a study on high strength self compacting concrete on exposure to various temperatures

57

International Journal of Research and Innovation (IJRI)

International Journal of Research and Innovation (IJRI)A STUDY ON HIGH STRENGTH SELF COMPACTING CON-

CRETE ON EXPOSURE TO VARIOUS TEMPERATURES

A.Swetha 1, K. Mythili2,

1 Research Scholar, Department Of Civil Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India2 Associate Professor, Department Of Civil Engineering, Aurora's Scientific Technological & Research Academy,Hyderabad, India

*Corresponding Author: A.Swetha, Research Scholar, Department of CIVIL Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India Published: October 27, 2014Review Type: peer reviewedVolume: I, Issue : II

Citation:A.Swetha , (2014) A Study On High Strength Self Com-pacting Concrete On Exposure To Various Temperatures

INTRODUCTIONGENERAL

Concrete is one of the most extensively used con-struction materials in the world, with about two billion tons of utilization worldwide each year. It is attractive in many applications because it offers considerable strength at a relatively low cost. Con-crete can generally be produced of locally available constituents, can be cast in to wide variety of struc-tural configurations and requires minimal mainte-nance during service. However, environmental con-cerns, stemming from high-energy expense and CO2 emission associated with cement manufacture, have brought pressures to reduce consumption through the use of supplementary materials.

In general, concrete is said to be a very durable one. But when Reinforced Concrete structure is subject-

ed to severe environmental conditions, its properties are affected adversely depending on the type of ex-posure. Durability is one the most important prop-erties to be considered in the design of Reinforced Concrete structures exposed to aggressive environ-ments which can be described by two stages: the initiation and the propagation period. Increasing the concrete strength is always one of the main desires of Concrete Technology. Since more than 20 years High Strength concretes with com-pressive strength ranging from 50 N/mm2 to 130N/mm2 have been used worldwide in tall buildings and bridges with long spans or buildings in aggres-sive environments. Building elements made of High Strength concrete are usually densely reinforced. The small distance between reinforcing bars may lead to defects in concrete. If High Strength con-crete is self-compacting, the production of dense-ly reinforced building element from High Strength concrete with high homogeneity would be an easy work. Self-compacting concrete is a concrete that flows and compacts only under gravity. It fills the whole mould completely without any defects. The usual self-compacting concretes have a compres-sive strength in the range of 60-100N/mm2.

Self Compacting Concrete (SCC):

Placement of concrete generally requires consolida-

Abstract

The extensive use of concrete as a structural material for the high rise buildings, storage tanks, nuclear reactors and pressure vessels increase the risk of concrete being exposed to high temperatures. This has led to a demand to improve the understanding of the effect of temperature on concrete. The behavior of concrete exposed to high temperature is a result of many factors including the exposed environment and constituent materials.Concrete structures are exposed to fire when a fire accident occurs. Damage in concrete structures due to fire depends to a great extent on the intensity and duration of fire. The distress in concrete manifests in the form of cracking and spalling of concrete surface.The main aim of the present experiment investigation is to study the behavior of High Strength Self Compacting Con-crete when subjected to elevated temperatures. High Strength Self Compacting Concrete specimens made with Cement, Micro Silica, Quartz Sand, Quartz Power and Basalt of size 2 to 5 mm and Chemical Admixtures.In the present investigation, tests were conducted on Concrete Specimens by exposing them at different temperatures like 2000 C, 4000 C and 6000 C at 4 hours, 8 hours and 12 hours duration. After 28 days curing the specimens are tested for Compressive Strength, Split Tensile Strength, Percentage Weight Loss and Non Destructive Test to measure velocity of Concrete.Based on the study, conclusions were made that High Strength Self Compacting Concrete with the above materials not able to resist temperature of 6000 C and above.

1401-1402

58


tion by vibration in the forms. Self compacting Con-crete (SCC) can be defined as the “highly flowable concrete yet stable concrete that can spread readily into place and fill the formwork without any con-solidation and without undergoing any significant separation”( Khayat, Hu and many, proceeding first international RILEM symposium, SCC Stockholm 1999).An alternative specification suggest SCC as a “flowing concrete without segregation and bleeding, capable of filling spaces and dense reinforcement or inaccessible voids without hindrance or blockage.

