Journal of the American Concrete Institute, Vol. 17, No. 4

J O U R N A L

V - / w I V l l

1

of the

AMERICAN C O N C R E T E INSTITUTE

(A C I PROCEEDINGS Vol. 4 2 )

Vol. 17 February 1946 No. 4

CONTENTS

Papers and Reports... 277-400

M aintenance of H eavy Concrete Structures— M innesota Power & Light Com­

pany Practice...C L A Y C. BOSW ELL and ALBERT C. GIESECKE 277 Two Special M ethods of Restoring and Strengthening M asonry Structures. . . .

...J. W . KELLY and B. D. KEATTS. 289 Laboratory Studies of Concrete Containing Air-Entraining Adm ixtures...

...CHARLES E. WUERPEL 305 Shrinkage Stresses in Concrete— (Part 2 )...GERALD PICKETT

t 361

Job Problems and Practice ... 401 -404

Influence of M ix in g W ater "H ardness" on Air-Entrainm ent... • >

...CHARLES E. WUERPEL 1 401 Locating Points A lo n g Beam A xis Corresponding to Known M om ents...

...W . C. G O O D W IN 402

5th A nnual Technical Progress Section...405-472

!•

News Letter... 1-20

C O N V E N T I O N P R O G R A M # A C I Aw ards Announced—

John L. Savage, Lewis H . Tuthill, Clarence Rawhouser, Bartlett G . Long, H enry J. Kurtz and Thomas Sandenaw # W ho's W ho # H onor Roll # New Members • Fred F. V an A tta Joins A C I Staff # Aw ards to JPP Contributors # Definitions Pertinent to Concrete #

to provide a comradeship in finding the best ways to do concrete work of all kinds and in spreading that knowledge

A D D R E S S i 7 4 0 0 S E C O N D B O U L E V A R D , D E T R O I T 2 , M I C H .

$7.50 by the year $1.50 per copy

Eilra capiat to mambaii $1.00

Discussion closes March 1, 1946

Sept. JL '45 Concrete Construction in the N atio n a l Forests— C lifford A . Betts

Lapped Bar Splices in Concrete Beams— Ralph W . Kluge and Edward C . Tuma Tests of Prestressed Concrete Pipes Containing A Steel C ylinder— Culbertson W . Ross Field Use of Cement Containing V insol Resin— Charles E, W uerpel

N ov. Jl. 45 M aintenance and Repair of Concrete Bridges on the O regon H ighw ay System

— G. S. Paxson

Should Portland Cement Be Dispersed?— T. C. Powers

A n Investigation of the Strength of W elded Stirrups in Reinforced Concrete Beams—

O reste M oretto

Discussion closes A p ril 1, 1946

Jan. Jl. *46 Shrinkage Stresses in Concrete— G erald Pickett

Floating Block Theory in Structural A nalysis— Stanley U. Benscoter

Shrinkage and Plastic Flow o f Pre-Stressed Concrete— H o w a rd R. Staley and Dean Peabody, Jr.

Proposed M inim um Standard Requirements for Precast Concrete Floor Units— A C I Committee 711

Proposed Recommended Practice for the Construction of Concrete Farm Silos— A C I Committee 714

Discussion closes June 1, 1946

Feb. Jl. '4 6 M aintenance of H eavy Concrete Structures— M innesota Power & Lig h t Com pany Practice

C lay C. Boswell and A lb e rt C. Giesecke

Two Special M ethods of Restoring and Strengthening M asonry Structures— J. W . Kelly and B. D. Keatts

Laboratory Studies of Concrete Containing A ir-E ntraining Adm ixtures—

Charles E. W uerpel

Shrinkage Stresses in Concrete— (Part 2)— G erald Pickett

J O U R N A L

o f the

AMERICAN CONCRETE INSTITUTE

Published by the American Concrete Institute. The Institute was founded 1905/ incorporated in the District of Columbia in 1906 as The N ational Association of Cement Users/ the name changed 1913 by charter amend- reincorporafec^r new statement of objects, August 8, 1945.

The Journal is issued six times yearly in the months o f January, February, A p ril, June, September and November under the authority of the

BOARD OF DIRECTION, AMERICAN CONCRETE INSTITUTE

President D O U G LAS E PARSONS

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Directors-at-Large

H ARRY F. T H O M S O N ROBERT F. BLANKS H ENRY L. KENNEDY Past Presidents

RODERICK B. Y O U N G R A Y M O N D E. D A V IS

BEN MOREELL M O R T O N O . W ITH E Y

R O Y W . CRUM

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is edited by the Secretary of the Publications Committee under the direction of the Committee

ROBERT F. BLANKS

Chairman

D O U G LA S E. PARSO NS

(ex-officio)

R. D. BRADBURY HERBERT J GILKEY

A . T. GOLDBECK H A R R ISO N F. G O N N E R M A N

FRANK H . JA C K S O N W . H . KLEIN S T A N T O N W ALKER RODERICK B. Y O U N G

H A R V E Y W HIPPLE

Secretary

It is the po licy of the Am erican Concrete Institute to encourage participation by its members and others in the work of extending the knowledge of concrete and reinforced concrete as a basis for improved products and structures.

To this end the Board of Direction has assigned to the Publications Committee the responsibility of selecting for publication such papers, committee reports, discussions and other contributions or parts of such contribu­

tions, as in the iudgm ent of the Committee, seem to offer most of value in attain ing Insti­

tute objectives within space requirements consistent with budget lim itations.

A M E R IC A N CONCRETE INSTITUTE

N E W CENTER BUILDING DETROIT 2, M IC H IG A N

R h s /$ Q

/ /

[

Title 42-13 — a part of PROCEEDINGS, A M E R IC A N C O NC RETE INSTITUTE V o l. 42

J O U R N A L

of the

A M E R I C A N C O N C R E T E I N S T I T U T E

(copyrighted)

V o l. 1 7 N o. 4

February 1946

M a in te n a n ce of H e a v y Concrete Structures

M in n e so ta Pow er & Lig h t C o m p a n y P ra ctice *

By CLAY C. BOSWELLt

Member American Concrete Institute

and ALBERT C. GIESECKEt

S Y N O P S I S

The practice of The M innesota Power & Light Company in repair­

ing and restoring a concrete dam is described and illustrated and com­

parisons made w ith a much older structure, which has had no repair cost because construction methods were better.

T h e sev erity of th e clim ate in th e area of th is c o m p an y ’s operations produces a less freq u en t, b u t m ore severe ty p e of frost dam age, th a n t h a t w hich occurs in a m ilder clim ate in th e presence of a fre q u e n tly re­

occuring “ cycle of freezing-thaw ing” , such as is usu ally associated w ith concrete d isin te g ratio n problem s.

I t is th e deeper p e n e tra tio n of frost, in to such concrete stru c tu re s as are v u ln era b le to its d am aging effects, w hich form s im p o r ta n t reason for th e p ractice developed by th e M in n eso ta P ow er & L ig h t C om pany, a n d w hich lends su b sta n tia l m eaning to th e te rm “ h ea v y concrete re­

p a ir sla b ” as p ic tu re d in th is article.

T h e p ra ctice of th is co m p an y in dealing w ith problem s of th is ty p e d a te s b ac k to 1926 w hen th e first m ajo r w ork of sim ilar c h a ra c te r was done. A n u m b e r of com parable ap p licatio n s h av e since been m ade.

Ages of tw o m a jo r ap p licatio n s are ap p ro ac h in g 18 years, a n d resu lts to d a te are m o st satisfacto ry .

