Physical and Mechanical Characteristics of Sustainable Concrete Comprising Industrial Waste Materials as a Replacement of Conventional Aggregate

Abstract

In a sustainable approach, it is essential to reduce waste materials for improving the urban environmental performance leads to development in the livable, sustainable, and greener city. In pursuit of this goal, iron lathe waste was used in this study as a replacement of fine aggregate to produce sustainable concrete. Iron lathe waste is generally a waste material from the lathe machine, which is abundantly available to an extent. These waste materials may lead to environmental and health concerns. Therefore, the main goal of this study is to experimentally examine the physio-mechanical characteristics of sustainable concrete incorporating lathe iron waste. The lathe iron waste dusts (LIWD) were used as a partial replacement of fine aggregate in different levels by weight (5%, 10%, 15%, and 20%) to fabricate the sustainable concrete. The mechanical and physical properties of sustainable concrete were investigated by conducting tests, such as workability, ultrasonic pulse velocity, compressive strength, splitting tensile strength, and flexural strength to investigate the properties of the alternative concrete comparing with that of conventional concrete. The experimental results showed that the LIWD significantly enhanced the tensile, flexural, and compressive strength of the concrete up to 13%, 19%, and 38%, respectively. Therefore, LIWD can potentially improve the serviceability of the structural elements.

1. Introduction

Sustainability is a major concern due to rapid development in the past few decades. The construction industry significantly impacts infrastructure development in any region. Concrete has been utilized as an elementary material in any development [1]. The production of concrete generates huge pollutions and makes an intensive amount of CO₂, which is the decline in natural resources and the most evident impacts on greenhouse emissions. Therefore, it is rational to use industrial waste materials to produce sustainable concrete [2].

Hence, the most important are the steel industries, with their various forms and supporting industries, which have negative environmental impacts represented by the waste of their production. Where this waste may be dumped into the barren land and other disposal places. Dumping of these wastes into the barren soil contaminates the soil and ground water, which in turn creates an unhealthy environment [3]. To reduce these effects and to develop specialized concrete many efforts are being in this field. Attempts are being made by worldwide researchers to effectively enhance the performance of concrete by using resorting to making use of these wastes, recycling them and using them as inputs for many other industries, especially in the concrete industry, as these wastes have good advantages that can lead to improving some of the physical and mechanical properties of the produced concrete [4]. In fact, concrete being weak in tension and fails in brittle manner when applied with flexure and tension forces [5]. Hence, to improve the tension characteristics of concrete and reduce the negative effects of steel wastes that resulted from steel-producing industries, many researchers around the world have tended to recycle these wastes and use them as industrial inputs [6,7]. This may achieve by using multiple methods, such as using them as admixtures with certain proportions of concrete weight, or as partial replacement by certain weight percentages of sand or aggregate [8].

For example, Rahman et al. [9] concluded that adding 1% by weight of waste steel scraps to concrete has a noticeable effect on concrete properties, as the compressive strength value increased by 60% and the tensile strength increased by 37% over its value for ordinary concrete at the age of 28 days. Darji et al. [10] utilized steel scrap up to 2.4% by weight, at a gap of 0.2%, and they observed that the compressive strength of concrete increased by adding steel scrap up to 1.4%. They also concluded that adding more percentage of steel scrap (more than 1.4%) causes slight reduction in compressive strength, but strength is still more than plain cement concrete. Also, Shrivasatava et al. [11] found reusing 0.5–2% steel scrap content in concrete, that compressive strength slightly increased by 3%, and tensile strength increased up to 20% as considerable increases, while the flexural strength effectively increased nearly 40% as compared to plain cement concrete. The experimental results revealed that steel scrap aid to improve the shrinkage reduction, cracking resistance (i.e., preventing crack propagation with increasing modulus of elasticity), but in contrast, the workability of fresh concrete restricted to less scrap contents. Mello et al. [12] have studied the concrete properties with the addition of cellulose, steel, carbon, and PET fibers. Each fiber was added at 4% to the fresh concrete, which was moist cured for 28 days and then tested for compressive, flexural, and tensile strengths. Results showed that improvement in strength after addition of steel and carbon fibers. In addition, Gawatre et al. [13] have mixed the lathe waste in three proportions, i.e., 0.5%, 1%, and 2%. The results show that the compressive strength increased by 16.4% while tensile strength increased by 25.3% due to addition of 2% waste lathe as compared to plain cement concrete. Vijayakumar et al. [14] concluded in their research that the addition of lathe scrap in concrete increased the performance of beams in flexural by 40% as compared to plain concrete. There is only considerable increase in split tensile strength of concrete with lathe scarp as compared with plain concrete. The result showed that addition of lathe scraps into plain concrete mixtures enhanced its compressive strength while it decreased the workability of fresh concrete. The impact strength of concrete mixed with lathe scrap showed an increase as compared with plain concrete. Ashok et al. [15] have made comparison between conventional concrete and concrete replacing cement with steel scrap fibers (SSFRC) (i.e., 0.5%, 1%, 1.5%, 2%). Compressive strength, tensile strength, and flexural strength of SSFRC is found to be the maximum for volume fraction of 1.5% steel scrap fiber.

