INDIAN INSTITUTE OF TECHNOLOGY GUWAHATI DEPARTMENT OF CIVIL ENGINEERING
Economic evaluation of PCCBP versus conventional flexible and rigid pavements was also performed. Economic evaluation (considering construction cost and maintenance cost for 5 years) shows that the cost of flexible and rigid pavements is higher by ~43% and ~141% respectively compared to that of PCCBP.
Introduction
General
From the available literature review, no attempt has been made to study the effect of PCCBP thickness on the structural performance of the pavement. The present work aims to conduct a systematic field study on the structural performance of PCCBP for different cell thicknesses subjected to live traffic (low volume) conditions.
Objectives
In addition, attempts have also been made to conduct emergency surveys of PCCBP test sections based on the pavement condition index (PCI) method. Economic evaluation of PCCBP over conventional flexible and concrete pavements was also carried out to know the benefits of constructing rural roads with PCCBP over the conventional flexible and rigid pavements.
Thesis organization
PCCBP
Literature Review
- Introduction
- Low Volume Rural Roads – definition
- Plastic Cell Filled Concrete Block Pavement
- Review of previous work carried out in South Africa
- Review of previous work carried out in India
- PCCBP as Overlay Construction
- Stone dust as replacement of sand in concrete
- Distresses in PCCBP
- Summary of literature review
It was concluded that while a 100 mm thick PCCBP layer may be structurally suitable for ultra-heavy loading conditions, a 150 mm layer would be preferable. The moduli values of the surface layer were found to be in the range MPa, with the highest associated with a 100 mm thick PCCBP over a 100 mm thick soil cement (10% cement by dry soil weight).
Structural Behaviour of PCCBP
Introduction
Materials used for the construction of PCCBP .1 Low Density Polyethylene (LDPE) Plastic Cell
- Cement
- Stone dust
- Coarse Aggregate
- Soil
The soil used for the sub-grade fill for the test pavement was brought from a nearby hillside excavation. The laboratory soaked and undamped California bearing ratio (CBR) values of the backfill soil were found to be 5% and 7%, respectively (IS.
Laboratory investigations
It has been observed that for the grouting technique, mortar with w/c ratio = 0.4 was too dry to grout into the voids between the coarse aggregates, while a w/c ratio of 0.6 gave high workability. Crushed nominal single size stone aggregates 22.4 mm were filled into the pockets of the plastic cells and mortar with c:sd ratio = 1:1.25 was vibrated using a plate vibrator into the voids between the coarse aggregates.
Structural evaluation of PCCBP test sections .1 Test section
- Excavation of the existing pavement
- Preparation of the sub-grade soil
- Water Bound Macadam (WBM) Course
- Laying and concreting of the plastic cells .1 PCCBP – new construction
- Curing of the PCCBP test section
The concreting of the overlap section is done while the Gellix coating is still adhesive (Figure 3.13). The wheel load recorded by the portable load pad was then doubled to estimate the axle load of the vehicles.
Structural evaluation of PCCBP test section
- Falling Weight Deflectometer (FWD)
- Backcalculation of layer modulus using BACKGA
- Deflection computation using KENLAYER
- Deflection computation using ABAQUS
Validations of the BACKGA results (layer moduli) have been performed using the finite element (FE) software ABAQUS (2009) (linear-elastic-static analyses). The layer moduli obtained through BACKGA have been used as input to the FE analyses.
Results and discussions
- Thickness effect of PCCBP test pavement .1 Surface deflections
- Layer elastic modulus
- Validation with FE and KENLAYER
- Comparison with other similar studies
- PCCBP as overlay construction .1 Surface deflections
- Layer elastic modulus
- Performance of PCCBP with load repetitions .1 Different thickness of PCCBP test section
- PCCBP as overlay construction
The Poisson ratios considered for PCCBP, subbase and subgrade layers in the analysis are given in Table 3.7. From Figure 3.31 it can be seen that subgrade moduli lie within the range 70 - 100 MPa for the thicknesses considered. From Figure 3.34 it can be seen that subgrade moduli lie in the range 63 – 48 MPa for the thicknesses considered.
