KM_C554e-20150630104853Dr. N.CHITHARANjAN Assistant Professor of Structural Engineering
Col!ege of Engineerlng Anna Unlversity Madras 600 025 SOUTH INDlA
T.P. KALIAPPAN Chief Englneer
Tamil - Nadu Slum Clearance Board Madras 600 005 SOUTH INDlA
ABSTRACf
The Cel!ular Concrete Plant at Madras, set up under the Indo-Polish col!abora­ tion, by Tamil Nadu Housing Board, one of the major housing organisations in India manufactures medium sized '07' type Celcrete blocks which are used for its construction activitles. In splte of the strlct quality contraI cracking of Celcrete during manufacture could not be completely avoided and it is a problem for the authorities to dispose of this waste material. This article enumerates the feasibility study of using this waste material as aggregate for the manufacture of light weight concrete precast wal! elements. The structura I behaviour of these wal! elements are experimental!y verifled and their suitabillt y for the proposed Houslng kit for mass Housing schemes are dlscussed.
INTRODUcnON
Inspite of the untiring efforts of various housing organlsations, catering the housing demand due to the growlng population in a developing country like India is a perenniel problem. Considerable research (1 - 5) has be'cn carried out by variolls research organisations in India to deve lop new construction techniques using local material for low cost housing. Many housing projects are seriously affected by the non predictable scarcity of conventional building materiaIs, dearth of skil!ed labours and due to the escalation in the cost of materiaIs and construction. To a certain extend these problems can be solved by going in for partial prefabrication techniques and by using iocai materiaIs.
The Government of Tamil Nadu, South India has launched a major housing scheme for providing shelter for Thirty Lakhs of homeless poor in three years. Tamil Nadu Housing Roard anel Tamil Nadu Slum Clearance Board are the two major Governmental organisation wh!ch are seriously involvcd in this venture
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and are attemptlng various low cost materiais and construction techniques (6). One such attempt Is the utlllsatlon of Celcrete wastes for the manufacture of light welght concrete sultable for the prefabrlcated wall panels (7). The system conslsts of precast column and panel elements whlch are jolnted together to assemble wall panels sultable for the proposed Houslng klt for mass houslng schemes. The structural behavlour of these wall panels when subjected to Inplane vertical and horizontal loads and due to uneven settlement of foundatlons are experlmentally studied. The method of assembling of the wall panel is brlefed and the economlcal feaslbIlity is dlscussed.
DESIGN OF LIGHT WEIGHT CONCRETE USING CELCRETE WASTES
CelIular Concrete Plant at Madras, set up by the Tamll Nadu Houslng Board under Indo-PolIsh collaboratlon Is intended to manufacture '07' type Cellular Concrete blocks for mass housing schemes. Inspire of the strict quaIlty control the cracking of Celcrete durlng the manufacture and handling cou ld not be avolded. This waste material could be used for the manufacture of IIght weight aggregate concrete (4).
The strength of light welght aggregate concrete (o) Is related to the strength of aggregate (o ) and that of the mortar (o ) as
a In
o = (o ) no (1-n) a m
where n Is the volume fractlon of aggregate per unlt volume of concrete, (5).
The suggested nomograms (Figure 1 and Figure i-) can be used for design of a IIght welght concrete of strength upto 14 N/mm, u sing Celcrete wastes as aggregates. F.:arller studies revealed the sultabillty of thls cüncrete to use in composlte wlth relnforcement for precast roof panels for mass houslng schemes (8,) and as wall panels for precast twln type W.C. units for sltes and services schemes (9). Therefore It Is proposed to use thls concrete for the load bearlng wall elements üf suggested Housing klt.
HOUSING KIT
The suggested houslng kit conslsts of precast components which can be procured from a centralised precasting plant, transported to the site and assembled at a faster rate wlth lesser labc)ur cost. The plan and sectional elevation of the proposed twln type model house uslng the sugges ted technlque Is shown In Figure 3. The f10w line productlon of the proposed housing kl t Is diagramatlcally shown In Figure 4. The objectlve of the present study is to manufacture Individual precast wall and column elements uslng celcrete waste aggregate concrete and to assemble prefabricated walls. These walls will be tested for the followlng loading condltlons:
-----.
-
~ 12.0 w a:: tii 10.0 w > üi ~ 8.0 a: a.
"" r'\. '\..
'\.. r'\..
"
I 1
8 6.00.6 0.8 1.0 1.2 1.4 1.6 f'... I ./ 1
I ./ w 0.0 w
~ 4.0 4 W/C RA TIO 8Y WEI6HT ! V w ~
FIG.1 RELATlON BETWEEN COMPRESSIVE STRENGTH ANO WATER CEMENT RATIO FOR CELCRETE WASTE AGGREGATE CONCRETE
r I
~ 9.0 ~ ~ ~O ~ ~ 5.5 8.0 w 4: 6.0 8.0 10.0 12.0 14.0 16.0 "" 8 COMPRESSIVE STRENGTH N/mm2 u.
