Vol 12, Issue 12, DEC / 2021 ISSN NO:

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Journal of E ngineering S cien ces

EXPERIMENTAL STUDY AND INVESTIGATION OF PERMEABILITY PROPERTIES OF FIBER REINFORCED LIGHT WEIGHT CONCRETE

G. RAVI TEJA ¹, G. DEEPTHI²

1. Student of M. Tech (Structural), Department of Civil Engineering, Universal College of Engineering and Technology,Dokiparru, Guntur, Andhra Pradesh 522005.

2. Assistant Professor, Department of Civil Engineering, Universal College of Engineering and Technology,Dokiparru, Guntur, Andhra Pradesh 522005.

Abstract:

Degradation of Concrete by the acid attack, the occurrence of reinforcement corrosion and associated damage of Concrete because of water intrusion is progressively being recognized as some of the threatening Durability problems in Reinforced Concrete Structures. High Performance Concrete is a novel construction material with improved properties like Higher Strength, Durability, Higher Constructability, etc. In the present investigation an exertion has been made to inquire about the joint impact of addition of silica fume and Steel Fibers on the Durability of SFR-HPC with regard to Impermeability of Concrete. A HPC of M40 grade was considered and Permeability test were performed to find the persistence of Steel Fiber Reinforced High Performance Concrete. The main variables considered in this study are. Four various proportions of Micro Silica viz. 0%, 5%, 7.5%, 10% by weight of Cement. Three different Aspect Ratios of Steel Fibers i.e. 60, 70, 80. Three different Volume Fractions of Fibers i.e. 0.5%, 0.75%, 1.0%.

Test results indicate that by adding of Micro-Silica to Plain Concrete up to 10% decreases its Permeability by about 52%. Further, addition of Micro Silica 5% and Steel Fibers fraction of 1.0%, reduces its Coefficient of Permeability from 10.48×10^-5 centimeter/second to 3.69×10^-5 centimeter/second. The reduction is about 35%. It is also noted that addition of 7.5% Micro Silica and Steel Fibers above 0.75%

fraction, results indicate in increase in Coefficient of Permeability value. Further experimental results reveal that addition of 10% Micro Silica along with Steel Fibers do not reduce the value of Coefficient of Permeability of Concrete. In all, the results of present investigation gave an insight on possible way of improving impermeability of Concrete by making use of mineral admixtures like Micro Silica in combination with Steel Fibers.

1.0 INTRODUCTION

Concrete production exists around the world as a leading material in construction for our infrastructure and essentially today, this man-made stone has risen as a most versatile and universally recognized tool to build with. The durability of concrete is characterized as the capacity of the material to stay workable for in any event the required lifetime of the structure. Likewise, its durability is fundamental in safeguarding the infrastructure of society. Amongst the different strategies to improve the Durability of Concrete, and to accomplish High Performance Concrete, the utilization of Micro Silica is a newly approach. In many situations, the durability of concrete is likewise legitimately identifying with its permeability which again depends a great deal upon its protection from entrance of dampness. The dampness which goes into the concrete can prompt to disintegration of steel reinforcement and diminishes the life of the structures radically.

In previous concrete, carefully controlled amounts of water and cementitious materials are used to create a paste that forms a thick coating around aggregate particles. A pervious concrete mixture contains little or no sand, creating a substantial void content. And that’s why it is also known as No fines Concrete. Using sufficient paste to coat and bind the aggregate particles together creates a system of highly permeable, Interconnected voids that drain quickly. For porous concrete, water permeability is the main specification requirement instead of its strength and continuity of the open pores is the main concern in the production of porous concrete.

Figure:1.1: Porous concrete

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In several cases, base layer is employed to grant a uniform support for rigid pavement structure. The increasing of traffic load will aim to the use of denser, more robust and anti-erosion base material as well.

The foundation material that contains large fine creates base layer with low permeability and slow water movement. The combination of trapped infiltration water and repeated traffic loading will generate void between base layer surface and surface layer base (erosion). The majority of infiltrated water that accumulated inside the void comes from pavement surface by infiltration through cracks, joints and gaps alongside the edge of pavement. Erosion phenomenon could lead to the loss of foundation support, pavement premature distress and short-term service life issue.

Pavement is the actual travel surface especially made durable and serviceable to withstand the traffic load commuting upon it. Pavement grants friction for the vehicles thus providing comfort to the driver and transfers the traffic load from the upper surface to the natural soil. In earlier times before the vehicular traffic became most regular, cobblestone paths were much familiar for animal carts and on foot traffic load.

