Development of Ternary blends for High Performance Concrete

Deepa A Sinha Dr. A K Verma Dr K B Prakash Associate Professor, Dept. Professor& Head, Principal,Structural Engg. Dept. Structural Engg.v Dept. Govt Engg College BVM Engg. College, V V Nagar BVM Engg. College, V V Nagar Vidyanagar, Haveri,KarnatakaEmail:deepa_sinha_98@yahoo.co.in Email:akvbvm@yahoo.co.in

Abstract- Mineral admixtures have changed the concept of making durable and special concretes in last four decades.Metakaolin has been researched world wide and have been found to be a product equivalent to silica fume in reactivity. India has large reserves of kaolin and there are about half a dozen companies who process this mineral for various applications. During the last couple of years good quality metakaolin is made available for use as cement replacement in construction industry. A good amount of research work is also reported on the applications leading to beginning of use of metakaolin in cement mortar and concrete. In the present experimental investigation compressive, tensile and flexural strength of plain concrete and steel fiber reinforced the concrete with corrugated fibres with different ternary blends are compared. The concrete mixed used for casting the cube, cylinder and beam specimen is 1: 1.86 : 2.41 by weight and a water cement ratio as 0.45. The corrugated stewol steel fibres of 30 mm length and 0.7mm thickness with 42 as the aspect ratio at 1% volume fraction are incorporated in the concrete with 0.78 % super plasticizer[3]

I. INTRODUCTIONDuring the past few decades, the potential of Portland

cement in terms of its effective utility has been realized. As a result, the use of new admixtures has increased significantly within the concrete industry. Availability of mineral admixtures marked the opening of a new era for designingconcrete mix of higher and higher strengths. However it was experienced, and hence realised, over a period of time, that it was not only the strength that is important, other attributes of concrete, such as durability, workability etc. were also vital performance parameters. This has led to the work, which was initially limited to high strength concrete (HSC), then extended to high performance concrete (HPC). HPC mix is designed with mineral and chemical admixtures along with other normal ingredients of concrete, having a low watercementitious ratio. Mineral admixtures are added to concrete in relatively varying quantities, generally in the range 5 to 40 % by weight of portland cement, depending on its type and requirements. Practical experience has revealed that addition of mineral admixtures to concrete reduces heat of hydration due to reduced cement content, and increases durability by contributing to pore refinement. Mineral admixtures can be broadly divided into two groups: the reactive type and the inert type. The latter has no cementitious value, which the first

type has. The first type is further categorised into cementitious materials such as ground granulated blast furnace slag (GGBS), and pozzolans or supplementary cementitious materials (SCM) such as fly ash, silica fume (SF), rice husk ash (RHA) and metakaolin. Kaolin is a fme, white, clay mineral that has been traditionally used in the manufacture of porcelain. It is thought that the term kaolin is derived from the Chinese kaoling, which translates loosely to white hill and has been related to the name of a mountain in China that yielded the first kaolins that were sent to Europe. Kaolinite is the mineralogical term that is applicable to kaolin clays. Kaolinite is defined as a common mineral, hydrated aluminum disilicate [AI,Si,O,(OH).], the most common constituent of kaolin.Kaolins, a class of clay minerals, which like all clays, are phyllosilicates i.e. a layer silicate.

The meta prefix in the term is used to denote change. It is a borrowing from Greek meaning after, along with, beyond. It is used, and is recognizable, in the formation of compound words metabolic-metamorphosis. The scientific use of the prefix is used for a combining form denoting the least hydrated of a series. In the case of metakaolin, the change that is taking place is dehydroxylization, brought on by the application of heat over a defined period of time. At about 100-200 degrees C, clay minerals lose most of their adsorbed water. The temperature at which kaolinite"loses water by dehydroxilization is in the range of 500-800 degrees C. This thermal activation of a mineral is also referred to as calcining. Beyond the temperature of dehydroxylization, kaolinite retains two-dimensional oroer in the crystal structure and the product is termed metakaolin. The key in producing metakaolin for use as a supplementary cementing material, or pozzolan is to achieve as near to complete dehydroxilization as possible without over heating. Successful processing results in a disordered, amorphous state, which is highly pozzolanic. Thermal exposure beyond a defined point will result in sintering and the formation of mullite, which is dead burnt and not reactive. In other words, kaolinite, to be optimally altered to a metakaolin state, requires that it is thoroughly roasted but never burnt. For ages, concrete has been one of the widely used materials for construction. The following two characteristics have, however, restricted its full utilization: it is brittle and weak in tension and develops cracks during curing and due to thermal expansion / contraction over a period ot time. This led to search of new composite material with superior properties and performance

13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India

National Conference on Recent Trends in Engineering & Technology

by using short, discrete, stiff and closely spaced fibers called Fiber Reinforced Concrete (FRC). In fiber composite, the increase in strength and toughness, the degree of ductility, the extent of post-cracking behavior, and simple and multiple cracking depend on the strength characteristics of the fibers themselves, the bond in the matrix-fiber interface, the ductility of fibers, the volume of fibers, the dispersion and orientation of fibers, and their shape and aspect ratio [1]. In the present work, to facilitate comparative studies different types of plain cement concrete, steel fibre reinforced concrete with different ternary blended cement are prepared and are tested to find splitting tensile strength, static flexural strength, with all samples casted using a fixed mix proportion.[2]

