development of an innovative interlocking load bearing hollow block system in malaysia

Construction and Building Materials 18(2004) 445–454

0950-0618/04/$ - see front matter� 2004 Elsevier Ltd. All rights reserved.doi:10.1016/j.conbuildmat.2004.03.013

Development of an innovative interlocking load bearing hollow blocksystem in Malaysia

Waleed A. Thanoon, Mohd Saleh Jaafar*, Mohd Razali Abdul Kadir, Abang Abdullah Abang Ali,D.N. Trikha, Amad M.S. Najm

Serdang, Darul Ehsan, Malaysia

Received 17 April 2002; received in revised form 14 February 2003; accepted 9 March 2004

Abstract

The paper describes the development of a new interlocking hollow block masonry system appropriate for load bearing masonrywall construction. The developed system is an alternative to the traditional bonded masonry system where the blocks in the wallare integrated through mortar layers. In the system developed, the blocks are stacked on one another and three-dimensionalinterlocking protrusions are provided in the blocks to integrate the blocks into walls. This paper includes the background, conceptand procedure used to develop an efficient interlocking hollow block system, which may be used in the construction of loadbearing walls. Twenty-one different block models have been investigated and analysed with respect to weight, bearing and shearareas, shape, ease of production, ability to accommodate vertical and horizontal reinforcing stabilising ties and efficiency of theinterlocking mechanism under imposed loads. The blocks, developed under the name ‘PUTRA BLOCK’, have been used toconstruct a single-storey house at Universiti Putra Malaysia. The system provides a fast, easy and an accurate building system.� 2004 Elsevier Ltd. All rights reserved.

Keywords: Masonry system; Putra block; Interlocking load bearing hollow block; Dry construction; Modular coordination

1. Introduction

The use of structural masonry may result in cheaperand faster construction compared with framed buildingconstruction for low-rise buildings. Interlocking hollowblock (IHB) system is promoted as a new buildingtechnique that may result in even greater economy. Theuse of interlocking load bearing hollow blocks in build-ing construction speeds up the construction process as aresult of the elimination of mortar layers. Further, dueto the self-aligning features of the interlocking hollowblocks, the walls can be assembled at much faster speedcompared to mortared masonry construction. In Malay-sia, the supply of houses by both the public and privatesectors is still far from meeting the demand especiallyin low cost housing sector. The proposed system usinginterlocking hollow blocks (IHB) may provide thesolution to overcome this shortage as these blocks can

*Corresponding author.E-mail address: [email protected](M.S. Jaafar).

be used in the construction of both non-load bearingand load bearing walls.The main feature of an IHB system is the elimination

of the mortar layers as the blocks are interconnectedthrough key connections(protrusions and grooves). Theinterconnections between the blocks have to be designedto withstand the stresses, which develop in a wall underapplied loads.In the development of the new interlocking block

system, the following features are sought to be included:

● Efficient interlocking mechanism in different direc-tions to withstand the different forces(shear andbearing), which develop under applied loads.

● Self-alignment to ensure accurate and simple con-struction.

● Meeting modular coordination requirements.● Construction of both load bearing and non-load

bearing walls.● Production is similar to that of normal hollow blocks

so that the manufacturing machinery is easilyfabricated.

446 W.A. Thanoon et al. / Construction and Building Materials 18 (2004) 445–454

Fig. 1. Interlocking block developed by R. Thallonw10x.

Fig. 2. Haenar Interlocking Systemw6x.

2. Background

There have been several attempts to develop mortar-less hollow blocks in different parts of the world in therecent past. R. Thallonw10x developed interlockingblocks, which were used to construct a single-storeyhouse. These interlocking blocks used are shown in Fig.1. During the manufacturing process, the blocks arepassed through a machine that grinds the top and bottomsurfaces to a tolerance of 0.12 mm. These parallel andsmoothly ground surfaces allow the blocks to be laid upwith ease without mortar. The blocks also have maleand female interlocking mechanism at their sides to help

align and secure them during placement. Grouting isused to finally fill all the cores.In the Haenarw6x interlocking hollow block system,

for the construction of load bearing walls, three typesof blocks are used as shown in Fig. 2, The alignmentin Haenar blocks is achieved by providing interlockingkeys at the sides, while the interlocking between theblocks is ensured by providing a key(small projection)at the top of the blocks in addition to the inside inclinedweb at the bottom. The inside web acts as a support tothe top key to interlock the blocks. This interlockingmechanism is efficient to ensure self-alignment and easyconstruction. Both horizontal and vertical reinforcement

447W.A. Thanoon et al. / Construction and Building Materials 18 (2004) 445–454

Fig. 3. Mecano Interlocking Systemw5x.

