CHẤT KẾT DÍNH MANHÊZI PHỐTPHÁT ỨNG DỤNG LÀM VẬT LIỆU CHO CÁC GIẢI PHÁP CHỐNG CHÁY BỊ ĐỘNG.pdf

8/10/2019 CHT KT DNH MANHZI PHTPHT NG DNG LM VT LIU CHO CC GII PHP CHNG CHY B NG.pdf

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VT LIU XY DNG -MI TRNG

Tp ch KHCN Xy dng - s 3/201430

CHT KT DNH MANHZI PHTPHT NG DNG LM VT LIU CHOCC GII PHP CHNG CHYB NG

KS.NGUYN PHC VINH, KS.NGUYN HONG,KS.NGUYN THANH NHN, TS.NGUYN KHNH SN

i hc Bch khoa Tp. H Ch Minh (HCMUT)

Tm tt:Nghin cu ny tp trung nh gi ng

dng cht kt dnh manhzi phtpht (MPB) lm vt

liu ngn chy, chng chy b ng trong cc h

thng ca ngn chy (fire door), bo v (fireshield) kt

cu chu lc b-tng, thp, ng gen k thut. Thnh

phn cu to gm khong kt tinh ngm nc kiu K-

struvite, biu hin tnh chu lc, bn v nhit nphn

ng cao. Thnh phn pha phn tn gm cc cht n

tro bay, ct, si thy tinh b sung tng hp snphm compzt. Kt qu biu hin truyn nhit vi

mu panel 150x150x30mm theo thi gian cho thy

tnh bn-n nh nhit cng nh kh nng cch nhit

nhit cao qua b dy 30mm p ng tiu ch vt

liu chng chy TCVN 9311-1-2012. Mc tiu ng

dng gii php chng chy b ng cho cc cng trnh

xy dng, giao thng c th c d kin.

T kho: Cht kt dnh manhzi phtpht, chng

chy b ng, nhit n chuyn pha, truyn nhit, ISO

834.

1. Gii thiu v c ch phn ng dnh kt

Thng k trn th gii v nc ta u cho thy

cc v chy ln xy ra trong cc cng trnh nh cao

tng, trung tm thng mi, cng nghip hay cc

hm ngm giao thng, xe li nhng hu qu

khng khip. Kim sot, khng ch hiu qu m

chy cng nh duy tr cng trnh bn vng khi chy l

nhng yu cu chnh trong thit k gii php phng

chy cha chy [1]. Cc loi vt liu bin hin nhitn chuyn pha ln nh thch cao, silict canxium

ang c dng ph bin cu to cc b phn ca

ngn chy (fire door), lp bo v cch nhit chy

(fireshield) cho kt cu chu lc b-tng, thp hay bc

bo v cch nhit chy ng gen k thut thng gi,

thot khi, cp in. Nhc im ca chng l tnh n

nh nhit khng cao, cng nh c th b ph hy

nhit trn 12000C. Vt liu manhzi ni chung, vn

c s dng trong cc ng dng chu la l cng

nghip nhit rt cao, c th xem xt ng dngtrong xy dng nu p ng cc tiu ch kinh t k

thut.

Cht kt dnh hay xi-mng manhzi phtpht

(MPB) c xp vo nhm vt liu kiu ceramic vi

cc dng lin kt ho hc. Tnh dnh kt ca MPB

c hnh thnh nh tri qua qu trnh phn ng kt

ta mui trong dung dch nc dng nho trn. Qu

trnh ny c nt tng ng vi giai on ng rn

nhit thng to sn phm ca va xi-mng

Poclng (XMP), nhng hnh thnh cu trc tinh th

th li tng t nh nhng vt liu ceramic [2]. Ttrc n nay, nhng ng dng thc t ca loi vt

liu kt dnh ny vn cn b hn ch trong lnh vc vt

liu xy dng, nguyn nhn l do gi thnh nguyn

liu sn xut cao v c nhng c th iu kin ng

rn ca cht kt dnh [3]. Theo l thuyt, MPB nh

hnh trong dung dch phn ng axt-baz gia MgO

v mui axt phtphoric (mn hir phtpht HPO42-,

ihir phtpht H2PO4-). Cc xut ca nhiu tc

gi trong [4] cho thy cch nh gi khc nhau v c

ch phn ng ng rn MPB. Theo cng b gn yca Soude & Pra [5], tc gi ngh chia phn ng

theo 2 giai on khc nhau. u tin s din ra qu

trnh ho tan phn ly ion H+trong dung mi nc ca

mui axt phtphoric (pH


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Tp ch KHCN Xy dng - s 3/2014 31

MgOH++ 2H2O Mg(OH)2+ H3O+ (5)

Mg(OH)2 Mg2++ 2OH- (6)

Mg2++ 6H2O Mg(H2O)62+ (7)

nh gi qu trnh phn ng kt hp gia ion sau

, Abdelrazig v cng s, [6] ch ra trn kt quchp ph XRD cc pc ni bt l sn phm tinh th

kt tinh nc gm 6 phn t nh struvite

(MgNH4PO4.6H2O) hay K-struvite (MgKPO4.6H2O) ty

theo gc mui s dng. Nhn chung y khng hn l

sn phm kt tinh duy nht m l sn phm bn nht

trong s h cc sn phm phc schertelite, dittmarite,

newberyite, phosphorroesslerite, hayesite,... km bn.

