examining the effects of introducing and combining

applied sciences

Article

Examining the Effects of Introducing and CombiningElectric-Arc Furnace Slag and Ceramic Waste in aSingle Self-Consolidating, High-StrengthConcrete Mix

Sayed Mohamad Soleimani *, Abdel Rahman Alaqqad, Adel Jumaah and Abdulaziz Majeed

Department of Civil Engineering, Australian College of Kuwait, P.O. Box 1411, Safat 13015, Kuwait;[email protected] (A.R.A.); [email protected] (A.J.); [email protected] (A.M.)* Correspondence: [email protected]; Tel.: +965-1828225 (ext. 4046)

Received: 12 April 2020; Accepted: 6 May 2020; Published: 15 July 2020��

Abstract: The purpose of this paper is to examine the effects of introducing waste materials sourcedfrom factories in Kuwait as partial replacements of conventional concrete materials. Rejected ceramicproducts and unused electric-arc furnace slag were treated and partially replaced portions ofcoarse and fine aggregates, and the possibility of partially replacing cement was also examined.Initial results showed that all aggregate sizes can be replaced with either of the waste materialswithout compromising the concrete’s rheological properties or compressive strength. Additionally,pulverized ceramic powder was shown to improve the compressive strength of mortar cube samples.Finally, the two waste materials were combined in hybrid mixes that aimed to have the highestutilization of waste materials while maintaining (if not improving) the properties of a previouslyestablished benchmark self-consolidating concrete (SCC) mix. The results of this study show thatwaste materials sourced from landfills in Kuwait can be repurposed to replace portions of conventionalconstruction materials in a self-consolidating, high-performance concrete mix with significantly bettermechanical properties and higher compressive strength than that shown by a benchmark mix.

Keywords: high-strength concrete; ceramic powder; ceramic aggregate; self-consolidating concrete;electric-arc furnace slag; waste materials

1. Introduction

As overall consideration for the environment gains traction in Kuwait, attention is being turnedto some local factories that generate large amounts of waste. Some of Kuwait’s significant industriesinclude structural steel production plants as well as the ceramics production industry. Stringent qualitycontrol standards during the manufacturing process and the brittle nature of final ceramic productsmean that the ceramics industry generates lots of waste [1,2]. While rejected ‘green ceramics’ canbe pulverized and reintroduced into the production cycle, rejected glazed ceramics cannot be easilyrecycled and are therefore discarded in landfills across the country. The structural steel plants inKuwait produce electric-arc furnace slag (EAFS) as opposed to blast furnace slag (BFS); this by-productis made by reducing iron ore and recycling waste steel in electric-arc furnaces, which are the standardacross the country. The generated EAFS is discarded as it has no use in Kuwait, but it is known to bedurable in its use as an aggregate in the production of pavements [3], which is due to the fact that it isharder and approximately 20% to 25% denser than BFS [4]. Standard performance concrete containingcrushed ceramic products to partially replace aggregates show similar rheological properties whencompared to a typical concrete mix [5–7]. The introduction of ceramic waste products to replace coarseand fine aggregates has been shown to improve the rheological and hardened properties of a standard

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Appl. Sci. 2020, 10, 4844 2 of 16

performance concrete [8,9]. Meanwhile, studies have shown that it is possible to use EAFS to partiallyreplace aggregates in a self-consolidating, high-performance concrete mix, but also noted that its usewould result in a reduction of slump and an increase in the viscosity of the SCC mix [10]. However,the use of EAFS has shown to increase the compressive strength, elastic modulus, and also improvesthe durability of a standard concrete mix made with conventional rounded aggregates [11]. This couldbe explained by the porosity and roughness of the surface of the EAFS aggregates compared to regularaggregates, which allows for better interaction between the cement paste and the aggregates [11,12].Self-consolidating concrete (SCC) is a subset of high-performance concrete (HPC) that has a veryhigh workability which allows it to flow considerably easier than standard performance concrete [13].This makes SCC less susceptible to segregation and can be poured on site easier than standardperformance concrete using less labor [14]. Seeing as the effects of introducing each of the additivesto either conventional or high-performance concrete mix has already been documented, the aimof this study is to examine the viability of partially replacing conventional concrete materials withlocally-sourced EAFS and repurposed ceramic products in a self-consolidating, high-performanceconcrete mix, and how it would affect its properties. The results of this would, in turn, be usedto find a suitable hybrid mix containing an optimal amount of each of the replacement materials.Introducing these local waste materials into a self-consolidating, high-performance concrete will helpminimize the amount of waste that goes to landfill in the State of Kuwait and can bring down the costof construction. Repurposing wastes generated from local industries to serve as construction materialsis one of the ways to make the construction process ‘greener’ and will aid the country in finding away forward to becoming a more sustainable community, which is in line with its desire to meet theUnited Nations Sustainable Development Goals (UN SDGs) by the year 2035, particularly SDG 11:Sustainable Cities and Communities, which is to “make cities and human settlements inclusive, safe,resilient and sustainable” [15].

2. Materials and Methods

2.1. Selection of Quality Control Tests

As stated in the Introduction, SCC is defined by its high workability as compared to conventionalconcrete. SCC is defined by having specific rheological properties, which can be verified by thefollowing ASTM and British Standard quality control tests:

2.1.1. Fresh SCC Quality Control Tests

The following quality control tests were chosen to be performed on the fresh SCC samples.Photographs of the testing procedure are shown in Figure 1.

(1) L-Box Test: This test demonstrates the SCC’s flowability through tight sections and restrictedreinforcement arrangements. For a sample of concrete to be considered SCC, the ratio H2/H1(with H2 being measured at the end of the open channel and H1 being measured at the verticalhopper) should preferably be 1.0. However, the standard allows for a minimum ratio of 0.8 [16].

(2) J-Ring Test: This test demonstrates the SCC’s flowability around reinforcements. This test alsogives an indication of its workability and exposure to segregation. SCC is defined as having anaverage slump flow diameter of at least 500 mm, which was used as a cutoff to determine whetherthe sample of concrete is SCC or not. A difference of 25 mm between the J-Ring flow and slumpflow test results is acceptable [17].

