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Mr. Balaji K. Moorthy

Honoary ChairpersonDr. Bhanumathi Das

EditorEr Anil Kumar Pillai

MembersEr Srinivasa Rao

Er Shashank SharmaEr Suraj

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Er BilalEr Arindam Acharya

Er Venkatesh Pulavarty Er Vishnu Narayanan Namboothiry

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Vol. II No.1

ContentsChairman’s Message 03

Engineers Day Good Concrete Practices 04

International Workshop on Sustainability and Advances in Concrete Technology ( SACT 2012) – NIT Calicut 05

Performance of Blended Cement Concrete Subjected to Elevated Temperatures 06

Interaction with Engineers & Participation in Exhibition 19

Readers Feedback on TECHMANTRA 20

Projects associated with RAMCO DryMix 21

Projects Associated With RAMCO Cement 22

MACE Division 24

Chairman’s Message

Dear Friends Greetings from Ramco ! Customer Delight is one of our Mantras and we, at Ramco, leave no stone unturned to ensure

that our products and services exceed the quality standards and expectations of our customers. We are well aware that in today’s scenario, the customer has diverse requirements and myriad options. We, therefore, are well aware that we cannot remain complacent with our offerings. That is the reason, we constantly interact with our customers - to study and understand and fi ne tune our offerings to their changing needs.

We are well aware that one of the biggest challenges that you construction professionals face is to ensure quality workmanship at construction sites. In order to support you, we have ramped up the activity of our MACE division comprising of qualifi ed civil engineers. Our MACE division engineers constantly visit construction sites and conduct demonstrations and trials and help masons and site engineers in making durable concrete. The response from construction professionals has been very positive and we are in the process of strengthening our MACE team. We sincerely hope that this activity of ours will help in reducing some of your burden and concerns.

You are well aware that our commitment to environment and sustainable development is total. It was our privilege to extend our support for the International Workshop on Sustainability and Advances in Concrete Technology held at NIT – Kozhikode . I am happy to note that experts and academicians from across the globe have presented papers on the usage of alternative supplementary cementitious materials to be used in concrete. I am sure this will go a long way in creating better awareness to the need for sustainable development.

Let me also take this opportunity to wish you all a happy Engineers Day which falls on September 15th . I am sure that this day would be an opportunity for all construction professionals to get together and deliberate on various challenges which face us in building a more durable and stronger India.

With my best wishes

P R Ramasubrahmaneya RajhaChairman & MD

Engineers Day 2012

Madras Cements Ltd wishes every Engineer a Happy Engineers Day . About Engineers day : Engineers day is celebrated every year in India on September 15th to commemorate the birthday of the legendary Engineer Sir M. Visvesaraya ( 1861-1962) . He was also a scholar , statesman and the Diwan of Mysore during 1912 to 1919 . He is recognized for his works in harnessing water resources which lead to the design and construction of several river dams , bridges and implementation of drinking water schemes all over India . Some of his most successful projects include the design and construction of K.R . Sagar dam and its adjoining Brindavan Gardens , turn around of the Bhadravathi Iron and Steel Works setting up of the Mysore Sandalwood Oil factory and the founding of the Bank of Mysore.

Good Concrete Practices – Guidelines Compaction : Adequate compaction without segregation should be ensured by providing suitable

workability and by employing appropriate placing and compacting equipment and procedures . Full compaction is particularly important in the vicinity of construction and movement joints and of embedded water bars and reinforcement

Finishing Practices: Good fi nishing practices are essential for durable concrete Overworking the surface and addition of water /cement to aid in fi nishing should be avoided ; the resulting laittance will have impaired strength and durability and will be particularly vulnerable to freezing and thawing under wet conditions.

Curing : It is essential to use proper and adequate curing techniques to reduce the permeability of the concrete and enhance its durability by extending the hydration of the cement , particularly in its surface zone.

Concrete in sea water : Concrete in sea water or exposed directly along the sea coast shall be atleast M20 Grade in case of plain concrete and M30 in case of reinforced concrete . The use of slag or pozzolona cement is advantageous under such conditions.

Form removal : Forms shall not be released until the concrete has achieved a strength of atleast twice the stress to which the concrete may be subjected at the time of removal of formwork . The strength referred to shall be that of concrete using the same cement and aggregates and admixture , if any , with the same proportions and cured under conditions of temperature and moisture similar to those existing on the work . Dosage of Chemical Admixtures: Dosage of retarders , plasticisers and superplasticisers shall be restricted

to 0.5, 1.0 and 2.0 percent respectively by weight of cementitious materials and unless a higher value is agreed upon between the manufacturer and the constructor based on performance test.

Supervision during Concreting : It is exceedingly diffi cult and costly to alter concrete once placed . Hence , constant and strict supervision of all the items of construction is necessary during the progress of work , including the proportioning and mixing of the concrete . Supervision is also of extreme importance to check the reinforcement and its placing before being covered.

- Compiled from IS 456 : 2000 – PLAIN AND REINFORCED CONCRETE – CODE OF PRACTICE

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International Workshop on Sustainability and Advances in Concrete Technology

( SACT 2012) – NIT CalicutMadras Cements Ltd was associated as a sponsor during the International Concrete Workshop

held at National Institute of Calicut from 7-8th May 2012 .