This may be due to the greater thickness of the sub-base (445mm) compared to 100mm for the new build. The figures show the variation of elastic layer moduli of PCCBP, sub-base and sub-grade layers respectively for 3 (three) different load repetitions. It can be seen from Figure 3.39 that the elastic modulus of the sub-base layer also decreased with increasing traffic passes, but with a relatively steeper gradient at the initial 38000 ESAL passes.
From Figure 3.41 it can be observed that the reduction of modules for PCCBP and bituminous overlays are 0.9% and 3%.
Conclusions
The elastic modulus of the subgrade was found to be in the range of 100 – 70 MPa, with marginal variation with thickness.
Distress Study of PCCBP
Introduction
External indicators of pavement deterioration caused by loading, environmental factors, construction deficiencies, or a combination thereof. It is a numerical rating of the pavement condition ranging from 0 to 100 with 0 being the worst possible condition and 100 being the best possible condition. The basic flow diagram for developing the PCI values for a section of pavement is shown in Figure 4.1.
Data sheets recording at least the following information: date, location, section, sampling unit size, block number and size, emergency types, severity levels, quantities and names of surveyors (Appendix E).
Distress Evaluation
- New PCCBP test section
- Distress types similar to Interlocking concrete block pavement distress manual (ICPI, 2007)
- Distresses specific to PCCBP
- Overlay PCCBP test section
The difficulty level of the track can be defined by the maximum track depth in mm. Such deformation in the plane of the cell wall (high density polyethylene cell wall) of the order of 5 mm (reduction in cell height) was also reported by Visser (1999). Description: The length of the block sides can be increased due to the opening of the seal in the plastic cell formwork.
Identification: Normally opening cells are identified based on the size of the sides of the block. Roughness level: The roughness level can be expressed as the size of the sides of the block inside. Visual observation shows that unlike the 50 mm PCCBP test sections placed on the 100 mm thick WBM course, there is no scraping of the edges of the blocks in the overlap section.
The improved performance of the PCCBP overlay can be attributed to the well-compacted underlayers.
Evaluation of PCI
- Measuring Techniques
- Different thickness of PCCBP
- PCCBP overlay
The assessment of the overall condition of the section is assessed by the PCI assessment chart given in Figure 4.1. Visual observation shows that there are no discernible disturbances observed in the PCCBP overlay test section.
Discussions
Conclusions
Economic Evaluation
- Introduction
- Design of Different Types of Pavement .1 Design parameters
- Design of rigid pavement
- Design of PCCBP
- Cost comparison
- Construction and maintenance cost
- Cost estimation
- Discussions
- Conclusions
From the pavement design map, Figure 4 of IRC (2007), the thicknesses of the pavement layers were obtained as a 150 mm thick granular base layer (CBR > mm thick WBM layer and 20 mm thick bituminous premix carpet as a top layer). In the present study, a design analysis was carried out for 100 mm thick PCCBP laid over a sub-layer of 100 mm thick WBM layer. In the absence of guidelines on maintenance charges for PCCBP and taking into account the good performance of cellular concrete pavements 100 mm thick, more than 100 mm compacted moorum subbase layer constructed for a village road that has withstood 5 (five) heavy monsoons without any maintenance (Roy et. al., 2009), is considered the same as that for concrete pavement.
The cost calculation for economic evaluation of PCCBP versus conventional flexible and rigid pavement is given below. Cost of construction for 100 mm thick cement concrete (using stone dust) = Rs 384/m2 Hence total cost of construction for PCCBP pavement = Rs 639/m2 The routine maintenance cost for 5 years = Rs 16/m2 Renewal / major repair cost of PCCBP pavement after 5 years = Rs 26/m2. The cost comparison of PCCBP with conventional flexible and concrete pavement considering both construction and maintenance costs is shown in Table 5.2.
The total costs including construction and maintenance costs for 5 years of flexible and rigid pavements are higher by 43% and 141%, respectively, compared to PCCBP.
Summary and Conclusions
A thin PCCBP of approximately 50 mm over a thin sub-layer can result in sufficiently high elastic moduli (>1900 MPa) of PCCBP to be used for rural roads. The elastic modulus of PCCBP increases with increasing thickness, approximately in a linear manner for the thicknesses tested; a 90% increase in elastic modulus was observed with a 200% increase in thickness. It has been observed that for the first 38,000 ESAL passes, the low modulus degradation of PCCBP is in the range of ~3–20%. However, there appears to be a stabilization after 38,000 passes, with degradation dropping to ~1-7%.