FIG.2 A DESIGN CHART CONNECTING QUANTITlES OF VARIOUS MATERIALS REQUIRED FOR CELCRETE WASTE AGGREGATE CONCRETE
C.lcr.t. wast. aggrogat. panol roofs
Flooring
R.C.C.l:8.16- ;,";; 1
'" N o
V V =_-:-:.w= _..:.:=-::=-_- = :-.=c==<=-
O o t-o 45_i 100_0 r )(X~ si 1000 ,f 1000 ~ -lõ~j PLA N
-1 W:
FOUNOAnON
Pr~st \Vali Elemenu
joisu or 2. Cela,etc Reln!orc~d
A,r.rel.~t~$te AerO<""..!cte
Cuncrete Panel (lei
SUGGESTED LOW COST
HOUSlNG KIT 1
FlN1SHfNG
Colour
Whlte
Wuh
FIG.4 FLOW lINE FOR ASSEMBlING A TYPICAL HOUSING KIT r a5 A-i -
(a) WASTE AGGREGATES
(b) COLUMN MOULD
---
Mlx Deslgn
It is proposed to manufacture hal f scale models using Celcrete waste aggregate concrete. Celcrete wastes obtalned from the Cellular concrete Plant, Madras Is hand crushed to the require2 slze and used as aggregates (figure 5a). A concrete of strength 7 N/mm is arrlved at uslng figure 1 and figure 2. Locally avallable river sand and ordlnary Portland cement are used. fo'r mlxlng and curing potable water Is used. Two types of wooden moulds are used (Figure 6).
Manufacture of coIumn elements
The details of the reusab!e mould can be seen from figure 5.b. A central rod of diameter 20 mm Is held vertlcally during the casting as shown in Figure 5.c and as sooo as the mlx sets, this rod is removed to induce the duct whlch Is used to provide relnforcernent for the column durlng the assembling of the panel. Samples are water cured for 28 days anú each pane! of slze 1.5 m x 1.5 m requlre 16 column unlts.
Manufacture of wall elements
Same mix Is used for wall elements also. Samples are cast on leveI ground using detachable wooden forms (figure 5.d). After three hours the slde forms are removed (figure 5. e) and reused. The samples are water cureú fOí 28 days.
Castlng of base beam
To simulate the pllnth beam at the slte a reinforced concrete beam of slze 1600 mm x 100 mm x 30 mm (figure 7) Is used for the assemb!y of the test samples. At speclfled spacing 10 mm dia meter rods are extended from the base beam whlch wl11 serve as gulde for allgning the columns and to serve as column relnforcement. Using cast Iron plpes of 40 mm dlarneter holes are provlded at speclfled spaclng to anchor the wall element to the test bed.
Castlng of rlb elements
A seperate relnforced concrete contlnuous ribs of size 1600 mm x 50 mm x 50 mm relnforced wlth 4 numbers of 6 mm diameter ml1d steel bars as maln reinforcement and 6 mm dlameter rlngs at 150 mm c/c as Shear reinforcement, are casto This rlb is Inteoded for the pro per distributlon of load over the panels.
Assembly of prefabrlcated wall elements
Three numbers of Wall Panels of slze 1600 mm x 1600 mm x 50 mm are assembled as descrlbed below (figure 8).
6
x
-j 1-12
---I 75 t---
T .1 100
PLAN (a)MOULD FOR COLUMN ELEMENT
'--175~
Rings 6mmj1! MS aI 20mm CC
6 nos of 12 mm j1! R T S
D3 I. 1600 .1 ~
--..
.. .. • .. ..
(c) PANELS INSERTED (d) SECOND LAYER (a) ASSEMBLING IN PROGRESS
• .. (.9) TOP RIB FIXED
FIG.S ASSEMBlING WALL PANELS
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o Fixed the base beam on the test bed with suitable anchorages. (Figure 8.a) o Align the vertical rods extended for the base beam and insert four
numbers of column elements. (Figure 8.b) o Insert the panel elements through the grooves ava!lable in the column
elements and groutwell uslng 1:3 cement mortar. (Figure 8.c) o Insert the second and thlrd layer of panels by whlch the panels extend
over the helght of the column elements. Insert the second layer af column elements. (Figure 8.d)
o Repear the process tlll the celllng helght Is reached. (Figure 8.e) o If necessary spec!ally cast half wall panels may be used at the top levei. o Insert the top horizontal rlb through the holes provlded to accomodate
relnforcement from the column elements. (Figure 8. f and Figure 8.g.) o Check the vertlcallty of individuai elements as well as panel a whole unlt
and grout the jolnt.
