Experimental study on mechanical properties of a novel micro-steel fiber reinforced magnesium phosphate cement-based concrete

Abstract

Magnesium phosphate cement (MPC) received increased attention in recent years, but MPC-based concrete is rarely reported. The micro-steel fibers (MSF) were added to MPC-based concrete to enhance its ductility due to the high brittleness in tensile and flexural strength properties of MPC. This paper investigates the effect of MSF volume fraction on the mechanical properties of a new pattern of MPC-based concrete. The temperature development curve, fluidity, cubic compressive strength, modulus of elastic, axial compressive strength, and four-point flexural strength were experimentally studied with 192 specimens, and a scanning electron microscopy (SEM) test was carried out after the specimens were failed. Based on the test results, the correlations between the cubic compressive strength and curing age, the axial and cubic compressive strength of MPC-based concrete were proposed. The results showed that with the increase of MSF volume fraction, the fluidity of fresh MPC-based concrete decreased gradually. MSF had no apparent influence on the compressive strength, while it enhanced the four-point flexural strength of MPC-based concrete. The four-point flexural strength of specimens with MSF volume fraction from 0.25% to 0.75% were 12.3%, 21.1%, 24.6% higher than that of the specimens without MSF, respectively.

Graphical abstract

Keywords

magnesium phosphate cement-based concrete / micro-steel fibers / four-point flexural strength / compressive strength

1 Introduction

Magnesium phosphate cement (MPC) is a new type of inorganic cementitious material with a strong bond, first discovered as dental material and high-temperature resistant product in the 1940s [ 1– 3]. MPC has the advantages of fast condensation, high early and bonding strength, and good durability [ 4– 6] than ordinary Portland cement (OPC). In addition, dead burned magnesia (MgO), the raw material of MPC, can absorb carbon dioxide in the atmosphere, making it come into the discussion of carbon-neutral cement [ 3, 7]. Hence, MPC can partially replace OPC, and it has received increased attention in recent years [ 8].

Previous studies on MPC indicated that the main factors influencing MPC properties were retarder, admixture, and proportion of raw materials [ 9, 10]. Borax is one of the common retarders, which can effectively slow down the hardening time of MPC. Borax may reduce the early strength but hardly affected the final strength [ 9]. Li et al. [ 11] observed that the existence of glacial acetic acid (GAC) could delay the set of MPC based on improving the early strength of MPC. Magnesium-to-phosphate (M/P) and water-to-cement (W/C) ratios were significant factors affecting MPC property. High M/P and low W/C were required to ensure good mechanical durability [ 12]. Feng et al. [ 13] revealed that M/P was the dominant factor in the fluidity, W/C was the most critical parameter on the early strength of MPC. Li et al. [ 14] mentioned that the specimens with M/P of 3 had more cracks than those with M/P of 5 by observing the SEM results, which means higher M/P increased the dense structure of MPC concrete. The existence of admixtures could significantly modify the property of MPC and reduce the cost; Li and Chen [ 15] reported that fly ash (FA) could increase the fluidity and prolong hardening time, MPC with a FA content of 50% gave the highest water-resistance and strength in all specimens. Mo et al. [ 16] stated that the existence of metakaolin (MK) delayed the appearance and development of microcracks, improved the pore structure, and increased the strength of MPC mortars at all ages, which is consistent with the conclusion of Qin et al. [ 17].

It is worth noting that MPC materials showed high brittleness in tensile and flexural strength properties [ 18, 19]. Hence, many scholars [ 18, 20– 25] had added various microfibers into MPC to modify the ductility of MPC materials. Hu et al. [ 20] noted that the MPC with MSF presented ductile destruction, the equivalent flexural strength ratio and the flexural toughness of the specimens improved obviously by 54.3% and 104.5%, respectively, with the increase of MSF volume content from 0.8% to 1.6%, and concluded that the specimens with MSF have better ductility than polyvinyl and basalt fiber (BF). The inclusion of glass fiber (GF) in MPC mortar could improve the flexibility and deformation behavior, afford a ductile failure mode; Fang et al. recommended that the optimal GF content was 2.5% by Ref. [ 21]. Qin et al. [ 22] concluded that BF was more suitable to modify MPC mortar than GF by integrating the test results of flexural toughness, compressive strength, and post-peak residual strengths. Li et al. [ 24] found a high adhesive force between MPC mortar and electron beam (EB) fiber, which prevented the fibers from being pulled out and thus improved the ductility of MPC. Li also advised that the optimum volume fraction of EB fibers ranges from 0.6% to 0.9%.

