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1ACI Materials Journal
ACI MATERIALS JOURNAL TECHNICAL PAPER
In this study, the impact of expanded perlite (EP) and expanded
vermiculite (EV) on the refractory properties of magnesium potas-
sium phosphate cement (MKPC)-based re-resistant materials
were investigated. The physical and mechanical properties of
MKPC paste were tested, and its re retardancy properties were
studied in detail. The results indicate that the incorporation of EP
or EV to MKPC-based refractories brings a notable improvement
in the re resistance and makes a reduction in the apparent density.
However, compared with EV-MKPC, the porosity of EP-MKPC is
larger and its moisture content is higher, so the thermal insulation
performance of EP-MKPC is better than that of EV-MKPC at the
same content.
Keywords: apparent density; expanded perlite; expanded vermiculite;
re resistance; magnesium potassium phosphate cement (MKPC)-based
refractories.
INTRODUCTION
Magnesium phosphate cement (MPC) is a new inorganic
cementitious material with the advantages of both cement
and ceramics, which is made of magnesium oxide, retarder,
and soluble phosphate in accordance with the corresponding
mixture ratio. MPC has become an important research object
in the building materials industry in recent years because
of its high early strength, fast setting speed, good bonding
performance, and good volume stability.1-5 It has made
outstanding contributions to stabilizing hazardous or radio-
active nuclear waste6 and quickly repairing roads.7,8 Studies
have reported that MPC also boasts good resistance to high
temperature,9-11 but there are few reports on the use of MPC
as refractory. This is because most re-resistant materials are
expensive and toxic.
Expanded perlite (EP) or expanded vermiculite (EV) is
a common re-resistant and heat-insulating material with
excellent re-retardant performance, which is benecial
to improving the re-resistant performance of MPC. High
temperature exposure and volume expansion are conducive
to improving the re resistance of expanded perlite.12 EP
has high absorptivity, incombustibility, extremely low bulk
density, and low thermal conductivity properties, making it
ideal for refractory and heat insulation. Koksal et al.13 found
that expanded vermiculite is also a good refractory material.
Because it can signicantly improve the volume stability
of concrete at high temperature, it is very suitable for the
production of cement-based refractory insulation materials.
In previous experiments, a mixture of three material,
MKPC, EP, and EV was applied to reproof panels and high
temperature vessels (baking furnaces, sintering furnaces,
heating furnaces) as a new type of refractory insulation mate-
rial to resist re and high temperature. EP and EV, as llers
will be studied on the ground of its inuence on this new
type of refractory insulation material. The exural strength,
apparent density, and re resistance of MKPC-based refrac-
tories were measured. Moreover, the results of thermo-grav-
imetric and dierential scanning calorimeter (TG-DSC) and
scanning electron microscope (SEM) are expected to clarify
the re-resistance properties and re-resistance mechanism
of new inorganic re-resistant materials.
RESEARCH SIGNIFICANCE
Magnesium potassium phosphate cement (MKPC), a new
type of energy-saving and environmental protection green
cementing material, was used in the research and devel-
opment of reproof material. Moreover, this new type of
MKPC-based refractory material does not have organic
volatile harmful components and does not produce harmful
components when heated. The development of this new
refractory can contribute to environmental protection (such
as reducing carbon dioxide [CO2] emission).
EXPERIMENTAL INVESTIGATION
Materials
The magnesium oxide for the experiment was supplied by
a local mining company, which was produced by calcining
magnesite at 1500°C (2732°F). The magnesium oxide was
industrial pure grade, the MgO content was more than 95%,
and the average particle size of magnesium oxide in the
experiment was 33.29 μm (0.0013 in.). The admixtures used
were EP and EV with mean particle size of 3.0 and 1.0 mm
(0.12 and 0.04 in.), respectively. EP and EV were used as
the re-resistant insulation components. Besides, industri-
al-grade monopotassium phosphate (KH2PO4) was used in
this study as the acid compound and the purity of KH2PO4
was more than 98%. It is worth noting that adding a retarder
such as borax is unnecessary because the setting time of
MKPC-based refractory becomes longer after the addi-
tion of the re-resistant insulation materials. The chemical
MS No. M-2019-277
Effect of Expanded Perlite or Expanded Vermiculite on
Performance of Magnesium Potassium Phosphate Cement-
Based Refractory
by Yu-Dong Xie, Xu-Jian Lin, Hong-Hong Ai, and Tao Ji
ACI Materials Journal, V. 117, No. 3, May 2020.