(3) V-Funnel Test: This test was used to get an idea of the SCC’s viscosity. The SCC’s viscosity wasmeasured immediately after placing it in the V-Funnel and after leaving it in the V-Funnel for5 min. The timings of the two iterations are then compared [18].

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(a)

(b) (c)

Figure 1. Photographs showing the tests performed on fresh self-consolidating concrete (SCC) samples: (a) Fresh SCC flowing through the L-Box; (b) Measuring the fresh SCC’s spread during the J-Ring test; (c) Filling the V-Funnel to measure viscosity.

2.1.2. Measurement of Compressive Strength

After the fresh concrete tests, cylindrical samples with a diameter of 100 mm and a nominal height of 200 mm were cast and cured in an insulated water tank for a period of time ranging between 3 and 56 days. A total of 224 samples spread over 16 batches were cast and tested for the purposes of this study. After curing, the hardened concrete’s compressive strength was tested using appropriately sized steel caps lined with neoprene pads (for when the strength of the concrete is less than 80 MPa) [19], and using sulfur capping (for when the strength of the concrete is more than or equal to 80 MPa) [20]. Photographs of the testing procedure are shown in Figure 2.

Figure 1. Photographs showing the tests performed on fresh self-consolidating concrete (SCC) samples:(a) Fresh SCC flowing through the L-Box; (b) Measuring the fresh SCC’s spread during the J-Ring test;(c) Filling the V-Funnel to measure viscosity.

2.1.2. Measurement of Compressive Strength

After the fresh concrete tests, cylindrical samples with a diameter of 100 mm and a nominal heightof 200 mm were cast and cured in an insulated water tank for a period of time ranging between 3 and56 days. A total of 224 samples spread over 16 batches were cast and tested for the purposes of thisstudy. After curing, the hardened concrete’s compressive strength was tested using appropriately sizedsteel caps lined with neoprene pads (for when the strength of the concrete is less than 80 MPa) [19],and using sulfur capping (for when the strength of the concrete is more than or equal to 80 MPa) [20].Photographs of the testing procedure are shown in Figure 2.

Appl. Sci. 2020, 10, 4844 4 of 16Appl. Sci. 2020, 10, x FOR PEER REVIEW 4 of 16

(a)

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Figure 2. Photographs showing the tests performed on hardened SCC samples: (a) Tested SCC samples; (b) Sample being tested for its compressive strength; (c) Sulfur-capped samples ready to be tested.

2.2. Use of Ceramic Waste

A local sanitary wares production facility provided the waste glazed ceramics used in this study. The ceramics were used to prepare three replacement products: ceramic waste coarse aggregate (CWCA) to partially replace 4.75 mm aggregates, ceramic waste fine aggregate (CWFA) to partially replace sand, as well as ceramic waste powder (CWP) to partially replace cement. Large pieces of ceramics were spun in a Los Angeles (LA) Abrasion apparatus with 12 steel balls for repetitions of 1000 revolutions. The resulting product was sieved through a series of standard sieves with diameters ranging from 9.5 mm to 0.075 mm to obtain the replacement products. Ceramic aggregates passing the 9.5 mm sieve and retained on the 4.75 mm sieve was classified as CWCA. All ceramic aggregates passing the 4.75 mm sieve and retained on any sieve up to and including the 0.075 mm sieve was classified as CWFA. Finally, ceramic aggregates passing the 0.075 mm sieve was classified as CWP. The effect of each ceramic additive was investigated individually prior to their use in the hybrid mixes to get a clear idea of how each of the additives affected the SCC’s behavior. The physical

Figure 2. Photographs showing the tests performed on hardened SCC samples: (a) Tested SCC samples;(b) Sample being tested for its compressive strength; (c) Sulfur-capped samples ready to be tested.

2.2. Use of Ceramic Waste

A local sanitary wares production facility provided the waste glazed ceramics used in this study.The ceramics were used to prepare three replacement products: ceramic waste coarse aggregate(CWCA) to partially replace 4.75 mm aggregates, ceramic waste fine aggregate (CWFA) to partiallyreplace sand, as well as ceramic waste powder (CWP) to partially replace cement. Large pieces ofceramics were spun in a Los Angeles (LA) Abrasion apparatus with 12 steel balls for repetitions of1000 revolutions. The resulting product was sieved through a series of standard sieves with diametersranging from 9.5 mm to 0.075 mm to obtain the replacement products. Ceramic aggregates passing the9.5 mm sieve and retained on the 4.75 mm sieve was classified as CWCA. All ceramic aggregates passingthe 4.75 mm sieve and retained on any sieve up to and including the 0.075 mm sieve was classified asCWFA. Finally, ceramic aggregates passing the 0.075 mm sieve was classified as CWP. The effect ofeach ceramic additive was investigated individually prior to their use in the hybrid mixes to get a clearidea of how each of the additives affected the SCC’s behavior. The physical properties of the CWCA,

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CWFA, and CWP used in the study are shown in Table 1. The bulk densities, specific gravities, andabsorption of CWCA were obtained in accordance with ASTM C127 [21]. The absorption of CWFAand CWP were obtained in accordance with ASTM C128 [22]. The fineness of CWP was obtained inaccordance with ASTM C184 [23].

Table 1. Physical properties of ceramic additives.

Symbol Property Value

CWCA

ρ loose Bulk Density–Loose (kg/m3) 1295ρ compacted Bulk Density–Compacted (kg/m3) 1434Gs apparent Specific Gravity–Apparent 2.401

Gs SSD Specific Gravity–SSD 2.421Gs bulk Specific Gravity–Bulk 2.450

- Water Absorption (%wt) 0.84

CWFA


CWP

- Water Absorption (%wt) 0.08F Fineness (%) 100

2.3. Use of EAFS

A portion of the 9.5 mm aggregates used in the study were replaced with similarly sized EAFS.The EAFS was sourced from a local structural steel production facility and sieved using a standard9.5 mm sieve to obtain the aggregates. The physical properties of the EAFS used in the study are shownin Table 2. The bulk densities, specific gravities, and absorption of EAFS were obtained in accordancewith ASTM C127 [21].

Table 2. Physical properties of Self-consolidating concrete (EAFS).

