read more ...

UltraTech Cement to implement Coolbrook’s RotoDynamic HeaterTM revolutionary technology for industrial electrification
UltraTech Cement Limited, India’s largest cement and ready-mix concrete (RMC) company, and Coolbrook, a transformational technology and engineering company, will jointly develop a project to implement Coolbrook’s RotoDynamic HeaterTM (RDH)

Read more ...

Plastic Shrinkage and Cracks in Concrete
Plastic shrinkage cracking occurs when fresh concrete is subjected to a very rapid loss of moisture. It is caused by a combination of factors such as air and concrete temperature, relative humidity, and wind velocity at the surface of concrete. These can cause

Read more ...

Mechanised way of plastering with spray Plaster Machine
This paper covers the research work carried out on cement plastering process for internal and external building wall by using spray plastering machine. Objective of study is to experiment and compare the plastering activity by conventional way and

Read more ...

Construction Defects Investigation & Remedies
In recent years, the speed of construction has increased very fast; buildings which used to take 3-5 years are now getting completed in 1-2 years. There is a race to complete projects faster, but due to this speedy construction, the quality of construction is often

Read more ...

Challenges in usage of Hydrogen in Cement Industry
With its zero-emission characteristics, hydrogen has become a promising decarbonization path for the cement industry. While there are several issues that need to be resolved in the use of hydrogen, there are also many advantages, so much so that the growth

Read more ...

Enhancing Corrosion Resistance of Steel Bars in Reinforced Concrete Structures
Reinforced concrete is a composite material which is made using concrete and steel bars. Concrete takes the compressive forces and steel bar takes tensile forces. Concrete around the steel bar protects it from corrosion by providing an alkaline environment

Read more ...

Moving toward workability retention to rheology retention with low viscosity concrete technology
Amol Patil, Sr. Specialist - General Manager (Admixture and Specialty Products), Master Builders Solutions (India), and Nilotpol KAR, Managing Director, Master Builders Solutions (South Asia), present a paper on the concept of low viscosity concrete in

Read more ...

Cement industry innovating eco-friendly packaging
Cement companies are constantly innovating to meet global sustainability standards and improve logistics, shelf life, and utility of cement, while reducing wastage. Thei aim is to reduce their environmental impact without compromising their product

Read more ...

IIT Madras uses Solar Thermal Energy to Recycle Waste concrete
Researchers at the Indian Institute of Technology Madras have developed a treatment process using solar thermal energy to recycle construction and demolition debris. Waste concrete from demolition was heated using solar radiation to produce recycled concrete

Read more ...

Textile Reinforced Concrete - A Novel Construction Material of the Future
As a new-age innovative building material, TRC is especially suited for maintenance of existing structures, for manufacturing new lightweight precast members, or as a secondary building material to aid the main building material. Textile Reinforced Concrete

Read more ...

Technological Innovation for Use of Bottom Ash by-product of Thermal Power Plants in the Production of Concrete
The day is not far for the adoption of this innovative, eco-friendly, and cost-effective bottom ash – concrete process technology by construction agencies undertaking road/infrastructure project works, real estate developers, ready mix concrete (RMC) operators

Read more ...

Headed Bars in Concrete Construction
Using headed bars instead of hooked bars offer several advantages like requirement of reduced development length, less congestion, ease of transport and fixing at site, better concrete consolidation, and better performance under seismic loads.

Read more ...

Sustainability of Cement Concrete - Research Experience at CRRI on Sustainability of Concrete from Materials Perspective
It can be said that ever since the publication of the document of World Commission on Environment and Development [1], the focus of the world has diverted towards sustainability. Gro Harlem Bruntland [1] defined sustainable development as “development

Read more ...

Shrinkage, Creep, Crack-Width, Deflection in Concrete
The effects of shrinkage, creep, crack-width, and deflection in concrete are often ignored by designers while designing structural members. These effects, if not considered in some special cases such as long span slabs or long cantilevers, may become very

Read more ...

Concrete Relief Shelve Walls - An Innovative Method of Earth Retention
Relief shelve walls are a unique concept that use only conventional construction materials like PCC / RCC / steel reinforcements, and work on a completely different fundamental to resist the lateral load caused due to soil. Information on the various dimensions

Read more ...

Carbon Neutrality in Cement Industry A Global Perspective
Increasing energy costs, overcapacity, and environmental pollution are the top concerns of the cement industry, which is one of the major contributors to CO2 emissions. Dr S B Hegde, Professor, Department of Civil Engineering, Jain College of Engineering

Read more ...

Finnish company Betolar expands to Indian concrete markets with a cement-free concrete solution
Betolar, a Finnish start-up, and innovator of geopolymer concrete solution Geoprime®, has expanded its operations to Europe and Asian markets including India, Vietnam and Indonesia. Betolar’s innovation Geoprime® is the next-generation, low carbon

Read more ...

Why Fly Ash Bricks Are Better Than Clay/Red Bricks
It is estimated that in India each million clay bricks consume about 200 tons of coal and emit around 270 tons of CO2; on the other hand, with fly ash bricks production in an energy-free route, there are no emissions. Dr. N. Subramanian, Consulting

Read more ...