Phn ng kt hp din ra theo m hnh nh trn hnh

1. Cc tinh th sn phm u tin xut hin trn b

bao ngoi cc ht MgO v tip tc pht trin theo

hng t ngoi vo trong li ht. Do , khi hintng ng rn bt u din ra hn hp mt tnh linh

ng, cc lin kt, vi cu trc hnh thnh ng thi

lp bao sn phm v cng cng lm hn ch qu

trnh tan, phn ly ion OH- ca thnh phn manhzi

cha phn ng trong li [7].

Hnh 1.M hnhphn ng kt hp trong dung dch gia cc ion Mg(H2O)62+

, K+, PO4

3-

Trong phn tip theo ca bi vit, chng ti s tp

trung vo kho st sn phm cht kt dnh MPB v

cc pha phn tn trong khai thc tnh cch nhit

chng chy cng trnh xy dng. Cc biu hin ng

x trong iu kin nhit caoca m chy c th

th nghim m phng trng hp tip xc gradient

nhit ln t l nung. Cc bn lun trn kt qu th

nghim ny s c trnh by cng vi cc xutng dng sn phm compzt ch to.

2. Nguyn l iu s dng v thc nghim

Vic la chn thnh phn cc cht n khc

nhau, mt mt th nghim nhit l nhit cao, mt

khc gp phn quan trng lm gim gi thnh sn

phm khi ng dng.

2.1 Nguyn l iu

Bt manhzi loi cng nghip dng ph bin trongngnh sn xut gm s, vt liu chu la c chng

ti s dng nh thnh phn baz trong cc th

nghim sau y. Sn phm MgO cng nghip ny thu

c khi nung qu mui ccbnt manh. Kt qu

phn tch XRF (XEPOS-SPECTRO) cho c lng

thnh phn xt manh ch yu chim 85,7% theo

khi lng. Mt s pha khong chnh manhzi, bruxt,

lmt c pht hin trn ph chp XRD (AXS D8

Advance, cc CuK). Thnh phn bruxt, lmt tn

ti nh sn phm phn ng vi mi trng bo qunhay cc tp cht khng loi b ht khi sn xut quy

m cng nghip. Vi hm lng MgO ch yu, cng

nh mn cao (di sng 90m) ca bt manhzi

d on kh nng hot tnh phn ng tt. Theo l

thuyt, mc hot tnh ho hc ca phn ng baz

MgO vi axt ph thuc ng thi vo kch thc ht

v cc khuyt tt trn b mt, do h qu ca cc gia

cng nghin sng [7].

Mt loi mui axt phtphoric l kali ihir

phtpht KH2PO4 98% (KDP) c chng ti s dng

nh thnh phn nguyn liu axt. Trong mui KDP c

cha cc nguyn t K, P vi lng cho t, cy trng

nn thng gi chung l phn m. ho tan ca

mui phtpht r rng cao hn nhiu so vi bt

manhzi, ph thuc vo nhit v dung mi s

dng. Thm vo , theo Soude & Pera [5] qu trnh

tan, phn ly ra ion H+ca mui axt phtphoric s gip

ko theo qu trnh tan trong dung dch ca MgO m

bo a mi trng tr li trung tnh, iu ny kh

ph bin trong trng hp phn ng axt baz.

Theo nghin cu ca Hall v cng s [8], vai tr

ca ph gia lm chm ln qu trnh phn ng axit-

baz l to trn b mt ht nguyn liu baz MgO

mt lp mng ngn nc ngn chn qu trnh phn ly

ion OH-. duy tr kh nng thi cng, khun cht

kt dnh MPB, rt cn thit kim sot phn ng ng

rn nhanh v tnh to nhit ln ban u. Mui borax

hay natri borat Na2B4O710H2O, c s dng nh

ph gia lm chm, l loi ho cht dng trong phngth nghim vi tinh khit 99,9%. Theo kt qu quan

st cu trc sn phm ca Abdelrazig v cng s [6],

K++ Mg(H2O)62++ PO4

3-MgKPO4.6H2O (K-struvite)

2MgOH++ K++ 2HPO42-2MgKPO4.H2O (dittmarite)

Mg(OH)2 + HPO42- + H2OMgHPO4.3H2O (newberyite)


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s dng hm lng borax dng gy nh hng n

qu trnh kt tinh tinh th, to cc pha v nh hnh,

kch thc nh. Theo kt qu kho st, lng ph gia

2,5% s dng cho php nho trn d dng cng nh

kim sot tt phn ng.

