New Zealand pumice as a lightweight concrete aggregate

THJ~8IS PR.:i':i:PAHKD ll'OH '.rHg

HAOHJELOH OF' l!:NGINEERING (HONOURS)

during 1949 on

I would like to express my gratitude for the advice

and Buggestlon,s gi von most willingly at all times by' lV!r D~ Br•1we Smith, Senior Lecturer in Structural Engineering, and by lV!r

M.A. Craven, Engineer to the :New Zealand Po1~t1and Cement .Association o I would also thank all those membe:r. s of the

staff of the National School of Mngineering, Canterbury College, who have assisted in many ways during the year,

especially appreciating the co-operation of those who have had

to p1.1t up with the pum:tce dust accompanying the work.

I thank the following people for help at various stages of the

work:-Messrs S.R.Siemon, Senior Lecturer in Applied Chemistry, M.Gage, Senior ~ecturer in Geology,

H.

c.

Lough, A ssj, stant Eng:t neei' 5 M. 0. W. Destgn Office, F.J.T.Grigg, Domj.nton Analyst,

L.H.James, Acting Dominion .Analyst,

J.T.Gilkinson, Project Nngineer, Mangakino, ~r.Healy, Super:lrrtending GeologlEJt, R.otorua, G.N.BJuck, Senior ~ngineer, M.O.W., Rotorua.

D.M.Wlillson,

4 ..

6.

Int1:>oducttm1

The 11.:xtent and Nature of' the l;)umi ce Deposits in New Zealand

The Design of' the Research Equipment

'I'est:ing and l\Ux:i ng Procedure

.. Ph;y-sica1 ~Pests carr•ied out on Pumtcf;; The Mixing Programme with Gradings

adopted for• Pumice Concrete

The Results of the Pumice Concrete Mixes carried out

Conclusion

The Advantages and Disadvantag-ce Concrete in Structural

Bibl:lography

12

23 31

36

44

G6

With the present day advance of building science, concrete engineers are beginning to look into the possib-ilities of making lightweight concrete particularly from

liglltwei.ght aggregate. There are many reasons for this, the 1nost obv:i.ou:3 being of course the reduced dead weight fox•

at:r.•uctt.u~al worit, whj_cb means lower dead Joad moments in beams and columns. '.L'l1e reduction in dead loads is a1so accompanted by lower earthquake forces on a building, and lower foundation loads which means lighter and cheaper foundations. In

connection with earthquake resistance, a lightweight structural concrete with a low modulus of elasticity is a more flexible and f:>hocl~: 1•esistant bu:Llding matei'ial than normal gravel concrete. It is also desirable to have a material out of which light partition walls can be c6nstruc~ed.

Normally, lightweight aggregates owe their lower unit weigl1t to enclosed air. This means that with these

aggr•egat es thei'e also comes several other i nhePen t. ad vantages in better thermal and sound insulation. Also several light-weight aggr'EJgat.cfl, pumice amongst them, prov:LcJ.e a concl'ete v1hich ean be nailed and sawn without damage. /Pumice lla.s these advantages and one otbex• impox•tant one, that of being almost totally fireproof. 'lthis is due to two fo.ctors, one being the inert nature of the material, and the other and most important, the thermal insulation properties.

But before proceedj_ng further it becomes ne.cessax•y to define what purnj.ee ls. One defJnition

from rock fragments thrown into the air from active volcanoes.

1

l1_{he" sudden eXlJansion of gasses within the rock structure and}

rapid cooling tr•apped tiny bubbles of gas that cau.sed it to r•emain as a spongeli.ke but tough and durable ma ter•ial11_•

However, a better idea of the formation of this material may be gained from an extr•act talcen from "Geomor-phology" by Pr•oi'essor G.A. Cotton.

11_{The more viscid -- that is generall;y non-basalfltic}

lavas become much inflated owing to liberation of gas

throughout the body of the material in the conduit through which lava is rising to the surface. Expansion of the gas owing to a r•elief of' pressure as the surface is appr•oached pl~ovides the motive power• fol' the explosive ejection of rnater1a1 .. It also converts some lavas into a foam which, when solidj_fi.ed, makes pumice. Purnice may be ejected j_n l::n•ge l.uinps; or the pr•o t:ess of ga a-emission may r•educe the mater•ial. to small pellets (lapllli), or pr•act1cally to a.

powder consisting of tubular shreds of glass and isolated minute crystals of minerals in course of separation from the

cooli. ng lava".

At this stage, perhaps it would be advisable to classify briefly the uses of lightweight concrete in engineering construction, either in a precast or cast-in-situ

form:-A .§.!;x•uct.ur·~~ as fox• ordinary full-weight concr•eteo B Non-8tructux•a1 used as a 1nedtum for heat or' sound

t nsulat i.on, f'or fi reproof'i ng, or for• non-structur'al f:llli. ng.

3 ..

(b) For external walls between other steel or concrete

membel-<~Se

(c) For light-vJeight roofing on a stx·uctural frame in the

form of slabs or tiles.

(d) For interior :partition walls ..

(e) Fol~ _{:providing nailable surfaces where I'equil""'ed,.}

'f')

\- Fo1~ covex•ing pipes and conduits vvithin \lilalls or

floors, or as a thicknessing or filling media, where

deadweight would make a dense concrete fillrng

uneconomical,

(g) For protecting steel beams against fire.

(h) For the construction of fireplaces, chimneys,

coppers, etc ..

PUMICE CONC!U:TE

Taken in conjunction with the structural :properties

of pt.unice concrete, the two most im:pol"tant factors in its

uses are unit weight and insulation :properties; the former

to be considered later, so the latter will be considered now*

?lease note that all figures quoted in this section of the

report are taken from .American :practice,.

(a) Thermal Insul~tin~ Properties

Here I quote figures taken from the A.C.I.Journal May,

1948, nPrefabricated Pumice Concrete Housestt by

The fi~ares are expressed in terms of conductivity in B.T.U's,

per hour, per square foot, :per inch thickness, for 1oF.

difference between the two wall surfaces.

Material

Sound and Gravel Concrete Portland Cement Plaster Cinder Concrete

Building Brick

Conducgvity

12.0

8 .. 0

Gypsum Plaster Asbestos Boar•d Purn:lce Concrete Fi br•e 13oard

L86

0.5

Also quoted ar•e the figu:r:•es for ,gu x 811 _{by 16}11 _{3 core} building blocks in various materials, the values being taken for the whole 811 _{width in this case.}

Sand and Gravel Concrete Cinder Concrete

Purrd_ce Concrete

0 .. 95

0.60

'rhus it can be seen that pumice concr•ete compares favourably with other building materials.

(b) Fire Resistance

'r1w :.f.'usio11 point of pumice is 2₁4500IP. ap:pr'loximately and isjfar as tests have shown no undesirable effects

(spalling etc.) are noticeable until the pumice concrete

reaches a temper•ature of' 1,4000F. As the maximum temperature in a b1:dlding fire rarely exceeds 1, 2000F., it can be seen that a burnt-out pumice concr•ete building needs only r•e-lining for re-usee 'l'his compares favourably with full-weight

concrete which norlmally is serj.ously dmnaged by intense heat. In American 11 ter'ature on pumice concretejl practically every article describes holding an oxy-acetylene torch (1,600°F.) against the 2 inch thick wall of a standard building block • . Normally tt is 12 minutes ox• so befor"e the intel"ior face of

the wall becomes warm to the touch.