Self compacting concrete was first developed in 1986 in Japan to achieve durable concrete struc-ture since then, various investigations have been carried out this type of concrete has been used in practical structures in Japan, mainly by large con-struction companies.The first usable self compacting concrete was com-pleted in 1988 and was named “High performance concrete” and later proposed as “Self compacting high performance concrete’. This leads to develop-ments of self compacting concrete. Self compacting concrete has been described as “The most revolu-tionary development in concrete construction for several decades” originally developed to offset a growing shortage of skilled labour, it has proved beneficially economically.

Self compacting concrete a new kind of high perfor-mance concrete (HPC) excellent deformability and segregation resistance, it is a special kind concrete than can flow through and fill the gaps of reinforce-ment and corners of molds without any need for vi-bration and compaction during the pacing process. Through showing good performance, self compact-ing concrete is different from the HPC developed in North America and Europe, which emphasizes on high and durability of concrete. In terms of work-ability, HPC merely improved fluidity of concrete to facilitate placing: however it cannot flow freely by itself to pack every corner of molds and all gaps among reinforcement. In other words HPC still re-quires vibration and compaction in the construction process. Comparatively self compacting concrete has more favorable characteristics such as high flu-idity, good segregation resistance and the distinc-tive self compacting ability without any need for vi-bration during the placing process.

BENEFITS AND ADVANTAGES OF SCC:

•Modern, presently self compacting concrete (self compacted concrete) can be classified as an ad-vanced construction material. The self compacting concrete as the name suggests, does not require to be vibrated to achieve full compaction. This many benefits and advantages over conventional concrete.

•Improved quality of concrete and reduction of onsite repairs.•Faster construction times.

•Lower overall costs.

•Facilitation of introduction of automation into con-crete construction.

•Better surface finishes.

•Easier placing.

•Thinner concrete sections.

•Greater freedom in design.

•Improved durability and reliability of concrete structures.

•Easy of placement results in cost savings through reduced equipment and labour requirement.

High Performance Concrete:

Long-term performance of structures has become vital to the economies of all nations. Concrete has been the major instrument for providing stable and reliable infrastructure since the days of the Greek and Roman civilization. Deterioration, long term poor performance and inadequate resistance to hostile environment coupled with greater demands for more sophisticated architectural form, led to the accelerated research into the microstructure of cements and concretes and more elaborate codes and standards. As a result, new materials and composites have been developed and improved ce-ments evolved. Today concrete structures with a compressive strength exceeding138 Mpa are being built world over. In research laboratories, concrete strengths of even as high as 800 Mpa are being pro-duced. One major remarkable quality in making of High Performance Concrete (HPC) is the virtual elimination of voids in the concrete matrix which are mainly the cause of most of the ills that generate deterioration.

Advantages of High Performance Concrete:

The advantages of using high strength high perfor-mance concretes often balance the increase in ma-terial cost. The following are the major advantages that can be accomplished.1.Reduction in member size, resulting in increase in plinth area/useable area and direct savings in the concrete volume.2.Reduction in the self-weight and super-imposed DL with the accompanying saving due to smaller foundations.3.Reduction in form-work area and cost with the ac-companying reduction in shoring and stripping time due to high early-age gain in strength.4.Construction of High-rise buildings with the ac-companying savings in real-estate costs in congest-ed areas.5.Longer spans and fewer beams for the same mag-nitude of loading.6.Reduced axial shortening of compression sup-porting members.

59


7.Reduction in the number of supports and the sup-porting foundations due to the increase in spans.8.Reduction in the thickness of floor slabs and sup-porting beam sections which are a major component of the weight and cost of majority of structures.9.Superior long-term service performance under static, dynamic and fatigue loading.10.Low creep and shrinkage.11.Greater stiffness as a result of a higher modulus (Ec).12.Higher resistance to freezing and thawing, chem-ical attack, and significantly improved long-term durability and crack propagation.13.Reduced maintenance and repairs.14.Smaller depreciation as a fixed cost.

Aim of the Present Study:

The Aim of the Present Study is to investigate the Compressive Strength and Split Tensile Strength of High Strength Self Compacting Concrete when subjected to elevated temperatures. To investigate the effect of temperature and to evaluate structural safety, an attempt has been made to study the Com-pressive Strength.The study concentrates mainly on the properties of Compressive Strength of High Strength Self Compacting Concrete for a particu-lar water binder (w/b) ratio at 2000C, 4000C and 6000C.