Pavements are primarily to be used by vehicles and pedestrians. Storm water drainage and environmental conditions are a major concern in the designing of a pavement. The first of the constructed roads date back to 4000 BC and consisted of stone paved streets or timber roads.

Rigid Pavement:

Rigid pavements have sufficient flexural strength to transmit the wheel load stresses to a wider area below.

Compared to flexible pavement, rigid pavements are placed either directly on the prepared sub-grade or on a single layer of granular or stabilized material. Since there is only one layer of material between the concrete and the sub-grade, this layer can be called as base or sub-base course in rigid pavement, load is distributed by the slab action, and the pavement behaves like an elastic plate resting on viscous medium Rigid pavements are constructed by Portland cement concrete (PCC) and should be analyzed by plate theory instead of layer theory, assuming an elastic plate resting on viscous foundation.

Rigid Pavement

 Deformation in the sub grade is not transferred to subsequent layers

 Design is based on flexural strength or slab action

 Rigid pavement carries high flexural strength

 No such phenomenon of grain-to-grain load transfer exists

 Have low repairing cost but completion cost is high Need Of Porous Concrete

In rural areas larger amount of rainwater ends up falling on impervious surfaces such as Parking lots, driveways, sidewalks, and streets rather than soaking into the soil. This creates an imbalance in the natural ecosystem and leads to a host of problems including erosion, floods, ground water level depletion and pollution of rivers, as rainwater rushing across pavement surfaces picks up everything from oil and grease spills to de-icing salts and chemical fertilizers. A simple solution to avoid these problems is to stop constructing impervious surfaces that Block natural water infiltration into the soil. Rather than building them with conventional concrete, we should be switching to Porous Concrete or Porous Pavement, a material that offers the inherent durability and low life-cycle costs of a typical concrete pavement while retaining storm water runoff and replenishing local watershed systems. Instead of preventing infiltration of water into the soil, porous pavement assists the process by capturing rainwater in a network of voids and allowing it to percolate into the underlying soil.

Applications

 Porous concrete has had numerous useful non-pavement applications including buildings, tennis courts, drains & drain tiles, floors in greenhouses, slope stabilization, swimming pools decks, zoo areas etc.

 The majority of porous concrete applications are parking lots, sidewalks, pathways, parks, shoulders, drains, noise barriers, friction course for highway pavements, permeable based under a normal concrete pavement and low volume roads.

 Water and Power resources services in America successfully tested the use of drains and drain tiles constructed from porous concrete beneath hydraulic structures.

Objectives of the present work

Coming up next are the motivation behind the present examination:

 To evaluate the influence of various Percentages of Micro Silica on the Permeability of Concrete.

 To examine the influence of different proportions of Silica Fume in combination of various Percentages of Steel Fibers Fractions on Permeability of Concrete.

 To arrive at best combination of Silica Fume and Steel Fiber content for improved Durability.

2.0 Literature Review

As mentioned earlier in the Section 1.6, need for the present study is ascertained on the basis of research reports that are available on strength & durability characteristics of concrete containing admixtures like

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Micro Silica & Steel Fibers. In order to plan the experimental program and attain the objectives defined, a comprehensive literature survey is essential. Hence in the following text detailed literature review on strength & durability characteristics of concrete having different admixtures is presented. Prasad, B.K. [1]

have taken up an examination to explore the impact of replacement of cement with silica fume in the production of High Strength Concrete. The replacement levels chosen were 0% to 20% in the increment of 5%. Thus, a total of four mixtures, two of controlled concrete with and rest of two specimens with Micro Silica concrete were used. Venkatesh Babu [2] examined on mechanical properties of High-Performance Concrete mixes, with various substitution levels of Ordinary Portland cement with Condensed micro silica of grade 960D. The Compressive strength, split Tensile strength and Flexural strengths of the mixes were examined according to IS specifications. The following interpretation were done by the authors.