In no sense is it th e a u th o r ’s suggestion th a t th e m eth o d s herein described be a d o p ted in to to for o th e r co n d itio n s; in ste a d it is his con­

v ic tio n t h a t conditions p rev ailin g a t each s itu a tio n will re q u ire local decisions as to —

♦R eceiv ed b y th e I n s tit u te N ov. 5, 1945.

fV ice P re s id e n t a n d C h ie f E n g in eer, M in n e so ta P o w e r & L ig h t C o m p a n y , D u lu th .

^ H y d ra u lic E n g in eer, M in n e s o ta P o w er & L ig h t C o m p a n y , D u lu th .

(277)

1. D esign of d eta ils of slab a n d reinforcing.

2. D esign of co n crete mix.

3. Spacing an d d e tail of c o n stru c tio n jo in ts.

F O N D DU L A C H Y D R O ELECTRIC S T A T IO N D A M

If proof w ere w a n te d as to w h e th e r v a ria tio n s in te c h n iq u e used b y th e b u ild er can m ake th e difference b etw e en a concrete dam o f good quality, as a g a in st one in w hich m a in te n a n c e is a m a jo r ite m , i t w o u ld be av ailab le b y th e sim ple process of in sp e c tin g th e T h o m so n D a m a n d th e F o n d d u L ac D am , b o th on th e St. L ouis R iv er, M in n e so ta , w hich, a t th is d ate, are 39 a n d 21 y ears old, resp ectiv ely .

T h e excellent co n d itio n of th e T h o m so n D a m w as reco g n ized in 1928 w hen it w as described b y H . C. Ash, in th e A C I Proceedings, V. 25 of 1929.

S uch lack of e ru d itio n as m a y h a v e h in d e re d th e effo rts of th e b u ild e rs of T h o m so n D am , w as in am ple m easu re offset b y d ilig e n t a p p lic a tio n of sim ple fu n d a m e n ta ls. T h e y used clean ag g re g a te ; m ixed ag g re g a te as densely as possible b y com bining p it g rav el a n d la k e g rav el; th e y cleaned d ays-w ork planes, a n d , in th e w ords of M r. A sh “ d ry co n c re te req u irin g m u ch ta m p in g , a n d free w a te r on th e su rface of p la c e d con­

crete, w ere b o th discouraged w ith em p h a sis.” T h e concrete, ac c o rd in g to M r. A sh, ap p ro x im a te d p ro p o rtio n s of 1 :1.7:4.3.

T h e F o n d d u Lac co n crete w as cru sh ed sto n e a n d p it san d , b o th of w hich w ere clean a n d so u n d . T h e m ix w as g en erally 1:3:6 a n d m o st con crete w as p laced b y a sy stem of ch u tes. G ood p ra c tic e w as v io ­ la te d , p rin c ip a lly in th e w ide v a ria tio n a n d excessive use of m ixing w ate r, w ith co n seq u e n t gross seg re g atio n w hich now is th e o b v io u s nucleus of m o st of th e w eakness re q u irin g rem ed y w ith in th e d ecad e e n d in g a p p ro x im a te ly as th e s tru c tu re reach es th e en d of its first 25 y ea rs of service.

T h e 39-year-old T h o m so n D am is in e sse n tia lly a p e rfe c t s ta te of p re ­ se rv a tio n w ith no con crete m ain ta n e n c e expense “ a f t ” or “ fo rw a rd .” T h e 21-year-old F o n d d u L ac D am , how ever, will, b efo re i t is 39 y e a rs old, h a v e in v o lv ed s u b s ta n tia l m a in te n a n c e co sts in a d d itio n to th o se a lre a d y incurred.

The Fond du Lac maintenance problem

Signs of im p en d in g co n crete m a in te n a n c e p ro b lem s w ere seen as e a rly as 1928, w hen th e d am w as b u t 4 y e a rs old, a t w h ich tim e d is in te g ra tio n was, in m inor degree, n o tic eab le in th e ta in to r g a te w a te rw a y s. T h is w as th en , how ever, considered “of no im m ediate c o n c e r n G re a te r con­

cern was fe lt over th e co n d itio n of tw o g a te piers. Fig. 1, on close ex am in atio n , will reveal t h a t s u b s ta n tia l ev id en ce of d isin te g ra tio n w as

Fig. 1 (above)— Downstream face of Fond du Lac Dam showing taintor gates numbers 4 to 1 7 inclusive. September, 1928

Fig. 2 (right)— Downstream face of Fond du Lac Dam in area of gates 8, 9 and 10. June 1936

visible on th e d o w n stream face of th e dam , even w hen view ed from several h u n d re d feet aw ay.

Condition in 1 936

Fig. 2 shows th e condition n ear ta in to r gates 8, 9 a n d 10 in Ju n e 1936.

Also, in O ctober, careful field inspection revealed ta in to r g ate w aterw ay spalling as show n on Fig. 3. T h e lesser d e p th of spalling in ta in to r gate 16, a n d a t several a d ja c e n t ones, is acco u n ted for, a t least in p a rt, b y th e less fre q u e n t discharge th ro u g h th ese g ates as com pared w ith th o se n ear th e m iddle of th e dam .

A t th is p o in t, records of original co n stru ctio n were review ed a n d it w as fo u n d t h a t concrete specifications w ere com plied w ith, except as to

C R O S S S E C T IO N OF D A M

SEAT5 OF TAINTOR GATES

S E C TIO N S A T L O C A T IO N S IN D IC A T E D

LEG EN D A S TO S U R FA C E C Q N O ITIQ N

Of DISINTEGRATION WAS ACTUALLY MEASURED H -X -H ORIGINAL SURFACE ENTIRELY GONE

n-Y—-H ORIGINAL SURFACE PARTLY GONE ORIGINAL SURFACE SUBSTANTIALLY INTACT H-XY--4 IRREGULAR PATCHES OF CONDITIONS X A N O Y f-X i-H IRREGULAR PATCHES OF CONDITIONS X AND *

»•-Yi-w IRREGULAR PATCHES OF CONDITIONS Y A N O Î

Fig. 3— Part record of inspection of downstream face of Fond du Lac Dam in O ctober, 1936

MAINTENANCE OF HEAVY CONCRETE STRUCTURES

Fig 4— Downstream face of Fond du Lac Dam in area of first concrete restoration. O ctober, 1940

lav ish use of m ixing w a te r; com pressive stre n g th te sts were m ade as th e w ork progressed, an d th ese should hav e been w arn in g enough to call for corrective m easures. T h e ch u tin g system of placing concrete was th e occasion for excessive a n d v ary in g m oisture co n ten ts, a n d th is re­

su lted p a rtly in defective conditions th ro u g h o u t large areas, a n d else­

w here in lenses of poorer concrete (and even sh eet laitan ce) in tersp ersed inside m asses of som ew hat b e tte r q u ality .

Repair program

F a c to rs outside th e F o n d du Lac D am were largely responsible for a d o p tin g th e p lan to w hich th e job read ily le n t itself, nam ely, dividing th e re p a ir job in to 3 blocks, one each for 1940, 1945 a n d 1948. T h is p ro g ram p e rm itte d th e w ork to be k e p t w ith in th e cap a c ity of th e c o m p a n y ’s rep air crew, staggered w ith th e periods in w hich sim ilar w ork elsew here h a d to be done. F u rth e r it accom m odated in b e st possible degree, th e coordination necessary betw een w ork of th is kind an d th e req u irem en ts of pow er production.

1940 repair work

T h e area re sto red in 1940 is in d icate d on Fig. 3, as well as in Fig. 4, w hich shows th e form s still in place a t ta in to r gates 14 a n d 15, an d in th e rig h t foreground, th e in tersp ersio n of w eaker lenses in otherw ise fa irly sou n d concrete. In th e d istance, (as well as a t th e u p p e r rig h t corner), th e generally poor areas form ing p a rts of su b seq u en t rep air blocks is sh o w n .

