Winter construction

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Winter construction

Naslund, B.

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N~ITIOITAL RES l';,":RCH COUiTO

IL

O? C!i;J~1i31i Technical Tra,lalat ion

TT-583

T i t l e : :,'?inter construction, ( ~ i n t e r b y g g e )

.

Author: B e r t i l ~:slundx~.

Bef erence: S t a t e n s s om mi t

te'

f6r

Byggnadsforsirilillr;, Stockholm, B r o s c l w

5,

1952,

32

p.

Trarlslator : 13, A. G. Nathan, T r a n s l s t ions Section,

N. B.

C. Li'irary.

Trans)-ated with pernlission.

$<:'The maauscri2t was prepared with the a s s i s t a n c e of Karin Stenslznd Junker.

PREFACE

The problems coimected with b u i l d i n g during winter r~ionths have been a concern of t h e Division of Building Research

s i n c e i t s b e g i n n i n ~ f , This phase of b u i l d i n g researcil i s one t h a t Canada has i n comr~on with o t h e r c o u n t r i e s , notably the Sccmdiiiavian countries, l:lucPi can be learned frail t h e i r e:iperi- ence,

I t i s hoped t h a t t h e t r a n s l a t i o n of t h i s a r t i c l e on i.rinter c o n s t r u c t i o n p r a c t i c e s i n Sneden w i l l b e of help t o those i n Canada concerned with t h i s problem.

The Division of Building Research a i s h e s t o thank 21r. H,A.G, Nathan f o r t r a n s l a t i n g t h i s a r t i c l e ,

Ottawa,

Rovelxber 1955, Robert

P,

Lezget, Director.

1 2 T T 2 0 . D U C ~ T I ~

An i d l e b u i l d i n g t r a d e during t h e winter was fori,lerly talcen f o r granted and considered a n a t u r a l event e v e r y ~ r l ~ e r e , The e n t i r e b u i l d i n g a c t i v i t y and thus t h e building-raaterial i n d u s t r y cane t o a s t a n d s t i l l a f t e r October 1st.

There has been a s t e a d i l y growing t r e n d to~vards b u i l d i n g a c t i v i t y the year rouncl f o r a number of' reasons. A s

i n other key i n d u s t r i e s , laboul- a i t h i n t h e b u i l d i n g t r a d e has become i n c r e a s i n g l y specialized. During the winter the construc- t i o n li~orl;er today has no longer t h e same p o s s i b i l i t i e s of

switching over t o another occupation where he n i g h t a s s e r t him- s e l f i n comnpetition. Since numerous mechanical a i d s a r e now a v a i l a b l e t o the c o n t r a c t o r a t t h e b u i l d i n g s i t e ,

i t

i s only i ~ a t u r a l t h a t he should be i n t e r e s t e d i n u t i l i z i n g them econo~xi- c a l l y and t h u s avoid u ~ p r o d u c t i v e i d l e periods. On t h e o t l a e ~ hand, the s i t u a t i o n on the labour market during the p a s t decade imde

i t

e s s e n t i a l t o u t i l i z e a l l t h e a v a i l a b l e labour the yen? round, Last b u t not l e a s t , s t a t e c o n t r o l of' t h e b u i l d i n g

a c t i v i t y was enacted i n order t o spread v;orlc over the ~vhols year by specifying times a t which c o n s t r a c t i o n i s t o s t a r t , thus

counteracting any unequal burden on the labour market*, Building a c t i v i t y during t h e v i n t e r no longer en- s m n - t e r s t e c h n i c a l d i f f i c u l t i e s which cannot be overcome by

'g1'Iihat winter stoppage means:

For t h e c o n s t r u c t i o n worker

-

seasonal unernpl~yr~~ent. For the c o n t r a c t o r

-

unproductive expenses f o r

machinery and admini- s t r a t i o n ,

For the property owner

-

l o s s of' r e n t , which eventu- a l l y w i l l a f f e c t the olnount o f r e n t paid by the tenant.

present-day resources, a p a r t frorn c e r t a i n types of c o n s t r u c t i o n work which should not be c a r r i e d out i n !*?inter, i , e , , e x t e r i o r p l n s t e r i n g , e x t e r i o r p a i n t i n g , e x t e r i o r paving, l e v e l l i n g and landscaping. Hovrever, these types of .~orlc may be suspended without any g r e a t i n t e r r u p t i o n of the time-table u n t i l t h e we:ather becornes more favourable and may then be c a r r i e d out a t

the b e s t s u i t a b l e moment, i r r e s p e c t i v e of the o t h e r c o n s t r u c t i o n work,

Above a l l , three f a c t o r s , i . e . , cold weather, snow and darkness, d e c i s i v e l y a f f e c t winter construction.

The

manner i n which these f a c t o r s a s s e r t t h e m s e l ~ e s i s explained i n g r e a t e r d e t a i l under the heading ltWinter wea t h e r conditions i n S7dvedenlt, I n order t o counteract these f a c t o r s a nunber of d i f f e r e n t

measures must be taken, Hoiirever, i t should be remembered t h a t s p e c i a l measures a r e c o s t l y , e s p e c i a l l y i n a b u i l d i n g under con- s t r u c t i o n . The problem f a c i n g the c o n t r a c t o r when he wants fc

maintain b u i l d i n g a c t i v i t y the year round i s a s follows,

The c o s t s f o r winter measures should be balanced i n such a way t h a t they leave a margin of prof i t f o r the b u i l d e r and take i n t o account the p u b l i c i r i t e r e s t a s well. These measures, lvlyilich a r e of a long-tern n a t u r e , Eire intended t o

spread the b u i l d i n g a c t i v i t y more evenly, c ~ ~ r e s p o n d i n ~ ; t o the l e v e l of occupation i n other industr:!es*.

A study of the records i s being made i n Sweden t 2

determine the e x t r a c o s t of winter construction. This study i s

:xSessonal unemployment means :

A burden on the labour market, unernployriient insurance b e n e f i t s o r compulsory r e t r a i n i n g f o r another occupation during the

Buildiw the y e s r round means:

A more permanent labour f o r c e , econo~nic and s o c i a l s e c u r i t y ; the demand on the building-materi a1 i n d u s t r y and t r a n s p o r t - a t i o n c o q ~ a n i e s i s more evenly d i s t r i b u t e d ,

xxde p o s s i b l e by a g r a n t from the S t a t e n s ~ o i n m i t t g

f 8 r

Bjrzgnads- forslcning ( 2 t a t e Colnnittee f o r Building Researcli) and i s being conducted by the author. This a n a l y s i s i s based on i n v e c t i - g a t i o n s during the years 1943-52. I t i s intended t o e s t a b l i s h , n i t h the a i d of t h i s r e s e a r c h r e p o r t , a schedule based on

d i f f e r e n t d a t a obtained from a study of a r e 2 r e s e i l t a t i v e s e l e c t i o n o f buildings. Furthernore, i t i s a l s o intended t o detep:.iine t h e econornic e f f e c t of such schedules and f i x e d times f o p s t a r t i n g c o n s t r u c t i o n work on the b u i l d i w c o s t s f o r d i f f e r e n t tyges of houses.

I n order t o determine the ex9ense i m ~ o s e d by winter on year round b u i l d i n g a c t i v i t y , t h e f a c t t h a t vreatlier conditions rnay be t h e cause of a d d i t i o n a l c o s t s d u r i a g a l l the f o u r seasons must be taken i n t o account, On the o t h e r hand, c e r t s i n t y - e s of work may be f a c i l i t a t e d by winter weather conditions, i n any

case compared with conditions b r o ~ h t a'uout by r a i n , e t c . , during t h e f a l l .

The p r e s e n t boolclet d e a l s i n t h e f i r s t p l a c e v i t h measures talcen during the winter i n order t o c a r r y out c e r t a i n

ty-pes of work which n o r m l l y cannot be c a r r i e d out durinz t h i s season vrit:lout a d d i t i o n a l expense. This booklet does not claim t o be conclusive b u t merely r e p o r t s on p r a c t i c a l experience

gained and observations made i n winter construction. F u ~ t i ~ e r ~ n o r e i t s scope does not permit a d e s c r i p t i o n of a l l t h e ;naAlnerAy for

winter c o n s t r u c t i o n found on the market. I n cases where t h e t r a d e names of d i f f e r e n t devices have been given tbis does not n e w

the d e s c r i p t i o n p r e s e n t s an opinion, I t i s merely intended t o show roughly what rnay be useful. Data

on

the c a p a c i t y and con- suinption of f u e l , e t c . , have been gathered from the d i s t r i b u t o r s of the devices,

The type of work which i n c r e a s e s the c o s t of cons-kuc- t i o n during t h e winter i s c a r r i e d out c h i e f l y by u n s k i l l e d labour

and bricklayers.

It is reported wider the headings:

Foundation morlr, concreting and ceinent work, masonry,

interior plastering, maintenance of building site, snow removal,

etc.

*

WINTER

T ~ K 4 T i G R

CONDITIONS IN

SWEDEN

Cold weather, Cold weather conditions in different

-

parts of the country bring about different conditions of depth

and duration of frost. This decisively affects the planning of

foundation work.