Technical Services team of Madras Cements with delegates of “ International Workshop on sustainability and advances in Concrete Technology ( SACT 2012) ” at NIT – Kozhikode

Few of the major papers presented during the workshop were as follows :

Sustainability Issues and Concrete Technology: Dr V.M.Malhotra, President of Supplementary Cementing Materials for Sustainable Development Inc. Ottawa, Canada

A New look at Fiber Reinforced Concrete as a sustainable Material: Prof V.Ramakrishnan, Distinguished Professor Emeritus South Dakota School of Mines and Technology, USA

Lightweight Concrete and Sustainability Issues: Dr. Theodore W. Bremner Professor Emeritus, Department of Civil Engineering, University of New Brunswick, Canada

Concrete with High Volume of supplementary Cementing Materials and Admixtures for Sustainable and Productive Construction: Dr Harold Justnes Chief Scientist, SINTEF, Trondheim, Norway

The Indo Norwegian initiative on sustainable utilization of alternative materials in cement and concrete – Potential for increased use: Mr Christian Jon Engelson, Senior Scientist, SINTEF, Trondheim, Norway

C02 – Emission – Tripple Focus: Mr Per Jahren Consultant, Oslo, Norway

Recent Progress of Chinese Cement Industry on Energy Saving and Emission Reduction : Dr SUI Tongbo, Professor, Academy Member, China Building materials Academy Beijing, China

High Performance Concrete – For More Sustainable Construction Dr Per Fidjestol Global Technical Marketing manager, Elkem, Norway

Studies on GeoPolymer Concrete : Dr B. Vijaya Rangan, Emeritus Professor Curtin University of Technology, Perth, Australia

Retrofi tting of Structures Using Ferrocement Laminates: Dr P.Paramasivam Professorial Fellow, National University of Singapore

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Subhash C. Yaragal 1, K S Babu Narayan 2, Sushanth Nayak 3 , Shoaib Mohammed 4 , Shrihari K Naik 5, Ahamad Farid S 6, and Darshan Patel 7

1,2 Associate Professors, 3,4,5,6 UG Students, 7 PG Student, Department of Civil Engineering, National Institute of Technology, Karnataka, Surathkal, PO Srinivasnagar – 575025, Karnataka State, INDIA .

email: subhashyaragal@yahoo.com

Abstract: Concrete is a popular building material due to its special property of mouldability to any shape. With a huge volume of production of concrete worldwide, manufacture of Ordinary Portland Cement (OPC) is responsible for fi ve percent of global carbon dioxide emissions every year. There is wide scope for reducing use of OPC by adopting environmental friendly substitutes like Ground Granulated Blast Furnace Slag (GGBS), Fly Ash and Silica Fume etc. This paper discusses the effect of replacement of OPC with different percentages (10%, 20%, 30%, 40% and 50%) of GGBS, on the compressive and split tensile strength of 100 mm cubes subjected to elevated temperatures of 200 0 C, 400 0 C, 600 0 C and 800 0 C. The retention period for all the cases is 2 hours. Results indicate that, at all the fi ve levels of OPC replacement with GGBS, specimen exhibited better temperature endurance properties in terms of residual compressive and split tensile strengths when compared to the specimen at ambient temperature. From the present investigation, it is observed that, 40% replacement of OPC has shown better performance in terms of strength, at all levels of exposure studied.Further for the case of 30% OPC replacement by GGBS, the effect of specimen cooling either in furnace or by water quenching on the strength loss is also reported.

Keywords: Elevated Temperatures, Compressive Strength Retention, Concrete Cubes, Cooling Regimes.

1. INTRODUCTION

1.1 GeneralConcrete is the widely used construction material on earth. The reason being concrete could be cast in any desired shape and it is cheaper when compared to other materials. But the availability of natural resources is limited, so we need a supplementary material to cement which will act as the binder in production of concrete. Also cement contributes immensely in the CO2 emission which is a major concern at present. Hence GGBS, the by product obtained during the production of iron is used as the supplement to OPC. It has been found that using GGBS will enhance the strength, durability, fi re resistance properties of concrete. Slag being a by product does not generate any CO2, thus is environmental friendly. Citing various benefi ciaries in using GGBS, lot of research is taking place to observe various other characteristic of GGBS when used as the replacement to cement.

1.2 Ground Granulated Blast Furnace Slag (GGBS)Ground granulated blast furnace slag (GGBS or GGBFS) is the ground blast furnace slag which is obtained by quenching molten iron slag (a by-product of iron manufacture) from a blast furnace in water or cold air, to produce a glassy, granular product and drying the same. GGBS is used to make durable concrete structures in combination with OPC and/or other pozzolanic materials. Concrete made with GGBS cement sets more slowly than concrete made with ordinary Portland cement, depending on the amount of GGBS in the cementitious material, but also continues to gain strength over a longer period. This results in lower heat of hydration and lower temperature rises, and avoids cold joints easier, but may also affect construction schedules. Replacement levels for GGBS vary from 30% to up to 85%. Typically 40 to 50% is used in most instances.

1.3 AppearanceConcrete made with Portland cement is stony grey in colour whereas the near-white colour of GGBS cement permits architects to achieve a lighter colour for exposed fair-faced concrete fi nishes, at no extra cost. GGBS cement also produces a smoother, more defect free surface, due to the fi neness of the GGBS particles. Dirt does not adhere to GGBS concrete as easily as concrete made with Portland cement, reducing maintenance costs.