Fig. 5— Downstream face of Fond du Lac Dam showing details o f construction. O ctober, 1940

M e th o d s of d ealing w ith sim ilar problem s, d ev elo p ed on o th e r s tr u c ­ tu re s as m u ch as 14 y e a rs earlier, w ere a p p lied a t F o n d d u L ac in 1940, a n d a t th is d a te , no in d ic a tio n of fa ilu re h a s m a n ife ste d itself. W h ile necessarily th e re m e d y inv o lv es a cover o v er larg e areas, th e co v er is in no sense a “ v e n e e r” because it is fa r to o h e a v y to b e so d esig n ated .

D etail of heavy concrete repair slab

T h e co n cep t of a “ h e a v y re p a ir s la b ” is d esc rip tiv e of th e s u b s ta n tia l th ick n ess of reinforced co n crete w hich we use to t r e a t su ch a surface.

T h e slab is u su ally specified to h a v e a t le a st 24 in. a v erag e th ic k n e ss a n d well reinforced w ith reinforcing co n n ected m ech an ically b y ho o k s to th e dow el rods, w hich, in tu rn , b y w edge a n d , or g ro u t, p ro v id e a n c h o rag e to th e u n d erly in g concrete a t d e p th b e y o n d th e reach of fro st p e n e tra tio n .

A t F o n d d u Lac th e v e rtic a l c o n stru c tio n jo in ts in th e re p a ir slab w ere spaced on th e ce n ter line of each ta in to r gate. T h is p laced a re p a ir slab jo in t a t each of th e original s tru c tu re jo in ts w hich o ccu rred a t c e n te r lines of a lte rn a te gates. T h e p lacing of con crete w as carried fro m th e b o tto m to th e v e ry to p of each section as a co n tin o u s o p eratio n .

T h e new co n crete is d ep o sited on su rfaces g en erally sc ru b b e d b y a h ea v y s p ra y of high p re ssu re a ir a n d w ater;, th e n , sh o rtly before con­

c re te is p laced , a g ro u t w ash is ap p lied . All co n crete is of clean, sound a g g reg ate, of s ta n d a rd p o rtla n d c em en t (w ith o u t a d m ix tu re or air e n ­ tra in in g a g en t) a n d w a te r sufficient to p ro d u c e th e m in im u m slu m p con­

s is te n t w ith p lacin g th e co n crete w ith o u t h o n ey-com bing. O u r general p ra c tic e is to use a b o u t 6 to 6 ^ bags of s ta n d a r d p o rtla n d c e m en t p er

MAINTENANCE OF HEAVY CONCRETE STRUCTURES

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NEW CONCRETE 16' M IN IM U M & 24

AVERAGE TH IC KNESS D O W ELS W ITH SHORT

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W IT H W EDGE A N D /O R GROUT

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EL 61 3 O

.HO O KED DOWELS

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C O N S T R U C T I O N J O I N T . O L D P A R T r .N E W P A R T

¿ .R E S T O R E D R O LL W AY SURFACE

C O N S T R U C T IO N J O IN T

T A I N T O R G A T E R O L L W A Y

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G R A V IT Y S E C T I O N R E T A IN IN G W A L L

Fig. 6 — Drawing from specifications governing the 1940 concrete restoration at Fond du Lac Dam

Fig. 6a, upper left; 6b, upper right; 6c, lower right; 6d, lower left

cubic y a rd a n d in te rn a l v ib ra tio n is re so rte d to w herev er it can be ap p lied . I n curing green concrete, th e u su al p recau tio n s of a p p ly in g am ple m o istu re are observed for from six to eig h t days.

Fig. 5 shows m an y item s of in terest. A t th e extrem e rig h t edge, new concrete from w hich form s have a lre ad y been rem oved is visible. N e x t is th e large area in w hich concrete is being placed, while on th e left is an are a w hich is being readied for concrete, w ith panel form s covering a p o r­

tio n of th e area, an d leaving to view th e a rra n g e m en t of dowels a n d rein ­ forcing bars, as well as giving in d icatio n of th ick n ess of th e concrete slab being provided. Fig. 6 shows th e d etails in draw ing form .

EL 6 8 7 0 W S E L 682

E A R T H FILL HO O K D O W E LS

I' R O D S AT 3F T ON CENTERS Vt RODS AND

Fig. 7— V ie w of 1940 concrete in the right foreground and of a disintegrated area beyond the center line of gate 1 5, which is scheduled for 1945 restoration.

July, 1945

Fig. 8— Typical pond face disintegration on vertical walls at Fond du Lac dam ; trash

gate pier to right of staff gage. September, 1941

MAINTENANCE OF HEAVY CONCRETE STRUCTURES

Fig. 9 — Typical pond face restoration, showing in profile, the pier appearing on Fig. 8.

Fig. 6a show s th e a rra n g e m en t of dowels a n d reinforcing steel. I t also in d icates th e po sitio n an d m a n n e r of placing steel colum ns a t th e heel of th e ta in to r g ate pier. Such a steel colum n is p a rtly visible beh in d th e in co m p leted form s in Fig. 5.

F ig 6b show s d e ta il a t location of original co n stru ctio n joints.

1945 repair work:

W ork scheduled for 1945 em braced d o w n stream face areas, as well as p o n d face item s. F ig 6c shows d etails of re sto ra tio n of th e forebay re tain in g wall, an d Fig. 6d shows m an n er of dealing w ith w a te r line d isin te g ra tio n .

Fig. 7, a t th e left, shows a n are a scheduled for tre a tm e n t in 1945, a n d a t th e rig h t, a large p a r t of th e 1940 work. T h e d iv id in g line betw een th e se tw o areas is th e ce n te r line of ta in to r g ate 15.

Fig. 8 show s w a te r line d isin te g ra tio n suffered a t th e pon d face. T h is p a rtic u la r view show s th e tra s h g a te pier ju s t to th e rig h t of th e staff gage, a n d th e m a n n e r of tre a tm e n t given it is in d ic a te d in Fig. 9 w hich show s th e sam e tra s h g ate pier in profile.

I availab le from A C I a t 25 cents each— quantity quotations on request. Discussion L o f this paper (copies in triplicate) should reach the Institute not later than M a y 1, 1 9 4 6 J

Title 42-14 — a part of PROCEEDINGS, A M E R IC A N C O NCRETE INSTITUTE V o l. 42

o f the

A M E R I C A N C O N C R E T E I N S T I T U T E

(copyrighted

V o l. 1 7 N o. 4

February 1946

Tw o S p e cia l M ethods of Restoring a n d Stren g th en in g M a so n ry Structures*

By J. W. KELLYf and B. D. KEATTSt

Members American Concrete Institute

S Y N O P S I S

S tructures and foundations damaged by weather, erosion, scour, or settlem ent have been restored and strengthened by ingenious methods involving the pum ping of cement-base stabilizing m aterial into small interstices and the filling of larger spaces by aggregate which is then em bedded in the stabilizing m aterial under pressure. H erein are des­

cribed several applications of the methods to various structures in­

cluding bridge piers an d abutm ents, reservoirs, dams, and underw ater construction.

IN TR O D U C T IO N

I t h as been well said t h a t g reate r engineering skill is req u ired to re sto re an old s tru c tu re th a n to b u ild a new one. C e rta in ly re sto ra tio n challenges th e engineer a n d calls for a high degree of experience an d in g en u ity . H ow ever, it is th e only so lution to m a n y problem s w here th e use of th e s tru c tu re m u st n o t be in te rru p te d a n d w here th e cost of rem o v al a n d rep lace m en t w ould be p ro h ib itiv e.