In the present investigation, the tests were con-ducted for a total of 180 specimens on a particular w/b ratio by exposing them at different tempera-tures like Room Temperature, 2000C, 4000C and 6000C for 4 Hours, 8 Hours and 12 Hours duration. The results indicate that the High Performance Self Compacting Concrete is effective in resisting the ef-fect of temperature on the compressive strength. The main aim of the present experiment investiga-tion is to study the behavior of High Strength Self Compacting Concrete when subjected to elevated temperatures.

High Strength Self Compacting Concrete speci-mens made with Cement, Micro Silica, Quartz sand, Quartz Powder, Basalt of size 2 to 5 mm and Chemi-cal Admixtures.

In the present investigation tests were conducted on Concrete specimens by exploring that at differ-ent temperatures like 2000C, 4000C and 6000C for 4 Hours, 8 Hours and 12 Hours duration after 28 days curing. The specimens are tested for Com-pressive Strength, Split Tensile Strength , % Weight Loss and Non Destructive Test to measure Velocity of Concrete.

Based on the study, conclusions were made that High Strength Self Compacting Concrete with the above materials was not able to resist temperature of 6000C and above.

EXPERMENTAL INVESTIGATION

GENERAL:

The present investigation is a study of the concrete compressive strength, Split tensile strength and % reduction in weight of concrete for High Strength Self compacting concrete when subjected to elevat-ed temperatures of 2000C, 4000C, and 6000C. This was planned to be carried out through an experi-mental program on concrete specimens of size 100 x 100 x 100 mm cubes and 100 x 200 mm cylinders for compressive strength and split tensile strength. The test specimens were de-moulded 4 hrs of air cooling and kept for water curing for 28 days. The standard specimens after curing period were placed in muffle furnace at requisite temperature of 2000C, 4000C and 6000C at 4 hrs, 8 hrs and 12 hrs duration.

After the specimen removed from the furnace, the specimens were allowed to cool in air for 2 hrs. Then the specimens were tested for NDT, compres-sive strength, split tensile strength, the results were tabulated & required comparative study was made.The objective of the experimental study that was conducted is given below.

1)To study the pulse velocity (m/sec) at 28 days at Room, Temperature, 2000C, 4000C and 6000C expo-sure at 4hrs, 8 hrs and 12 hrs duration.2)To study the percentage weight loss at 28 days at Room Temperature, 2000C, 4000C and 6000C expo-sure at 4hrs, 8 hrs and 12 hrs duration.3)To study the Compressive strength and Split ten-sile strength ( Mpa) at 28 days at Room Tempera-ture, 2000C, 4000C and 6000C exposure at 4hrs, 8 hrs and 12 hrs duration.

Materials used:

The materials that are used in this study are:•Cement•Fine aggregate (Quartz sand) •Quartz Powder•Coarse aggregate (Crushed basalt)•Super plasticizer•VMA•Water

CementOrdinary Portland cement of 53 grade available in local market is used in the investigation. The ce-ment used has been tested for various proportions as per IS 4031 – 1988 and found to be confirming to various specifications of IS 12269-1987. The specif-ic gravity was 3.15 and fineness was 2800 cm2/gm. In the experimental investigations ordinary Port-land cement i.e., I.S Type cement of 53 grade is used. Care to be taken that it is made from a single source and fine grained and is stored in an airtight container to prevent it from the atmospheric mois-ture and humidity.

60


Properties of Quartz powder and Quartz sand:

Name SiO2 TiO2 Fe2O3 Al2O3 CaO MgO Loss on Igni-tion

Per-centage 99.24 Absent 0.04 0.12 0.28 Absent 0.06

Pictures of Quartz sand and Quartz powder

Coarse aggregate (Crushed basalt 2 to 5mm)

Basalt comes from extensive lava flows. Basalt is a very common igneous rock and the most com-mon rock in the Earth's crust. Almost all oceanic crust is made of Basalt and it is a common extru-sion from many volcanic regions around the world. It forms from the melting of the upper mantle and its chemistry closely resembles the upper mantle's composition. It is generally Silica poor and Iron and Magnesium rich. Basalt originates from "hot spot" volcanoes, massive basalt flows and mid oceanic ridges.In present investigations crushed basalt is used with size varying from 2 - 5 mm.

