Trong khi be tbng d mdc 500 trd len vdi ea 4 logi sgi thi cudng dg chju kdo khi uln cua BTCS thdp tdng cao, cho thiy be tbng mdc trung binh sir dgng sgi thep khbng hidu qua;.. Ty Id h[r]
Trang 1VAT LIEU - MOI T R l f O N G - KY T H U A l HA T A N G
ANH Hl/dNG CUA Cl/dNG DO BE TONG VA LOAI SOI THEP DEN HIEU QUA SI/ DUNG SOI THEP TRONG BE TONG COT SOI THEP
TS NGUYeN THANH BJNH
Vien KHCN Xay du-ng
KS NGUY6N HUYeN THI
Cong ty Co phan Thu-ong mai Thiet bj & San pham Cong nghiep (IPECO)
Tdm tit: Su- dung isgi thip trong be tdng (BTCS
thip) lim ting rd r$t khi ning chju kio udn cua be
tdng Tuy nhien viec sir dung sai thep hieu qui phu
thudc vio nhiiu yiu td, trong dd inh hwdng cw&ng dd
cua be tdng gdc (bi tdng khdng sai) vi ioai sai (ty li
hw6ng sai) din cwimg dd chiu kio khi udn cua be
tdng li rit Idn Bii bio gi&i thiiu inh hwdng cua
cirang dg be tdng vi lo^i sgi thip din cirang dd chju
kio khi udn cua be tdng trong gidi han mic 300 - 800,
nhim muc dich phit huy higu qui cua sgi thip khi
su-dung trong be tdng cdt sgi
1 Be tdng cdt sm thep va cac loai s v i nghien ciru
Be tbng eit sgi (BTCS) thep la be tbng eb sgi
thep phdn tdn trong thdnh phin, sgi thep rdi rgc
khbng lien tge Khi chju kdo BTCS thep ehl hu hdng
sau khi sgi thdp bj dO-t hoge bj tubt ra khdi da xi mdng
[6] Vide dua them sgi thdp vdo be tbng da cai thi$n mbt so tinh chat cua be tbng nhu [1, 3, 5, 6]: tdng cudng db chju uln; tdng db bin deo dai; tdng kha ndng chju va chgm m ^ h ; tdng kha ndng chju biin dang khi kdo uon; tdng kha ndng khdng nut khi chju tai trpng va cdc tinh chat khdc, trong dd rb rdt nhit la tdng cao cudng db chju kdo khi u l n tir 50-70%, thdm chi Idn han 100% [5, 6]
TO cde k i t qua nghien cuu [1, 2], ta chpn 4 loai sgi dien hinh cho 4 ty Id hudng sgi (chieu ddi/dudng kinh), ddc trung cho sgi thdp hidn cd tgi Vi$t Nam: sgi thep Crimped (sgi d$t lugn sdng, ddi 38mm va 52mm) vd sgi Dradmix (sgi trdn 2 d i u neo, ddi 30 va 35mm) cho trong bang 1 D l thiy rb anh hudng cua mdc bd tbng d i n hidu qua su dgng sgi thdp, chpn bd tbng gle eho be tbng cot sgi thdp vdi mdc 300, 500,
700 vd 800
*'^^.M^'^;.'!.e;ri^^
Sgi thep crimped do NYCON - My san xuit
hdlfatotnia Dramix
Sgi thep DFiAMIX do Hin Quoc san xuit
Hinh 1 Cic loai sgi thep sw dung trong nghiin ciru Bang 1 Thong so ky thuat cua sgi thep [1]
STT
1
2
3
4
5
6
7
Thong so ky thudt cua sgi thep Hinh dang, tiet dien ngang
ctja sgi
Chieu ddi sgi (mm)
Dudng kinh, dudng kinh
tuong duong (mm)
Ty Id hudng sgi
Tong dien tich be mgt, cm^/kg
S6 lugng sgi (sgi/kg)
Cudng db chju kdo (daN/cm^)
Loai sgi thep Det dai 38mm Det ddi 52mm
Sgi det tiet di#n hinh vdng cung