Ngoi ra, nh cp trn y cc pha phn tn

gm si thy tinh, tro bay v ct xy dng c

nghin cu s dng ch to sn phm compzt vi

cht kt dnh MPB. S kt hp thm cc cht n

c ghi nhn vai tr gia tng tnh n nh nhit, hn

ch co nt c th xy ra khi vt l iu chu tc tng

nhit ln [9]. Tro bay loi C (FA) vi thnh phn 26%

CaO, 43% SiO2 c ngun gc nhit in C Mau,

dng lm ph gia khong cho sn xut xi-mng. Ct

xy dng (CS) sngng Nai, mun ln 2,3 p

ng theo tiu chun Vit Nam ct liu mn sn xut

b-tng. Si thy tinh (GF) loi EGlass dng ri l

sn phm thng mi s dng trong sn xut

compzt nn nha. Hm lng dng kho st s b

da theo cc tiu ch l cng chu lc v kh

nng to hnh khun. y ch gii hn cc kho

st vi tng loi ct liu mt lm pha phn tn vi

cht kt dnh nn.

2.2 Cp phi v quy trnh ch to

Cn lu rng t l phn ng l thuyt gia hai

thnh phn KDP/MgO l 1/1 theo mol hay 3,3/1 theo

khi lng. y cng l t l cc chtphn ng ph

hp kho st ch to cht kt dnh nn MPB. Phn

ng din ra vi tc rt nhanh, ta nhit rt mnh

v dung dch h kt ta ng rn ngay sau . S

quy trnh phi trn cc bc kht tri qua 2 giai

on nh sau: mui KDP v bt MgO c phi trn

kh cng nhau v nghin s b trong ci nghin hnh

tinh nhm ng nht ha, tip theo c t t

vo trong nc ho tan sn borax 2,5% kt hp

khuy lin tc. Nc ng vai tr dung mi ha tan,to tnh cng tc cho hn hp va ng thi l thnh

phn nguyn liu phn ng ng rn. y, t l

nc/cht rn c hiu chnh ln cn vi t l l

thuyt phn ng 5/1 theo mol hay 0,56 theo khi

lng. Cc thnh phn cht n c thm vo

cui giai on nho trn phn tn trong h.

Bng 1.Thnh phn phi liu ch to va MPB v h compzt

Cht rn (CR) Pha phn tn (theo % CR)K hiu mu

MgO KDP

Nc/

CR

Borax(theo %

CR) Si thy tinh Tro bay Ct

MPB (i chng) 3,3 1 0,56 2,5 - - -MPB-GF 3,3 1 0,56 2,5 0,5-0,75-1 - -MPB-FA 3,3 1 0,56 2,5 - 20-30-40 -MPB-CS 3,3 1 0,56 2,5 - - 100-150-200

Chng ti lit k 4 loi cp phi cc thnh phn

nguyn liu trong bng 1, bao gm MPB; MPB-FA (b

sung thnh phn tro bay); MPB-CS (b sung thnh

phn ct) v MPB-GF (b sung thnh phn si thy

tinh). Lu thi gian phi trn thu c hn hp

c tnh ng nht l rt khc nhau gia cc loi chtn, cng nh gia cc t l cht n. Ct biu hin

tnh phn tn cao sau khong 5 pht nho trn, tro

bay th c tnh ht nc v ch phn tn sau khong

10 pht nho trn.i vi si thy tinh, vic phn tn

vo nn kt dnh rt kh khn vi si di, vi si ct

ngn 20 mm thi gian nho trn khong 8 pht. Hm

lng cht n cng cao th cng kh phn tn v

phi kim sot cn thn trnh b ng cc. Hai loi

mu c ch to gm dng thanh 40x40x160 (mm)

tng t nh vi trng hp va XMP (TCVN 6016-

1995) o cng chu lc un/nn cho tt c

cp phi, v dng tm panel vung, dy 30 mm i

vi cc mu c tnh chu lc cao o tnh cch

nhit. Sau khi khun to thanh hoc tm panen,

quan st thy hin tng ta nhit v ng rn sau

. Thi gian k t khi mu ng rn hon ton n

khi tho khun l khong 60 pht. Tip theo, cc mu

c lu, phi kh t nhin nhit phng vgim st cn khi lng hng ngy kim chng.

2.2. Th nghim truyn nhit qua b dy tm panel

Vt liu ng dng cch nhit chng chy b ng

cho cng trnh cn thit phi tho mn cc tiu ch c

bn gm tnh khng chy, tnh cch nhit, tnh ton

vn v tnh chu lc trong mt s trng hp. Vt liu

ngun gc khong v c nh cht kt dnh MPB v

cht n p ng mt cch t nhin tnh khng bt

la cng nh khng tham gia qu trnh chy. ng xbiu hin kh nng cch nhit chy (n 12000C) cn

thit phi kim chng qua cc th nghim kim nh


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c thc hin trong cc trung tm kim nh quy