V-Funnel Test Apparatus

The average flow through speed, Vm, is calculated in terms of the flow through time, t0;

To quantify segregation resistance, the flow-through index, Sf, is calculated in terms of initial flow through time, t0, and the flow through time after 5 minutes, t5:

Slump Flow Test:

The simplest and most widely used test method for self-compacting concrete is the slump flow test (Kuroiwa et al. 1993; EFNARC 2002; Bartos, Sonebi, and Tamimi 2002). The test, which was developed in Japan, was originally used to measure underwater concrete and has also been used to measure highly flowable concretes. To perform the test, a conven-tional slump cone is placed on a rigid, non-absor-bent plate and filled with concrete without tamping. The plate must be placed on a firm, level surface. The slump cone is lifted and the horizontal spread of the concrete is measured. For an additional meas-ure of flowability, the time required for the concrete to spread to a diameter of 50 cm can be measured. The slump flow was used to assess the horizontal free flow and the falling ability in the absence of ob-structions. The recommended slump range was 650 to 800 mm. This value of T50 generally ranges from 2-7 seconds. It is possible to assess the stability of concrete qualitatively after performing the slump flow test. A visual stability index(VSI) has been de-veloped as a standard means of determining stabil-ity. A numerical score on a scale of 0 to 3 is assigned based on a visual evaluation of the segregation and bleeding in the concrete sample. Self-compacting concrete should exhibit a rating of 0 or 1 to be con-sidered acceptable.

L-Box Test:

The L-box test (EFNARC 2002; Bartos, Sonebi, and Tamimi 2002) measures the filling and passing abil-ity of self-compacting concrete. Originally devel-oped in Japan for underwater concrete, the test is also applicable for highly flowable concrete. As the test name implies, the apparatus consists of an L-shaped box.

L-Box Test Apparatus

Casting

For casting the cube and cylinder specimens, stand-ard cast iron metal moulds of size 100 x 100 x 100 mm and 100 x 200 mm were used. The moulds were cleaned from adhering dust particle and oiled on all sides, before concrete is poured into. Thoroughly mixed concrete was filled in moulds.

Curing

After casting, the specimens were stored in the labo-ratory free of vibrations in moist air at room tem-

Sf = ts t0

t0

Vm

0.01(0.065x0.075)xt0

= = 2.05t0

(m/s)

61


perature for 24 hrs. After this period, the specimens were removed from the mould and immediately im-mersed in clean, fresh water curing tank. The above climate was maintained for 28 days.

Testing of Specimens:

A time schedule for testing of specimens is main-tained to ensure their proper testing on the due date and time. The cast specimens are tested as per standard procedures, immediately after they are re-moved from curing pond and wiped off the surface water. The test results are tabulated carefully

Description of Compression Testing Machine

The compression testing machine (Microproces-sor based) used for testing the cube specimens is of standard make. The capacity of the testing ma-chine is 200 Tonnes or 2000 KN. The machine has an ideal gauge on which the load applied can be read directly. The oil level is checked, the MS plates are cleaned and the machine is kept ready for test-ing specimens.

Ultra Pulse Velocity apparatus

This determines the velocity of longitudinal waves. The determination consists of measurement of the time taken by a pulse, hence the name of the meth-od to travel a measured distance. The apparatus in-clude transducers which are placed in contact with the concrete, a pulse generator with a frequency of between 10 and 150 Hz, an amplifier a time meas-uring circuit and a digital display of the time taken by the pulse of longitudinal waves to travel between the transducers. The test method is prescribed by ASTM C 597 – 83 and by BS 1881:203:1986.

EXPERIMENTAL RESULTS

GENERAL:

In the present study, investigations are carried out to study the effect of elevated temperatures on High strength self compacting concrete.

Properties of Micro SilicaTypical Oxide Composition of Micro Silica (Oriental Trexim Pvt Ltd)

Sl. No: Constituents Percentage

1 Silica, Sio2 92.00

2 Alumina, A12O3 0.46

3 Iron Oxide, Fe2O3 1.60

4 Lime, CaO 0.36

5 Magnesia, MgO 0.74

6 Sulphur Trioxide, SO3 0.35

7 Loss on ignition 2.50

8 Na2O 0.70

9 K2O 0.90

10 pH 7.60

11 Accelerated Pozzolonic Acidity index in 7 days 104.00

12 Accelerated Pozzolonic Acidity index in 28 days 117.00

13 Surface Area m2/kg 1890

14 Moisture Content 1.00

15 Bulk Density 450-650

Quantities of Materials required per 1m3 of High Strength Self Compacting Concrete

