STRUCTURAL BEHAVIOUR OF COMPOSITE PAVEMENTS OVER LEAN CONCRETE BASE

Abstract

Throughout the world, research has been done on number of composite materials such as steel fibre reinforced concrete, ferrocement and ferrofibrocrete. By using these materials pavement thickness reduces and load carrying capacity increases. These composite pavements may be laid directly on subgrade or other base course such as WBM, lean concrete etc. Lean concrete is semi-rigid material having superior load dispersion characteristics than WBM. Beside this, it is resistant to softening action of water and is very useful in heavy rainfall areas or in black cotton soil area. When composite pavements are constructed using lean concrete as the base course,load carrying capacity and crack arrest properties are improved. Under the present investigation an attempt has been made to study the load carrying capacity and cracking behaviour of lean concrete-SFRC and lean concrete-ferro-fibrocrete composite pavement slab. The materials properties evaluated are compressive strength, flexural strength and modulus of elasticity. The size of lean concrete-SFRC composite slab was taken as 1.8 m x 1.8 m x 0.14 m composed of 40 rnm SFRC (1% fibre content by volume of concrete) over 100 mm lean concrete base course. The lean-ferro-fibrocrete slab was 1.8 m x 1.8 m x 0.125 m composed of 25 mm ferro-fibrocrete (0.5% steel fibre and 0.5% wire mesh reinforcement by volume of mortar) over 100 mm lean concrete base course. The investigation shows that the compressive strength of lean concrete-SFRC and lean concrete-ferro-fibrocrete composite increases to 17 N/mm2 and 20.62 N/mm2 as compared to 8.28 N/mm2 of lean concrete. Similarly, flexural strength and modulus of elasticity of the composites increases as compared to lean concrete. Load carrying capacity of lean concrete-SFRC and lean concrete-ferro-fibrocrete was 80 kN and 110 kN under corner loading condition. The cost of lean concrete-ferro-fibrocrete was less than that of lean concrete-SFRC. No cracking was observed in lean concrete-ferro-fibrocrete upto 180 kN under central loading condition although lean concrete base course cracked at much lower load. Minor cracks were observed on the surface of lean concrete-SFRC composite slab under edge and corner coading condition at 90 KN and 70 KN respectively. The study of structural behaviour of composite pavement slabs under static plate load tests established that composite pavement using lean concrete as base course may be used for lighter traffic condition.