Evaluation of flexural toughness of polyurethane concrete incorporating various steel fiber length and content

Figures & data

Table 1. Physical and chemical properties of isocyanate.

Number	Type	Test results	Appearance
1	Viscosity at 25 ℃ (mPa•s)	250
2	NCO content of isocyanate (%)	32.0
3	Density at 25 ℃ (g/cm3)	1.22
4	Acidity (%)	0.030
5	Hydrolyzed chlorine (%)	0.20

Table 2. Physical and chemical properties of combined polyether polyol.

Number	Type	Test results	Appearance
1	Viscosity at 25 ℃ (mPa•s)	200
2	Hydroxyl value (mg KOH/g)	370
3	Density at 25 ℃ (g/cm3)	1.13
4	PH	5.4
5	Unsaturation (mmol/g)	0.005

Table 3. Physical and mechanical properties of cement.

Number	Type		Test results
1	Setting time (min)	Initial setting time	72
		Final setting time	366
2	Fineness (%)		1.8
3	Specific surface area (m^2/kg)		374
4	28d shrinkage rate (%)		0.08
5	Wear resistance (kg/m^2)		2.4
6	Flexural strength (MPa)	3 days	4.6
		28 days	7.2
7	Compressive strength (MPa)	3 days	24.6
		28 days	43.5

Table 4. Physical and mechanical properties of granite aggregate.

Number	Length (mm)	Diameter (mm)	Length-diameter ratio	Density (t/m^3)	Elastic modulus (GPa)	Appearance
1	30	0.75	40	7.8	210
2	40	0.75	53
3	50	0.75	66
4	60	0.75	80

Table 5. Polyurethane concrete mixture (by mass).

Isocyanate	Polyether polyol	Aggregate	Cement	Molecular sieve
1	1	10	2.3	0.3

Table 6. Physical and mechanical properties of polyurethane concrete.

Density (g/cm^3)	Shore hardness (HD)	Slump (mm)	Compressive strength (MPa)	Splitting tensile strength (MPa)	Modulus of elasticity (GPa)
2.119	85.5	10	83.03	8.29	.3833

Table 7. Test plan for steel fiber polyurethane concrete.

Number	Specimen ID	Steel fiber length (mm)	Steel fiber content (%)
1	SFPUC-0	/	/
2	SFPUC-H30-1.0%	30	1%
3	SFPUC-H40-1.0%	40	1%
4	SFPUC-H50-1.0%	50	1%
5	SFPUC-H60-1.0%	60	1%
6	SFPUC-H50-.5%	50	0.5%
7	SFPUC-H50-1.5%	50	1.5%
8	SFPUC-H50-2.0%	50	2%

Figure 1. Diagram of polyurethane concrete preparation.

Figure 2. Definitions of flexural toughness parameters.

Figure 3. Test results of compressive strength of steel fiber polyurethane concrete.

Figure 4. The typical cross-sectional distribution of steel fibers.

Table 8. The bending test results of the test beam.

Number	Specimen ID	Peak load (kN)	Deflection of peak load (mm)	Ultimate deflection (mm)	Number of fibers in cross-section	Number of steel fiber fracture	Fracture ratio
1	SFPUC-0	186.1	0.085	0.085	/	/	/
2	SFPUC-H30-1.0%	235.8	0.311	4.981	38	31	81.6%
3	SFPUC-H40-1.0%	228.1	0.261	4.571	34	27	79.4%
4	SFPUC-H50-1.0%	223.4	0.227	4.374	31	23	74.2%
5	SFPUC-H60-1.0%	215.4	0.183	4.289	26	18	69.2%
6	SFPUC-H50-.5%	193.5	0.165	4.001	19	15	73.7%
7	SFPUC-H50-1.5%	272.2	0.287	4.563	36	27	75.0%
8	SFPUC-H50-2.0%	288.4	0.332	4.999	50	38	76.0%

Figure 5. Peak load and deflection of peak load.

Figure 6. Typical load-deflection curves for polyurethane concrete beam specimens incorporating 1.0% of various fiber lengths.

Figure 7. Peak load and deflection of peak load.

Figure 8. Typical load-deflection curves for polyurethane concrete beam specimens of various fiber content.

Figure 9. Microstructure of failure form of steel fiber in matrix (a: steel fiber pull-out, b: steel fiber fracture, c: end bonding failure of steel fiber).

Figure 10. Flexural toughness ratio for polyurethane concrete beam specimens incorporating 1.0% of various fiber lengths.

Figure 11. Flexural toughness ratio for polyurethane concrete beam specimens with different content of steel fiber.

Table 9. Flexural toughness index variability of polyurethane concrete with different steel fiber lengths.

Specimen ID		SFPUC-H30-1.0%	SFPUC-H40-1.0%	SFPUC-H50-1.0%	SFPUC-H60-1.0%
Re,P	Values	0.73	0.75	0.75	0.75
	Variation rate（%）	/	2.74	2.74	2.74
Re,500	Values	0.81	0.78	0.72	0.73
	Variation rate（%）	/	−3.7	−11.11	−9.88
Re,300	Values	0.64	0.64	0.6	0.59
	Variation rate（%）	/	0	−6.25	−7.81
Re,250	Values	0.58	0.59	0.55	0.54
	Variation rate（%）	/	1.72	−5.17	−6.9
Re,200	Values	0.51	0.52	0.5	0.5
	Variation rate（%）	/	1.96	−1.96	−1.96
Re,150	Values	0.43	0.44	0.43	0.44
	Variation rate（%）	/	2.33	0	2.33

Table 10. The area Ω₁₅₀ enclosed by the load-deflection curve and the coordinate axis at characteristic deflection δ_150.

Specimen ID	SFPUC-H30-1.0%	SFPUC-H40-1.0%	SFPUC-H50-1.0%	SFPUC-H60-1.0%
Ω150 (N∙mm)	324144	322758	307373	292614

Figure 12. Definitions of flexural toughness parameters.

Figure 13. Toughening degree D_I and relative initial flexural toughness ratio R_P of polyurethane concrete with different steel fiber length.

Figure 14. Relative residual flexural toughness ratio R_k of polyurethane concrete with different steel fiber length.

Figure 15. Toughening degree D_I and relative initial flexural toughness ratio R_P of polyurethane concrete with different steel fiber content.

Figure 16. Relative residual flexural toughness ratio R_k of polyurethane concrete with different steel fiber content.