STRUCTURAL BEHAVIOUR OF CONCRETE BLOCK PAVEMENT: A REVIEW

INDIAN INSTITUTE OF TECHNOLOGY ROORKEE TRANSPORTATION INFRASTRUCTURE PROJECTS : CONCEPTION TO EXECUTION (TIPCE) - 2019 A presentation on STRUCTURAL BEHAVIOUR OF CONCRETE BLOCK PAVEMENT: A REVIEW Sumit Nandi Research Scholar Civil Engineering Department (CED) Indian Institute of Technology Roorkee Dr. G. D. Ransinchung R. N. Associate Professor Civil Engineering Department (CED) Indian Institute of Technology Roorkee

2 CONTENTS INTRODUCTION TO PAVER BLOCKS ADVANTAGES OF CONCRETE BLOCK PAVEMENT HISTORY OF PAVER BLOCKS USAGE STATISTICS APPLICATIONS OF PAVER BLOCKS FEATURES OF PAVER BLOCKS JOINTING AND BEDDING SAND EDGE RESTRAINT INTERLOCK MECHANISM LOAD DEFLECTION BEHAVIOR LOAD REPEATATION JOINT FILLING AND THICKNESS VARIATION CONCLUSIONS REFERENCES

3 PAVER BLOCKS: PART OF BLOCK PAVEMENT Paver blocks form a part of the segmental paving system. The individual paving units are bedded and jointed in the sand rather than the age-old system of continuous paving (Panda and Ghosh 2002 b). Substructure beneath the bedding sand is similar to that of a conventional flexible pavement. Figure : Components of block pavement (Panda and Ghosh 2002 a) The major structural components of the concrete block pavements are: (1) Block Pavers (2) Bedding and Jointing Sands (3) Edge Restraints (4) Base-course and Sub-base (5) Sub-grade

4 ADVANTAGES OF CONCRETE BLOCK PAVEMENT FREEZE-THAW RESISTANCE ACCESS TO UTILITIES EASY MAINTENANCE AND REPAIR LOWER MAINTENANCE COSTS CRACKING PHENOMENON FREE CONCRETE BLOCK PAVEMENT (CBP) RESTRICT THE SPEED OF VEHICLES AESTHETICALLY PLEASING UNAFFECTED BY SPILLAGE OF OILs WITHSTANDING DEICING SALTS

5 PAVER BLOCKS: HISTORY 4000 BC First record of stone paving in Assyria. 2000 BC Flagstones were being used to pave village streets. Road-making using brick common in Mesopotamia. 300 BC Clay brick paving in use in India. 1950 AD Post World War II. Shortage of coal. Concrete pavers were first introduced in The Netherlands as an alternative to the kiln-fired brick paving units then in use. Spread quickly to Germany, Austria, Belgium, France, and England. 1970s AD Concrete pavers came to the United States.

6 PAVER BLOCKS: HISTORY BLOCK SHAPE EVOLUTION (IRC:SP:63 2004) INITIAL COST AND SIZE SIMILAR TO PAVING BRICK DENTATED TO PROVIDE KEY WITH ADJOINING UNITS, RETAINING ESSENTIALLY BRICK DIMENSIONS NEW SHAPE FOR BETTER PERFORMANCE UNDER TRAFFIC AND PERMITTING MECHANICAL LAYING OF BLOCKS 'X' SHAPED BLOCK FOR BETTER INTERLOCK AND FASTER MECHANISED PAVING

7 PAVER BLOCKS: USAGE STATISTICS Figure : Use of pavers worldwide in millions of square metres per annum (CMA 2009) Figure : Growth in concrete block paving in South Africa (CMA 2009)

8 PAVER BLOCKS: APPLICATIONS Figure : Paver Blocks at Intersections Figure : Paver Blocks at Pedestrian Crossings Figure : Paver Blocks at Sidewalks Figure : Paver Blocks at Toll Plazas Figure : Paver Blocks at Main Roads Figure : Paver Blocks at Car Parks

9 PAVER BLOCKS: APPLICATIONS Figure : Paver Blocks at Factories and Warehouses Figure : Paver Blocks at Container Depots Figure : Paver Blocks at Embankments Figure : Paver Blocks in Stormwater channels Figure : Paver Blocks at Roof Deck Figure : Paver Blocks used to create picture

10 PAVER BLOCKS: FEATURES (CATEGORIES) Three categories of paver shape have been recognized (Morrish 1980). Category A comprises dentate blocks which key into each other on all four faces. Category B comprises dentated blocks which key into one another on two faces only. Category C comprises non-dentated blocks which do not key together geometrically. Figure : Different Categories of Blocks (IRC:SP:63 2004)