Symbol Property Value

ρ loose Bulk Density–Loose (kg/m3) 1750ρ compacted Bulk Density–Compacted (kg/m3) 1902Gs apparent Specific Gravity–Apparent 3.502

Gs SSD Specific Gravity–SSD 3.550Gs bulk Specific Gravity–Bulk 3.629


2.4. Benchmark SCC Mix

The study then proceeded to determine a suitable high-strength SCC with a target compressivestrength of 90 MPa to be used as a benchmark. This would be used as a reference to documentthe effects of each of the additives on the rheological properties and compressive strength of theSCC. The conventional concrete raw materials used in this study include: Type I ordinary Portlandcement, washed and oven-dried sand, oven-dried angular aggregates with nominal sizes of 9.5 mm and4.75 mm, class F fly ash, and silica fume that complies with the requirements set out in ASTM C1240 [24].Initially, the effect of each additive was investigated separately at various doses. The results were thenanalyzed to find the optimal dose of each additive to be used in the development of the hybrid mixes.The mix design used to produce the benchmark SCC mix is shown in Table 3. The water/cement wascomputed by dividing the quantity of water by the quantity of cement shown in the table, whereas thewater/binder ratio includes all binders used in the mix (cement, silica fume, and fly ash). It is worth

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noting that the water/cement and water/binder ratios shown in the table are those obtained from themix design and are therefore theoretical.

Table 3. Mix design proportions of benchmark SCC Mix.

Material Quantity

Cement (kg/m3) 550Sand (kg/m3) 600Coarse aggregates–9.5 mm (kg/m3) 360Coarse aggregates–4.75 mm (kg/m3) 720Water (kg/m3) 169Silica fume (kg/m3) 40Fly ash (kg/m3) 60SIKA® ViscoCrete®-5070 (l) 2.2Water/cement ratio 0.26Water/binder ratio 0.32

3. Results and Discussion

3.1. Effects of Ceramic Additives

3.1.1. Rheological Properties

The average diameters for the J-Ring flow and slump flow for samples containing varying doses ofeach ceramic additive are shown in Figure 3. As shown in the figure, introducing the additives showedno adverse effects on the flowability of the mix nor does it subject it to segregation, which initiallymeans that all trials containing ceramic additives can be considered. However, ASTM C1621 [15]also states that the numerical difference between the average diameters obtained from the two testsmust not exceed 25 mm. Figure 4 shows the numerical difference between the J-Ring flow and slumpflow for each of the ceramic additives. The results of the J-Ring flow and slump flow show that theintroduction of 10% and 15% CWFA restricts the flowability of the SCC to the point where its resultsare considered unacceptable. All other doses of ceramic additives, however, met both requirements asstated in ASTM C1621 and therefore are considered successful.

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Table 3. Mix design proportions of benchmark SCC Mix.

Material Quantity Cement (kg/m3) 550 Sand (kg/m3) 600 Coarse aggregates – 9.5 mm (kg/m3) 360 Coarse aggregates – 4.75 mm (kg/m3) 720 Water (kg/m3) 169 Silica fume (kg/m3) 40 Fly ash (kg/m3) 60 SIKA® ViscoCrete®-5070 (l) 2.2 Water/cement ratio 0.26 Water/binder ratio 0.32

3. Results and Discussion

3.1. Effects of Ceramic Additives


The average diameters for the J-Ring flow and slump flow for samples containing varying doses of each ceramic additive are shown in Figure 3. As shown in the figure, introducing the additives showed no adverse effects on the flowability of the mix nor does it subject it to segregation, which initially means that all trials containing ceramic additives can be considered. However, ASTM C1621 [15] also states that the numerical difference between the average diameters obtained from the two tests must not exceed 25 mm. Figure 4 shows the numerical difference between the J-Ring flow and slump flow for each of the ceramic additives. The results of the J-Ring flow and slump flow show that the introduction of 10% and 15% CWFA restricts the flowability of the SCC to the point where its results are considered unacceptable. All other doses of ceramic additives, however, met both requirements as stated in ASTM C1621 and therefore are considered successful.

Figure 3. Results of the J-Ring flow and slump flow for SCC samples containing varying doses of ceramic waste coarse aggregate (CWCA), ceramic waste fine aggregate (CWFA), and ceramic waste powder (CWP).

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Figure 3. Results of the J-Ring flow and slump flow for SCC samples containing varying doses ofceramic waste coarse aggregate (CWCA), ceramic waste fine aggregate (CWFA), and ceramic wastepowder (CWP).

Appl. Sci. 2020, 10, 4844 7 of 16


Figure 4. Numerical difference of the J-Ring flow and slump flow for SCC samples containing varying doses of CWCA, CWFA, and CWP.

Figure 5 shows the ratio of H2/H1 for samples containing different doses of each ceramic additive. As shown in the figure, introducing the additives had no adverse effects on the flow-ability of the SCC. All samples of SCC met the requirement to have a minimum H2/H1 ratio of 0.8 as specified in BS EN 12350-10 [16]. Additionally, most samples had ideal flow-ability as their H2/H1 ratio was 1.0. This, along with the J-Ring test results, show that the introduction of ceramic additives to a benchmark SCC mix generally does not undermine its rheological properties.

Figure 5. Ratio of H2/H1 obtained from the L-Box Test results for SCC samples containing varying dosages of CWCA, CWFA, and CWP.

Figure 6 shows the time it takes for samples containing different doses of each ceramic additive to pass through a V-Funnel as stated in BS EN 12350-9 [18]. It is worth noting that the benchmark SCC mix initially had undesirable viscosity; the viscosity of the mix is not considered to be a major issue as it is not a key determinant of SCC. It can be inferred that the introduction of CWCA to partially replace 4.75 mm aggregates increases the viscosity of the benchmark SCC mix, which is shown in the figure by the increased time taken for the SCC to pass through the V-Funnel; the result for 15% CWCA replacement can be considered anomalous as it does not follow the general trend shown by the CWCA-replaced SCC. Introducing CWFA at lower and higher ranges to partially replace sand improved the benchmark SCC mix’s viscosity and made it meet the criteria for desirable

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Figure 4. Numerical difference of the J-Ring flow and slump flow for SCC samples containing varyingdoses of CWCA, CWFA, and CWP.