Mohammed Reza [3] completed an examination on the effect of 15% Micro Silica on the mechanical strength of concrete made with Sulphate resisting cement. For this a total of 150 cubes were cast, 75 cubes with sulpate resisting cement and rest 75 cubes with sulphate resisting cement and Micro Silica. The compressive strength was observed at 14 days, 28days, 180days, and 360days. Al Mutairi, Bufarsan [4] as driven a trial examination to consider about the distinctive of different rates of Fine/Coarse Tire waste and silica rage at different temperatures on the Compressive Quality of concrete. The Compressive quality of concrete blends made with tire Elastic was surveyed with those of concrete containing silica fume and conventional concrete to get to the comfort of reusing elastic waste as a piece of concrete. M.I Khan [5]

has contemplated on porousness related properties of Superior Solid utilizing Fly ash and silica fume as cement supplanting materials. Oxygen Porousness and Porosity of Cement consolidating Fly ash and silica smoke orchestrated with different water binder proportions were settled. The decrement in the Penetrability was progressively noticeable when silica fume was joined at up to 10% substitution level. Above 10%

expansion of small-scale Silica, the decrement level was marginal.8% to 12% Micro Silica gave the perfect execution, realizing the exceptionally less Porousness esteems for all degrees of Fly ash remains. For porosity test, the fuse of up to 10% micro-Silica showed decline in the porosity at all ages.

3.0 MATERIALS AND METHODS

The following experimental program was made to find out the durability property of concrete in terms of Permeability by usage of Micro Silica as Partial Cement replacement material along with Steel Fibers.

Materials used: The materials utilized in the test program are Cement, Coarse Aggregates, Fine Aggregates, Water, Micro Silica, Steel Fibers, Super plasticizer.

Steel fibers: Straight Galvanized iron Steel Fibers chopped in three different sizes with Aspect Ratio viz.

60, 70, 80, was used.

Super plasticizer: it Complots SP-337 Manufactured by Fosroc Chemicals (India) Limited, Bangalore, was utilized as water reducing agent to achieve the required Workability.

CONCRETE MIX DESIGN

Using the Properties of Cement and Aggregates, Concrete mix design of M40 grade was designed as per IS 10262. The mix design procedure and calculations are shown in Appendix A. The following proportions by weight were obtained.

Cement Fine aggregate Coarse aggregate Water-Content W/C

Ratio

450 kg/m³ 412.12 kg/m³ 1340.14 kg/m³ 186.5 kg/m³ 0.41

By using these proportions, a Trial mix was carried out and Compressive strength was determined. It was found that compressive strength for 7 days was very high with these proportions. So, again by doing trials with different water content, final proportions satisfying the strength requirements were obtained. The final proportions are as given below.

Cement Fine aggregate Coarse aggregate Water-Content W/C

Ratio

450 kg/m³ 417 kg/m³ 1356 kg/m³ 178 kg/m³ 0.39

The above mix proportions were used throughout the experiment.

Concrete mix cases: As stated earlier, the present investigation aims at understanding the impact of Micro Silica and Steel Fibers on Coefficient of Permeability of Various grades of Concrete. Accordingly, a total of 13 mix cases including one controlled concrete mix were designed by considering Micro Silica in various percentages viz.5%, 7.5%, 10%, combined with Steel Fibers having three different Aspect Ratios i.e. 60, 70, 80. Various percentage fractions of Fibers were also varied from 0.5% to 1.0% for each Aspect Ratio of Fibers to understand its importance on Permeability of concrete.

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Table 3.1: Details of Mix Cases

CASTING AND CURING OF TEST SPECIMENS: Using the mix proportions and quantities of ingredients tabulated in Table3.8 for various mix cases, concrete of desired grade is produced and specimens for Permeability test are cast. In all 39 cylinders of size 100millimeter Ø x 100millimeter ht. are cast. The detailed procedure of concrete mixings, casting and testing is described in the following text.

Table 3. 2Quantities of Concrete Ingredients for Three Cylinder Specimens

Mixing of materials: Various constituents of concrete mixtures were weigh batched accurately as tabulated in Table 3.8. Cement, Fine Aggregate, Coarse Aggregate, Micro Silica was mix thoroughly.

Fibers are then added to the mix in required proportions. After through dry mixing, little quantity of water from a required quantity was added to the mix. After mixing, remaining quantity of water along with Super Plasticizer was added and it is then overturned and mixes well till a homogeneous mix was obtained. This

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homogeneous concrete was used for casting of specimens.

Casting of specimens: The homogeneous mix obtained was used to cast the cylinder specimen of size 100mm diameter×100mm height which meets the requirements of Cement Mortar and Concrete Permeability Apparatus as per IS 13382:2018 The wet mix was filled into the moulds in layers. Table vibrator was used for doing the compaction of concrete.

CURING: After 24 hours of casting, the specimens were demolded and labeling was done as per the mix cases and immersed in the water tank for curing.