In an article "Pumice .A.gg:r•egate in :New Mexico, its uses and Potentialitles11 _{by D.Ivl.Clj.ppinger and W.E.Gay}

house is described. It was carried out in the city or Los Angeles, U .. S~A.

"This test was supervised by the city engineering and inspection departments, and performed by the city fire depart-ment .. Tri'w 55 gallon drums of gasoline were po.ured out on a layer of sand which 'J'Jas spread on the pumice concrete floor. The gasoline was then igniteda When it became safe to do so, a lH::e amount of: gasoline v-uas again distributed over· the floor to 1-.epeat the operation .. Vfuen the heat was estimated to be at the highest point, two firemen played hoses on the interior walls with .water pressure comparable to normal fire-fighting pressures. Inspection of this I1.ouse on the following clay

showed that the pQ~ice walls had not been damaged to reduce their stJ:•uctural safety and permanency'!~

(c) Sound Absorption

Briefly the sound absorption :pro:pel"ty of pu .. ruice concrete are set out below in comparison VIIi th some comr:1on building

materials:-Material Hair Felt

Pumice Concrete Wood

Gravel Concrete

Coefficient of Sound Absorption

.. 35

.175

.,06

.. 01

In connection with accoustic panels, I quote a short note from the articles by Clippinger and Gay, as follows:~

"By tests recently completed on the trowelled face of a pQmice concrete specimen, the average coefficient of sound

absorption was found to be 66 .. 1 percent with sound frequency ranging from 116 to 2,400 cycles per second. The sound

absol"ption efficiency is 83.9 :percent for normal office noises ..

6 ..

~umice aggregate graded from 40 percent minus No.4 to rb.8,

35 percent minus No .. 8 to N o,.16 and 25 percent minus No.16 to

No.28, will provide a sound absorption coefficient approaching

100 percent.

Exrunules of the Use of PQmice Concrete in Building Construction.

The first use of this material was probably by the

Romans. In later times there are records of its use in

Germany, Britain and Japan but very little literature is

available .. With the setting u:p of a large pumice mining

concern, supplying graded aggregate, in the U.S.A. in recent

years this material has come into extensive use .. With this

increasing use has come a steady stream of literature,

particularly in the last two years. Many very large

l:mild-·ings have been consti"'.Jcted particularly by telephone

companies, and it hss been used. extensively for light-tlileight

roofing as in a large new General r~'Iotors plant put up in

recent years ..

Possibly the best description of its use is contained

in an article in nEngineering News Recordn, March, 1939, in

which the construction of a building in Los Angeles is

des-cribed. This has a structural steel frame and Pw~ice

concrete 11 _{shear walls}11 _{v~hich are designed to take earthquake}

forces. The building covers two blocks and is 9 stories

high. The saving in total foundation load was 15,600 tons

against the final dead load weight of 32,000 tons and the

saving in structural steel was estimated at 1,000 tons.

Thus it can be seen that the use of purnice concrete

in New Zealand can well be investigated in view of its

properties, and the enormous quantities available in this

18\V ZE.liLAND PUMICE AS A LIGliWVEIGHT

CONCRETE AGGREGATE

SECTION I

The extent and nature of the uuiilice deuosi t s

in New Zealand.

This section has been included to give the reader

some idea or what pumice deposits there are, their extent

and natures. It also briefly covers the geology or this

material. It must be realized that p~mice found in different

1ocalities and even in oue deposit may vary in nature ..

These variations can be classified as

follows:-(1) Apparent Specific Gravity

(2) Natural Grading

(3) Chemical Composition

(4) Degree of Weathering.

These variations can be attributed to various

geological factors concerned in the formation, trans:port

and weathering of the pumice.

I am indebted to the following articles as a source

of geologica_l

data:-(a) uclassif'icatioD or Soils of the Rotorua County",

(H.Z.Journal of Science and Technology, Volume II, :pages

219-228)

(b) nGeology of the Rotorua-Tau:po Subdivision", (N.Z~

Geological Survey Bulletin, No.3?.)

Both these articles are written by L.I.Grange. A considerable

fu~ount has been written on the pmnice formation in New

Zealand but most of this is well-smmuarized in reference (b).

TASMAN SEA

Pt-.ENT Y

NORTH

ISlAND -

NEW

ZEALAND

VOI.CANIC

L.£G-ENO SJJGwel"

Ro 1-o,.ua Rh yoli 1-e

Taraw-era

[6'00 sq. ,....;les

;:?'

"cl~ep]

.4fgjrt:JQ

Taupo Pun?IC e

c.e

1)0 Stf.,..,. i les ?"b ''Jeep]

-~on!!~-~

;",.-.o

-A

-;;

d<:~,t:-:-s-;,:;.14~e~~tj}

IV.!J(u•ohoe Andesile

'ffi

IV9a~cu7o P;f ~rk.s ~ua,.,•y

SIJ,ply f"cr Concrefe .41/:t-es : 2 L. O"J e t;>uar/'y on !?oDds ide

13

T<>upD

Pu~,<o ~.od ~Puany

.,r:j:\

f?oad a~U'I'"OW'f"ir ncrfhPrn

~~ Oeser! ;qoc-d

See Tt: 1rf f"or defa,/s

o/ obovc

.She &Ning

ASH

SHOIN'£R8

OF Mlt..£S

I

:::±d ,

8 I~

INSET

ROTORUA

-TAUPO

8 ..

is taken from reference (a) above. The area of the North Island covered by the Taupo shower alone, to a depth greater than six inches, is 8,800 square miles or 19.9 percent of the total area. Compared li'li th this it ~;;ould seem that the

Tarawera shower of 1886, covering 600 square miles; was only a very small affair indeed.

As far as the geology of the p~mice deposits is concerned, much of the story is unknown, particularly the early part. The important recent showers are clasSfied

below:-The Pumice Shovuers

(10

The oldest is the Rotorua shower which had its origin in or near Lake Tikita?U (Blue Lake). The material is rhyolitic in nature. The ejecta was blown towards

Mamakv.., as the deposits are fine in this direction. To a height of 25 feet above the present lake level, the material

was laid down in water.

(2) The next is the hlamaku shower which is :probably from a vent 11ext to or the same vent as the Rotorua shower.

Possibly this occurred in tfrvo distinct showers.

(3) The Rotol\:awau shower was next, being this time a basa~lt shower from a series of craters now forming the lakes Rotokawau, Roto Ngata and Roto Atua.

( 4) The Tau-:Jo shovver erupted from the north-eastern end of Lake Taupo. The product of this shower was rhyolitic pumice and the extent of the shower can be realized, not

only from the 8,000 square miles of country covered, but also from the fact that. this sho1111er is at least 800 feet deep neai• Taupo •

9.