According to

BABS**

"unfrozen groundn is the gram-d

below the surface on which the foundation walls and footings

nay be erected without danger of freezing. This suggests that

the u;afrozen ground always is a relative value. Apart from the

temperature the following factors affect the freezing of the

soil: thickness of the sncw cover, duration of the snow period

and geological conditions of the soil. Therefore, under ex-

ceptionally ~ m ~ i ' ; ~ v o u r ~ b l e

con.diJ~ions,

the nurrier:ical

du'ta on

'c11.e

u.ilfpozen

g-0~~1.6- 1im.y be

very n:isleadS.n.g. This may

have d i ~ z s -

trous consequences. It provea costly to

raw

b u . i l d e r s 6 u ~ j . i ~

the cold 1-linters of tile last

m a r .

The

map

shovm in

Pig. 2 lias

been corrected by ta!iirg into ccc:>unt the values fop I;l-~c

unf"ok;en

~ r o w d

during these winters.

U

The effect of the colb

~;'eatl.ler~

on otiiei-.

tyyes or con-

struction work varies. 3epeated fluctuations in terlperat-ure

zbout O°C. have an adverse effect on co~creting,

even if the con-

crete itself is frost-resist:cn';,

Thavrs altern:~tinll;

ivitll perlods

:*Tennir,ology in the present boolile'b is identical with that; of

(4)

[cf, list of references on

p,&g]

of the present

paper

.

cf f r e e z i n g may have a devc.sJ~e.tln.g e f f e c t oil other. t~y-pes of' con- s t r u c t i o n work a s well. The d i a g ~ ~ ~ i : ir, Fig.

3

c l e a r l y shows

how the .l:ri:iter i n Stoclrhclm i s c l ~ a r a c t e r i z e i l b y incessan-i; ch.anges a-bout t h e f r e e z i n g p o i n t , i. e., cl.lz~r!-ges e.bozt O°C. I n Wo?-.rla~.d p e r s i s t e n t , f r e e z i n g terq)erz.tures imy Ise expecJ~ed with sonle

degree of' c e r t a i n t y and p l a n s car, b 6 l.ilade ac ~oi?dill.l;ly.

Freezing teml;eratures reduce the ctlpacity o f t h e nt.ji10~- pliere f o r absorbing moisture, i, e.

,

they i n c r e a s e t h e r e l a t i v e h-wlidity of t h e atmosphere, This t h a t t h e re1a"~iv.e h~i.!idii;y OF t h e atmosphere i s higher d~~r.i_ng t h e ninJier than d - u i n g the s m n e r d e s p i t e t h e f a c t t h a t tl-;e &sol-xte moistuse content of t h e atmosphere i s lower, Hence, owing t o the cold vieather during t h e ivinter i t t a k e s a b u i l d i n g longer t o d ~ y out

(CP. I n t e r i o r p l a s t e r i n g , p , 3 0 ) . Honever, if' t h e a i r teriperat-ure i n c r e z s e s t h e r e l a t i v e h~unid5tg of t h e atmosphere decreases and t h e capa.city of t h e atmosphere f o r absorbing ~ ~ i o i s t u r e i s thus incre:~sed. The f o l l o v ~ i n g ee:r:irnple i l l u s t r e t e s t h e irrrl,o12t::nce o f t h e a i r tei:qer.r,tulae f o r t h e r e l a t i - ~ e :i~x!~ridity of the ai;;;iosphere.

A t a ter;~percture of + 2 0 ° ~ . a ~ i d 100% sat~i-:?:tion 1 l~gr:!. of' 23-r con- t a i n s

14

~ m .

of water. A t +55OC. and 100% s a t u r e t i o n t h e s.me

m o u n t of air. can absorb

_'_I4

cn,

of water, This exarilple sfloas how i r q o r t a n t h e a t i s i n cons'truction vic~rl; because o:C' Clle g e s % d e a l of moisture produced,

I n c e r t a i n respec1;s

the

persLst.en'r, f r e e z i n g 'tenlper- atu-res and t h e more sevepe f ~ o s t br~ Norrlanfi seem t o be nore o-

l e s s compensated f o r by the f a c t t h a t tlie atrriosphere i s ;lp:i.er h e r e than i n c e n t r a l and southern Sweden, e s p e c i a l l y a t t h e v e s t coast. I n o t h e r words, t h e r e i s no combination of low temper-. a t u r e s and high h u m i d i t i e s of' tLe atmosphere, Therefore, t h e elinlate of Norrland is o f t e n more favourzble f o r t h e storr.ge sf c e r t a i n t m e s of b u i l d i n g m a t e r i a l s , e.go b r i c k s and lul;ibero

Snow. Although the prob1es;s of snoT;r relxoval a r e much

-

@12ec t e r i n Forrland than i n c e n t r a l and socthern SncSLen, the "real1' winter i n PJorrland with the snol:I cover rclnaining on the gpo~md f o r a c e r t a i n l e n g t h 02 time has i t s zdvmtages f o r

the

b u i l d i n g a c t i v i t y , Thaw and s l u s h a r e not encomitercd t o t h e same e x t e n t here. Therei'ore, i t may be expected tht:t the snow becomes pzc!ced and forms a b e t t e r and 1nol.e perrilanent roadvray,

Darlcness, The hours of d ~ . r k n e s s during the ?.linter i n d i f f e r e n t p a r t s of' Sweden c a i ~ be seen i n the diacrarns s h o ~ m i n

1 -

1 ,

6

A s the c r i t e r i o n of d i f f u s e d "6-a:.rlizht", a l i c h t in-

t e n s i t y of 500 lux has been chosen, I t i s nss-~uzed t l ~ : ~ t t h i s i s the minimnun amount of l i g h t rcquired f o r c a r r y i n g on c o n s t r u c t i o n work,

How much a person can see a t a b u i l d i n g s i t e v ~ i t h o u t a r t i f i c i a l l i g h t does not depend on the d i f f u s e d dz-ylight alone, The r e f l e c t i n g poner of the ground i s an important. fuct,or and

r!;ust a l s o be tdcen i n t o a c c o ~ ~ t , The r e f l e c t i n g poner, oS covrse, is increased t o a g r e a t e x t e n t by the snolrr. Therefore, frora

t h i s p o i n t of vien snocvCalls m e advantageous.

It i s a l s o i r q ~ o r t z n t 7:~l~et!ler the slcy i s overcast o r vihether i t i s hazy o r clear. Fig,

6

g i v e s tile hourts o f smisliine p e r month during t h e y e a r s 1951--52, i.e., the sune p e r i o d a s

i n

the diagram f o r temperature and p r e c i p i t a t i o n ( ~ i g ,

3 ) .

Lenqth of Winter

The need f o r measures f o r d i f f e r e n t types of c o n s t r u c t i o n work v a r i e s with the clir-latic collditions o f diff'er- e n t p a r t s of Slyreden. If t h e s e rnensures depended only on terxper- z t u r e s and snowfalls, the a c t u a l beginning of' n i n t e r would s t i l l be dubious i n many instanccc. I n the i l ~ t r o d u c t i o n of t h i s pzper the >:!inter l ~ a s derined as t h e t i x e during 'iihich s p e c i a l measures rL1ust be taken a t a b c i l d i ~ s i t e , I t i s c1e::r t h a t a i l l l e r thus

defined does not s t a r t s i m ~ ~ l t a n e o u s l y f o r a l l types o f constru-c- t i o n work.

For example, concreting cannot be c a r r i e d out -uith- out s p e c i a l rneesures a t terxperatures below +50°C. A s Big.

3

s110\;'1~, an average teli~perature of noye than +5OC. cannot be ex- pected i n the Stoclcholm d i s t r i c t between f:rovember 1st and 0 - p r i l 15 th::'

.

This rnezns t h a t what be crilled i n t h i s conncction "-;!interw a s f a r a s concreting i s concerned corresponds t o t h e p e r i o d betmeen Novernber 1st and A p r i l 1 5 t h i n centrsil S::ied.en,

Regarding i n t e r i o r p l a s t e r i w the winter period i s roughly the smle a s i n t h e case of' concreting.

The heating of t h e shacks corr_es under maintenance of b u i l d i n g s i t e . I n t h i s case winter begins e a r l i e r , I n general,

t h e h e a t i n g of the shacks begins around October 1 s t and does not cease before some time a r o ~ m d t h e end of April. Therefore,

winter a s f a r a s t h e maintenance of the b u i l d i n g s i t e i s con- cerned m a y be considered a s p e c i f i e d period ( ~ c t o b e r 1st t o A p r i l 30th)

**.

F0UT:DATION WORK

Everyone i n the b u i l d i n g t m d e lcnovrs t h a t

i t

i s most advantageous t o begin b u i l d i n g s r t f f i c i e n t l y e a r l y t o complcte t h e foundztion work before tlie f r o s t s e t s i n , If f o r one r e r s o n o r ailotller t h i s should be impossible, irluch can be gained by

covering the p a r t o f the ground t o be excavated, thus p r o t e c t i n g i t a g a i n s t f r o s t . The i m t e r i a l f o r covering t h e excavation

c o s t s very l i t t l e compared with ~vliat i t v?ould c o s t t o excavnte frozen s o i l .

::: One day mild and a few degrees o f f r o s t t h e next i s not unusual f o r Stockholm.

