12TH I NTERNATIONAL BRICK/BLOCK Masonry. DEVElOPMENT OF THE PRODUCTION TECNIQUES OF THE SMAll SCAlE CONCRETE BlOCKS

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1 12TH I NTERNATIONAL BRICK/BLOCK Masonry c O N F E R E N C E DEVElOPMENT OF THE PRODUCTION TECNIQUES OF THE SMAll SCAlE CONCRETE BlOCKS J. S. Camacho 1, R. P. Andolfato 2 'Assistant Professor (Ph.D.). ' Structural Engineer 'Department of Civil Engineering Professor, Ilha Solteira College, Ilha Solteira, SP. Address: AI. Bahia, 550 CEP: Ilha Solteira - SP - BRASIL jefcam@dec.feis.unesp.br ' Department of Civil Engineering Graduate Student, Ilha Solteira College. ABSTRACT This paper describes the production technique development of the (7 :4) scale modeled concrete blocks. These blocks were tested with different compacity degrees, in the best way to reproduce the prototype patterns. Axial compression tests were executed on blocks and on prisms. The compression strength, and the rupture type were measured and compared for ali specimens. The procedures adopted on the tests, materiais preparation, mortar chosen and results outputs are completely described. The results are shown through tables and graphs forms and discussed in this paper. Key words: Masonry, Concrete, 8lock, Structural, Model, Small-Scale. 385

2 1. INTRODUCTION The knowledge obtained about structural masonry, came, usually, from the realized experimental analysis, in most cases, at the research centers. It is obvious that the tests on real scale blocks, and even on real scale prisms, are viable and are very applied until these days. However, the tests for determination of the walls behavior or high complexity structural elements are difficult to construct, as well it is expensive. Consequently, the small-scale model utilization that answers like the real model became indispensable. This work intention is to describe the production techniques used for small-scale models production, and, besides that, compare the results of the compression strength tests obtained for different degrees of compacity, and also a relation between real scale blocks and prisms and small-scale ones. 2. CONCRETE BLOCKS PRODUCTION In the (1 :4) small-scale blocks manufacture, was employed a small equipment developed at Civil Eng ineering Laboratory of Ilha Solteira College, as seeing in figure 1. Having the status of first prototype, the PVC was the basic material, because of its easy handling property. The developed mechanism was fixed over a vibratory table for superior compacity conditions. In the production process the mixture was introduced inside the shape, and at the same time manually hard-pressed and vibrated. Subsequently, the blocks were stored at humid room where they were kept until the test date. The (1:1) real scale blocks were produced at a commercial factory, which provided ali required information about the used mixture. Ali geometric characteristics of the blocks were reduced linearly, even the apertures, which present con ic characteristics. Figure 2 shows two models in both scales Mix employed on the blocks fabrication The sand used in the small-scale block production was sieved on the net #0,42mm and the gravei used was the one that passed by the net #2,OOmm and retained into the net #1, 19mm, trying to keep the (1 :4) relation between these materiais while reducing the real scale block. 386

3 Figure 1. Mechanism of Small-scale 810cks Fabrication. Figure 2. Relationship between scales. 387

4 The cement used in the fabrication of the (1:4) blocks was the same employed in the real scale ones, which was the HIS - Cement of High Initial Strengths. The proportion between the employed materiais is the same exhibited below. eement: 15m/ -7 23g. 1 water: 12ml -7 12g mlxture : sand: 81 m/ gravei: 54ml -7 76g 2.2. Block compacity degree determination For an in itial situation of the compacity degree to use in the blocks manufacture, it was established the real scale block apparent density, making a relation between its mass and its gross volume (V = h x w x t), and getting a medium value of k= 1,296g/cm 3 This value helped to characterize the mass to be employed in the fabrication process of the small-scale concrete blocks, determining so, the compacity degree of them. According to the calculus, the right mass to use in the production of the small-scale blocks was approximate 156g. VB 7714 Vb = - = -- = 120 5em) P = V x k = 1205 x = 156 2g ' ", Being the manufacture a hand process, it was necessary to work with a lower value than the one determined above. Because of the hand-press difficulty, different degrees of compacity was used, its value is showed below. - BL 1-133: these are blocks made of mixture1 with initial mass 133g. - BL 1-135: these are blocks made of mixture1 with initial mass 135g. - BL 1-138: these are blocks made of mixture1 with initial mass 138g. - BL 1-140: these are blocks made of mixture1 with initial mass 140g. 3. MOlDING THE PRISMS With the intention to proceed an initial study of the compression strengths, an amount of prisms were built with three blocks each, in both scales (1 :1) and (1 :4), as showing figure 3, and they were tested until the rupture. While modeling those prisms, ali parameters relative with the labor that interfere in the final results were controlled, such as, mortar bedding thickness, plumb and leveling. The mortar used at prisms modeling was prepared with 1:1 :6 parts of cement, lime and sand. It was employed medium sand at (1:1) scale prisms and fine sand at (1 :4) scale prisms. 388

