Mechanical Properties of Concrete with Steel Fibers

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Questions and Answers

What is the percentage weight of SiO₂ in the cement composition?

21.1 (correct)

3.81

64.1

19.42

Which compound is found in the highest percentage in the cement composition?

C3S

C2S (correct)

C3A

Al₂O₃

What is the limit for Al₂O₃ content according to the Iraqi standard No. 5/2019?

2.2%

3.4%

5.4%

3.5% (correct)

Which of the following compounds exceeds the standard limit established for it?

C4AF Signup and view all the answers

What is the percentage of MgO in the cement composition?

2.2% Signup and view all the answers

What is the main effect of adding DSF to concrete according to the results?

It leads to a slight increase in modulus of elasticity. Signup and view all the answers

Which fiber percentage showed the highest increase in modulus of elasticity?

0.5% DSF showed a 3.06% increase. Signup and view all the answers

How did the tensile strength of concrete vary with different percentages of DSF?

It showed an increase with the addition of both 0.25% and 0.5% DSF. Signup and view all the answers

What trend was observed regarding the modulus of elasticity values for the specimens reinforced with DSF?

Values increased modestly with both 0.25% and 0.5% DSF. Signup and view all the answers

What can be concluded about the air voids in concrete with increasing DSF content?

Air voids decreased significantly with any addition of DSF. Signup and view all the answers

What is one primary benefit of incorporating fibers into concrete?

Enhances compressive strength Signup and view all the answers

What percentage increase in compressive strength can be achieved by using steel fibers according to the findings?

10–25% Signup and view all the answers

Which type of fibers is mentioned as commonly used in concrete improvement?

Steel fibers Signup and view all the answers

What is a limitation of using industrial steel fibers (ISF) in concrete construction?

Limited supply in many regions Signup and view all the answers

How much steel fiber is contained in each tire for normal and heavy cars respectively?

15-25% Signup and view all the answers

What aspect of concrete does the addition of steel fibers NOT improve?

Cost of materials Signup and view all the answers

In increasing water-to-cement ratios, what mechanical property was significantly changed by the addition of steel fibers?

Tensile strength Signup and view all the answers

What is a critical reason for researching alternative fibers to industrial steel fibers?

Increased availability and lower costs Signup and view all the answers

What was the primary purpose of the study presented in the paper?

To assess the mechanical properties of normal concrete with discarded steel fibers Signup and view all the answers

How many different volume fractions of discarded steel fibers were used in the study?

Two Signup and view all the answers

What effect did the addition of discarded steel fibers have on the compressive strength of the concrete?

It enhanced compressive strength by 8.8% and 3.3% Signup and view all the answers

What was the change in workability of the concrete when discarded steel fibers were added?

Workability decreased at all added ratios Signup and view all the answers

By what percentage did the modulus of elasticity increase for the concrete mixes incorporating discarded steel fibers?

3.06% and 2.25% Signup and view all the answers

Which property of concrete was significantly improved by the addition of discarded steel fibers?

Splitting tensile strength Signup and view all the answers

What was the increase in modulus of rupture for the concrete with fiber volume fractions of 0.5%?

25.58% Signup and view all the answers

What is one characteristic of the discarded steel fibers used in the study?

They have a length of 40 mm and a diameter of 0.92 mm Signup and view all the answers

What effect does increasing the content of DSF have on the workability of the concrete mixture?

It decreases workability. Signup and view all the answers

How much does the addition of 0.25% DSF increase the compressive strength of the concrete mixture compared to the reference mix?

8.8% Signup and view all the answers

What happens to the compressive strength when increasing the DSF content from 0.25% to 0.5%?

It decreases compared to 0.25%. Signup and view all the answers

What improvement in splitting tensile strength is noted with the addition of DSF?

Significant improvement. Signup and view all the answers

Which of the following observations related to density and modulus of elasticity was made with DSF addition?

Both increased slightly. Signup and view all the answers

What is suggested for future work regarding the use of DSF in concrete?

Investigate higher ratios of DSF such as 0.75% and 1%. Signup and view all the answers

What was the flexural strength of the mix with 0.5% DSF?

5.4 MPa Signup and view all the answers

Which mix shows the highest flexural strength increase?

Mix 3 Signup and view all the answers

What was the compressive strength of Mix1?