*:::In order t o avoid unpleasant and sometimes c o s t l y s u r p r i s e s the changes i n the must be taken i n t o account,

For l a r g e and ~ n e d i m - s i z e S u i l c i i n ~ : . ~ the e;iccv:~tion

f o r the 'sasemcnt i s g e n e r a l l y il~ade by a11 e;:c~.v:.:tor. A s ~ ~ Q I ~ ~ el.:cttvator norlcs r i g h t t l ~ r o u g h a f r o z e n c r u s t 25 o r 30 cm, tl~icl:,,

This means tll::,t t h e ground sl1oul2 be i ~ r o t e c t e d b y a cover i f t h e d i g g i l ~ of t h e excavation i s :>l~~l?lred a t a t i x c vr';t.eli t h e f r o ; t has y e n e t r a t e d t o

a

g r e a t cle:~th, b u t ti1a.t a covep i s not r e q u i r e d f o r mild f r o s t o r fox1 s h o r t d e l a y s i n t h e exczvation norlc,

The foundation silo~!JrI'~ bc b=lclz T i l l e d up t o t h e ~ ~ 0 ~ ~ x 3 n a l l s 3 s soon a s p o s s i b l e . Frequently t h e r.iate'iz.1 r e q u i r e d

f o r Sack f i l l i n g t h e f o ~ u z d a t i o n i s l e f t l y i n g a t the b u i l d i n g s i t e and f r e e z e s , This means i t must be l e f t t h a t way and may thus i n t e r f e r e with t h e Fpogress p r s c t i c a l l y t h e e n t i r e t i ~ n e a b u i l d i n g i s under c o n s t r u c t ion. IIon much t r o u b l e tl?is ZiEL:r cause

need n o t be ein13hasized. ThercTorac, t h e m a t e r i a l f o r bac!r

filliw

t h e f o u l d a t i o n rr'ust be renloved :;t a l l c o s t Sef'ore i t f r c e z e s , If' the m a t e r i a l Freezes and

i s

then removed, i t may cos-t t e n t-irries a s niuch.

P r o t e c t i v e Cover f o r t h e Ground-

-

A l a y e r of sera:.!, o r s i m i l a r iasu1:;ting imaterizl,

a p ~ o x i n a t e l y

31)

cm. 'cliicls, i s uscd t o c o v c ~ tile growld if f r o a t es e;cpected,

The

s t r a u n-32 be ' ~ w ~ d l e d ; b ~ l i ~ d l e s oP s t r z n rimy

- -. .--.

a l s o h e used f o r t h e p r o t e c t i o l l of co~:z;-c.l;e, ,,..,.,cdLiene~:h i n Deixnar~: shox:!s t h a t stray! can keep t h e ground f r e e f r o z P?;losL

dolil;? t o .i;e!;l>errLtures of a:~proxii;lately -lO°C.

Excavations i n Frozen So22

--

F r o s t i n t e r f e r e s ,ibove a l l -t!:'itl? e:icavat i o n s dug by I such as trenc??.es, excavdlt i o n s f o r f oundntioils, trenches f o r f o o t i n z s , etc.

I t i s o f t e n e x t r e n e l y d i f f i c u l t t o p r o t z c t t h e grouncl f o r t r e n c h worli a cover. I t 1;2c?y even 5 e advanf,a.,eous i f

ve:>ticzl surfaces f r e e z e s l i g h t l y , This decreases t h e danger c o l l a p s e and t h e c a r r i e d out more e a s i l y

trenches, Treilclies f o p f o o t i n g s call be adequately p r o t e c t e d by coveiaing thein during tlle ~7iight vrith s ~ T ; ~ ; . J , t a r p : ~ u l i n s , e t c ,

S o i l exczvated by I-rand and used f o r r e f i l l i n g ,

i s

not covcred, a s a r u l e , and u s u a l l y f r e e z e s , The f o l l o a i n z methods ixay be a p p l i e d t o suctl f r o z e n s o i i :

( a ) The f r o z e n c r u s t i s brolien w i t 1 1 t h e a i d of ~.lredgea, I n case of moderate f r o s t a p i c k axe or an irosl b a r ;my 3 e used.

( b ) The frozeil c r u s t i s bro:re:~ up wit11 a pneu- 21atic spade,

n

very ei?fective device f o r f r o z e n s o i l , 210-,;rever, only i n t h e case of a l a r g e b u i l d i n g would the purchase o r r e n t of a comilressop be juc-:iFied,

( c ) The f r o z e n c r u s t i s b l a o J ~ c d ; honevcr, f o p the sake of s a f e t y t h i s can only be recoixr~leil-

dcd v~lien tlie b u i 1 d j . n ~ i s a t su-fficien-t d i s - tance from o t h e r S u i l d i q s ! o r e l s e oilly

slim11 q u a n t i t i e s of exijloslver should be used. ( d ) The f r o z e n c r u s t i s defros-tied, Iil 3em;xirk

t e s t s wepc maGe i r r t h i s r e s p e c t rliti? a hot- -zater stream under a. l a g e r o r s t r a v , cl~ernical a g e n t s , e-LC, But none of t h e s e methods a r e r e a l l y rec~ii.;~iencled by Danisli c o n s t r u c t o r s , I t i s ul12ilrely t h a t these rnethoLs have ever been t r i e d i n Sneden,

P r o t e c t i o n of 'i'ei;q3oray.t~ Water-S~steins

Teiiiyorary water systeril iiiust be prevented froi-n freezilig so t h a t no valuable time i s vi-lnsted v i t h thawing, Theref'ore,

it

i s of the u t n o s t ilrpoptslnce t h a t a l l w:lter conduits a r e erxptied when t h e l:;or:men l e a v e t h e b u i l d i n g s i t e i n t h e afternoon".

=:It ray cause a g r e a t c o n s t r u c t i o n i f t h e f r e e z e . Burst p i p e s vrorking hours a r e l o

d e a l of inconvenience i n a b u i l d i n g v n 6

temporary v~.r=l t e r syste1;zs a r e allowed t o are expensive t o r e p a i r and many valua3 s t if c o n d u i t s i a ~ ~ s t be defrosted.

Prcqidently t h e water system i s g r o t e c t c d b~ i n s t a l l i n g t h e c o ~ i d ~ ? i t s i n double aooden c a s i n g s f i l l e d ;-iith f r e s h horse manure and i n s u l a t e d w i t 1 1 g l a s s wool. The piye l i n e s :As0 ape

i n s u l a t e d .

Another method my a l s o be used t o 9 ~ - o t e c t the tenlpor- ary v r ~ t c r syster.1 a g n i n s t f r o s t , i . e . , by c o n d u c t i w an e l e c t p i c cui3reiit of 1 ~ i 1 v 0 1 t ; : ~ ~ e tkr?ough the p i p e i t s c l f 02 -th~ou$l

2n

~ m i n s u l n t e d c a b l e w i t h i n t h e pipe. Tile sane c u r r e n t a s d?a:-,n by a 40-watt l r u n i ~ i s e f f e c t i v e .

Tlie r a t e of chelilicrzl r e a c t i o n decreases a s t h e t e i - ~ ~ i j e ~ - afuure d e c ~ e a s e s . This a l s o a p p l i e s t o t h e r e a c t i o n of cei-,lent and water, as sho7in i n d e t s - i l i n Fig. 11.

If t h e tei;l]?erature of concrete ~ P O I J S belovvr the f3Xez;ing

p o i n t during pouring so t h a t ~ r ~ a t e ~ conLained i n the concrete fpeezec, t h e concrete cannot s e t . A t c x t e r n a l ter:~per.;ctures be-

t-.;:eei~ ;tO°C. and + 5 O C . concrete s e t s very S ~ O W ~ J T . Zveli a t +5OZ. the tirile r e q u i r e d f o r s c t t l n g i s appro:ciciately P o w t i n e s t h a t s t +20°c. I11 o t h e r words, vvheii tile e x t e r n n l t e n p e r n t u r e drops below +5OC. t h e t e ~ m e r a t u r e p a s s e s t h e bo-aiidary below viilich

s p e c i a l meanares inust b e taken f o r t e c h n i c a l reasons

i r

c o n c ~ e t e i s poured ou.tdoors

.

f ~ f ' t e r talcin2 v a r i o u s p r o t e c t i v e I-2eas-ures concrete can be ;,oured a t t e ; , y e r a t u r e s dovri %o -15OC. Ro-r~ever

,

o13inions

a s t o 7:rhat i s the l o n e a t p o s s i b l e e ~ t e - ~ i l ~ l terrll~erature f o r

; ~ o u r i n g coiicrete d i f f e r . I n Norrland i t i s u n l i k e l y t h a t a coa- t r - c t o r w i l l pour ~ o i i c ~ e t e a t a t e ; 1 ~ 2 e r a t u ~ e of -20OC. Zven i n

:%An extepilal t e m p e r a t u x of +5OC. i s tlie "viliter b o ~ l i i a r y ! ~ f o r concreting. ils f a r a s concreting i s concerned, w i n t e r i n c e x t r u l Sneden l a s t s fro:,^ Novernber 1st t o A-pril 15th.

t h e recor:~;-nendstions f o r concretil cIv.ri?lg thc ~ i l i t e r , ~ s G u : ? ~ by tllc S-::'edish Ceiilei~t Association ?lo)

,

and i n thc i n ~ t ~ u c t i o n s

col~cerning

a.

c o n c r e t i ~ ~ technique, publlshcil by thc Z7;,;cdish ( )

Resesrch I n s t i t u t e f o r Cement and Concrete

,

t h c lower 1ii;li-L f o r p o u r i ~ i g concrete i s s e t a t an a i l a t c ~ x p c r a t u r e of -20°c,

Hovrever,

i t

i s a knovm f a c t t h a t c o n t r a c t o r s i n Stocldlolr;~ n o r i ~ ~ l l y do not pour conci?e t e a t these l o w te~;~peratces::r.