m kch thc v iu kin gn thc t c chun

ha [10]. nghin cu, chng ti pht trin h thng

thit b cho php th nghim truyn nhit mt phng

nhm nh gi tnh cch nhit chy, dng ngun nhit

m phng ta ra t l nung in tr trong phng. Bphn ca ng kn l khi gia nhit chnh l tm

panel th nghim (hnh 2). Kch thc tm panel vt

liu c c nh l 150x150x30 (mm), trong chiu

dy 30mm chnh l qung ng nhit truyn qua t

trong l ra ngoi khng kh. T l mu ch to chiu

dy/cnh ngang = 1/5, c th xem m bo b dy

nh hn nhiu so vi cnh ngang, nn cho php b

qua nhng chnh lch nhit trn cng mt phng

ngang v ch tp trung chnh lch nhit theo chiu

dy, tc truyn nhit 1 phng (1D).Tng cng c 7

cp nhit in (loi K v S) c b tr trong th

nghim, ni vi h thng ghi nhn tn hiu tn sut 1

giy 1 ln. Hai cp nhit in S1S2c t trong

lng l v ngay v tr ca l tip xc vi mt trong mu

tm panel ghi nhn nhit l nung v nhit

mt trong tip xc nhit l (mt nng). Nmcp nhitin K1K5c t ngay trn mt ngoi mu tm

panel ghi nhn nhit trung bnh mt tip xc vi

khng kh (mt lnh). B iu khin l thit lp

chng trnh nng nhit da theo gi tr im

(nhit vs. thi gian) ca ng quan h nhit

thi gian tiu chun (ISO 834, phng trnh

T(t)=T0+345.log(8t+1) vi t tnh bng pht [11]). Theo

nguyn l b tr ny th tm panel vt liu th nghim

s lm chm qu trnh truyn nhit chy ISO 834 t

trong l ra ngoi qua b dy 30mm.

Hnh 2.H thng l in tr gia nhit, cu to ca l bng tm panel (tri); h thng cp nhit inb tr trn mt trong v ngoi mu (phi)

3. Kt qu v bn lun

Mt c im chung ca cht kt dnh manhzi

phtpht l tnh ng rn nhanh, sn phm ng rn

c chc, nng v c cng cao. y cc kt

qu thc nghim trnh by ch yu tp trung vo s

kt hp ca cht kt dnh vi pha phn tn, vai tr

nh hng cng nh i chiu vi nn MPB i

chng.

3.1. Kt qu kho st c trng c l

3.1.1 Pht trin vi cu trc

Tt c cc mu va MPB v mu compzt u

biu hin ng rn pht trin cng khi bo

dng. Quan st mt gy sn phm bng mt

thng (hnh 3) cho thy dng c chc nh t

nhin. Ct liu phn tn tt trn nn kt dnh, ng

thi xut hin cc bt kh.

Hnh 3.nh chp mt gy mu 40x40x160 (mm) cht kt dnh MPB v compzt

Quan st cho thy trn hnh 4a cc tinh th K-

struvite dng tm th trn cc nh chp knh hin vi in

t qut (SEM) mu MPB.iu ny chng t qu trnh

phn ng kt tinh tinh th sn phm tt. Cng cn tn

Ct liu ct

Mu MPB-CS 100%

Si thy tinh

Mu MPB-GF 0,75%

Bt kh

Tro bay vn cc

Mu MPB-FA 20%

40

40

Mu MPB

L nung cng sut 4kW

Ca l nung Cp nhit

Mu panel 150x150x30mm

Tnhiu

Mt ngoi(lnh)

Mt trong(nng)

Cpnhit

K1-K5

CpnhitS2


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ti cc cht khng phn ng (ht sng mu MgO) trn

b mt tm sn phm chnh. Vng phng i (x1300) b

mt ca tinh th rt u n, c chc. S dng ph gia

lm chm mui borax gip phn ng trong dung dch c

kim sot, kt qu thu c phn ln cc tinh th sn

phm trng thi kt tinh, ng ngha cng chulc cao. Trn nh SEM ca cc mu compzt (hnh

4c,d) d dng nhn thy hnh nh tng t ca cc tinh

th sn phm xen ln cc du vt ca tro bay, ct liu

ct v c bt kh b cun vo trong khi nho trn. Vi

mu c si thy tinh th vng chp qu b nn khng

quan st thy si (hnh 4b). Nhng, c cc vt nt kh

ln, ko di trn nh chp c th l gii nguyn nhn khi

un nn ph v mu vi s hin din ca ct si lmcho mu c tnh dai, thi gian chu lc ko di v cc

ph hoi (do p lc) lan truyn rng khp.

Hnh 4.nh chp knh hin vi in t qut (SEM)ca cc mu cht kt dnh MPB v mu compzt

3.1.2 Cng chu nn, un

i vi mu va MPB, kt qu cng chu unv chu nn trung bnh (bng 2) ch c chnh lch nh

gia thi im 1 v 3 ngy tui. Mu chun cht kt

dnh biu hin kh nng chu lc kh cao so vi va

xi-mng thng thng, RTBnn=24,63 MPa v

RTBun=1,02 MPa, ng thi lgc vi tnh c chc

khi quan st nh chp (hnh 3, 4). S dng ph gia

mui borax cho php duy tr trng thi h m boqu trnh phn ng din ra trc khi ton khi va b

ng rn, cc v tr nguyn liu cha phn ng t quan

st thy. iu ny cng ng ngha vi vic ch cc

tinh th sn phm pht trin trong thnh phn kt

dnh.

