Life cycle assessment of steel fibre-reinforced concrete beams

Figures & data

Figure 1. Carbon dioxide emissions from the cement and steel industry in 2019 (IEA, 2019).

Figure 2. Phases of a life cycle assessment. Adapted from ISO 14040 (2006b) and ISO 14044 (2006c).

Figure 3. LCA modules of construction products adapted from EN 15804 (2019).

Figure 4. Defining SFRC material properties for beam modelling.

Table 1. Properties of modelled RC beams.

s/n	Beam ID	Span (m)	Breadth, b (m)	Depth, h (m)	Compressive strength (MPa)
1	RC30-4-50	4	0.23	0.37	30
2	RC30-5-50	5	0.23	0.37	30
3	RC30-6-50	6	0.25	0.42	30
4	RC30-4-100	4	0.25	0.37	30
5	RC30-5-100	5	0.25	0.37	30
6	RC30-6-100	6	0.25	0.45	30
7	RC30-4-150	4	0.275	0.4	30
8	RC30-5-150	5	0.275	0.4	30
9	RC30-6-150	6	0.275	0.45	30
10	RC30-4-200	4	0.28	0.43	30
11	RC30-5-200	5	0.28	0.43	30
12	RC30-6-200	6	0.3	0.47	30
13	RC40-4-50	4	0.23	0.37	40
14	RC40-5-50	5	0.23	0.37	40
15	RC40-6-50	6	0.25	0.42	40
16	RC40-4-100	4	0.25	0.37	40
17	RC40-5-100	5	0.25	0.37	40
18	RC40-6-100	6	0.25	0.45	40
19	RC40-4-150	4	0.275	0.4	40
20	RC40-5-150	5	0.275	0.4	40
21	RC40-6-150	6	0.275	0.45	40
22	RC40-4-200	4	0.28	0.43	40
23	RC40-5-200	5	0.28	0.43	40
24	RC40-6-200	6	0.3	0.47	40
25	RC50-4-50	4	0.23	0.35	50
26	RC50-5-50	5	0.23	0.35	50
27	RC50-6-50	6	0.24	0.4	50
28	RC50-4-100	4	0.25	0.37	50
29	RC50-5-100	5	0.25	0.37	50
30	RC50-6-100	6	0.25	0.42	50
31	RC50-4-150	4	0.275	0.4	50
32	RC50-5-150	5	0.275	0.4	50
33	RC50-6-150	6	0.275	0.45	50
34	RC50-4-200	4	0.28	0.43	50
35	RC50-5-200	5	0.28	0.43	50
36	RC50-6-200	6	0.3	0.47	50

Table 2. Properties of modelled SFRC beams.

s/n	Beam ID	Span	Breadth, b (m)	Depth, h (m)	Compressive strength (MPa)
1	SFRC30-4-50	4	0.15	0.25	30
2	SFRC30-5-50	5	0.15	0.26	30
3	SFRC30-6-50	6	0.15	0.3	30
4	SFRC30-4-100	4	0.2	0.31	30
5	SFRC30-5-100	5	0.2	0.34	30
6	SFRC30-6-100	6	0.2	0.345	30
7	SFRC30-4-150	4	0.24	0.36	30
8	SFRC30-5-150	5	0.24	0.36	30
9	SFRC30-6-150	6	0.25	0.4	30
10	SFRC30-4-200	4	0.26	0.38	30
11	SFRC30-5-200	5	0.26	0.38	30
12	SFRC30-6-200	6	0.3	0.44	30
13	SFRC40-4-50	4	0.15	0.25	40
14	SFRC40-5-50	5	0.15	0.26	40
15	SFRC40-6-50	6	0.15	0.3	40
16	SFRC40-4-100	4	0.2	0.31	40
17	SFRC40-5-100	5	0.2	0.34	40
18	SFRC40-6-100	6	0.2	0.345	40
19	SFRC40-4-150	4	0.24	0.36	40
20	SFRC40-5-150	5	0.24	0.36	40
21	SFRC40-6-150	6	0.25	0.4	40
22	SFRC40-4-200	4	0.26	0.38	40
23	SFRC40-5-200	5	0.26	0.38	40
24	SFRC40-6-200	6	0.3	0.44	40
25	SFRC50-4-50	4	0.15	0.25	50
26	SFRC50-5-50	5	0.15	0.25	50
27	SFRC50-6-50	6	0.15	0.3	50
28	SFRC50-4-100	4	0.2	0.31	50
29	SFRC50-5-100	5	0.2	0.33	50
30	SFRC50-6-100	6	0.2	0.34	50
31	SFRC50-4-150	4	0.24	0.34	50
32	SFRC50-5-150	5	0.24	0.34	50
33	SFRC50-6-150	6	0.25	0.36	50
34	SFRC50-4-200	4	0.26	0.37	50
35	SFRC50-5-200	5	0.26	0.37	50
36	SFRC50-6-200	6	0.3	0.42	50

Table 3. Properties of traditional concrete.

Description	C30/37	C40/50	C50/60
Elastic (E) modulus	3.28 × 10^4 MPa	3.52 × 10^4 MPa	3.73 × 10^4 MPa
Shear (G) modulus	1.37 × 10^4 MPa	1.47 × 10^4 MPa	1.55 × 10^4 MPa
Mean tensile strength at 28 days	2.9 MPa	3.5 MPa	4.1 MPa
Density	2500 kg/m^3	2500 kg/m^3	2500 kg/m^3

Table 4. Properties of steel fibre-reinforced concrete.