The diagram i n Fig, 11 sho-irs llon the a i r tel;l-:erat-e a f f e c t s the hardening of concrete; t h e h a p d e i i i n ~ o r concrete of a given com:)osition a t +20°ce i s cox;)ared r71it.h t h e h3.rdenii1g of concrete of t h e smile c o r n ~ o s i t i o n a t :-wer tei-qeratures. A t

+2o0c,

the coilcrete a t t a i n s a s t r e n g t h which p e n n i t s loading with 200

-

250 ke;m./sq, cln. 28 days a f t e r pouring. This strei%.tl? i s r e f e r r e d t o below a s "28-day s t r e n g t h " and denotes a s t a n d : ~ . ~ d i n c r e a s e i n strength f o r ordinary concyete.

For e x a q l e , a t + ~ O C . t h e s t r e n g t h a f t e r 28 Gnyn i s

only from 60 t o

70% o f

t h e 28-d?-y s t r s n j t l ~

a t

+20°c. This i s t h e s a n e s t r e n g t h which concrete z t t a i n s a t +20°C, a f t e r only

7

days. s t r e n g t l ~ , i, e,

,

60 t o

7G$

oi" 28-day stre:l@th, i s colisidered the lowest s t r e ~ q t h ?v,tlich colicrctc r m j r have befor$ for:ns can be renoved,

c . ~ .

fop Irafiiiix j o i s ? ; s ( 6 ) . Hence a t an e x t e r n a l temperntuxe of +5OC, i t t a k e s 28 clays b e f o x the forills can be reijloved from concrete uilless the tc!:;~~er;?*tur,~ 02 t h e

concrete i s increased by various inez.11~.

ccIn order t o i n c r e a s e the t e u : ~ ) e r a t u ~ ~ e OF the m a t e r i a l f o r pouring,

i t

i s Gore

e f f e c t i v e t o lieat the v ~ a t c r ~ a t i i e ~ ~ than

t h e o t h e r ingrcdieilts o f the concrete, p a p t i c u l a r l y ~ i n c e tlie s p e c i f i c h e s t of n a t e r i s 1.0 while t h a t of' cei.nent a n d l a r g e a g ~ r e ~ ; ' a J i e i;; only 0,2. Purtheri:iore, the ten;perature of :i:_lter can be c o n t r o l l e d ;;:ore e a s i l y . A tcL;.2~er;rituac o f +60°C. i s j u s t r i g h t aaSz a tcizperature ez:ccciiin~ -1-7C0c. too li:;ha L t ixoder:~tcly low e x t e r l ~ a l t e ~ ~ ~ e r t n - i u r c s 1icc?ting the enater zlone

i s s u f f i c i e n t and the requii-ed terfipeP::;tr!.ro oi' the ;i:;-ltey+ A :

I..

I1

2. iile te1;ll)era'l;ti.i-e ~2 -bl;c ci.,z;;]ll.;; ~ j ~ ~ u ~ ~ e ; l c u l l -

,

.

.

.

C r e t e filuat llo$ decx?eLr; ;;e l j c l o ? , i c. c ~ i > i , , r . L- 7 . ~ >.:l.T.!,?-- ~ ~ .

1 2 ~ 1 1 d ~ p i p ~ -i>ie c-p-i-;ic;-!.J szt.Li;-pi - , ; ~ ~ ~ j ~ ~ ~ - . A. ,3 , .

-

- ., -'. ,- -1

3.

:_"he tirile Tor rcr;jcvi;lz .c:2pl.:c :J-;.c'.'' '

0 'a -, CL</.~! :, 2 -1

t o tile cold acz'cher condi~l;ior;c,

I?,lece + rcq.~~.irci-~;e-nts a r e i x t by t:~4iil< tile -r"ol.!.ol-~i~i;; ;;!ci;zr:. -,-: ' L ' t ,J * BeiiuiremenL 2: ( a ) S e l e c t i n g t h e proper t n j e of cericnt ( b ) Cher:ii c a l a d d i t i o n agen-i; ( c ) S u i t s b l e zater-cer.:ent r a t i o ( d ) P r o t c c t i o n 02 thc c o n c r e t e Z - u r i , ~ ~ the s e t t i n 2 time

~et~v-ii-ci;~ei1t

3~

(:I) ! l : ; r 6 1 ~ ~ ~ ~ t e s t

( b ) !:el. p ~~ K Y C ~ a013 SC~'V:, '~iorls

''hi. s;::r~C, n o t the src.vel, i s heatcc', as i.ndicated be- lo.Jrc pie y--,.-,,37r--7-

-

L,~,u., i,,lxe<- conclqe'Le ir?:;..rcd.iat e l y b:>gins 'Lc. ;ci:el-ai;e

k c a t o r i ' t s oT~sil. Too hi211 a tei.:~>ei.zt~~i>e izny ~ a s c l - i ; i n co.rig

c;v:.l)ollcL<ioll o r the l;~~-.tcl>, c a c s i n g i n i - t i a l s e t (ili-l-j.;lg . ~ 1 ? ; ~ ? 7 ~ - ~ <..;+ ."A, Oxa t-

r.tj.oi.1 t c ; t:le si-l;r: oj: A -QC)UT j . 1 ~ . Tl~ercfope, tile tecl.,-:1cpa.tl--la{:: ~f ";LC

;i;;-.tcy,i31 t c be ~-,oin-ed ;:lust n o t cxcecd +2() -I;o+3Corj.

:>*

If'

-i;Il-,

co::,rr,e ;r- . v . ~ l . i s not heated. t l ~ i s h;;c an ec:-i~e-1

j - z i i ~ c

effect 0x1 the

.*.

bci.;i2ep:::L7L:i:3~ of' tjlc ; ~ ~ z ~ ' l ; e r i r ; l in the :;lixe<:, concr(:-:tc=. IIo'<;ev~>i'~ if'

...

--.

Tarpr~uliris i x y be reiIJGcd a t ~ e l a t i v e l y lovr c o s t , at l e a s t Coil:- ; ~ s r e d >:~i.i;h vrhrLt it nould c o s t t o work t h r o ~ - i h t h e snow i f 3

p r c t e c t i v e covcr is n o t useCLe

It

scldci;~ i2ay:; t o cconoi:iize on l ; m ~ ~ : ~ . u l i ~ s .

-9. 0. r-,

-d--s.~llt? u.~;i;er t e l ~ l ~ ~ c r z . t u r e l i r n i t of c o n c r e t e n:-~~s-'; 5i: -?::1tc3eC. I t

t h e coarse g r a v e l i s heated, not only i s t h e e ~ u a l i z i n g ecf'ect e l i m i n a t e d , b u t t h e subsequent shrinkage of the a;;.;;re&:itc r:ay

re:;-~lt i n the 1oosenin;r; o r i n d i v i d u a l s t o n e s i n the concre'te l i k e a Iiazel nut i n tile s h e l l , The sand should not be heated too

L C ; t h i s i s iriiportnnt,

Foil lieciting t h e s m d with s t e m , p e r f o r a t e d i r o n p i p e s and steam j e t s a r e used, which a r e s t u c k i n t o t h e sarxl heap i n o l d ~ e r t o lleut i t a i r e c t l y , The stea11 j e t i s comiected t o t h e b o i l e r p l a n t o r t h e concreting i n s t a l l a t i o n by hoses, O f course, only t h e ar:lo-cu?t of s2nd r e q u i r e d f o r pouring sl-iould be covered r i t h t a r p a u l i n s i n order t o r e t a i n t h e heat,

Other more o r l e s s primitive h e a t i n g d e v i c e s a r e s t i l l found i n tlie sane p i l e s i n buildiw;s of a l l d e s c r i p t i o n s , For excmple, i t be mentioned t h ~ . t a curved i r o n p l a t e i s placed i n t o t h e sfind p i l e and heated i n t h e sane vay as an old-f'::shionecl baking oven. Speciril vrood s t o v e s of c s s t i r o n , so-c,zlled c:!n6. b r a z i e r s , a r e Frequently used, I F t h e s:~ncl i s 11c::teii i n t h i s

l.,-ray i t involves the r i s k of l t b ~ w n i l q t h e sandtt.

