Brucite modified epoxy mortar binders: Flame retardancy, thermal and mechanical characterization

Construction and Building Materials xxx (2015) xxx–xxx

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Brucite modified epoxy mortar binders: Flame retardancy, thermal and mechanical characterization Yuge Zhang a, Yifan Sun a, Ke Xu a, Zuanru Yuan b, Jing Zhang a, Ru Chen a, Hongfeng Xie a,⇑, Rongshi Cheng a,c a Key Laboratory of High Performance Polymer Materials and Technology, Ministry of Education, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China b Modern Analysis Center, Nanjing University, Nanjing 210093, China c College of Material Science and Engineering, South China University of Technology, Guangzhou 510641, China

h i g h l i g h t s  Environmentally-friendly flame-retarded epoxy mortar binder (EMB) has been developed.  The synthetic brucite significantly enhances the flame retardancy, thermal stability and mechanical properties of EMBs.  The viscosity of brucite modified EMBs is low enough to satisfy the requirement of mortar pavement even at 60 °C.

a r t i c l e

i n f o

Article history: Received 15 January 2015 Received in revised form 10 April 2015 Accepted 2 May 2015 Available online xxxx Keywords: Polymer mortar Brucite Flame retardant Thermal stability Mechanical properties

a b s t r a c t Polymer mortar with excellent mechanical strength and durability has been widely used in road pavement and other construction industry. In this study, two kinds of brucites, synthetic and natural brucites were incorporated in the epoxy mortar binders as flame retardants. The components and morphology of the two kinds of brucites were investigated. The flame retardancy of brucite-modified epoxy mortar binders was evaluated by the horizontal burning and limiting oxygen index tests. The influence of flame retardants on the rotational viscosity, the thermal and mechanical properties of epoxy mortar binders was determined by differential scanning calorimetry, thermogravimetric analysis, and universal test machine. Furthermore, the morphology of flame retarded-epoxy mortar binders was characterized by scanning electron microscopy. The addition of brucites significantly improved the flame retardancy, thermal stability and tensile strength of epoxy mortar binders. Especially in the case of the addition of 20 wt% synthetic brucites in epoxy mortar binders, from FH-3 to FH-1 reduction in the horizontal burning classification, 5.5% improvement in limiting oxygen index, 15% increment in tensile strength were obtained. Ó 2015 Elsevier Ltd. All rights reserved.

1. Introduction Polymer mortars are concrete-like composites with the composition of aggregates and polymer binder, which have been widely used in bridge and tunnel decking, runway overlay, concrete structures surface defect treatment, and other construction industry, because of its fast curing, very low permeability, strong adhesive force to other materials, ability to withstand frost, salt, alkali and acid, construction convenient, and other specific properties [1]. As one of thermosetting polymers, epoxy resin has been often used as polymer binders to improve the adhesion, impermeability, resilience and durability of polymer mortar [2]. However, one of the

⇑ Corresponding author.

major concerns when using epoxy mortar is its flammability, especially when it is used in the tunnels, since epoxy resins normally are flammable (limiting-oxygen index, LOI = 18–22%) [3]. Li et al. [4] reported that the cycloaliphatic epoxy resin can cause dripping with burning, because of its lower LOI and melt viscosity. Epoxy mortar has a strong flammability at 400 °C with releasing dense black smoke, despite large proportion of aggregates in it [5]. During its combustion, abundant combustible volatile ingredients mixed with the surrounding air burn intensely above epoxy mortars. Therefore, in order to enhance the fire properties of epoxy mortars, flame retardants have been often added into the epoxy binder, such as the halogen-containing and halogen-free flame retardants [6,7]. Considering the generation of the toxic, corrosive, halogenated gases with the halogen flame retardant system, more and more attention has been attracted to the halogen-free flame

http://dx.doi.org/10.1016/j.conbuildmat.2015.05.037 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved.