Figure 5 shows the ratio of H2/H1 for samples containing different doses of each ceramic additive.As shown in the figure, introducing the additives had no adverse effects on the flow-ability of the SCC.All samples of SCC met the requirement to have a minimum H2/H1 ratio of 0.8 as specified in BS EN12350-10 [16]. Additionally, most samples had ideal flow-ability as their H2/H1 ratio was 1.0. This,along with the J-Ring test results, show that the introduction of ceramic additives to a benchmark SCCmix generally does not undermine its rheological properties.


Figure 4. Numerical difference of the J-Ring flow and slump flow for SCC samples containing varying doses of CWCA, CWFA, and CWP.

Figure 5 shows the ratio of H2/H1 for samples containing different doses of each ceramic additive. As shown in the figure, introducing the additives had no adverse effects on the flow-ability of the SCC. All samples of SCC met the requirement to have a minimum H2/H1 ratio of 0.8 as specified in BS EN 12350-10 [16]. Additionally, most samples had ideal flow-ability as their H2/H1 ratio was 1.0. This, along with the J-Ring test results, show that the introduction of ceramic additives to a benchmark SCC mix generally does not undermine its rheological properties.

Figure 5. Ratio of H2/H1 obtained from the L-Box Test results for SCC samples containing varying dosages of CWCA, CWFA, and CWP.

Figure 6 shows the time it takes for samples containing different doses of each ceramic additive to pass through a V-Funnel as stated in BS EN 12350-9 [18]. It is worth noting that the benchmark SCC mix initially had undesirable viscosity; the viscosity of the mix is not considered to be a major issue as it is not a key determinant of SCC. It can be inferred that the introduction of CWCA to partially replace 4.75 mm aggregates increases the viscosity of the benchmark SCC mix, which is shown in the figure by the increased time taken for the SCC to pass through the V-Funnel; the result for 15% CWCA replacement can be considered anomalous as it does not follow the general trend shown by the CWCA-replaced SCC. Introducing CWFA at lower and higher ranges to partially replace sand improved the benchmark SCC mix’s viscosity and made it meet the criteria for desirable

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Figure 5. Ratio of H2/H1 obtained from the L-Box Test results for SCC samples containing varyingdosages of CWCA, CWFA, and CWP.

Figure 6 shows the time it takes for samples containing different doses of each ceramic additive topass through a V-Funnel as stated in BS EN 12350-9 [18]. It is worth noting that the benchmark SCCmix initially had undesirable viscosity; the viscosity of the mix is not considered to be a major issueas it is not a key determinant of SCC. It can be inferred that the introduction of CWCA to partiallyreplace 4.75 mm aggregates increases the viscosity of the benchmark SCC mix, which is shown inthe figure by the increased time taken for the SCC to pass through the V-Funnel; the result for 15%CWCA replacement can be considered anomalous as it does not follow the general trend shown bythe CWCA-replaced SCC. Introducing CWFA at lower and higher ranges to partially replace sandimproved the benchmark SCC mix’s viscosity and made it meet the criteria for desirable workability

Appl. Sci. 2020, 10, 4844 8 of 16

as per the standard. Finally, the introduction of CWP to the mix significantly improved the viscosity ofthe benchmark SCC mix, making them fall well beneath the cut-off set by the standard.


workability as per the standard. Finally, the introduction of CWP to the mix significantly improved the viscosity of the benchmark SCC mix, making them fall well beneath the cut-off set by the standard.

Figure 6. The time taken for SCC samples containing varying doses of CWCA, CWFA, and CWP to pass through a V-Funnel.

3.1.2. Compressive Strength

Figures 7–9 show the variation of compressive strength of SCC samples containing various ceramic additives with time. Multiple samples were tested at different intervals ranging between 3 and 56 days, with the average compressive strength being reported.

Figure 7 shows how the compressive strength of SCC samples containing various doses of CWCA varied with curing age. As shown in the figure, introducing CWCA at low doses (5% and 10%) had a negative impact on the compressive strength at 3 days compared to the benchmark SCC mix. By examining the slope of the trendline for 5% CWCA, we see that the SCC continued to gain strength at a consistent rate up until the 21-day mark, after which the rate of strength gain plateaued with no significant strength gain up to the 56-day mark. All other trials exhibited similar rates of strength gain compared to the benchmark SCC mix. All trials had similar 56-day compressive strengths, ranging between 92–95 MPa, noting that the benchmark SCC mix had a 56-day compressive strength of 92.1 MPa. For the benchmark mix, the compressive strength results had a maximum standard deviation of 2.82 MPa and had a maximum variance coefficient of 3.13%, whereas the CWCA mixes had a maximum standard deviation of 6.70 MPa and a maximum variance coefficient of 7.41%.

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Figure 6. The time taken for SCC samples containing varying doses of CWCA, CWFA, and CWP topass through a V-Funnel.


Figures 7–9 show the variation of compressive strength of SCC samples containing various ceramicadditives with time. Multiple samples were tested at different intervals ranging between 3 and 56 days,with the average compressive strength being reported.


Figure 7. Compressive strength variation of samples containing various doses of CWCA.

Figure 8 shows the variation of compressive strength of SCC samples containing various doses of CWFA. As shown in the figure, introducing CWFA at any dose initially improved the compressive strength measured at 3 days, when compared to the benchmark SCC mix. By examining the slope of the trendline for 20% CWFA, we see that the SCC gained strength at a much faster rate as compared to the benchmark SCC mix. The same mix gained most of its compressive strength by the 14-day mark, after which the rate of strength gain plateaued with no significant strength gain up to the 56-day mark. All other trials exhibited similar rates of strength gain compared to the benchmark SCC mix. All trials had similar 56-day compressive strengths, ranging between 92–96 MPa. The CWFA mixes had a maximum standard deviation of 4.32 MPa and a maximum variance coefficient of 4.92%.

The compressive strength of SCC samples containing various doses of CWP is shown in Figure 9. As shown in the figure, introducing CWP at any dose initially had a negative effect on the compressive strength measured at 3 days, when compared to the benchmark SCC mix. 5% CWP began to match the benchmark SCC’s performance at 14 days, while 10% CWP matched the benchmark SCC at 28 days. Both trials had similar 56-day compressive strengths, ranging between 90–92 MPa. The CWP mixes had a maximum standard deviation of 2.72 MPa and a maximum variance coefficient of 2.99%.

Figure 8. Compressive strength variation of samples containing various doses of CWFA.