Performance of Blended Cement Concrete Subjected to Elevated Temperatures

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1.4 StrengthConcrete containing GGBS cement has a higher ultimate strength than concrete made with Portland cement. It has a higher proportion of the strength-enhancing calcium silicate hydrates (CSH) than concrete made with Portland cement only, and a reduced content of free lime, which does not contribute to concrete strength. Concrete made with GGBS continues to gain strength over time, and has been shown to increase in strength to the double its 28 day strength over periods of 10 to 12 years.

1.5 Physical PropertiesThe following table shows the typical values for the physical properties of GGBS.

Table 1. Typical physical properties for civil and marine GGBS

Fineness 450 to 550m2/kgBulk density 1000 to 1100kg/m3 (loose)

1200 to 1300kg/m3 (vibrated)Specifi c gravity 2.9Colour Off white

CaO SiO2 Al2O3 MgO Fe2O3

GGBS 40% 35% 12% 10% 0.2%OPC 65% 20% 5% 1% 2%

1.6 Chemical Properties GGBS contains the same principal oxides as Portland cement, but in slightly different proportions. The following table compares typical percentages of the principal oxides in GGBS with those in Portland cement.

Table 2. Typical chemical properties for civil and marine GGBS

1.7 Environmental Issues Regarding GGBSTable 3 shows the percentage reductions of various environmental components due to usage of GGBS.

Table 3. Impact of GGBS on the environment

Emission of carbon dioxide 40% reductionAcidifi cation 35% reductionWinter smog 35% reductionEutrophication 30% reductionPrimary energy requirement 35% reduction

1.8 DurabilityConcrete containing GGBS is less permeable and chemically more stable than normal concrete. This enhances its resistance to many forms of deleterious attack, in particular: Disintegration due to sulfate attack Chloride-related corrosion of reinforcement Cracking caused by alkali-silica reaction Provide better fi re resistance.

1.8.1 Permeability and chemical stabilityThe reactions between GGBS, Portland cement and water are complex. When Portland cement reacts with water, the insoluble hydration products (mainly calcium silicate hydrates) form close to the cement particle. The relatively soluble product of hydration (calcium hydroxide) migrates through the pore solution and precipitates as discrete crystals, surrounded by large pores. When GGBS particles are also present, both the GGBS and Portland cement hydrate to form calcium silicate hydrates. Additionally, the GGBS reacts with the excess of calcium hydroxide to form a fi nely dispersed gel, which fi lls the larger pores. The result is a densifi ed cement paste, which contains far fewer calcium hydroxide crystals and therefore has fewer large capillary pores. The reduction in free calcium hydroxide makes concrete chemically more stable, and the fi ner pore structure limits the ability of aggressive chemicals to diffuse through the concrete.

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1.8.2 Concrete in aggressive ground Sulfates occur naturally in the ground and can sometimes have a harmful effect on concrete, causing it to crack and disintegrate. The use of GGBS in concrete gives greatly increased resistance to attack by sulfates. This is well recognised by codes and standards, for example in the latest version of the British Standard for concrete (BS8500), the only option recommended as suitable for the most severe sulfate exposure (Class DC-4m) is a concrete containing at least 66 per cent GGBS. For this severe exposure, sulfate resisting Portland cement is not considered as having adequate resistance. The primary sulfate reaction that causes disruption of hardened concrete is associated with one of the mineralogical phases in Portland cement, tricalcium aluminate. Supfate ions those penetrate the concrete react with either calcium aluminate or its hydrates to form a calcium sulfo-aluminate hydrate called ettringite. Ettringite has expansive tendency and occupies a volume greater than the original constituents and grows as myriad needle-shaped crystals that generate high internal stresses in the concrete and can cause it to crack and disintegrate.

Historically, it had been tried to contain ettringite attack has been prevented by using sulfate resisting Portland cement, in which the tricalcium aluminate level is limited to a low level. More recently, a second form of sulfate attack, called thaumasite attack has been recognised as a problem after the discovery of its effects on some M5 motorway bridges. Thaumasite is a calcium silicate sulfo-carbonate hydrate, which forms at temperatures below 15°C by a reaction between cement paste hydrates, carbonate and sulfate ions. Its formation reduces the cement paste to a soft mulch. Unfortunately, sulfate resisting Portland cement offers no protection against the thaumasite form of sulfate attack. As a result of its reduced permeability and increased chemical stability, concrete containing GGBS is resistant to both forms of sulfate attack. Detailed recommendations for avoiding sulfate attack can be found in Building Research Establishment: Special Digest 1:2005 Concrete in aggressive ground, and the recommendations of this digest have been adopted by BS 8500:2006.

1.8.3 Corrosion of reinforcement by chlorideSteel embedded in concrete is normally protected against corrosion by the high alkalinity created inside concrete by hydrated cement. In fact ordinary iron and steel products are covered normally with a thin iron-oxide fi lm which, under alkaline environment, strongly adheres to the surface of metal and makes the steel passive to corrosion. This is known as passivity fi lm and this is stable as long as the pH of the solution is > 11.5. However, if signifi cant amounts of chloride are able to penetrate the concrete, when the latter becomes permeable, this protection can be destroyed depending on the Cl-/OH- and the embedded steel will rust and corrode.