Bng 2.Cng chu nn, un trung bnh 1, 3 ngy tui trn mu thanh 40x40x160 (mm)

RTBChu un(MPa) RTB

Chu nn(MPa)K hiu mu1 ngy 3 ngy 1 ngy 3 ngy

MPB (i chng) 0,95 1,02 22,26 24,63

0,5% 1,0 1,09 19,91 20,390,75% 1,11 1,14 22,11 23,94MPB-GF

1% 0,89 1,17 20,99 23,8320% 0,92 1,04 26,24 27,3130% 0,70 0,72 16,89 18,97MPB-FA40% 0,48 0,66 14,02 16,57

100% 0,51 0,61 19,20 19,21150% 0,64 0,55 18,78 18,75MPB-CS200% 0,40 0,42 15,27 18,70

Trong khi , vi mu compzt, c s khc bit

nht nh cng chu lc 1 v 3 ngy tui cng

nh cc cp phi cht n (bng 2). Khi s dngct thay th nguyn liu to cht kt dnh th ng

thi c kt qu cng chu nn v chu un u

gim so vi mu i chng. Mu MPB-FA cho kt

qu cng chu nn, un tt nht, tng ng l

27,31 MPa v 1,04 MPa nu m bo phi trn ngnht phn tro bay thay th cho nguyn liu to cht

kt dnh. Cc ht mn tro bay phn tn cho php thu

(a) MPB: x100 v x1300

L rngVt nt

(b) MPB-GF: x100 v x1300

(c) MPB-FA: x100 v x1300

Tro bayTro bay

K-StruviteK-Struvite

L rng

(d) MPB-CS: x500 v x1000

Ct


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c vi cu trc sn phm vi c chc cao hn,

nhng cng kh nho trn, khun do vn cc (hnh

3). i vi mu ct kh nng nho trn tt nh cc

ht ct ng vai tr nh nhng vin bi gip ch xt

nh tan cc cc bt nguyn liu. Nhng kch thc

ht ln th lin kt vi tinh th dng tm K-struvitekhng tt dn n gim cng . Si thy tinh

thng c tnh ha tan trong mi trng kim ca

va xi-mng, nhng trong mi trng trung tnh ca

cht kt dnh axit-baz nh MPB th khc [12]. Kt

qu cng chu un ca mu MPB-GF c ci

thin khi dng si thy tinh l minh chng. Nhng,

cng tng t nh hai loi cht n dng ht, vic

phn tn si thy tinh vo nn kt dnh cng gp kh

khn, mu rt d b ng cc nu khng nh ti

mnh bng cnh khuy.

3.2. Kt qu kho st ng x nh it cao

3.2.1 H s dn nhit

Kt qu o h s dn nhit trn cc mu tm

panel t trong iu kin nhit phng n nh250C. Thit b o Quick Thermal Conductivity Meter(QTM-500) ng dng nguyn l o nhanh trng thikhng n nh vi phng php Hot-wire. Gi tr trungbnh (bng 3) ly t5 ln o 5 v tr khc nhau trnmt 150x150 (mm) ca tm mu panel. Trong khi 2trng hp s dng tro bay v si thy tinh khngcho thy thay i ng k gi tr h s dn nhit svi mu i chng th mu ct 100% li cho thy hin

tng tng t ngt gi tr h s dn nhit hn 2 lnmu i chng. Mu cha ct cch nhit km hn vcn thit nhng lu xem qu trnh truyn nhit

qua mu ny.

Bng 3.Gi tr o h s dn nhit cc tm panel MPB v compzt

K hiu mu MPB MPB-GF MPB-FA MPB-CS

(W/m.K) 250C 0,8778 0,9943 0,8758 2,1339

3.2.2 Qu trnh truyn nhit nhit cao (12000C)

Biu bin thin nhit theo thi gian i vi

mu panel i chng MPB (hnh 5) ch r c s khc

bit nht nh bin thin nhit lng l () ving biu din nhit l thuyt ISO 834 (). Khc

bit ln nht ch yu tp trung vo giai on ban u

khi gia nhit l vi qun tnh do khng gian cng nh

c im nng nhit ca in tr dy, nhng t

khong 2 gi tr i th chnh lch l khng nhiu v

nhit l duy tr 12000C tng ng vi nhit l

thuyt. So snh nhit trong lng l vi nhit ca

mt trong ca tm panel MPB (mt nng) cng c s

chnh lch gia hai ng bin thin nhit ti mi

thi im trong sut qu trnh th nghim. Nguyn

nhn ca hin tng ny ch yu do s khng ng

nht trong ton b khng gian, cng nh tn tht

nhit ti cc v tr bin. Sau 2 gi nng nhit th nhit

ti hai v tr ny ln lt ghi nhn bi cp nhit

in loi S l 1200 v 10200C. ng biu din bin

thin nhit trung bnh theo thi gian trn mt

ngoi ca tm panel MPB (mt ngui) c xut hin

mt thm ng nhit (t thi im 0 gi 30 pht n 2

gi 50 pht), trn nhit dao ng tng ln rt t.