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Figure 8 shows the variation of compressive strength of SCC samples containing various doses of CWFA. As shown in the figure, introducing CWFA at any dose initially improved the compressive strength measured at 3 days, when compared to the benchmark SCC mix. By examining the slope of the trendline for 20% CWFA, we see that the SCC gained strength at a much faster rate as compared to the benchmark SCC mix. The same mix gained most of its compressive strength by the 14-day mark, after which the rate of strength gain plateaued with no significant strength gain up to the 56-day mark. All other trials exhibited similar rates of strength gain compared to the benchmark SCC mix. All trials had similar 56-day compressive strengths, ranging between 92–96 MPa. The CWFA mixes had a maximum standard deviation of 4.32 MPa and a maximum variance coefficient of 4.92%.

The compressive strength of SCC samples containing various doses of CWP is shown in Figure 9. As shown in the figure, introducing CWP at any dose initially had a negative effect on the compressive strength measured at 3 days, when compared to the benchmark SCC mix. 5% CWP began to match the benchmark SCC’s performance at 14 days, while 10% CWP matched the benchmark SCC at 28 days. Both trials had similar 56-day compressive strengths, ranging between 90–92 MPa. The CWP mixes had a maximum standard deviation of 2.72 MPa and a maximum variance coefficient of 2.99%.


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Appl. Sci. 2020, 10, 4844 9 of 16


Figure 9. Compressive strength variation of samples containing various doses of CWP.

Following the results of the CWP trials, an additional investigation was launched to see whether CWP could be used as a viable replacement of cement. Twelve mortar cubes measuring 50 × 50 × 50 mm were cast in accordance with ASTM C109 [25]. Three cubes were cast as a control sample that contained no CWP, with the remainder divided into three cubes with increments of 10% CWP. Figure 10 shows the variation of the compressive strength of these hydraulic cement cubes when tested at 7 days of age. As shown in the figure, introducing CWP at any dose increased the compressive strength of the mortar cubes when compared to the plain mortar cubes, with 20% CWP exhibiting the largest compressive strength (31.2 MPa). The results of this test show that CWP is a viable replacement of cement in the preparation of mortar cubes, and that the compressive strength of the SCC mix can be improved if introduced at an appropriate dose.

Figure 10. Variation of compressive strength of hydraulic cement for samples containing various dosages of CWP compared to a plain mortar mix.

3.2. Effects of EAFS


The average diameters for the J-Ring flow and slump flow for samples containing varying doses of EAFS are shown in Figure 11. As shown in the figure, introducing EAFS showed no adverse effects on the flow-ability of the SCC, which means that it will not be subject to any significant segregation.

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Figure 7 shows how the compressive strength of SCC samples containing various doses of CWCAvaried with curing age. As shown in the figure, introducing CWCA at low doses (5% and 10%)had a negative impact on the compressive strength at 3 days compared to the benchmark SCC mix.By examining the slope of the trendline for 5% CWCA, we see that the SCC continued to gain strengthat a consistent rate up until the 21-day mark, after which the rate of strength gain plateaued with nosignificant strength gain up to the 56-day mark. All other trials exhibited similar rates of strengthgain compared to the benchmark SCC mix. All trials had similar 56-day compressive strengths,ranging between 92–95 MPa, noting that the benchmark SCC mix had a 56-day compressive strengthof 92.1 MPa. For the benchmark mix, the compressive strength results had a maximum standarddeviation of 2.82 MPa and had a maximum variance coefficient of 3.13%, whereas the CWCA mixeshad a maximum standard deviation of 6.70 MPa and a maximum variance coefficient of 7.41%.

Figure 8 shows the variation of compressive strength of SCC samples containing various doses ofCWFA. As shown in the figure, introducing CWFA at any dose initially improved the compressivestrength measured at 3 days, when compared to the benchmark SCC mix. By examining the slope ofthe trendline for 20% CWFA, we see that the SCC gained strength at a much faster rate as comparedto the benchmark SCC mix. The same mix gained most of its compressive strength by the 14-daymark, after which the rate of strength gain plateaued with no significant strength gain up to the 56-daymark. All other trials exhibited similar rates of strength gain compared to the benchmark SCC mix.All trials had similar 56-day compressive strengths, ranging between 92–96 MPa. The CWFA mixeshad a maximum standard deviation of 4.32 MPa and a maximum variance coefficient of 4.92%.

The compressive strength of SCC samples containing various doses of CWP is shown in Figure 9.As shown in the figure, introducing CWP at any dose initially had a negative effect on the compressivestrength measured at 3 days, when compared to the benchmark SCC mix. 5% CWP began to match thebenchmark SCC’s performance at 14 days, while 10% CWP matched the benchmark SCC at 28 days.Both trials had similar 56-day compressive strengths, ranging between 90–92 MPa. The CWP mixeshad a maximum standard deviation of 2.72 MPa and a maximum variance coefficient of 2.99%.

Following the results of the CWP trials, an additional investigation was launched to see whetherCWP could be used as a viable replacement of cement. Twelve mortar cubes measuring 50 × 50 × 50 mmwere cast in accordance with ASTM C109 [25]. Three cubes were cast as a control sample that containedno CWP, with the remainder divided into three cubes with increments of 10% CWP. Figure 10 showsthe variation of the compressive strength of these hydraulic cement cubes when tested at 7 days of age.As shown in the figure, introducing CWP at any dose increased the compressive strength of the mortarcubes when compared to the plain mortar cubes, with 20% CWP exhibiting the largest compressive

Appl. Sci. 2020, 10, 4844 10 of 16

strength (31.2 MPa). The results of this test show that CWP is a viable replacement of cement in thepreparation of mortar cubes, and that the compressive strength of the SCC mix can be improved ifintroduced at an appropriate dose.



Following the results of the CWP trials, an additional investigation was launched to see whether CWP could be used as a viable replacement of cement. Twelve mortar cubes measuring 50 × 50 × 50 mm were cast in accordance with ASTM C109 [25]. Three cubes were cast as a control sample that contained no CWP, with the remainder divided into three cubes with increments of 10% CWP. Figure 10 shows the variation of the compressive strength of these hydraulic cement cubes when tested at 7 days of age. As shown in the figure, introducing CWP at any dose increased the compressive strength of the mortar cubes when compared to the plain mortar cubes, with 20% CWP exhibiting the largest compressive strength (31.2 MPa). The results of this test show that CWP is a viable replacement of cement in the preparation of mortar cubes, and that the compressive strength of the SCC mix can be improved if introduced at an appropriate dose.