(6) The final eruption in the series so far, was the rrarawera sh~ in 18E:\6 f1•om which basa)hlt ash and

rhyolite matel'ial were ejected ·from a series of' craters adjacent to, and on Mount Tarawera.

All the pumice showers (1), (2), (4) and (5) are characterized by being of acidic lava; namely, rhyolite.

'l'he characterist:lcs of' such EJ lava ar·e that it is tlery vtscous

j.n the molten condition compared with the fr•ee-flowing mor•e basic types of lava. Thus bar:-dc volcanoes such as Ngauruhoe and •rongari no are not pumice-producers. The explana tton of this phenomena is that, although all lavas contain entrapped gases, these can escape more easily from the li5uid lavas

whereas the more viscous lavas solidify before the gases can

'l'he }Jumice showex•s vax•y in colour, the .most common colour being white, but there are also red, yellow and brown varieties. General,ly, the Taupo shower is creamy-white, the Kaharoa showe:r.• white and the Rotorua shower :yeLlowish-white.

'rhe p11m:i.ce for the research wor1c which was cax•ried out wa.8 taken f'I•om the Ngapuna pit, Ministry of Works quarx•y,

An analysis of this material was made by Mr L.H.James, Acting Dominion Analyst of the Dominion Laboratory as

follows:-S:lllca 8102 :per cent 70.06

Alumuna _Al20rz II II _{14 .• 60}

.J 0

Ir•on Oxide Fe203 II //- II 2a25

Magnesia lVi _g 0 If II _{0 .. 57}

Lime CaO II II

1.91 Soda NaoO (.>

II II _{3 .. 68}

Potash K,)o

(.J

11 II _2(>.42

'

Ti tanj.a T:l00 "'

tl II _Oa30

Gul.phur• trj.oxide

so

If If _'l1_ra.ce

· General viEw of t~o

floor of the quarry

Close-uno~ thE face ab~ve.

ml;_e lO\IEr Dhoto~rau~ shows t'1.C pumice slze in com~crison to a

nencil. .

10 ..

Chlorine C1 per cent 0 .. 16

Combined water etc.

I T • . • T )

\ ..!..gru tlon .LiOSs

Moisture (1050C) 0 .. 17

Total 99 .. 93

It should be noted that although the percentage of' silica is high, the great bulk of' this is present not as f'ree silica or quartz, but as a constituent or volcanic glass.

The material has been classed as coming rrom the Roto1~a

and Marnaku showers but the chemical analysis as f'ar as could be ascertained seems to ind:tcate the ~,Isr.aa~ru shovver ..

During the course of the year, a short trip was made through the pumice-areas in order to inspect the deposits, and photog1'"'a::9hs taken dux•ing this trip accompany this section

of tl'1e tl1.esi s. The abundance of' clean usable pumice available f'or concl"'ete lvorl-c and other uses is sufficient to yrovide all f'ut1n'e l'"'eguirements, and, wl12.t is more, it can be f'ound close to transport facilities, In most cases, the amount or over-burden is small. Tl'1e y-uinice is easily shi:Eted b·~T :_Jovver tools

and could be bladed from the quarry faces with ease.

As regards the variations in properties mentioned at the corr@encement of' this section., the folloiNing observations were Dade.

(1) Aunarent Snecific Gravity. This varies in two ways.

Firstly, it varies with the size of materialz Secondly,

smne pLL"Tlices contain more entrap:c)ed voids than others, but the variation does not ap:::_)e8.l" to i::;e vel"Y great. (2) Natural Grading. It must be realized t~at dlliTiice

naturally occurs not as solid deposits, but as a mass of variously graded material@ PLunice can occur in sizes

PUMICE QUARRIES OF THE \1/AITAHUNI-ROTGRUA ROA_D

Pumice quarry one and one half miles south of the

~auranga-Tauuo stream . Note size of car at foot of quarry .

First quarry,a pu1ice borrowpit six miles south of Lake Taupo .

11.

two inches downwards. Preliminary indications show that the natural gradings of pumice are very similar; usually deficient in fines below No.16 sieve size.

( 3) Chemical CoillJl~.::> l2!. Only small vm~iat ions occur• in the chem:i.csl comr)osi "c:i.on and these EU'e usually neglj_gible.

(4) l}egr~.§. o£~. Ac~ all the pu.mice i3bower:::~

described are of recent origin geologically, weathering is not a very tmpo:e tant facto:r.

During the trip, a visit was mad~ to the Ngapuna Pit quarPy in ox•der to take natural moJsture content samples whiol1 were Elnalyr:;ocl fH3 follows, percentage moj_ sture by

weight:·-(a) Top of quarry face 13.9 per cent (b) Bottom of quarry fsce 50.9 II II

64.8

32$4- II

Concluding in the words of Grange concerning pumice deposits near

Rotorua:-"If pumice can be successfully empJoy·ecl aG c:m aggx•egate for concrete, a plentiful m~ply can be obtained in the

Rotorua district. A ? foot layer oJ' pund ce f1:agment s 111 _{- 2}11 diameter and up to 611 _{fo:rmtng tbe coEtrse portion o:e the}

Hotorua shower oecux•s at the :foot o:f the hills at the back of Whakarewarowa. The quarries already opened in the flats ar•ound Hoto1,ua show that puJnice can be :pr<)cux•ed 1'rom this sou1•ceo '1'h1ck beds of' pum:i.ce outcrop along the sho11e or

r~a1ces Hotoi ti., Hotoehu and Hotoi'"LlB, bu.t those are cU stant f'r•om the railways. The pmn:Lce at all localities is clean, and

Having covered briefly some of the possibilities of

j;n:unice in the J~OPegoing sections of' the thesiB, it can be seen that there is some justification for reBearch work into

the properties of this material as a concrete aggregate, from a practt ca1 as tNell as a them~et t cal stancll)oi nt@ It now rernai ns to desm:'i be what research WOl'k was c1one and how it

wa~3 carried out. Tl.le stFuctural px•opePties o:C pumice concrete which were investigated

are:-( a) Compression t er:lt s -- most important. (b) Bond t e r3 t s.

(c) Modulu.s of :illlastici t~r (secant).

These tests were carried out on specimens cured for

periods of 7 days, 20 days and 3 months (84 ·days) respective-ly. Durtng the placing, seve1•al tests were carl'ied out on

the wet concrete as

follows:-(1) Unit Weight determination.

( 2 ) Sl u111p t est •

(3) Workability teste

(4) lt'1ow test.

In all, three types of pwnice concrete mixes were

planned,

namely:-(a) Plain pumice concrete.

(b) Pumice com•se aggregate, vvi th gre;ywaclze oand.

(c) Air entrained pumtce concrete.

Now, having decided on the controlled variables, a

apparatus would. need to be assembled in order to carry it out .. Now there are two important details to be noted.

Firstly, a series of' tests covering the large nu.-rnber of', variables above can only be regarded as preliminary to give a general pictul"e of the :field and to guide future research work into more de:finite lines.. Secondly, with the controlled variables :fixed, (there are several others not mentioned until the next ~ection) the methods and equipnent have to be

designed with the idea of rendering all other factors cf' no effect. This mixing, curing and testing procedure had to be standardized as much as :possible. The testing program

is detailed in the next section.