Because of its fi ner pore structure, GGBS concrete is substantially more resistant to chloride diffusion than Portland cement concrete. For reinforced concrete structures exposed to chlorides, the use of GGBS will give enhanced durability and a longer useful life. The use of GGBS in such instances is expected to increase the life of the structure by up to 50% had only Portland cement been used, and precludes the need for more expensive stainless steel reinforcing.

1.8.4 Alkali-Silica Reaction (ASR)Alkali ions (sodium and potassium) are present in Portland cement. They are readily soluble in water and are released into the pore solution of concrete when the cement hydrates. Here they can slowly interact with reactive silica in the aggregate to produce an alkali-silicate hydrate gel. In the presence of moisture this gel can absorb water, swell and exert suffi cient pressure to crack the concrete. In some cases the resultant cracking is suffi cient to endanger structural integrity. The consequences of ASR can be severe and there is no reliable cure for affected structures. Addition of appropriate percentages of GGBS is an effective means of minimizing the risk of damaging ASR.

1.9 Properties

1.9.1 Setting timeThe setting time of concrete is infl uenced by many factors, in particular temperature and water/cement ratio. With GGBS, the setting time will be extended to some extent. The effect will be more pronounced at high levels of GGBS and/or low temperatures. An extended setting time is advantageous in that the concrete will remain workable longer and there will be less risk of cold joints.

1.9.2 ConsistenceWhile concretes containing GGBS have a similar, or slightly improved consistence to equivalent Portland cement concretes, fresh concrete containing GGBS tends to require less energy for movement. This makes it easier to place and compact, especially when pumping or using mechanical vibration. In addition, it will retain its workability for longer.

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1.9.3 Early age temperature riseThe reactions involved in the setting and hardening of concrete generate signifi cant heat and can produce large temperature rises, particularly in thick-section pours. This can result in thermal cracking. Replacing Portland cement with GGBS reduces the temperature rise and helps to avoid early-age thermal cracking. There are a number of factors which determine the rate of heat development and the maximum temperature rise. These include the percentage of GGBS, the total cementitious content, the dimensions of the structure, the type of formwork and ambient weather conditions. The greater the percentage of GGBS, the lower will be the rate at which heat is developed and the smaller the maximum temperature rise. As well as depressing the peak temperature, the time taken to reach the peak will be extended. For mass concrete structures, it is common to use 70 per cent GGBS to control the temperature rise. With thinner sections, signifi cant savings in crack control reinforcement can be achieved even with lower levels of GGBS of 50 per cent or less.

1.9.4 ColourGround granulated blast furnace slag is off-white in colour and substantially lighter than Portland cement. This whiter colour is also seen in concrete made with GGBS, especially at addition rates of 50 per cent and above. The more aesthetically pleasing appearance of GGBS concrete can help soften the visual impact of large structures such as bridges and retaining walls. For coloured concrete, the pigment requirements are often reduced with GGBS and the colours are brighter.

1.10 Advantages of Using GGBS in ConcreteGGBS is widely being used these days, due to its various benefi ts, compared to the OPC. Here are a few points worth mentioning.

1.10.1 Reduction in CO2 emissionsThe manufacture of normal cement (CEM I of EN 197) results in the emission of 930 kg of CO2/t of cement (British Cement Association, 2009): approximately 50% from decarbonation of the limestone raw material (process emissions), 40% from fossil fuel consumption, and 10% from generating the electricity used in the process. GGBS manufacture typically releases 35 kg of CO2/t of GGBS: less than 4% of the carbon footprint of normal cement.

1.10.2 Solar refl ectanceConcrete made with GGBS will have a high solar refl ectance: there will be increase of 20% in refl ection of sunlight by concrete with GGBS. This will reduce the “heat island” effect in urban developments, as well as having other benefi cial effects (reduced need for artifi cial lighting at night, safer roads from better visibility).

1.10.3 Civil engineering applications Low heat of hydration (large section pours), Resistance to chemical attack (exposure to de-icing salts, sea-waters, sulphates) Use in water-retaining structures (low permeability, crack control) and Architectural requirements (lighter colour, prevention of effl orescence) etc.

1.11 Pertinent Review of Literature and Scope of Current WorkStudies by G. J. Osborne (1998) has demonstrated that use of high levels of slag gave the added benefi t of reducing chloride ingress, which provided enhanced protection to steel reinforcement.Chi-Sun Poon et. Al (2001) have tested four cement pastes containing 0%, 50%, 70% and 90% replacement of slag by weight with OPC. The maximum tested temperature was 500°C with an interval of 100°C. All slag cement paste specimen experienced an increase in strength between 100°C and 250°C.

A.F. Bingol and R. Gul (1998) have reported the compressive strength of normal strength concrete at elevated temperatures up to 7000C and the effect of cooling regimes were investigated and compared. Thus, two different mixture groups with initial strengths of 20 MPa and 35 MPa were produced by using river sand, normal aggregate and Portland cement. Thirteen different temperature values were chosen from 50 to 7000C. The specimen were heated for 3 hours at each temperature. After heating, concretes were cooled to room temperature either in water rapidly or in laboratory conditions gradually. After 4000C, both type of concrete lost their strength rapidly and the strength loss was more in water-cooled specimen when compared to air cooled.

