Chuong 6 VuaXD

7/30/2019 Chuong 6 VuaXD

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Bi ging VtLiu Xy Dng

CHNG 6 VA XY DNG

6.1. KHI NIM V PHN LOI

6.1.1. Khi nim

Va xy dng l vt liu nhn to khng nung, c thnh phn gm cht ktdnh, dung mi, ct liu v ph gia; c nho trn theo mt t l nht nh rirn chc li m thnh.

Va XD c cng dng chnh l xy v trt.

6.1.2. Phn loi

Theo loi cht kt dnh: va vi, va ximng, va thch cao, va t st vva hn hp.

Theo loi khi lng th tch:+ Va nh: l va c v1500 kg/cm3

+ Va nng: l va c v=18002200 kg/cm3

Theo cng dng: va xy, va trt v va c bit.

6.1.3. c im chung ca va xy dng

Do cng dng ch yu xy v trt cng trnh nn va lun b dn mng vkhng dng ct liu ln v vy:+ Cng va thp.+ Lng dng cht kt dnh cao.+ D b mt nc do nn ht hoc bay hi.+ Yu cu tnh do cao.+ Va c tc dng chnh l bo v v trang tr cng trnh.

6.2. VT LIU CH TO VA XY DNG

6.2.1. Cht kt dnh

Cht kt dnh v c thng l ximng pooclng theo tiu chun Vit Nam hocquc t, l thnh phn chnh to ra cng v m bo tnh gi nc chova.+ Dng c hu ht tt c cc loi cht kt dnh v c.

+ Chn cc loi cht kt dnh phi m bo cho va c cng v nnh trong iu kin c th s dng cng trnh.+ Cht kt dnh phi tho mn cc yu cu k thut nh nc quy nh.

Trong trng hp cn chng thm, sa chnh kt cu btng ct thp c th dngcc loi cht kt dnh polime hoc ximng polime.

GVC.Ths Trng Th Kim Xun - 1 -


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6.2.2. Ct liu

L thnh phn to b xng cng ca va, thng l ct thch anh, ngoi racn c tc dng lm gim co th tch v tng sn lng va.

Yu cu:+ Ch s dng ct liu nh (Dmax


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6.3. CC TNH CHT CH YU CA VA XY DNG

6.3.1. do ca hn hp va

do hp l ca hn hp va phi tho mn cc yu cu sau:

Hnh 1.1. Dng c th do ca va

+ D dn mng ng u: khng lng qu, kh qu+ Bm chc vo nn ngay khi cho va vo+ Phi gi c nc, khng nn ht hoc bay hi nhanh.

Phng php xc nh+ Dng cm su vo va ca 1 qu chu hnh nn bng kim loi c gc

chp 300, nng 300g+ cm su ca chu vo va, OK (cm) l gi tr biu din do ca va;

OK cng ln th do ca va cng ln.

6.3.2. Tnh gi nc

Hnh 1.1. Dng c xc nh phn tng ca va.

L kh nng gi khng cho nc trong va b ht mt bi nn hoc bay hi m bo va nc cho qu trnh thu ho, rn chc bnh thng.

nh gi kh nng gi nc dng khi nim phn tng v c xcnh bng 2 phng php:



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+ Phng php lng: Va trn xong th ngay do, c OK1; sau va tnh nh 30pht ri gt b 2/3 va lp trn v em trn u lp div xc nh do OK2. Khi phn tng PT = OK1 - OK2 (cm)

+ Phng php chn ng: Va trn xong cho vo bnh hnh tr rng, t ln

bn rung trong 30 giy ri trt 2 tht 1, 2 ra ly va tht 1 v 3 xc nh do c OK1, OK3. Khi phn tng PT = OK1- OK3 (cm3)

Bin php ci thin tnh gi nc ca va:+ Dng ph gia tng do, gim nc+ Tng cht kt dnh+ Ti nc vo nn v gch trc khi xy trt.

6.3.3. Tnh chng thm

Va trt ngoi cng trnh cn phi chu p lc chng thm Phng php xc nh: ch to mu va dy 2cm, sau cho mu va chu

p lc nc bt u l >>>> h24at2h3at5,1h2at1h1at5,0 mu khng b

thm th mu va t tnh chng thm. chng thm ca va k hiu W2, W4, W6, W8

6.3.4. Cng ca va

1. Cng chu nn ca va

Xc nh cng chu nn bng cch p cc mu va, c nh gi bng s

hiu mc va.

Mc va l cng gii hn chu nn ca mu va hnh lp phng vi kchthc cnh 7,07cm hoc hnh dm 4x4x16cm, c trn nn xp v cdng h 28 ngy trong iu kin tiu chun.

