3554 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Test Methods
Testing Methods for Flexural Strength
According to the Chinese standard GB/T 25993-2010 per-
meable pavement bricks and permeable pavement panels
for the flexural strength test of the samples. The flexural
strength of the samples was calculated according to equa-
tion (1).
R
2HB
3Pl
f 2 =(1)
where,
Rf =flexural strength (Mpa)
P =Damage load (N)
l =Distance between two support points (mm),
H =Sample width (mm)
B =Sample thickness (mm)
Testing Methods for Permeability Coefficient
The samples’ permeability coefficient was tested per the
Chinese standard GB/T 25993-2010 for permeable pave-
ment bricks and panels. The formula for calculating the
permeability coefficient is as follows:
KT AHt
QL
=(2)
where,
KT =The permeability coefficient of the specimen at
a water temperature of T °C(cm/s)
Q =Amount of water seeping out at time t seconds
(ml)
L =Thickness of the sample (cm)
A =The upper surface area of the sample (cm2)
H =Water level difference (cm)
t =Time (s)
Testing Methods for Microscopic Morphology
XRD analysis was carried out using a Bruker D8
ADVANCE, with a Cu target wavelength of 1.5406Å, a
tube current of 40 mA and a tube voltage of 40kV. SEM
testing was carried out using a Gemini300 thermal field
emission scanning electron microscope, with conductive
tape dipped in a small amount of powder and attached to
the sample stage, and sprayed with gold for 60 seconds,
and then on-boarded and vacuumed for testing. The sam-
ples were imaged by high-resolution scanning using GE’s
Vtomex-type industrial CT with a scanning voltage of
150 kV, a current of 150 uA, an exposure time of 0.65 s, a
scanning time of 90 min, a resolution of 39 um, and two-
dimensional cuts derived according to a spacing of 39 µm.
RESULTS AND DISCUSSION
Effect of Molding Pressure on the Properties of
Permeable Bricks
Molding pressure is one of the critical factors affecting
the performance of permeable bricks. The high molding
pressure will lead to the construction of connecting pores
between aggregates occlusion, reducing the porosity and
then affected the permeability coefficient. In turn, the small
molding pressure will result in the decline in the strength
of permeable bricks, and can not reach the requirements
of the relevant standards. The results of the effect of differ-
ent molding pressures on the splitting flexural strength and
permeability coefficient of permeable bricks were shown in
Figure 3.
As can be seen from Figure 3, the impact of molding
pressure on the performance of permeable bricks is obvi-
ous, the splitting flexural strength of permeable bricks is
positively correlated with the forming pressure, and the
water permeability coefficient is negatively correlated with
the molding pressure. With the increase of molding pres-
sure, the flexural strength of permeable brick increases, and
the permeability coefficient decreases, when the molding
pressure is less than 2.5 MPa, the flexural strength of per-
meable brick did not satisfy the requirement of the strength
index of the Chinese standard. When the molding pres-
sure is 2.5 MPa, the flexural strength of permeable brick
is 3.06 MPa, meeting the requirement of the index of
Rf3.0 of the Chinese standard and the permeability coef-
ficient of permeable brick is 2.04×10–2 cms–1, which met
the requirement of permeability grade A index. When the
molding pressure up to 4.0MPa, the permeability coef-
ficient of permeable bricks is less than 1.0×10–2cms–1.
Because with the increase of molding pressure, the aggre-
gate will undergo deformation, and collapse, resulting
in smaller gaps between aggregates, lower porosity, and
increased compactness, which in turn lead to increased flex-
ural strength and a decrease in permeability coefficient. As a
result, the molding pressure between 2.5~3.5MPa prepared
permeable brick met the index requirement of permeable
pavement brick and permeable pavement version [Chinese
standard GB/T 25993-2010].