MS No. M-2019-277, doi: 10.14359/51724599, received July 15, 2019, and
reviewed under Institute publication policies. Copyright © 2020, American Concrete
Institute. All rights reserved, including the making of copies unless permission is
obtained from the copyright proprietors. Pertinent discussion including author’s
closure, if any, will be published ten months from this journal’s date if the discussion
is received within four months of the paper’s print publication.
2 ACI Materials Journal
compositions of the raw materials are listed in Table 1, and
the performance index of expanded perlite and expanded
vermiculite are listed in Table 2.
Mixture proportion
In the previous experiment with variable P/M by mass,
it was found that the mechanical properties of P/M = 1/3
group were the best of all the groups, and the compressive
strength at 7 days reached 54.52 MPa (7.9 ksi). Accordingly,
P/M is chosen as 1/3 in this study. By changing the content
of EP or EV, the mixing ratio of the combined mixing test
was obtained, as listed in Table 3. The purpose was to
strengthen the re resistance of MKPC-based refractory by
optimizing the ratio of EP or EV. The weight ratio of MKPC-
based refractories without EP or EV (control group) is 1/3
for KH2PO4 to MgO (P/M) and 0.16 for water to M + P
(water-cement ration [w/c]), where C denotes M+P. The M +
P part of MKPC-based refractories is replaced by EP or EV.
When mixed with EP or EV by volume, C stands for M + P
+ EP or M + P + EV. In the following test results, EP-MKPC
and EV-MKPC represent a new type of refractory insulation
material respectively made up of a mixture of MKPC-based
and EP or a mixture of MKPC-based and EV.
Flexural strength and apparent density
The specimen used in the exural strength test was formed
in a mold of 40 x 40 x 160 mm (1.57 x 1.57 x 6.3 in.). First,
the raw materials (M, P, EP, or EV) were stirred in a blender
for 3 minutes to prevent layering. Next, water was added to
the blender and run at low speed for 30 seconds, then at high
speed for 60 seconds. The mixture was then quickly placed
into the mold and vibrated on the vibrator for 120 seconds
to form a dense MKPC-based refractory. Finally, the spec-
imens were demolded 2 hours after casting, and then were
cured in the indoor environment (20 ± 2°C [68 ± 3.8°F], RH
< 50%) for dierent ages. According to the Chinese Stan-
dard,14 the exural strength of the specimens was measured
for 7, 14, and 28 days.
Because the apparent density is an indirect reection of the
internal porosity of the material, an apparent density test was
performed with the use of molds of 70.7 x 70.7 x 70.7 mm
(2.78 x 2.78 x 2.78 in.). In this experiment, the uniformly
stirred slurry was rst placed into the mold, slightly vibrated
and tampered, and then released after the slurry was dried
and solidied. After 28 days of curing under standard condi-
tions, it was placed in an oven at 45 to 50°C (113 to 122°F)
and dried to a constant weight, and then taken out and cooled
to room temperature in a dryer. Finally, the volume and mass
of the specimens were measured with vernier and electronic
balance, respectively, and then the apparent density was
calculated using Eq. (1)
G
V
(1)
where ρ denotes the apparent density (g/cm3 [lb/ft3]); G is
the mass (g [lb]); and V represents the volume (cm3 [ft3]).
Fire resistance
This study was based on the Chinese Code GB33544-
2017,15 and the re resistance of potassium magnesium
phosphate cement was measured by the “re resistance
limit” index in this study. During this test, the specimens
for the re resistance limit test were formed in molds of 16
x 50 x 100 mm (0.63 x 1.97 x 3.94 in.). The forming and
curing process of these specimens is the same as that of the
previous section. The re resistance limit test of the speci-
mens was tested after 28 days. The thickness of the speci-
mens was controlled at 16 mm (0.63 in.) in all re resistance
experiments. In each re resistance limit test, the spec-
imen was rst placed on the support of the combustion test
machine, two thermocouples were placed in the back of the
Table 1—Chemical composition, %wt.
Material SiO2Al2O3Fe2O3CaO MgO SO3K2O Na2O LOI
M 2.68 0.60 0.96 2.54 92.55 0.061 0.015 —0.27
EP 76.29 13.37 0.96 1.07 0.18 —3.32 4.37 —
EV 39.56 12.7 11.23 4.24 18.29 —3.84 0.88 —
Table 2—Performance index of expanded perlite and expanded vermiculite
Material
Particle size,
mm (in.)