Sl. No: Material Weight (Kg)1 Crushed basalt-2 to 5mm 10222 Quartz Sand (3 to 8 μm) 4373 Quartz Powder (0 to 10 μm) 2024 Micro Silica 1425 Cement 4726 Water 175 lt7 Super Plasticizer 14688 ml8 VMA 816 ml

9Water /(cement + Micro Silica + Quartz Powder) 0.215

Workability of High Strength Self Compacting Concrete

Test method MixPermissible limits as per EFNARC

GuidelinesMin Max

V-Funnel 9.7 sec 6 sec 12 secV-Funnel at T5

min 13.85 sec 11 sec 15 sec

Abrams slump flow 690 mm 650 mm 800 mm

T 50cm slump flow 4 sec 2 sec 5 sec

L- Box

0.9 0.82 1.01 sec 1 sec 2 sec

2 sec 2 sec 3 sec

Details of specimens to be tested for elevated tem-perature of HPSCC

62


Strength point of view no”.of cubes required

Sl. No

Size of the cube

No. of days (all 28 days)No.of cubesRoom

temp4

hrs8

hrs12 hrs

1(a)

100 x 100 x 100 mm

cubes (Compressive

strength) – 2000 C

3 3 3 3 12

1(b)

100 x 100 x 100 mm

cubes (Compressive

strength) - 4000 C

- 3 3 3 9

1(c)

100 x 100 x 100 mm

cubes (Compressive

strength) - 6000 C

- 3 3 3 9

2(a)

150 x 300 mm cylinders (Split tensile strength) -

2000 C

3 3 3 3 12

2(b)


4000 C

- 3 3 3 9

2(c)


6000 C

- 3 3 3 9

Compressive Strength of High Strength Self Com-pacting Concrete for 28 days at Room Temperature and 2000 C at 4, 8, 12 hours duration.

S.no:Water / Binder Ratio

Compressive Strength (N/mm2)Duration

Room Tempera-

ture

4 Hours

8 Hours

12 Hours

10.215

82.57 77.68 74.68 72.582 84.69 80.59 76.59 74.553 83.59 76.62 73.62 71.68

Compressive Strength of High Strength Self Com-pacting Concrete for 28 days at Room Temperature and 4000 C at 4, 8, 12 hours duration.

S.no:Water / Binder Ratio


Room Tempera-

ture

4 Hours

8 Hours

12 Hours

10.215

82.57 68.68 66.58 61.952 84.69 71.68 67.02 64.653 83.59 68.02 66.02 63.52

Compressive Strength of High Strength Self Com-pacting Concrete for 28 days at Room Tem-perature and 6000 C at 4, 8, 12 hours duration.

S.no:

Water / Binder Ratio


Room Tem-pera-ture

4 Hours 8 Hours 12 Hours

10.215

82.57 Crushed Crushed Crushed2 84.69 Crushed Crushed Crushed3 83.59 Crushed Crushed Crushed

Percentage Decrease of Compressive Strength of High Strength Self Compacting Concrete at 2000 C at 4, 8, 12 hours duration with respect to 28 days compressive strength

S.no:


Percentage Decrease of Compressive Strength Duration

4 Hours 8 Hours 12 Hours1

0.2155.92 9.56 12.10

2 4.84 9.56 12.003 8.34 11.90 14.20


S.no:




0.21516.80 19.40 25.00

2 15.40 20.90 23.703 18.60 21.00 24.00


63


S.no:




0.215Crushed Crushed Crushed

2 Crushed Crushed Crushed3 Crushed Crushed Crushed

Percentage Weight Loss of High Strength Self Com-pacting Concrete at 2000 C at 4, 8, 12 hours dura-tion with respect to 28 days compressive strength

S.no:


Percentage Weight LossDuration


0.2151.58 2.29 3.27

2 1.60 1.96 3.293 0.79 2.43 4.07

Percentage Weight Loss of High Strength Self Com-pacting Concrete at 4000 C at 4, 8, 12 hours dura-tion with respect to 28 days compressive strength.

S.no:




0.2154.86 7.31 7.98

2 3.92 8.16 9.963 6.35 5.91 8.30

Percentage Weight Loss of High Strength Self Com-pacting Concrete at 6000 C at 4, 8, 12 hours dura-tion with respect to 28 days compressive strength.

S.no:




0.215Crushed Crushed Crushed

2 Crushed Crushed Crushed3 Crushed Crushed Crushed

Pulse Velocity of High Strength Self Compacting Concrete for 28 days at Room Temperature and 2000 C at 4, 8, 12 hours duration.

