SYNOPSIS
CHAPTER-1
INTRODUCTION
1. GENERAL
The advancement and latest development of major construction is largely associated with improving the efficiency of the building under seismic effect, reducing cost, economic use of new materials etc., concrete is one such material, which is consumed in construction industry next to water consumption in the world. This marvelous material is strong in compression but very weak in tension. Use of dispersed reinforcement in the cement based matrix/concrete attains promising new material and eliminates certain drawbacks and entrances certain property.
1.2 HISTORICAL BACK GROUND
Historically, fibers were used to reinforced the brittle material since ancient times, straws were used to reinforce sun-baked bricks, horse hairs were used to reinforce plaster and asbestos fibers were used to reinforce cement.
In 1910, porter put the idea that concrete can be strengthened by the inclusion of fibers. Till 1963; there was only slow progress on fiber reinforced concrete (FRC). Romualdi and Batson gave rise to FRC by conducting numerous experimental works to determine the basic engineering properties such as compressive, tensile strength FRC.
Typical types of fibers used are steel, acrylic asbestons, glass, xylon, polyster, polyethylene, polypropylene, rayon, rock wool and so on. Steel fibers are available in round, flat, reimped, deformed forms. Steel fibers were used in different structural elements in various zones and investigated its performance. Now-a-days synthetic fibers have become more attractive and used for the reinforcement of cementitious materials.
‘Fiber Reinforced Cement’ as a material made from hydraulic cement and discrete, discontinuous fibers (containing no aggregate). “Fiber reinforced concrete” (FRC) is made with hydraulic cement, aggregates of various sizes, in corporating discrete, discontinuous fibers. Both are firmly established as a new construction material.
Steel fibers and synthetic fibers find applications in civil engineering on a larger scale by virtue of their inherent advantages; it is of interest to note that the performance of concrete can be enhanced through the employment of these micro-reinforcements in a hybrid form. The volume of data available on the performance studies of hybrid fiber reinforced concrete appears to be inadequate for a better understanding the investigation, it is proposed to combine these fibers at different proportions in the beam structural elements and engineering properties and performance are being investigated.
The necessity for the addition of fibers in structural material is to increase the strength of the concrete and mortar and also to reduce the crack propagation that mainly depends on the following parameters.
➢ Strength characteristics of fiber
➢ Bond at fiber matrix interface
➢ Ductility of fibers
➢ Volume of fiber reinforcement
➢ Spacing, dispersion, orientation, shape and aspect ratio of fiber.
High strength fibers, favorable orientation large volume, fiber length and diameter of fiber have been found independently to improve the strength of composites. The steel fiber is known to have possessed high tensile strength and ductility.
The most significant factor affecting resistance to crack propagation and strength of the fibrous concrete and mortar are
➢ Shape and bond at fiber matrix interface
➢ Volume fraction of fibers
➢ Fiber aspect ratio and Orientation of fibers
➢ Workability and Compaction of Concrete
➢ Size of Coarse Aggregate
➢ Mixing:
A) SHAPE AND BOND AT FIBER MATRIX INTERFACE
The modulus of elasticity of matrix must be much lower than that of fiber for efficient stress transfer. Low modulus of fibers such as nylon and polypropylene are therefore unlikely to give strength improvement, but they help in the absorption of large energy and therefore impart greater degree of toughness and resistance to impact. High modulus fibers such as steel, glass and carbon impart strength and stiffness to the composite. Interfacial bond between the matrix and the fibers also determine the effectiveness of stress transfer, from the matrix to the fiber. A good bond is essential for improving tensile strength of the composite. The interfacial bond could be improved by larger area of contact, improving the frictional properties and degree of gripping and treating the steel fibers with sodium hydroxide or acetone.
B) VOLUME FRACTION OF FIBER
The strength of the composite largely on the quantity of fibers used in it. The increase in the volume of fibers, increase approximately linearly, the tensile strength and toughness of the composite. Use of higher percentage of fiber is likely to cause segregation and hardness of concrete and mortar.
C) FIBER ASPECT RATIO
Fiber aspect ratio is defined as the ratio of fiber length to the equivalent fiber diameter. In order to utilize fracture strength of fibers fully, adequate bond between the matrix and the fiber has to be developed. This depends on the shape of the fibers viz., straight, crimped, hooked end and its aspect ratio. An aspect ratio 60 to 100 is commonly used.