Gi tr nhit ghi nhn bi 5 cp nhit in loi K b

tr tiy cng rt thng nht. Sau 6 gi th nghimtruyn nhit, khi nhit mt nng (S2) l 10200C

th nhit trung bnh trn mt ngui (cch ly bi

30mm b dy mu) l khong 1200C. Kt qu ny r

rng chng t vt liu MPB biu hin kh nng

cch nhit, lm chm qu trnh truyn nhit ra. So vi

yu cu tnh cch nhit ca cc b phn ngn chy

cho cc dng cu kin chu lc, gi tr nhit gia

tng trung bnh mi im o trnmt khng tip xc

vi la khng c vt qu gii hn cho php,

thng l 1400C v khng c im no >1800C, th

kt qu ny ha hn ng dng c. Lp bo v tnh

chu la cho cu kin chu lc b - tng hay bc bo

v cch nhit cho cc b phn cng trnh m bo

cng trnh vn hnh an ton v mt k thut trong

khong thi gian di qu trnh chy xy ra, cng nh

tit kim sa cha nhanh chng a vo vn hnh li

sau chy.


7/10



Hnh 5.Kt qu sau hn 6 gi th nghim truyn nhit l 12000C qua mu tm panel MPB 150x150x30 (mm)

Hnh 6.Kt qu sau hn 6 gi th nghim truyn nhit l 12000Cqua mu tm panel MPB-GF 0,75% (si thy tinh) 150x150x30 (mm)

T hnh 6 n hnh 8 ln lt l kt qu bin thin

nhit theo thi gian i vi mu panel MPB-FA (20%

tro bay), MPB-CS (100% ct), MPB-FA (0,75% si thy

tinh), tin hnh th nghim tng t trong vng 6 gi nh

mu i chng trn y. Trong ba trng hp, biu

kt qu trn hnh 6 (mu c si thy tinh) v hnh 7 (mu

c tro bay) cho thy tnh tng ng. Nhit trung bnh

o ti mt ngui dao ng ln lt trong khong 123-

1340Ci vi mu c tro bay v trong khong 111-1410C

i vi mu c si thy tinh. ng thi thm ng nhit

ko di khong gn 120 pht cho c hai trng hp, t

thi im 0 gi 30 pht n 2 gi 30 pht.

Hnh 7.Kt qu sau hn 6 gi th nghim truyn nhit l 12000Cqua mu tm panel MPB-FA 20% (tro bay) 150x150x30 (mm)

Tm MPB-FA: trc (tri) vsau (phi) th nghim

12000C

Nhit (0C)

M lnh

M nng

2 gi

ng ISO 834

Nh l nung

tgian(gi)

Tm MPB-GF: trc (tri) vsau (phi) th nghim

12000C

Nhit (0C)

Mt lnh

Mt nng

2 gi

ng ISO 834

Nhit l nung

tgian (gi)

Tm MPB: trc (tri) v sau(phi) th nghim 12000C

Nhit (0C)

Mt lnh

Mt nng

2 gi

ng ISO 834

Nhit l nung

tgian (gi)


8/10



i vi mu c ct, nhit trung bnh o ti mt

ngui bin ng ln hn trong khong 131-1880C,

ng thi thm ng nhit ch ko di khong 70 pht

t thi im 0 gi 20 pht n 1 gi 30 pht. Nh vy

iu chng t kh nng cch nhit chy ca mu c

ct l km hn so vi hai trng hp tro bay v sithy tinh, ng thi cng km hn so vi mu i

chng ch c cht kt dnh MPB. Tnh cch nhit km

ca mu c ct th hin hon ton lgc vi kt qu h

s dn nhit vt tri trn bng 3. Cng b dy 30 mm

tm panel, nu xem xt kh nng ng x cch nhit

ca cc mu ng vi cc thi im 2 gi v 4 gi th

nghim th mu MPB-GF cch nhit nhit cao tt

nht, theo sau ln lt bi mu MPB (i chng),

MPB-FA v MPB-CS. Nu xt v thi gian ko di

thm ng nhit, vn ng vai tr quyt nh trong viclm chm s tng ln ca nhit trn mt ngui mu

panel, th mu i chng MPB l di nht khong 140

pht. Chng ti s quay tr li vn ny khi phn tch

thnh phn sau khi tri qua th nghim truyn nhit.

Hnh 8.Kt qu sau hn 6 gi th nghim truyn nhit l 12000C qua mu tm panel MPB-CS 100% (ct) 150x150x30 (mm)

3.2.3 Tnh bin dng v n nh nhit

ng thi trn hnh 5n hnh 8cng ch r nh

chp tiu biu cc mu tm panel trc v sau th

nghim truyn nhit trong vng 6 gi. Cng lu vi

s lng th nghim cho tng trng hp l 3 tm.