M a n y cu t-sto n e s tru c tu re s on th is c o n tin e n t are now alm o st a cen­

tu r y old, a n d m a n y concrete s tru c tu re s are a b o u t a h a lf-c e n tu ry old.

As a class th ese stru c tu re s are d u rab le a n d stab le, b u t one need n o t go fa r to find m a n y t h a t are in need of tre a tm e n t. Som e are defective because of fa u lty design or co n stru ctio n re su ltin g in p o ro sity , h o n ey ­ com bing, laitan ce, or cracking. O thers, even if well b u ilt, are in u n ­ s a tisfa c to ry co n d itio n because of severe w eath erin g , leaching, cracking, or exposure to fum es or o th e r corrosive ag en ts. F o u n d a tio n s h av e been su b je c t to scour a n d to u n e v e n se ttle m e n t. I n m a n y cases th e live loads

* R eceiv ed b y th e I n s tit u te , D ec. 3, 1945.

tA s s o c ia te P ro fesso r of C iv il E n g in e e rin g , U n iv e rs ity of C alifo rn ia . JE n g in e e r, I n tr u s io n - P r e p a k t I n c ., C le v ela n d .

(289)

h a v e increased fa r b ey o n d th e original design loads, a n d new uses of th e s tru c tu re h av e b een developed.

Special a tte n tio n to th ese co n d itio n s h a s long been given b y th e c o n stru ctio n o rg an izatio n s whose w ork is describ ed herein, a n d h u n d re d s of s tru c tu re s h av e been re co n d itio n ed th ro u g h th e use of tw o special tech n iq u es developed n o t only b y field experience b u t also b y ex ten siv e la b o ra to ry research. W hile th e se are p ro p rie ta ry processes, th e ir a p p li­

catio n h as been so w id esp read a n d so co n siste n tly successful t h a t a fa c tu a l a c c o u n t of th e ir general n a tu r e a n d ty p ic a l a c co m p lish m en ts will be of in te re s t to all w ho h av e th e re sp o n sib ility for th e m a in te n a n c e a n d re p a ir of m aso n ry stru c tu re s.

In o rd er to av o id re p e titio n in th e d escrip tio n s of th e w o rk on in ­ d iv id u a l stru c tu re s, it is d esirable first to explain th e tw o g eneral processes, in tru sio n a n d prepacking.

IN TR U S IO N

B riefly, th e in tru sio n process of stab ilizin g a s tru c tu re or fo u n d a ­ tio n consists in drilling holes a t in te rv a ls a n d in je c tin g an in tru sio n m ix ­ tu r e w hich consists of p o rtla n d cem en t, a po w d ered m in e ra l filler, an in tru sio n aid, w a te r, a n d in som e cases a fine sand. T h e m a te ria ls an d p ro p o rtio n s are n ecessarily v a rie d to m e e t th e p a rtic u la r co n d itio n s, w ith in lim its w hich are esta b lish e d b y la b o ra to ry te s t a n d field ex­

perience. F e a tu re s of th e process a re th e c h a ra c te ristic s of th e in tru s io n m ix tu re, special fittin g s a n d connections fo r in tru sio n , th e sequence of solidifying v a rio u s p o rtio n s of th e m ass, a n d th e d e te rm in a tio n of a d e q u a te p e n e tra tio n .

T h e m in era l filler used in th e in tru sio n m ix tu re is a finely d iv id ed siliceous m a te ria l called Alfesil. I n th e fresh m ix tu re i t te n d s to p re v e n t ag g lo m eratio n of th e grains of p o rtla n d c em en t a n d th u s in creases th e ir effectiveness. In th e h a rd e n e d m ix tu re , i t com bines w ith lim e lib e ra te d b y th e h y d ra tin g p o rtla n d c em en t to fo rm calcium silicates w h ich a re re la tiv e ly insoluble a n d w hich c o n trib u te to stre n g th . T h e effect of th is puzzolanic m a te ria l becom es e v id e n t in th e considerable d e v e lo p m e n t of s tre n g th a t la te r ages, a fte r a slow s ta rt.

T h e in tru sio n aid, or a g e n t as it is com m only called, is u sed p rim a rily fo r th e p u rp o se of in creasin g th e p u m p a b ility o r flow ability of th e m ix ­ tu re th ro u g h th e ex trem ely sm all crevices a n d voids w h ich m u s t be tra v e rs e d to secure th o ro u g h p e n e tra tio n of th e s tru c tu re b y th e solidi­

fy in g m a te ria l. T h e a g e n t also assists in disp ersal of th e c em en t g rain s, a n d to g e th e r w ith th e filler it reduces s e ttle m e n t a n d e lim in a te s e a rly sh rin k ag e of th e m ix tu re a fte r it reaches its final lo catio n in th e v o id spaces. N u m ero u s te s t specim ens c u t from s tru c tu re s w hich h a v e been

Fig. 1.— To prepare for intrusion, holes are drilled throughout structure and foundation.

RESTORING AND

in tru d e d show t h a t th e spaces rem ain com pletely filled, w ith o u t th e p a rtia l se p a ra tio n from th e w alls an d to p of th e c a v ity t h a t is o ften observed in th e case of p o rtla n d -c e m en t grouts.

E ac h stru c tu re p re se n ts d istin c tiv e problem s, b u t in general th e process of in tru sio n involves th e follow ing steps. H oles are drilled a t v a rio u s in te rv a ls an d to v ario u s d e p th s as re q u ired b y th e co n d itio n of th e s tru c tu re (Fig. 1). C are is of course ta k e n n o t to d am ag e th e s tru c ­ tu re . B efore a given section is tre a te d it is te ste d u n d e r w a te r pressure in o rd er to d eterm in e w h e th e r th e drilling is a d e q u a te a n d to select th e pro p er consistency of th e in tru sio n m ixture.

T h e in tru sio n m ix tu re is th o ro u g h ly m ixed b y m echanical stirrin g and a g ita tio n u n til a sm o o th slu rry is o b ta in e d (Fig. 2). W here a high degree of p e n e tra tio n in to sm all voids an d passages is req u ired , th e m ixing tim e m a y be as m u ch as 20 m in u tes. T h e m ix tu re is a g ita te d c o n tin u ally in o rd er to keep it uniform .

T h e in tru sio n m ix tu re is in jec ted b y p u m p in g u n d e r pressure sufficient to secure th o ro u g h p e n e tra tio n of th e s tru c tu re w ith o u t disp lacem en t of s tru c tu ra l p a rts (Fig. 2). T h e sequence of filling th e v ario u s holes and, if necessary, th e v a rio u s d e p th s in a given hole, is such as to expel th e w a te r a n d a ir from th e cav ities a h ead of th e in tru sio n m ixture. W hen no

Fig. 2 .— M a terials from platform (center) are meas­

ured into m ixing tanks.

Piston pumps at left force in tru s io n mi x t u r e in to structure.

Fig. 3.— A special ex­

panding connection called

an intrusion insert is used to

connect pressure hose to

hole.