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retardant [7]. Especially now, increasing attention has been paid on the flame retardancy of 9,10-dihydro-9-oxa-10-phosphaphe nan-threne-10-oxide (DOPO) and its derivatives [8]. However, it also needs to be considered the economic reasons when choosing the flame retardants. Brucite, which main ingredient is a magnesium hydroxide (MH), Mg(OH)2, has the highest magnesium contents among the raw materials of magnesium-containing ores [9]. When the brucites are heating, the main ingredient MH begins to decompose into MgO and H2O at a relatively higher temperature (300 °C). At the same time, in the flame phase, water vapor forms an envelope around the flame, which tends to exclude the air and dilute the flammable gases. The MgO residue forms a thermally inert layer that could create a protective barrier on the polymer substrate [10]. Especially, in recent years, as a kind of non-halogen flame retardant in polymers, brucite has been attracted much attention because of its excellent performance of flame retardancy, smoke suppression, and thermal stability [11]. To the best of our knowledge, however, few studies were available on the flame retardancy of brucite modified polymer mortar binders. The main focus of this paper is to explore the impacts of the synthetic brucite (SB) and natural brucite (NB) on the properties of epoxy mortar binders (EMBs). Two kinds of brucites were incorporated into epoxy mortar binders as flame retardants. The LOI and horizontal burning rate of brucite retarded EMBs were determined. Furthermore, the rotational viscosity, fire, thermal, mechanical, and morphological properties of brucite modified EMBs were studied. 2. Experimental 2.1. Materials The epoxy mortar binder was obtained from Nanjing Pureness Advanced Materials Co. Ltd., China. It consists of two components: epoxy resin and curing agent by mass ratio of 72:28. The detailed properties of epoxy resin and cure agents are demonstrated in Table 1. Two kinds of brucites (2000 mesh) powders, SB and NB, were obtained from Wuxi Daxin Environment Protection Materials Co. Ltd., China. The chemical components of brucites are given in Table 2. The specific surface area, pore-size distribution and micropore volume of SB and NB were measured by the nitrogen chemisorption isotherm technique. The analysis bath temperature was 195.6 °C. The surface characteristics of SB and NB are shown in Table 3. 2.2. Samples preparation Epoxy, curing agent and brucite were introduced into a 250 mL beaker and agitated (2000 rpm) for 5 min. Then, the mixtures were cured for 2 days at 60 °C in the polytetrafluoroethylene (PTFE) molds. The mass percent of the two different flame retardants (FR) in the mixtures of EMBs were 0, 10, 20, 30, respectively.

2.3.1. Limiting oxygen index The limiting oxygen index (LOI) is often used to quantify the fire retardancy of materials and the validity of flame retardants. In present study, the HC-2C oxygen index instrument (Shangyuan Analytical Instruments Co., Ltd., Nanjing, China) was

Table 1 Properties of epoxy resin and cure agents.

Viscosity (25 °C, MPa s) Specific gravity (23 °C, g/cm3) Epoxide equivalent weight (g/ eq) Acid value (mg KOH/g)

2.3.2. Horizontal burning The horizontal burning (HB) test of burning of the samples was carried out with CZF-4 type instrument (Nanjing Shangyuan Analytical Instruments Co., Ltd., Nanjing, China) according to ASTM D635. The samples with a size of 123 mm  13 mm  3 mm were oriented horizontally and placed in a test chamber, then the flame of the Bunsen burner was used to ignite the sample for 30 s, the time until the flame extinguished itself and the distance for the burn propagated were measured, then figured out the linear burning rate in mm per minute. 2.3.3. Rotational viscosity Rotational viscosity tests of the neat EMB and brucite modified-EMBs were measured in a NDJ-1C Brookfield rotational viscometer (Shanghai Changji Instrument Co., Ltd. referring to ASTM D4402. The spindle 28 was used and tests were conducted at 60 °C. 2.3.4. Thermogravimetric analysis The thermal decomposition of the two kinds of brucites and brucite modified EMB composites were characterized by a STA 449C TG analyzer (NETZSCH, Germany). The thermogravimetric analysis (TGA) was performed from 25 °C to 800 °C with a scan rate of 20 °C/min in nitrogen atmosphere. 2.3.5. Glass transition temperature The effects of brucites on the glass transition temperature (Tg) were determined by Perkin-Elmer Pyris 1 differential scanning calorimetry (DSC) instrument (Boston, MA, USA). The DSC measurements were conducted from 40 to 80 °C at a scan rate of 20 °C/min under argon. DSC results were presented as curves of heat flow versus temperature, in which Tg is defined as the inflection point. 2.3.6. Mechanical properties Tensile properties of brucites flame retarded-EMBs were evaluated by universal test machine (Instron, Model 4466, Norwood, MA, USA) following ASTM D638. The measurements were conducted with a strain rate of 500 mm/min at room temperature. 2.3.7. X-ray diffraction X-ray diffraction (XRD) measurements of samples were conducted on a Shimadzu XRD-6000 diffractometer using Cu Ka radiation from 2h = 3° to 75°. 2.3.8. Scanning electron microscopy The morphological characterization of brucite/EMB composites were evaluated by using a field-emission scanning electron microscopy (FE-SEM, Hitachi S-4800, Japan) operating at 2 kV. Before the observation, the composite surface fractured in the liquid nitrogen and brucite powders were coated with gold.

