A Study on Plastic Cell Filled Concrete Block Pavement for Low Volume Rural Roads
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A systematic full scale experimental study on the structural performance of Plastic Cell filled Concrete Block Pavement (PCCBP) for various cell thicknesses subjected to live traffic conditions is presented in this research work. Five test sections of different thicknesses viz., 50 mm, 80 mm, 100 mm, 120 mm and 150 mm, of PCCBP over 100 mm thick water bound macadam (WBM) sub-base layer has been constructed at the approach road towards Indian Institute of Technology Guwahati (IIT Guwahati), India, from National Highway 31 (NH 31). In addition, to check the feasibility of PCCBP overlay to strengthen the existing old bituminous pavement, 50 mm thick PCCBP overlay test section was also constructed. Further, in order to optimize the cost of pavement construction, an attempt has been made to use waste stone dust (byproduct of aggregates crushing) in place of the traditional river sand. Custom fabricated Falling Weight Deflectometer (FWD) was used to evaluate the PCCBP by measuring the surface deflections at specified radial distance from the load center. In this work, Genetic Algorithm (GA) based backcalculation program (Reddy et. al., 2002) was used for backcalculating the layer moduli of the PCCBP test sections using pavement surface deflection data. For the thicknesses tested, elastic layer modulus of PCCBP (~1995 MPa for 50 mm thick) has been seen to increase linearly with increasing thickness (~90% increase in elastic modulus was observed for 200% increase in thickness). To evaluate the structural performance of PCCBP, surface deflections data using FWD were collected at regular intervals of 0 passes, 38,000 passes (~6 months) and 62,000 passes (~11 months). It has been observed that for the initial 38,000 ESAL passes the degradation in layer modulus of PCCBP is of the range ~3-20%, however there appears to be a stabilization after 38,000 ESAL passes with the degradation dropping to ~1-7% (from 38,000 to 62,000 ESAL passes). It has also been seen that there is a significant improvement (~230% increase) in elastic layer modulus when PCCBP is used as overlay as compared to that of bituminous overlay. Efforts have been made to assess pavement distresses of PCCBP test section using distress guidelines developed by Interlocking Concrete Pavement Institute (ICPI, 2007) based on Pavement Condition Index (PCI) for similar distress types observed. The distress type and severity level of each test section was recorded and PCI value of each section was calculated using the deduct curves given in the distress manual. From the PCI value, the rating of the test section was found to be in the range from Fair to Very Good condition even after a load repetition of 62,000 ESAL passes. Specific distresses observed for PCCBP are also reported. From the feasibility study of PCCBP overlay, it was observed that the performance is Excellent even after 62,000 ESAL passes. Economic evaluation of PCCBP vis-a-vis conventional flexible and rigid pavements was also carried out. In the absence of design guidelines for PCCBP, rutting criteria as per IRC (2001) was adopted to design the PCCBP pavement. Conventional flexible and rigid pavements were design as per IRC (2007) and IRC (2004). The construction and maintenance cost were estimated based on Government of Assam schedule rate 2007-08 (PWD, 2007) and guidelines for the estimation of the maintenance cost for construction of the rural roads......
Supervisor: T. Lyngdoh AND K. Darunkumar