The Effect of the Waste of Materials and Carbon Nanotube on the Concrete Incorporated with Steel Fibers

Steel fiber, waste material, Carbon Nanotube, concrete, advanced application The addition of agricultural and industrial solid wastes and nanomaterials to concrete combined with steel fibers to improve the mechanical and electrical properties of concrete was investigated. This approach could be used in advanced applications in electromagnetic shielding and conductive concrete. Steel fibers were used at 2%wt. of sand and (induction furnace slag (EIF), carbon nanotube (CNT), steel wool fibers, prepared corn husks) at 0.5 and 1 wt.%. of cement. Obtained results of using 1% for both carbon nanotube and steel wool with steel fibers in the mixture 4 and 6, respectively, showed the highest rates of compressive strength. A similar result was shown when tested at 3,7 and 28 days of age and compressive strength was 47.4MPa,47.34MPa for the mixture 4 and 6 respectively. The electrical conductivity and electrical resistance of the samples were measured at the age of 7 days. The findings have also shown that adding steel wool as well as( CNT) gave the best results and the sample containing the furnace slag achieved satisfactory results as well. How to cite this article: M. H. Saleem, F.M. Othman, and A. A. Hamead, “The Effect of the Waste of Materials and Carbon Nanotube on the Concrete Incorporated with Steel Fibers,” Engineering and Technology Journal, Vol. 39, No. 06, pp. 956-964, 2021. DOI: https://doi.org/10.30684/etj.v39i6.2018

Steel fiber, waste material, Carbon Nanotube, concrete, advanced application The addition of agricultural and industrial solid wastes and nanomaterials to concrete combined with steel fibers to improve the mechanical and electrical properties of concrete was investigated. This approach could be used in advanced applications in electromagnetic shielding and conductive concrete. Steel fibers were used at 2%wt. of sand and (induction furnace slag (EIF), carbon nanotube (CNT), steel wool fibers, prepared corn husks) at 0.5 and 1 wt.%. of cement. Obtained results of using 1% for both carbon nanotube and steel wool with steel fibers in the mixture 4 and 6, respectively, showed the highest rates of compressive strength. A similar result was shown when tested at 3,7 and 28 days of age and compressive strength was 47.4MPa,47.34MPa for the mixture 4 and 6 respectively. The electrical conductivity and electrical resistance of the samples were measured at the age of 7 days. The findings have also shown that adding steel wool as well as( CNT) gave the best results and the sample containing the furnace slag achieved satisfactory results as well.

INTRODUCTION
The study of concrete incorporated with steel fibers has been investigated from the side of physical, mechanical, and electrical properties as well as electromagnetic interference (EMI) in electrical noise. It creates a disturbance or an unwanted response in electrical circuits and devices and this helps in their use in the military protection of some installations from the impulses resulting from the explosions for example. ] 1  The current work aims to make use of industrial and agricultural waste by preparing slag powder and corn husk ash and using it as a partial substitute for cement, as well as studying its effect on concrete incorporated with steel fibers by studying the physical and mechanical properties, resistance and electrical conductivity properties.

I. Materials
Induction furnace slag was used from the State Company for Steel Industries in Baghdad. Visible impurities were removed, crushed, and grinding to obtain a fine slag powder to be used as a partial substitute for cement in this study Figure1. Cornhusk was used in this study by immersing it in water for 3 days and then drying it for two days After that, it was burned at a temperature of 500 °C ]15[, then milled for 15 minutes Figure 2 and used as a partial substitute for cement. SEM for slag and prepared corn husk as shown in Figure 3. Ordinary Portland cement (OPC) (kubasuh cement plant in Iraq) was used. The sand was passed from a 0.085 sieve to remove all impurities that might reduce the quality of the concrete. The maximum size of coarse aggregate is 14 mm. Steel fiber from SAPEN INTERNATIONAL CO., LTD was used as a partial substitute for sand. Table І shows the physical properties of these fibers. Carbon nanotube (CNT) from Sky Spring Nanomaterials, Inc. used as a partial substitute for cement in this study Table П shows the physical properties of Multiwall nanotube. Steel wool or shredded steel fibers are used in brake linings, cleaning, automobile exhaust pipes, metal separating, etc., Table Ш shows the properties of steel wool.

II. Concrete Mixture Proportioning
A concrete mixing ratio of 1:1.5:3 was used and 9mixtures were designed in this study, as shown in Table ІV, the percentage of steel fiber is 2% of the weight of sand, the ratio of EIF slag, CNT, steel wool, and corn husk was 0.5 and 1% of the weight of cement. The concrete was poured into molds of 10×10×10 cm dimensions]2[ According to British specifications BS EN 12390 -3 [16], and the concrete components were manually weighed and then mixed in the electric concrete mixer. The concrete cubes were removed after 24 h from the molds, kept underwater for curing, and tested After 3,7,28 days.