The list of essential equipment compiled for the research work

follows:-( 1) Constant-temperature room.

( 2) II _{100 :per cent l).u .. midi ty curing}

cabinetG

(3) Concrete mixer~ cubic foot .. capacity. id

(4) Sealed containers for cement storage .. (5) Moulds.

(6) A sllimp cone.

( '7) Worl"i:ability apparatus and "flov~ table11 • (8) Accu .. rate scales as specified by A.

s,

T.Ivl. to) m 2 ~.. .a ' ' => .. ..!...

\~ lWO ~ cuolc LOO~ ~rays Ior we~ concreGe.

(10) Unit weight container.

(11) Crushing equipment and screening eguipment for grading the aggregate.

(12) Aggregate testing cylinder.

(13) The use of suitable testing machines. (14) A drying plant for drying aggregate.

(16) A stop watche

(1'7) Sundry equipment i::~cluding therr:llometel~s (plain, wet and dry bulb, 111aXirlllliO and minimum), trowels~ an

A .. S. T .. 1I. tamping rod and containers f'or aggregate and water storagee

I vill now describe in detail those pieces of' equipment in whose design I was concerned or which.have important details to be specially noted ..

(1) Constant-temuerature room~

O~;ving to shortage of' space, this was made a.s Sl1lall as

possible .. As is shown 6n the accompanying drawing, it was constructed against existing rvalls of' thick brick requiring no further heat insulation .. However, the f'ront and roof' of the room were lined with a 3-inch thickness of sawdust between plain timbered walls ..

ma11ner ..

The door was also insulated in a like

A .. S .. T.M. C192-4'7T specif'ies that curing shall be done at 650F - '750F so the temperature of '700F was selected for both the. room and the curing cabinete The temperature was controlled by a Satchwell t;srpe "Q,Pn air thermostat vv:i.. th an operating range of' 2: 1°F. At a later date, it was decided that it was an advantage to keep the mixing room at 650F and the curing cabinet at '70°F so that when the blocks were f'irst placed in the curing cabinet, there would be an initial

condensation of moisture on the surface which would ensure correct initial curing. The normal temperature of' the surrounding buildings is considerably less than sooF, so by coupling the thermostat to a small heater and circulating fan, no trouble was experienced in keeping -~he room up to

teml::Jerature .. The heater is of 1 K .. W. capaci t;;r .. The

..

...

·

_.

.

..

@

-? ;

·-

_I ..; .. ·: .-. •I .... 1 -=~ .t ·' .•

..

.

, =~~

S£CTION A-A

%d

INDEX

cc

ss

FS

88

p

M

B

Bosin "/died 4-Vdi, ee-l!'nf- lrap /or wusluh ;n!A"t>r.

F

Flow fo.blc , rell?lfl$'1!'ohl~e ~ncl r~ploc.sJJ/e.

SECTION

B-B

0

0 Ce,.,en f

Tro;;

HEATING

APPARATUS

OETAIL

{Celo~N n?}yerin

Sec.lion B-8)

~

/

In let

i~b Screw c<Jnnecf;cn fo bo.stn

~=

O.uflef

L - - - t d ~

C£M£NT

TRAP

( /3elcW" 1.3 os t'n)

PUNIC£

CONCRETE RESEARCH

SCALE:. DRAWN

CON.S7ANT

TEMPERATURE

_{1 !=#td} MAIN _{t .. /utch} 6 /t0/-1~

GJ

~ I

®

~

@

®

'/:/·

Af

-' I ~

I

{~9t"

IJESCRIPTitJN

Wmdow of o'ovhlc:: g!c::J~S SjJoced /11

Ctparr or tew/n h er/7?orne ers In co i nef. Door o f dou.ble.. osbC?sfos Sf'oced If:. 11

oporf /ill~cl wt th sowdu.sr and sponge

1---+---r-:-:-'-uhbt!'r /,.ned for on ot'rt"/9h t- seal.

-Folv~ t'c con fro/ .su,Ppl_y f"o IVai~,. ~"k ~~-~-r-=cgt..dc.l-ed unfil orer~low 's .Just clr'p~ln.!J

B ;,/t on door so cobmef Con be /oclred

when ne<t:-.sSo,., •

low - b reu--;i(-:5--w-",~.1-ch---,----co-n--:fr_o_ll-/n-'.!1-~-o-w-e-r--4

5u or'/. l'o healers.

®

lO/?crele walt:"r h<!c-hny Tanir/ 6 '1deef', 4-"

wa//.s, COj'Oci:z 3.J2ya//ons. feyed/-o _/'/oor

.by ch;);:"nf ~~~, wq.sh1n_f "_y~"oul1ny lfli/1;

n eo I ceh? e;-, f Co~aclly o/ ./-,;;.nk fo

het1/ers ,./'usf c:.o ~ered 17·4 gallonS

CROSS-SECTION

.B/l

"F CONCRETE TANK

.,•

., :J .

· .. J

..