At present, most of the research on MPC materials is on the cement level, and it should be applied to concrete as soon as possible to expand the application of MPC in civil engineering. Therefore, it is significant to investigate the mechanical properties of MPC-based concrete. Some scholars [ 26– 28] had produced a novel foam concrete by replacing OPC with MPC. The MPC foam concrete had the same high early-strength as MPC, and the better mechanical property, thermal insulation than OPC foam concrete, indicating that it had the potential to be applied to structural concrete [ 26, 28]. Ma et al. [ 29] researched the influence of MK on MPC aerated concrete; like the MPC mortar, MK helped improve the water-resistance and compress strength by making the microstructure denser. This paper intends to develop a new type of MPC-based concrete and study the effect of MSF volume fraction on the fluidity, cubic compress strength (CCS), axial compress strength (ACS), four-point flexural strength (FS), and modulus of elasticity of the MPC-based concrete by testing total 192 specimens.

2 Materials and methods

2.1 Materials

MPC-based concrete was prepared from a mixture of MgO, ammonium dihydrogen phosphate (NH ₄H ₂PO ₄, ADP), a composite retarder (CR), mineral admixtures (FA, MK), and quartz sand (S) with the size of 1–2 mm and 7–12 mm. The calcination temperature of MgO is 2700°C, provided by Liaoning Dashiqiao Tianyi Material Co., Ltd of China. The MgO appearance is shown in Fig. 1(a). The compositions of MgO and mineral admixtures (FA, MK) were presented in Table 1. Industrial grade ammonium dihydrogen phosphate (NH ₄H ₂PO ₄, ADP), purity 98%, obtained from Jinan Bozhi Chemical Co., Ltd of Shandong, China. The appearance of ADP is reported in Fig. 1(b). The FA and MK appearances are shown in Figs. 1(c), and 1(d). The composite retarder was composed of disodium hydrogen phosphate dodecahydrate (Na ₂HPO ₄·12H ₂O, DSP), (Na ₂B ₄O ₇·10H ₂O, B), and glacial acetic acid (CH ₃COOH, GAC). The purity of borax was 95%, which Liaoning Shougang Boroniron Co., Ltd provided. The DSP with a purity of 99% was supplied by Chongqing Wansheng Chuandong Chemical Co., Ltd of China. The appearances of the borax and disodium hydrogen phosphate dodecahydrate are exhibited in Figs. 1(e) and 1(f). Glacial acetic acid was provided by Nanjing Yanhua Chemical Industry Co., Ltd of Jiangsu, China. The appearances of different sizes of quartz sand are displayed in Figs. 1(g) and 1(h). In this study, micro-steel fiber (MSF) was added into MPC-based concrete to study its mechanical properties. The properties of micro-steel fibers (Fig. 2) are listed in Table 2.

2.2 Details of mix compositions and specimen preparation

The proportion of each component of MPC-based concrete used in the test was shown in Table 3. The specimens were divided into four groups according to fiber volume fraction. The ratio of quartz sand to the cement of all MPC-based concrete mixtures was fixed at 1.3:1, the water-cement ratio was 0.12, the mass ratio of MgO and ADP was 2:1, B, DHP, and GAC accounted for 10%, 7.5%, and 0.25% of MgO by mass, respectively. The ratio between quartz sand with a size of 7–12 mm and a size of 1–2 mm was 5. Based on previous studies [ 30, 31], the addition of FA and MK could modify the pore structure and improve the mechanical property and water resistance of MPC. In addition, adding mineral admixture can save cost. Thus FA and MK were adopted to replace 10% of MgO, respectively, in this paper.

At first, MgO, FA, MK, and ADP were mixed with water and stirred quickly for 5 min, then the quartz sand was added and stirred for 3 min. At the last minute, adding micro-steel fibers and stirring at a low speed. Due to the short setting time, the demolding could be carried out after the MPC-based concrete was poured into the mold for about two hours. Then the specimens were cured at the laboratory with a temperature of about 25°C and a humidity of 50%–60%. There are 192 specimens in this study, 48 specimens of 100 mm × 100 mm × 100 mm for CCS test, 96 specimens of 100 mm × 100 mm × 300 mm for ACS test and elastic modulus test under static compression, and 48 specimens of 100 mm × 100 mm × 400 mm for FS test.