D) ORIENTATION OF FIBERS
One of the differences between conventional reinforcement and fiber reinforcement is that in conventional reinforcement bars are oriented in the direction desired while fibers are randomly oriented. It was observed that in fiber reinforced mortar the fibers aligned parallel to the applied load offered more tensile strength and toughness than randomly distributed or perpendicular
E) WORKABILITY AND COMPACTION OF CONCRETE
Incorporation of steel fiber decreases the workability considerably and even prolonged external vibration fails to compact the concrete. This situation adversely affects the consolidation of fresh mix. The fiber volume at which this situation is reached depends on the length and diameter of the fiber and non-uniform distribution of the fibers. Generally, the workability and compaction standard of the mix are improved through increased water/cement ratio or by the use of water reducing admixtures. The overall workability of fresh fibrous mixes was found to be largely independent of the fiber type. Crimped fibers produce slightly higher slumps, and hooked fibers were found to be more effective than straight and crimped ones.
F) SIZE OF COARSE AGGREGATE
Several investigators recommended that the maximum size of the coarse aggregate should be restricted to 10mm, to avoid appreciable reduction in strength of the composite. A fiber in effect, as aggregate having a simple geometry, their influence on the properties of fresh concrete is complex. The inter-particle friction between fibers and between fibers and aggregates controls the orientation and distribution of the fibers and consequently the properties of the composite. Friction reducing admixtures and admixtures that improve the cohesiveness of the mix can significantly improve the mix.
G) MIXING
Mixing of fiber reinforced concrete needs careful conditions to avoid balling of fibers, segregation, and difficulty of mixing the materials uniformly. Increase in the aspect ratio, volume percentage and size and quantity of coarse aggregate intensify the difficulties and balling tendencies. It is important that the fibers are dispersed uniformly throughout the mix. This can be done by adding fibers before adding water. When mixing in a laboratory mixer, introducing the fibers through a wire mesh basket will help even distribution of fibers.
1.3 SCOPE FOR THE PRESENT STUDY
➢ To study the physical properties of concrete using polypropylene fiber, steel fiber
➢ Evaluation of compressive strength and of splitting tensile strength of concrete with steel fiber
➢ Evaluation of compressive strength and of splitting tensile strength of concrete with polypropylene fiber.
➢ Evaluation of compressive strength and of splitting tensile strength of concrete without fiber.
➢ To establish the physical properties of constituents (cement, fine aggregate, coarse aggregate and fiber)
➢ To design the concrete mix using IS (Indian Standard)
1.4 EFFECT OF FIBERS IN CONCRETE
➢ Fibers are initially used in concrete to control plastic shrinkage and drying
Shrinkage cracking.
➢ They also lower the permeability of concrete and thus reduce bleeding of water.
Some types of fibers produce greater impact, abrasion and shatter resistance in
Concrete.
➢ The material ductility is increased by the addition of fibers.
➢ High-performance fiber-reinforced concrete used in bridges found to provide
Residual strength and control cracking. The residual strength is directly proportional
to the fiber content.
➢ Generally fibers do not increase the compressive strength of concrete. Fibers
cannot replace moment resisting or structural steel reinforcement. Some fibers reduce
the strength of concrete
CHAPTER-2
LITERATURE REVIEW
A) Waheeb Ahmed al-khaja (1997 volume 7) studied the mechanical properties
And time dependent deformation of polypropylene fiber concrete. This investigation conducted to study the effect of PPF used for reinforcing concrete mixes.
The compression, tension and flexural strength test were performed changing fiber 0.1 to 3 % of the cement weight content. Adding the 0.5 % of PPF the compressive strength can obtain the maximum value.
B) K.Anbuvelan, M.M. Khadar. M.h, M.Lakshmipathy and K.S. Sathyanarayann studies on properties of concretes containing polypropylene, steel and reengineered plastic shred fiber work an attempt has been made to study the influence of polypropylene fibers, steel fibers and re-engineered plastic shreds with0.1 %, 0.5 % and 0.5 % by volume of concrete mix.
1. With the addition of polypropylene fibers to plain concrete, its strength is increased in the range of 4 %-17 %. The improvement in its wear and impact resistance were 28 %-58 % and 72 %-134 %, respectively and reduction in maximum crack width is to an extent of 21 %-74 %.
2. The steel fiber added to plain concrete resulted in improvement of the strength, wear and impact resistance characteristics by 4 %-49 %, 42 %-52 % and 34 %-38 % respectively. The reduction in maximum crack width is found to be 46 %-67 %.
3. With the addition of reengineered plastic fibers to plain concrete, strength, wear and resistance to impact are increased to 20%-17.60%, 31%-48% and 123%-139% respectively. The reduction in its maximum crack width is 59%-73%.