Figure 10. Variation of compressive strength of hydraulic cement for samples containing various dosages of CWP compared to a plain mortar mix.



The average diameters for the J-Ring flow and slump flow for samples containing varying doses of EAFS are shown in Figure 11. As shown in the figure, introducing EAFS showed no adverse effects on the flow-ability of the SCC, which means that it will not be subject to any significant segregation.

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Figure 10. Variation of compressive strength of hydraulic cement for samples containing variousdosages of CWP compared to a plain mortar mix.



The average diameters for the J-Ring flow and slump flow for samples containing varying dosesof EAFS are shown in Figure 11. As shown in the figure, introducing EAFS showed no adverse effectson the flow-ability of the SCC, which means that it will not be subject to any significant segregation.All trials containing EAFS can be considered. Figure 12 shows the numerical difference between theJ-Ring flow and slump flow for each of the trials. All doses of EAFS met both requirements of averagediameter and numerical difference as stated in ASTM C1621 and are therefore considered successful.


All trials containing EAFS can be considered. Figure 12 shows the numerical difference between the J-Ring flow and slump flow for each of the trials. All doses of EAFS met both requirements of average diameter and numerical difference as stated in ASTM C1621 and are therefore considered successful.

Figure 11. Results of the J-Ring flow and slump flow for SCC samples containing varying doses of EAFS.

Figure 12. Numerical difference of the J-Ring flow and slump flow for SCC samples containing varying doses of EAFS.

Introducing EAFS had no effect on the flow-ability of the SCC. All samples of SCC had ideal flow-ability as their H2/H1 ratio was 1.0. This, along with the J-Ring test results, show that introducing EAFS to a benchmark SCC mix at these doses does not undermine its rheological properties.

Figure 13 shows the time it takes for samples containing different doses of EAFS to pass through a V-Funnel. It is clear that adding EAFS to a benchmark SCC mix significantly decreases its viscosity. A small dose of EAFS reduced the time required to clear the V-Funnel to 1 s, compared to 15 s for the benchmark SCC mix. All doses up to and including 15% EAFS were at or under the maximum desirable time stated in BS EN 12350-9 [18]. The results from this test shows a strong correlation between the EAFS content in a sample of SCC and its viscosity. The results of the 5, 10, and 15% replacements stand at odds with the findings of another study, which stated that the incorporation of EAFS would significantly increase the viscosity of the SCC mix [10].

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Appl. Sci. 2020, 10, 4844 11 of 16


All trials containing EAFS can be considered. Figure 12 shows the numerical difference between the J-Ring flow and slump flow for each of the trials. All doses of EAFS met both requirements of average diameter and numerical difference as stated in ASTM C1621 and are therefore considered successful.


Figure 12. Numerical difference of the J-Ring flow and slump flow for SCC samples containing varying doses of EAFS.

Introducing EAFS had no effect on the flow-ability of the SCC. All samples of SCC had ideal flow-ability as their H2/H1 ratio was 1.0. This, along with the J-Ring test results, show that introducing EAFS to a benchmark SCC mix at these doses does not undermine its rheological properties.

Figure 13 shows the time it takes for samples containing different doses of EAFS to pass through a V-Funnel. It is clear that adding EAFS to a benchmark SCC mix significantly decreases its viscosity. A small dose of EAFS reduced the time required to clear the V-Funnel to 1 s, compared to 15 s for the benchmark SCC mix. All doses up to and including 15% EAFS were at or under the maximum desirable time stated in BS EN 12350-9 [18]. The results from this test shows a strong correlation between the EAFS content in a sample of SCC and its viscosity. The results of the 5, 10, and 15% replacements stand at odds with the findings of another study, which stated that the incorporation of EAFS would significantly increase the viscosity of the SCC mix [10].

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Figure 12. Numerical difference of the J-Ring flow and slump flow for SCC samples containing varyingdoses of EAFS.

Introducing EAFS had no effect on the flow-ability of the SCC. All samples of SCC had idealflow-ability as their H2/H1 ratio was 1.0. This, along with the J-Ring test results, show that introducingEAFS to a benchmark SCC mix at these doses does not undermine its rheological properties.

Figure 13 shows the time it takes for samples containing different doses of EAFS to pass through aV-Funnel. It is clear that adding EAFS to a benchmark SCC mix significantly decreases its viscosity.A small dose of EAFS reduced the time required to clear the V-Funnel to 1 s, compared to 15 s forthe benchmark SCC mix. All doses up to and including 15% EAFS were at or under the maximumdesirable time stated in BS EN 12350-9 [18]. The results from this test shows a strong correlationbetween the EAFS content in a sample of SCC and its viscosity. The results of the 5, 10, and 15%replacements stand at odds with the findings of another study, which stated that the incorporation ofEAFS would significantly increase the viscosity of the SCC mix [10].Appl. Sci. 2020, 10, x FOR PEER REVIEW 12 of 16

Figure 13. The time taken for SCC samples containing varying doses of EAFS to pass through a V-Funnel.


The following figures show the variation of compressive strength of SCC samples containing EAFS with time. Multiple samples were tested at different intervals ranging between 3 and 56 days, with the average compressive strength being reported.

Figure 14 shows how the compressive strength of SCC samples containing various doses of EAFS varies with curing age. As shown in the figure, the introduction of EAFS at low doses (5% and 10%) into the benchmark SCC mix improves the compressive strength of the SCC at any age, and increased its 56-day compressive strength considerably from 92.1 MPa to 104.7 MPa and 98.2 MPa, respectively. The introduction of EAFS at higher doses (15% and 20%) showed almost identical compressive strength results to each other with minor variations; both doses initially had a slower strength gain rate compared to the benchmark SCC mix. The EAFS mixes had a maximum standard deviation of 2.70 MPa and a maximum variance coefficient of 2.75%.

Figure 14. Variation of compressive strength for samples containing various dosages of EAFS compared to the benchmark SCC mix.