Effect of Sintering System on the Performance of
Permeable Bricks
Sintering process is a critical part of the brick-making
process. The sintering temperature and time significantly
impact the performance of permeable bricks. Generally,
the sintering temperature is controlled between 950°C and
Test Methods
Testing Methods for Flexural Strength
According to the Chinese standard GB/T 25993-2010 per-
meable pavement bricks and permeable pavement panels
for the flexural strength test of the samples. The flexural
strength of the samples was calculated according to equa-
tion (1).
R
2HB
3Pl
f 2 =(1)
where,
Rf =flexural strength (Mpa)
P =Damage load (N)
l =Distance between two support points (mm),
H =Sample width (mm)
B =Sample thickness (mm)
Testing Methods for Permeability Coefficient
The samples’ permeability coefficient was tested per the
Chinese standard GB/T 25993-2010 for permeable pave-
ment bricks and panels. The formula for calculating the
permeability coefficient is as follows:
KT AHt
QL
=(2)
where,
KT =The permeability coefficient of the specimen at
a water temperature of T °C(cm/s)
Q =Amount of water seeping out at time t seconds
(ml)
L =Thickness of the sample (cm)
A =The upper surface area of the sample (cm2)
H =Water level difference (cm)
t =Time (s)
Testing Methods for Microscopic Morphology
XRD analysis was carried out using a Bruker D8
ADVANCE, with a Cu target wavelength of 1.5406Å, a
tube current of 40 mA and a tube voltage of 40kV. SEM
testing was carried out using a Gemini300 thermal field
emission scanning electron microscope, with conductive
tape dipped in a small amount of powder and attached to
the sample stage, and sprayed with gold for 60 seconds,
and then on-boarded and vacuumed for testing. The sam-
ples were imaged by high-resolution scanning using GE’s
Vtomex-type industrial CT with a scanning voltage of
150 kV, a current of 150 uA, an exposure time of 0.65 s, a
scanning time of 90 min, a resolution of 39 um, and two-
dimensional cuts derived according to a spacing of 39 µm.
RESULTS AND DISCUSSION
Effect of Molding Pressure on the Properties of
Permeable Bricks
Molding pressure is one of the critical factors affecting
the performance of permeable bricks. The high molding
pressure will lead to the construction of connecting pores
between aggregates occlusion, reducing the porosity and
then affected the permeability coefficient. In turn, the small
molding pressure will result in the decline in the strength
of permeable bricks, and can not reach the requirements
of the relevant standards. The results of the effect of differ-
ent molding pressures on the splitting flexural strength and
permeability coefficient of permeable bricks were shown in
Figure 3.
As can be seen from Figure 3, the impact of molding
pressure on the performance of permeable bricks is obvi-
ous, the splitting flexural strength of permeable bricks is
positively correlated with the forming pressure, and the
water permeability coefficient is negatively correlated with
the molding pressure. With the increase of molding pres-
sure, the flexural strength of permeable brick increases, and
the permeability coefficient decreases, when the molding
pressure is less than 2.5 MPa, the flexural strength of per-
meable brick did not satisfy the requirement of the strength
index of the Chinese standard. When the molding pres-
sure is 2.5 MPa, the flexural strength of permeable brick
is 3.06 MPa, meeting the requirement of the index of
Rf3.0 of the Chinese standard and the permeability coef-
ficient of permeable brick is 2.04×10–2 cms–1, which met
the requirement of permeability grade A index. When the
molding pressure up to 4.0MPa, the permeability coef-
ficient of permeable bricks is less than 1.0×10–2cms–1.
Because with the increase of molding pressure, the aggre-
gate will undergo deformation, and collapse, resulting
in smaller gaps between aggregates, lower porosity, and
increased compactness, which in turn lead to increased flex-
ural strength and a decrease in permeability coefficient. As a
result, the molding pressure between 2.5~3.5MPa prepared
permeable brick met the index requirement of permeable
pavement brick and permeable pavement version [Chinese
standard GB/T 25993-2010].
Effect of Sintering System on the Performance of
Permeable Bricks
Sintering process is a critical part of the brick-making
process. The sintering temperature and time significantly
impact the performance of permeable bricks. Generally,
the sintering temperature is controlled between 950°C and