Cng ca va ph thuc vo nhiu yu t: cng cht kt dnh, lngdng cht kt dnh, t l N/X, ph gia ...

a. Cng ca va ximng, va hn hp ximng vi trn nn c (khnght nc) c xc nh theo cng thc N.A. Popov:

=4,025,0

X

NRR

Xv (1.1)

Trong :

+ Rv cng va sau 28 ngy rn chc;+ RX mc ximng xc nh theo phng php cng.+ X lng dng ximng cho 1m3 ct vng, kg;



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+ N lng nc dng cho 1m3 va, lt.

b. Cng ca va trn nn xp (ht nc):

( ) 405,01 +=

XRKRXv (1.1)

Trong :

+ Rv mc va; kG/cm2.+ RX mc ximng.+ X lng dng ximng cho 1m3 ct vng, kg;+ K1 h s tu thuc vo ct liu v phng php xc nh mc ximng.

Bng b.2. H s K1

K1 RX xc nh theo phngphp cng

RX xc nh theo phngphp mm

Ct ht ln 1 2,2Ct ht trung bnh 0,8 1,8Ct ht nh 0,5-0,7 1,4

Va xyvva hon thinuphi thomnyu cuvkhnngchu lc nhquynhtrongbng6-4.

Bng b.3. Yu cu v kh nng chu lc ca vaMcva

Gii hnbnnntrungbnhnhnht, kG/cm

2Gii hn bn nn trung bnh

lnnht, kG/cm2

410255075

100150200300

410255075100150200300

924497499

149199299

-

Gii hn bn chu nn ca va c th bng cch nn v cc mu vahnh lpphngkch thc 7,07x7,07x7,07 cm hoc cc na mudmsaukhichuun.



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Xcnhbngccmu lpphngc kchthc7,07x7,07x7,07cm.

Khihnhpva c lungnhhn4 cm,muc c trongkhun thpc y, cn nu hn hp va c lu ng ln hn 4 cm th mu c c

trongkhunthpkhngcy.

Saukhi tohnhmuc bodngnhsau:

Vi va dng cht kt dnh l xi mng cc mu c trong khun mi

trngmcm trnmt mutrn90%vnhit 27 20C thi gian t24

n48gi ri thokhun.Saukhi thokhun cc muc boqun thm 3

ngy trongmi trngmcm trnmt mu trn90%,nhit 27 2oC.

Thi giancn li chon lc th muva c bodng trongkhngkh

nhit 27 20

C v m t nhin i vi va xy trong mi trng kh,cni vi va xytrongmi trngm th va c ngmtrongnc.

Vi va cdngcht kt dnhrntrongkhngkh cc muc trong khun

mi trng phng th nghim c nhit 27 2oC thi gian 72 gi ri tho

khun. Sau khi tho khun cc mu c bo dng trong mi trng

khngkhnhit 27 2oC vm t nhin.

Sau khi bo dng s ngy quy nh cc mu va c em nn. Kt qu

ca php thc tnhbng trungbnh cng gi tr ca 3hoc 5vinmu th.Sai skt qu ca tngvin mu vi gi tr trung bnh khngc vt qu

15%vi mu tohnhvdngh trongphng th nghimvkhngvt qu 20% vi cc mu ch to ti cng trng. Nu 2 trong 3 hoc 3 trong 5 vinmuth khngt yu cu th phi tinhnhthc hin li.

Xcnhbngccnamudmsau khichuun:

xc nh cngchunn ca va ngi ta cngc thsdng cc namudmsaukhichuun,mudmckchthc 160x40x40.

chuyngii hnbnchunn ca va xc nhbng cch thna mu dmsang gii hn bn chu nn xc nh bng cc mu lp phng cng iu kinch to vbo dngnhnhau th nhnvi hs 0,8cho cc muva mcdi 100.Vi va mc t100 tr ln th gii hnbnnn ca cc muna dmngbnggii hnbnnn ca cc mu lpphng.



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6.4. VA XY V VA TRT

6.5. Va xy

Va xy c tc dng lin kt v truyn lc t vin gch hay ny xung vingch hay khc trong kt cu xy. Nu mch va khng y khi xy khngchc d b ph hoi v un.

Cc loi va xy cn c do tt. do ny thay i tu theo loi kt cu xy,phng php m chc, iu kin thi tit khi thi cng v loi nn.

6.6. Va trt

Va trt c tc dng bo v cho lp ct xy v lm cho kt cu xy vung vn,bng phng, lm tng v p cho cng trnh, v vy va trt c cc c tnh sau:

Va thng trt lm 3 lp mng:+ Lp d b trt u tin dy 3 8mm cn m bo cho va dnh vo ct xy

sau va cn do v phi mit mch.+ Lp m trt th hai: c tc dng lm cho kt cu xy bng phng. Lp ny

c km do km hn lp d b.+ Lp trang hong ngoi cng dy 2mm, lm cho b mt trt nhn, mn.

Va trt cn nho hn v cn c kh nng gi nc tt v tip xc vi ct xynhiu cho nn b ct xy ht v nc d bay hi vo mi trng.

Lng cht kt dnh va trt cao hn va xy. Trong mi trng kh ro dng

va vi rt tt.


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Chuong 6 VuaXD