B. Splitting Tensile Strength Test[5] Direct tension test of concrete is seldom made because of difficulties in mounting the specimens and uncertainties as to the secondary processes induced by the holding devices. An indirect test for tensile strength of concrete has been standardized by ASTM and is in general use. In this test specimen of cylindrical shape of diameter 15 cm and length 30 cm are tested under a compressive load across the diameter along its length till the cylinder splits. To determine the average split tensile strength, in the present work, 3-3-3 cylinders of PCC, SFRC and different ternary blended proportion mixes are tested under Compression Testing Machine of 200 tones capacity after removing the specimens at the age of 28 days and 90 days from the curing tank. Cylindrical specimen is placed in the machine, along its length, keeping plywood strips between the cylinder and the testing machine bearing surfaces at top and bottom of cylinder. Load is gradually applied and maximum load at which the specimen fails is noted. The magnitude of the tensile strength is worked out with the help of 2P/(π L D) where P is applied load at failure, D is diameter in mm and L is the length of specimen in mm.C. Static Flexural Strength Test[5] The purpose of flexural strength test is to have and idea of the load at which a concrete member in bending may crack due to tension. It gives an idea of tensile strength of concrete. The tensile strength of concrete in bending is known as its flexural tensile strength. The flexural tensile strength is also known as modulus of rupture and is equal to bending moment at failure divided by the section modulus of a beam under test. In the present work, beam samples of PCC, SFRC and different ternary blended mixed proportion were casted of size 100 x 100 x 500 mm size are tested under simply supported condition keeping the span as 400 mm. For conducting static flexural test, the deflection is increased at a constant rate of 0.005 mm/sec, under two loading points symmetrically located from mid span at 1/3 rd the span from each support. Maximum load at which beam fails is recorded and distance between the line of fracture and the nearer support is measured on the centre line of the tensile side of the specimen in mm. The first crack flexural stress is determined in the

beam from bending moment M (PL/6) at failure divided by the section modulus.

D. Discussion and Conclusions1. Addition of steel fiber at 1.0 volume fraction is found not

to affect the workability of concrete; concrete is easilymixed with steel fiber.

2. Addition of steel fiber does not affect the finishibility of

concrete. Outer surface of concrete after casting was as

smooth as plain concrete.

3.Marginal increase in bulk density and marginal decrease

of slump of concrete was observed due to addition of steel.

4.Ultimate compressive strength of SFRC in comparison to

PCC is found 5.15 %. From this it can be concluded that

presence of fibers does not affect substantially the concrete

strength. This is very obvious as compressive strength of

concrete is primarily affected by the property of concrete

matrix and not due to the influence of the fibers.

5.Split tensile strength of SFRC in comparison to PCC is

found 9.46 %. Also in SFRC samples multiple cracking

was observed at fracture surface and failure occurred due

to fiber pullout in some of the cases.

6.Under two point loading arrangement used for flexural strength testing, the failure occurs in middle third portion of the specimen. In case of PCC, failure is sudden and through the aggregate. While in case of SFRC beams, the first crack could be seen easily. Crack starts slowly from the bottom layer of the specimen and as the load increases, the crack propagates up to the top layer of the specimen. As the beams were tested under displacement control, pulling out of fibers could be seen easily with the propagation of crack.

7.Flexural strength of SFRC in comparison to the PCC is found 17.59 % higher Here, addition of fibers marginally increases the flexural strength of concrete. This may bebecause the strength of FRC mixes is primarily affected by the properties of the concrete matrix and not the properties of fibers. The advantage of using fibers however could be clearly seen by prolonged post peak behavior.

8. Steel FRC specimens failed in a ductile manner under static loading because of the effective bridging action

13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India

National Conference on Recent Trends in Engineering & Technology

TABLE II OVER ALL RESULT OF TENSILE STRENGTH FOR 28 DAYS AND 90 DAYS

TABLE III OVER ALL RESULTS OF FLEXURAL

STRENGTH FOR 28 DAYS AND 90 DAYS

REFERENCES

[1] A. K. Dutta: "Fibrous Concrete - A New Look", Journal

of New Building Materials and Construction World", pp. 38-

44, July 2003.

[2] A.K.Twari, D.N.Jha,Engineered Mineral Admixture for

use with Portland cements, 20 microns Ltd. Baroda.

[3] IS 10262-2009, concrete mix design

[4] Nabil Bouzoubaa, Alain Bilodeau, Vasanthy

Sivasundaram and Dean M.Golden, “Development of Ternary

Blends for High performance concrete”.

[5] IS 516-1959

Percentage replacement of cement by Fly ash and

Blast Furnace Slag

Average tensile

StrengthN/mm2

% increase or decrease in tensile strength w.r.t reference

mix

28 days 90 days 28 days 90 days

Normal Mix 4.21 6.00 9.46% 3.07%C+0+0

(Reference mix)

4.65 6.19 -- --

C+30+0 4.95 6.27 6.45% 1.29%C+25+5 5.23 6.37 12.47% 2.91%

C+20+10 5.44 6.67 16.99% 7.75%C+15+15 5.89 6.86 26.67% 10.82%C+10+20 5.66 6.72 21.72% 8.56%C+5+25 5.62 6.58 20.86% 6.30%C+0+30 5.37 6.36 15.48% 2.75%

Percentage replacement of cement by Fly ash and Blast Furnace Slag

Average flexural StrengthN/mm2

% increase or decrease in flexural

strength w.r.t reference mix

28 days90

days28 days 90 days

Normal Mix 4.31 4.36 17.59% 19.11%

C+0+0 (Reference mix)

5.23 5.39 --- ---

C+30+0 6.12 6.14 17.02% 13.91%C+25+5 6.57 6.746 25.62% 25.16%

C+20+10 6.908 7.477 32.08% 38.72%

C+15+15 7.315 7.76 39.87% 43.97%C+10+20 6.99 7.51 33.65% 39.33%C+5+25 6.868 7.112 31.32% 31.95%C+0+30 6.5024 6.868 24.33% 27.42%

13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India

National Conference on Recent Trends in Engineering & Technology