He:-ti-nfi; t h e *$rater g r e a t l y a f f e c t s tlic tc;;;per:;ture of t h e concrete. Since the s p e c i f i c h e a t of r7r=iter. i s high coi;x~med ,:ith t h a t of the o t h e r r n a t c r i a l s linking up tlie concrete, i t i s c l e a r t h z t n o t only does t h e water r e q u i r e a g r e a t h e c t input b u t a t t h e sane time i t suy;plLes most of t h e h e a t t o t h e con-

c r e t e mixture. BurJcherniore, t h e water must n o t be heate2 ex- c e s s i v e l y , s i n c e too high a water temperature m a y b r i n g a12ou-k premature s e t t i n g of t h e cement,

The Swedish Cement Association recoi-rri-lends the f o l l o a i n z msirnum terilpertltwes f o r t h e h e a t i n g c'r' b o t h sand and n z t e r :

+60°c, f o r t h e use of s t a n d a r d cement,

A s !.;entioned above, t h e temperature of t h e rezdy-l~iixed concrete sllould not exceed +20°C. t o +30°C, Such big-11 t ~ ; ~ ~ p e ~ -

ztuiaes m3y be z i ~ p l i e d t o tlze v a r i o u s r m t e r i a l s mentioned a'ucve, bec:>.uce t h e m z t c r i ~ l cools s u f f i c i e n t l y on t h e i-lag from t h e

s t o r c l ~ e plailt t o tile u ~ i x e r ,

I t h2.s becoixe evident t h a t a l l s o r t s o r boilel. p1rcli.l;~ s p e used f o r ! l e s t i n ~ t h c late rial 122liin~; up the concrete. S:;nd

i n ?;:;c tod3.y: Ion-pressure b o i l e r s znd h i g h - p e s s u r e b o i l e r s . I n t l ~ e p a c t , low-pressure b o i l e r s -:?ere most coi,monly used iil c e n t r d Cv~cG-eli, b u t today h i g h - p r e s s ~ r e b o i l e r s ape clorae f r c - quoiltly used. I n Xorrland, i t s inore severe c l i l x t e , high- p r e s s u r e b o i l e r s a r e e x c l u s i v e l y used f o r l a r g e - s i z c b u i l d i i u s under construction,

1,lodern lot*{-pressure b o i l e r s a r e c p i c k l y f i r e d and c ~ n be heated with n a s t e wood, sa-:$r3_ust, p e a t o r o t h e r r e l a t i v e l y

cheap f u e l . According t o corfirfiercial a d v e r t i s i w t h e b o i l e r s

zre

l e f t c'i; P u l l staar;l f o r

7

minutes,. tile s t e a ~ n c a p z c i t y being from 150 t o 200 kgn./hr, These b o i l e r s have all el>tixhely automa-l;ic

vU7rlter feed an6 tile f i r e box i s surrounded by i-rater, \;rlzicil pPeverf-- L 4 0

~ ' v e ~ l l c t i t i i ~ of t h e s h e e t metal.

A s a r u l e , t h e h e a t generated by 1ov~-pressure b o i l e r s i s not si-dficient t o h e a t both tile g r a v e l and t h e n a t e r as vie11 a s a i ; i ? u l t a i i e o ~ ~ l g 'to tl-~avi t h e i c e and S ~ O V J i n t h e f orr:,s ~ i l d pe-

i17forcenieilJcs. Therefore, lovr-pressure b o i l e r s a r e f r c q u e n t l g provided 1:;ith a s p e c i a l water h e a t e r ,

A s a r u l e such a n a t e r h e a t c r i s designed i n ayproxi- i?:iitelg t h e f ol1o::linz way, The ::!ater i s c o n d ~ c 'tcd f ror.1 the

tei:porary !.;rater systc!:i throwll B c o i l e d p i p e ( u s u a l l y of c o ~ ) ~ c r ) , ;-rhich ends L I ~ i n a tank. The tank m y vary from a11 ordillrtry

.p.

:,-,

. 2:- cLgc;S y2cj;

,;-:---.cc

.:;, .;: !,2 ;;;< ;??,-;+ -: .:, 7:. c. JGS 6.. <> :-,..- Ll(> il . > , - --

".!.I- _{U . . . ,} . I:le cost _9f 7 .; -- , . ,, *-

1 ,:I:: cCIY.~ l :?l-:~ ;c;i;t:; > : ~ ~ a OIICl-;L'L<-,?r- -.: .LC> .a:..->?-i;Ol.>.;Jr-i b~ . L.. .J.- r-1 u -,La- 13r a- A. ?iixcJ,-

..-

- L - L ~LcLLI- ~

-7:

L L ~ ~ : ~ - ~ j ~ 2 ~ < ; ; ; - & ~ ? : ~ bo.:l(;j: ; ~ ~ ; ] ~ l . ~ ~ ; g;ay ?.>C ( Q ~ ~ l > . ~ { ; * ~ , J b.77 u-:-

i . cl -.A ; ; , ~ + j ~ ~ , 2 L ~ ' 1 - c . L ; -lj,c~?7-.>- L - - -:i22 2;; :r;:y>j.::<2:?., :;::;c :l:::l(; 13 11 -:.:I ;: 71 $7 2, -j-<>:.>::; , - . ; - ~ l . ~ - ,

.

-. > , l ~ , ; stn,~- ,., , .L.A 7 ' c . ~ ; ~ r - i ~11j-s v c ~ l a l l - ~ ~ fv-3-177 ~ ~ ~ q j ~ ! .3 1 1 ~ ; : ;:;l:yl r. -f ~:.:l-r;: .. U 1- .

-

.: :,, ,..: 1 CL 5 :I:-;2) 7 9 j c ,c

t

.

y l e

lc-x.k-l

5r

c x . ~ ~ . ~ , ~ ~ ~ ~ ~ ~ ~ rJ c ~ ~

-

~" ~- , , - . 7 ? 4 - - , - - . ~ - it ~ q > ~ 2 1 . ~ 7 ~ ~ - & ~ ~ ~ ~ ul> . , .

c ic ~z]-p~.ki~:~l 02; ti-lJ:; p p O i ; e F ~~;;1;:ilt t;,q>~, 'kh~: ~ i . l ~ ~ ; ; : . ~ : . . : l ;1;~lq3:,2~\~ ,-. ,,- < , . - > r 7

-+->-,,

. . r c ~ ~ ~ ~ ~-pc1.t-0* ~ , - ~ p : ~f-i>c;~kl13. , ~ ~ ~ ~i)ij-~:p:><. ] ~ ~ c ; , , ~ > ~ , ~ ~ > ! - : ~ ~

. . , L e d " - . , , . . , - L A I,i.-\, .. <... .,-...-

, .>-;;; 7,: c> .;,I I-d ,L ;;; Jc ;?,=I in 0 pd~.? U A ~2 'c, Q 1-2; . L C ~ L3-1 tile 11 c ::i .b 'L i 221 :>y!+c-

Guick-setting ceixelzt geiierates imch more h e a t than

s t ~ ~ n d a . ~ d ceinent ciurinz t h e s e t t i n g tine2:', IIor-ievcr, t h e paw

l;ltitci3it.;l Tor the c o i ~ c r e t e inust b e heated i n t h e u s u a l rimmier

2 . u - i A a g tiie pouring, b u t need not be C O ~ J ~ P C ~ o r heated subsecjuel~tly. If quick-setting ce~nelit i s used, the upper tcfil2)erature l i m i t f o r tile inate17iiA f o r pouring i s considcr::bly l o n c r than t h a t i n t h e case of stcndard cement. This rnust b e talcell illto account ;.,hen t h e -::atcr and ;;ravel = r e heated.

At 1e;:st

350

1::',1:1, of q u i c k - s e t t i n g cement p e r cu,m. oli" concre,te sliould be used i n tile r:~ix.tul-e. Tile poured concrete can be loaded v ~ i t h o u t clanger, i , e . , t h e forcis may be d i s a s s e c ~ b l e d a f t e r

3

o r

4

days. During tiie c r i t i c n l s i t u a t i o n i n tlie b u i l d i n g i n d u s t r y quick-settixg

ceixen: r?as a s c a r c e itern beczuse of' supply d i f f i c u l t i e s , Further- more, quick-settine; cement c o s t s fr01-n 50 t o 706 rcore than s t a n d a r d

ceiLlent. Therefore, a s a r u l e , q u i c k - s e t t i n g

cement

i s used only f o r s r m l l jobs and r u s h nor!^,

I t i s very important t o avoid t h e use of o l d cement (and p o s s i b l y celnent containing hur~us inipuri t i e s ) during t h e

a i n t e r r Cement sllould n o t be s t o r e d f o r ally l e n g t h of time under f r c e z i n g c o n d i t i o n s and not xore than i s a c t u a l l y r e q u i r e d f o r p o w i n g sllould be made.

( b ) Cliemical a d d i t i o n agents

Chemical a d d i t i o n a g e n t s a r e used during the winter i n o r d e r 'LO has'cen t h e s e t t i q of' t h e concrete, A s a r u l e calcium c h l o r i d e ( c a c l , ) , which reduces t h e f r e e z i n g p o i n t of the con- c r e t e somewhat, i s added- Roacver, t h e arnount added i s n o t l w g e enoW1l t h a t Ll~e u s u a l p r o t e c t i v e measurer, i;lay b e dis11enseG v ~ i t h .