In other hand, Girskas and Nagrockienė [16] partially replaced fine aggregate with steel cord scrap of 1.5%, 3.0%, and 4.5% by weight. They predicted that the substitution of fine aggregate with steel cord scrap resulted in lower water absorption and higher compressive strength in the concrete specimens. The porosity parameters have also changed: the closed porosity has increased and consequently the freeze–thaw resistance of concrete has improved. In addition, Mandloi and Pathak [17] presented a research of utilization of lathe steel waste as partial replacement of natural coarse aggregate with 5% (by weight). Also, for the increment in strength of concrete, they use wire mesh while casting in the form of 10 mm³ cubes. The outcomes found that highest value of compressive strength is obtained for cubes with 5% replacement of aggregates with lathe steel waste and with wire mesh higher than the normal concrete.

Due to urbanization and sustainable development—in addition to concrete possessing low tensile strength—there is a steady trend towards the industry of concrete with high compressive and tensile strength with low cost. To do so, iron waste was used as an input in the concrete industry, either using it as admixtures to concrete in certain proportions, or as a partial replacement of cement, sand, or aggregates. In this context, the main aim of this paper is to use iron waste in the concrete to develop a sustainable and greener construction industry, as many local workshops and lathes provide abundant low-cost lathe iron waste.

2. Experimental Program

2.1. Materials

2.1.1. Cement

Type I ordinary Portland cement (OPC I) supplied by Najran cement was used in this study. The Blaine Fineness of the cement is 410 m²/kg, and the specific gravity is 3.15. The Bogue phases of the cement was 59% C3S (Tricalcium silicate), 12.1% C2S (Dicalcium silicate), 10.6% C3A (Tricalcium aluminate), and 10.4% C4AF (Tetracalcium aluminoferrite) as provided by the manufacturer. The oxides of the cement are listed in

Table 1. Chemical composition of cement.

Items	SiO2	Al2O3	Fe2O3	CaO	SO3	MgO	K2O	Insoluble	LOI
wt.%	19.73	6.2	3.44	63.78	2.23	0.96	1.02	0.93	1.51

.

2.1.2. Lathe Iron Waste Dusts (LIWD)

The lathe iron waste dusts (LIWD) was collected from industrial lathe workshops which normally generated from steel cutting treatments. A sample of the waste iron utilized in this study is shown in Figure 1a. The XRD test of the sample reflects the dominance of silica and iron oxides as shown in Figure 1b. The physical properties of the waste iron are presented in

Table 2. Materials properties.

Material	Fineness Modulus	Specific Gravity	Absorption (%)	Bulk Density (kg/m3)
Coarse aggregate	7.34	2.77	0.69	1630.00
Fine aggregate	2.23	2.67	1.31	1535.74
LIWD	2.33	5.56	-	1783.00

.

2.1.3. Aggregates

The fine aggregate was natural sand with a maximum size of 4.75 mm and the coarser aggregate was a natural crushed stone with a maximum size of 20 mm used for casting the concrete samples which comply with ASTM C33/C33M-18 [18]. The physical properties of the aggregates are presented in Table 2.

2.1.4. Water

The potable tap water was used as a constituent of conventional and sustainable concrete mixtures and curing of concrete. The properties of the water were fulfilled with ASTM C1602/C1602M requirement [19].

2.2. Mixing Regime

AL-KO (tecnotest) Mixer (4-ft3 capacity) was used for mixing concrete formulations. The constituents were mixed in dry state for 1–2 min followed by adding mixing water into the bowl of the dry mixture. The total approximate mixing time was 2 min for all concrete formulations. To ensure that the mixtures in the desired workability, slump test was conducted for each. Following ASTM C511 procedure, specimens of seven 100 mm cubes; 100 mm diameter and 200 mm height cylinders; and a prism of 100 × 100 × 500 mm were cast for testing compressive, split, and flexural strength respectively for each concrete mixture.

2.3. Samples Preparations

Concrete samples were prepared according to ASTM C192M [20] using a standard mixer with a water-to-cement ratio of 0.50. No Supplementary Materials or chemical admixtures were used in this study. The iron waste was used as a partial mass replacement of fine aggregate (sand) as 5%, 10%, 15%, and 20%. The mix proportions of concrete are listed in

Table 3. Mix proportions of concrete.