45 MPa Signup and view all the answers

What percentage increase in compressive strength was observed for Mix2 compared to Mix1?

8.8% Signup and view all the answers

How does the addition of DSFs affect the tensile strength of concrete?

It significantly improves the tensile strength. Signup and view all the answers

What is one primary disadvantage of concrete mentioned in the content?

Poor resistance to tensile forces Signup and view all the answers

In the study, which mix type had the highest recorded splitting tensile strength increase?

Mix3 Signup and view all the answers

What was the splitting tensile strength increase observed at a volume fraction of 0.25% DSFs?

7.89% Signup and view all the answers

What failure mode was observed in plain concrete specimens under tensile stress?

Splitting into two pieces Signup and view all the answers

What role does the fiber addition play in concrete's performance under tensile stress?

It improves resistance to tensile stress. Signup and view all the answers

Study Notes

Experimental Investigation on Mechanical Properties of Normal Concrete Reinforced with Discarded Steel Fibers

This study investigated the mechanical properties of normal concrete reinforced with discarded steel fibers (DSFs) from tire manufacturing.
DSFs were added to concrete in two different volume fractions (0.25% and 0.5%), with fiber dimensions of 40mm length and 0.92mm diameter.
Compressive strength increased by 8.8% and 3.3% with the addition of DSFs.
Workability of concrete decreased with increasing fiber volume fraction.
Density showed slight changes.
Modulus of elasticity showed slight increases (3.06% and 2.25%).
Splitting tensile strength and modulus of rupture significantly improved with DSF addition.
Splitting tensile strength increased by 7.89% and 23.68% for 0.25% and 0.5% DSF, respectively.
Modulus of rupture increased by 6.67% and 25.58% for 0.25% and 0.5% DSF, respectively.
Using discarded fibers as an alternative to industrial fibers improves concrete mechanical properties.

Introduction

Concrete is a brittle material with low tensile and strain capacities.
Adding fibers (steel, glass, polypropylene, synthetic) can improve these properties.
Steel fibers are commonly used to enhance concrete's flexural strength, toughness, post-cracking behavior, and ductility.
Recycled steel fibers (RSF) from end-of-life tires are a sustainable alternative to standard steel fibers (ISF).
However, the supply of industrial steel fibers and their cost can be a limitation.
Discarded steel fibers (DSFs) are used in this study as an alternative to ISF and RSF.
A significant amount of steel is used in tires, and this waste material could be a sustainable solution.

Experimental Program

Ordinary Portland Cement (Type I) was used as a cement.
Local fine and coarse aggregates and SikaViscoCrete-5930 superplasticizer were used.
Discarded tire steel fibers (DSFs) were utilized in 0.25% and 0.5% volume fractions of concrete.
Several types of specimens were prepared (cubes, cylinders, prisms) of different sizes to test different properties.
The mixing procedure involved a series of steps, mixing ingredients in a set order, and time durations.

Results and Discussions

Fresh Properties: The inclusion of DSFs decreased slump, reducing concrete workability.
Density: Density showed a slight increase with the addition of DSFs.
Compressive Strength: The compressive strength increased by 8.8% and 3.3% for 0.25% and 0.5% DSF, respectively. This was attributed to the fibers' interaction with the matrix and their ability to prevent cracking.
Splitting Tensile Strength: A significant increase in splitting tensile strength was observed with higher DSF content.
Modulus of Elasticity: A slight increase in the modulus of elasticity was found with the incorporation of DSFs.
Modulus of Rupture: Modulus of rupture saw a substantial improvement with the addition of DSFs in both ratios.
Failure Modes: The addition of DSF altered failure mechanisms, changing from sudden cracking to more gradual failure.

Conclusions

Workability decreased with DSF inclusion.
Compressive strength improved with DSF addition, though higher percentages may lead to decreased strength.
Splitting tensile strength and modulus of rupture showed significant improvements.
DSFs are a viable alternative to other fibers for improving concrete's mechanical properties, making use of waste materials.

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Description

This quiz explores the mechanical properties of normal concrete reinforced with discarded steel fibers. The study focuses on how different volume fractions of steel fibers impact compressive strength, workability, and tensile strength. Test your knowledge on the effects of adding discarded fibers from tire manufacturing to concrete!