*3-day " q u i c k - s e t t i n g c o n c r e t e t t = 7-d2y stzndzrd concrete; 7-day "quick-set t i n g concrete1' = 28-day s-tanciard concrete,

Concraete c o n t a i n i n s CaCl, f r e e z e s a t approximately -5OC. and i s 12Gpe r z a d i l y a o r k a b l e , This ];lay b e u t i l i z e d For Teducing t h e .::zte~ con-teilt of t h e concrete. Ho?:revzr, t h e s e tv~o proper- tie:; aye only of second:x-y i r ~ r p o ~ t a n c e . The f a c t t h : i t CaC1,

a <. ,bcns -'- t h e scttin;j; of the c o l ~ c r e t e i s of prilile irq3ortance.

C'? coui-sc, c a r e sllould b e taken t h a t t h e c o n c r e t e dces ~ o t 'oe2i.11 t o s e t i n t h e c o n c r e t e mixer o r on t h e aay t o t h e Sob,

As a r u l e ,

1'7:

of t h e ~ ~ e i z h t of t h e cenent i s a sL~FLnlcle a n o u l t f o r t h e a d d i t i o n agent. If t h e e x t c ~ i l a l

te,i~~jcr:~iture i s c:ipectcd t o drop below -5OC. d i i - e c t l y ~lf'ter -Lhe pou.rilx, 'the a,:o-silt shoulC b e i n c r e a s e d s l i g h t l y , b u t ;lo% " u o

..-

::.c,, -, e tllnn 2;; oio t:lc v:eight of tile cerzeat. FuPtheri;.iol~e,

the

cuncrote i:lust be covered a s r z p i d l y a s p o s s i b l e after t h c

According Lo t h e 3l:~edish Ceii?ent Associatiox, t h e

t v n .L L, li, "-^l-..i;ll of' b ~ l e c o n c r e t e incre::~ses i n tlie foll.onixl;l; i;la;me~-? ~-!iien ~k~~ s-~,p~,,,-!..'.?.

thz ai~ioult of calci11ili;- c l l l o r i d e added i s 27;.

""

-A- d l of

=1 2-day sai:rple i n c r e a s e s a,)proxirnatelg 50$, thtxt of a 7-dr3.y ~r~;q>Z-e ~,,p~o>::t 2572 and t h a t of a 28-dng S L ~ ~ ) ! - F : a p p ~ o x i - :;i::tely

lo:.%

cor;p@rcd with a corresponding soncz,ete :7i-b1-1 ilo

sl.le~:-!ic:ll ag~i1-1; added. IIowe.vep, t h e Tina1 s t r e n g t h ? ; r i l l - ~ e

nq-:l;=o>,~ii;i:ite]-j- A - sgi:le i,n b o t h cnsesu('O)e The t s l i q z j ? u t w e of

a ~ ~ o w c d conci?ete with a che;.cical agent addcd rho.ul:l n o t 6.~:-

c;.ea:-;e Selo-.-I +lO°C. d u r i n g t h e f i r s t day 2nd i10L belora 4-3OC, 2-",7,r.i>, l;:12 tllipd clay,

( c ) S u i t z l ~ l e .;:~ater-ceinent r a t i o

The c7,anzer of' t h e c o n c r e t e T r e e z i l ~ durinil;. '~1-e f i r s t c r i t i c : : i l s e t tizx x)eriod d i ~ i n i s h e s i f the aatcr-cexeiit r a t i o Is ' - - ~ ; t ILL^, :.IS lo;:? 3 s : ) o ~ s i b l e . T h i s i s v.su3lly taken i n t o a c c o ~ m t t ~ d a y 2nd evcryt1lin.g p o s s i b l e i s done t o 1;ee~l thi:; r a t i o do-c~T!..

Concrete v i b r a t o r s a r e i r ? ~ ~ o p t a n t i n t h i s connectioli, silice they 11er1.iii t2;e v-sc of a C r i e r concrete*.

(6) D-:~rinz t h e s e t t i n [ ; time t h e concrete i s p r o t e c t e d by covepi?;:; i t n i t h a h e a t - i n s ~ l a t i i l ; : . n ~ a t e r i a l , The e a r l i e r

dm T Tpc-;l2h c o n c r ~ c t e i s i n s u l a t e d , t;le be-Ltel? n i l 1 be i t s q u a l i t y .

E':;p~"i-' ?;q-s xjlc-,sed d i r e c t l y on t h e concrel;e r:ny h e l p t o reduce he2.;t losi;es (il;-~e t o col-lvection and r;?.~~-i~l.tion).

In

o-l;hc13 r e -

~;-,eci;s papzr b a - 2 ~ ape v-seless :IS i n s u l z t i n g m a t e r i a l . The in-

"A

sv.l:;tion 1-111p.t be ti211tly x~tiac!.-,ed, G a p s i n t h e for!;ls a r e o f t e n c:rcelient Tor p r o t e c t i n g t h e concrete. For exte13nsl i a s u l 2 . t i o n

-tile z:l.~;.;s r;:a:r be covered n i t h talay)aUins, The most eTf ec t i v e

l-~c;:;t-in:;c.l~.~ t i 3 2 materials a r e s t r a n , s t r a n ~::ats, g1:rss T-1001

;-la.ts, ce;.:erl'i, 322s f i l l e d ~ c - i t l l c u t t e r sllavijl;l;s, etc.

( e ) Concrete ;;-rust 71e heatcG duriri.:;; s e t t i n g tirile i f

e>:tep:.;::>.l "i.c;.i~~cr;;tare d r q s b e l o x -5OC.

,

or i T tilc conc?ete =;tiz.dct~rac i s i j ~ . ~ t i c ~ . l n r l y t l ~ i n . I n such c a s e s tile h e z t i s

~.:,-,l i1sd vlifiep concrete ~1::-.bs, n o t only t o prevent -the concre'ie

i - L ,,1:!:' r C, j";.oT11 fpeezing b u t a l s o t o ? : ~ c i l i t a . b e .I;llc loosenill;' of

rpoc7

a-- -fop;n~.'.J-

L, L11

'.

...

T h e - t e ~ > p ~ e r : ~ t u r e of tile colicrete shoalc3 be cllcclced

1:i-eTcp h1.y v r i t% i;lelr;lor:leters i n s e r t e d iil t h c Presllly 20112.~ed ;.lntei*ial*:::*. 3,all h o l e s of v a r a y i ~ depth ,-.:riy b e l c i ' t i n 'idlie

::: Tile v i b r s J i c r ~ ) l z . y s all ir ; l o r t c n t pole durilig $he vrln2~ela,

;j::r-l;icul.;;rly 1-ri~en r e l a Lively t h i n w a l l s t r u c t~:rca ape l~o~~-l>eSi.

T_lais T l3er:nits _the use of a d r i e r concrete and d e c r e a s e s t h e

d ~ . n ~ e r t h a t t h c colzcrete Treezes b e f o r e i t beco;-les f r o s t - rcsist:-:nt.

Avoid cverllenting under f r e s h l y poured c o n c r e t e sl 1lb~i11)t chcli;;es of tti-nperzture o r repented changes

i r s y b e ?Letri~.icll'btcl t o t h e c o n c r e t e , even i f T t i s

all,

nbout 0

f r o s t - :::::zz:Tlzermorne t e r s a r e e s s e n t i a l d u r i n g t h e v i n t e r . A iim:cirl:u~--

:iLnirr.m,i tile rrnome t e r i s needed f o r rreasuriw t h e c x t c r m l te;;q)era tulic *.lnd t h e r e should b e s p e c i a l tl?errno~,leter~s f o r t h e concre1;e.

concrete f o r t h i s purpose ( c f , ~ i g . 2 5 ) . I t iViould be idez.1 i f

tlie temperature could be prevented from ever dropping below +7OC, d'clsing t h e s e t t i n g time. T h i s o f t e n r e q u i r e s t h r e e days

of heating, After t h i s tirne t h e cement ~ e n e r a t e s s u f f i c i e n t h e a t of i t s o~yn t o maintain t h e ter.q)erature.

If too cluch h e a t i s applied under a f r e s h l y poured concretc s l a b T o r

3

days and the concrete i s then allo-:red t o s e t without p r o t e c t i v e measures a t e x t e r n a l temperatures below O°C,, the concrete seeras t o be detrir,lentnlly a f f e c t e d by the abrupt change i n teinperat~we, even ii' t h e concrete has becorxe f r o s t - r e s i s t a n t , Purtl~ermore, t h e water i n the concrete

evaporates too r a p i d l y i f too much h e a t i s applied, Tilerefore, s o d e r a t e h e a t should be np2lied e i t h e r under o r w i t h i n t h e Tresilly poured concrete,

On the nhole, the s3me types o f h e a t i n g device

are

used f o r concrete a s f o r the dryilz;= of i n t e r i o r p l a s t e r ( c f ,

pp. 30-35) a r e placed under the f r e s h l y poured colicrete, Holes i n the brickwork a r e covered n i t h makeshift arraizl;e;;ieilts

such ss cardboard, vood, etc.

Coke b r a z i e r s a r e the most corn-aon h e a t i n 2 devices (cf. Piz. 30 and p,32).