Figure 3. Prism af Three 81acks in Real Scale. The specimens to control the mortar strength were taken during prisms modeling period, and they were tested later, to determine its compression strength.

5 Figure 3. Prism af Three 81acks in Real Scale. The specimens to control the mortar strength were taken during prisms modeling period, and they were tested later, to determine its compression strength. Mortar bedding thickness was assumed as 1 O,Omm in the real scale prisms and it was assumed 2,5mm in the (1:4) scale. 4. TESTS PROCEEDINGS The tests were done in hydraulic presses. When testing the (1 :4) scale blocks, it was used a 200kN maximum capacity press, even using the 10kN scale, figure 4 gives a general view of this testo While testing the (1 :1) scale blocks, it was used a 5000kN maximum capacity press, even using the 1000kN scale, figure 5 gives a general view of this test. The tested blocks were capped with sulfur, always following the test methods extolled by NBR During the tests of the real scale blocks the load velocity was 203,ON/s and for the small-scale blocks this velocity was 12,7N/s. It is worth to comment that NBR 7186 determinations are the same for the prisms load cases, including the load velocity. 5. FINAL OBTAINED RESUlTS The obtained results of the blocks and prisms testing, as well the mortar tests, are showed as tables and figures, believing the authors, that it is the best way to visualize. 389

6 Figure 4. Compression Strength Test in the Small-Scale Block. Figure 5. Compression Strength Test in Real Scale Block. 6. RESUl TS ANAL YSIS AND CONCLUSIONS The blocks fabrication process began with a mixture lower than 1 30g. Using this amount of mass, it was verified that the blocks were breaking during the shape hand-removing process, making this value the minimum allowed. It was also verified that for values over 140g, it was not possible, either because of the shape hand-removing process or the manual pressing. According to those limits the fabrication process was predefined with the values 130g, 132g, 135g e 137g. 390

7 Table 7. (7:4) blocks compression strength. Type Rupture Load (kn) Strength (MPa) Medium Strength (Mpa) Final Mass (g) BL ,20 1,26 1, ,56 1,80 3,38 1,33 3,80 1,50 5,08 2,00 BL ,60 1,81 1, ,42 2,14 4,34 1)1 4,26 1,68 5,38 2,12 4,62 1,82 BL ,94 1,55 2, )0 2,25 5,10 2,01 6,38 2,51 BL ,52 2,18 2, ,92 2)3 5,52 2,18 7,48 2,95 5,30 2,09 5,86 2,31 8,62 3,40 Graph 7. Medium Compression 5trength Varying the Compacity Degree ;- ~ 7 /! J:. 6 / ~ 5 /' C!li ~ 4 /" 1--Curva equaeionada r- ~ 2,55 ~ I o Dados obtidos ~8 ~ 2 ~ "y~ 208, Final Dry Mass (g) / / About the obtained test data, it was verified, as showing on graphic 1, the compression strength increase was related with the mass increase, or better writing, related with the compacity degree increase, as it was expected. It is still believed that when the (1 :4) small-scale blocks have the same compacity degree of the real scale blocks, those will probably presents compression strengths values bet- 397