Bulk density,
kg/m3 (lb/ft3)
Thermal conductivity, W/
(m·K) (Btu/(ft2.h.°F)) Refractoriness, °C (°F) pH (in water)
EP 3.0 (0.12) 83 (5.18) 0.035 (0.02) 1300 (2372) 7.0
EV 1.0 (0.04) 530 (33.09) 0.05 (0.03) 1100 (2012) 6.1
Table 3—Mixture proportion of MKPC-based
refractories
Samples P/M w/cEP, % EV, %
C 1/3 0.16 0 0
EP 1.0 1/3 0.16 10 0
EP 1.5 1/3 0.16 15 0
EP 2.0 1/3 0.16 20 0
EP 2.5 1/3 0.16 25 0
EP 3.0 1/3 0.16 30 0
EV 1.0 1/3 0.16 0 10
EV 1.5 1/3 0.16 0 15
EV 2.0 1/3 0.16 0 20
EV 2.5 1/3 0.16 0 25
EV 3.0 1/3 0.16 0 30
3ACI Materials Journal
specimen of which the front directly was set on re, and the
thermocouple probe was xed as well. Thermocouple wires
were pierced from the small hole on the right side of the
combustion test machine and connected to the temperature
acquisition box. The temperature acquisition box and the
computer storing data constituted the temperature acquisi-
tion system. And then when the sample was burned with an
alcohol burner, the vertical distance between the nozzle and
the specimen was 70 mm (2.76 in.).
Some studies have showed that the struvite-K begins to
dehydrate at temperatures above 60°C (140°F) and the dehy-
dration is almost completed at temperatures around 200°C
(392°F).16-20
Thus, the temperature of thermocouple was recorded
every minute and the time required to reach 200°C (392°F)
was recorded. The test process is shown in Fig. 1.
Pore structure, SEM, and TG-DSC tests
In this experiment, the pore structure of MKPC-based
refractories was measured by helium ow method and gas
adsorption method, and the pore structure of MKPC-based
refractories was tested with an automatic surface aperture
analyzer. To prepare specimens, the MKPC-based refractory
specimens were broken into small pieces, and then appro-
priate fragments were selected from the center of the MKPC-
based refractory specimens. Before the test, the sample was
dried for 6 hours in an oven at 105 ± 2°C (221 ± 3.8°F)
to remove the moisture in the pore. The hydration product
morphologies of the samples were analyzed with with a
scanning electron microscope. The heating rate of TG-DSC
is 10°C (18°F) per minute.
RESULTS AND DISCUSSION
Fire resistance limit time
The re resistance limit time of the samples of the MKPC-
based refractory with dierent EP or EV contents are shown
in Fig. 2. Compared with the control mixture of the MKPC-
based refractory, the re resistance limit time increased
after the samples of the MKPC-based refractory blending
with the EP or EV. With an increasing content of the EV, the
maximum limit value was 159.4%, which was larger than
that of the control mixture of the MKPC-based refractory.
However, with the same content, EP-MKPC has a higher
limit re resistance time than EV-MKPC. Therefore, the re
resistance time of these MKPC-based refractories can be
improved by mixing MKPC-based samples with EP or EV.
Generally, as the microstructure framework of hardened
MPC paste is composed of unreacted raw materials and
struvite-K, the specimen generated is quite dense.21,22 The
decomposition of struvite-K can be described as Eq. (2)23
when the temperature was approximately 250°C (482°F):
MgKPO4·6H2O = MgKPO4 + 6H2O (2)
After the start of the re resistance test, the struvite-K in
the sample began to dehydrate and decompose when the
temperature increased to 60°C (140°F). The higher the
temperature was, the faster the decomposition rate of stru-
vite-K would be accelerated. At the same time, it would
absorb a lot of heat, which greatly delayed the heating rate
of the sample. Therefore, the re resistance limit time of the
control mixture of the MKPC-based refractory can reach
13.8 minutes. However, when MKPC-based samples were
incorporated into EP or EV, the re resistance time was
greatly improved. This may be due to the morphology and
physical properties of the EP or EV material.
TG-DSC analysis
As can be seen from Fig. 3, the endothermic peaks of
the control group, EV 2.0-MKPC and EP 2.0-MKPC, are
between 50 and 252°C (122 and 485.6°F), which is due to
the loss of free water in MKPC-based refractories and chem-
Fig. 1—Fire resistance test diagram.