Xin Luo and Wein Sun (2000) have reported that high performance concrete is worse when compared with normal strength concrete after being subjected to different high temperatures of 8000C and 11000C and subjected to cooling regimes of gradual and rapid cooling. Deterioration of compressive strength of the concrete was measured. The results obtained showed

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that the strength of both the HPC and NSC reduced sharply after their exposure to high temperatures. Thermal shock due to rapid cooling caused a bit more deterioration in strength than in the case of gradual cooling without thermal shock. A. M. K. Abdelalim and G. E. Abdel (2009) reported that CO2 powder cooling regime provided the least damage to the concrete after exposure to fi re while water cooling regime was the worst of the studied cooling regimes.

Substantial work that has been reported in literature is on the variation of compressive strength and split tensile strength in general, and with the usage of GGBS at ambient temperature. In this study, the variation in percentage weight loss and residual compressive and split tensile strengths of normal strength concrete and concrete with various percentages of OPC replacement by GGBS at different levels of temperatures (i.e. room temperature, 200°C, 400°C, 600°C & 800°C) is reported. The role of cooling regimes in strength deterioration is also reported for the case of 30% OPC replaced by GGBS.

2. TEST PROCEDURE

2.1 Mix Proportion Total six series of specimen of size 100 x 100 x 100 mm, designed in this investigation consist of one Normal Strength Concrete (M30) and fi ve Concrete with 10% to 50% (at an interval of 10%) replacement of OPC by GGBS cubes.

The design mix proportion for M30 grade is based on 28 days compressive strength results. The optimum mix design proportions have been recommended based on trial mixes. The recommended mix proportions for both the concretes are given in table 4.

Table 4. Mix proportion of M30 concrete (kg/m3)

The measured slump of the fresh concrete is 75-125mm.

Table 5. Table showing percentage replacement of OPC by GGBS for different series

43 grade OPC (kgs)

GGBS(kgs)

Water(liters)

Sand(kgs)

10mmaggregates (kgs)

20mmaggregates (kgs)

430 - 194 515 377 880

Series GGBS replacement for OPCA Pure Cement Concrete (0%)B 10%C 20%D 30%E 40%F 50%

For each series, 48 cubes have been cast and 28 days water cured with the intention of subjecting them to elevated temperature of 200°C, 400°C, 600°C and 800°C. The details of number of specimen required for each series is given in the following table 6.

Table 6. Number of specimen to be tested at different tests and temperatures

Sl No Temperature No. of specimen for direct compression

No. of specimen forSplit tensile

1 Room 3 32 200°C 3 33 400°C 3 34 600°C 3 35 800°C 3 3

15 15Total number of specimen

The remaining 18 cubes in each series are cast in case any erroneous result are obtained, these specimen could be used for repeating the experiment.

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2.2 Electric Furnace Temperature Build-up The specimen were placed in the furnace, target temperatures are adjusted using the knob. Once the target temperature is reached, the specimens are held till the retention period is completed. It is observed that the temperature build up till 400 0C is at a faster rate of 20 0C/ minute compared to temperature built up above 400 0C. Temperature build-up is gradual above 400 0C and is at the rate of 7 0C/ minute. Figure 1 shows the arrangement of cubes in the furnace.

Fig. 1 Arrangement of cubes in the furnace

2.3 Studies on Cooling RegimesFor this purpose 100 mm cubes were cast for the case of 30% OPC replaced by GGBS, adopting the same mix proportion as before. The specimen were heated to temperatures of 150°C, 250°C, 350°C , 450°C and 550°C. The retention period was 1 hour. Two cooling regimes namely furnace cooling and sudden quenching in water are studied.

2.4 Specimen CoolingIn the furnace cooling, after exposing the cubes to the designated temperature they were allowed to cool in the furnace itself till the room temperature was reached. Afterwards the weight loss of specimen was noted and the destructive tests were performed for residual compressive and split tensile strength evaluation. For sudden cooling in water, after exposing the cubes to the required temperature, they were removed from the furnace and were placed in the tub of water which was allowed to cool till room temperature.

3. RESULTS AND DISCUSSION

3.1 SlumpThe slump of concrete with different GGBS content was obtained and tabulated below. The graph of the variation of the slump with increase in GGBS content is also shown below.

Table 7. Slump values for different series

Series Percentage replacement of cement by GGBS Degree of workability

Max MinA 0 95 90 HighB 10 68 48 LowC 20 73 55 MediumD 30 88 58 MediumE 40 115 80 Medium to highF 50 125 95 High

Slump (mm)

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Fig. 1 Variation between slump and GGBS percentage.

Fig. 2 Slump measurement

It is observed from fi gure 1, that with increase in percentage replacement of OPC with GGBS, the workability increases. This is attributed to the fi neness of GGBS which is substantially higher than that of OPC. Therefore as the quantity of GGBS increases the mix becomes more workable. Lowest slump of 68mm has been observed for 10% replacement of OPC with GGBS. Highest slump of 125mm has been observed for 50% replacement of OPC

3.2 Loss of Weight after Exposure to Elevated TemperaturesThe following table shows the summary of weight loss results for all cases studied.

Table 8. Summary of weight loss in concrete cubes at elevated temperature

Fig. 3 Variation of percentage weight loss with temperature

GGBS Level A-series(0%)

B-series(10%)

C-series(20%)

D-series(30%)

E-series(40%)

F-series(50%)

200 4.91 5.06 5.75 4.55 5.29 5.32400 5.90 5.36 6.28 5.59 6.16 7.33600 6.27 7.03 7.15 6.61 8.27 7.56800 6.58 7.91 7.45 6.91 8.23 8.95

Temperature

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From table 8 and fi gure 3 the following observations are made(i)For all cases there is increase in percentage loss in weight with increase in temperature.