~

~~~·

SECTION ~

O£TAIL FITTING OF H£ATER

IN

CONCRETE

TANK

PliAIIC£ · CON~N£T£ RESEARCH ICAL£ PRAWN

CONSTANT TEMPERATURE

HUMIDITY CABINET

IIIlA lN . I

I

1/i,otT./ilfcl, 20

1'"

~!}

DETAIL LJ. dt.)f:

15 ..

lined with asbestos in case the fan should rail to come on.

A check or temyerature conditions throughout the room showed

remarkably constant results -- never much more than + 1GF variation ..

As can be seen in the drawing, one side or the room is occupied by the mixing bench. Beneath this is a cupboard which housed a large galvanized tank containing the bond specimens, stored under water. There is also a small shelf for trowels etc., and a cement trap. The cement trap gave considerable trouble due to the fact that it was very in-accessible. The whole tank, however, was made removable for cleaning.. This \lilas all that could be arranged under the

circumstances, but a large outdoor settling tanl~ would have been much better. Also, considerable ~nounts or floating pQmice could not be stopped by the trap.

The layout or the mixing bench made for easy cleaning of' the m_ixer b;si hose from the ta_y, directly into the basino The bench was made only 2 feet high for easy handling of' the mixer ..

Considerable shelf'· storage space was allotved f'or. The flo~ table was removable, and above this is shown a folding shelf', to which result sheets could be pinned f'or easy enter-ing up ..

(2) Constant-temperature 100 uer cent Emnidity Cabinet .. A :fully dimensioned drawing of' this is included f'rom the outside by the teermometers behind the double-glass window.

(3) The d~sign of' the Concrete Mixer.

Considerable difficulty was had in trying to lacate any data on this subject. Initially, a mixer speed of' 23 r.p.m. and a rated 'Capacity of'

i

cubic foot were decided upon from current laboratory practice.

16.

This gives total drum capacity 2 .. 5-3 times rated capacity, and the latter figure was chosen. The actual designed capacity of the whole drurn was 1 .. 485 cubic feet .. The dru..m bottom was specified of 12 gauge steel sheet and was pressed out to a saucer-shape. The drurn top and blades are 16 and 14 gauges respectively. The whole dr~m is welded together and a

:k

11 _{diameter rod is bent into a ring and ~!lelded to}

sti~fen the drum top. The socket to take the driving shaft at the base of the drum was welded on, and then the whole drum centred on a lathe and the hole f'or the shaft bored out ..

The drive f'or the drLLm was selected for the following

reasons:-(a) To be silent, as mixing was done in a small room. (b) To be self-lubricating with no chance of grit getting

in the lubricant.

( c)rr:To do away with the expense of having the large be111el gear made, normally associated with external drive. (d) The worm drive chosen was free from the defect

assoc-iated with external drum drive, where grit caught

between the bevel gears means that the bearings or the

-drum have to be capable of taking considerable overload • .As can be seen from the accorr~panying drawing, the

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IND£X

Gene,..al

/Je rail

j ;;?,(Jcc.;r {Jit::!/c:le haru.t'/e,S~r/p.

2. Js,."¢ Af. S. f-u6c hc,.,c//~::.

2 I !"¥ d"'""" t:{,.;.,;ny .s-ho /'r.

22 s~c.fi~n 12 ~ dru,., h47ffo,..,.,_

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re.f-o/ni,g-31--J",..j" lr~f:F f".,,. _o,._ wl.ee/.

15

I(; --J-"' plof-e dr/Ye P~S't:P>~~~over.

17 )"¢ P'Pe ,..,.,;, OeoNn

hocui~s-18 c-~arcox oil ;:;!fer ;. ole.

~-,-~-+-6~~-"U-;.~-~---;; f:r~,.., -F /;;,;~ i~ -:

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IVO. 8801'1' sealed' becu .. ;ng. _

~7 5_k:F. R-M-S4 pla/n bea,.ing.

D£TA

Pf/MIC£ CONCRETE RESEARCH

LABORAT,OfiY

CONCR£T£

MIXER

SCAlE

MAIN

5 mches fo linch

DETAIL

lfolf full siz~

DRAWN

0-..

For al position.

1-w showing - motor ,

worm drive and d~t ils

of constructio 1 .

of m1x1n0 blades .

Below .- Lixer tilted to

17.

qnd worm-wheel are enclosed in a sealed oil-chamber. The drum is carried on two sealed ball-bearing races, lubi•icated for· life.

The drum is held at the desired mixing angle by a

cotter pin to give a 25° or a 300 mixing angle, the latter to

cope wlth an overload in the dPUJn. As detign was limited

by size r•eguirements, neither the motor no:r the bearings work at anywhe:r.•e near their full capacity. In practice, the mixer has a thorough mixing action, and has exceeded all

expectations. One small defect is that the motor• is not a totally-enclosed t;)Tpe, as these were unobtainable at the time, so the motor has since had to have a cover fitted to exclude water. When the drum is fulJ., very little effort 1 s required to tilt the drmn, and even when it is empty, the effort required is small.

Photographs of tho mixer ere lncluded with tho thesis. (4) Cement Storage.

;\'G the commencement of the mixing program, the total estimated cement requirements were made out. The cement was then all emptied onto a mixj.ng board and thoroughly rntxed. The cement containers were 10 lb. honey tins, and these were

sealed with wax to ensure uniformity dur·ing the whole 3 month mixing period; bej_ng stored in the constant-temperature room.

( 5) Moulds.

(a) Compression

--

double 5" cube moulds. (b) Modulus o:t':' E. ditto •

(c) Bond specimens .;2.11 .bars and

12

11 _{bars embedded in}

4 8

Com res&i~n ~oulds .

Closed .

ond .

I 'Jo C'T'en .

FLC I T \RLE .

---Tot:' photo13ranh c:ohows

com~o~er.t p~rts .

Botton nhoto ... rar:''rl s'1.ov1s

18 ..

(7) Workability apparatus and Flow Table.

These two pieces of equipment were designed by another Honours student., Mr Goats, and full details will be found in his thesis ..

Briefly, the Remoulding test apparatus is based on a paper ustudies on the workability of concrete'', by T.C .. Powers, 28th Annual Convention A.C.I. 1932. It consists of

17 a cylindrical :pan, 12'! diameter and 7..!..H

8 high, which can be lifted

1u

4 and dropped by rotating a cam. A standard 4ft

-

_8" X 12" slurn:p cone is placed in the centre of the pan,

filled, and then removed.. Around the cone of wet concrete 1

is then placed a cylinder with open ends,

Sf'

in diameter and 5" high, supported 2~" above the bottom of the main pan.

4

A. niston gtt in diameter connected to a 15~11 X

1.u

graduated

-.., • ' . 4 2 ~

rod sliding in a bearing aboge the centres of the two concentric cylinders, is then lowered onto theslum:ped concrete. The whole apparatus is given 1 jig :per second

3

until the :piston falls to 3₁₆" from the bottom of the main :pan, and the number of jigs is recorded as the workability. Thus the concrete is forced down around the end of the small cylinder and flows u:p between the two cylinders. The

workability is intended to give a measure of the work required ~o place the concrete in and around reinforcing bars, etc.

The Flow table is more simple, consisting of a 3011 diameter stainless steel table mounted on a frame, so it can be raised and dropped ~n by rotating a cam .. The full

description of this apparatus is contained in A. S .. T .. M. 0124-39 .. A slump cone tapering from 10" to 6~u diameter and 5n high

19 ..

The diameter or the resulting spread concrete is measured

at six symmetrically distributed positions, to

~u

and averaged. The flow per cent = _{spread diameter in inches-10 x 100}

10

However, just as important as the per cent flow, is the appearance or the spread concrete. A well-balanced mix will either remain as a well-bulged even pat, or a smooth-looking spread circle, depending on the water content. Hov~ever, a badly proportioned mix will break orr in irregular lurnps when dry, and flow with considerable segregation when wet. With pumice concrete, the flow table gave one a very good idea or

the properties or a mix.

(8) Scales.

1

These were graduated to 200 lb. up to 30 lb. and so V~Jeights could be estimated to one one-tl"lOusandth or a pound. This may seem far too accurate for concrete control, but an

accuracy or 1 lb. of cement in a yard in the field is equivalent to one-fifty-fourth of a pound in a

~

cubic foot mix. Normally,

1

weights were to an accuracy of 100 lb. but in the case of air-entraining agent the full accuracy was used.

(9) Unit Weight Container.

This container was actually the base of an airmeter, and was accura~ely calibrated to a vol11..rne of 0.196 cubic :feet, being approximately 6u diameter and 1211 _{deep ..}

(11) Crushing and sieving eguipment.

The crushing of' the pumice aggregate was carried out, using a small jaw crusher. This type of crusher was not the best :for the job, as it would not handle anything but dry pu_rnice. This resulted in a considerable amount of' dust ..

CoL~1ercial prunice crushing equipment consists or roller crushers handling moist p11..rnice.

20 ..

greater than the No.4 sieve size, and by a sieve shaker using 811

diameter Tyler sieves. All the-material ror the latter had to be absolutely rree from damp, and as large quantities were handled, the ~rocess was a slow one. The

3,t

maximum size of aggregate used was

4 .

Sieve sizes and sieving ~rocedure was as specified by A. S. T. IVL.

C-136-46:-Coarse aggregate

₄

3u

f

