Departmental Training of PWD Engineers on Interlocking Concrete Block Pavement/ICBP//Rajib Chattaraj

Sri Rajib Chattaraj, Hon'ble Chief Engineer, National Highway, P.W.(Roads) Directorate conducted this training programme at Pranjali Guest House ICBP is used as the wearing course of a pavement consisting of precast small size concrete blocks without reinforcements laid on the prepared subgrade and aggregate base like that of a flexible pavement. With its limitation to be used in major highways, it is very useful for cycle track, parking lots, fuel station, city roads, for paving the portion of underground utility cuts of an urban CC road for facilitating frequent maintenance and it performs well in waterlogged area too. A well constructed ICBP can provide the durability of a CC pavement at a low cost with the flexibility of a bituminous pavement and very easy maintenance procedure with a bit of compromise in riding quality and noise generation issue. The concept of Interlocking concrete block pavement(ICBP) started from the roads of Roman Empire. The modern concrete block pavement were developed in Netherlands in late 40’s as a replacement of clay brick streets. It came in USA in 70’s. In India, ICBP was started from the mid of the first decade of this millennium. Principal of Interlock Interlocking concrete block pavement is a paving system consisting of discrete, hand-sized paving units with either rectangular or dentated shapes manufactured from concrete. Either type of shape is placed in an interlocking pattern, compacted into coarse bedding sand, the joints filled with joint filling sand, and compacted again to start interlock. The paving units and bedding sand are placed over an unbound or bound aggregate layer and a prepared subgrade. Interlock is the inability of a paver to move independently from its neighbours. It is critical to the structural performance of interlocking concrete pavement. Unlike Concrete or Asphalt pavement, ICBP does not depend on monolithic continuity of their material for structural integrity. When considering design and construction, three types of interlock must be achieved: Vertical, rotational and horizontal Interlocking concrete pavements are typically constructed as flexible pavements on a compacted soil subgrade and compacted aggregate base. Concrete pavers are then placed on a thin layer of bedding sand (25 to 35 mm), compacted, joint filling sand swept into the joints, and the units compacted again. When compacted, the pavers interlock, transferring vertical loads from vehicles to surrounding pavers by shear forces through the joint sand. The sand in the joints enables applied loads to be spread in a manner similar to asphalt, reducing the stresses on the base and subgrade Important components of ICBP Paving Block — Solid un-reinforced precast cement concrete paving units used in the surface course of pavements, with minimum horizontal cross section of 50 mm from any edge in any direction, having aspect ratio not more than four, except for complementary blocks. Complementary Block — A block usually of the shape of part of a block, used for fitting into gaps remaining in a block-paved area, for complete coverage of paved surface. Important components of ICBP Bedding Sand : Bedding sands are a critical component of all sand-set segmental concrete paving systems. Especially for vehicular applications, specifiers and contractors need to consider bedding sand selection. Bedding sand provides the following functions. It beds the pavers during installation, acts as a cushion between hard base and the paver blocks. helps initialize interlock among the pavers. Bedding sand helps to keep lower part of the joint filled with sand which provides added interlocking effect. provides a structural component for the system as well as provides a layer by which the blocks can be levelled perfectly. facilitates drainage of water that infiltrates through the joints as well as acts as a barrier and does not allow propagation of cracks formed in the lower layers. Bedding Sand : Bedding sands are a critical component of all sand-set segmental concrete paving systems. Especially for vehicular applications, specifiers and contractors need to consider bedding sand selection. Bedding sand provides the following functions. It beds the pavers during installation, acts as a cushion between hard base and the paver blocks. helps initialize interlock among the pavers. Bedding sand helps to keep lower part of the joint filled with sand which provides added interlocking effect. provides a structural component for the system as well as provides a layer by which the blocks can be levelled perfectly. facilitates drainage of water that infiltrates through the joints as well as acts as a barrier and does not allow propagation of cracks formed in the lower layers. Edge Paver — A paving unit that is made with a straight, flush side, or cut straight for placement against an edge restraint. Spacer bars or spacer nibs