% Waste Iron	Quantity (kg/m3)
	Cement	Water	Fine Aggregate	Coarse Aggregate	Waste Iron
0%	399.20	210.38	863.16	868.00	0.00
5%			820.01		43.16
10%			776.85		86.32
15%			733.69		129.47
20%			690.53		172.63

Note: Aggregates are in saturated surface dry condition.

. After the mixing, concrete was cast into several molds (cubes, cylinders, and prisms) for 24 h and then demolded and submerged in clean potable tap water for curing. The concrete samples were cured for 7, 14, and 28 days at room temperature.

2.4. Test Samples

The compressive, split tensile, and flexural strength tests were respectively carried out as per ASTM C39/C39M [21], ASTM C496/C496M [22], and ASTM C78/C78M [23]. The compressive strength test was done on 100 × 100 × 100 mm³ cube specimens, while split test was carried out on 100 mm diameter, 200 mm height, and flexural strength of 100 × 100 × 500 mm³-prism specimens while represents 7, 14, and 28 days curing age, the average of three specimens for each.

In order to know the homogeneity and integrity of the structure of produced LIWD concrete, ultrasonic pulse velocity (UPV) tests were conducted according to ASTM C597 [24]. The cube specimens were weighed in water immediately after getting them out from the water basin, in the saturated surface dry state, and in the dry state for calculating the densities of the samples.

3. Results and Discussions

3.1. Slump Test

Figure 2 shows the slump values for mixtures containing different percentages of lathe waste steel as a partial replacement of fine aggregate. It is perceived that the slump values are linearly decreasing with the increasing replacement of fine aggregate in the concrete. The correlation between the slump and iron waste as a partial replacement of fine aggregate is revealed in Figure 3. It is emphasized that the slump decreasing with the coefficient of correlation of 0.9489. The outcomes indicate that the slump decreases of about 2.6%, 5.3%, 10.8%, and 20.3%, respectively compared with the reference sample. The slump reduced might be due to the heterogeneity and roughness of the iron waste particles that could reduce the fluidity of the mixtures.

3.2. Densities of the Speecimen

The dry densities of the concrete containing 5%, 10%, 15%, and 20% of waste steel as a partial replacement of fine aggregate over curing periods of 7, 14, and 28 days are exhibited in Figure 4. The concrete containing iron waste demonstrated that higher dense concrete with respect to the reference sample. The curves revealed that dry densities linearly increase with increasing the iron waste. For 28-day curing, the dry densities for samples containing 5%, 10%, 15%, and 20% of iron waste increases about 1.0%, 2.5%, 3.8%, and 5.0%, respectively, compared to the reference sample as exposed in Figure 5. There was also a slight increase in the dry densities has been observed due to the curing time increases. The increase in the dry densities for the concrete is due to the fact that the specific gravity of iron waste is 1.80 times greater than the specific gravity of fine aggregate. Other researchers exhibited that the dry density of concrete increased by the steel slag as a fine aggregate into the concrete [25,26].

3.3. Compressive Strength

Figure 6 presents the compressive strength over curing period of 7, 14, and 28 days for concrete containing 5%, 10%, 15%, and 20% of iron waste as a partial replacement of fine aggregate. The curves showed that the compressive strength of the concrete comprising iron waste increases with increasing percentage of iron waste for all curing period of concrete. This might be due to the higher compressive strength and density of lathe iron waste. For 14-day curing period, a slight reduction of compressive strength was observed for higher percentage of iron waste (15% and 20%) compared to other mixtures, which might be due to the accumulation of iron waste on cement particles, leading to retardation hydration of the cement. At 28-day curing period, the trend of increasing the compressive strength greater at the higher percentage of iron waste (15% and 20%) was attained compared with the other mixtures. This waste might be attributed to the availability of water into the matrix for longer period of time and which helped for accelerating the hydration process of cement within the matrix and thus strength development enhanced with higher volume of iron waste.

The compressive strength and its enhancement at 28 days of curing period are revealed in Figure 7. The concrete enclosing iron waste 5% to 20% enhanced the compressive strength 4.75% to 38% respectively, compared with the reference sample. Whereas the compressive strength of concrete increased up to 21% by the use of steel slag as an aggregate [27].