S.no:


Pulse Velocity (m/sec)Duration

Room Tem-pera-ture


10.215

4430 4270 4220 42002 4370 4290 4130 42003 4430 4390 4200 4290

Pulse Velocity of High Strength Self Compacting Concrete for 28 days at Room Temperature and 4000 C at 4, 8, 12 hours duration.

S.no:



Room Tem-pera-ture


10.215

4430 3900 3800 34702 4370 4090 3690 33903 4430 4050 3500 3250

Pulse Velocity of High Strength Self Compacting

EXPERIMENTAL PHOTOGRAPHS

Quartz Sand Quartz Powder

64


Basalt Pan Mixer

V-Funnel Test Testing of Split Tensile Strength Specimen

specimen of Split Tensile Strength after Test Strength Concrete Specimen in Compression Testing Machine

65


Concrete for 28 days at Room Temperature and 6000 C at 4, 8, 12 hours duration.

S.no:



Room Tem-pera-ture


10.215

4430 Crushed Crushed Crushed2 4370 Crushed Crushed Crushed3 4430 Crushed Crushed Crushed

DISCUSSION OF TEST RESULTS

Compressive Strength of High Strength Self Com-pacting Concrete exposure to 2000 C for 4, 8 & 12 hours duration.

Table 4.4.13 and Graph 1 show the compressive strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours duration at 2000 C. The Compressive Strength of High Strength Self Compacting Concrete for 4 hours exposure are 77.68, 80.59 and 76.62 N/mm2 ; 8 hours exposure are 74.68, 76.59 and 73.62 N/mm2 and 12 hours exposure are 72.58, 74.55 and 71.68 N/mm2.


Table 4.4.13 and Graph 1 show the compressive strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours duration at 4000 C. The Compressive Strength of High Strength Self Compacting Concrete for 4 hours exposure are 68.68, 71.68 and 68.02 N/mm2 ; 8 hours exposure are 66.58, 67.02 and 66.02 N/mm2 and 12 hours exposure are 61.95, 64.65 and 63.52 N/mm2.


Table 4.4.13 and Graph 1 show the compressive strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours duration at 6000 C. All the specimens are exposed to 6000 C at 4, 8 & 12 hours duration. All the specimens are crushed and entire concrete became powder material. Hence the concrete is not able to take 6000 C temperature.

Percentage decrease of Compressive Strength of High Strength Self Compacting Concrete exposure to 2000 C for 4, 8 & 12 hours duration.

Table 4.4.14 and Graph 2 show the Percentage de-crease of compressive strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours duration at 2000 C. The Compressive Strength of High Strength Self Compacting Concrete for 4 hours exposure are 5.92, 4.84 and 8.34 N/mm2 ; 8 hours exposure are 9.56, 9.56 and 11.90 N/mm2 and 12 hours exposure are 12.10, 12.00 and 14.20 N/mm2.

Percentage decrease of Compressive Strength of High Strength Self Compacting Concrete exposure to 4000 C for 4, 8 & 12 hours duration.

Table 4.4.14 and Graph 2 show the Percentage de-crease of compressive strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours duration at 4000 C. The Compressive Strength of High Strength Self Compacting Concrete for 4 hours exposure are 16.80, 15.40 and 18.60 N/mm2 ; 8 hours exposure are 19.40, 20.90 and 21.00 N/mm2 and 12 hours exposure are 25.00, 23.70 and 24.00 N/mm2

Percentage decrease of Compressive Strength of High Strength Self Compacting Concrete exposure to 6000 C for 4, 8 & 12 hours duration.Table 4.4.14 and Graph 2 show the Percentage de-crease of compressive strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours duration at 6000 C. All the specimens are exposed to 6000 C at 4, 8 & 12 hours duration. All the specimens are crushed and entire concrete became powder material. Hence the concrete is not able to take 6000 C temperature.

Percentage Weight Loss of Compressive Strength of High Strength Self Compacting Concrete exposure to 2000 C for 4, 8 & 12 hours duration.

Table 4.4.15 and Graph 3 show the Percent-age Weight Loss of Compressive Strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours du-ration at 2000 C. The Compressive Strength of High Strength Self Compacting Concrete for 4 hours exposure are 1.58, 1.60 and 0.79 N/mm2 ; 8 hours exposure are 2.29, 1.96 and 2.43 N/mm2 and 12 hours exposure are 3.27, 3.29 and 4.07 N/mm2.