11 PAVER BLOCKS: FEATURES (TEST SETUP) Figure : Schematic Test-Setup for testing of Paver Blocks (Panda and Ghosh 2002 a) Figure : Highway accelerated loading instrument (Ling et al. 2009)

12 PAVER BLOCKS: FEATURES (BLOCK SHAPES) Higher vertical surface area results in large load spreading ability. Some early plate load studies (Knapton 1976; Clark 1978) contradicted this finding. Later accelerated trafficking studies (Shackel 1980) and plate load studies (Shackel et al. 1993) established that shaped (dentated) blocks exhibited smaller deformation than rectangular blocks of a similar thickness installed in the same laying pattern under the same applied load. Figure : Summary of paver block shapes available (CMA 2009)

13 PAVER BLOCKS: FEATURES (BLOCK SIZE) Smaller size blocks have more numbers of joint per unit area than a larger block (Panda and Ghosh 2002 a). The tendency of rotation and translation of the smaller block is higher than a larger block. This conclusion is inconsistent with earlier findings by Shackel (1980). Figure : Effect of block sizes on behavior of block pavement (Panda and Ghosh 2002 b)

14 PAVER BLOCKS: FEATURES (BLOCK THICKNESS) As the block thickness increases the elastic deformation of the pavement reduces. Knapton (1976) found pavement performance was essentially independent of block thickness, whereas Clark (1978) reported a small improvement in pavement performance with an increase in block thickness. Shackel (1980), Miura et al. (1984) and Shackel et al. (1993) claimed that an increase in block thickness reduced elastic deflection and the stress transmitted to the subbase. Compounded effect of higher frictional resistance and thrusting action between adjacent block at the hinging point is more effective in case of thicker blocks (Panda and Ghosh 2002 a). Figure : Rut depth as a function of block and base thickness (Shackel 1980)

15 PAVER BLOCKS: FEATURES (BLOCK STRENGTH) Figure : Effect of block strengths on the behavior of block pavement (Panda and Ghosh 2002 b) The blocks of the in-service CBP undergo compressive stresses due to traffic loading. The bending stresses develop in blocks are negligible because of block size and its aspect ratio. Concrete blocks behave as rigid bodies in CBP. Loads transfer to the adjacent blocks is by virtue of its geometrical characteristics rather than the strength of blocks. Shackel (1980), and Panda and Ghosh (2002 b) concluded that the load associated performance of block pavements was essentially independent of the compressive strength of the blocks. The effect of block strength on the load-deflection behaviour of block pavement is shown in the adjacent figure.

16 PAVER BLOCKS: FEATURES (LAYING PATTERN) The most commonly used patterns are herringbone, stretcher or running and basketweave or parquet bonds. Knapton (1976) found that laying pattern did not significantly affect the static load-spreading capacity of the pavement. Figure : Three basic laying patterns for block paving (CMA 2009) Accelerated trafficking tests (Shackel 1980) have been used to compare the performance of these patterns. From plate load studies, Miura et al. (1984) and Shackel et al. (1993) have reported that, for a given shape and thickness, blocks laid in a herringbone bond exhibited higher performance than blocks laid in a stretcher bond. The Herringbone pattern can have three orientations relative to the direction of traffic. It should be laid at 45⁰ to the traffic to resist the traffic shear stresses. Figure : Effect of laying pattern of blocks on behavior of block pavement (Panda and Ghosh 2002 b)

17 PAVER BLOCKS: FEATURES (BEDDING SAND) Table : Thickness of Bedding Sand Table : Bedding Sand grading Authors Specification (Thickness) Authors Specification (Grading) Eisenmann and Leykuf (1988), Lilley and Dowson (1988), Compacted thickness of 50 mm Lilley and Dowson (1988) 5, 15 and 50 percent passing (maximum) 75, 150, and 300 mm sieves respectively. Hurmann (1997) Nominal size of 5 mm (European practice) (maximum), 10% or less Rada et al. (1990) (United States), Shackel et al. (1993) (Australia) Simmons (1979) Compacted thicknesses of 20-30 mm Compacted depth of 40 mm minimum Sharp and Simmons (1980) coarser than the 4.75 mm sieve. Grains should not be single sized and/or spherical shaped. Less than 3% clay/silt content. Particle size of 9.52 mm Mavin (1980) Compacted depth of 30 ± 10 mm, 10 mm tolerance to be kept Livneh et al. (1988) maximum. Not more than 10% should pass the 75 on the subbase micron sieve.

