A study on the factors influencing the load transfer efficiency in concrete block pavements

Abstract

Concrete Block Pavements (CBP) are essentially precast blocks arranged in a specific pattern over a sub base and interlocked with graded bedding and jointing sand. The block size and shape, joint gap and joint filling sand size and laying pattern influence the effectiveness of the interlocking or the distribution of wheel loads. The measure of effectiveness - Load Transfer Efficiency (LTE), is the ratio of deflection between a loaded block to an adjacent unloaded block. In the present LTE study, joint filling sand of three particle sizes (1.18, 0.6 and 0.3mm), laying patterns of two types [stretcher and basket weave), concrete mixes with four variations (cement, cement with 20% fly ash, cement with steel fibre (0.5%) and cement with both fly ash and steel fibre] were tested. The test section consisted of 100 mm x 200 mm x 100mm blocks fixed over a 20 mm thick bed of 4.75 mm sand. A wet mix macadam layer over the sub grade supported the blocks. The study revealed that the joint filling with 0.6 mm sand gave a higher LTE than the other two sizes. The basket weave resulted in a higher average LTE than the stretcher bond and incorporating steel fibre and fly ash in concrete also showed an increase in the LTE.