38 1,31
29
« 5.340 2.280
52 1,31 39,7
« 5.340 1.840
Trdn SF-35/0,7 (mm) TrdnSF-30/0,5 (mm) Sgi trdn SF tilt di$n hinh tron
35 0,7
50
« 6.616 8.600
30 0,5
60
a 8.978 19.040
>10.000
Trang 2Trong bang 1, dudng kinh tuang duang cua sgi
det dugc tinh theo tieu chuin ACI 544.1R 96 [3]: d =
f(D/SG) 1/2
Trong dd: d dudng kinh tuang duang, mm; f
-hd s i ehuyin doi, f = 0,0120; D db choi cua sgi,
gam; SG - khoi lugng rieng eua sgi thdp, g/cm^
Cbng thCpc [3]: dudng kinh tuang duang Id dudng
kinh mbt vbng trbn eb didn tich tuang duang vdi didn
tich tilt didn ngang cua sgi thdp; D6 choi eua sgi Id
khIi lugng tinh bdng gam cua 9000 mdt ddi cua mbt
sgi dan
2 Thdnh phdn d p phdi BTCS thep va be tong
khong sai ddi chupng
Vdt lidu ehl tgo gom:
Xi ming: PCB 40 Nghi San thoa man ede yeu
ciu ky thudt eua TCVN 6260 : 1997 Cudng db chju
ndn ciJa xi mdng d tuoi 28 ngdy dat 48,9 N/mm^
thLJ-theo TCVN 6015-95;
- Cit: Cdt sbng Lb phu hgp vdi TCVN 7570: 2006
Bd tbng mdc 300, mb dun db Idn ciia cdt Id 2,3; mdc
500 vd 700, mb dun d | Idn Id 2,72; mdc 800, mb dun
d | Idn Id 2,92;
Di dim: d^ax = 20mm, c i p phii hgt: d = 5
•=-10mm/d= 10 -=- 20mm la 45/55 Bd tbng mdc 300
dung dd vbi; be tbng mdc 500, 700 vd 800 dimg dd xanh (Hod Binh) Dd ddm phO hgp vdi TCVN 7570: 2006;
- Phu gia sieu dio: Phg gia sidu deo Glenium SP
51 cQa hang MBT- Degussa;
Phu gia khoing min: Tro triu nghiin mjn ddp
ung TCXDVN 311:2004 hodc ASTM C1240-00, chit dbn mjn la tro tuyIn Pha Lgi ddp li-ng theo ASTM C618-00;
- Nwdfc: dgt yeu c i u ky thudt TCXDVN 302: 2004; Sgi thip: dung 4 loai sgi vdi hinh dgng lugn
sbng vd trbn tran 2 diu neo, sgi thdp ddp ung ydu ciu ASTM A820-01 [4]
Thanh phin d p phii bd tbng nghidn cu-u eho trong bang 2, be tbng khbng sgi cb db sgt tiJ- 18-20
em vdi be tbng mac 300, 500 vd 700, db sgt 20-22cm vdi be tbng mac 800 Sgi thdp dung 50kg/m^ vdi 4 logi sgi, diiu chinh hdm lugng phg gia sieu deo d l db sgt eua hbn hgp BTCS thdp dat 16-18 cm, giu- nguyen
ty Id N/X Ky hipu trong bang 2 nhu sau: CP30, CP50, CP70 vd CP80 Id be tbng khbng sgi mdc 300, 500,
700 vd 800; A, B, C, D la BTCS thdp: vdi A Id sgi thdp
cb ty Id hudng sgi 29, B Id sgi thdp eb ty Id hudng sgi 39,7, C Id sgi thep ed ty Id hudng sgi 50 vd D Id sgi thdp ed ty Id hudng sgi 60
STT
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Bang 2 Thinh phin cip phoi bi tdng khong sgi va
Ky hieu
Be tong goc
mac 300
Be tong goc
mdc 500
Be tong goc
mdc 700
Be tong goc
mdc 800
Ky hi$u CP30 CP30A CP30B CP30C CP30D CP50 CP50A CP50B CP50C CP50D CP70 CP70A CP70B CP70C CP70D CP80 CP80A CP80B CP80C CP80D
Xi mang (kg)
310
310
310
310
310
380
380
380