Permeability test Preparation of specimen

Once the curing is done for 28 days, the specimens were removed from the curing tank and it was kept for drying for few hours. The surface was cleaned and dust particles and deposits were removed. The sharp edges of the cylinders at the joints were smoothened. Care had been taken to smoothen the edges to round shape. After drying the thread was wound around the specimen densely to fit it in the Permeability apparatus cell with no gaps. However, to ensure that gap between the specimen and cells are closely air tight, molten sealing compound was poured. The whole set up was tested for water leakage through the gaps between specimen and cell walls by pounding water over one of the surfaces of the specimen. After it ensures that no leakage is taking place, the cell is capped with cover plate and tightened properly to ensure no leakages from the sides. The whole set up of Permeability cell with specimen is ready for running the Permeability test.

Testing of specimens: The permeability cell with specimen made ready as stated above is placed in the permeability test set up and water pipe was attached to a water reservoir of Permeability test setup. The water reservoir of Permeability test setup was loaded with distilled water and the standard test pressure of 10kilogram/centimeter-square was maintained in the water reservoir. This may anyway can be decreased as much as 5 kilogram/centimeter-square in case of more Penetrable Specimens, and may be increased up to 1515kilogram/centimeter-square for less Permeable Specimens.

4.0 TEST RESULTS AND ANALYSIS

The following testing procedure was undertaken during the cube compression testing: The measuring and testing of test specimens was undertaken as soon as possible after being removed from curing. All specimens were tested in a wet condition and excess water removed from the surface. The dimensions of the test specimens were measured and recorded. The platens were cleaned when necessary to ensure no obstruction from small particles or grit.

 Any loose particles were removed from the uncapped bearing surfaces of the specimens. It was ensured there was no trace of lubricant on the bearing surfaces.

 The specimens were centered on the bottom platen of the testing machine. The upper platen was lowered until uniform pressure was provided on the specimen.

 A force was applied at the required rate shown by the rotating disc on the testing machine.

Figure 4.1 : Compressive Strength Test

The water is poured into the measuring jar, while the knob should be kept open so as to expel the air out.

Hence creating a constant head. Then the knob is closed and the water is poured in the jar to 1000ml, now having kept the stop watch ready, the knob is opened and1000ml of water is allowed to flow and time required for the water to percolate through the sample is noted down.

Coefficient of permeability: The rate of flow under laminar flow conditions through a unit cross sectional area of porous medium under unit hydraulic gradient is defined as coefficient of permeability.

where, k=coefficient of permeability (cm/sec) a= area of graduated cylinder (cm2)

l=length of the specimen (cm)

h1=length between bent portion of the collector pipe and the 1000ml mark on the measuring jar (cm)

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h2=length between bent portion to the top of the specimen (cm)

Figure 4.2: Non porous Concrete Cubes

Figure 4.3: Porous Concrete Cubes

Figure 4.4: Curing days Cubes

Table 4.1: Compressive Strength Test in M40 Grade porous concrete Cube S. No Curing days Load (KN) Compressive test

(N/sq.mm)

1 7 Days 330.0 38.10

320.0 38.15

315.0 39.84

2 28 Days 920.0 40.89

918.0 40.80

909.0 40.40

3 56 Days 1110.0 49.33

1090 48.44

1120.0 49.78

Figure 4.5: Compressive Strength Test in porous concrete 7 Days

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Figure 4.8: Comparison of different Curing Days in porous concrete Compressive Strength Test Flexural Test:

Flexure (Bend) tests are generally used to determine the flexural modulus or flexural strength of a material.

A flexure test is more affordable than a tensile test and test results are slightly different. The material is laid horizontally over two points of contact (lower support span) and then a force is applied to the top of the material through either one or two points of contact (upper loading span) until the sample fails. The maximum recorded force is the flexural strength of that particular sample.

Purpose of a Flexural Test

The most common purpose of a flexure test is to measure flexural strength and flexural modulus. Flexural strength is defined as the maximum stress at the outermost fiber on either the compression or tension side of the specimen. Flexural modulus is calculated from the slope of the stress vs. strain deflection curve.