III. Inspection and Test
1.) The compressive strength test with device specifications, capacity: 3000KN, was performed for 3, 7, and 28 days.
2.) The electrical conductivity was measured by a precision impedance analyzer (brand Agilent, model 4294A made in USA), OSC level was (500 mv). Samples were prepared in the form of discs with dimensions of diameter (3.5cm) and thickness (0.5 cm) with the same replacement ratios for steel fiber 2% of the weight of sand and for each of the EIF slag and CNT, corn husks and steel wool 1% of the cement weight. The DC conductivity(σ ) was calculated using the Eq.(1) [12] σ = 1/ρ =L/RA (1) Where ρ is the electrical resistivity, R is electrical resistance, L is the distance between the two electrodes, A is the cross-sectional area of the electrical contact.
3.) Scanning Electron Microscope (SEM), This test analyzes the microstructure and morphology of the prepared samples examined at the Nanotechnology Research Center at the University of Technology using TESCAN Vega II. 4.) The density of samples was tested at an age of 3, 7, 28 days, samples were in the form of a circular disk with a diameter of 1 cm and a thickness of 0.5 cm, It is possible to calculate the density through the following Eq.
Where w1: Dry weight of sample in gm, W2: Average weight of wet sample in gm. W3: submerge weight of the sample in gm ρw: The density of water which is equivalent to 1 g/cm3.

I. Compressive strength
The presence of steel fibers enhanced the strength and compressive strength of concrete]20[, and the rates of improvement varied according to the additives used in this research (slag, CNT, steel wool, corn husks). Figure 4 shows the results of the compressive strength of the prepared concrete samples, the results were much better compared to Ali Toghroli et. al ]3[ and Tareq S. Al-Attar et. al ] 18[. The figure shows the improvement of all mixtures compared to the control sample at all ages 3, 7, 28 days, And the additives with the highest percentage, which is 1% of the weight of cement, showed a greater improvement than using it by 0.5% Concrete mixture M4 and M6 showed the best results when tested at 28 days of age, and the rate of improvement compared to the control sample was 41.6% for mixture No. 4 containing 1% CNT and 41, 4% for mixture 6 containing 1% steel wool. Also, compressive strength improved, With a percentage of 20, 9% when slag add by 1% in mixture 2 and for mixture 8 contain 1% corn husk at 18%.

II. Electrical conductivity results
The electrical conductivity is affected by the additions of the conductive materials as well as the presence of the pores in the concrete mixture. The distribution and mixing of the materials in a homogeneous manner has a great effect as well as the conductivity is affected by the temperature and humidity ]9[. Figure5 shows the results of the electrical resistance as well as the electrical conductivity of the prepared samples, and it is evident from the figure that the mixture that contains steel fibers with steel wool, he showed improved results in an approach to the mixture containing steel fibers with (CNT), and these were the best results compared to the control mixture, and  Figure 6 shows SEM images of prepared mixtures, Samples were examined at 7 days old. The results showed that the addition of (slag, carbon nanotube, steel wool, and corn husk ash) led to a change in the concrete's microstructure. The presence of these additives in the mixture gave a relatively thicker consistency. Figure 6-a shows the well and homogeneous distribution of furnace slag in the concrete mixture. Figure 6-b, Several Nano filaments have been distinguished because the nanotube are homogeneous and the concrete mixture is well known and the widespread MWCNT can be distinguished. This may be responsible for the good mechanical and electrical properties of the mixture. Figure 6-c shows that the cut steel wool fibers with steel fibers in the concrete mixture can form fiber groups and thus the conductive channels appear along with them Figure 6-d. Cornhusk ash with steel fibers in the concrete mixture is shown and a clear network helps give good properties to this mixture.   -with 1%slag, b-with1%CNT, c-with 1%steel wool, d-with 1%corn ash).

IV. Dry density
Figure7 shows the dry density of the samples prepared at ages 3, 7, and 28 days. The figure shows that the density increases for all mixtures compared to the control sample, but it is higher at the greater substitution rate of cement. mixtures containing 1% by weight for all additives (slag, Carbon nanotube, steel wool, corn husks), but the rates of increase differ because of the difference in the density of the materials used, and it seems that these additives acted as fillers]22[, which improved properties and increased density]17[.

CONCLUSIONS
The concrete reinforced with steel fibers of 6 cm length was studied with the use of agricultural and industrial wastes and carbon nanotube within the prepared mixtures, compression resistance, density, and electrical properties were studied.
Conclusions can be drawn from this study: 1.) It is possible to benefit from agricultural and industrial wastes such as corn husks prepared in this research and induction furnaces slag in concrete mixtures and this contributes to preserving the environment through the disposal of these wastes and their reuse, as well as the use of these materials, contributes to reducing the cost.
2.) Concrete containing Nanocarbon and steel fibers showed results of a comparable approach compared to The sample, which contains steel wool and steel fibers, achieved excellent results in the compressive strength test and the conductivity and electrical resistance test for both mixtures, and it scored 47, 4 MPa, and 47.34MPa, respectively, and the electrical conductivity was reached 0.056 S/m and 0.057 S/m.
3.) Concrete can be developed, improved mechanical, electrical, electromagnetic, and physical properties for use in advanced applications in conductive concrete and electromagnetic shielding.