3. Results and discussion 3.1. Characteristics of brucites

2.3. Tests and measurements

Property

used to test the LOI values according to ASTM D2863. The samples were molded to the proper size (80 mm  10 mm  4 mm). The test procedures were as following: the sample was fixed vertically in the combustion cylinder and was flowed by the mixture of nitrogen and oxygen in a specific ratio from the bottom. The upper side of the specimen was ignited using a butane gas flame. The time and length of the combustion was recorded. And then the minimum percentage of oxygen to maintain a stable combustion was determined.

Value

Test method

Epoxy resin

Cure agents

10,000– 14,000 1.40

550

ASTM D445

0.93

183–194

–

–

180–220

ASTM D1475 ASTM D1652 ASTM D664

The X-ray diffraction patterns of the brucites are presented in Fig. 1. The primary reflections for brucites appear at 18.6°, 32.8°, 38.0°, 50.8°, 58.7°, 62.2°, 68.3°, and 72.1°, which attribute to the primary diffraction of (0 0 1), (1 0 0), (1 0 1), (1 0 2), (1 1 0), (1 1 1), (1 0 3) and (2 0 1) crystal faces, respectively [12]. It can be seen clearly that the major diffraction peaks of SB is basically the same as those of the pure brucite [13]. This reveales that the SB has high purity in this study. Table 2 provides the chemical component of brucites determined by X-ray fluorescence (XRF). Clearly, the main component of NB is Mg(OH)2, while silicon, sulfur, calcium and iron oxides and hydroxides as main impurity exist in NB. It is well known that the natural brucite mineral is often contaminated with other magnesium minerals such as talc serpentinite, dolomite, and magnesite [14]. Therefore, as shown in Fig. 1, the main peaks of the XRD spectra for NB show the existence of talc, dolomite, and magnesite [15]. The XRF results in Table 2 indicate that NB contains more composition of extra substances as compared with SB.

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Y. Zhang et al. / Construction and Building Materials xxx (2015) xxx–xxx Table 2 Chemical components of brucites. Samples

MgO

SiO2

H2O

CaO

Fe2O3

P2O5

Al2O3

MnO

SO3

SB (%) NB (%)

68.82 63.86

0.02 11.14

30.76 19.00

0.002 5.55

0.002 0.24

– 0.09

– 0.08

– 0.03

0.06 –

Table 3 Physical characteristic of brucites. Physical characteristics BET surface area (m2/g) BJH adsorption cumulative volume of pores between 17,000 and 3,000,000 Å diameter (cm3/g) BJH desorption cumulative volume of pores between 17,000 and 3,000,000 Å diameter (cm3/g) Adsorption average pore width (4V/A by BET) (nm) BJH adsorption average pore diameter (4V/A) (nm) BJH desorption average pore diameter (4V/A) (nm)

SB

NB

8.68 0.044

5.90 0.032

0.043

0.031

11.59 37.82 29.57

11.78 36.02 31.84

The TG and the DTG curves of brucites are presented in Fig. 2. It can be seen that the thermal decomposition of SB includes three stages as shown in Fig. 2b. The main stage of SB decomposition around 423 °C attributes to brucite [16], whereas the tiny thermal decomposition around 524 °C and 619 °C is due to the degradation of talc and magnesite, respectively [17]. These results agree well with that of XRF and XRD, which reveals that SB contains a very small quantity of impurity substance, such as talc and magnesite. For NB, the thermal degradation contains five stages, which are around 263 °C, 440 °C, 524 °C, 598 °C, and 719 °C, respectively. These stages attribute to the dehydration of the zeolitic water and decomposition of brucite, talc, magnesite, and dolomite, respectively [18]. Therefore, TG results also indicate that NB consists of much more impurities as compared with SB. The morphology of the brucites is represented by Fig. 3. The shape of SB particles have a plate-like form (Fig. 3a), which is in agreement with other reports [19]. For NB, some angular and irregular particles are observed in the brucites due to the existence of much more other impurity, as shown in Fig. 3b.