Table 4.4.15 and Graph 3 show the Percent-age Weight Loss of Compressive Strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours du-ration at 4000 C. The Compressive Strength of High Strength Self

66


Compacting Concrete for 4 hours exposure are 4.86, 3.92 and 6.35 N/mm2 ; 8 hours exposure are 7.31, 8.16 and 5.91 N/mm2 and 12 hours exposure are 7.98, 9.96 and 8.30 N/mm2.


Table 4.4.15 and Graph 3 show the Percent-age Weight Loss of Compressive Strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours du-ration at 6000 C.

All the specimens are exposed to 6000 C at 4, 8 & 12 hours duration. All the specimens are crushed and entire concrete became powder material. Hence the concrete is not able to take 6000 C temperature.

Pulse Velocity (m/sec) of High Strength Self Com-pacting Concrete for 28 days at Room Temperature and 2000 C at 4, 8, 12 hours duration

Table 4.4.16 and Graph 4 show the Pulse Velocity (m/sec) of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours duration at 2000 C.

The Pulse Velocity of High Strength Self Compacting Concrete for 4 hours exposure are 4270, 4290 and 4390 m/sec ; 8 hours exposure are 4220, 4130 and 4200 m/sec and 12 hours exposure are 4200, 4200 and 4290 m/sec.







Split Tensile Strength of High Strength Self Com-pacting Concrete exposure to 2000 C for 4, 8 & 12 hours duration.

Table 4.5.12 and Graph 5 show the Split Tensile Strength of High Strength Self Compacting Con-crete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours duration at 2000 C.

The Split Tensile Strength of High Strength Self Compacting Concrete for 4 hours exposure are 7.25, 7.48 and 7.43 N/mm2 ; 8 hours exposure are 6.99, 7.22 and 7.32 N/mm2 and 12 hours exposure are 6.87, 7.08 and 7.07 N/mm2.







Percentage decrease of Split Tensile Strength of High Strength Self Compacting Concrete exposure to 2000 C for 4, 8 & 12 hours duration.

Table 4.5.13 and Graph 6 show the Percentage de-crease of Split Tensile strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours duration at 2000 C. The Split Tensile Strength of High Strength Self Compacting Concrete for 4 hours exposure are 0.96, 3.73 and 4.01 N/mm2 ; 8 hours exposure are 4.51, 7.08 and 5.43 N/mm2 and 12 hours exposure are 6.15, 8.88 and 8.66 N/mm2.


Table 4.5.13 and Graph 6 show the Percentage de-

67


crease of Split Tensile Strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours duration at 4000 C.

The Split Tensile Strength of High Strength Self Compacting Concrete for 4 hours exposure are 7.10, 10.04 and 10.21 N/mm2 ; 8 hours exposure are 8.61, 11.58 and 11.89 N/mm2 and 12 hours ex-posure are 14.75, 16.47 and 16.15 N/mm2.


Table 4.5.13 and Graph 6 show the Percentage de-crease of Split Tensile Strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours duration at 6000 C.


Percentage Weight Loss of Split Tensile Strength of High Strength Self Compacting Concrete exposure to 2000 C for 4, 8 & 12 hours duration.

Table 4.5.14 and Graph 7 show the Percent-age Weight Loss of Split Tensile Strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours du-ration at 2000 C.


Percentage weight loss of High Strength Self Com-pacting Concrete Specimen of Split Tensile Strength exposure to 4000 C for 4, 8 & 12 hours duration.

Table 4.5.14 and Graph 7 show the Percent-age Weight Loss of Split Tensile Strength of High Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours du-ration at 4000 C.


Percentage Weight Loss of High Strength Self Com-pacting Concrete Specimen of Split Tensile Strength exposure to 6000 C for 4, 8 & 12 hours duration.

Table 4.5.14 and Graph 7 show the Percent-age Weight Loss of Split Tensile Strength of High

Strength Self Compacting Concrete for water binder ratio 0.215 after exposure to 4, 8 and 12 hours du-ration at 6000 C.


Pulse Velocity (m/sec) of High Strength Self Com-pacting Concrete Specimen of Split Tensile Strength for 28 days at Room Temperature and 2000 C at 4, 8, 12 hours duration









CONCLUSIONS

The following conclusions are drawn from the Ex-perimental Investigation in present Thesis:

1)The percentage decrease of compressive strength was found higher for higher exposure time.