_{6" or No.4 (4760 micron)}

Fine aggregate No. 8 (2380 micron) No .. 16 (1190 n \

)

No .. 30 ( 590 l? ₎

No.50 t

29'7 It ₎

\.

.No.100 f

149 If ₎

\

tt2) Aggregate testing cylinder.

In dealing with lightweight aggregates, there are two methods of determining the crushing strengths of graded

aggregate:-(a) By crushing in an enclosed space under a certain fixed load, and measuring by sieve analysis the amount of crushed material ..

(b) By crushing in an enclosed space, and measuring the load to ~roduce a en .deflection.

l\11ethod (a) is in co:mformi ty IJ'Ji th recent J:nglish practice, while (b) cotlf1orms to current American px•actice .. In this case, method (b) seems to give the simplest and most practical test, so this method was adopted.

As shown on the accompanying diagram, the _cylinder is of 3~'1 out side diameter boiler stay tube, boi•ed to 3. 0311

inside diruneter and fitted with a diruneter plunger.

welded to a~" steel ~late base 6" x 6". 0

The .tube is

+

I I

~

C)

~

I

I

I

<:1

'-l

c

IS >'hov.s"rtdfh~

<'f 0"1 Inc/,

c.leoro,.,c~

PI un 9~r of M . S'.

~---.J 0 ,,

1 --315~ _ _

.l

,.,...,

Bar- J"~ -1'" 6 "1'-o <7f.St~ r

,;., ,..~,._,eu..-;,9 plu,.~e,.

Zero c/ofuh'1 ftn~ sa•t6e<l

o,.ound cy/t,.,der

Sp"'"'9 b,.oss cl,;,o..r

to hold o.T<:Q/~ f'r~e

be o~u&l-etl

Bctler .sloy 1-c,I:J,;.,'fJ bo,.ed

1-o for,..., c:tlh?der .sho"'"

h~re ; ,. por't-1q/ St!Cfio,

! - 6·0"- ' - - - ----+-'

21.

plunger was kept clean and well-oiled, it gave no trouble as J'ar as sticklng in the cylfnder ir:J concm:nerl. The scale was movable in the brass clips to adjust any sJJ.ght zero

error. 'l'he msximum loac1 of 32 9 000 1b. was put on the cylinder

without any trouble. The clearance between plunger and cylinder was not s~fficient to allow leakage of water when pumice was being tested in the saturated condition.

(a)

A

30,000 lb. screw-power, compound lever, vertical 01 sen t est:l ng rna chine was ur:Jed :for aggr•ega te testing and for bond testing.

(b) A 100-ton Amsler hydraulic vertical testing machine was used for compression testing and modulus determin-ation. Considerable difficulty was exoerienced in the use of thi.s machine.

(1) Obtaining and maintaining a uniformly slow rate of loading.

(2) Ensuring that both plattens were paraJlel. The spherical seat:lne; o:f:' the bottom platten on this mach:tne was not sensi ti. ve enougb. to take l.:tp all the Potation

ln tbe case of the low loads u.secJ in p1mrlce concrete testing. Both these factors influenced the accuracy

br

the results, but to what extent cannot be determined.

(14) ~l.iJ?nlent__;Qor dr;yi ng aggrep;at,Q~

( )

a For the drying of the whole aggregate, a

lu

4 steel plate was mounted on insulating blocks over two gas

burners. The pumice can hold such an enormous quantity of water in its voids, that drying is apt to be a slow

cess. With large quantities of pumice to be

' a ng nt would be absolutely

Two views of t' is ~pparatus are

s'~owr .

~ ~ . : • I'Al:_PETI AND CCI~ .

'"'howing various sa"JDlea of fine · ... ~~re:gate of aif~erent moiqtqre

contant.

A regat too wet , cone not slu~~eo .

regate at

S • • D . conditicn,

cone just slt'mre~.

22.

(b) For drying the Eine aggregate for moisture determinations, a. piece of' EJgutpment was 8sr;;emb1ed, whereb~v 8 r3tr•eam

of at:e :f'rorn 8 fan was dj.J:(:;cted. over a gas burner·, impingjng directly on a glass plate. TllL::l plate was

inclined at about 3QO to the air stream ~nd any fine pumice placed on the plate rapidly dried when

trowelled over: in the air stream. The texnper•at1ue was never over 150°F and so did not cause overheating.

A. S.T.lvi. TarmJer• and cone.·

These were constructEJd for obtaining a saturated, surface-dry condition of fine aggregate. The cone is of 26

gauge steel sheet o:f

1~

11 top diawete:t:,

3~

11 bottom cUamoter

?

and

28

11 111gb. '1,hEJ tam:9er bas a bottom face 111 _{in diamete:r,}

23.

SECTION TTI

Testing and hlixing ?rocedt1re.

In this section, the .Jrocedure involved in the

follo~vi11g opera tiOllS will be c1eal t ~ui

tl~:-(2) ecific gravity determination.

(3) Saturated, surface-dry condition ~etermin~tion for aggregate.

(4) Aggregate crushing strength tests.

(6) Moisture determination.

(7) Aggregate unit weight determination. (8) ii:Lxing plain ce concrete.

(9) Mixing air-entrained ce concrete.

( 10) Consistency tests on fluid concl"ete. Concrete unit eight determination. (12) Cement factor calculation.

( 13) Watel"'/ cement l"'atio calculatio •

l-: 4)

\ - - Stripping and inc~exing the concrete syecimens. (15) Curing period determination.

(16) Testing procedure for cured specimens.

(1)

Grading analysis. In every case, determination was carried out with mat othei"il'Jise :procedure Iivas

(2) Specific gravity determination. _{this is} meant the determination of the absolute specific of

the volcanic lava making up the ce ..

I11 a :.;:>reviously weighed and calibrated 25 c. c. specific

the whole being then weighed to obtain the exact weight of

the pumice. Guff1c:lent dj_r;Jtj_:LJ.cd water was then added to

half fi 11 the sf)ed :Lie gravity bottle, and the t[3.pel•cd gla::3s

cap pierced by a fine hole was then £)laced on the bottleo The bottle was then placed in a vacuum desiccator

connected by· rubber pressux•e tubing to EHJ i:"1h' r-eceiver and then

to a vacuum water _purnp. The purpose of the air vessel is to

prevent the accidental drawing of' water into the system due

to water pressux>c flJ.ctuations.

When the lowest pressure attainable (abou~ 1.73 inches of' mercury) had been roached, the desiccator and bottle were

vibrated fox• a m:lnute at a time at :llvc-mirn.J.te intervs1:3 unt:i.1 all air had ceased coming off the pumice. The bottle was

then r·olled on the bench to stir• up the pumice vdth tb.e water

and replaced in the desiccator. The pressure was once again

lowered ~::md. the whole sequence repeated until no :fu.rther ai:r•

could be drawn off the pumice.

The bottle was then conwleto1y filled with distilled

water, making sure that this was at the same temperature as

when the bottle was calibrated. Tho cap put on and the

bottle dried, it was then weighed.

Le~ W - weight of water alone bottle full

II _{" purnj_ ce}

tl _{and water after complete r·emoval}

of a1r•.

p p

(3) Satu~e~d,, sur:(~~,::dr;y condi!,ton d~teJ.12lina~ for __ ~g&r,~.

This condition (usually abbreviated to

s.s.D.)

is the moisture condition of the aggregate when the material is

saturated with water and the surface dry. ~rhe determ:i.nations for this condition were carried out as specified in A.S.T.M.

C-127-42 and 0-128-42 for coarse and fine aggregates

respectively. The S.S.D. condition is the basis for all work carl:'ied out on purnj.ce, when :L t is assmned that concH tions a1,e stable, neither javouring tho absorption nor release of water. Several tests were carried out on the absorption of water by prunice which will be described later in the thesis.

In filling the aggregate crushind strength testing cy1j_ndel1

; su:ETi cient nw. t erial is .r;rut in to fo:t:m a layer 511

deep when :Lni tially compacted. The initial compaction is accomplished by plDoing the well-oi-led plunger in the cy1inder and dropping tbe appa:r•atus

%"

to a concrete floo1, ten tlnws. Any zero error less than

~''

is adjusted, otherwise the cylinder

is x•e-i'illed. The cylinder is then placed in the ·testing machine and the plunger loaded at the uniform straining rate

of 0~60 inches per minute to a one inch deflection when the load is observed. Tho crushing strength is calculated by dividing the maxj_xnurn loacJ. by the area of the plunger·, 7.0fW

square inches. The plunger is removed after testing by using the small bax• provided, and gj.ving the plunger a sllar}?

twist.

( 5) Agtli;rega te gradill£.•

26.

most pu..mice \'VaS USed in the moist COndition, each eighed batch could have been moistened and left for 24 hours before mixing.

Eo ever, the drying and sieving equipment available would have had to be kept working seve1•al months continuously alone to separate all the .fine size ranges, to sa;y nothing o.f other people trying to use the equipment. Thus the .follovving method was used as an alternative, although small inaccuracies must have resulted.

The pumice arriving in the moist condition was carefully

and ~horoughly mixed, and the natural grading analysed. This

was compared with the desired grading and by trial and errqr, the size range vvhich would limit the guanti ty of gl"aded

aggregate determined. This was normally the

4'• -

3

a"

3 range and normally there was sufficient excess ~~~ - No. 4 size to give excess for crushing to fill deficiencies in the smaller

sizes. rhe total volurne of moist aggregate was determined and estimates made of the weights and hence vol1..1..mes of the various sizes available. (~11 grading 'Nas by volume fqr reasons given later in the thesis.) This was compared with the voltu11es o.f different gradings desired and thus quanti ties to be added or removed were obtained as indicated in the

specimen analysis following.

Grading by Volume

Corrections

Natural Desired to be

Size.

_%

Vol"LU11e

_%

Volmne Added Rejected