C) Maalej and Paramasivam (2002) studied the effectiveness of ductile fiber reinforced cementitious composites (DFRCC) in retarding the corrosion of steel in reinforced concrete beams. A fiber content of 1.5 % PVA & 1.0 % steel fibres was used in a DFRCC and a layer of DFRCC was used around the main longitudinal reinforcement (FRC). The authors concluded that the FGC concept using DFRCC material was very effective in preventing corrosion – induced damage in RC beams and minimizing the loss in the beam load and deflection capacities. They also reported that the functionally graded concrete (FGC) beams have higher resistance against corrosion and cracking compared with conventional reinforced concrete.
D) Nataraja, Dhang and Gupta (1999) examined the feasibility of using UPV technique for assessing the quality of steel fiber reinforced concrete. The study parameters included fiber content, aspect ratio of fibres and concrete strength. The pulse velocity readings were taken longitudinally at the centre of cylinders and prisms. The authors concluded that the quality of SFRC could be adequately confirmed using UPV technique. They also reported that the pulse velocity at 7 – days and 28 – days can be estimated knowing the pulse velocity at 1- day using amplification factors of 1.11 and 1.13 for both plain and fiber reinforced concrete up to a compressive strength of 50 MPa.
E) Mohammed and Kaushik (2000) investigated the influence of mixed aspect ratio of fibres on compressive strength, splitting tensile strength, flexural strength, impact strength and ductility of SFRC. They tried different mixed aspect ratio of fibres with a total volume fraction of 1.0%. The authors concluded that the use of 65% long fibres and 35% short fibres gave optimum mechanical properties.
CHAPTER-3
METHODOLOGY
CHAPTER-4
PROPERTIES OF MATERIALS
4.1 PROPERTIES OF CEMENT
The properties of ordinary Portland cement as shown in the table 4.1.
|Test Particulars |Result Obtained |Requirements as per IS: 12269 1987 |
|Specific gravity |3.15 |3.10-3.15 |
|Normal consistency (%) |31 |30-35 |
|Initial setting time (minutes) |37 |30 minimum |
|Final setting time (minutes) |570 |600 maximum |
|Compressive strength (MPa) | | |
|3 days |28 |43 |
|7 days |38 |33 |
|28 days |44 |23 |
Table 4.1: Physical properties of ordinary Portland cement
4.2 PROPERTIES OF FIBERS
4.2.1 STEEL FIBER (METALLIC FIBER)
Steel fiber is one of the most commonly used fibers. Generally, round fibers are used. The diameter may vary from 0.25 to 0.75 mm. The steel fiber is likely to get rusted and lose some of its strength. But investigations have shown that the rusting of the fibers takes place only at the surface. Use of steel fibers make significant improvements in flexural, impact and fatigue strength of concrete, it has been extensively used in various types of structures, particularly for overlays of roads, airfield pavements and bridge decks. Thin shells and plates have also been constructed using steel fibers.
[pic]
Figure 4.1: The figure shows the general view of steel fiber
4.2.2 POLYMERIC FIBER
Synthetic polymeric fibers have been produced as a result of research and development in the petrochemical and textile industries. Fiber types that have been tired with cement matrices include arcrylic, aramid, nylon, polyester, polypropylene and polyethylene. They all have a very high tensile strength, but most of these fibers (except for aramids) have a relatively low modulus of elasticity. The quality of polymeric fibers that makes them useful in FRC is their very high length to diameter ratios, their diameters are on the order of micrometers.
A.POLYPROPYLENE FIBER (PPF)
Polypropylene fibers are synthetic types of fibers. Synthetic fibers are gradually replacing steel fibers due to the fact that are cost effective, can be used in low volume fractions and there is no risk of corrosion by there is used in concrete. Polypropylene fibers are currently manufactured in variety of geometries and configuration. These fibers are produced by drawing or stretching the synthetic fiber into film sheets which are then slit longitudinally into tapes. Polypropylene fibers are composed of crystalline and non-crystalline region.
Polypropylene fibers have a softening point in the region of 150º c and a melting point at 160 to 170 º c. It is lowest thermal conductivity of all commercial fibers. It has excellent chemical resistance to acid and alkalis, high abrasion resistance.
[pic]
Figure 4.2: The figure shows the general view of polypropylene fiber
B. NYLON FIBER
Commercial available nylon fibers are made of nylon 6. They are available in varies lengths in single filament form. Since this fibers are very thin, a number of fibers per pound in the range of 35 million per pound for fiber length of 0.75 inch (19 mm).