68


2)A gradual reduction in strength was found with increase in temperature from 200 to 6000C for all exposure duration of 4, 8 and 12 hours.

3)The percentage decrease of weight loss was found higher for higher exposure times.

4)The pulse velocity of High Strength Self Compact-ing Concrete was found lower for higher exposure time.

5)The specimens when exposed to 6000C for 4, 8, 12 hours duration, all the specimens got totally pow-dered at this temperature.

6)High Strength Self Compacting Concrete speci-mens exhibited maximum percentage decrease of compressive strength of nearly 24% at 4000C for 12 hours duration.

7)High Strength Self Compacting Concrete speci-mens exhibited maximum percentage weight loss of 9% at 4000C for 12 hours duration.

8)High Strength Self Compacting Concrete speci-mens exhibited maximum percentage decrease of split tensile strength of nearly 15% at 4000C for 12 hours duration.

9)The Pulse Velocity of High Strength Self Compact-ing Concrete specimens after exposure at 4000C for 12 hours duration is 3470 m/Sec to 3290m/Sec

SCOPE OF FUTURE STUDIES

1.Investigation can be made with the addition of Glass Fibres to know Residual Strength of High Strength Self Compacting Concrete.

2.Study can be made on High Strength Self Com-pacting Concrete specimens by exposing concrete to longer duration.

3.A time dependent study can be made to know about the long term behavior of High Strength Self Compacting Concrete.

REFERENCES

1.Castilo, C and Durrani A J (1990) Effect of transient high tem-perature on High strength Concrete, ACI Materials Journal, Jan- February 1990, pp 47-53.

2.Chakrabarti. S.C., Sharma. K.N., AND Abha Mittal., “Residual Strength in Concrete after exposure to elevated temperature”. The Indian Concrete Journal, December 1994 PP 713-717. 3.EFNARC, “Specifications and guidelines for self compacting concrete”, www.efnarc.org.

4.George C. Hoff etal (2000) elevated temperature effects HSC residual strength, Concrete International, April 2000, pp 41-47.

5.Hajime Okamura and Masahiro Ouchi (2003) “Self-Compact-ing Concrete”, Journal of Advanced Concrete Technology, Japan Concrete Institute, Vol.1, pp. 5-15.

6.Janotka, Nurnbergurora T (1990), Thermo-Mechanical proper-

ties of PENLY reactor envelop at temperatures up to 200oC, Ma-terials and structures Vol.32, December 1999, pp 719-726.

7.Klaus Holschemacher and Y Vette Klug, Leipzig “A Database for the Evaluation of Hardened properties of SCC” (Pages from 123-134).8,Long T. Phan and Nicholas J.Carino “Effects of test Conditions and Mixture proportions on Behavior of High Strength concrete Exposed to High Temperatures”, ACI Materials Journal, January- February 2002 PP 54-62.

9.Manu Santhanam and Subramaniam S. (2004) “current devel-opments in Self Compacting Concrete”, Indian Concrete Journal, June, Vol., pp 11-22.

10.Mohammed Bhai, G.T.G., “The residual strength of Concrete subjected to elevated temperature”, Concrete Journal, Vol.17, No.12, 1983, PP 22-27. 11.“Self Compacting Concrete”, Indian Concrete Journal, Au-gust, pp. 1261-1266.

12.Srinivasa Rao K, Potha Raju M. & Raju P.S.N “Effect of age on HSC on Residual Compressive Strength under Elevated temper-atures”, International conference on Advances in Concrete and Construction, December 2004, PP 733-741. 13.Srinivasa Rao K, Potha Raju M. & Raju P.S.N “Effect of Elevat-ed temperature on compressive strength on HSC made with OPC & PPC”, The Indian Concrete Journal, August 2006, PP 43-48. 14.Srinivasa Rao. P, Sravana. P and Seshagiri Rao. M.V. “Effect of Thermal cycles on Strength Properties of OPC and fly ash con-cretes”, the Indian Concrete Journal, March, 2006, PP 49-52.

Timo Wusthloz “Fresh properties of SCC” (Pages from 179-188)

AUTHOR

A.Swetha, Research Scholar, Department of CIVIL Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India

K. Mythili,AssociateProfessor,Department of CIVIL Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India

a study on high strength self compacting concrete on exposure to various temperatures

Education