380
380
480
480
480
480
480
580
580
580
580
580
Tro trIu (kg)
0
0
0
0
0 38,0 38,0 38,0 38,0 38,0 48,0 48,0 48,0 48,0 48,0 58,0 58,0 58,0 58,0 58,0
Tro bay (kg) 155,0 155,0 155,0 155,0 155,0 95,0 95,0 95,0 95.0 95,0 48,0 48,0 48,0 48,0 48,0
0
0
0
0
0
Sieu deo (lit) 0,78 0,84 0,88 0,93 0,93 2,2 3,23 3,23 3,23 3,23 3,0 3,36 3,48 3,48 3,48 6,67 6,67 6,67 6,67 6,67
BTCS thip mac 300, 500, 700 va 800
Cdt (kg)
761
753
753
761
761
761
752
752
752
752
743
736
735
735
735
644
637
637
644
644
Ba (kg)
941
931
931
941
941
969
958
958
958
958
947
937
937
937
937
976
966
966
976
976
Nude (lit) 183,0 183,0 183,0 183,0 183,0 172,0 172,0 172,0 172,0 172,0 171,5 171,5 171,5 171,5 171,5 170.5 170,5 170,5 170,5 170,5
Sgi thep (kg)
0
50
50
50
50
0
50
50
50
50
0
50
50
50
50
0
50
50
50
50
DO sgt (cm) 18,0 18,0 18,0 17,0 16,5 20,0 18.0 17.5 17.0
17 20.0 18.0 18,0 18,0 18,0 22,0 18,0 18,0 17,5 17,0
Trang 3VAT LIEU - MOI TRU'aNG - KY THUAT HA T A N G
D l thiy rb anh hudng cua mdc bd tbng vd logi sgi thdp d i n hidu qua su dgng sgi thdp nhim tdng cao cudng db chjg keo khi u l n eua be tbng, nghien cuu vdi be tbng mac 700 va 800 su dung 2 logi sgi thdp cd ty 1$ hudng sgi cao Id 50 vd 60 Thanh phin d p phbi BTCS thep eho trong bang 3
Bang 3 Thanh phin cip phoi BTCS thep mac 700 vi 800 sir dung sgi thep co ty 1$ hwang sgi cao
STT
1
2
3
4
5
6
7
8
9
10
Loai sgi
Sgi thep cd ty l#
hudng sgi 50
Sgi thep cd ty le
hudng sgi 60
Sgi thep cd ty le
hudng sgi 50
Sgi thep cd ty Id
hudng sgi 60
Ky hieu CP70C1 CP70C2 CP70D1 CP70D2 CP80C1 CP80C2 CP80C3 CP80D1 CP80D2 CP80D3
Xi mang (kg)
480
480
480
480
580
580
580
580
580
580
Tro trau (kg) 48,0 48,0 48,0 48,0 58,0 58,0 58.0 58.0 58,0 58,0
Tro bay (kg) 48,0 48,0 48,0 48,0
0
0
0
0
0
0
Sieu deo (lit) 4,32 5,28 4,32 5,28 6,67 7,25 8,12 6,67 7,25 8,12
Cat (kg)
731
726
731
726
634
630
625
634
630
625
Oa (kg)
931
925
931
925
961
955
949
961
955
949
Nude (lit) 171,5 171,5 171,5 171,5 170,5 170,5 170,5 170,5 170,5 170,5
Sgi thep (kg)
75
100
75
100
75
100
125
75
100
125
Bpsyt (cm) 17,0 17,0 17,0 17,0 17,5 16,0
15 16,5 15,0 14,5
3 Anh hydng mac be tong va loai s?i thep den cu'dng do chju keo khi uon cua BTCS thep
Kit qua eho trong bang 4, anh hudng cua mdc be tbng vd ty Id hudng sgi trdn do thj hinh 2
Bang 4 Cwang dg chiu uon cua be tong khong sgi vi BTCS thep a tuoi 28 ngay
BTCS thep va be tong (BT) khong sgi mac 300, 500, 700 vd 800 STT
1
2
3
4
5
6
7
8
9
10
Ky hieu
CP30
CP30A
CP30B
CP30C
CP30D
CP50
CP50A
CP50B
CP50C
CP50D
Ruin,
daN/cm^
54,3 64,5 64,0 68,0 70,0 74,7 88,5 99,2 111,2 120,0
Muc tang so vdi BT khong sgi daN/cm'^
— 10,2 9,7 13,7 15,7
— 13,8 24,5 36,5 45,3