C. POLYESTER
Polyester fibers are made of ethyl acetate monomers. Their physical and chemical properties can be changed substantially by altering manufacturing techniques. The higher modulus of elasticity and better bonding to concrete that is important for FRB application can be achieved by some of this modification.
[pic]
Figure4.3: The figure shows the general view of polyester fiber
Physical properties of polymeric fibers as shown in the given table 4.2
|Fiber type |Effective Dia × 10-3 |Specific Gravity |Tensile Strength (MPa)|Elastic Modulus (GPa) |Ultimate Elongation |
| |(mm) | | | |(%) |
|Nylon |- |1.16 |965 |5.17 |20 |
|Polyester |- |1.34-1.39 |896-1100 |17.5 |- |
|Polyethylene |25-1020 |0.96 |200-300 |5 |3 |
|Polypropylene |- |0.9-0.91 |310-760 |3.5-4.9 |15 |
Table 4.2: Physical properties of polymeric fibers
D. POLYETHYLENE
Polyethylene fibers are available both in standard length (0.52-2, 12-50 mm)and in pulp form .the longer fiber available in the market have wart-like surface deformation, better bond to concrete. The fibers that are available in pulp form have been promoted has a replacement for asbestos fibers in concrete. These short fibers can also used in cement matrix to improve ductility, impact resistance and fatigue strength
[pic]
Figure4. 4: The figure shows the general view of polyethylene fiber
E. GLASS FIBERS
The glass fibers are primarily used for glass fiber reinforced cement (GFRC) sheets. Regular E-Glass fibers were found to deteriorate in concrete.
[pic]
Figure4. 5; The figure shows the general view of glass fiber
4.2.3 NATURALLY OCCURING FIBERS
The oldest forms of fiber reinforced composites were made with naturally occurring fiber such as straw and horse hair. Modern technology has made it possible to extract fibers economically from various plants, such as jute and bamboo to use in cement composites.
The unique aspects of this fiber in the low amount of the energy required to extract these fibers. The primary problem with used of this fibers in concrete is their tendency to disintegrate in an alkaline environment. Effects of being made to improve durability of this fiber in concrete by using admixture to make the concrete less alkaline and the subjecting the fibers to special treatment.
Natural fibers used in Portland cement composite include akwara bamboo, coconut, flax, jute, sisal, sugarcane bagases, wood, and others mechanical properties of some of these fibers are presented in the succeeding.
A. AKWARA FIBERS
Akwara is a natural fiber derived from a plant stem grown in large quantities in Nigeria. They are made of a cellular core covered with a smooth sheath. Akwara fibers were found to be durable in alkaline environment of cement matrix, and they are also dimensionally stable under wetting and drying conditions. The disadvantages are their low elastic modulus and brittleness.
B. BAMBOO FIBERS
Bamboo, which is a member of the grass family, grows in tropical and subtropical region. Plants can grow up to a height of 15 m. their hollow stalks have intermediate joints, the diameters of these stalks range from 0.4 to 4.0 inch (1 to 10 cm).
Special techniques are needed to extract the fibers from bamboo. Bamboo fibers are strong in tension, but have a relatively low modulus of elasticity. Their tendency absorb water adversely affects the bonding between the fibers and the mixture during the curing process.
C. COCONUT FIBERS
A mature coconut has an outer fibrous husk. Coconut fibers, called coir, can be extracted simply by soaking the husk in water or, alternatively, by using mechanical processes. These short (only a few inches) stiff fibers have been used for making rope for centuries. Coir has a low elastic modulus and is also sensitive to moisture changes.
D. FLAX AND VEGETABLE FIBERS
Flax is grown for its fiber. Flax fibers are strong under tension and also possess a high modulus of elasticity. Fibers extracted from other plant such as elephant grass, water reed, plantain, and musamba have also been tried as reinforcements for concrete. Most of these fibers are removed from the stems of the plants manually.
Physical properties of naturally occurring fibers as shown in the given table 4.2
|Fiber Type |Coconut |Sisal |Sugarcane Bagasse |
|Pyconometer bottle (W1) |651.5 |651.5 | |
|Wt of Pyconometer + dry soil (W2) |851.5 |855.5 | |
|Wt of Pyconometer + dry soil + water (W3) |1668 |1675 | |
|Wt of Pyconometer + water (W4) |1545.5 |1549.5 | |
|Specific gravity = W2-W1/[(W2-W1)-(W3-W4)] |2.6 |2.6 |2.6 |
Table5.1: Specific gravity of fine aggregate coarse
Table5,2 shows the Specific gravity test result for coarse aggregate by using Pyconometer test.
