Properties and mechanical–environmental efficiency of concrete combining recycled rubber with waste materials

Figures & data

Table 1 Properties of utilised JIS type-II fly ash.

Property	Unit	Value
SiO2 content	%	62.6
Moisture content	%	0.11
Loss on ignition	%	2.2
Density	g/cm^3	2.29
Specific surface area (Blaine value)	cm^2/g	4.087
Flow value ratio	%	107
Activity index
28 days	%	86
91 days	%	98

Figure 1 Low-grade recycled aggregates showing residual mortar.

Table 2 JIS recycled aggregate specifications.

Property	Unit	Grade L	Grade M	Grade H
Density	g/cm^3	–	>2.3	>2.5
Absorption	%	< 7	< 5	< 3
Abrasion	%	–	–	< 35
Fine particles	%	< 2	< 1.5	< 1
Pore volume	%	–	< 45	< 45
Volume of Cl	%	< 0.4 or 0.1
Waste materials
Rubber, mud bricks	%	–	< 2.0
Glass	%	–	< 0.5
Plaster	%	–	< 0.1
Inorganic materials	%	–	< 0.5
Plastic	%	–	< 0.5
Asphalt	%	–	< 0.1
Total	%	–	< 3.0

Table 3 Properties of sand, rubber crumbs and coarse aggregates.

Material	SSD density (g/cm^2)	Absorption (%)	Fineness modulus	Maximum size (mm)
Sand	2.62	2.09	2.74	4
Rubber crumbs	1.10	–	–	3
Normal aggregate	2.71	0.63	6.28	20
Recycled aggregate	2.43	5.81	6.73	20

Figure 2 Rubber crumbs (size 1–3 mm) from recycled rubber tires.

Table 4 Mix proportions and fresh properties.

Series	W (kg/m^3)	C (kg/m^3)	FA (kg/m^3)	S (kg/m^3)	GC (kg/m^3)	NA (kg/m^3)	RA (kg/m^3)	Slump (cm)	Air (%)
Control (normal)	171	342	–	746	–	1015	–	11.0	4.0
No waste		550	–	624	–	1009	–	18.5	5.1
Recycled aggregate						–	905	12.0	5.2
Fly ash		275	275	590	–	955	–	10.0	3.0
Recycled aggregate+fly ash						–	856	16.0	4.5
25% rubber		550	–	468	65	1009	–	10.0	3.6
Recycled aggregate+25% rubber	165					–	905	9.5	5.1
Fly ash+25% rubber		275	275	442	62	995	–	17.0	2.7
Recycled aggregate+fly ash+25% rubber						–	856	13.5	5.1
50% rubber		550	–	312	131	1009	–	9.5	5.7
Recycled aggregate+50% rubber						–	905	13.0	5.0
Fly ash+50% rubber		275	275	295	124	955	–	11.0	4.4
Recycled aggregate+fly ash+50% rubber						–	856	12.5	3.7

Figure 3 Compressive strength development from 7 to 91 days for 0% (top), 25% (middle) and 50% (bottom) rubber crumb replacement ratios.

Figure 4 Effect of rubber crumb replacement ratio on the 28-day compressive strength.

Figure 5 Effect of rubber crumb replacement ratio on the 28-day Young's modulus.

Figure 6 Compressive strength vs. Young's modulus with JSCE standard curve.

Figure 7 Failure mode of specimens under compressive loading: no waste (top left), recycled aggregate (top right), 25% rubber crumbs (bottom left) and recycled aggregate+25% rubber crumbs (bottom right).

Figure 8 Failure mode of normal concrete under compressive loading.

Figure 9 Effect of rubber crumb replacement ratio on the 28-day air permeability coefficient.

Figure 10 Effect of rubber crumb replacement ratio on volume of raw materials.

Figure 11 Volume of raw materials vs. the 28-day compressive strength.

Figure 12 Effect of rubber crumb replacement ratio on weighted strength calculation results.

Figure 13 Weighted strength calculation results normalised by control mix.