Fig. 2—Fire resistance limit time for MKPC-based
refractories.
4 ACI Materials Journal
ically-bonded water in the struvite-K, resulting in the weight
loss of the samples. Between 620 and 650°C (1148 and
1202°F), there are small endothermic peaks at the control
but there is no obvious weightlessness.
The weight loss of the EP 2.0-MKPC sample decreases
at a faster rate than that of the other two groups when the
temperature ranges from 50 to 252°C (122 to 485.6°F) and
the rst endothermic peak occurs. The weight loss decreases
at a slower rate for the three samples when the temperature
rose from 252 to 1000°C (485.6 to 1832°F).
For the control specimen, the rst endothermic peak (peak
temperature is 112°C [233.6°F]) appears when the tempera-
ture rises from 61 to 182°C (141.8 to 359.6°F), and the
weight loss rate is 6.29%. When the temperature rises from
385 to 420°C (725 to 788°F), the second endothermic peak
(peak temperature is 410°C [770°F]) appears and the weight
loss rate is 1.1%. There is an exothermic peak and a small
endothermic peak at 350 and 630°C (662 and 1166°F). When
the temperature of EP 2.0 rises from 62 to 238°C (143.6 to
460.4°F), the rst endothermic peak (peak temperature is
120°C [248°F]) appears, and the weight loss rate is 37.2%;
there are an endothermic peak and small exothermic peak at
370 and 385°C (698 and 725°F). When the temperature of
EV 2.0 sample rises from 62 to 246°C (143.6 to 474.8°F),
the rst endothermic peak appears (the peak temperature is
118°C [244.4°F]), and the weight loss rate is 9.9%; there
is a very small exothermic peak at 380°C (71°F). The total
weightlessness rates of control, EP, and EV samples were
10.8%, 44.8%, and 22.5%, respectively, from 50 to 1000°C
(122 to 1832°F). This is because EP 2.0 and EV 2.0 are
porous and they are easy to absorb water. Another reason
is that water can be stored in the internal voids, resulting in
more free water content in MKPC-based refractories slurry
than in the control group. Thus, the mass loss of EP 2.0 and
EV 2.0 is greater than that of the control group after the
free water and crystalline water are heated and evaporated.
However, due to the weaker water absorption eect of EV
and less free water in re-proof panels, the mass loss after
evaporation is smaller than that of EP. As a result, the mass
loss rate of the three groups is: the EP 2.0 > EV 2.0 > the
control.
In the TG-DSC test, the weight loss was mainly caused by
the decomposition of MPP when the temperature was higher
than 200°C (392°F).19 A phase transition may occur when
the temperature is higher than 600°C (1112°F). In addition,
exothermic peaks were observed but no samples showed
weight loss.24,25 The endothermic peaks were observed in
control samples at 630°C (1166°F). However, when MKPC-
based refractory was mixed with EP or EV, the endothermic
peak does not appear.
In this test, when EP was added, the heat transfer rate in the
sample was slower and the dehydration and decomposition
rate of struvite-K between particles was also slower, so the
continuous decomposition time was prolonged. However,
EV-MKPC's re resistance limit time growth rate is not as
obvious as that of EP-MKPC, which is mainly down to the
dierent ways in which EV works. The EV debris mass is
like a small “wall” in the structure which blocks the transfer
of heat, so it delays the heat transfer rate, ultimately leading
to an extension of the re endurance time of the MKPC-
based refractory. Because the thermal conductivity of the gas
phase is much smaller than that of the solid phase, and the
porosity of the EV is smaller than that of the EP, the thermal
insulation performance of the EP-MKPC is better than that
of the EV-MKPC at the same content.
Therefore, adding EP or EV can signicantly improve the
re retardancy of MKPC-based refractories. On this basis,
the main reason why EV-MKPC or EP-MKPC has excel-
lent re resistance is the water evaporation process of the
MKPC-based refractory in which the MKPC-based absorbs
a lot of heat and prevents the melt from diusing into the
substrate. At the same time, EP and EV can improve the re
resistance and prolong the re resistance time by slowing
down the heat transfer rate.
Localized morphology analysis by SEM
Figure 4(a) shows EP is in a honeycombed porous struc-
ture before the re resistance test. It can be found that the
pore structure of the expanded perlite is relatively complete,
and the wall of the pores of dierent pore diameters is clear.