~~~- 19 1 .. 52 41 1..52

-

No.4 <;)t:;

""''"" 2 .. 00 22 0 .. 82 1 .. 18

No .. 4-No.S 26 2.08 13 0 .. 48 1,.60

No. 8-:N·o .16 12 0 .. 96 6 0 .. 22 0 .. 74 No .. 16-No. 30 10 0.80 6 0 .. 22 0 .. 58 No.30-No.50 4 0 .. 32 5 0 .. 19

No.50-No.100 2 1.16 5 0 .. 18 6.02

Pan

__g

0.16 2 0 .. 07 0 .. 09

':ehis grad.:tng analysis above is typical of' what

actually occurred and very close to actual f'igures with one

exception. This was that there was sometimes considerable

pumice over the

i2tt

_4- size whi.ch could .be crushed and added to the .!2.11 ₄

-

£2u

range.

8 However, even then large quantities had to be ~ejected, up to 50 per cent. In practic~, however, this d.if'ficulty coul<'l be overcome by ob:baining larger pumice,

II'Jhich ocmn~s in large quantiti.es, and crushing to aug.me.nt the lJ..11 311

-~ - -8 range.

4

As can be seen from above, roost of the re-g:r•adiDg

had. to be carried out on coarse.pumice, which was fairly easily

done without drying out all the pumice. However, the rejectfld

material had to be dried to remove the smaller fractions

clin~j.ng to it :in the damp condttionB ( 6)

All moisture determination was made by drying at a high temperature as otherwj_se it was a slow process x•emovtng

watero The excellent properties of pumice as an insulating

material mean that water is very slowly removed from the core

of the material. Usually, this was done in a metal pan on a

gas burner, heated until the bottom of' the pan was just

becoming a dull r•ed.,

( 7) Agg£~-~-1?l!i t K~~~~Jgp~~~Jer&n~?-~~l o U.

(a) Graded aggregates according to A~S.T.M. C-29-42 using

the redding procedure.