2.3 Properties of fresh MPC-based concrete

The fluidity of MPC-based concrete was tested by measuring the expansion range of MPC-based concrete mixtures under a specified vibration state (GB/T 2419−2005) [ 32]. The test was divided into two steps: first, putting the mixed MPC-based concrete into the truncated cone mold quickly and then lifting the truncated cone mold vertically and gently, immediately opening the jumping table to vibrate 25 times, and measuring the diffusion diameter (Fig. 3(a)).

A temperature recorder was used to obtain the temperature development curve of MPC-based concrete within 180 min by inserting the thermocouple into the center of the specimens immediately after the mixed concrete was poured into the mold.

2.4 Mechanical properties

The CCS of MPC-based concrete specimens was measured on a pressure testing machine with a loading rate of 0.8 MPa/s (Fig. 3(b)) according to Chinese standard GB/T 50081−2002 [ 33] at 1, 3, 7, and 28 d of curing age, and three samples were repeated in each group.

Following Chinese standard GB/T 50081-2016, the ACS (Fig. 3(c)) and elastic modulus tests (Fig. 3(d)) were carried out with the electro-hydraulic servo universal testing machine. The loading rate of ACS test was 0.8 MPa/s and the loading system of the elastic modulus test was presented in Fig. 4. The elastic modulus of MPC-based concrete is calculated by Eq. (1):

(1) E = \frac{F_{\mathrm{a}}-F_0}{A} \times \frac{L}{{\mathrm{\Delta }}_{\mathrm{n}}} , {\mathrm{\Delta }}_{\mathrm{n}} = {\epsilon }_{\mathrm{a}} - {\epsilon }_0 ,

where E = elastic modulus of MPC-based concrete (MPa), F _a, F ₀ = load when the stress is one-third of the ACS and 0.5 MPa (N), respectively, A = the bearing area of specimens (mm ²), L = the gauge distance (mm), ε _a, ε ₀ = the average value of deformation on both sides of the specimens when the load is F _a and F ₀ (mm), respectively.

FS experiment was conducted with the electronic universal testing machine at a loading rate of 0.08 MPa/s according to the method recommended by Chinese standard GB/T 50081-2016 (Fig. 3(e)). The FS of MPC-based concrete is calculated by Eq. (2):

(2) f_{\mathrm{f}} = \frac{Fl}{b{h}^2} ,

where f _f = the FS of MPC-based concrete (MPa), F = the failure load (N), l = the span between two supports (mm), b, h = height and width of the specimens (mm), respectively.

SEM analysis of MPC-based concrete was done through a JSM-6510 scanning electron microscope (Fig. 3(f)).

3 Results and discussion

3.1 Fluidity

Figure 5 listed the results of the influence of different MSF volume fractions on the fluidity of MPC-based concrete. With the increase of MSF volume content, the fluidity of fresh MPC-based concrete decreased gradually. The reason for the decrease of fluidity is that with the increase of MSF content, the fiber surface area also increases, leading to the supplement of friction resistance inside MPC-based concrete and affecting its fluidity. Specimens M0 gave the best fluidity; the fluidity of the specimens with fiber volume fraction from 0.0% to 0.75% were 274, 251, 230, and 203 mm.

3.2 Temperature development curve

Temperature development curves for MPC-based concrete with different sizes were presented in Fig. 6. Initially, the central temperature of MPC-based concrete rose slowly and then accelerated to reach the peak temperature and then began to decline slowly. The central peak temperature of specimens was around 70°C–80°C.