Fig. 4.— Piece of concrete cut from disintegrated tun­

nel lining 70 ft. from nearest point of intrusion. N ote penetration of intrusion m aterial (solid gray) into old structure.

ad d itio n a l m a te ria l can be in tru d e d im m ediately, pressure is m a in ­ ta in e d long enough to in su re a n y ad d itio n a l p e n e tra tio n t h a t m a y be m ad e possible b y slow flow of th e m ix tu re in to cavities. T h e th o ro u g h ­ ness of p e n e tra tio n a t a n y given hole is ju d g ed b y th e inflow in re la tio n to c onditions observed d u rin g th e drilling, b y th e pressure a t w hich in tru sio n stops, a n d b y th e show ing of in tru sio n m ix tu re a t d is ta n t cracks or o th e r openings. W hen necessary, a d ja c e n t openings are calked to p re v e n t loss of in tru sio n m aterial. A special ex p an d in g con­

nectio n has been developed to connect th e pressure hose q u ick ly an d tig h tly to th e drilled holes (Fig. 3).

T h e re su lts o b ta in e d b y in tru sio n becom e e v id e n t in th e perform ance of th e stru c tu re . If th e stru c tu re is one w hich is exposed to w a te r u n d e r pressure, th e re su lts can b e observed v isu ally a t once. T h e a m o u n t of m a te ria l in tru d e d is of course one m easure of solidification. S u rp ris­

in g ly large a m o u n ts can o ften be in jec ted in to stru c tu re s w hich on th e surface a p p e a r to be fairly sound (Fig. 4). T e s t cores m a y be ta k e n to pro v e th e com pleteness of p e n e tra tio n a n d to d eterm in e th e stre n g th .

T e sts for s tre n g th a n d o th e r physical p ro p erties of th e in tru sio n m ix tu re itself h a v e been m ad e b y a n u m b e r of lab o rato ries. I t m u st be em phasized t h a t th e m ix tu re s are n o t sta n d a rd iz e d b u t are p ro p o rtio n e d to m eet th e req u ire m e n ts of th e p a rtic u la r job, a n d t h a t a n y stre n g th equal to t h a t of com parable concretes can be produced. In one series of te sts, 2-by 4-in. cylinders a n d s ta n d a rd tensile b riq u e ts w ere m olded from a m o rta r w hich co n tain e d equal p a rts b y w eight of in tru sio n p aste an d sand, w ith a ra tio of w a te r to cem ent plus Alfesil of 0.47 b y w eight.

T h e specim ens w ere stan d a rd -c u red . T h e follow ing stre n g th s w ere o b tain ed .

7 day 28 day 3 mo. 1 yr.

Compressive strength, p s i... 2510 4200 6860 9090 Tensile strength, psi... 330 465 505 590

C o m p a ra tiv e te s ts of in tru sio n p a ste s w ith p o rtla n d -c e m e n t g ro u t of e q u al consistency disclose (1) t h a t th e b leeding of th e in tru sio n p a ste is negligible w hereas u n d e r th e sam e co n d itio n s th e p o rtla n d -c e m e n t g ro u t bleeds as m u ch as 4 p e r ce n t of w a te r b y v o lu m e; (2) th e in tru sio n p a ste q u ick ly passes th ro u g h glass tu b e s filled w ith coarse san d , w hich c a n n o t be p e n e tra te d w ith p o rtla n d -c e m en t g ro u ts of co rresp o n d in g co n sisten cy ; an d (3) th e v o lu m etric sh rin k ag e d u rin g th e first 24 h o u rs is fa r less fo r th e in tru sio n p a ste th a n for th e p o rtla n d -c e m e n t g ro u t.

T o sum m arize, th e in tru sio n m ix tu re m a in ta in s th e solids in su s­

pension, flows easily a n d w ith o u t plugging, is low in s e ttin g sh rin k ag e, an d develops in th e cav ities a dense stro n g p a s te tig h tly b o n d ed to th e walls.

PR EPAC KING

P re p a k t is concrete m ad e b y p ack in g th e form s w ith coarse a g g reg ate an d th e n p u m p in g in a cem en t-b ase in tru s io n m ix tu re to fill th e voids u n d e r pressure. I t is used b o th for re s to ra tio n an d , in special cases, fo r new co n stru ctio n .

One p rin cip al p u rp o se of p lacin g th e a g g reg a te in a d v a n c e is to b rin g th e pieces of ag g reg ate in to c o n ta c t or n e a r-c o n ta c t, w ith o u t th e clear­

ance w hich is req u ire d for p la stic ity in o rd in a ry concrete. B y th is arra n g e m en t, even if th e in te rv e n in g m o rta r w ere n o rm a l in d ry in g - sh rin k a g e c h a ra cteristics, overall sh rin k ag e of th e co n crete w ould be re la tiv e ly low because th e pieces of coarse ag g re g ate a re in c o n ta c t w ith one an o th e r. W h en th e coarse ag g reg ate is s u ita b ly g ra d e d th e v o id spaces are re la tiv e ly low, w ith co rresp o n d in g ly low re q u ire m e n t of m o rta r a n d th erefo re cem ent. T h e low cem en t c o n te n t, to g e th e r w ith th e slow -hardening c h a ra c te ristic s of th e in tru sio n m ix tu re , m a k e for low a n d slow h e a t gen eratio n , w hich is of im p o rta n c e in m ass concrete.

P ack in g th e ag g reg ate in a d v a n c e also fa c ilita te s p lacin g in difficult locations, a n d p e rm its in sp ectio n before co n c re tin g in o rd e r to assure com plete filling of th e form s.

As in th e case of in tru s io n m ix tu res, th e s tre n g th of P r e p a k t con­

crete is m ad e to m e e t th e jo b re q u ire m en ts. T h e a v erag e com pressive s tre n g th of 32 P re p a k t co n cretes fo r w hich reco rd s are c o n v e n ie n tly av ailab le, te s te d in th e fo rm of 6- b y 12-in. cylinders, w as 2,200 psi a t 7 d ay s, 3,540 psi a t 28 days, a n d 4,330 psi a t 3 m o n th s. Som e of th e se concretes a tta in e d a com pressive s tre n g th of 3,200 psi a t 7 d a y s a n d 6,700 psi a t 3 m o n th s. T h e d ry in g sh rin k ag e of P r e p a k t co n crete is less th a n t h a t of o rd in a ry con crete of th e sam e c e m en t c o n te n t, a n d th e re sista n c e to crack in g is corresp o n d in g ly high. R e sistan ce to w e a th e rin g h as been e stab lish ed as s a tisfa c to ry n o t only b y accelerated la b o ra to ry te s ts b u t

RESTORING AND STRENGTHENING MASONRY STRUCTURES

also b y field experience u n d e r several y ears of exposure. As in regular concrete, resistan ce to freezing an d th a w in g m a y be m a rk e d ly im p ro v ed th ro u g h th e use of a ir-e n tra in in g agents.

T h e bon d s tre n g th of P re p a k t concrete to reg u la r concrete, te ste d in th e fo rm of beam s jo in te d a t m id sp an , w as fo u n d to be a b o u t 65 per cent g re a te r th a n t h a t for reg u lar concrete c a st a g a in st reg u lar concrete;

in fa c t, it w as a b o u t 70 p e r ce n t of th e s tre n g th of corresponding u n ­ jo in te d beam s of reg u lar concrete. In freezin g -an d -th aw in g te s ts of P re p a k t concrete cast a g a in st air-e n tra in ed reg u lar concrete, th e jo in t betw een th e tw o p o rtio n s rem ain ed in ta c t even a fte r severe d isin te g ra ­ tio n of th e concretes them selves h a d ta k e n place.

T h e general process of re sto ra tio n w ith P re p a k t is illu stra te d in Fig.

5a to 5c. D efectiv e concrete of th e stru c tu re is chipped out, a form is applied, a n d th e space b eh in d th e form is packed tig h tly w ith coarse aggregate. In tru s io n m ix tu re is p u m p ed in and, u n d e r pressure, n o t only fills th e spaces w ith in th e p rep ack ed aggregate b u t also p e n e tra te s in to th e pores of th e u n d erly in g surface a n d in to conn ectin g cracks a n d void spaces. T h e cem enting to a n d stab ilizin g of th e u n d erly in g m ass is a d istin c tiv e fe a tu re of th is m eth o d of repair.