|Description |1 |2 |Average |
|Pyconometer bottle (W1) |651.5 |651.5 | |
|Wt of Pyconometer + dry soil (W2) |881.5 |855.5 | |
|Wt of Pyconometer + dry soil + water (W3) |1753.68 |1765 | |
|Wt of Pyconometer + water (W4) |1606 |1633 | |
|Specific gravity = W2-W1/[(W2-W1)-(W3-W4)] |2.8 |2.8 |2.8 |
Table 5.2: Specific gravity of coarse aggregate
Table5.3 shows the Sieve analysis test for fine aggregate concrete.
|IS Sieve size |Quantity Retained (g) |Cumulative Wt Retained |% Retained |% Passing |Limits for Zone-II |
|(mm) | |(g) | | |(IS383) |
|10 |0 |0 |0 |100 |100 |
|4.75 |0 |0 |0 |100 |90-100 |
|2.36 |120 |120 |2.4 |97.6 |95-100 |
|1.18 |1425 |1545 |28.5 |69.1 |55-90 |
|0.6 |880 |2425 |17.6 |51.5 |35-59 |
|0.3 |1670 |4095 |33.4 |18.1 |8-30 |
|0.15 |905 |5000 |18.1 |0 |0-10 |
Table5.3: Sieve analysis of fine aggregate concrete
Table5.4 shows the Sieve analysis test for coarse aggregate concrete.
|Sieve Size (mm) |Quantity Retained (g) |Cumulative Wt Retained (g) |% Retained |% Passing |
|63 |0 |0 |0 |100 |
|40 |0 |0 |0 |100 |
|20 |803 |803 |5.8 |94.2 |
|12.5 |0 |803 |5.8 |94.2 |
|10 |12562 |13365 |96.5 |3.5 |
|4.75 |374 |13739 |99.2 |0.8 |
Table 5.4: Sieve analysis of coarse aggregate concrete
CHAPTER-7
MIX DESIGN
Proper design of concrete mixture is intended to obtain such proportioning of ingredients which will produce concrete of high durability performance during the designed life of a structure, usually 50 years.
For a particular strength and long term qualities and performance. Several factors determine these properties.
1. Quality of cement
2. Proportion of cement and other cementations materials in relation to water in the mixture (water/cementation ratio)
3. Strength and cleanliness of aggregate
4. Interaction or adhesion between cement paste and aggregate
5. Adequate mixing of ingredients
6. Proper placing, finishing, and compaction of fresh concrete
7. Curing at a temperature not below 50° F while the placed concrete gains strength
8. Chloride content not exceeds 0.15% in reinforced concrete exposed to chlorides in service and 1% for dry protected concrete.
A study of these requirements shows that most of the control actions have to be taken prior to placing the fresh concrete. Since each control is governed by the proportion and the mechanical ease or difficulty in handling and placing, the development of criteria based on the theory of proportioning for each mixture should be studied.
In addition, a determination has to be made as to the admixtures that need to be prescribed to enhance the long-term high performance and durability of the finished product.
There are several types of strength-modifying admixtures: high range water reducers (super plasticizer), polymers, granulated blast furnace slag, fly ash, or slica fume. However, in mixture proportioning for very high strength concrete, isolating the water/cementation materials ratio W/(C+P) (often called simply w/cm) from the paste/aggregate ratio due to the very low water content can be more effective in arriving at the optimum mixture with fewer trial mixtures and field trial batches. The very low w/cm material ratio required for strength in the range 138 Mpa or higher requires major modification to the present standard approach used in mixture proportioning that seems to work well for strength up to 83 Mpa. The optimum mixture that can be chosen with minimum trials has to produce satisfactory concrete product in both its plastic and hardened states.
7.1 VARIOUS METHODS OF DESIGN MIX PROPORTIONING
➢ Arbitrary proportion
➢ Maximum density method
➢ Fineness modulus method
➢ Surface area method
➢ ACI Committee method
➢ Grading curve method
➢ IRC-44 method
➢ High strength concrete mix design
➢ Design based on flexural strength
➢ Indian standard method
7.2 CONCRETE MIX DESIGN FOR INDIAN STANDARD METHOD
STEP 1: Design stipulation
A) Characteristic compressive strength = 20 N /mm2
B) Max size of aggregate = 20 mm (angular)
C) Degree of workability = 0.9 compacting factor
D) Degree of quality control = good
E) Type of exposure = severe
STEP 2: Test data for materials
Cement used opc = 53 grade
Specific gravity of cement = 3.15
Specific gravity of fine aggregate = 2.6
Specific gravity of coarse aggregate = 2.8
Water absorption
1. Coarse aggregate = 0.5%
2. Fine aggregate = 1%
STEP 3: Target mean strength of concrete
Target compressive strength F ck = f ck + t.s
fck = Characteristic compressive strength at 28 days
s = Standard deviation
t = tolerance factor (its take 1.65)
For using table(1) the target mean strength for the specified characteristic strength
20 + (1.65 × 4.6) = 27.6 N/ mm2
STEP 4: Selection of water-cement ratio
The w/c ratio required for target mean strength of 27.6 N/ mm2 is 0.5 from table 5 of IS 456-2000.