EMBs increases with the increase of flame retardant loadings. The LOI values of EMB with 20 and 30 wt% NB are 24.0% and 26.0%, respectively. Obviously, with 20 wt% brucites, SB/EMB composites show better flame retardancy than NB/EMB composites. It should be noted that the purity and dispersion of brucite play an important role in the flammability for the EMBs. Similar results were also reported in magnesium hydroxide retarded asphalt binders [20]. Although some of the impurities found in NB also exhibit an endothermic decomposition and could play a favorable role in the flame retardancy of the epoxy, the poor dispersion of NB in the EMB as discussed in the last section counteracts the fire retardancy of NBs.

3.2.2. Horizontal burning The HB test is a method which is generally applied to assess the extent and the linear burning rate of the horizontal combustion [21]. Table 4 summarizes the HB data of the neat EMB and brucite/EMB composites. It shows clearly that the HB classification of brucite modified EMB decreases from FH-3-12.63 mm/min to FH-1 with the increasing of the flame retardant loadings. Furthermore, the SB-retarded EMBs have the lower classification than the NB-retarded EMBs. It is noteworthy that the value of LOI increases from 20.5% to 26.0% and HB classification reduces

3.2. Flammability 3.2.1. Limiting oxygen index The LOI values of the neat EMB and flame-retarded EMBs are shown in Table 4. The LOI of the pure EMB is 20.5%. The addition of brucites increases the LOI of EMB. For SB, a maximum LOI is 26.0% appears at the loading of 20 wt%. The LOI of the NB modified

Fig. 1. XRD patterns for two kinds of brucites.

Fig. 2. TG (a) and DTG (b) curves of brucites.

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Fig. 3. SEM images for brucites: SB (a) and NB (b).

Table 4 Flammability results of pure EMB and brucite modified EMBs. Sample

HB classification

LOI (%)

Neat EMB 10 wt% SB 20 wt% SB 30 wt% SB 10 wt% NB 20 wt% NB 30 wt% NB

FH-3-12.6 mm/min FH-2-31.0 mm FH-1 FH-1 FH-2-33.3 mm FH-1 FH-1

20.5 23.5 26.0 24.0 23.0 24.0 26.0

from FH-3 to FH-1 with adding a small amount of SB into the EMBs, which reveals that only a small amount of synthetic brucite with high purity can effectively hinder the combustion of epoxy mortar binder. Similar results were also found in glass microspheres and magnesium hydroxide retarded ethylene–vinyl acetate composites [22]. 3.3. Rotational viscosity The polymer mortar has attracted much attention owing to its great resistance to the chemical aggressions, good adhesion with the aggregates compared to conventional construction materials, especially its fast hardening [23]. Therefore, the reaction rate of polymer mortar binder should be carefully controlled to ensure the operation time. The rotational viscosity of binders must be controlled lower than 3 Pa s for concrete compaction because the binders will become too hard to compact the pavement if the viscosity exceeds 3 Pa s [24]. The rotational viscosity-time curves of the neat EMB and brucite flame retarded-EMB composites at 60 °C are shown in Fig. 4a and b. Obviously, the rotational viscosity for EMB increases greatly with the increase of the brucite contents. For EMB, the reaction time to 2 Pa s is 84 min. The reaction time to 2 Pa s for the SB modified EMBs is around 58–82 min, a little faster than 61–82 min for the NB modified EMBs. It was reported that the reaction time to reach 2 Pa s for warm mix epoxy asphalt curing at 110 °C is 48 min, which is much shorter than that of brucite modified EMB composite [25]. Therefore, the viscosity of brucite modified EMB composite is low enough to satisfy the requirement of mortar pavement even at 60 °C.