Fig. 4. Modified ‘H’ (a) and ‘W’ (b) Block Masonry System developed at Drexel Universityw7x.

embedded in grout has been recommended to be placedat suitable intervals for load bearing walls.In Peru, a system called Mecano block system has

been developed by Cetholicw5x in which no interlockingis provided so that the blocks are simply stacked oneach other as shown in Fig. 3. All the voids providedin the blocks are then grouted after the placement of thehorizontal and vertical reinforcement in their positions.The blocks must have accurate dimensions and smooth-ness. A tolerance of 0.5 mm is obtained through mould-ing under pressure. The shape of the blocks allowstwo-way hollow cores for introducing the reinforcement.The horizontal reinforcement is placed during stackingof the blocks while the vertical reinforcement is placedafter stacking the blocks for the complete wall. Thehollow cores are then filled with concrete grout tocomplete the reinforced masonry wall. The concrete

grout ingredients are the same as those used in normalconcrete with the extra requirement that the grout musthave a high degree of workability.w7x for reinforced masonry construction, which is ableto resist earthquake. The first of the two systems is asimple modified H-block shown in Fig. 4a, with tongueand groove interlocking on both the bed and head joints.It can be reinforced in both vertical and horizontaldirections. Partial grouting is required to ensure thestability of the wall during construction prior to fullgrouting.The second system is the W-block interlocking sys-

tem, shown in Fig. 4b, which also shows the possiblehorizontal and vertical reinforcement and the stackingof the units. The horizontal joints between the coursesare staggered by using different block heights. Threedifferent types are required to construct the walls.However, the vertical joints are made continuous alongthe height of the wall.In Malaysia, Abang Abdullah et al.w1x developed

another interlocking hollow block system, as shown inFig. 5, based on the LEGO system. Individual blocksand full-scale walls have been tested at Universiti PutraMalaysia for different types of loading. It has beenfound that the compressive strength of the individualblocks satisfies Malaysia code requirementsw9x. Thedeveloped IHB can be used for two-storey building witha good margin of safety.Mirasa et al.w2x investigated the structural behaviour

of a new shape of interlocking block system developedat the Universiti Teknologi Malaysia. The block chosenhas two-core of voids as shown in Fig. 6. The middleweb thickness is twice the outer web thickness. Theouter dimensions of the block are 200(B)=150(H) and


Fig. 5. Interlocking Hollow Block System, Universiti Putra Malaysiaw1x.

Fig. 6. Interlocking Hollow Block System, Universiti Teknologi Malaysiaw2x.

400(L) mm but these do not comply with the require-ments for modular dimensions.From the above review on the development of the

interlocking hollow blocks in different parts of theworld, it can be concluded that:

1. In most of the IHB systems, the interlocking mech-anism has been used for the alignment of the blocksto speed up the construction and to reduce the labourrequirement. The interlocking keys alone are not ableto resist the stresses, which develop under designloads due to the elimination of mortar layers.

2. Some of the IHB systems have been used to providea permanent formwork for casting reinforced concretewalls.

3. Horizontal and vertical stabilising ties in the form ofreinforced concrete beams and columns embedded inthe wall can be cast within the hollow cores insidethe block.

4. However, a number of IHB systems do not providecontinuous hollow spaces(vertical andyor horizon-tal) to host ties in both directions.

5. Most of the IHB available requires a complicatedmould for casting in addition to the complicated andexpensive production process.

It is therefore necessary to develop an IHB system,which overcomes the present limitations as indicatedabove. The newly developed system should satisfy thestrength requirements and have ease in production andconstruction features.

3. Choice of block configurations

A number of block models have been configuredalong with their interlocking mechanism as shown inFig. 7, the major design consideration being that theblocks are able to resist all the forces, which develop inan assembled wall. The applied loads have been calcu-lated for a five-storey residential building construction.The factors considered in the analysis of different

block models are the weight, the bearing and shear areasprovided by the block to resist vertical and lateral forces,the interlocking mechanism if uni, bi or three-dimen-sional in nature and the ability of the blocks to hostvertical and horizontal stabilising ties easily. Moreover,two groups of blocks have been investigated, the blocksin Group 1 have block dimensions of 400=200=200mm while the Group 2 blocks have the dimensions of400=200=100 mm. The detailed investigation is pre-


Fig. 7. Different Interlocking Hollow Block Models, studied at Universiti Putra Malaysia.

sented in Ref.w11x. The investigations have led to thefollowing conclusions:

1. All of the blocks in Group 1 provide sufficientbearing and shearing areas to resist the design verticaland horizontal forces, while blocks in Group 2 havea small bearing area sufficient for the constructionof partitions walls.