STEP 5: Selection of water and sand content.
Table 4 of IS 10262-1282 (for 20 mm nominal max size aggregate)
And confirming to grading zone-II
Water content per m3 concrete = 186 kg sand content as percentage of total aggregate by absolute volume = 35% for changes in values in water-cement ratio for following adjustment is required.
|Changing Condition |Adjustment Required |
| |In water content % |%sand in total aggregate |
|For decrease in water cement ratio |0 |-2.0 |
|(0.6-0.5)=0.1 | | |
|For increase in compacting factor |+3 |0 |
|(0.9-0.8)=0.1 | | |
|For sand conforming zone-II of table 4 |0 |-1.5 |
|IS 383-1970 | | |
|3% |-3.5% |
Therefore required sand content as % of total aggregate by absolute volume = 35-3.5 = 31.5%
Required water content = 186 + (186×3)/100
=191.6 l/m3
STEP 6: Determination of cement content
Water cement ratio = 0.5
Water = 191.6 l
Cement = 191.6/0.5
=383 kg/m3
This cement content is adequate for extreme exposure condition. According to IS: 456-2000
STEP 7: Determine aggregate content
By using equation 3.15 form 10262-1982
V = [w + (C/Sc) + (1/p) + (fa/Sfa)] × (1/1000)
Where
V = absolute volume of fresh concrete, which is equal to gross volume (m3) minus the volume of entrapped air,
W = mass of water (kg) per m3 of concrete,
C = mass of cement (kg) per m3 of concrete,
Sc = specific gravity of cement,
p = ratio of fine aggregate to total aggregate by absolute volume,
fa = total masses of fine aggregate and coarse aggregate (kg) per m3 of concrete respectively, and
Sfa = specific gravities of saturated surface dry fine aggregate and coarse aggregate respectively.
From IS: 383 : 1970 specified maximum size of aggregate 20 mm, the amount of entrapped air in the wet concrete is 2%, taking this into account and apply into the above equation.
0.98 = [191.6 + (383/31.5) + (1/0.315) + (fa/2.6)] × (1/1000)
fa = 545 kg/m3
Therefore
Ca = (1-0.315/0.315) × (1/1000)
Ca = 1188 kg/m3
fa = amount of fine aggregate
Ca = amount coarse aggregate
MIX PROPORTION
|Water |Cement |Fine Aggregate |Coarse Aggregate |
|191.6 kg |383kg |545 kg |1188 kg |
|0.5 |1 |1.4 |3.1 |
CHAPTER-8
TESTING OF SPECIMEN
8.1 SPECIMEN PREPARATION
➢ The steel fiber and polypropylene fiber added in the range of 0.25%, 0.50%, 0.75, 2%, and 2.5% by volume of concrete specimen.
➢ The concrete was mixed in hand then the decided quantity of fiber was added evenly and mixed to get the uniform distribution and homogeneous mixer without forming fiber balls.
➢ The compressive strength and tensile strength performance were evaluated using 150 mm cube, 100 mm diameter and 200 mm height cylinder.
➢ The specimens were cast in steel mould. The test specimens were normal cured under water.
8.2 COMPRESSIVE STRENGTH TEST
The compressive strength of concrete is one of the most important and useful properties of concrete. I most structure applications concrete is employed primarily to resist compressive stresses. In those case where strength in tension or in shear is of primary importance, stresses. In those cases where strength in tension or in shear is of primary importance, the compressive strength is frequently used as a measure of these properties. Therefore, the concrete making properties of varies ingredients of mix are usually measured in terms of the compressive strength. Compressive strength is also used as a qualitative measure for other properties of hardened concrete.
The modulus of elasticity in this case does not follow the compressive strength. The other case where the compressive strength does not indicate the useful property of concrete is when the concrete is subjected to freezing and thawing.
Concrete containing about 6 percent of entrained air which is relatively weaker is strength is found to be more durable than dense and strong concrete.