(ii) For any temperature, there is increase in percentage loss in weight for cases of pure cement concrete (0%), 10% & 20% replacement of OPC with GGBS.(iii) It is observed that for case of 30% replacement of OPC with GGBS, drop in percentage loss in weight is observed. For cases of 40% & 50% replacement of OPC with GGBS there is further increase in percentage loss of weight.

(iv) It appears that for the case of 30% replacement of OPC with GGBS, the densifi cation of concrete must be better and hence chances for the escape of moisture could be lower compared to other cases.

The following fi gures show the specimen at room temperature (un-exposed) and exposed to 200°C, 400°C, 600°C and 800°C.

Fig. 4 Without exposure

Fig. 5 Test specimen under exposure at 200°C

Fig. 6 Test specimen under exposure at 400ºC

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Fig.7 Test specimen under exposure at 600ºC

Fig. 8 Test specimen under exposure at 800ºC

3.3 Residual Compressive Strength

Table 9 presents the summary of compressive strengths for all cases studied.Table 9. Summary of residual compressive strength (MPa) results for concrete cubes at elevated temperatures.

GGBS Level A-series(0%)

B-series(10%)

C-series(20%)

D-series(30%)

E-series(40%)

F-series(50%)

Room 42.7 40.1 43.2 43.1 38.0 36.3200 43.5 42.0 44.1 37.8 37.0 35.5400 39.0 40.0 41.1 36.0 36.2 34.7600 34.0 37.8 37.0 27.5 23.8 30.6800 13.0 21.5 17.2 16.3 14.3 15.0

Temperature

GGBS Level A-series(0%)

B-series(10%)

C-series(20%)

D-series(30%)

E-series(40%)

F-series(50%)

Room 1.00 1.00 1.00 1.00 1.00 1.00200 1.02 1.05 1.02 0.88 0.97 0.98400 0.91 0.99 0.95 0.83 0.95 0.95600 0.79 0.94 0.85 0.64 0.62 0.84800 0.30 0.53 0.40 0.37 0.37 0.41

Temperature

Table 10. Summary of residual compressive strength results normalised for concrete cubes as factor/co-effi cient at elevated temperatures.

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Fig. 9 Variation of residual compressive strength with temperature

Fig. 10 Residual Compressive Strength vs. Temperature (°C)

From table 10 and fi gures 9 and 10, the following observations are made,1. For all GGBS blended concretes, it is observed that the residual compressive strength decreases with increase in temperature.2. Amongst all cases, 10% replacement cases show the best strength retention of about 53% and the least being 37% for 30% replacement cases, at 800ºC.3. It is observed that at all % replacements GGBS blended concretes indicated better temperature endurance properties at 800ºC. It is also observed that only 30% strength is retained for the case of no replacement of cement by GGBS.4. For 30% replacement case, the performance in strength retention characteristic is the poorest, if all temperatures are considered for comparison.5. At 200ºC, it is seen that the residual compressive strength is higher than the one at ambient temperature for 0%, 10% and 20% replacement of cement by GGBS. This is attributed to the conversion of free water to water vapour.6. The loss of strength is gradual for all cases for exposure temperatures of 200ºC, 400ºC and 600ºC. The loss in strength is observed to be very rapid from 600ºC to 800ºC for all cases.

3.4 Residual Split Tensile Strength Split tensile strength values for various GGBS replacement levels are obtained and tabulated below. The graph between split tensile strength and the temperature is plotted for different percentage of GGBS replacement.

Table 11. Summary of split tensile strength (MPa) results for concrete cubes at elevated temperatures.

GGBS Level A-series(0%)

B-series(10%)

C-series(20%)

D-series(30%)

E-series(40%)

F-series(50%)

Room 4.18 5.06 3.83 3.95 2.92 3.23200 4.93 4.29 3.26 4.23 3.15 3.04400 3.50 2.83 2.86 2.64 2.33 2.53600 1.60 2.97 2.36 1.66 1.53 1.67800 1.15 1.66 1.38 1.30 1.13 1.07

Temperature

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Table 12. Summary of residual compressive strength results normalised for concrete cubes as factor/co-effi cient at elevated temperatures.

Fig. 11 Variation of residual split tensile strength with temperature

Fig. 12 Residual Split Tensile Strength Vs. Temperature

From fi gures 11 and 12, following observations are made,1. For all cases of cement replacement with GGBS, it is observed that the splitting tensile strength decreases with increase in temperature.2. It is observed that the cement replacement by GGBS cases have all indicated better temperature endurances at 800ºC. It is also observed that at 800ºC only 27% splitting tensile strength is retained for cases of no replacement of cement by GGBS.3. For 30% replacement case the performance in splitting tensile strength is poorest, if all temperatures are considered for comparison.3. 5 Studies on Cooling RegimesImportant results relating to loss in weight and loss in strength for two cooling regimes is presented and discussed.

3.5.1 Loss in weight of specimen Initial specimen weights were taken after 28 days of water curing. After exposure to various elevated temperatures and cooled

GGBS Level A-series(0%)

B-series(10%)

C-series(20%)

D-series(30%)

E-series(40%)

F-series(50%)

Room 1.00 1.00 1.00 1.00 1.00 1.00200 1.18 0.85 0.85 1.07 1.08 0.94400 0.83 0.56 0.75 0.67 0.80 0.78600 0.38 0.58 0.61 0.42 0.52 0.51800 0.27 0.33 0.36 0.33 0.39 0.33

Temperature

16TECH MANTRA

under different cooling regimes (furnace and sudden) the weights of the specimen were recorded to determine the percentage loss in weight.