3.3. Development of Hybrid Mixes

With the results of each individual additive at hand, hybrid SCC mixes using optimum doses of CWCA, CWFA, CWP, and EAFS were developed. In total, three hybrid mixes were put forward and

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Appl. Sci. 2020, 10, 4844 12 of 16


The following figures show the variation of compressive strength of SCC samples containingEAFS with time. Multiple samples were tested at different intervals ranging between 3 and 56 days,with the average compressive strength being reported.

Figure 14 shows how the compressive strength of SCC samples containing various doses of EAFSvaries with curing age. As shown in the figure, the introduction of EAFS at low doses (5% and 10%)into the benchmark SCC mix improves the compressive strength of the SCC at any age, and increasedits 56-day compressive strength considerably from 92.1 MPa to 104.7 MPa and 98.2 MPa, respectively.The introduction of EAFS at higher doses (15% and 20%) showed almost identical compressive strengthresults to each other with minor variations; both doses initially had a slower strength gain ratecompared to the benchmark SCC mix. The EAFS mixes had a maximum standard deviation of 2.70 MPaand a maximum variance coefficient of 2.75%.




The following figures show the variation of compressive strength of SCC samples containing EAFS with time. Multiple samples were tested at different intervals ranging between 3 and 56 days, with the average compressive strength being reported.

Figure 14 shows how the compressive strength of SCC samples containing various doses of EAFS varies with curing age. As shown in the figure, the introduction of EAFS at low doses (5% and 10%) into the benchmark SCC mix improves the compressive strength of the SCC at any age, and increased its 56-day compressive strength considerably from 92.1 MPa to 104.7 MPa and 98.2 MPa, respectively. The introduction of EAFS at higher doses (15% and 20%) showed almost identical compressive strength results to each other with minor variations; both doses initially had a slower strength gain rate compared to the benchmark SCC mix. The EAFS mixes had a maximum standard deviation of 2.70 MPa and a maximum variance coefficient of 2.75%.

Figure 14. Variation of compressive strength for samples containing various dosages of EAFS compared to the benchmark SCC mix.


With the results of each individual additive at hand, hybrid SCC mixes using optimum doses of CWCA, CWFA, CWP, and EAFS were developed. In total, three hybrid mixes were put forward and

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Figure 14. Variation of compressive strength for samples containing various dosages of EAFS comparedto the benchmark SCC mix.


With the results of each individual additive at hand, hybrid SCC mixes using optimum dosesof CWCA, CWFA, CWP, and EAFS were developed. In total, three hybrid mixes were put forwardand tested for their rheological properties as well as their compressive strength. The testing matrixshowing the content of the hybrid mixes is shown in Table 4.

Table 4. Testing matrix for the hybrid mixes used in the study.

Replacement Material * Hybrid mix 1 (H01) Hybrid mix 2 (H02) Hybrid mix 3 (H03)

CWCA (replacing 4.75 mm CA) 0 10 0CWFA (replacing sand) 10 0 0CWP (replacing cement) 0 0 5EAFS (replacing 9.5 mm CA) 5 10 5

* Values cited are the percentage replacement of conventional concrete materials shown in parentheses.


Figure 15 shows the average diameter for the J-Ring flow and slump flow for the hybrid mixes.As shown in the figure, all hybrid mixes had the minimum diameter to be initially considered SCC.Figure 16 shows the numerical difference between the J-Ring flow and slump flow for each trial.All hybrid mixes met both requirements of average diameter and numerical difference as stated inASTM C162.

Appl. Sci. 2020, 10, 4844 13 of 16


tested for their rheological properties as well as their compressive strength. The testing matrix showing the content of the hybrid mixes is shown in Table 4.


Replacement material * Hybrid mix 1 (H01) Hybrid mix 2 (H02) Hybrid mix 3 (H03) CWCA (replacing 4.75 mm CA) 0 10 0 CWFA (replacing sand) 10 0 0 CWP (replacing cement) 0 0 5 EAFS (replacing 9.5 mm CA) 5 10 5



Figure 15 shows the average diameter for the J-Ring flow and slump flow for the hybrid mixes. As shown in the figure, all hybrid mixes had the minimum diameter to be initially considered SCC. Figure 16 shows the numerical difference between the J-Ring flow and slump flow for each trial. All hybrid mixes met both requirements of average diameter and numerical difference as stated in ASTM C162.

Figure 15. Results of the J-Ring flow and slump flow for hybrid SCC samples.

Figure 16. Numerical difference of the J-Ring flow and slump flow for hybrid SCC samples.

The hybrid mixes had no effect on the flow-ability of the SCC. All samples of SCC had ideal flow-ability as their H2/H1 ratio was 1.0. This, along with the J-Ring test results, show that the

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tested for their rheological properties as well as their compressive strength. The testing matrix showing the content of the hybrid mixes is shown in Table 4.


Replacement material * Hybrid mix 1 (H01) Hybrid mix 2 (H02) Hybrid mix 3 (H03) CWCA (replacing 4.75 mm CA) 0 10 0 CWFA (replacing sand) 10 0 0 CWP (replacing cement) 0 0 5 EAFS (replacing 9.5 mm CA) 5 10 5



Figure 15 shows the average diameter for the J-Ring flow and slump flow for the hybrid mixes. As shown in the figure, all hybrid mixes had the minimum diameter to be initially considered SCC. Figure 16 shows the numerical difference between the J-Ring flow and slump flow for each trial. All hybrid mixes met both requirements of average diameter and numerical difference as stated in ASTM C162.



The hybrid mixes had no effect on the flow-ability of the SCC. All samples of SCC had ideal flow-ability as their H2/H1 ratio was 1.0. This, along with the J-Ring test results, show that the

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The hybrid mixes had no effect on the flow-ability of the SCC. All samples of SCC had idealflow-ability as their H2/H1 ratio was 1.0. This, along with the J-Ring test results, show that thehybridization of the benchmark mix in all hybrid mixes was done correctly, as the benchmark SCC’sfresh properties were not compromised.

Figure 17 shows the time it takes for the hybrid SCC samples to pass through a V-Funnel. It isclear that all hybrid mixes reduced the viscosity of the SCC, which is shown in the significant drop intime required to clear the V-Funnel. H02 had the best results (6 s) whereas H01 and H03 had similarresults (8 s). All hybrid samples showed desirable viscosity.


hybridization of the benchmark mix in all hybrid mixes was done correctly, as the benchmark SCC’s fresh properties were not compromised.