Moreover, because the expanded perlite is tightly wrapped
by the bonding material, each of the expanded perlite parti-
cles can become a separate “bubble” (not connected) which
is independent and closed after the interior is lled with air.
It is benecial to weaken the thermal conductivity of the
material and to greatly enhance its re resistance. This is
because the thermal conductivity of the gas phase is much
smaller than that of the solid phase, and the EP has larger
porosity and a higher content of gas phase than the control
group. For that reason, after incorporating EP, the re resis-
tance of the MKPC-based refractory is greatly improved.
Figure 4(b) shows EV with small fragments is scattered
randomly in the structure before the re resistance test. It
can be found that because the EV fragments are small and
the sheets are spliced and overlapped, it is dicult for the
bonding material to completely wrap the fragments. It is
common for a plurality of fragments to gather together, and
for one gap portion to be lled with cement and for the other
Fig. 3—TG-DSC results of MKPC-based samples.
5ACI Materials Journal
portion to form a disordered distribution of small holes.
Meteorite fragments are like a small “wall” in the struc-
ture that blocks heat transfer and retards heat transfer rates,
thereby improving re resistance.
As can be seen from Table 4, the porosity of EP is higher
than that of EV. In addition, according to the results of the
previous re resistance limit test, it can be found that the
re resistance of EP is better than that of EV. Because of the
fact that EP-MKPC has larger porosity and more gas phase
content than EV-MKPC, EP-MKPC has better re resis-
tance and heat insulation performance at the same content.
These conclusions are consistent with the results obtained
in TG-DSC.
Apparent density
Apparent density is an indirect reection of the internal
porosity of the material. The small apparent density and
the large internal porosity are conducive to improving the
thermal insulation capacity of the reproof board, and the
smaller density is also conducive to engineering construc-
tion. Apparent density in this study refers to the dry density
of the specimen after 28 days of maintenance. As can be
seen from Fig. 5, the apparent density of the MKPC-based
refractory decreases linearly with the addition of EP and EV,
and also decreases linearly with the increase of the content
of expanded vermiculite and expanded perlite. Moreover, EP
has more obvious eect on apparent density than EV.
This is because the density of EP is much smaller than that
of EV. With the same content, the mass of the MKPC-based
refractory replaced by EP particles decreases more, which
leads to the apparent density of EP-MKPC smaller than that
of EV-MKPC. Therefore, EP is more suitable as refractory
and heat insulation material than EV.
Flexural strength
Few researchers have studied the exural strength of the
MKPC-based refractory incorporating refractory materials.
At the same time, if the new MKPC-based refractory in this
study is applied to a reproof board with a large cross-sec-
tional area, its exural strength must be studied. The ex-
ural strength of MKPC-based samples with EP or EV at the
7th, 14th, and 28th day in dierent contents is shown in Fig.
6. It can be found that the exural strength of the MKPC-
based refractory decreases with the increase of the amount
of refractory and heat insulation materials. Although the
minimum exural strength of the MKPC-based samples with
EP at the 28th day only can reach 1.73 MPa (0.25 ksi). this
strength is sucient to meet the actual requirements of the
project partly because this kind of reproof board is mainly
used for re resistance, rather than as a force component.
Because refractory and thermal insulation materials only
play a lling role, they do not participate in the reaction of
Fig. 4—SEM photomicrographs of EP 2.0-MKPC and EV 2.0-MKPC samples before re resistance test: (a) EP-MKPC before
re resistance test; and (b) EV-MKPC before re resistance test.
Table 4—Pore size distribution of MKPC-based samples before re resistance test
No.
Average pore size, nm
(in. × 10–6)
Pore size, %
<20 nm
(7.87 in. × 10–7)
20 to 100 nm
(0.78 to 3.94 in. × 10–6)
100 to 200 nm
(0.39 to 7.87 in. × 10–6)
>200 nm
(7.87 in. × 10–6)
EP 2.0 182.3 (7.18) 20.12 11.19 21.17 47.52
EV 2.0 168.23 (6.62) 23.32 10.13 22.24 44.31
Fig. 5—Apparent density of MKPC-based refractories.