C th thy trn cc nh chp h hi, vt nt xut

hin trn cc mt trong, mt ngoi v c trn b dy

cc mu so vi trc khi th nghim. Nhng nu xt

v trng thi th tt c cc tm panel u cha b phhy hon ton sau 6 gi tip xc nhit cao trong

cc i ln n 12000C. iu chng t tnh n

nh hnh dng trong iu kin th nghim vi

gradient nhit ln l tng i tt. S xut hin v

pht trin m rng ng thi ko di ca cc vt nt

l biu hin u tin ca mt n nh nhit hay bin

dng nhit ln gy ni ng sut ph hoi. B sung

thnh phn cht n khc nhau c tc dng iu

chnh qu trnh ny, c th mu c si thy tinh v ct

cho thy s lng, m rng v quy m ni chung

ca cc vt nt l t hn so vi mu i chng v c

tro bay.iu ny ng cho c mt nng ln mt ngui

mu panel, si thy tinh v ct gip m bo tnhton vn ca mu trong iu kin chy. Mu c tro

bay biu hin tnh c chc ln, cng chu lc

cao, song c hn ch l b nt v ph hoi v mt n

nh nhit hn.

Tm MPB-CS: trc (tri) vsau (phi) th nghim

12000C

Nhit (0C)

M lnh

M nng

2 gi

ng ISO 834

Nhi l nung

tgian (gi)


9/10



Hnh 9.nh chp SEM ca mu MPB ti v tr mt nng (a) v mt ngui (b), sau khi th nghim truyn nhit nhit l

Kt qu tin hnh phn tch nh chp vi cu trc

vt liu ly t hai v tr ln cn vi mt nng v mt

ngui. Di tip xc trc tip vi nhit cao lin tc

trong vng 6 gi, vt liu cht kt dnh MPB s b

chuyn trng thi v ph hy. Hnh 9a cho thy iu

ny, c th nhn thy dng vi cu trc v nh hnh,

kch thc nh, gy gn [13] ca chnh cc pha thnh

phn dehydrt KMgPO4. Cc l rng kch thc ln

cng xut hin nhiu gia cc nt gy. Trong khi ,trn hnh 9b cho thy mt s khc bit ti v tr mt

ngui so vi mt nng. Trn nh chp vn c cc l

rng v b mt b lm phng, kch thc ht b. Tuy

nhin, c chc cao hn hn v tng quan hn

so vi nh chp vi cu trc sn phm MPB trn hnh

4a (x100).iu c ngha rng vt l iu MPB mt

ngui din ra phn ng hidrt ha mt phn.

Phn tch thnh phn khong lm sng t iu ny

vi cc nhca khong K-struvite cn hin din. Nh

vy c th ni cng vi qu trnh truyn nhit 1phng qua 30mm b dy tm panel l s dch

chuyn ca mt gii hn chuyn pha (front of phase

transition) t mt nng n mt ngui. Phn ng thu

nhit ( hidrt ha v ha hi nc) ca qu trnh

ny lm nn thm ng nhit ko di nh cp trn

y. Gi tr nhit n hay nhit hp th trn mt n v

khi lng MPB c c lng trn kt qu phn

tch nhit vi sai khong 910 J/g [14]. ng thi s

chuyn pha thnh phn khong cng l nguyn nhn

ca bin dng nhit v mt n nh, cn thit cht n

nh si thy tinh tng tnh n nh th tch. Vic

mu tm panel MPB cha b sp hon ton sau 6

gi th nghim cng c th gii thch t qu trnh phn

ng cha hon ton kt thc.

4. Kt lun

Cht kt dnh manhzi phtpht c tng

hp trong nghin cu ny t nguyn liu bt baz

MgO, mui c tnh axt KDP, nc v ph gia lm

chm phn ng mui borax 2,5%. Ko di thi gian

phi trn v khuy ng nht cc thnh phn nguynliu m bo cho qu trnh phn ng to sn phm

kt tinh cao K-struvite (ngm 6 phn t nc) v dnh

kt ng rn. Sn phm compzt c th c ch

to t s dng cc pha phn tn dng si, bt hay

ht ct l iu kt hp vi nn cht kt dnh MPB. Theo

tiu ch tnh cht c l cao v kh nng thi cng to

hnh, ba loisn phm c trnh by gm MPB-

GF 0,75% (dng si thy tinh), MPB-FA 20% (dng

tro bay loi C), MPB-CS 150% (dng ct sng). Tro

bay gip ci thin tnh chu nn, si thy tinh gip cithin tnh chu ko v ct gip ci thin tnh lu ng