Cure for 7 days by spraylng water before load testo
The deta!ls of assembly of the wall panel for settlement study Is the same as that of the earlier samples, except for the depth of the base beam is reduced to 100 m m.
TESTING
Three numbers of samples are tested In the Test bed ava!lable in the Structural Engineerlng Divislon. The samples for lateral load test Is firlnly connected to the test bed. The disc type of dlsplacement meters are used to measure the deformatlon. Rectangular Rosettes are pasted at specifled Intervals on the surface of the wall panels for measurlng the straln variatlons for incrementaI loadlng.
Testlng of Wall Panel for Inplane VertIcal Loading
The load Is applied through a loadlng tree to slmulate unlformly dlstrlbuted load uslng a 20 tonnes Hydraullc jack and a provlng rlng (Figure 9.a). Panel deformatlons are measured at every 0.25 tonnes Increment of load and the straln varlatlons are noted for every 2 tonnes Increment of load. The first crack. appeared at a line load of 25 KN/metre run over the wall panel and the sample failed at an equlvalent line load of 38.40 KN/metre run. Though the first crack appeared In the vertical dlrectlon the final fa!lure was due to horizontal jolnt failure due to the buckllng of the wall panel (FIgure 9.b). The varlatlon of principal stralns on the surface of the panel was negllglble. Treatlng as a slngle storey bullding wlth flat roof but wlth no access, the service load works out to 13.5 KN/metre run Inclusive of dead loads. Even the observed cracklng load (25 KN/metre run) is 1.85 times the anticlpated ser vice load. Thls test revealed the suitablllty of this wall panel to use In low cost houslng conslderlng the strength cri teria beca use the panel was Intact even after testlng (Figure 9. b.).
Testlng of Wall Panel for Inplane Lateral Loadlng
The dimenslons of thls test sample Is similar to the earlier one and is rlgldly anchored to the test bed. Uslng a 5 tonnes hydraulic jack anel provlng ring lateral load is applied at the top horizontal rib. Lateral deformations are measured uslng disc type displacement meters and correctlons are made for the upli ft of the panel as a whole. The first horizontal crack
, " " l~'
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FIG.9 TESTED SAMPLES
(o) FAILURE DUE TO BASE BEAM
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appeared at about 30 percent of the ultimate load levei (8.50 KN). On further loading subsequent joints failed and at about 88 pe r cent of the ultimate load levei vertical seperation between the column a nd panels are wltnessed. Lateral deformatlon behavlour of the panel Is shown In Figure 10. Rosette readings could not give substantial information. The fallure is initiated by propogative horizontal cracks followed by vertical seperation of column and panei (Figure 9.c). Th is study e nlightened the struc tural safety of the panel against accedental iate ral ioads.
Testlng of Wall Panel for uneven Settlement
To lnduce uneven settlement thls panel Is supported on rollers with equal ove r hang on both sides and is subJected to inplane vertical ioad. The flrst c rack appeared at 0.53 times the ultlmate load ievel (60.32 KN/metre run). Upto 74 percent of the uitimate load leveI the buckllng was not so serious (Figure 11). However at about 87 percent of the ultlmate load le veI the lateral buckllng was predomlnent. The first vertical crack appeared at 0. 38 times the ultirnate load levei and extended towards the overhang support at 0.83 times the ultlmate load levei and the overhang falled a t the ultimate levei (Figure 9.d). The settlement of the wall pane l is shown In Figure 12. The monollthic behaviour of the \vall elements are evident from the principal stress contours shown in Figure 13. The behaviour of this panel is similar to the panel tested without settlement. This test revealed that inspite of the increased number of joints the provision of base beam which s imulate the ca;:Jplng beam at the site ellminates the catastrophical failure o f the structure (Figure 9.e).
Testlng of lsolated Column Elements
A full scaie column of the same mix and of height 3.0 m is cast uslng the same principIe and tested to destruction. The test sample could carry 99 percent of the ultimate load that could be carried by an identical column cast monolithlcally. Thls study also revealed that the provlsion of reinforce­ ment at the ce ntre for the column has not seriously affected stre ngth provided the eccentricity of load is ellminated.
CONCLUSIONS
Celcrete Wastes as Aggregates for Concrete
o The suggested nomograms can be used wlth confldence for mix designo o Conventionai brlck work can be replaced by this concrete. o Earlier studies revealed the suitabillty of this material for relnforced
structural elements.