Description	C30/37-5D65/60BG	C40/50-5D65/60BG	C50/60-5D65/60BG
E modulus	3.28 × 10^4 MPa	3.52 × 10^4 MPa	3.73 × 10^4 MPa
G modulus	1.37 × 10^4 MPa	1.47 × 10^4 MPa	1.55 × 10^4 MPa
Characteristic Basic residual tensile strength with 20–40 kg/m^3 fibres dosage (fcto,u)	0.7–1.10 MPa	0.77–1.25 MPa	0.84–1.38 MPa
Density	2500 kg/m^3	2500 kg/m^3	2500 kg/m^3

Table 5. Properties of steel bars (B500 C).

Description	Result
Characteristic yield strength	500 MPa
Bar surface	Ribbed
G modulus	8.33 × 10^4 MPa
Minimum stress ratio	1.15–1.35
Minimum elongation at maximum load	7.5%

Figure 5. The geometry of 5D steel fibres. Adapted from Abdallah et al. (2016).

Table 6. Mechanical and geometric Properties of steel fibres (DRAMIX 5D).

Description	Result
Length	60 mm
Diameter	0.9 mm
Aspect ratio	65
E modulus	210 GPa
Tensile strength	2300 MPa
Wire ductility	6%
Hook length, L1	2.57 mm
Hook length, L2	2.38 mm
Hook length, L3	2.57 mm
Hook length, L4	2.56 mm
Hook angle, ϴ1	27.9 °
Hook angle, ϴ2	28.2
Hook height, H1	2.96 mm
Hook height, H2	1.57 mm

Figure 6. Stress-strain distribution block in the cross-section. Adapted from Dlouhý and Pouillon (2019).

Figure 7. Minimum C/D to compressive strength of concrete (García-Taengua et al., 2014).

Figure 8. Displacement of simply supported RC beam under a loading condition in SCIA engineer.

Figure 9. Displacement of SFRC beams under a given loading condition in SCIA engineer.

Figure 10. Shear force analysis of SFRC beam in SCIA engineer.

Figure 11. LCA system boundary for conventionally reinforced concrete.

Figure 12. LCA system boundary for steel fibre-reinforced concrete.

Table 7. Life cycle inventory data summary.

Data Type	Data source	Geography
Reinforced concrete
Cement production	ICE	United Kingdom (UK)
Fine and coarse aggregate production	ICE	UK
Steel rebar production	Speciality Steel UK Limited (T/A Liberty Speciality Steels) EPD	UK
Steel fibres production	Bekaert Dramix steel fibres EPD	Europe
Transportation
Road	Greenhouse gas reporting: conversion factors 2022	UK
Construction activities
Site equipment operations	Greenhouse gas reporting: conversion factors 2022	UK
Workforce inputs	Authors calculation	Global

Table 8. Embodied carbon of construction materials.

Material	Embodied carbon (kgCO2e/ kg)	Source
Cement	0.832	Jones (2019)
Water	0.000149	BEIS (2022)
Aggregates	0.00438	Jones (2019)
Superplasticizer	1.88	Jones (2019)
Steel rebar	1.18	Speciality Steel (2021)
Steel fibres	1.59	Bekaert (2021)

Table 9. Base mix proportion for 30 MPa, 40 MPa and 50 MPa grade concrete.

	Compressive strength
Material	30 MPa	40 MPa	50 MPa
Cement, kg/m^3	330	400	450
Water, kg/m^3	140	140	140
Fine aggregates, kg/m^3	750	700	660
Coarse aggregates, kg/m^3	1245	1230	1230
Superplasticiser, kg/m^3	3.3	4.0	4.5

Table 10. End-of-life scenario for the various elements.

Element	Recovery rate	Source
Concrete	100%	Authors assumption
Steel rebar	92%	Jones (2019) and Speciality Steel (2021)
Steel fibre	86%	Bekaert (2021)

Table 11. WLEC of RC and SFRC beams.

fck (MPa)	Mres (kN.m/m)	Span (m)	Embodied carbon, RC beam (kgCO2e/kN.m/m)	Embodied carbon, SFRC beam (kgCO2e/kN.m/m)
30	50	4	0.618	0.321
		6	0.618	0.298
		8	0.701	0.292
	100	4	0.364	0.261
		6	0.364	0.239
		8	0.361	0.243
	150	4	0.315	0.236
		6	0.313	0.236
		8	0.323	0.239
	200	4	0.270	0.214
		6	0.270	0.214
		8	0.291	0.231
40	50	4	0.671	0.334
		6	0.671	0.314
		8	0.842	0.313
	100	4	0.390	0.253
		6	0.390	0.255
		8	0.466	0.315
	150	4	0.343	0.250
		6	0.343	0.250
		8	0.366	0.273
	200	4	0.281	0.226
		6	0.281	0.226
		8	0.323	0.275
50	50	4	0.735	0.350
		6	0.735	0.337
		8	0.821	0.335
	100	4	0.406	0.290
		6	0.406	0.299
		8	0.460	0.315
	150	4	0.367	0.264
		6	0.367	0.264
		8	0.398	0.300
	200	4	0.296	0.240
		6	0.296	0.240
		8	0.344	0.301

Figure 13. Embodied carbon of 4 m span RC and SFRC beams.

Figure 14. Embodied carbon of 6 m span RC and SFRC beams.

Figure 15. Embodied carbon of 8 m span RC and SFRC beams.

Figure 16. Area of steel provided in the tension zone of 30 MPa RC and SFRC beams.

Figure 17. Area of steel provided in the tension zone of 40 MPa RC and SFRC beams.

Figure 18. Area of steel provided in the tension zone of 50 MPa RC and SFRC beams.

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Data availability statement

The data that support the findings of this study are available upon reasonable request. All inquiries regarding the data used for this study should be directed to the corresponding author, Gideon Osei Asare.