\Vooa stoves a r e described i n greater d e t a i l on p.33. B o i l e r p l a n t s a r e occasionally used Tor lieating con- c r e t e duping the s e t t i w tirne by conveying the s t e m i n ribbed p s c l i o t i n ~ piy~es, which a r e lnounted under t h e fpesilly poured sl,ib, Ho~revcr, t h i s would r e q u i r e s p e c i a l connection p i 2 e s thus malting the i n s t 2 l l a t i o n a l a r g e undertalcing. Tiiererore, the espcnsc For h e a t i n g the concrete i n t h i s n ~ y i s out of'

p r o ~ ~ o r t i o n LIZ f a r a s an ordinary dwelling 5s concerned, If' the s l z b has a very l a r z e s u r f a c e , a s i n tile case of schools,

h o s i ~ i t , z l s o r cor:i:li:?ercial b u i l d i : c s , the i n s t ; ~ l l r x t i o n OF E L L C ~ . 'I plali"c;z;?ay be j u s t i f i e d ,

A kerosene-heated h o t - z i r unit of the

"LIEI-

t or!;!' trL?e

( ~ i z .

2b)

has been on t h e r:larket i^or t11c p c s t feu-; years.

IIot-air f 3 - n ~ aye seine-ti;::cs xsed, b u t ~ 1 0 3 t1y f o r dr;'ii^;;1; t5e p l n s t e r (el'. pp,

30-35

)

.

3 ,

Tiiile f o r P C ; . ; O V ~ ~ ~ : t l ; ~ I?OY ,I:;

--

..;;L~-s% 753 ;i.d>j~t~G t o

the COW-::.cz'tller condi t i o n ~ .

The time f o r r e ~ i l o v i ~ the f o l ~ i l ~ i s deteilr,ii~lefL by the s t r e n ~ t h 'rhich t h e concrete l m s t have i n orcler t o su;7po;?t i t - s e l f and p o s s i b l y an a d d i t i o n a l load, This t i n e i s ~.f.;'cctecl by the nurnber of cold days,

( a ) B a r h e s s t e s t s a r e rlaile i n s e l e c t e d cases. T1:e san?;,le i s poured sir;lultaneously z i t h the conclaete cor_strv.ction and exposed t o the sariie changes 02 t e c q ~ e r a t w e a s the l z t t e r .

( b ) Tempera tvxe ob s e r v c t ions inclucie the c i i e c l c i ~ ~ of '~hc t e r q ~ e r n t u r e

of

both the a i r ttncl the concrete. I n vien of the L'iict t h a t the f o r r m a r e g e n e r a l l y n o t ~ ~ e n o v e d before seven

&ays after. t h e pouring, tlie days v i t l i an a i r ter22eratvce 1oi:icr

than 0 " ~ . m u s t not be cou~tecl,

A

d i a g r m sllov~ing thc i n c r c c ~ s e i n s t r e n g t h of the concrete a t vnrlous tenlperaturez; sliould be

n v a i l ~ ~ o l e 3% the b u i l d i n g s i t e ( c f . Fig. 11.).

~ e n e i a l Rules f o r pour in^ Concrete D u r i w the Winter

A t the moment of pouring, the t e r i i p e r ~ t u ~ e of the ready-mixed concrete i s maintnined 2.t a !.iiniKun of

+5OC,

i n

. t l ~ e s l a b auld ground w a l l s and a t + l O ° C . i n thiruic13 buil-c',ill_~; r ~ a l ~ t c , such a s walls,

A s soon a s the f r e s h l y poured concrete b e s i n s t o generate h e a t , i t s tenlgerature should be maintained b e t r e e n +15 and +20°C. during the t h r e e c r i t i c a l days. The concrete

thus a t t a i n s the degree of s e t t i n g r e q u i r e d t o become f r o s t - r e s i s t a n t .

The water-cement r a t i o of the concrete m u s t be kept a s low a s p o s s i b l e i n order t o decrease the danger of cracking and f r e e z i n g ,

If the amount of cement i s increased, the time re- quired f o r s e t t i n g i s decreased and thus the dangerof f r e e z i n g i s reduced,

If quick-setting cement i s used, the m a t e r i a l must be heated and the f r e s h l y pouraed concrete covered, b u t the con-

c r e t e need not be heated during t h e s e t t i w time,

The time which t h e form f o r the concrete must be l e f t i n p l a c e depends on the number of cold days*. The reader i s r e f e r r e d t o pages 26 and 27, where a s m l a p y i s given of the measures which should be taken a t d i f f e r e n t a i r temperatures within the f i r s t week a f t e r the pouring(according t o

H. ~ b l h f o r s ( ~ ) ) . O f course,

i t

is assumed t h a t the temperature never drops belov~ the lowest temperature of the i n t e r v a l s

given. These measures a r e intended t o a s s u r e t h a t t h e b u i l d i n g a c t i v i t y i s i n t e r r u p t e d a s l i t t l e as p o s s i b l e , This i s a mini-

m

of all-round p r o t e c t i v e measures t h a t may be recommended,

*A diagram showing the i n c r e a s e s i n s t r e n g t h of the concrete a t d i f f e r e n t temperatures should always be a v a i l a b l e a t t h e b u i l d i n g s i t e ,

When no CaC1, i s added the water should be heated.

When CaC1, i s added no s p e c i a l neasures a r e required, b u t the forins should be rer~loved a f t e r approximately t h e same tiine a s duing the sumier,

The water should be heated and p r e f e r a b l y CaC1, added, If CaC1, i s added, t h e con- c r e t e m y be poured without h e a t i n g the wa t el*,

The sand should be heated and f r o z e n l u r q s tha7,ved, The f r e s h l y poured concrete should be covered during the f i r s t n i g h t with t a r -

p a u l i n s or cardl2oard on a frarfie~~vork, o r a t l e a s t v r i t h cement bags,

The water should be heated and p r e f e r a b l y CaCI, added. The sand shoilld be heated and f r o z e n lumps tha-,?red, The Freshly poured concrete should be i n s u l a t e d f o r t h r e e days with straw, straw mats o r s i m i l a r i n s u l a t i n g materials. Gaps i n the s t o r e y below should be covered and the temperature i n the room under t h e concrete s l a b should he kept above O°C. f o r t h r e e days,

Lower than -lO°C, I t would be p r e f e r a b l e t o postpone the

pouring of the concrete, b u t i f t h e concrete must be poured the same measures a s a t

temperatures between -5' and -10°C. should be taken, The i n s u l a t i o n should not b s re- moved u n t i l t h e temperature s t a y s above -lO°C,

The measures t o be taken a t a i r tealperaturcs below O'C. a r e only f o r preventing the concrete from f r e e z i n g .

The water used i n cer,ient work during t h e win-ter must be heated a s f o r concrete. S p e c i a l measures f o r h e a t i n g the

cement during the s e t t i n g time a r e u s u a l l y not required, s i n c e the b u i l d i n g is roofed when cement vror!: i s c a r r i e d out, F u ~ t i r c r - more, by t h i s time the o t h e r c o n s t r u c t i o n work has advanced t o

a p o i n t where t h e drying and h e a t i n g devices i n s t a l l e d prevent the temperature v ~ i t h l r i the b u i l d i n g from dropping s u f f ' i c i e n t l y t o a f f e c t the cement vrork detrimeiitillly. Howeve??, should i t become necessary, measures t o p r o t e c t the cement a g a i n s t f r o s t must be talcen a s i n the case of concrete.

I n order t o b u i l d masonry during t h e winter

i t

i s e s s e n t i a l t h a t the b r i c k s be kept a b s o l u t e l y dry, Bricks must be p r o t e c t e d a g a i n s t p r e c i p i t a t i o n i r r e s p e c t i v e of t h e season. Furthermore, d w i r g t h e winter the mortar m u s t be heated.

Taking these m e a s u ~ e s , outdoor b u i l d i n g can be c a r r i e d out a t temperatures doml t o -:.O°C,

JointLng of Zaqade b r i c k s during the winter r e q u i r e s s p e c i a l care, Howerer, i f j o i n t i n g i s postponed t o the sye3ing t h e fagade sliould be p r o t e c t e d , involviw a d d i t i o n a l ea)ense. J o i n t i n g migilt j u s t a s :yell be carraied out simuitaneously wi<;h the l a y i n g of the b r i c k s , provided, of course, t h a t the bric:rs a r e s u f f i c i e n t l y d r y t o absorb t h e water i n the mortar. If a b u i l d i n g is exposed t o the weather, p a r t i c u l a r l y t o t h e wind,

o r i f a b u i l d i n g i s high, j o i n t i n g becomes more hazardous, If j o i n t i n g i s c a r r i e d out i n c o l d weather (and t h i s Is f r e - quently done) the faqade should be covered with t a r p a u l i n s , e t c .

Heated mostar may be obtained a t a small a d d i t i o n a l c o s t , a t l e a s t i n l a r g e r commwliities. The mortar must be kept

heated while the work I s g z i n g on and t h f s can lclz done i n t h ~ e c : d i f f e r e n t ways: ( a ) by .i.nsula-ti~g t h e mortar bed, ( h ) by

h e a t i n g the mortar, and ( c ) 'by iliixilq the mortar with h c t water, ( a ) The mor-kar be(; may be insa1:3ted by p u t t i n g f r e s h horse manure around

it, VarLous

t y - e s o-? insulcitlng

mats, such

a s g l a s s wool mts, styaw rmts, e t c . , may a l s o b e used.. I n a d d i t i o n t o the i n s u l a t i o n tile bed is o f t e n covered overh,

u s u a l l y with t a r p a u l i n s or s h u t t e r s .