Figure 17 shows the time it takes for the hybrid SCC samples to pass through a V-Funnel. It is clear that all hybrid mixes reduced the viscosity of the SCC, which is shown in the significant drop in time required to clear the V-Funnel. H02 had the best results (6 s) whereas H01 and H03 had similar results (8 s). All hybrid samples showed desirable viscosity.

Figure 17. The time taken for hybrid SCC samples to pass through a V-Funnel.


The variation of the hybrid SCC samples’ compressive strength with curing age is shown in Figure 18. Multiple samples were tested at different intervals ranging between 3 and 56 days, with the average compressive strength being reported. At 3 and 7 days of curing, the hybrid mixes had a lower compressive strength compared to the benchmark SCC mix. Afterwards, H01 began to overtake the benchmark SCC mix and continued to do so until 56 days. Meanwhile, H02 and H03 exhibited similar trends (compressive strength and rate of strength gain) to each other. H02 met the benchmark SCC mix’s final compressive strength while H01 and H03 exceeded it, with the final compressive strengths being 95.6, 92.1, and 94.7 MPa for H01, H02, and H03, respectively. The hybrid mixes had a maximum standard deviation of 4.20 MPa and a maximum variance coefficient of 5.25%.

Figure 18. Compressive strength variation of hybrid SCC samples.

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Appl. Sci. 2020, 10, 4844 14 of 16


The variation of the hybrid SCC samples’ compressive strength with curing age is shown inFigure 18. Multiple samples were tested at different intervals ranging between 3 and 56 days, with theaverage compressive strength being reported. At 3 and 7 days of curing, the hybrid mixes had a lowercompressive strength compared to the benchmark SCC mix. Afterwards, H01 began to overtake thebenchmark SCC mix and continued to do so until 56 days. Meanwhile, H02 and H03 exhibited similartrends (compressive strength and rate of strength gain) to each other. H02 met the benchmark SCCmix’s final compressive strength while H01 and H03 exceeded it, with the final compressive strengthsbeing 95.6, 92.1, and 94.7 MPa for H01, H02, and H03, respectively. The hybrid mixes had a maximumstandard deviation of 4.20 MPa and a maximum variance coefficient of 5.25%.


hybridization of the benchmark mix in all hybrid mixes was done correctly, as the benchmark SCC’s fresh properties were not compromised.

Figure 17 shows the time it takes for the hybrid SCC samples to pass through a V-Funnel. It is clear that all hybrid mixes reduced the viscosity of the SCC, which is shown in the significant drop in time required to clear the V-Funnel. H02 had the best results (6 s) whereas H01 and H03 had similar results (8 s). All hybrid samples showed desirable viscosity.



The variation of the hybrid SCC samples’ compressive strength with curing age is shown in Figure 18. Multiple samples were tested at different intervals ranging between 3 and 56 days, with the average compressive strength being reported. At 3 and 7 days of curing, the hybrid mixes had a lower compressive strength compared to the benchmark SCC mix. Afterwards, H01 began to overtake the benchmark SCC mix and continued to do so until 56 days. Meanwhile, H02 and H03 exhibited similar trends (compressive strength and rate of strength gain) to each other. H02 met the benchmark SCC mix’s final compressive strength while H01 and H03 exceeded it, with the final compressive strengths being 95.6, 92.1, and 94.7 MPa for H01, H02, and H03, respectively. The hybrid mixes had a maximum standard deviation of 4.20 MPa and a maximum variance coefficient of 5.25%.


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4. Conclusions

Upon close examination of the results of this study, it is clear that waste materials from Kuwaitcan be repurposed to yield viable construction materials that can replace conventional constructionmaterials to produce high-strength SCC concrete. CWCA was found to be a viable replacement of4.75 mm used in a benchmark SCC concrete, though its introduction may have subjected the SCC to aslight increase in risk of segregation and viscosity. CWFA used at either a high (20%) or low (5%) dosewas shown to greatly improve the SCC’s viscosity to make it more desirable. The CWP investigationswere useful, showing that its introduction had no negative impact on the SCC’s rheological properties.However, it was found that CWP’s introduction at low doses (5% and 10%) can negatively impactthe SCC’s compressive strength but its introduction at higher doses (20% and 30%) as a replacementof cement in mortar cubes shows that it can match and exceed the control sample, indicating itsfeasibility as a sustainable cement replacement. Introducing EAFS to a benchmark SCC mix at thedoses put forward in this study had no adverse effects on its rheological properties or its compressivestrength whatsoever. The findings for SCC with EAFS stand in disagreement with the outcomes ofprevious studies. Based on these results, three hybrid mixes were devised using optimum doses ofeach replacement material, and it was shown that a high-strength SCC concrete can be produced usingthese waste materials as a partial replacement of conventional materials that can at least match abenchmark SCC concrete mix’s properties, if not improve them.

Author Contributions: Conceptualization, S.M.S.; methodology, S.M.S., A.R.A., A.J. and A.M.; formal analysis,S.M.S., and A.R.A.; investigation, A.J. and A.M.; resources, S.M.S. and A.R.A.; writing—original draft preparation,A.R.A.; writing—review and editing, A.R.A. and S.M.S.; supervision, S.M.S.; project administration, A.R.A.;funding acquisition, S.M.S. All authors have read and agreed to the published version of the manuscript.

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Funding: This project was funded “partially” by Kuwait Foundation for the Advancement of Sciences underproject code: PN18-15EV-01.

Acknowledgments: The authors would like to acknowledge Tahir Afrasiab, Ali Behbehani, Najem Al-Matroud,and Sarah Al-Muhanna for their contributions and hard work and dedication while preparing the concrete mixesfor this study. The authors would also like to express their gratitude to United Steel Industrial Company forproviding their waste electric-arc furnace slag and to Gulf Shores Company for Sanitary Wares and ConstructionBuilding Materials for providing their waste glazed ceramics for use in this project. The authors are grateful toCombined Group Contracting Co. for providing the team with the concrete materials and to Sika for providingthe team with the superplasticizer used in the study.

Conflicts of Interest: The authors declare no conflict of interest.

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examining the effects of introducing and combining

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