2. The weight of the Group 1 blocks is rather high(greater than 20 kg) and for South–East Asianworkers, the blocks may be considered as unduly

heavy. The weight may reduce productivity signifi-cantly.

3. Most of the blocks provide sufficient interlockingmechanism in two directions with sufficient resis-tance to the forces developed in the construction ofone- to two-storey buildings.

4. Some of the blocks are suitable for manual produc-tion but may require complicated moulds.

It needs to be emphasised that in addition to thestrength requirements, the production of the blocks and


Fig. 8. Putra Interlocking Block System.

Fig. 9. Interlocking mechanism along with the bearing and shear areas provided by the main block unit.

Table 1The physical properties of different block units

Block type Block dimension(mm) Average weight Solid volume Bearing area Shear area in major Shear area in minor

Length Width Height(kg) (m =10 )

y3 3 (mm )2 direction(mm )2 direction(mm )2

Stretcher 300 150 200 13 5.72 24 000 12 200 4200Half 150 150 200 8 3.78 12 000 962 962Corner 300 150 200 14 6.23 24 000 1924 1924

the constructability of the walls using the block areequally important factors to be considered in the devel-opment of the blocks. In the development of the newinterlocking block system, the following featuresyadvan-tages are sought to be included:

● Efficient interlocking mechanism in different direc-tions to withstand the different forces(shear andbearing), that develop under applied loads.

● Self-alignment to ensure accurate and simpleconstruction.

● MeetingModular Coordination requirements, i.e. thedimensions should fit into the modular dimensions,

i.e. horizontal planning dimensions of 3M and verti-cal planning dimensions of 1M, where 1Ms100mm.

● Construction for bothload bearing and non-loadbearing walls.

● Production is similar to that of normal hollow blocksso that the manufacturing machinery is easilyfabricated.

● Light weight with an average weight of 12 kg perblock.

● No formwork is required for construction, so it maybe environmental friendly.

● Dry and fast construction, with minimum in-situcasting.

4. Putra interlocking block system

Based on the study of the above configurations andto achieve the objectives of ease of production andconstructability as well as to satisfy modular coordina-tion requirements, a new configuration with differentdimensions has finally been developed called PutraInterlocking Blocks. These blocks have three differentconfigurations as Stretcher Block, Corner Block andHalf Block (Fig. 8). The interlocking mechanism in anydirection is ensured through providing a protrusion of20 mm height. The physical properties of differentindividual block types are presented in Table 1. Thestretcher block is the main unit used in the constructionof the wall. The Comer block unit is to be used to fit


Fig. 10. Schematic drawing for stages of wall construction using the Putra Block System.

at the junctions and the end of the walls. While the Halfblock is used to complete the courses of the wall sothat vertical joints will be staggered. The interlockingmechanisms have been designed to obviate the need formortar layers, so that the construction speed may beincreased. The self-aligning features add to the increasein the speed of construction.The block dimensions are in conformity with the

modular design rules, which require that the horizontal

controlling planes to be in modular dimension of 3M or300 mm, and the vertical controlling planes to be 1Mor 100 mm. The Half Block with the length of 150 mmcan be conveniently put in the technical zones of 150mm. This allows other spaces in the house to havemodular dimensions, thus facilitating the use of othermodularly coordinated components such as windows,doors and built-in cabinets. It could be seen also that ifthe typical room heights of 2800 or 3000 mm are


Fig. 11. Schematic drawing for corner walls and walls with opening construction.