The

bed should be kept covered a s much a s possibl.e, e-reli while 1:iorlc i s i n pragrzss.

( b ) There a r e v a r i o u s wzys of h e a t h 2 the mor-:.aT,

A s t r o n g l i g h t c r an e l e c t i - i c element, placed under the pratec- t i v e cover, may be usei3., E-;:LJ,~ a he2 Ling c o i l f-om a t o i l e r p l a n t may be placed untiela the bed ( c f , Big. 1.9).

( c ) Hot water ;-s t h e moat e f f e c t i v e mealis of h e a t i n g the inortar while the 7.atter i s mixed, \Vater proC.aces P1 ,ve tzlrnes a s rnuch h e a t per ~ ~ 1 1 . 3 ns:igh.t a s tlie o t h e r coinponents o f

thz

inortar. Hot n a % r my be ohtaj.lierl. e i t h e r from the b o i l e r p l a n t of the c o n c r s t i r a i n s t a k l a t i o : ~ o r d i r e c t l y frorn a ~ ~ ~ a t e r heatsp,

The mor";ar must. h 3 Icept, s o r t by mechanLcal, stirriilg

( c f . Fig,

27).

Tk:;.s :'.s rr!cri-: Iinportant dlxaing .1;.?-~$ winter 5he.l:- during t h e o t h e r seasons,

The m o p t a r 'ued a?xmL.ii ;7reSerably be kep2 ~,'iliptg a f t e r working hours. FeedLess t:.) say, a l o t can be savc2d i f t?le con-

sumption of mor-Lars Curing ",e v~in.ter can be calculates drirec",iy, because the p r o t e c t i o n of n i o ~ t ~ a r a g a i n s t f ~ o s t during tile night

i n c r e a s e s the t o t a l cos-!,s unnecessarily.

The mortar may be i n s u l a t e d d u ~ i n g the nigli': by

b u i l d i n g the bed i n a she?, T?.e ?-ntter sliould be pr~vfided with an opening so t h a t -&he m.0-+,a? can 3e dwn2ed d.irect3.y from -:rucks

over the bed, which u s u a l l y can be locked and may p o s s i b l y be i n s u l a t e d e x t e r n a l l y , The bed may a l s o be placed on a t h i c k bed of sand, which i s heated by ::tern c o i l s from the b o i l e r p l a n t .

Mortar tubs of wood a r e p r e f e r a b l e during t h e winter. Tin v e s s e l s a r e u n s u i t a b l e , s i n c e the water f r e e z e s rnore e a s i l y Ln them,

The masonry i n a b u i l d i n g under c o n s t r u c t i o n must be p r o t e c t e d a g a i n s t p r e c i p i t a t i o n i n order t o avoid darnage due t o f r o s t and t o f a c i l i t a t e drying, O f course, when t h e work i s i n t e r r u p t e d Lhe rnasonry m u s t be covered over-

Buildings which happen t o be exposed t o i n t e n s e sun- shine on one o r t v ~ o s i d e s should be p r o t e c t e d with t a r p a u l i n s during the winter while the masonry i s being constructed,

Otherwise the mortar might s h r i n k more r a p i d l y i n t h e p s r t ex- posed t o the sun than i n t h e shaded p a r t , r e s u l t i n g i n crooked .:aalls,

The above a p p l i e s not only t o mortar b u t a l s o t o

c l i n k e r masonry, a s well a s conrete-block w a l l s and t i l e d lF?alls, although t h e amount of rnortar per cu.m,. of rnasonry i n the l a s t two c a t e g o r i e s i s smaller.

A f a i r l y nevi technique of c o n s t r u c t i n g w a l l s which seems t o be s u i t a b l e f o r winter c o n s t r u c t i o n i s applied i n t h e so-called p a r a l l e l - b l o c k masonry, This rec-uires a s p e c i a l t o o l which almost resembles an i r o n g r a t e with a container f o r the n o r t a r . The r,lorta.r i s d i s t r i b u t e d through the g r a t e i n the

j o i n t s i n p a r a l l e l strings so t h a t a i r d u c t s rerimin open a s v e r t i c a l s e c t i o n s throughout the e n t i r e wall, The j o i n t thus has t h e same h e a t - i c s u l a t i n g p r o p e r t i e s a s a

r(.

'orated block and the mortar consmiption i s n e g l i g i b l e , Cement mortar i s used

f o r b u i l d i n g with p a p a l l e l blocks, I n order t o harden, t h e cenent m o r t a r must absorb t h e water -c?hich i t previously emitted t o t h e w a l l blcck. Along t h e n e g l i g i b l e conswl]?tion of mortar, t h i s should have a f'avcurable e f f e c t on the drying,

IITTERIOR PLASTER

WORK

I n t e r i o r p l a s t e r i n g during t h e winter i s made es- p e c i a l l y d i f f i c u l t by the f a c t thp't t h e moisture must be

eliminated. To use a popular expression, t h e r e a r e two " s o r t s " o f moisture: water c o ~ t a i n e d i n bthe mortar and water which Forms i n t h e process of carbonization.

Carbonization means t h a t t h e c ~ ( o H ) , combines with GO2 conta'ined i n the atmosphere and fornls CaCO, and H20, I n order t o show how much water forms during carbonization an

e:cmple i s given, assuming t h a t sand-lire rnort:;r i s used. This i s composed of 1 kgm. of lime

+

9

urn.

of sand

+

2.2 k@i. of watei? = 12.2 kgm. molatsr. The lime c o n s i s t s of 90$ of C ~ ( O I I ) , = 0, kg111. Tile carbonization lias t h e following f o r r u l a :

Reaction: Ca(OH),

+

CO, + CaCO, + H200

I f I t i s assumed t h a t t h e carbonization i s complete t h e tt?lount 02 n a t e r produced i s 0.

9

k ~ a . = 0 22 ICLTIF.

CoiripLste car7uonization r e q u i ~ e s a long time arid

i t

i s reason- a b l e to a s s m e t h a t only one-tenth of the lime carbonizes during t h e

time

a b u i l d i n g i s under construction, Hence i n t h e above example oclv 0,022 kpp. of water i s given o f f , i. e.

,

only 1%

of' the water (2.2 km, ) which the mortar was a s s m e d t o c o n t a i 2 i n i t i a l l y and most of which must be ~emoved b e f o r e t h e b u i l d i n g i s occupied,

This shows t h a t the carbonization i s only of secondary importance i n the drying of t h e p l a s t e r . Therefore, t h e supply

of CO, i s :lot i i ~ ~ ~ ~ o ~ t a n t e i t h e r and should have no b e a r i n g on

t h e s e l e c t i o n of t h e drying sgsteix. The removal of the i ~ ~ o i s t u r e i s of' grime importance, Cold a i r <ihsoYbs n :;iuch s m a l l e r amount

of water t!~an ~ : z t ~ r n a i r (cf', p.

7)

+, The rnoicture-absor5ing power

of t h e a i r may 5 e increased by h e a t i n g i t ; t h e a b i l i t y t o re-

ri :lve moisture i s increased by f r e q u e n t chalwes of a i r . There-

f o r e , h e a t and changes of a i r a r e of prime importance i n t h e drying of p l a s t e r .

The measures vhich a r e taken during t h e winter v h i l e i n t e r i o r p l a s t e r work i s c a r r i e d on a r e intended:

( 1 ) t o p r o t e c t and h e a t the p l a s t e r i ' l ~ ~ t l f and ( 2 ) t o p r o v i d e , p r o t e c t i o n and h e a t during t h e

seJctiW Lime

02

t h e p l a s t e r .

(1) P r o t e c t i o n and h e a t f o r . i t h e p l a s t e r i t e z l f

I n l a r , r e r c o i ~ m i t i e s , l~eatscl f i n i s h i n g mo17tar, l i k e r.~ortar Tor >ointilzg, i s d e l i v e r e d t o , t h e b u - i l d i w s i t e a ' ~ a

si;;?.ll a d d i t i o n a l cost. I n orciei? t o p r o t e c t t h e i ~ l o r t z r 5cd and t o ]??at t i e r ~ ? o r t ~ r , \ t h e same rxethocis a r e a p p l i e d h e r e ns i n t h e c:jze of rnort:-ir f o r j o i n t i n g ( c f . .p. 2C).

( 2 ) ? ~ o - l ; e c t i c n and

-

h e a t

-~

du~in:.:. tile s e t t i n g ; til:;e

--

-

~f J. LL>e 7 .:.;l;,.s tt>17

Bef'ore , t h e i n t e r i o r plz.stering begins p r o t e c t i o n ml.sL

S e provided ( a ) by c a s i n g s , and. ( b ) by i r - s t a l l i n g d e v i c e s fo17 d r y i r . tlze p l a s t e r b e f o r e t h e s e t t i n g p r o c e s s begins.

( 3 ) Casings must be used t o prevent t h e escEl.pe of heat l?roducecl by t h e c i r j r i ~ devices. The wind-ow openirgs and

*At terrrperatures bet7::een

+40°

and +60°C, ail7 can absorb e i g h t times a s i ~ u c h moisture a s a t roolii tempernture. ThereiC'ore, the ter;~perr*-L~re should be kept high n e a r newly p l a s t e r e d surfaces.