Fig. 13 Variation in percentage loss in weight for exposure and cooled gradually in furnace and suddenly cooled regimesFrom Fig. 13, it is observed that for the case of furnace cooling, 69.1% of total weight loss occurs when exposed to 150 0C. The remaining 30.9% weight is lost, which is gradually with increments of 7% for temperature change of 150 0C to 250 0C, 17.6% for temperature change of 250 0C to 350 0C, 3% for temperature change of 3500C to 450 0C and 3.9% for temperature change of 450 0C to 550 0C.

From Fig. 13, it is observed that for the case of sudden cooling, 65.2% of total weight loss occurs when exposed to 150 0C. The remaining 34.8% weight is lost, gradually with increments of 6.0% for temperature change of 150 0C to 250 0C, 9.1% for temperature change of 250 0C to 350 0C, 7.6% for temperature change of 350 0C to 450 0C and 12.1% for temperature change of 450 0C to 550 0C.

3.5.2 Variation in residual compressive and split tensile strengths for different cooling regimes

Fig. 14 Variation in residual compressive strength for different cooling regimesFrom Fig. 14, it is observed that for furnace cooling the residual coeffi cient of compressive strength of cubes exposed to 150 0C is slightly higher by about 6% than that of cubes tested at normal room temperature. This is mainly because, at earlier elevated temperatures the moisture content in the cubes gets converted to vapour pressure, which contributed to the additional compressive strength than that of normal strength at room temperature as observed by Saava et.al (2005), Y Xu et.al (2003). This effect is called as autoclaving effect

On further increase of temperature there is loss in compressive strength gradually, as compared to strength at room temperature due to loss of moisture content and disintegration of hydrated cement paste. At 250 0C the residual coeffi cient of compressive strength is 0.95, and drops gradually to 0.84, 0.73 and 0.57 at elevated temperatures of 350 0C, 450 0C and 550 0C respectively for the furnace cooling which is gradual.

Further, for the case of sudden cooling, it is observed that the residual coeffi cient of compressive strength of cubes exposed to 150 0C is 0.86 and drops gradually to 0.81, 0.67, 0.53 and 0.39 at elevated temperatures of 250 0C, 350 0C, 450 0C and 550 0C.

The percentage differences between the two cooling regimes are 20, 14, 17, 20 and 18 respectively for 150 0C, 250 0C, 350 0C, 450 0C and 550 0C. On an average 20% change is reported for temperature of 350 0C and above.

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Fig. 15 Variation in residual split tensile strength for different cooling regimesFrom Fig. 15, it is observed that the residual coeffi cient of split tensile strength of cubes exposed to 1500C is 0.92 and drops gradually to 0.86, 0.76, 0.63 and 0.56 at elevated temperatures of 2500C, 3500C, 4500C and 5500C for the case of furnace cooling which is gradual.

Further, for the case of sudden cooling, it is observed that the residual coeffi cient of split tensile strength of cubes exposed to 1500C is 0.58 and drops gradually to 0.53, 0.45, 0.37 and 0.30 at elevated temperatures of 2500C, 350°C, 4500C and 5500C.

The percentage difference between the cooling regimes are 34, 33, 31, 26 and 26 respectively for 150°C, 250°C, 350°C, 450°C and 550°C. There is a decreasing variation from 50% to nearly 26% for temperature change of 150°C to 550°C.

4. CONCLUSIONS(i) It is observed that compressive strength of concrete increases with increase in percentage OPC replacement with GGBS up to 30%, and then on, the strength seemed to drop for the cases of room temperature.

(ii) It is noticed that at 800ºC temperature, all the fi ve levels of OPC replacement with GGBS have exhibited better temperature endurance properties in terms of residual compressive strength being much higher than that for the case of ambient temperature.

(iii) From the present investigation, it is observed that 50% replacement of OPC, has shown better performance in terms of strength at all levels of exposure.

(iv) Rate of loss in strength of concrete is highly dependent on the type of cooling regimes. The loss of compressive and split tensile strength is minimum under furnace cooling as the heat gradient is gradual and maximum under sudden cooling, as the thermal shock is sudden.

(v) The loss in compressive strength at 550°C, is 26% and 34% for the cooling regimes of furnace and sudden conditions respectively.

References

1. A. F. Bingol. and Rustem Gul, (2008), “Effect of elevated temperatures and cooling regimes on normal strength concrete”, Fire and Materials Vol.33, pp. 79-88.

2. A. M. K. Abdelalim and G.E.Abdel-Aziz, (2009), “Effect of elevated fi re temperature and cooling regime on the fi re resistance of normal and self-compacting concretes”, Engineering Research Journal, Vol. 122, pp. 63-81.

3. Chi-Sun Poon, Salman Azhar, Mike Anson and Yuk-Lung Wong, (2001), “Strength and durability recovery of fi re-damaged concrete after post-fi re-curing”, Cement and Concrete Research, 31, 1307–1318.

4. G J Osborne, (1998), “Durability of Portland blast furnace slag cement concrete”, Cement and Concrete Research Vol.21, Issue 3,, pp. 233-239.