(b) The separate sizes of material were compacted. jn tbe

unit weight container by jigging with

~~~

drops on the

workability apparatus; until there was no evidence of'

compaction 1~or• the last f'i ve blovm .. The unit weight

conta:iner was smaller than usua.l, because of' the

28 ..

smaller size r•anges ..

A

pint glass jar was used with a sheet of glass as a cover for calibration, and for detecting whether full compaction had taken place ..

( 8) ~tl:l.xiDfLProcedur!:.-J?lAJ 11 pumice cone~.

Initially, the aggregate and water were brought up

to temperatu1~e. The aggregate was added to the mixer with

approximately half the mixing water, and gtven a one minute pre-mix, tn order to prevent excessive slump loss .. The rest

of the mixtng water and the cement were then added and given a four minute mix before pouring ..

(g) Mj_xj,,ng _Dl~~dure-air ent raiJJeCl_:f1UIDic~~ com:et~. Initially, the aggregate and water ~vere brou.ght up to tempel.1atu.re., The aggregate was added to the mixer.

mixing water with the air entraining agent mixed in was then added to the mixe:r:, and given a one minute pr•e-mix. The cement was then added and the whole mixed for• :four minutes befo1•e 1)ouri ng.,

( 10) .Qonsistel1CY tests on the fr•eshly poul,ed concrete. These were carried out in the following order ..

(a) Slum£ teijL~ as in A.S.'l'.M. C-143-~59.

(b) ~!QYJ.d.~,!JE;,~~ as alread~' d.escri bed.

(c) Flow test as already described.

The only point worthy of note was that at the

conclusion of each test, the concrete was returned to the tray and re-mixed by trowel befo1•e the next test ..

(11) Concr•ete un}.t w~,~ght dete~itQlJ•

This was the first test carried. out after pouring the fresh concrete. It was placed. in the unit weight container in three layers and. each layer was rod.d~d 25 times to the full depth of the layer. The surface was then trowelled. off level and the container weighed.

29 ..

then the concrete was placed in.the moulds a:f.'ter re-mixing

( 12)~ent P~c_tot~9~1l1~ul!2-tioq as

.follows:-Let W be thf:J wetght in pounds/cubic foot of concrete,

" 0 " II II II

"

of cement,

II _T II II II

"

II _{aggregate + cement + water.} 'rhen the Ceme.mt li'actor in bags/cubtc yard i.s egu.al

.to:-0~~~~7.

fo:t' a 11- cubic foot mix on the basis of 94 lb. bags of'

cement o

Effective water for combining with the cement taken

as

=

weight of' water added

+weight of water in aggregate

_. weight of water• l~egu.ired to change aggr•egRte from a dl~y

conclit:Lon to a sattuated, s1n•f'ace d:t:•y condj tion.

(14)

The concrete specimens were poured"into well-greased

moulds and stripped between 20 and 48 hours as specified by A.S.T.M. 0-192-47T. The specimens were indexed as

follows:-(a) Series denoted by capital letters

A,

B, C etc., each series representing a different g~ading of aggregate and mix type.

(b) Mixes in the series denoted by a numeral following the

capital latter, e.g. Bl, D2, 03, etc.

(c) As a convention only the heaviest specimen was used for

3 months and the lightest for• 7-,day dur:i ng0 The blocks were

labelled using 11_Dulux91 _{wh:t te u.nder•eoa t, (which 1. s ver•y x•apj d}

dl"'y:i.ng), applied wi tb a ~;" bru.sho

The specimens were cured for the following

periods:-Cornpr"'ession tests

-

7, 28, C14 days,

~/Jodulus tests

-

28 days,

The accuracy of curing periods were:-7 days + 2 hom:-s

28 days + 8 hours 84 days + 1 day.

These limits should reduce variations in strength due to -ctnder or• over curing by less tlmn 1 per eenta

( 16)

Dimensions measured to .01 inchese

End pac1d ng 3 layers of

·j~

6

u

ca:edboal"CJ or1 each end o:L

tl! e speci.men.

Rate of' load appl:tcotton 100 J.b./squa:c>e :inch/r:Jecond, which was considerably higher than that allowed by A.S.T.M.

0-39-44 wbi.ch gives 20-50 lb/sguare inch/second. This rate ·was aclopt ed to reduce the effect of sudden 1oadi lJg due to

valve adjustments; necet:1sary in the type or testtr1g machine

(e)

J,engtl1 of embedcled ba:.r:• rnea su:t•ed to • 01 t nel1es.

Hate of load 8pp1icat1.on 0.12 :tncl1es/mj,nute •

.1,~·"

Packing one .

_..

₁₆ cardboard. )

illnd p~cking as for (a).

Dof'lection of blocJ;;: measu.11ed at 2~000; '7.,000; 12,000;

17,000 lb. total Joad, the total increase beinG put on in

60 secono.s.

'I'he def'1ection:::oj were mea::m:r:oed. by 11_{MEArtens mirrors"}

whl ch measuN·:c'.l genera11~r to a stx•ai. n of' o 000197 0

The purpoElEl of the 7,000 and 12,000 lba r>ead.:tngs were

The rollo sical tests were carried

out:-1 ecific

(2) Absorption ..

ce as described in Sectio This was carried out on t

---

_{of S.G.bottle filled with}

water grams.

of S.G. e grams of bottle

c.c9

e grams

e

7'5 .. 7150 25 .. 6342 50.0808 40.9990 25.6342 15 .. 3548

ce + ~'\latel.,

Volume

e

grams 84. 557'5

u 40 .. 9890

.5685 6 .. 5123 2.,358

35.0549 10.1408 24 .. 9141 18.4286

10o 140,8

8.28'78

39.8486 18 .. 4286 21 .. 4200 3,.4941 2.372 These two results agree very well particularly

there could nave been some air sealed off' in the

centre of some of the material o:f eas

took 36 to reach

32,.

finely ground.,

Considering the :possible nature of the glass malcing up the pumice, these values seem ver~~ I'easonable.

(b) .fl .. :cmarent and true bulk specific gravi t;r.

The apparent cSogo of the ptuuice is found carT•ying out a unit weight determination~ The t~uc b.s.g. is found by correcting this value for the voids occurring bet een the aggregate particles.

No , in either case, the bullz.: specific gl"avit;;;'" is differen~ for all sieve sizes, as the proportion of

pore-spaces in the pumice decreases with decreasing size ranges. In the limit, the true basogo of the pumice reaches a constant value, equal to the true specific gravity (a), when the

material is so fine as to contain no porespaces at c:,ll ..

-The above pai"agra:ph gives the reason for gx'ading pu .. Inice aggregate by vohLme and not b:y V:Jeight. The bulk specific gravity of no::::~Lal J:"ull-weight aggregates is al::2ost completely independent o:f sieve size., Thus a ll\leight grading curve is also a vol"LUne gl"ading curve Fli th these aggregates., Then to apply a normal grading curve to pumice, it is necessary to increase the proportional weights of the various sieve sizes

in tl1e x~atio basegeof the narticular sieve size

b.sog.of the largest sieve size ' other ~SVords to gJ:ade by volw-ne ..

or in

The void determination was carried out as a sequel to determ.ining the apparent be s .. g .. o:f the aggregate in the s.s .. d .. condition .. The t weight container containing the aggregate was carefully filled vvith water and the amount o:f

water by weight added was determined.. Since the pore-spaces of the pumice ere initially filled with water then

-- weight of water added ~₁~uo

0

;S

voids ~ "

volume unit vweight container x .. 62 .. 4 ""'"

out on this assumption .. However, later work has shown this

is not so, although the variation is not great enough to cause

any serious errorsa In the absence of fuller informatj.on, ::i. t

has been assumed that the void proportion is proportional to

the size of materiaL Cornplete ver:l:l:'i.cation of th1s assum:ptj.on

was prevented by Jack of time and equipment.

_§II_ 3 F/.

·-"

211_{-No 4 No. L1-8 · No.S-16 No.16-30 No. 30-f50 No.,50-100}

4 8

e - •

(a) 39.,8 4[),. 5 48 _49.5 50~6 150.8 51.0

(b) 39.8 43.7 51.0

The proportion of voids would vary with the methods of

cornpactton used. The dtfficulty is in determining the voids

of the finer materials and the prouess becomes a very long one.

A table of' I'esul ts of deter•mi nat iorn of bulk spec:ific g:t~avi t;v

f'ollows:-Sieve size

3 3

-~"-₄

-"

₈

~

11

_-No.4

No.4--8

No.B-16

No.16-30

No.50-l00

.Apparent b.sogo

clr;y s .. d • c1.

e4065 .5270 1.Hi4 :t.l55 .786 1.118 1.226 1.300

1 .. 169

Absorption we:l.ght per eent~

48.46 48.70 38.65 14.37 12.64 1.18 Voids per cent.

• 48 49.5 50.6 50.8 5LO True b.,s.p;.

~ 67c1

L296

1e602

2.345

2$ ~}50

It can be &een that the last true bes.g. comes very close

to the true specific gravity of' 2.365 (average)

( 2) Given in the table above are the

figures for the absorption

%

to ln'ing the pumice from the dry

to the s.s.d. condition. Another test was carried out on

abso!'ption of' the coarse aggregate of' grading

"ott

(i e. greater