adopted, there is not a single block that needs to bebroken to fit into the spaces required. There will be nowastage in the materials, and indeed, exact number ofblocks required for a specific house could be estimatedfrom the architectural drawing.The configuration and the interlocking mechanism

can easily be produced using a normal block makingmachine giving special consideration to the mould used,concrete mix and vibration time. The compressivestrength of the tested individual blocks is 94.6–118%of the concrete cube cast using the same mix. Thedeveloped blocks have been analysed theoreticallyw8xand experimentallyw3x. The theoretical analyses andexperimental results cover the structural behaviour ofthe prisms as well as full-scale wall panels undervertical, lateral and eccentric loads.The compressive strength of masonry walls is the

most important parameter in the design of masonrystructures and primarily depends on the strength of theblock units. The strength ratio of the interlocking basicwall panel whaving dimensions of 1.2 m(width)=1.2m (length)x in terms of the average compressive strengthof the main block(stretcher) unit is found to be equal

to 0.39 (the average strength of the stretcher block isequal to 15.2 Nymm ). This is complied very well with2

the strength ratio of traditional bonded masonry wallpanel. The strength ratio of the basic panel for bondedhollow block masonry with mortar layers of differentdesignation and block unit strength equal to 15 Nymm obtained using BS 5268: Part 1w4x are 0.45, 0.42

and 0.38 for mortar designation(i), (ii) and (iii ),respectively.The interlocking mechanism plays a significant role

in the distribution of the stresses developed in the blockdue to the applied load. The deformed shape obtainedfrom finite element analysis of the interlocking blocksystem under axial compression load(Fig. 9) showsthat, there is an interaction between different block unitsthrough their interlocking keys, which in turn leads tohigher stress concentration near the web-shell intersec-tion. The connected parts of the blocks will resist thestresses developed in the wall due to the applied loadto integrate the blocks in the wall. The webs providelateral resistance to the shells and hence the deformationnear the web-shell intersection is minimised and highstress is expected at these junctions.


Fig. 12. Sequence of house construction using Putra Block System.

Walls can be constructed using minimal unskilledlabour. In addition, the assembled blocks in the wallprovide continuous hollow voids, which can be used tohost stabilising ties in vertical and horizontal directionsas shown in Fig. 10 to enhance stability and integrityof the system. At the corners or junctions of walls, theconnectivity between layers is achieved at subsequentlayers, as shown in Fig. 11. The interlocking hollowblock system, as developed, has been employed effi-ciently to construct a single storey house as shown inFig. 12. The reasonable weight and the simple shape ofthe blocks render the system to be friendlier to theworkers.The construction of the 60 m house shows a 30%2

reduction in the construction time as compared to thetraditional system. Unskilled labour, although unfamiliarwith the system, found the system to be simpler andeasier to work with. No formwork has been used in theconstruction of the entire house. The lintels are embed-ded within the block which further reduces the construc-tion time was shown in plate(f), Fig. 12x.

5. Summary and conclusions

This paper presents the development of a new inter-locking hollow block system. Different interlockingblock system used in different parts of the world havebeen reviewed and discussed. In an attempt to evolve anew and innovative system, a number of block config-urations have been studied for their structural perform-ance as well as their interlocking mechanisms.Accordingly, a new interlocking block system named‘Putra Block’ has been developed. The main features ofPutra Block System are:

1. The Putra Block dimensions satisfy the modularcoordination requirements.

2. The shape of Putra Block is simple, resulting in easyproduction and easy assembly of the wall.

3. The interlocking mechanism provided by Putra Blockis sufficient to interlock the assembled blocks indifferent directions.

4. It is a self-aligned construction system to ensureaccurate and fast construction.


Acknowledgments

The authors of this paper acknowledge the financialassistance from the Ministry of Housing and LocalGovernment, Malaysia without which this block systemcould not have been developed. Special thanks to MrsDang Anom Bt Mohd. Zin, Principal Assistant Director,Research and Development Division, Ministry of Hous-ing and Local Government for her continuous supportand encouragement.

References

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w3x Najm AMS. Structural behaviour of load bearing interlockinghollow block masonry. M.Sc. Thesis, Faculty of Engineering,Universiti Putra Malaysia 2001.

w4x British Standard. BS 5628: Part 1. Unreinforced Masonry,1978.

w5x Cetholic. Mortarless Masonry—The Mecano System, HousingScience, Vol. 12, No. 2, Lima, Peru, 1988: pp. 145–157.

w6x Haener . Stacking Mortarless Block System. Hamilton, Ontario:Engineering Design Manual by Ikinson Engineering, Inc, 1984.

w7x Harris HG, Oh K, Hamid AA. Development of new interlock-ing and mortarless block masonry units for efficient buildingsystems. In: Proceeding of The Sixth Canadian MasonrySymposium. Drexel University: Saskatoon, Canada, 15–17June 1992.

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w9x Malaysian Standard. MS 7.2: Specification for precast concreteblocks, 1971.

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development of an innovative interlocking load bearing hollow block system in malaysia

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