5. IS: 10262-1982, “Recommended guidelines for concrete mix design” Bureau of Indian Standards, New Delhi.

6. Savva A, Manita P and Sideris K K, (2005), “Infl uence of elevated temperatures on the mechanical properties of blended cement concretes prepared with limestone and siliceous aggregates”, Cement and Concrete Composites, Vol. 27, 239–248.

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Interaction with Engineers & Participation in Exhibition

Dr Radhakrishnan IAS inaugurating our stall during the Engineers Conference

Mr Partha Chatterjee State Commerce and Industries Minister , West Bengal visiting our stall at

Science City , Kolkata

Dr C.S.Vishwanatha , Civil Aid Technolclinic Pvt Ltd at our stall during REDECON 2012 at Bangalore

Engineers from Bangalore visiting our Alathiyur Plant

Engineers visiting our stall at Salem

Stall of Madras Cements at Nandigram Polli Utsab – 2012, West Bengal

Engineers from Bangalore at our Research Centre- RRDC

Delegates from Association of Consulting Civil Engineers with RAMCO team at Mysore during the

Engineers conference

19TECH MANTRA

Dr.GanesanNIT – Kozhikode

I have gone through your Technical Magazine "TECHMANTRA" .It was covering a technical paper,brief details of your Ramco Research Development Centre and various articles and Ramco range of products. The details given are highly informative and useful to the engineers.The magazine was brought out nicely. The printing and photos are very good. In order to improvise further ,I suggest that you may consider including construction tips such as do's and don'ts which will be useful to the practicing engineers.

Dr. N Ganesan,Professor of Civil Engineering,National Institute of Technology, Calicut,

S.Thiagarajan Coromandel Engineering Company Ltd , Chennai

Today, we received your latest issue of TechMantra. It is an extremely informative magazine, and I am sure our Technical team will gain good knowledge on going through the same.S.ThiagarajanDeputy General Manager-HR & ADMINCoromandel engineering company limitedMurugappa GroupISO 9001:2008 & BS OHSAS 18001:2007 Certifi ed Company

Er Vijaya . V.Mayya, ChairmanAssociation of Consulting Civil Engineers , Mangalore

At the outset I would like to thank Madras Cements Ltd for their continued support by sponsoring our Engineers Day Celebration for the past several years . We would like to appreciate and congratulate for your attempt to empower the construction professionals through your knowledge and Technical based Magazine “ TechMantra”

Home Build Services , Panaji Goa

We have been using Ramco PPC since past few years and are very happy with the quality and service rendered . We would like to take this opportunity to congratulate Madras Cements team for coming out with the Technical Magazine TECHMANTRA benefi ting the construction professionals

Readers Feedback on TECHMANTRA

20TECH MANTRA

Sobha Developer –Bangalore Product used: Ramco Tilefi x

Projects Associated With RAMCO DryMix

Mahindra Tech City –Chennai Product used: Ramco superfi ne Putty

Provident wellworthcity-Bangalore Product used: Ramco plastering compound

Ritz Carlton Hotel-Bangalore Product used: Ramco Tilefi x

21TECH MANTRA

Projects Associated With RAMCO Cement

Lanco Highway project from Bangalore to Kolar built by Lanco Infrastructure Ltd where concrete grades

of M35 & above were used

Hirco group executing a project in Oragadam , Chennai

NCC Aster Park, Bangalore developed by NCC URBAN where concrete grades

of M25 & M30 were used

Project by Akshaya . Akshaya was founded in 1995 under the stewardship of Mr T. Chitty Babu

Dr M.G.R Educational and Research Institute University , one of the reputed universities in

Tamil Nadu

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Chennai Metro Rail Project whose part construction was handled by SOMA ENTERPRISES where RAMCO cement is approved

B.G.Shirke AWHO Project at Bangalore where concrete grades of M25 , M30 , M35 & above were used

Essar Project at Durgapur where our bulk cement from Kolaghat grinding unit is being used

Hyderabad Central University LANCO Hills , Hyderabad where concrete grades of M20 & above were used

23TECH MANTRA

MACE Division

Invitation for Articles to Tech Mantra

MOBILE VAN SERVICES FROM MACE DIVISION Our team of Civil Engineers will assist the customers in making a good quality concrete which also includes 1. Slump Cone testing for checking workability of concrete 2. Rebound Hammer test for evaluating the compressive strength of concrete 3. Concrete cube moulds for casting of concrete cubes

Cement Marketing Offices :Chennai : Tel : 044 28113838 / 28114477Madurai : Tel : 0452 2340981 / 2343559Trichy : Tel : 0431 2741937 / 2740131Salem : Tel : 0427 2334215 / 17Coimbatore : Tel : 0422 2552030 / 31Bangalore : Tel : 080 41226500 / 01 / 03Mysore : Tel : 0821 2562717 / 2463217Mangalore : Tel : 0824 2429292 / 9900016130Hyderabad : Tel : 040 23119271 / 72 / 8106018518

We invite technical articles in the fi eld of Civil Engineering, preferably in cement & Concrete technologyArticles in soft copy can be sent to akp@madrascements.co.in

PLEASE CONTACT OUR TOLL FREE NO : 1800 4255 700OR

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President (Marketing) is seen fl agging off the MACE vans Vice President (Marketing) addressing the gathering during the inaugurals of MACE vans