3.3 Cubic compressive strength (CCS)

3.3.1 Effect of MSF volume on the CCS of MPC-based concrete

The influence of the addition of MSF on the CCS of MPC-based concrete was presented in Fig. 7. MPC-based concrete showed the same failure pattern as ordinary concrete with a failure shape of conical. The CCS of MPC-based concrete improved significantly with the prolonged curing age. The CCS of specimens MSF-M1 was slightly higher than that of specimens M0 at all four curing ages. The CCS of specimens MSF-M2 at 3 and 7 d of curing time were close to the control group (without MSF) but decreased at 28 d of curing time. However, when the fiber volume fraction reached 0.75%, the CCS decreased at four curing ages. Because of the excellent adhesion between MPC and MSF [ 34], the random distribution of MSF in MPC-based concrete can inhibit the development of microcracks, thus improving the CCS of the specimens. However, excessive fiber would lead to many voids in MPC-based concrete, resulting in the decrease of the CCS of the specimens. According to Aminul Haque’s [ 18] report, this phenomenon is due to the rapid neutralization reaction rate of MPC-based concrete, and the increase of fiber content leads to many pores in hardened concrete, which inhibits the formation of hydration products by rapid reaction of MPC.

3.3.2 The correlation between CCS and curing age

The CCS of specimens M0, specimens MSF-M1, specimens MSF-M2, and specimens MSF-M3 at 7 d of curing age reached about 79.9%, 81.3%, 94.6%, and 91.4% of the CCS of specimens at 28 d of curing time, respectively, which indicated that MPC-based concrete had the characteristics of high early strength. The CCS of concrete with an age t is related to the type of cement, curing conditions, and temperature. Figure 8 demonstrated the correlation between CCS and curing age of specimens with different volume fractions of MSF under the same mixing and curing conditions. Equations (3)–(6) with logarithmic correlation were obtained to illustrate the relationship between the CCS and curing time of M0, MSF-M1, MSF-M2, and MSF-M3, respectively.

(3) f_{\mathrm{c}\mathrm{u},0} = 11.748 \ln t + 37.672 ,

(4) f_{\mathrm{c}\mathrm{u},0.25} = 12.039 \mathrm{l}\mathrm{n} t + 38.665 ,

(5) f_{\mathrm{c}\mathrm{u},0.5} = 10.875 \mathrm{l}\mathrm{n} t + 34.763 ,

(6) f_{\mathrm{c}\mathrm{u},0.75} = 6.807 \mathrm{l}\mathrm{n} t + 25.390 ,

where f _cu,0, f _cu,0.25, f _cu,0.5, f _cu,0.75 = CCS of specimens with 0%, 0.25%, 0.5%, 0.75% MSF, respectively. t = curing age.

3.4 Axial compressive strength (ACS)

3.4.1 Effect of MSF volume on the ACS of MPC-based concrete

The failure shape of MPC-based concrete was the oblique failure plane formed by the connection of longitudinal cracks. Figure 9 indicated that the effect of MSF on ACS and ACS of specimens is consistent. The ACS of the specimens with a fiber volume fraction of 0.25% is nearly close to that of the specimens without fiber. However, the ACS of the specimens with a fiber volume fraction of 0.75% at 28 d of curing time decreased 30.6% compared with the specimens without MSF, which is also due to the fiber leading to more pores and defects in MPC-based concrete. The ACS of specimens M0, MSF-M1, MSF-M2, and MSF-M3 at 7 d of curing reached about 54.5%, 51.2%, 56.7%, and 82.4% of the ACS of specimens at 28 d of curing, respectively, which also showed the high early strength behavior.

3.4.2 The correlation between ACS and CCS

Figure 10 illustrated the relationship between ACS and CCS by fitting the strength values of MPC-based concrete. Equations (7) and (8) showed the correlation between ACS and CCS at the early age (1, 3, 7 d) and 28 d of curing time, respectively. The coefficient at 28 d is higher than that at the early age because the hydration reaction of MPC is not complete, and the bond force between aggregate, MSF, and MPC is not significant at the early age. In addition, the ratio of the ACS to CCS is related to the properties of concrete materials. The correlation coefficient obtained in this paper at 28 d of curing age was between 0.55 and 0.79, which is lower than what we usually know. This may be due to the characteristics of MPC materials.

(7) f_{\mathrm{c}} = 0.43 f_{\mathrm{c}\mathrm{u}} ,

(8) f_{\mathrm{c}} = 0.64 f_{\mathrm{c}\mathrm{u}} ,

where f _c = ACS, f _cu = CCS.