va to hnh khi ln. i vi ng x cch nhit

chy vi nhit ln n 12000C, m phng t l

in tr trong phng th nghim, cc mu tm panel

150 x 150 x 30 (mm) cho thy kh nng cch nhit v

n nh theo thi gianng lu . C th nhit o

c mt ngoi cch ly qua 30mm b dy mt

trong tip xc nhit cao ch xp x 100-1200C sau 4

gi vi mu MPB, MPB-GF, MPB-FA v xp x 1500C

vi mu MPB-CS. Lu so vi tiu chun yu cutnh cch nhit (nhit gia tng trung bnh mi im

nh hn 1400C v khng c im no >1800C), th

(b) MPB : x100 v x500

KMgPO4

L rng

L rng

KMgPO4

Fly ash

(a) MPB : x100 v x500

KMgPO4

L rng

KMgPO4

L rng


10/10



30mm b dy vt liu c th p ng lm lp bo

v tnh chu la cho cu kin chu lc b-tng lm

vic an ton. Thm ng nhit ko di t 70-140 pht

ty theo loi pha phn tn ng vai tr quyt nh lm

chm qu trnh tng nhit trung bnh trn mt

ngoi ca 30 mm b dy. Tnh n nh nhit ckim chng qua th nghim truyn nhit lin tc trong

6 gi, cc mu tm panel b nt nhng khng b ph

hy, c bit trong trng hp c dng si thy tinh

gia cng. Vi kh nng cch nhit m bo lm vic

nhit 12000C th nghim nh trn, hon ton c

kh nng m rng quy m th nghim trn cc kch

thc, b dy khc nhau, trn cc mi trng lm

vic m cng nh so snh i chng vi cc loi vt

liu sn phm thng mi thch cao, silict canxium

nhm ng dng thc t trong cc b phn chngchy b ng cng trnh.

Li cm n: Cc tc gi cm n ti tr kinh phnghin cu ( ti NCKH, nm 2012) t NipponSheet Glass Foundation for Material Science andEngineering (Nht Bn).

TI LIU THAM KHO

1 LONG PHAN, Best pratice guidelines for strutural fire

resistance design of concrete and steel buildings, Hi

tho tiu chun VN-HK trong thng mi v thit k

PCCC cho nh v cng trnh,H Ni, 9/9/2009.

2 WAGH ARUN S., Chemically bonded phosphate

ceramics: Twenty-First Century Materials with Diverse

Applications; ELSEVIER 2004 ISBN: 0-08-044505-5.

3 LI Z., DING Z., ZHANG Y., Development of sustainable

cementitious materials, Proceedings of the

International Workshop on Sustainable Development

and Concrete Technology Ed. Kejin Wang, Beijing,

China May 2021, 2004, pp55-76.

4 ABDELRAZIG B.E.I., SHARP J.H., SIDDY P.A., EL-JAZAIRI B. Chemical reactions in magnesia-phosphate

cement. Proceedings of the British Ceramic Society

35, pp.141-154 (1984).

5 SOUDE E., PRA J., Mechanism of setting reaction

in magnesia-phosphate cements, Cement and

Concrete Research 30, pp.315321(2000).

6 ABDELRAZIG B.E.I., SHARP J.H. and EI-JAZAIRI

B.,The chemical composition of mortars made from

magnesia phosphate cement, Cement and Concrete

Research18 (3), pp.415-425 (1988).

7 SOUDE E., PRA J., Influence of magnesia surface

on the setting time of magnesia phosphate cement,

Cement and Concrete Research, Vol. 32, N01, pp. 153-

157(5) (2002).

8 HALL D.A., STEVENS R. and EL-JAZAIRI B., "The

effect of retarders on the microstructure and

mechanical properties of magnesia phosphate cement

(MPC) mortar", Cement and Concrete Research, Vol.

31, pp.455-465 (2001).

9 FEJEAN J., LANOS C., MELINGE Y., BAUX

C.,Behavior of fire proofing materials containing

gypsum, modifications induced by incorporation of inert

fillers. Trans IchemE, vol. 81, Part A- Chemical

Engineering Research and Design, pp.1230-1236,

(2003).

10 TCVN 9311-1 : 2012 Th nghim chu la - Cc b

phn cng trnh xy dng - Phn 1 - Yu cu chung.

11 ISO 834-INTERNATIONAL STANDARD, Fire-

resistance tests Elements of building construction,

Ed. 1999.

12 PERA J., AMBROISE J., Fiber-reinforced Magnesia

Phosphate Cement Composite for Rapid Repair,

Cement and Concrete Composites, vol.20, Iss.1,

pp.3139 (1998).

13 ABDELRAZIG B.E.I., SHARP J.H., Phase changes on

heating ammonium magnesium phosphate hydrates.

Thermochimica Acta 129(2),pp.197-215 (1988).

14 KHANH-SON NGUYEN, PHUOC-VINH NGUYEN,

HOANG NGUYEN, THANH-NHAN NGUYEN, THAI-

HOA NGUYEN, Use of phosphate magnesium material

in fire protection of concrete, Proceeding of The 5th

ACF Conference, 24-26 October 2012, Pattaya,

Thailand, pp.1-6.

Ngy nhn bi sa: 2/9/2014.

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