Influence of Crimped Steel Fibre on Properties of Concrete ...

If you are looking for more details, kindly visit our website.

Abstract

This research was inspired by the growing global shortage of natural aggregates. Different types of waste ceramics (apart from recycled concrete) are gaining popularity as materials for producing waste aggregates to potentially replace natural ones. The study aimed to analyze the efficiency of various aggregate mixes of waste and natural materials, focusing on two types of waste ceramic aggregates. These concrete mixes were prepared based on unique aggregate blends (a mix of natural aggregate, porous and iron oxide-rich (red) waste ceramic aggregate, and dense, kaolin-based (white) waste ceramic aggregate). All aggregates underwent thorough testing before being utilized in concrete mix creation. Four different aggregate blends were used to prepare concrete mixes via a simplex experimental design. These mixes were further modified by adding varying amounts of crimped steel fiber. The properties of hardened steel fiber-reinforced concrete (SFRC), such as density, compressive strength, shear strength, ultrasound propagation velocity, dynamic modulus of elasticity, and limit of proportionality during flexural testing, were of particular interest. Tests adhered to European and Japanese standards, and the achieved fiber-reinforced concretes displayed satisfactory strength characteristics, enabling the substitution of traditional reinforcement; strength classes according to the fib Model Code 2010 were assigned.

Keywords:

aggregate, white ceramic, red ceramic, waste, fibre, SFRC

1. Introduction

There is a growing global effort to efficiently utilize various ceramic wastes in the construction industry, leading to some successful applications of waste ceramics as partial or full replacements for fine and coarse natural aggregates. Red (porous, iron oxide-rich) ceramic waste is the type most often considered for use as a waste aggregate, often used in casting nonstructural concrete elements with lower strength requirements. To produce structural concrete from waste ceramic aggregates, a novel approach to composition is necessary. By blending different waste ceramic aggregates (e.g., red and white ceramic), a higher quality of sustainable concrete can be achieved, leveraging each aggregate's strengths and creating synergy. Red ceramic, though limited in compressive strength due to its porosity, offers internal curing benefits, while white ceramic, with "no porosity," provides much higher compressive strength. This study aims to validate using waste ceramic aggregates—red ceramic from brick production waste and white ceramic from local pottery factory waste—as aggregates in concrete. Both types of ceramics were processed uniformly to generate waste aggregates. As a baseline, natural post-glacial aggregates prevalent in southern Baltic Sea regions were used. A mixture design was employed, utilizing three aggregates, where the volumes of all three components always equaled 100%. This design enabled result visualization through ternary contour plots, commonly used in binder and concrete technology.

The research was conducted in two primary stages. The first stage focused on assessing the geometrical and mechanical characteristics of the waste and natural aggregates. The second stage evaluated the properties of concretes made from these tested aggregates. The analysis explored the feasibility of replacing natural aggregates with waste ceramic aggregates. Specific mixtures of waste ceramic and natural aggregates were proposed for concrete production, with four blends eventually selected. These four mixes were then modified by adding steel fibers in varying volumes (from 0.5% to 1.5% Vf). Altogether, 16 concrete mixes were cast to test the properties of concretes in their hardened state.

3. Experimental Design

An ordinary integral simplex design (also known as a mixture design) [21] was utilised in this research. The three types of aggregate were named as follows: X—red ceramic waste; Y—natural aggregate; Z—white ceramic waste. Due to the different specific gravity values of red ceramic waste, white ceramic waste, and natural aggregate, the materials were dosed by volume. The specific property of the mixture design was that the sum of the volume of all three ingredients was always equal to 100%. In this case, the three aggregates played the roles of the ingredients.

Table 3

Mix No.Aggregate (%)Natural AggregateWhite Ceramic WasteRed Ceramic WasteI10000II03367III67330IV343333Open in a separate window

The object of the experiment was considered to be a complex composite material. The internal structure of the material was unavailable (for unknown reasons) to observers, with only the “input” and “output” parameters known to observers [22,23]. All achieved experimental results were statistically processed. The Smirnov–Grubbs criterion was used to assess gross error of the values. The sequence of specific test realisations was decided using a digital random number generator to guarantee objectivity. All calculations associated with the execution of the research and graphic interpretation of the mathematical model were carried out using the Statistica 12 software suite. Contour plots were created using a polynomial fit with fitted functions characterised by a correlation coefficient of at least 0.80. This type of experimental design was successfully used numerous times in concrete technology, including concretes based on waste aggregates and steel fibre-reinforced concretes [21]. The number, shape, and size of specimens utilised for each test are presented in .