3.5 Elastic modulus

The effect of MSF content on the elastic modulus of MPC-based concrete was shown in Fig. 11. Elastic modulus had the same trends affected by MSF as the compressive strength, which means a significant positive correlation between elastic modulus and CCS of MPC-based concrete. The elastic modulus increased first with the increase of MSF content and then decreased when the MSF volume fraction is 0.5%, and the modulus of elasticity of concrete increased with the prolonged curing age.

3.6 Flexural strength (FS)

3.6.1 Effect of MSF volume fraction on the FS of MPC-based concrete

The failure modes of MPC-based concrete under four-point flexural strength test at 1, 3, 7, 28 d of curing were similar, and Fig. 12 presented the failure patterns of MPC-based concrete with different MSF volume content at 28 d of curing. All the cracks appeared in the pure bending section. The specimens without fiber were divided into two pieces after failure with a brittle failure mode, while the specimens MSF-M1, MSF-M2, and MSF-M3 were not divided into two pieces because of the existence of MSF.

The effect of MSF volume fraction on the FS of MPC-based concrete was reported in Fig. 13. Overall, MSF had an enhancement effect on the FS of concrete, and the more MSF was added, the more pronounced the enhancement effect would be. The FS of specimens MSF-M1, MSF-M2, and MSF-M3 reached 6.4, 6.9, and 7.1 MPa at 28 d of curing age, which were 12.3%, 21.1%, and 24.6% higher than that of the control group, respectively. As presented in Fig. 13, the FS of MPC-based concrete at each curing age improved with the increase of MSF content except the FS of concrete with MSF volume fraction of 0.5% at one day of curing time, which may be due to the quality of mixing. Because of the high early strength property of MPC-based concrete, the FS of specimens M0, MSF-1, MSF-M2, and MSF-M3 had reached 3.3, 3.8, 3.2, and 4.1 MPa in one day, which were 57.9%, 59.3%, 46.4% and 57.7% of 28-day FS, respectively.

The load-deformation curves of MPC-based concrete with 0%–0.75% MSF at 1, 3, 7, and 28 d of curing age were shown in Fig. 14. The deformation of the specimen was obtained directly from the testing machine. Each curve was the average test results of three repeated specimens. The load-deformation curve can usually be divided into three stages, elastic or linear, deflection hardening or nonlinear, and deflection softening behavior [ 35]. Two failure modes can be recognized from the load-deformation curves; MPC-based concrete without MSF showed brittle behavior at 1, 3, 7, and 28 d and failed immediately after reaching the ultimate strength. On the contrary, the MPC-based concrete with MSF showed remarkable ductility with a deflection softening behavior, which indicated that MSF could significantly improve MPC-based concrete ductility, thus eliminating the sudden failure after peak load. This is because MSF is randomly distributed in MPC-based concrete, and it has a strong bond with MPC-based concrete to inhibit the development of cracks and improve the ductility of MPC-based concrete.

3.6.2 Flexural-cubic compressive strength ratio

The FS-CCS ratio is a physical quantity reflecting the toughness of materials. Figure 15 illustrated the FS-CCS ratio of specimens with different MSF content at 28 d. The specimens with a large FS-CCS ratio show better ductility. The addition of MSF can improve the crack resistance of concrete, and the improvement effect on the ACS is higher than that on the FS. Thus, it can be concluded from Fig. 15 that the FS-CCS ratio of the specimens increased with the increase of the MSF content.

3.7 SEM analysis

The SEM test was carried out to qualitatively verify the assumption that the fiber would result in more pores in the concrete. The quantitative influence of MSF on concrete strength was verified by the compressive strength test. Figure 16 presented the SEM images of MPC-based concrete with and without MSF. It can be seen from the images that there are some pores in the interface between MSF and MPC, while the specimens without MSF presented a denser microstructure. This phenomenon further confirms that there will be more pores in the concrete when the fiber content increases, resulting in the reduction of concrete strength.

4 Conclusions

The primary purpose of this paper was to explore the effect of the volume content of MSF on the mechanical properties of MPC-based concrete. The following conclusions can be drawn according to the experimental results.

1) The fluidity of fresh MPC-based concrete decreased gradually with the increase of MSF volume content. The fluidity of specimens M0, MSF-M1, MSF-M2, MSF-M3 were 274, 251, 230, and 203 mm, respectively.

