Field Experience on Performance of High Volume Fly Ash Concrete Pavement

Introduction

Road infrastructure projects constitute huge investments that have to serve the society for a long time. High investing cost involved in these projects has to be justified from the benefits of a concrete pavement with less maintenance and vehicle operation cost over longer design life. Efforts have to be made to avoid premature performance failure of concrete pavements since rehabilitation techniques for these pavements are costlier proposition compared to other pavements. Also there is a need for optimization of component materials used in the construction of these pavements to make them safe, environment- friendly and effective to cater to the demands of increasing traffic. It is imperative to keep a good level of competence between different types of road construction and also keeping the costs low.

As per published literature [1], a concrete having minimum cement replacement level of 50% by fly ash is termed as high volume fly ash concrete (HFC). HFC has low heat of hydration, reduced drying shrinkage and better workability. Hence HFC has got all the avenues to become a sustainable material especially for rigid pavement application. A minimum grade of M30 concrete which results in a minimum static flexural strength of 3.9 N/mm2 has been specified for pavement quality concrete by Indian Roads Congress [2].

Currently in India most of ready mix concrete for construction industry has fly ash between 20 to 30% of the cementitious material in it while Indian Roads Congress still have reservations towards usage of high volumes of fly ash and hence restricting the percentage of fly ash to 30% that also to be used only in rural roads but not for other important roads. Awareness about HFC is still very low. Hence confidence building process for utilization of HFC for pavements is essential which can be achieved by field studies.

There are very limited field studies available on rigid pavement response in Indian scenario. Only few demonstration road projects have been undertaken in India to familiarize Indian practitioners with high volume fly ash concrete. Construction of high volume fly ash concrete road (on experimental basis of about 1 km length) was taken up jointly by Public Works Department, Raichur, Karnataka State and Central Road Research Institute Delhi using 50% replacement level. Also Associated Cement Company (ACC) has constructed demonstration roads using high volume fly ash concrete with 50% replacement at its Greater Noida and Faridabad Ready Mix Plants. Muncipal Corporation Delhi has constructed a 100m stretch of pavement of 7m wide at Fatehpur Beri, Mehrauli, New Delhi, with high volume fly ash concrete utilizing 50% cement replacement level.