Precast Elements
---
10 20 30 Deformation in mm
1.00 Pu'
1000 1600 500
1 lf . o o
FIGlO LATERAL DEFORMATION ;:F A WALL PANEL DUE TO INPLANE LOAD
0. 19 Pu' O.35Pu·
T Bale I beam
( li ) W ithoul slZttlement
p
300 nJ
FIG.11 BUCKLiNG OF WALLS DUE TO INPLANE VERTICAL LOADS
U ltimate load Pu' ~ 95.50 kN
1000 - ---....... ,- 300-.
FIG.12 DEFLECTlON PROFILE OF A BASE BEAM EXPERIENCING UNEVEN SETTLEMENT
FIG.13 MAXIMUM PRINCIPAL STRESS CONTOUR FOR VERTICAL INPlANE LOAD (40 kN)
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Prefabricated Panels
o Panels could be assembled at a faster rate. o Panels and column elernents could be jointed using 1:3 cement mortar and
the same mortar can be used for grouting the column ducts.
Structural Behaviour
o Inspite of the slenderness the precast wall elements could withstood without buckling a load equal to 1.85 times higher than that of the design service load.
o The wall pane! was intact upto 80 percent of the ultimate lateral load levei.
o Inspite of the uneven settlernent the perfect composite behaviour of the elements in the wall panel was witnessed upto 80 percent of ultimate load leveI.
Behaviour or lsolated Column
o The load carrying capacity of the assembled column is comparable with that of the monolithic one.
o For axial load without eccentricity the provision of reinforcement in the central core of the column is permitteri.
Housing Kit
o The required precast components for a twin unit can be easily transported to the site in a 5 tonnes lorry.
o Complete structure above foundation can be assembled in a weeks time. o Door and Window openings can be provided by suitably eliminating the
panels at the requireri spaces. o Precast lintel cum sunshade can be provided for door and window openings. o By providing suitable joints plastering can be eliminated.
General
o Suggested technique is 30 percent cheaper than conventional brick construction.
o Adoption of this technique leads to effective disposal of CeIcrete waste.
ACKNOWLEDGEMENT
Authorities of Anna University, Madras, South India, are thanked for extending the laboratory facilities to carry out the study.
Authorities of Tamil Nadu Housing Board and Tamil Nadu SI um Clearance Board are acknowledged with thanks for their constant encourage- ment in this study.
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REFERENCES
1. Vashneya,] .K. and Mathur,O.N., 'Hand Book of Rural Housing and Village Plannlng' National Bulldlng Organisation, Mlnlstry of Works, Houslng and Supply, New Delhl, 1963, pp. 36-44.
2. Chitharanjan,N. , 'Long Span Br!ck Panel Roof for Mass Hous!ng', the Ind!an Concrete ]ournal Vol.60, No.l, january 1986, pp. 9-14.
3. Chltharanjan,N., 'Development of Llght we!ght Concrete and the!r Appl!cat!ons to the Reinforced Flexual Members', A Ph.D. Thes!s approved by the Un!verslty of Madras, May 1980, pp. 16-42.
4. Chltharanjan,N. and Kumaresan,S., 'Design of Llght weight Concrete using Industrial Wastes', Proceedings of the IAHS International Conference on Housing Problems In Developing Countries, Dehran, Vol.II, December 1978, pp. 123-130.
5. • ..................... . , 'Proceedlngs of the Flrst Internatlonal Congress of Llght ~elght Concrete', Cement and Concrete Assoc!ation, London, Vol. lI, May 1968, pp. 12-30.
6. Kaliappan,T.P. and Chitharanjan,N., 'A Socio Economic Approach for Provlding Shelter for the homeless', Proceed!ngs of the IAHS World Congress on "New Trends on Hous!ng Projects Emphasising Developlng Countries", Miami, Florida, Dec. 14-20, 1986.
7. Padmanabhan,N., "Development of a Low Cost Hous!ng Kit", A M.E. Thes!s approved by the Anna University, Madras, j anuary 1988, pp. 1-117.
8. Chitharanjan,N., 'Utillsat!on of Celcrete Wastes for Low Cost Rooflng Elements', a Research Report submitted to the Tamil Nadu Housing Board, Madras, ] uly 1986, pp. 1-35.
9. Chltharanjan,N., "Prefabricated Twin Type W.c. Unlts for Sltes and Servlces Schemes", a Research Report subm!tted to the Tamil Nadu Housing Board, Madras, jan. 1987, pp. 1-25.
10. Chitharanjan,N., Sundarargan,R., Devadas Manoharan,P., 'Development and Applicat!on of Aerocrete with Non-metalIic Fibres', Proceedings of the International Symposium on F!bre Reinforced Concrete, VoI. lI, Madras, Ind!a, Dec. 16-19, 1987, pp.7.63-7.74.