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These two values can be used to evaluate the sample materials ability to withstand flexure or bending forces

Table 4.2: Flexural Strength Test in m40 Grade porous concrete

Cube S. No Curing days Load (KN) Flexural Strength

(N/sq.mm)

1 7 Days 240.0 25.3

240.0 25.2

280.0 25.6

2 28 Days 420.0 40.89

460.0 42.0

510.0 40.40

3 56 Days 700.0 55.0

730.0 48.44

750.0 58.0

Figure 4.9 : Flexural Strength Test in porous concrete 7 days

Figure 4.10: Flexural Strength Test in porous concrete 28 days

Figure 4.11: Flexural Strength Test in porous concrete 56 days

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Figure 4.12: Flexural Strength Test in porous concrete in different Curing days Split Tensile Strength Test:

The split tensile strength at which failure occurs is the tensile strength of concrete. In this Investigation the test is carried out on cylinder by splitting along its middle plane parallel to the edges by applying the compressive load to opposite edges as per IS: 516-1959

Table 4.3: Split Tensile Strength Test in M40 Grade porous concrete Cube S. No Curing days Load (KN) Split Tensile Strength

(N/sq.mm)

1 7 Days 240.0 2.3

240.0 2.2

280.0 2.6

2 28 Days 420.0 4.89

460.0 4.0

510.0 4.4

3 56 Days 700.0 5.7

730.0 4.4

750.0 5.2

Figure 4.13: Split Tensile Strength Test in porous concrete in curing in 7 days

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Figure 4.16 Split Tensile Strength Test in porous concrete in curing in different days

DISCUSSIONS:

It was found that there was very strong correlation between void content and permeability at the age of 7- days and 28-days which created fine likelihood to use void content to represent porous concrete permeability behavior. Greater fresh density created smaller void and small void would reduce permeability. High void content with a good connection resulting weaker aggregate interlocking inside the mixture so that the permeability increased and the compressive strength decreased. On the other hand, compact fresh density with a good aggregate interlocking increased the compressive strength value. It was happened because the void inside fresh concrete mixture with a bigger density was filled by cement paste and aggregate It was found that there was very strong correlation between void content and permeability at the age of 7-days and 56-days which created fine likelihood to use void content to represent porous concrete permeability behavior. Greater fresh density created smaller void and small void would reduce permeability. High void content with a good connection resulting weaker aggregate interlocking inside the mixture so that the permeability increased and the compressive strength decreased. On the other hand, compact fresh density with a good aggregate interlocking increased the compressive strength value. It was happened because the void inside fresh concrete mixture with a bigger density was filled by cement paste and aggregate Strong correlation between fresh density towards void content and permeability at the age of 28-days opened a fine potency to use the fresh density as a reference to set the desired porous concrete void content on the field.

CONCLUSIONS

These are the following Conclusions are given from the test outcomes and discussions.

 Addition of 5% Micro Silica reduces the Coefficient of Permeability to 9.46×10^-5 cm/sec, when compared to 10.48×10^-5 cm/sec for sample without silica fume. As the addition of silica fume increases to 7.5% and 10%, the coefficient of Permeability reduces to 7.61×10^-5 centimeter/second and 5.42×10^-5 centimeter/second, respectively. The reduction is about 48%.

 Adding of 10% silica fume and Steel strands having Aspect Ratio of 80 does not have much effect on Permeability of Concrete. The value slightly reduces to 9.72×10^-5 centimeter/second, 9.62×10^-5 centimeter/second, 8.42×10^-5 centimeter/second, when compared to 10.48×10^-5 centimeter/second, for concrete specimen without Micro Silica and Steel Fibers.

 Steel Fibers Aspect Ratio also affects the Coefficient of Permeability value. Steel fibers having Aspect Ratio 60 and 5% Micro Silica, the permeability value decreases. But further adding of

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Micro Silica 7.5%, 10% and Steel Fibers having Aspect Ratio 70 and 80, the Permeability value increases respectively.

 For a given Aspect Ratio of Steel Fiber, Permeability of Steel Fiber Reinforced Concrete composites decrements as the Volume portion of strand increments. The rate of decrease of Permeability however decreases with the incrimination of Fiber content.

 The best combination obtained from the test results is with the addition of 5% Micro Silica and Fibers volume fraction 1.0% and having Aspect ratio 60.

Future Scopes of The Work

 Further studies on durability of Concrete in terms of Permeability to verify the influence of other mineral admixtures with or without Fibers.

 Studies on Performance of Concrete in terms of improving impermeability of Concrete can be carried out by using other type of Fibers in combination of mineral admixtures.

 Investigation on durability of Concrete in terms of Coefficient of permeability may be extended to wide range of various grades of Concrete containing mineral admixtures and Fibers.

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