2) MPC-based concrete had the high early strength. The cubic compressive strength of specimens M0, MSF-M1, MSF-M2, MSF-M3 at 7 d of curing time reached about 79.9%, 81.3%, 94.6%, and 91.4% of specimens at 28 d of curing time, respectively. The effect of volume fraction of MSF on the cubic and axial compressive strength and elastic modulus of MPC-based concrete were consistent. The specimens with an MSF volume content of 0.25% showed better mechanical properties.

3) The increase of MSF content would lead to more holes in the concrete, decreasing the strength of concrete.

4) The bending strength of MPC-based concrete increased with the increase of MSF volume content. The existence of MSF restrains the development of tensile cracks, improves the ductility of MPC-based concrete and its four-point flexural strength.

5) The load-deformation curves indicated that the MPC-based concrete without MSF shows a brittle failure mode with sudden destruction after peak load, while the MPC-based concrete with MSF shows a ductile failure mode, which proved that MSF could improve its ductility.

6) The flexural-cubic compressive strength ratio of the specimens increased with the increase of the MSF content, which indicated that MSF could improve the ductility of MPC-based concrete.

7) Logarithmic equations were proposed to demonstrate the correlation between cubic compressive strength and curing time, the relationship between cubic and axial compressive strength of specimens, and the strength values calculated by the equations agree well with the experimental results.

References

[1] Seehra S S, Gupta S, Kumar S. Rapid setting magnesium phosphate cement for quick repair of concrete pavements-characterization and durability aspects. Cement and Concrete Research, 1993, 23( 2): 254– 266

[2] Prosen E M. US Patent, 2152152, 1939-03-28

[3] Haque M A, Chen B. Research progresses on magnesium phosphate cement: A review. Construction and Building Materials, 2019, 211 : 885– 898

[4] Yang Q, Zhu B, Wu X. Characteristics and durability test of magnesium phosphate cement-based material for rapid repair of concrete. Materials and Structures, 2000, 33( 4): 229– 234

[5] Qiao F, Chau C K, Li Z J. Property evaluation of magnesium phosphate cement mortar as patch repair material. Construction and Building Materials, 2010, 24( 5): 695– 700

[6] Wang Y S, Dai J G. Use of magnesia sand for optimal design of high performance magnesium potassium phosphate cement mortar. Construction and Building Materials, 2017, 153 : 385– 392

[7] Walling S A, Provis J L. Magnesia-based cements: A journey of 150 years, and cements for the future?. Chemical Reviews, 2016, 116( 7): 4170– 4204

[8] Chau C K, Qiao F, Li Z J. Microstructure of magnesium potassium phosphate cement. Construction and Building Materials, 2011, 25( 6): 2911– 2917

[9] Yang Q B, Wu X L. Factors influencing properties of phosphate cement-based binder for rapid repair of concrete. Cement and Concrete Research, 1999, 29( 3): 389– 396

[10] Ahmad M R, Chen B. Effect of silica fume and basalt fiber on the mechanical properties and microstructure of magnesium phosphate cement (MPC) mortar. Construction and Building Materials, 2018, 190 : 466– 478

[11] Li J, Ji Y S, Huang G D, Jin C. Retardation and reaction mechanisms of magnesium phosphate cement mixed with glacial acetic acid. RSC advances, 2017, 7( 74): 46852– 46857

[12] Xu B, Winnefeld F, Kaufmann J, Lothenbach B. Influence of magnesium-to-phosphate ratio and water-to-cement ratio on hydration and properties of magnesium potassium phosphate cements. Cement and Concrete Research, 2019, 123 : 105781–

[13] Feng L, Chen X Q, Wen X D, Zhang Z, Shou L. Investigating and optimizing the mix proportion of sustainable phosphate-based rapid repairing material. Construction and Building Materials, 2019, 204 : 550– 561

[14] Li Y, Sun J, Chen B. Experimental study of magnesia and M/P ratio influencing properties of magnesium phosphate cement. Construction and Building Materials, 2014, 65 : 177– 183

[15] Li Y, Chen B. Factors that affect the properties of magnesium phosphate cement. Construction and Building Materials, 2013, 47 : 977– 983