6 ACI Materials Journal
cementitious materials. It can be veried in Fig. 6 that the
more amounts of refractories that are used, the greater the
dispersion of the MKPC-based refractory is, the smaller the
bond strength between particles is, and ultimately the smaller
the exural strength is. The exural strength of EV-MKPC
is higher than that of EP-MKPC when the volume of
EV-MKPC is not dierent from that of EP-MKPC. Because
the particle size of EV is smaller than that of EP, its density is
better, which can be seen from Table 4 and Fig. 5. It has been
found that by reducing the pore of concrete with diameter
greater than 100 nm (3.93 × 10–6 in.) or increasing the pore
of concrete with diameter less than 50 nm (1.97 × 10–6 in.),
the properties of concrete can be greatly improved.26 And
it can be seen from Table 4 that the pore size of EP-MKPC
and EV-MKPC is mainly above 100 nm (3.93 × 10–6 in.),
while the porosity of EP-MKPC is 2.14% higher than that of
EV-MKPC in the pore size range larger than 100 nm (3.93
× 10–6 in.). Therefore, the exural strength of EV-MKPC is
higher than that of EP-MKPC under the condition of small
volume dierence.
CONCLUSIONS
In this paper, the refractory properties of the MKPC-based
refractory control, EP-MKPC, and EV-MKPC samples are
studied. The experiment conclusion as follows:
1. The re test results show that the re endurance time
increases proportionally with the increase of EP or EV
content. When the content increases to 20%, the growth
rate of the re endurance time becomes slower, and the re
endurance time curve tends to be horizontal. The maximum
re resistance limit time is 38.1 minutes when the MKPC-
based refractory is mixed with 30% EP. The MKPC-based
refractories used in this study had excellent re resistance
performances.
2. Adding EP or EV can signicantly reduce the apparent
density and exural strength of the MKPC-based refractory.
The smaller the apparent density is, the more internal voids
there are, the better heat insulation ability of the MKPC-
based refractory is, and the smaller the density is, the easier
it is to be used in engineering construction. In addition, EP
is more suitable as re resistance material being added to
MKPC-based refractories than EV.
3. Based on the TG-DSC, pore structure, and SEM results,
the excellent re-resistant performance of MKPC-based
refractory is mainly attributed to the following aspects:
heat absorption of chemical bonding water in MKPC-based
hydrate products (struvite-K) and free water during the
re-resistant process of MKPC-based refractory. It eec-
tively stops the spread of re. Meanwhile, the good adhe-
sion of MKPC matrix composites plays an important role
in preventing the formation of cracks. EP particles form
“bubbles” in the slurry of the MKPC-based refractory, which
weakens the thermal conductivity of the material, so its re
resistance and heat insulation eect are greatly enhanced.
While the EV chips are like a small “wall” in the structure,
these “walls” retard the heat transfer rate, thereby improving
the re resistance and extending the re endurance time.
However, due to the EP-MKPC having larger porosity and
more gas phase content than EV-MKPC, EP-MKPC has
better re resistance and heat insulation performance at the
same content.
Fig. 6—Flexural strength of MKPC-based samples with EP or EV at 7th, 14th, and 28th day.
7ACI Materials Journal
AUTHOR BIOS
Yu-Dong Xie is a Graduate Student of the Civil Engineering College of
Fuzhou University, Fuzhou, Fujian Province, China. He received his BS
from Taizhou University, Taizhou, China, in 2017. His research interests
include the preparation and mechanism research of new potassium magne-
sium phosphate cement and alkali-activated concrete.
Xu-Jian Lin is a Professor in the Department of Civil Engineering at
Fuzhou University, where she received her BS and MS. She received her
PhD in structural engineering from Zhejiang University, Hangzhou,
Zhejiang, China. Her research interests include the development of new
potassium magnesium phosphate cement.
Hong-Hong Ai is a Postgraduate Student in the Civil Engineering College
of Fuzhou University. She received her BS from Hubei University of Tech-
nology, Hubei, China, in 2013. Her research interests include the mecha-
nism research of magnesium phosphate cement.
Tao Ji is a Professor in the Department of Civil Engineering at Fuzhou
University. He received his BS from Harbin Building University, Harbin,
China, in 1994; his MS from Fuzhou University in 1997; and his PhD in
structural engineering from Zhejiang University in 2000. His research
interests include the application of solid wastes (such as steel slag, tailings,
titanium gypsum, and chemical waste) in building materials and products.
ACKNOWLEDGMENTS
This research was funded by four National Natural Science Foundations
(NSFC) (Approval No. 51479036, 51878179).
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8 ACI Materials Journal
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