%
— 18,8 17,8 25,2 28,9
— 18,5 32,6 48,8 60,6
STT
11
12
13
14
15
16
17
18
19
20
Ky hieu CP70 CP70A CP70B CP70C CP70D CP80 CP80A CP80B CP80C CP80D
Ru6n,
daN/cm^
91,0 107,5 119,0 130,5 139,0
103 121,5 134,0 145,0 156,0
Muc tang so vdi BT khong sgi daN/cm''
— 16,5 28,0 39,5 48,0
— 18,5 31,0 42,0 53,0
% _
18,1 30,8 41,7 52,7
17,9 30,0 40,7 51,4
CO
i
CQ
CO
'3
<o
o
170
I n
•a
•2 150
130
.= 110
I
.2 90
u
70
50
—•—E
—•—E
- A - E
—•—E
• " 2 9
W"^'
ITCS thdp md ITCS thdp md ITCS thdp md ITCS thdp md
Jtr"^
^^.A<J97
jm^^
0 300 c500 c700
^„^m
^,^ 60
_ — • 6 0
1
60
50
>o
I 40
t 30
i 20
i 10
t 1
• BTCS thep mac 300
• BTCS thep mac 500
A BTCS thep mac 700
—•— BTCS thep mac 800
• ^ 9
* 60
> ^ 6 0
^_ • S O
T9 le hudng s0i cua S0l thep
65
35 45 55 T^ le hirdng sdi cOa sdi thep
a Cwang dg chju keo khi udn cua BTCS thep b Mirc tang cwang dg chju keo khi udn cua BTCS thip
tudi 28 ngay so vai BT gdc khong sgi tudi 28 ngiy Hinh 2 Anh hwdng cua mic BT va ty lg hwang sgi thep din cwang dg keo udn cua BTCS thip & tudi 28 ngiy (sgi 50 kg/m)
Trang 4S i lidu trong bang 4 vd do thj hinh 2 cho thiy
ring, su dgng sgi thdp vdi hdm lugng sgi 50 kg/m^
dd Idm tdng ddng k l cudng db chju kdo khi uln eua
be tbng Muc tdng cudng db chju kdo khi uln eua
BTCS thdp so vdi be tbng gle khbng sgi phu thubc
vdo mdc bd tbng vd ty Id hudng sgi eua sgi thdp:
Vdi cung mbt logi sgi (eung ty Id hudng sgi),
cung hdm lugng sgi thi be tbng mdc cdng cao cang
Idm tdng cudng db chju kdo khi uln eua BTCS thdp
tO-c Id tdng hidu qua su dgng sgi thdp;
- Be tbng mdc trung binh (trong nghien cuu dung
bd tbng mdc 300) thi mO-e tdng cudng db chju kdo khi
uln cQa BTCS thdp Id khbng nhiiu vdi ca 4 loai sgi
Trong khi be tbng d mdc 500 trd len vdi ea 4 logi sgi thi cudng dg chju kdo khi uln cua BTCS thdp tdng cao, cho thiy be tbng mdc trung binh sir dgng sgi thep khbng hidu qua;
Ty Id hudng sgi tdng Idm tdng cudng db chju uon eua BTCS thdp; d i i vdi cdc logi sgi cb ty Id hudng sgi cao mirc tdng cudng db chju uon cua BTCS thep so vdi be tbng khbng sgi Id rit Idn Hay
nbi each khac, sir dgng sgi thdp eb ty Id hudng sgi
cao hidu qua han sgi thdp cd ty Id hudng sgi thip
S l lidu thi nghidm be tbng mdc 700 vd 800 vdi sgi thep cd ty Id hudng sgi cao d ede hdm lugng khdc nhau eho trong bang 5 vd cudng db chju kdo khi uln cua BTCS thep duge bilu didn trdn do thj hinh 3
Lo^i sgi
BT khdng
sgi
Sgi tron
SF-35/0,7 (mm),
ty If hudng
sgi 50
Sgi trdn
SF-30/0,5
(mm), ty le
hudng sgi
60
Bang 5 Cwang dg chju udn cua be tong khong sgi va BTCS thep
Be tdng mac 700
Ky hieu CP70 CP70C CP70C1 CP70C2
— CP70D CP70D1 CP70D2
—
Ham lugng sgi
0
50
75
100
—
50
75