3.4. Flexural Strength

The flexural strength of concrete and its enhancement by containing 5%, 10%, 15%, and 20% LIWD at 28-days curing period are presented in Figure 8. The gradual replacement of fine aggregate with iron waste from 0% to 20% enhanced the flexural strength up to 19% compared with the reference sample. Because the iron waste might resist or delay the occurring initial cracks in the tension face of the sample during the load applying moment by its higher load bearing capability. Hence, the iron waste comprising sustainable concrete significantly enhanced the flexural strength of the sample. Therefore, the flexural strength is about 5-times higher than the splitting tensile strength which is much better than the conventional concrete. Since the conventional concrete the flexural strength is about 1–2.5 times the higher than the splitting tensile strength [28].

3.5. Splitting Tensile Strength

The splitting tensile strength characteristics of iron waste containing sustainable concrete are revealed in Figure 9. Maximum enhancement of tensile strength of about 11% compared to the reference sample which was suppressed by 20% of iron waste as a fine aggregate replacement. This might be appeared due to the roughness of the iron waste surface. Whereas the waste materials from electrical furnace such as steel slag containing concrete slightly increased the splitting tensile strength due to the higher specific gravity of the slag [29].

3.6. Load-Displacement Characteristics

The experimental set-up is exhibited in Figure 10 for capturing the load-displacement data from the Universal Instron machine. The relationship between the applied load and displacement characteristics at mid-span of the prism samples are shown in Figure 11. The load-displacement behaviors of the samples are compared with the reference sample, which is comprised of 0% lathe iron waste dust. The curves were exposed gradually to linear behavior up to the ultimate strength of the samples. However, the displacement significantly reduced with 5%, 10%, 15%, and 20% LIWD in the samples due to the enhanced stiffness by the LIWD. This behaves also controlled the cracks in the samples during the application of the loads on the samples. Therefore, the LIWD samples load-displacement curves were steeper compared with the reference sample. These characteristics of the samples can be attributed to the serviceability requirement of the structural members since iron waste improved the cracking behavior and reduce the displacement [30,31].

3.7. Ultrasonic Pulse Velocity (UPV)

UPV test is a non-destructive test method that is led to determine the consistency and quality of concrete. UPV also specifies the pores and cracks in the concrete [32]. The relationship between the UPV and LIWD percentage is presented in Figure 12. The concrete having the UPV values from 3.66 km/s to 4.58 km/s is considered a good concrete [33]. The concrete within the above-mentioned limit is ensured that no bulky voids or cracks can decrease the structural integrity. The curves have exhibited the trend of enhancing in the UPV with the escalating age of concrete and percentage of LIWD. It could be enhanced the bonding into the concrete ingredients. That might be improved the strength of concrete by decreasing the voids and ensure dense concrete. The rate of increase in the UPV has revealed a higher trend due to a higher rate of hydration. Therefore, it is also essential to remark that the increase in the LIWD percentage in the concrete caused enhanced UPV values.

4. Conclusions

The influence of replacement of fine aggregate in the conventional concrete by industrial iron waste as a construction material was investigated for developing the sustainable concrete. The different percentages (0%, 5%, 10%, 15%, and 20%) of iron waste were utilized for manufactured sustainable concrete. The characteristics were investigated include slump, dry density, compressive strength, flexural strength, splitting tensile strength, load-displacement behavior, and UPV. The following conclusions can be drawn based on the experimental investigation:

• The replacement of fine aggregate with iron waste demonstrated significant influence on the compressive strength of concrete. The enhancement of compressive strength with the substitute of 5%, 10%, 15%, and 20% fine aggregate in sustainable concrete of iron waste expressed 5%, 13%, 31%, and 38%, respectively higher than the reference sample. However, the slump values were reduced up to 20.3% due to the heterogeneity and roughness of the iron waste.
• The dry density of the iron waste based sustainable concrete was increased up to 5% compared to the reference sample. Because of the higher unit weight of iron waste compared with the fine aggregate.
• The flexural strength significantly enhanced of 8%, 8%, 13%, and 19% compared with the reference sample by the replacement of fine aggregate of 5%, 10%, 15%, and 20%, respectively. This might be achieved by the iron waste particles delay the initiation of cracks into the concrete compared with the reference sample.
• The splitting tensile strength potentially increased up to 13% compared with the reference sample due to the roughness of the iron waste surface. Since this roughness of the surface make better interlocking between the aggregates.
• The displacement significantly reduced by 5%, 10%, 15%, and 20% comprising lathe iron waste in the samples which ensure the serviceability requirement might be achieved by this waste materials into the concrete.
• The iron waste meaningfully enhanced stiffness in the concrete samples due to higher density of the iron waste.
• The increment of iron waste in the concrete mixes were exhibited the improvement in UPV compared with the reference sample. The UPV improved due to the voids reduced by the iron waste and ensure dense concrete.
• Therefore, the lathe iron waste can be used as a construction material to produce sustainable concrete and to ensure a greener environment.