18 PAVER BLOCKS: FEATURES (JOINTING SAND) Table : Joint width Table : Grading of Jointing Sand Authors Specification (Joint Width) Authors Specification (Grading) Shackel et al. (1993), Hurmann (1997) 2-4 mm uniform, narrow and filled joints to be provided. Lilley (1981), Hurman (1997) Similar to that of bedding course. Particle size of 1.18 mm Knapton and O Grady (1983) Lilley (1994) 0.5-5 mm joints to be provided for better pavement performance Below 5 mm. Excess width decreases the structural capability of the wearing Shackel (1980) Knapton and O Grady (1983) maximum and less than 20% finer than the 75 micron sieve. It should be finer. Finer than 2.36 mm sieve. As per British Standards, Zone 2 sand found to be most effective. Particle size of 1.2 mm course. Livneh et al. (1988) maximum and 10% finer than 75 micron.

19 PAVER BLOCKS: FEATURES (EDGE RESTRAINT) Edge restraints are a key part of CBP. Edge restraints resist lateral movement, prevent rotation of the pavers under load and restrict loss of bedding sand material at the boundaries. Edge restraints are designed to remain stationary while receiving impacts during installation, from traffic loads and freeze-thaw cycles. Edge restraints should be laid at all boundaries of the paved area or between the joints of the edge restraints. Figure : Edge Restraints (IRC:SP:63 2004) Figure : Pavement deflections with and without edge restraint (Panda and Ghosh 2002 b)

PAVER BLOCKS: FEATURES (INTERLOCK) Interlock has been defined as the inability of an individual paver to move independently of its neighbours. Figure : Achievement of vertical interlock (Knapton and Barber 1980 ) It has been categorized as having three components: horizontal, rotational, and vertical. Interlock is of major importance for the prevention of movement of pavers horizontally when trafficked (Knapton and Barber 1979). Figure : Achievement of rotational interlock (Knapton and Barber 1980) 20

PAVER BLOCKS: FEATURES (INTERLOCK MECHANISM) 21 Figure : Effects of rotation on the wedging action of pavers (Shackel and Lim 2003) Figure : Effects of paver rotation on pavers laid in herringbone bond (Shackel and Lim 2003)

22 CBP: LOAD DEFLECTION BEHAVIOR The load-deflection behavior is irrespective of block shape, size, strength, thickness, and laying pattern. It is seen that the pavement deflection increased in a nonlinear manner with increasing load. An interesting observation is that the rate of deflection decreases with increasing load (Panda and Ghosh 2002 a). The results obtained are similar to that established in earlier plate load tests by Knapton (1976), Clark (1978), and Miura et al. (1984). Figure : Load spreading mechanism (Panda and Ghosh 2002 a)

23 CBP: LOAD REPEATATION Panda and Ghosh (2002 b) reported that the loaddeflection response is nonlinear. Moreover, initially, the repeated loading and unloading results into deflection, which is not fully recovered. Figure : Effects of cycling 51 KN load on paver blocks laid in a herringbone pattern (Panda and Ghosh 2002 b) Permanent residual deformations develop due to load repetition. Block pavements stiffen progressively with an increase in the number of load repetitions During loading, additional compaction of sand under blocks occurs, and some part of the energy is lost in that way. As a result, the recovery is not full. Figure : Effects of load repetition (Panda and Ghosh 2002 b)

24 CBP: JOINT FILLING AND THICKNESS VARIATION Figure : Need for complete filling of joints (IRC:SP:63 2004) Figure : Effect of thickness variations in paving blocks (IRC:SP:63 2004)

25 CONCLUSIONS CBP is made up of a rigid material but the construction and behaviour have a resemblance to that of a conventional asphalt pavement. Deflection of CBPs is influenced by the width of joint, jointing sand and bedding sand quality, bedding sand thickness, block shape, block size, block thickness, and number of load repetitions. The vertical surface area of the block greatly affects the load transfer. Shaped blocks perform better compared to square or rectangular (undented) ones of similar thickness laid in same laying pattern. Deflection of CBPs can be reduced by the use of larger blocks. The load associated performance of CBP is influenced by the pattern of laying with herringbone bond giving the best performance. On the contrary, the block compressive strength does not have any effect on the performance of thecbp. The joints between the paver blocks should be uniform, narrow and properly filled for optimum load spreading by friction, and to reduce deflection an effective edge restraint should be provided. The jointing sand should contain lesser fines that is, particles passing 75-micron sieve for smaller joint widths and the maximum size should be below the joint width provided.