Table 4

Type of TestSpecimen Shape (cm)Number of SpecimensStandardIn One TestTotalDensityCube 15 × 15 × 15
Beam 70 × 15 × 15393123-7:2011 *Compression strengthCube 15 × 15 × 15348406-3:2011 *Shear strengthBeam 70 × 15 × 153484JI-SF6:1984 **Ultrasound propagation velocityBeam 70 × 15 × 15348404-4:2005 *Dynamic modulus of elasticity ***Beam 70 × 15 × 15348404-4:2005 *Flexural strength: LOP
(limit of proportionality)Beam 70 × 15 × 15348451:2007 *Open in a separate window

All specimens were tested after 28 days of curing (first day in a plastic mould covered by a polyethylene sheet, then 27 days in a water tank) in a temperature of 20 °C ± 0.5 °C. After curing, specimens were measured, weighed, and dried to avoid problems during the ultrasound velocity test. The calculated density was a general quality test of the prepared specimens, with the value of density also useful for the ultrasound propagation velocity test and for computing the dynamic modulus of elasticity value. The shear strength test was performed on half of the beams that remained after the flexural test. Concrete mixes were modified by adding steel fibres to proportions of 0.5%, 1%, and 1.5%. The achieved results were subsequently compared with results obtained by other researchers working on steel fibre-reinforced concrete. Altogether, 16 concrete mixes were cast in order to test the properties of steel fibre-reinforced concrete (SFRC) in the hardened state.

5. Discussion

Four residual strengths (fR1, fR2, fR3, fR4) associated with particular CMOD values (0.5, 1.5, 2.5, and 3.5 mm) are not feasible for the direct design of an SFRC mix. There is general agreement among the global SFRC research community that the first residual strength fR1 is important in terms of service conditions, whereas the third residual strength fR3 is recognised as a key factor for the assessment of ultimate conditions. The “fib Bulletin 55, Model Code 2010” proposed the utilisation of the first and third residual strengths to calculate both the serviceability limit state (SLS) and the ultimate limit state (USL). Basically, the ratio fR3/fR1 was defined to describe the relationship between the behaviour of SFRC at ULS and SLS [32,33].

The proposed fib strength classification of SFRC consisted of two elements, i.e., strength interval (namely fR1) and post-cracking softening or hardening behaviour, which was described by a letter symbol from a to d directly referring to the fR3/fR1 ratio. Letter a represents the strongest softening and letter d represents the strongest hardening [34].

When the fibre reinforcement was efficient enough, substitution of traditional bar and stirrup reinforcement was enabled. Two following conditions were fulfilled simultaneously to pass the substitution threshold:

fR1 / fLOP > 0.4

(2)

fR3 / fR1 > 0.5

(3)

Calculated values of the above factors for tested concretes are presented in with the associated strength class and reinforcement substitution.

Table 5

Concrete Symbol fR3/fR1 fR1/fLOP fLOP (MPa)Strength ClassReinforcement SubstitutionI0.7830.9786.2166.0bEnabledII0.6960.5973.6533.0aEnabledIII0.7881.0055.4525.0bEnabledIV0.7611.0275.6585.0bEnabledOpen in a separate window

The achieved strength classes and enabled traditional reinforcement substitutions allowed for the utilisation of the tested concretes for structural applications. The wise use of different blends of ceramic waste and natural aggregates to shape the properties of cast concretes is possible. The proposed approach toward ceramic waste aggregates merged the advantages of internal curing and fibre reinforcement and was proven to be efficient.

6. Conclusions

The following conclusions can be drawn from the research described in this paper:

• It is possible to cast composites based on multiple waste aggregates;

• A blend of waste ceramic aggregates achieved a greater flexural strength of a cement composite than ordinary natural sand;

• The highest compressive strength was achieved using only natural aggregates;

• The compressive strength of the tested concretes was significantly influenced by the composition of the aggregate mix, as evidenced by the concrete with 1.5% fibre composition, whereby the values ranged from 17.5 MPa to 85.3 MPa;

• It is possible to partially or fully substitute natural aggregates with white or red ceramic wastes;

• The composites created on the basis of the white and red ceramic wastes are characterised by satisfactory mechanical properties, allowing for the assignment of standard strength classes according to both the EN and fib Model Code 2010;

• The research programme should be continued using greater specimens, focusing on more complicated mechanical characteristics (e.g., dynamic properties) of composites to enable full-scale modelling.