The compressive strength of concrete is generally determined by testing cubes or cylinders made in laboratory or field or cores drilled from handed concrete at site or from the non-destructive testing of the specimen or actual structures. The testing of hardened concrete is discussed in the subsequent chapter.
Strength of concrete is its resistance to rupture. It may be measured in a number of ways, such as, strength in compression, in tension, in shear or in flexure.
In order to determine the compressive strength, a total number of 144 cubes were cast. After 24 hours of casting, the specimens were de-molded and cured under water.
At the end of curing period, the above specimens were tested in a compressive testing machine as per: IS516-1989.
8.3 SPLIT TENSILE STRENGTH TEST
This is also sometimes referred as, “Brazilian Test”. This test was developed in Brazil in 1943.At about the some time this was also independently developed in Japan. The test is carried out by placing a cylindrical specimen horizontally between the loading surfaces of a compression testing machine and the load is applied until failure of the cylinder, along the vertical diameter.
When the load is applied along the generatrix, an element on the vertical diameter of the cylinder is subjected to a vertical compressive stress. In order to determine the split tensile strength of various concretes test was conducted as per IS: 5816-1999.
A total number of 96 cylindrical specimens were cast and after 28 days of curing, they were tested in a compression testing machine by loading it on the longitudinal direction.
CHAPTER-9
TEST RESULTS
The compressive strength of various percentage steel fibers added are given by the table9.1.
|Sl. no |Mix |Steel fiber (%) |Compressive Strength (Mpa) |
| | | |At 3days |At 7 days |At 28 days |
|1. |CC |0 |12.5 |15.5 |18 |
|2. |SF1 |0.25 |13.5 |19 |20 |
|3. |SF2 |0.5 |14.6 |20 |23.5 |
|4. |SF3 |0.75 |14.8 |21.4 |24.5 |
|5. |SF4 |1 |16 |24.2 |26 |
|6. |SF5 |1.5 |18.5 |25.3 |29 |
|7. |SF6 |2 |18 |23 |26.3 |
|8 |SF7 |2.5 |17.3 |22 |26 |
Table 9.1: Compressive strength of M20 grade concrete with and without steel fiber
Where
CC – Control Concrete
SF1– 0.25 % steel fiber added concrete
SF2 – 0.5 % steel fiber added concrete
SF3 – 0.75 % steel fiber added concrete
SF4- 1 % steel fiber added concrete
SF5 – 1.5 % steel fiber added concrete
SF6 – 2 % steel fiber added concrete
SF7 – 2.5 % steel fiber added concrete
[pic]Figure 9.1: Graph showing the compressive strength of M20 grade concrete with and without steel fiber
The compressive strength of various percentage added Polypropylene fiber added concrete as given by the table9.2.
| |Mix | Polypropylene fiber (%) |Compressive Strength (Mpa) |
|Sl. No | | | |
| | | |At 3days |At 7 days |At 28 days |
|1. |CC |0 |12.5 |15.5 |18 |
|2. |PPF1 |0.25 |13.5 |18.5 |21 |
|3. |PPF2 |0.5 |18 |21.3 |25.5 |
|4. |PPF3 |0.75 |17.3 |20 |24.3 |
|5. |PPF4 |1 |17 |19.2 |23 |
|6. |PPF5 |1.5 |16.6 |18.6 |22 |
|7. |PPF6 |2 |15.3 |17.9 |21.1 |
|8 |PPF7 |2.5 |14 |17 |20.8 |
Table 9.2: Compressive strength of M20 grade concrete with and without polypropylene fiber
Where
CC – Control concrete
PPF1 – 0.25 % polypropylene fiber added concrete
PPF2 – 0.5 % polypropylene fiber added concrete
PPF3 – 0.75 % polypropylene fiber added concrete
PPF4 – 1% polypropylene fiber added concrete
PPF5 – 1.5 % polypropylene fiber added concrete
PPF6– 2 % polypropylene fiber added concrete
PPF7– 2.5 % polypropylene fiber added concrete
[pic]
Figure 9.2: Graph shows the compressive strength of M20 grade concrete with and without polypropylene fiber
The Split tensile strength of various percentage steel fiber added concrete as given by the table9.3.