[16] Mo L W, Lv L M, Deng M, Qian J. Influence of fly ash and metakaolin on the microstructure and compressive strength of magnesium potassium phosphate cement paste. Cement and Concrete Research, 2018, 111 : 116– 129

[17] Qin Z H, Ma C, Zheng Z Q, Long G, Chen B. Effects of metakaolin on properties and microstructure of magnesium phosphate cement. Construction and Building Materials, 2020, 234 : 117353–

[18] Aminul Haque M, Chen B, Riaz Ahmad M, farasat ali shah S. Mechanical strength and flexural parameters analysis of micro-steel, polyvinyl and basalt fibre reinforced magnesium phosphate cement mortars. Construction and Building Materials, 2020, 235 : 117447–

[19] Ahmad M R, Chen B, Yu J. A comprehensive study of basalt fiber reinforced magnesium phosphate cement incorporating ultrafine fly ash. Composites. Part B, Engineering, 2019, 168 : 204– 217

[20] Hu F, Sheikh M N, Hadi M N S, Gao D, Zhao J. Mechanical properties of micro-steel fibre reinforced magnesium potassium phosphate cement composite. Construction and Building Materials, 2018, 185 : 423– 435

[21] Yuan F G, Chen B, Oderji S Y. Experimental research on magnesium phosphate cement mortar reinforced by glass fiber. Construction and Building Materials, 2018, 188 : 729– 736

[22] Qin J H, Qian J S, Li Z, You C, Dai X, Yue Y, Fan Y. Mechanical properties of basalt fiber reinforced magnesium phosphate cement composites. Construction and Building Materials, 2018, 188 : 946– 955

[23] Aminul Haque M, Chen B, Ahmad M R, Shah S F A. Evaluating the physical and strength properties of fibre reinforced magnesium phosphate cement mortar considering mass loss. Construction and Building Materials, 2019, 217 : 427– 440

[24] Li J, Ji Y S, Jin C, Xu Z S. Improvement and mechanism of the mechanical properties of magnesium ammonium phosphate cement with Chopped fibers. Construction and Building Materials, 2020, 243 : 118262–

[25] Liu Y T, Qin Z H, Chen B. Experimental research on magnesium phosphate cements modified by red mud. Construction and Building Materials, 2020, 231 : 117131–

[26] Li Y, Chen B. New type of super-lightweight magnesium phosphate cement foamed concrete. Journal of Materials in Civil Engineering, 2015, 27( 1): 04014112–

[27] Ma C, Chen B. Experimental study on the preparation and properties of a novel foamed concrete based on magnesium phosphate cement. Construction and Building Materials, 2017, 137 : 160– 168

[28] Li T, Wang Z, Zhou T, He Y, Huang F. Preparation and properties of magnesium phosphate cement foam concrete with H ₂O ₂ as foaming agent. Construction and Building Materials, 2019, 205 : 566– 573

[29] Ma C, Yi G, Long G C, Xie Y. Properties of high-early-strength aerated concrete incorporating metakaolin. Journal of Materials in Civil Engineering, 2019, 31( 10): 04019225–

[30] Xu B W, Lothenbach B, Ma H Y. Properties of fly ash blended magnesium potassium phosphate mortars: Effect of the ratio between fly ash and magnesia. Cement and Concrete Composites, 2018, 90 : 169– 177

[31] Qin Z H, Zhou S B, Ma C, Long G, Xie Y, Chen B. Roles of metakaolin in magnesium phosphate cement: Effect of the replacement ratio of magnesia by metakaolin with different particle sizes. Construction and Building Materials, 2019, 227 : 116675–

[32] GB/T 2419–2005. Test Method for Fluidity of Cement Mortar. Beijing: Standards Press of China, 2005

[33] GB/T 50081–2002. Standard for Test Method of Mechanical Properties of Ordinary Concrete. Beijing: China Architecture & Building Press, 2003

[34] Feng H, Li L L, Zhang P, Gao D, Zhao J, Feng L, Sheikh M N. Microscopic characteristics of interface transition zone between magnesium phosphate cement and steel fiber. Construction and Building Materials, 2020, 253 : 119179–

[35] Jalasutram S, Sahoo D R, Matsagar V. Experimental investigation of the mechanical properties of basalt fiber-reinforced concrete. Structural Concrete, 2017, 18( 2): 292– 302

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