100
—
Ruin,
daN/cm^
91,0 130,5 146,5 154,5
— 139,0 155,5 164,2
—
Muc tang so vdi
BT khong sgi daN/cm"^
39,5 55,5 63,5
— 48,0 64,5 73,2
—
%
41,7 61,0 70,0
— 52,7 70,8 80,4
a tuoi 28 ngay
Be tdng mac 800
Ky hieu CP80 CP80C CP80C1 CP82C2 CP83C3 CP80D CP80D1 CP80D2 CP80D3
Ham lugng sgi
0
50
75
100
125
50
75
100
125
Ru6n,
daN/cm^
103 145,0 164,0 174,2 183,1 156,0 173,0 184,4 195,5
Muc tang so vdi
BT khong sgi daN/cm''
42,0 61,0 71,2 80,1 53,0 70,0 81,4 92,5
%
40,7 59,2 69,1 77,8 51,4 70,0 79,0 89,8
fi-ts 80
60
40
' BT mdc 700 ty' le hUdng sai 50
• BT mdc 700 t^ le hUdng s 0 i 60
• BT mdc 8001^ le hUdng sdi 50
• BT mac 800 t^ le hUdng siJl 60
25 50 75
Ham iUdng scrl thep, kg/m^
100
Hinh 3 Cwang d0 chju kio khi uon cua BTCS thep
125
Kit qua trong bing 5 vd do thj bilu didn tren hinh
3, v l dnh hudng cua be tbng mdc cao su dgng sgi
thdp cb ty Id hudng sgi cao d i n cudng db chju kdo
khi uln eua bd tbng dd cho thiy:
Vdi cung mbt logi sgi, eung hdm lugng sgi thi bd tbng gle mdc cdng cao muc tdng cudng db chju kdo khi uln eua BTCS thdp cdng Idn;
- Hdm lugng sgi tdng thi cudng db chju kdo khi uln eua BTCS thdp tdng;
Trang 5VAT LIEU - MOI TRU'aNG - KY THUAT HA T A N G
Ty Id hudng sgi cdng cao thi mipc tdng cudng db
chiu kdo khi uln eua BTCS thep cdng Idn;
- Be tbng mac cao su dgng sgi thdp eb ty Id hudng
sgi cao Idm tdng rit cao cudng do chju kdo khi ubn
cua BTCS thdp Cd t h i tgo ra duge BTCS thdp ed
cudng db chju kdo khi uon tir 100-195 daN/cm^
Til- kit qua nghien cu-u cung cho thiy eb t h i tgo
ra BTCS thep eb cudng db chju kdo khi uon 100
daN/em^ vdi bd tbng mac 500 vd d i n 195 daN/cm^
vdi be tbng mdc 800
Kit qua trdn duge giai thich bdi kha nang lien kit tgi
b l mdt tiip xuc giua be tbng vd sgi thdp [6], eg t h i la:
Be tbng mac cao cb chit lugng ho xi mdng tit,
Idm tdng kha nang lien k i t tgi b l mdt tiip xuc giu-a
sgi thep vd da xi mdng, d i n tdi tang kha ndng chju
keo cho be tbng T, phdt huy hidu qua cua sgi thep su
dgng;
Sgi thep eb ty Id hudng sgi cao (tilt dien sgi
manh vd so lugng sgi Idn) cb tong didn tich b l mdt
tiip xuc eua sgi Idn han sgi thdp cd ty Id hudng sgi
thip vdi eung khoi lugng hodc eung dan vj t h i tich
(trong bang 1: sgi ty Id hudng sgi 29,7 cd tong didn
tich b l mdt Id 5.340 em^/kg; sgi ty Id hudng sgi 60 cd
tong didn tich b l mat 8.978 em^/kg);
Be tbng mdc cao sir dgng sgi thep eb ty Id
hudng sgi cao Idm tdng cao cudng db chju kdo khi
uln eua BTCS thdp chinh Id do chit lugng lien k i t tai
b l mdt tiip xuc tot kit hgp vdi tong didn tich b l mdt
tiep xuc cao, tiJ- dd tong luc lien k i t Idn;
Bd tdng mdc cao cb hdm lugng xi mang vd hdm