Fig. 4. Rational viscosity-time curves for brucites modified EMBs at 60 °C: SB (a) and NB (b).

of the presence of fillers on the Tg of polymer matrix is related to the rigid phase reinforcement and crosslinking network of the thermosetting polymer matrix [27–29]. Unlike the halogen-free reactive flame retardant, DOPO [30], the addition of brucites has negligible influence on the crosslinking networks of epoxy resin.

3.4. Glass transition temperature 3.5. Thermal stability The DSC curves of the pure EMB and brucite modified EMBs are presented in the Fig. 5. It can be seen that the Tg of the neat EMB is about 24 °C. The addition of the two kinds of brucites has no significant effect on the Tgs of EMBs. However, results reported by others shows that the addition of 10 wt% Mg(OH)2 leads to a slight decrease of Tg value (4 °C) [26]. It is well known that the effects

The influence of brucites on the thermal stability of EMBs was evaluated by TG. Figs. 6 and 7 present the TG and DTG data of NB/EMB composites. It can be seen that in the 250–450 °C range, the neat EMB undergoes the degradation mainly as a single step with a maximum mass loss rate (T1max) at 397 °C, which attributed

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that the residues at 750 °C of brucite modified EMBs are higher than that of the neat one. These results indicate that the thermal stability of the neat EMBs is enhanced by the incorporation of brucites. 3.6. Mechanical properties Fig. 8 demonstrates the tensile properties of the neat EMB and brucites modified EMBs. It can be seen that the tensile strength of EMBs is improved with the addition of SB and a maximum value (10.8 MPa) with an increase by 15% at a loading of 20 wt%, on the other hand, the addition of NB slightly lowers tensile strength of the neat EMB. Similar result was also reported by others [26]. The improvement of tensile strength is probably ascribed to large interface contact areas and uniform dispersion of brucites in the EMB, which will be discussed hereafter. Generally, the tensile strength improvement is always along with a decrease of the elongation at break (toughness). The elongation at break of brucite modified EMBs decreases with the increase of brucite content. Moreover, the elongation at break of SB modified EMBs is higher than that of NB modified ones at the same brucite content since fracture of talc and other impurity in NB can occur in the filler instead of the interface or the polymer matrix [34]. It should note that the technical requirement of tensile strength and elongation at break for epoxy mortar binders is 8 MPa and 50%, respectively. Even with loading of 20 wt% SB, as shown in Fig. 8, the mechanical property of EMB also satisfies the technical requirement. Thus, the mechanical results indicate that the addition of 20 wt% SB is optimal to improve the mechanical properties of EMBs.

Fig. 5. DSC curves of brucite modified EMBs: SB (a) and NB (b).

to the epoxy network decomposition [31,32]. The thermal decomposition of SB modified EMBs occurs in two distinct stages. The first stage is characterized by the decomposition of the epoxy network. The second stage which basically ends at around 537 °C is ascribed to the pyrolysis of the brucite. For NB/EMB composites, the thermal profile is similar with the addition of 10 wt% SB, but an obvious displacement in T1max is observed as compared to that of the neat EBM. However, with more brucites, the thermal decomposition of EMBs divides into three stages, attributes to existence of brucite and dolomite. The initial decomposition temperature (IDT) and Tmax can be used to ascertain a material lifetime [33]. The IDT is assumed to the temperature of 5% mass loss for the sample. The IDTs, T1max, and residues at 750 °C of the NB/EMB composites are summarized in Table 5. The mechanism related to the flame retardancy of brucite is related to the endothermic decomposition of MH (DH = 1450 J/g), which occurs by formation of magnesium oxide and dehydroxylation in one step reaction.

MgðOHÞ ¼ MgO þ H2 O This endothermic reaction can not only lower the temperature near MH, but also prevent the decomposition of the polymer matrix. In Table 5, temperatures characteristic for the beginning of IDT of EMBs increase by 8–20 °C for upon brucite addition. This may be due to the high thermal stability of MH around 340 °C, and 30.9% water release of MH in vapor phase when the temperature is raised to 450 °C [26]. However, T1max decrease by 20–30 °C with the addition of brucites, which is consistent with dehydration of the bound water of the MH [18]. Table 5 also shows

Fig. 6. TG (a) and DTG (b) curves of SB modified EBMs.