The PCCBP overlay showed a significant improvement (~230% increase) in the elastic modulus of the layer compared to that of a bituminous overlay, suggesting that PCCBP may be a good alternative for strengthening the existing bituminous pavement. Emergency evaluation of PCCBP test sections (after 62,000 ESAL passes) based on the ICPI emergency manual showed that PCCBP of 50 mm thickness can be assessed as. The construction and maintenance costs (over 5 years) of flexible and rigid pavements are estimated to be ~43% and ~141% higher, respectively, compared to PCCBP.
Therefore, PCCBP with waste stone dust as a replacement for the traditional sand for both concrete and WBM can be an economical option for rural roads.
Recommendations for future work
Structural Behavior of Concrete Block Pavements I: Sand in Bed and Joints, Journal of Transportation Engineering, March/April. Structural Behavior of Concrete Block Pavements II: Sand in Bed and Joints, Journal of Transportation Engineering, March/April. Artificial Neural Network - A Genetic Algorithm Based Model for Back Calculation of Pavement Layer Moduli, International Journal of Pavement Engineering, 7 (3), September, 221-230.
Buigsame-rigiede plaveiselmateriaal - 'n volhoubare oplossing vir dorpspaaie, Journal of the Indian Roads Congress, New Delhi. Structural Evaluation of Concrete Filled Cell Pavement, International Journal of Pavement Engineering and Asphalt Technology, U.K., 7 (1), pp. A Cast In-situ Block Pavement for Labour-Enhanced Construction, Concrete Beton, Journal of the Concrete Society of South Africa , (71), 1-8.
Response of flexible Portland cement concrete pavements under ultra-heavy loading, Beton Beton, Journal of the Concrete Society of South Africa.
Appendix A
APPENDIX-B
Appendix C
APPENDIX D
Appendix E
PCCBP CONDITION SURVEY DATA SHEET FOR SAMPLE UNIT
DISTRESS NUMBER AND TYPE
ROAD: Plastic Cell Filled Concrete Block Paving Test Section DATE: 24 November‟2010 SECTION: 120 mm PCCBP SAMPLE UNIT: 1 (one). ROAD: Plastic cell filled concrete block pavement test section DATE: 24 November‟2010 SECTION: 100 mm PCCBP SAMPLE UNIT: 1 (one). ROAD: Plastic Cell Filled Concrete Block Paving Test Section DATE: 24 November‟2010 SECTION: 80 mm PCCBP SAMPLE UNIT: 1 (one).
ROAD: Test section of concrete blocks filled with plastic cells DATE: 24 November 2010 SECTION: 50 mm PCCBP SAMPLE UNIT: 1 (one).
Appendix F
Appendix G
INPUT FILENAME -F:\ pccbp100rutshell.DAT NUMBER OF PROBLEMS TO BE SOLVED = 1 TITLE -PCCBP 100 thick.
Appendix H
- Cost of plastic
- Man-days required
- Paddle Sealing Machine
- Cost of Concreting
Application and application of an emulsion bonding layer using an emulsion pressure distributor at a rate of 0.20 kg/m2 on the prepared bituminous/granular surface, cleaned with a mechanical broom. Supplying, laying and rolling of open premix pavements of 20mm thickness composed of 13.2mm to 5.6mm aggregate either using penetration bitumen (60/70) or bitumen emulsion to the required line, quality and level to serve as a wearing layer on a previously prepared base, including mixing in a suitable. Supplying, laying, spreading and compacting of stone aggregates of specific dimensions according to the waterborne macadam specification, including spreading in uniform thickness, manual packing, rolling with an 8-10 ton vibratory roller in stages to the correct quality and camber, laying and blowing out of required types of screens/binding material to fill, water and compact the interstices of coarse aggregates to the required density (with an initial lead of 5.0 km).
Extract of Plastic Cell Filled Concrete Block Pavement (PCCBP) cost based on current (year 2010) market rate in Assam state. Cost of Electrically Driven Shovel Sealing Machine = Rs 10000.00 Hence total cost of preparing plastic cellular formwork for 3750Sqm area,.