lugng bbt mjn cao, ngodi vide Idm tdng kha ndng lien
kit tgi b l mdt tiip xuc giu-a sgi thdp vd dd xi mdng,
ma cdn tgo diiu kidn phdn tan tot sgi thdp cd ty Id
hudng sgi cao vdi hdm lugng sgi cao d i n tdi tang rat
cao cudng do chju keo khi uon cua BTCS thep
4 K i t luan
* Mac be tbng cb anh hudng Idn den hi$u qua su
dgng sgi thdp trong be tbng, eg t h i :
Be tbng mac trung binh (mdc 300) su- dgng sgi
thdp khbng hidu qua Khi su dgng sgi thdp vdi mgc
dich Idm tdng cudng db chju kdo khi uon cua be tbng
thi su dgng be tbng mdc Or 400-500 (40-50 MPa) trd
len;
Be tong mac cang cao thi cdng Idm tdng cudng
db chju kdo khi uon cua BTCS thdp khi sO dgng ciing mbt loai sgi, ciing hdm lugng sgi tuc Id tdng hidu qua
su dung sgi thdp
* Sgi thdp Idm tdng cao cudng d | chju uon eua be tbng, muc db tdng cudng db chju uon cua bd tbng khi
su dgng sgi thdp phg thuOc vdo nhieu y i u to, trong dd
ty Id hudng sgi Id yeu to rit quan trpng:
Ty Id hudng sgi tdng thi cudng db chju uln cua
BTCS thdp tdng Su dgng sgi thdp cb ty Id hudng sg\
cao hidu qua han sgi cb ty Id hudng sgi thip;
Chenh ldeh v l mO-c tdng cudng dO chju kdo khi uln khi dung sgi thdp cb ty Id hudng sgi cao vd khi dung sgi thdp cd ty Id hudng sgi thap (d cdc hdm lugng khdc nhau) Id r i t Idn
* Bd tbng mac cao eho phdp phdt huy cao hi$u qua ciia sgi thdp, khi dd dong thdi eho phdp su dgng eac loai sgi thdp cd ty Id hudng sgi cao, Idm tdng manh cudng dp chju kdo khi u l n cua BTCS thdp
* Be tbng mac cao sir dgng cdc logi sgi thdp cd ty
Id hudng sgi cao vdi hdm lugng sgi hgp ly cao Idm tang rit cao cudng db chju kdo khi uln eua BTCS thep Mu-e db tdng cudng d | chju kdo khi uln cua be tbng khi sO dgng sgi thdp cd t h i tdi 89,8% Cb the tao
ra BTCS thdp dgt cudng db chiu kdo khi uon tiJ-100-195daN/cm^
TAI LIEU THAM KHAO
1 NGUYEN THANH BINH. Nghien cuu che tgo be tong cot sgi thep cudng dp chju uon cao trong dieu ki$n
Viet Nam Luan in TSKT, Vign KHCN Xay dung, Ha Ngi, 155 trang, 2007
2. TRAN BA V I ^ T , N G U Y £ N THANH BINH vd cdc dv Nghien cuu chi tgo be tong chit lugng cao su- dgng cot sgi nhdn tgo dung cho cac cdng trinh d Ha NOi- ^
tai ma sd TC-DT/5-04-03, 494 trang, 2008
3 ACI 544.1 R-96, State-of-the-Art Report on Fitjer
Reinforced Concrete, 66p
4 ASTM A820-01, Standard Specification for Steel Fibers for Fiber-Reinforced Concrete
5 RILLEM, Fouth Intemational Workshop on High Performance Fiber Reinforced Cement Composites
(HPFRCC4), Edited by A.E Naaman and H.W Reinhatdt, June, 2003, 546 pp
6 PERUMALSAMY N BALAGURU and SURENDRA P.SHAH Fiber- Reinforced Cement Composites
Intemational Edition 1992, 529 pp
Ngiy nh$n bai: 8/8/2011