|Sl. no |Mix |Steel fiber (%) |Tensile Strength (Mpa) |
| | | |At 3days |At 7 days |At 28 days |
|1. |CC |0 |1.5 |1.8 |3 |
|2. |SF1 |0.25 |1.6 |2.2 |3.1 |
|3. |SF2 |0.5 |1.72 |2.6 |3.3 |
|4. |SF3 |0.75 |1.81 |2.8 |3.5 |
|5. |SF4 |1 |2 |3.31 |3.9 |
|6. |SF5 |1.5 |2.2 |3.8 |4.5 |
|7. |SF6 |2 |2.15 |3.6 |4.2 |
|8. |SF7 |2.5 |2.1 |3.52 |4.1 |
Table9.3: Split tensile strength of M20 grade concrete with and without steel fiber
Where
CC – Control Concrete
SF1– 0.25 % steel fiber added concrete
SF2 – 0.5 % steel fiber added concrete
SF3 – 0.75 % steel fiber added concrete
SF4- 1 % steel fiber added concrete
SF5 – 1.5 % steel fiber added concrete
SF6– 2 % steel fiber added concrete
SF7– 2.5 % steel fiber added concrete
[pic]
Figure9.3: Graph showing the split tensile strength of M20 grade concrete with and without steel fiber
The Split tensile strength of various percentage Polypropylene fiber added concrete as given by the table9.4.
|Sl. no |Mix |Polypropylene fiber (%) |Tensile Strength (Mpa) |
| | | |At 3days |At 7 days |At 28 days |
|1. |CC |0 |1.5 |1.8 |3 |
|2. |PPF1 |0.25 |2 |3.8 |4.2 |
|3. |PPF2 |0.5 |2.2 |4 |4.23 |
|4. |PPF3 |0.75 |2.3 |4.1 |4.5 |
|5. |PPF4 |1 |3 |4.5 |5.2 |
|6. |PPF5 |1.5 |2.8 |4.4 |5.1 |
|7. |PPF6 |2 |2.72 |4.32 |5.02 |
|8. |PPF7 |2.5 |2.61 |4.2 |4.8 |
Table9.4: Split tensile strength of M20 grade concrete with and without polypropylene fiber
Where
CC – Control concrete
PPF1 – 0.25 % polypropylene fiber added concrete
PPF2 – 0.5 % polypropylene fiber added concrete
PPF3 – 0.75 % polypropylene fiber added concrete
PPF4 – 1% polypropylene fiber added concrete
PPF5 – 1.5 % polypropylene fiber added concrete
PPF6– 2 % polypropylene fiber added concrete
PPF7– 2.5 % polypropylene fiber added concrete
[pic]
Figure 9.4: Graphs shows the split tensile strength of M20 grade concrete with and without polypropylene fiber
[pic]
Figure 9.5: Photo views on compressive strength testing of specimens
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Figure 9.6: Photo views on split tensile strength testing of specimens
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Figure 9.7: Different photos views on compressive strength test
[pic] [pic]
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Figure 9.8: Different photos views on split tensile strength test
CHAPTER-10
CONCLUSION
The following conclusions have been drawn based on the experimental investigation carried out on concrete mixture.
1. Higher compressive strength is obtained for 1.5 % steel fiber and 0.5% for
Polypropylene Fiber added concrete.
2. Higher split tensile strength is obtained for 1.5 % steel fiber and 1% for
Polypropylene Fiber added concrete.
3. Concrete attained maximum compressive and split tensile strength when mixing
Minimum amount of polypropylene fiber compared to steel fiber.
CHAPTER-11
REFERENCE
1. IS 10262:1982 ‘Hand Book of Concrete Mix Design’, Bureau of Indian Standards, New Delhi
2. IS 383:2000, ‘Code of Practice for Plain and Reinforced Concrete’, (4th Revision), Bureau of Indian Standards, New Delhi.
3. IS 383:1970, Specification for coarse and fine aggregates from natural sources for concrete
4. IS 5816:1999 Splitting Tensile Strength of Concrete Test.
5. M.S. SHETTY (2000).,Concrete Technology, S.CHAND and Company Ltd.
M.L. GAMBHIR (1998) “Concrete Technology “, Tata McGraw-Hill
7. ACI Committee 2111, (1994) mechanical properties
and time dependent deformation of polypropylene fiber concrete. ACI Manual of Concrete Practice.
8. ACI Committee 544, (1982) properties of concretes containing polypropylene, steel and reengineered plastic shred fiber.
[pic]
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Polypropylene Fiber
Steel Fiber
Curing of Specimens
Test on Specimens
Casting of specimens
Analysis and discussion of test results
Conclusion
Fiber added with concrete at various %
Control concrete (without fiber)
Collection of materials
Mix proportions
(M20 grade of concrete)
Hardened concrete
1. Comprehensive strength test
2. Split tensile strength test
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