Acknowledgments

The authors would like to thank Katarzyna Maciejewska and Elzbieta Kuźmińska for their help in the preparation of the specimens and during some of the conducted testing procedures.

Author Contributions

Conceptualization, J.K. (Jacek Katzer); Data curation, J.K. (Jacek Katzer) and J.K. (Janusz Kobaka); Formal analysis, T.P.; Funding acquisition, T.P.; Investigation, J.K. (Janusz Kobaka); Project administration, T.P.; Software, J.K. (Janusz Kobaka); Writing – original draft, J.K. (Jacek Katzer); Writing – review & editing, J.K. (Janusz Kobaka). All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding

Conflicts of Interest

The authors declare no conflict of interest

Product Description

◆ Description

Crimped steel fibers are low-carbon, cold-drawn steel wire fibers designed to provide temperature and shrinkage crack control, strengthen flexural reinforcement, increase shear strength, and improve crack resistance of concrete. Crimped steel fiber conforms to the standards outlined in ASTM C1116 (Standard Specification for Fiber Reinforced Concrete and Shotcrete) and ASTM A820 Type V (Standard Specification for Steel Fibers for Fiber Reinforced Concrete). These coarse steel fibers enhance impact resistance, shatter resistance, fatigue resistance, and abrasion resistance, contributing overall to increasing concrete toughness. The recommended dosage ranges from 25 to 100 lb/cubic yards (15 to 60 kg/m³), depending on specific project requirements.

Crimped steel fiber is widely used in buildings, road surfaces, bridges, tunnels, airport road surfaces, water conservancy projects, military engineering, and various building products.

 

◆ Specification:

Name

Crimped Steel Fiber (milling)

Material

Carbon steel 

Length

30-60mm

Diameter

0.5-0.7mm

L/D

30-80

Tensile strength

>800Mpa

shape

wave

Standard

ASTM A820

 

◆ User's guidance

• Dosage: dependent on application, the general mixing amount is 0.1%-1%.

• Mixing: When pouring sand and aggregates into the hopper, mix an appropriate amount of loose steel fibers evenly, then add cement. Place it in a mixing table, dry and mix for 2 minutes. If using rowed steel fibers, add them after water addition to dissolve the bonding glue.

If you are looking for more details, kindly visit well.

• Transport the mixed fiber concrete via conveyor.

• Concrete pouring and laying should be compacted.

 

◆ Reference standards

• EN 14889-1:2006

• EN 14651-2005

• ASTM A820

 

◆ Advantages

• Improves impact resistance, crack resistance, and abrasion resistance of concrete.

• Reduces segregation, plastic settlement, and shrinkage cracking of concrete.

• Provides three-dimensional reinforcement to prevent macro-cracking.

• Enhances durability, fatigue resistance, and flexural toughness.

• Cuts site costs compared to screens used for temperature/shrinkage crack control.

• Easily incorporated into concrete mixtures before placement.

 

◆ Features

High strength

Strong toughness

Good ductility

Long-lasting freeze-thaw resistance

Heat resistance and abrasion resistance

Cavitation resistance 

Corrosion resistance

Compression and impact resistance

 

◆ Application:

- Industrial and commercial floors

- Sprayed concrete (Shotcreting) in tunnels and mines

- Precast concrete products

- Bridges, Culverts, and Hydrodynamic structures

- Seismic resistance structures

- Highways & Airport pavements

- Concrete/shotcrete

- Heavy equipment foundation.

 

 

◆ Packaging

20kg per bag/carton or as required, with 50 bags or 1000kg per pallet, 24 tons per 20' container

 

 

◆ Certificate

CE, ISO9001, MA

 

◆ Exhibition

• April 16-18, 2021 Spring HK exhibition

• April 18-19, 2023 The 3rd China (Yixing) International Refractory Raw Materials Trade Fair

• November 17-19, 2023 The 4th China International Metallurgical Materials Exposition

 

 

◆ FAQs

Q: How can we guarantee quality?

A: Always a pre-production sample before mass production; Always final inspection before shipment.

Q: Why should you buy from us instead of other suppliers?

<