N ew co n stru ctio n w ith P re p a k t is perform ed in a sim ilar m anner, w ith m odifications as necessary. F o r exam ple, in a larg er m ass th e in ­ tru sio n in lets w hich are placed a t in te rv a ls h o rizo n tally a n d v ertic a lly m ay be p e rfo rated pipes em bedded w ith in th e ag g reg ate; a n d th e in ­ tru sio n m ix tu re m a y be in jected successively a t v ario u s elevations. F o r u n d e rw a te r w ork it is u su ally n o t n ecessary to u n w a te r th e stru c tu re . T e sts in field a n d la b o ra to ry h a v e show n re p e a te d ly t h a t th e rising m ass of in tru sio n m ix tu re displaces th e w a te r w ith o u t m ixing w ith it, a n d t h a t sa tisfa c to ry s tre n g th s an d densities are u n iform ly o b tain ed . Fig. 6 shows one la b o ra to ry te s t in progress; in tru sio n m ix tu re is being forced in a t th e low er left edge of th e form an d is rising th ro u g h to lj^ - in . agg reg ate prev io u sly subm erged in w ater. I n co m p arab le te s ts w ith p o rtla n d -c e m en t g ro u t, th e zone of d e m a rk a tio n betw een g ro u t an d w a te r is cloudy, an d segregation a n d d ilu tio n of th e g ro u t occur.

A P P L IC A T IO N S

On m a n y piers of th e older railw ay bridges, surface d isin te g ra tio n has o ccurred due to w eath erin g p a rtic u la rly a t th e w a te r (an d ice) lines.

Fig. 7a a n d 7b show re sto ra tio n in a ty p ica l case. F ir s t th e fo u n d atio n ro ck a n d th e m a so n ry base of th e p ier w ere in tru d e d . T h e n th e in ­ te rio r, w hich w as filled w ith loose rock, w as solidified as well as th e m o rta r jo in ts. D efective p o rtio n s'o f th e concrete p e d estal cap an d th e facing sto n es w ere rem oved a n d replaced w ith P r e p a k t co n crete; i t w as

n ecessary to c a st a P re p a k t b la n k e t co m p letely a ro u n d th e low er p o rtio n . In a n o th e r s tru c tu re th e p ier footings w ere ex te n d ed d o w n w ard a n d o u t­

w a rd w ith P r e p a k t concrete, p ro v id in g n o t only a g re a te r b e a rin g a re a b u t also a b e a rin g on firm er g round a t th e low er elevation.

Fig. 5a.— To pre­

pare for restoration with Prepakt, o ld concrete is trimmed a w a y t o s o u n d m aterial.

Fig. 5b.— Forms are packed with coarse aggregate, and in ­ trusion mixture is pumped in.

Fig. 5c.— F in ish e d

s u r f a c e , b e f o r e

cleaning.

Fig. 6 .— Laboratory test o f placing Prepakt concrete under water. N ote sharp line of demarkation between rising intrusion mixture and water being displaced.

D u rin g floods it is n o t u n u su a l for m u d or gravel to be w ashed from u n d e r piers w hich re st on piles. If th e a m o u n t of m a te ria l rem oved is considerable, th e la te ra l su p p o rt to th e piles is lessened to such an e x te n t t h a t th e s tru c tu re w eaves n o tic e a b ly u n d e r load. One in sta n c e in w hich th is condition w as co rrected b y in tru sio n is illu s tra te d in F ig. 8. H oles w ere drilled dow n th ro u g h th e footings, m u d a n d san d were flushed out, a n d th e space w as filled w ith in tru sio n m ix tu re, w hich also sp re a d a- ro u n d th e p ier a n d sta b ilize d an a re a g re a te r th a n th e original. T h e holes w ere ex ten d ed fu rth e r dow nw ard a n d w ere in tru d e d to fo rm a solid w all to p re v e n t fu tu re scour. S till fu rth e r dow n, th e existing la y e r of coarse sa n d a n d gravel w as flushed o u t an d solidified b y in ­ tru sio n . T h e a p p ro x im a te final lim its of in tru sio n , as d e te rm in e d b y drilling, are in d ic a te d on th e draw ing. In stab ilizin g th e piers of o th e r bridges, in som e cases th e opening b e n e a th th e p ier has been so large t h a t i t w as filled w ith rip ra p or w ith p rep a ck ed ag g reg a te in o rd er to re ­ d u ce th e a m o u n t of in tru sio n m ix tu re required.

A b u tm e n ts a n d w ing w alls are re sto re d in a m a n n e r sim ilar to t h a t p rev io u sly described for piers. A ty p ic a l case is illu s tra te d in Fig. 9a

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RESTORING AND STRENGTHENING MASONRY STRUCTURES

a n d 9b. I n a d d itio n to th e w ork show n, th e e n tire in te rio r of th e m a ­ so n ry a n d jo in ts w as solidified b y in tru sio n . I n a n o th e r case a n e n tire a b u tm e n t w as b u ilt w ith P re p a k t co n crete w hich could be c a s t m o re econom ically w ith p la n t a lre a d y a t th e site th a n b y b rin g in g in a con­

v e n tio n a l p la n t an d ca stin g o rd in a ry con crete (Fig. 10).

A com m on ty p e of e arly co n stru c tio n of sm all sin g le-arch b rid g es con sisted of c u t-sto n e m aso n ry to th e sp rin g line a n d b ric k m a so n ry in th e arch. O v erc o atin g of th e d isin te g ra te d m a so n ry w ould lessen th e opening of th e w aterw ay . S everal b rid g es of th is ty p e h a v e been re ­ sto re d b y rem oving th e sto n e in a lte rn a te le n g th s a n d c a stin g P r e p a k t co n crete to th e original line of th e s tru c tu re (Fig. 11a a n d l i b ) . Solidifi­

catio n of th e P re p a k t u n d e r p ressu re assu red tig h t c o n ta c t a n d p re ­ v e n te d s e ttle m e n t of th e arch . In one case, th e arch es of a sto n e brid g e w ere deepened over th e ir e n tire a re a w ith a P re p a k t-c o n c re te a rc h w hich b ecause of th e pressure filling w as ab le to sh are th e lo ad w ith o u t s e ttle ­ m e n t of th e arch.

R e s to ra tio n of th e piers of a long railw ay b rid g e u n d e r h e a v y traffic a n d severe u n d e rw a te r conditions w as accom plished b y th e in tru sio n a n d P re p a k t m e th o d s in 1941-1943.* T h e piers, 70 y ears old, h a d been b u ilt b y sin k in g w a te rtig h t tim b e r caissons in p lace a n d th e n b u ild in g a concrete b ase a n d c u t-sto n e p ier on each b ase. A ro u n d som e of th e piers h a d been p laced o p e n -b o tto m caissons w hich w ere filled w ith rip ­ ra p . D e te rio ra tio n of th e o u te r caissons e v e n tu a lly allow ed m u c h of th e rip ra p to escape; in som e cases dam ag e to th e tim b e r of th e c e n tra l caisson h a d p e rm itte d erosion a n d d isin te g ra tio n of th e co n crete fo u n d a ­ tio n ; a n d th e c u t-sto n e p o rtio n of th e p ier w as in b a d c o n d itio n p a rtic ­ u la rly a t th e jo in ts. A t som e of th e piers, th e w a te r w as as deep as 50 feet, a n d th e c u rre n t w as as sw ift as 12 m iles p e r h o u r. I n sp ite of th e se a d v erse co nditions, th e e n tire re s to ra tio n w as acco m p lish ed a t a cost e stim a te d to be less th a n t h a t for th e c o n stru c tio n of one n ew pier.