26 CONCLUSIONS The bedding course acts as a cushion and should consist of course-grained sand providing a greater resistance to shearing. A loose thickness of 50 mm can be provided. The response of CBP to load repetition is non-linear, so permanent residual deformations occur. With the number of load repetitions increased, there is a progressive stiffening of the block pavements. So block pavements gradually attain its strength. The early deformation occurring in the very early life of the pavement and well before final lock-up can be arrested by recompaction of the pavement prior to locking up (equilibrium). Functioning of CBPs largely depends on the unique interlocking mechanism of the paver blocks involving the wedging action.

27 REFERENCES 1. Clark, A.J., (1978). Block paving-research and development. Concrete, 12(7). 2. CMA (2009). Concrete Block Paving Introduction. Concrete Manufacturers Association, Midrand, South Africa. 3. Eisenmann, J. and Leykauf, G., (1988). Design of concrete block pavement in FRG. In Proc., 3rd Int. Conf. on Concrete Block Paving, Pavitalia, Rome, pp.149 155. 4. Huurman, M., (1997). Permanent deformation in concrete block pavements. PhD thesis, Delft Univ. of Technology, Delft, The Netherlands. 5. IS: 15658, (2006). Precast Concrete Blocks for Paving-Specifications. Indian Standards, New Delhi, India. 6. Knapton, J., (1976). The design of concrete block roads. Technical Rep. 42.515, Cement and Concrete Association, Wexham Springs, U.K. 7. Knapton, J. and O Grady, M., (1983). Structural behavior of concrete block paving. J. Concrete Soc., pp.17 18. 8. Lilley, A., (1994). Size and block shape - Do they Matter. Concrete plant and production, 12, pp.123-123. 9. Lilley, A.A. and Dowson, A.J., (1988, May). Laying course sand for concrete block paving. In Proc., 3rd Int. Conf. on Concrete Block Paving, Pavitalia, Rome, (pp. 457-462). 10. Livneh, M., Ishai, I. and Nesichi, S., (1988). Development of a pavement design methodology for concrete block pavements inisrael. In Proc., 3rd Int. Conf. on Concrete Block Paving, Pavitalia, Rome, pp.94-101. 11. Mavin, K.C., (1980). Interlocking block paving in Australian residential streets. In Proc. of 1st International Conf. on Concrete Block Paving. 12. Miura, Y., Takaura, M. and Tsuda, T., (1984). Structural design of concrete block pavements by CBR method and its evaluation. In Proc., 2nd Int. Conf. on Concrete Block Paving (pp. 152-157). Delft, The Netherlands: Delft Univ. oftechnology. 13. Panda, B.C. and Ghosh, A.K., (2002). Structural behavior of concrete block paving. II: Concrete blocks. Journal of transportation Engineering, 128(2), pp.130-135.

28 REFERENCES 14. Panda, B.C. and Ghosh, A.K., (2002). Structural behavior of concrete block paving. I: sand in bed and joints. Journal of Transportation Engineering, 128(2), pp.123-129. 15. Rada, G.R., Smith, D.R., Miller, J.S. and Witczak, M.W., (1990). Structural design of concrete block pavements. Journal of transportation engineering, 116(5), pp.615-635. 16. Shackel, B., (1979). A Design Method for Interlocking Concrete Block Pavements. In Proceedings Symposium on Precast Concrete Paving Block, Johannesburg, Concrete Society of Southern Africa. 17. Shackel, B., (1980). The performance of interlocking block pavements under accelerated trafficking. In Proc., 1st Int. Conf. on Concrete Block Paving, Newcastle-upon-Tyne, U.K., (pp. 113-120). 18. Shackel, B., O'Keeffe, W. and O'Keeffe, L., (1993). Concrete block paving tested as articulated slabs. In Fifth International Conference on Concrete Pavement Design and Rehabilitation Purdue University, School of Civil Engineering; Federal Highway Administration; Portland Cement Association; Transportation Research Board; Indiana Department of Transportation; Federal Aviation Administration; andamerican Concrete Pavement Association. (Vol. 1). 19. Shackel, B., (2003). The challenges of concrete block paving as a mature technology. Pave Africa, pp.12-15. 20. Sharp, K.G. and Simmons, M.J., (1980, August). Interlocking concrete blocks: state of the art review. In Australian Road Research Board (ARRB) Conference, 10th,1980, Sydney (Vol. 10, No. 2). 21. Simmons, M. J., (1979). Construction of interlocking concrete block pavements. Australian Road Research Rep. ARR No. 90, pp.71 80.

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