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brucite and EMBs and homogeneous dispersion of brucite in the EMBs. For brucites with more impurities (NB), however, we can see a larger number of aggregations of particles in SEM (Fig. 9b, d and f). It is known that agglomeration tends to counteract the reinforcement of the filler. In this case, the addition of NB lowers mechanical properties of EMBs as discussed above. Also, the agglomeration of NBs weakens the flame retardancy of NBs in EMB composites.

4. Conclusions The effects of two kinds of brucites, synthetic and natural brucites on the flame retardancy, rotational viscosity, thermal, mechanical, and morphological properties of epoxy mortar binders were investigated. The addition of brucites, especially the synthetic brucite, significantly improves the fire properties of epoxy mortar binders. The addition of brucites increases the rotational viscosity of EMB, which indicates that brucites hinder cure reaction of the binders. However, the viscosity of brucite modified EMBs is low enough to satisfy the requirement of mortar pavement even at 60 °C. The presence of brucites enhances the thermal stability of the EMBs. The addition of the synthetic brucite enhances the tensile strength of EMBs, while the natural brucite slightly decreases the tensile strength of EMBs. The incorporation of brucites deceases the elongation at break of EMBs, while the elongation at break of EMB with synthetic brucite is higher than that of EMB with natural brucite. For both brucites modification, EMB with

Fig. 7. TG (a) and DTG (b) curves of NB modified EBMs.

3.7. Morphology The morphology of the brucite modified EMBs are represented by Fig. 9. As shown in Fig 9a, c and e, for SB, random dispersion of brucite particles within the polymeric matrix is observed in the SEM image. Furthermore, few agglomerations of brucite particles are seen in the EMBs. It can be observed that brucite particles are fully embedded by epoxy in the brucites/EMB composites. Good adhesion is formed between particle and polymer matrix since brucites particles were coated with a thin film of epoxy. It is well known that both epoxy and brucite contains a large amount of hydroxyl groups [35]. The interfacial interaction between the EMBs and brucite particles may be attributed to the formation of hydrogen bonds among hydroxyl groups. Therefore, the above-motioned improvement of tensile strength for SB/EMB composites is ascribed to the excellent interfacial bonding between

Table 5 TGA and DTG results for EMBs with different brucite contents. Sample

IDT (°C)

T1max (°C)

T2max (°C)

T3max (°C)

Residues at 750 °C (%)

Neat EMB 10 wt% SB 20 wt% SB 30 wt% SB 10 wt% NB 20 wt% NB 30 wt% NB

298 298 292 318 308

397 370 367 364 374

– 416 416 422 –

– – – – –

5.6 13.2 19.1 26.0 13.9

317

370

413

720

20.6

306

370

423

720

25.3

Fig. 8. Tensile strength (a) and elongation at break (b) of neat EMB and brucite modified EMBs.

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Fig. 9. SEM images of EMBs containing 10 wt%, 20 wt% and 30 wt% of SB (a, c, e) and the same contents of NB (b, d, f).

20 wt% synthetic brucite shows optimal results of flame retardancy and mechanical properties. Acknowledgement The financial support from a Project Funded by Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT), the Priority Academic Program Development of Jiangsu Higher Education Institutions and the Fundamental Research Funds for the Central Universities (20620140066) are gratefully acknowledged. References [1] Reis JML, Moreira DC, Nunes LCS, Sphaier LA. Evaluation of the fracture properties of polymer mortars reinforced with nanoparticles. Compos Struct 2011;93(11):3002–5. [2] Mostafizur R, Akhtarul I. Effect of epoxy resin on the intrinsic properties of masonry mortars. Iran Polym J 2012;21:621–9. [3] Zhang YG, Pan XY, Sun YF, Xu W, Pan YQ, Xie HF, et al. Flame retardancy, thermal, and mechanical properties of mixed flame retardant modified epoxy asphalt binders. Constr Build Mater 2014;68:62–7. [4] Li Y-J, Gu X-Y, Zhao J, Jiang P, Sun J, Wang T. Flame retardancy effects of phosphorus-containing compounds and cationic photoinitiators on photopolymerized cycloaliphatic epoxy resins. J Appl Polym Sci 2014;131(7):40011.

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Please cite this article in press as: Zhang Y et al. Brucite modified epoxy mortar binders: Flame retardancy, thermal and mechanical characterization. Constr Build Mater (2015), http://dx.doi.org/10.1016/j.conbuildmat.2015.05.037