In th e u p p e r p o rtio n of th e piers, w hich w ere o rig in ally faced w ith a sh la r m a so n ry a n d filled w ith ru b b le m a so n ry s e t in lim e m o rta r, th e v o lu m e of in tru sio n m a te ria l p u m p e d in w as u p to 12 p e r c e n t of th e overall volum e.

A n o th e r o u ts ta n d in g renew al, t h a t of th e 24 piers of a ra ilw a y b rid g e 85 y ears old, w as accom plished a t a co st e s tim a te d to be o n e -te n th of th e cost of re p lacem en t, f I n no case w as i t n e ce ssary to u n w a te r th e p iers ; only a row of sh e e t piling w as d riv en across th e nose of th e p ier in o rd er to slow th e c u rre n t a n d p e rm it p ro p e r in sp ectio n a n d w o rk b y divers.

F ig u re 12 is a w in te r view u n d e r th is bridge.

* ” S u b s tr u c tu r e R e p a irs U n d e r D iffic u lt U n d e r w a te r C o n d itio n s ,” R oads a n d B rid g e s (T o r o n to ) , N o v 1943, p p . 36-40, 65-69.

f ‘R e ju v e n a te s 8 5 -Y ear-O ld B rid g e P ie r s ,” C . P . D isn e y , R a ilw a y Age, J u n e 16, 1945, p p . 1049-1051.

Fig. 11a (left)—Disintegrated stone masonry in bench walls of this single-arch railw ay bridge was removed in alter­

nate 5-foot sections and re­

placed with Prepakt con­

crete.

Fig. 11b (right)— Second stage of replacement— Prepakt concrete sec­

tions permit full flow section and pro­

vide smoother surface than original construction.

T h e lining of several tu n n e ls has been solidified a n d stabilized b y th e in tru s io n process, w ith P re p a k t concrete used w henever re q u ired to replace displaced or dam ag ed sections. One of th e earlier jo b s is de­

scribed in W estern Construction N ew s, Feb. 1939, pp. 35-38 a n d in R a il­

way Age, M a rc h 4, 1939, pp. 373-376.

Fig. 12.— O ne of two long railw ay bridges for which the piers were restored by intrusion and prepacking. Severity of ice conditions causing disintegration is apparent. Scaffolding for work interrupted by winter conditions is still on nearest piers.

A reservoir, show n in Fig. 13a a n d 13b, h a d been b u ilt in sa n d sto n e ex cav a ted to a d e p th of 14 feet a n d on th e fill fo rm ed b y th e e x c a v a ted san d sto n e to a n a d d itio n a l d e p th of 14 feet. T h e sides w ere on a slope of 1 to 1. T h e e n tire a re a of th e c u t a n d fill h a d b een su rfaced w ith a b la n k e t of clay, on w hich h a d been c a st a c o n crete slab 4 to 6 in. th ic k . S e ttle m e n t of th e fill w as so serious t h a t it w as im possible to fill th e reservoir m ore th a n h alf full, a n d m u c h of th e clay b la n k e t w as e v e n ­ tu a lly w ashed aw ay leav in g large voids a n d cav ities. T h is co n d itio n was co rrected b y in tru sio n th ro u g h a n d u n d e r th e b la n k e t, a n d th e reservoir w as ren d ere d sta b le a n d w a te rtig h t.

A large con crete d a m b u ilt in th e d a y s of long g ra v ity ch u te s, w e t m ixes, a n d co n seq u en t seg reg atio n a n d la ita n c e fo rm a tio n , is show n in Fig. 14. V ertical c o n stru c tio n jo in ts w ere sp aced 25 ft. a p a r t, a n d lifts w ere a b o u t 5 fe e t deep. L eak ag e of w a te r th ro u g h b o th ty p e s of jo in t w as extensive. I n o rd er to sto p th e leak ag e th ro u g h th e v e rtic a l jo in ts, holes w ere d rilled a t in te rv a ls along each jo in t, e x te n d in g in to th e rock fo u n d atio n . In tru s io n w as co m p leted in th e e a rly sp rin g , w hen th e w id th of th e jo in ts w as a m a x im u m due to seaso n al c o n tra c tio n of th e con crete blocks. T h e h o riz o n ta l c o n stru c tio n jo in ts w ere also sealed

RESTORING AND STRENGTHENING MASONRY STRUCTURES

Fig. 1 3a.— Reservoir built half in excavation and half in embankment showed extensive leakage in spite of clay blanket.

Fig. 13b.— A fte r intrusion to seal foundation and re­

place eroded portions of blanket, joints were sealed and entire surface treated w i t h w a t e r p r o o f i n g compound.

Fig. 14.— V e rtica l and horizontal construction joints have since been sealed by intrusion. Down­

stream face w ill be restored later.

b y d rillin g a n d in tru d in g from th e to p , each laita n c e seam being th o r­

o u g h ly flushed o u t before in tru sio n .

One in te re stin g d ev elo p m en t has been th e solidification of rock-fill b re a k w a te rs an d sea w alls to p re v e n t scour an d b re ak -u p in h ea v y storm s.

F ig u re 15 show s a tro u b leso m e section of rock ap ro n w hich h as been sta b iliz e d b y filling th e spaces betw een th e large stones w ith crushed- rock ag g reg ate a n d th e n in tru d in g th e m ass to form a five-foot ap ro n an d to e w all ex ten d in g well below low tide. In a su b seq u e n t sto rm , m uch of th e u n tr e a te d ro ck section show n a t th e le ft of th e p h o to g ra p h was w ashed o u t, w hereas th e tr e a te d section is still in ta c t.

In sp ectio n of a large concrete-lined spillw ay tu n n e l disclosed several ero d ed cav ities in th e in v e rt. T h e la rg est of th e se b re a k s w as a b o u t

Fig. 15.— Section of sea w all subject to heavy tide and wave action has been stabilized by intruding to form a solid blanket 5 feet thick. Rock Fill at left has since been washed out by storm, leaving the intruded apron intact.

112 ft. long a n d 33 ft. wide, w ith a m ax im u m d e p th ol sco u r of 36 ft. A d escrip tio n of th e re p a ir w o rk b y th e P r e p a k t m e th o d is given in ‘'E r o ­ sion C auses In v e r t B re a k in B o u ld e r D a m S pillw ay T u n n e l,” b y K e n ­ n e th B. K eener, Engrg. News-Record, N ov. 18, 1943, pp. 762-766. Q u o t­

ing from th e d escrip tio n , “ . . . in v e stig a tio n s in d ic a te d t h a t su ch a m eth o d h a d definite a d v a n ta g e s in t h a t th e high b o n d in g s tre n g th of p re p ack ed concrete, its low c em en t c o n te n t a n d low te m p e r a tu re rise, sm all sh rin k ag e a n d th erefo re less in c lin a tio n to cracking, w ould m o re th a n co m p en sate for its slow ness in a tta in in g stre n g th . H ow ever, th e p rim a ry reaso n for a d o p tio n of t h a t process w as th e conclusion t h a t th e rep airs could be m a d e m ore econom ically th a n b y re g u la r co n crete p lacin g m e th o d s.”