8 Table 2. Block, Prisms and Mortar Compressive 5treng th. Rupture Compressive Average Scale Type Load (kn) Strength compressive (Mpa) Strength (MPa) 1:1 Slock 627,00 15,44 13,66 610,00 15,02 677,00 16,67 532,00 13,10 612,00 15,07 408,00 10,05 417,00 10,27 Prism 336,00 8,28 8, ,00 7,54 370,00 9, ,00 7,64 Mortar 6,00 3,06 3,76 5,68 2, 89 10,44 5,32 1:4 Slock 5,52 2, 18 2,55 6,92 2,73 5,S2 2,18 7,48 2,95 5,86 2,3 1 5,30 2,09 8,62 3,40 Prism 7,34 2,89 2,40 6,44 2,54 6,20 2, 44 5,80 2,29 4, 66 1,84 Mortar 8,80 4,48 3,92 6,50 3,31 7,80 3,97 ween 9 to 11 MPa, this will occur only if the graphic 1 have a exponential projection. The real scale blocks compression strength presented a medium va lue of 1 3,66 MPa, this value, however, is higher than the ones found in the small-scale blocks tests. Even so, it is an obligation to point out that the small-scale blocks were tested when t hey were only seven days old, while the real scale blocks were much older than the small-scal e ones. This should be t he determinant factor on the verified difference, besi des t hat, the compacity degree has influenced too. The prisms presented lower values than the units (blocks), which were expected, the efficiency ratio (PRISM STRENGTH / UNIT STRENGTH) was 94% in the smallscale blocks, and for the real scale on es this value reaches 60% only. 392

9 Figure 6. Standard Rupture af Small-Scale Black. Figure 7. Standard Rupture af Small-Scale Prisms. As showing in the figures 7 and 8, the rupture characteristics of the prisms, in both scales, was similar, this fact can strongly indicate the possibility of representing the structural masonry behavior using small-scale models developed at research laboratories. New tests programs will be done, and because of this initial investigation, the necessity of improve better the fabrication process of the small-scale blocks became indispensable, making this happen, it will be possible to produce the small-scale blocks with the same compacity degree of the others in real scale. Once finished this stage, it is intended to make comparative tests with blocks, prisms and walls, studying then, the compression strengths, the strain and ruptures forms. 393

10 Figure 8. Standard Rupture af Real Scale Prisms. 7. ACKNOWlEDGEMENTS: Special acknowledgements to Concretic Concrete Blocks Factory for the blocks and ali the required information they gave to this research, and to CESP - Energy Generation Company of São Paulo State, for helping with the tests procedures and for lend the hydraulic presses used. 8. REFERENCES ABBOUD, B. E. et alli. Small-scale modeling of concrete block masonry structures. AC/ Structural journal, Detroit, v.87, n.2, p , mar/apr CAMACHO, J. S. Contribuição ao estudo de modelos físicos reduzidos de alvenaria estrutural cerâmica. São Paulo: Escola Politécnica da Universidade de São Paulo, EGERMAN, R.; COOK, D. A; ANZANI, A An investigation into the behavior of scale model brick walls. In: INTERNATIONAL BRICK/BLOCK MASONRY CONFERENCE, 9, 1991, Berlin. Proceedings (s.n.t.) p HENDRY, A W. & MURTHY, C. K. Comparative tests on one-sixth scale model brickwork piers and walls. British Ceramic Society Proceedings, Stoke-on-Trent, na, p.21-32, jul

11 HARRIS, H. G. &: BEClCA, I. J. Direct small scole modeling of concrete masonry. New York: American Society of Civil Engineering, p. (Laboratory Report, m77-1). HAMID, A A; ABBOUD, B. E.; HARRIS, H. G. Direct modeling of concrete block masonry under axial compression. Masonry: research, application and problems, STP-871, ASTM, Philadelphia, p , NBR 7186 Bloco vazado de concreto simples para alvenaria com função estrutural. São Paulo, Associação Brasileira de Normas Técnicas, 1982.

THE INFLUENCE OF MORTAR BEDDING ON THE COMPRESSIVE STRENGTH OF CONCRETE BLOCK MASONRY STRUCTURES

THE INFLUENCE OF MORTAR BEDDING ON THE COMPRESSIVE STRENGTH OF CONCRETE BLOCK MASONRY STRUCTURES Izquierdo, Orieta Soto 1 ; Corrêa, Márcio Roberto Silva 2 ; Soto, Indara Izquierdo 3 1 PhD Student, EESC