A u n iq u e design fo r b rid g e piers in deep w a te r h a s b e e n d ev ised b y C. P . D isney.* I n th is design, steel H -piles se t in th e b e d ro c k are en ­ cased in a P re p a k t-c o n c re te pier. S h e et p iling is d riv e n to th e o u tlin e of th e finished pier, th e enclosure is w ash ed clear of all m a te ria l ex c e p t t h a t w hich is su ita b le for inclusion in th e s tru c tu re , th e re m a in in g sp ace is p ac k ed w ith ag g reg ate, a n d th e p ie r is in tru d e d to fo rm a m o n o lith ic whole. W hile th e o p e ra tio n is n o t t h a t of rec o n d itio n in g as are th o se p rev io u sly described, it illu s tra te s th e p o ssib ilities fo r a lte ra tio n s of, a n d a d d itio n s to , ex istin g stru c tu re s.

T h e w o rk of re s to ra tio n b y e ith e r m e th o d d iscussed h e re in is con­

d u c te d b y In tru s io n -P re p a k t, a n d new c o n stru c tio n u sin g th e P r e p a k t m e th o d b y th e P r e p a k t C o n cre te C o., b o th w ith offices in C hicago, C leveland, a n d T o ro n to .

*“ R ed e sig n of th e Q u eb ec B rid g e ,” b y C . P . D is n e y , R oads an d B ridges ( T o r o n to ) , F e b . 1943, p p . 17-22, 48.

a vailab le from A C I at 50 cents each— quantity quotations on request. Discussion L o f this paper (copies in trip lica te) should reach the Institute not la ter than M a y 1, 1 9 4 6 J

Title 42-15 — a part o f PROCEEDINGS, A M E R IC A N C O N C RETE INSTITUTE V o l. 42

of the

A M E R I C A N C O N C R E T E I N S T I T U T E

(copyrighted)

V o l. 17 N o. 4

February 1946

La b o ra to ry Studies of Concrete C o n tain in g A ir - En tra in in g A d m ix tu re s*

By CHARLES E. WUERPELf

Member American Concrete Institute

S Y N O P S I S

The effects of th e incorporation of each of nine different air-entraining adm ixtures in concrete were investigated by the m aking of a large num ­ ber of batches of concrete under carefully controlled laboratory condi­

tions. The results of tests on the plastic and hardened concrete speci­

mens from batches made in parallel w ith and w ithout each adm ixture are presented and discussed. An interpretation of the significance of the d a ta and their application to the successful use of air entrainm ent in concrete is given.

IN T R O D U C T IO N

T h e p ra c tic a l a d v a n ta g e s to be d eriv ed from th e e n tra in m e n t of well d is trib u te d m in u te spheroids of a ir in concrete m ix tu re s w ere b ro u g h t to th e a tte n tio n of th e w rite r in 1939 b y w ork p erfo rm ed b y th e P o r t­

la n d C em en t A ssociation on e x p e rim en tal p av em en ts. S everal field a n d la b o ra to ry in v estig a tio n s h a d been in s titu te d b y o th ers d u rin g th e p rev io u s d ecade w ith som e v ag u e id ea of th e b en efit to th e h a rd e n e d concrete in h e re n t in a ir e n tra in m e n t. S earch of th e lite ra tu re reveals a n u m b e r of references to th e use of fa ts, oils, a n d greases in cem en t earlie r in th is c e n tu ry as is in d ic a te d in th e b ib lio g rap h y a p p en d ed to th is p ap er. R eference w as fo u n d (2) J to th e follow ing specification for stu cco as w ritte n b y M a rcu s V itru v iu s Pollio, th e fam ous R o m a n a rch i­

te c t, in th e first c e n tu ry A .D .; “ A m ix tu re of w ell-h y d ra ted lime, m arb le d u s t a n d w h ite sa n d m ixed w ith w ater, to which m ixture is added either hogs’ lard, curdled m ilk or blood.” T h e reference to th e “ b lo o d ” is sinister,

♦ R e ce iv e d b y th e I n s tit u te D ec. 12, 1945. . . .

( t) E n g in e e r in C h a rg e , C e n tr a l C o n c re te L a b o ra to ry , N o r th A tla n tic D iv isio n , C o rp s of Engineers*

U . S. A rm y , M o u n t V ern o n , N ew Y o rk . ,

( t ) T h e n u m b e rs in p a re n th e s e refer to th e b ib lio g ra p h y a p p e n d e d h e re to .

(305)

b u t th e reference to “ ho g s’ la r d ’’ is illu m in a tin g in t h a t i t in d ic a te s t h a t th e p ra c tic a l use of th e b enefits of e n tra in e d air is n o t a tw e n tie th - c e n tu ry discovery. T h is earlier w ork n o tw ith sta n d in g , th e p e c u lia r m e rit of p u rp o sefu l e n tra in m e n t of air in con crete h as becom e g en e rally kno w n a n d m ad e use of only in th e p a s t five y ears.

T h e d a ta com piled b y th is la b o ra to ry from te s ts on field specim ens a n d o b serv atio n s m ad e in conn ectio n w ith th e c o n stru c tio n of n u m e ro u s p ro jects, using p lain a n d a ir-e n tra in in g concrete, b y th e C o rp s of E n ­ gineers since A pril 1941 h av e been p u b lish ed (79). T h e re su lts of stu d ie s b y th is la b o ra to ry of v ario u s form s of V insol resin in te rg ro u n d w ith cem en t h a v e also been p u b lish e d (30, 31, 45, 65, 71, 77, 81 a n d 82).

I t is th e p u rp o se of th is p a p e r to p re se n t th e re su lts of th e m o st re c e n t la b o ra to ry stu d ies of a ir-e n tra in in g a d m ix tu re s w hich w ere a u th o riz e d :

(a) T o d eterm in e if th e benefits w ere solely a ttr ib u ta b le to th e a g e n t used or to th e air e n tra in e d or to a co m b in atio n of b o th ;

(b) T o d eterm in e th e m o st effective use of a ir e n tra in m e n t a n d th e o p tim u m lim its of such use, a n d

(c) T o develop a specification fo r a ir-e n tra in in g a d m ix tu re s a n d re la te d m e th o d s of te st.

T h e w ork w as d iv id ed in to a n in itia l a n d seco n d ary p h ase , th e re ­ su lts of w hich are h e re in a fte r re p o rte d in d e tail, a n d a te r tia r y p h ase, in v o lv in g co n crete co n ta in in g larg e (6-in.) ag g reg ate, w h ich h a s n o t progressed sufficiently to w a rra n t m ore th a n b rief m e n tio n a t th e close of th is paper.

IN IT IA L P H AS E Adm ixtures

I t w as decided t h a t th e in v e stig a tio n sh o u ld n o t be lim ite d to a d m ix ­ tu re s w hich h a d been in te rg ro u n d w ith th e cem en t, b u t sh o u ld in clu d e th o se w hich are a d d e d a t th e m ixer. F o r th is p u rp o se , th e m a te ria ls listed in T a b le 1 w ere in c lu d ed in th e w ork.

T A B LE 1— N A T U R E O F A D M IX T U R E S

Q—A com bination of spent transform er oil an d triethanolam ine.

R —A neutralized form of gasoline insoluble resin of th e pine tree.

S—R plus calcium chloride (non-proprietary).

T —Saponified beef tallow (non proprietary).

U—A com bination of an alkali salt of a fa tty alcohol sulfate an d calcium lignin sulfonate.

V—A com bination of R , calcium chloride and alum inum powder.

X —Paraffin-oil (non proprietary).

Y— A solution of calcium chloride in w ater containing a small am o u n t of an un­

identified organic m aterial—n o t an air-entraining agent.

Z—A com bination of fly ash, calcium chloride and calcium lignosulfonate.

No t e: I n all cases the symbol P represents concrete without admixture.