Application of Fly ash And Bottom ash Based Alkali Activated Concrete for Construction of Rigid Pavement

Abstract

Large portion of India is covered by villages where the roads are falling into of low volume traffic category. The main problem of the rural roads is that their maintenance is neglected. The durability of the bituminous surface road is low so the cement concrete road offers an alternative for such type of road with considerably good durability. In concrete Pavement construction, portland cement is mainly used as a binder. Cement which is used to make concrete, contributes tonne of greenhouse gas emissions annually to the earth's atmosphere. On the other hand, the large amount of availability of fly ash, bottom ash, rise husk ash, GGBFS, etc. worldwide creates opportunity to utilize these by-products as a substitute for OPC to manufacture the concrete. Present investigation relates to cement free alkali activated binder using combination of fly ash and bottom ash for manufacturing of the concrete and checks its suitability for the pavement construction. Present investigation is started by designing the low volume traffic rigid pavement as per IRC: SP: 64 and minimum grade of concrete is decided for the same. Granular sub base (GSB) and wet mix macadam (WMM) is selected for the sub grade of the rigid pavement and the mix design for both the grade is done as per MORTH guidelines. To achieve minimum required grade of concrete, optimization of mix design of alkali activated concrete is conducted. For developing the most optimized mix for alkali activated concrete, variations in different parameters like type of admixture, alkaline solution ratio, molarity of alkaline solution, alkaline solution to binder ratio and binder material ratio are employed. From the results of the parametric study, the mixture giving required strength and economical results is selected as final mix for the pavement. From the parametric study two mixes have been finalized. One having fly ash to bottom ash ratio 80:20 (F80B20) evaluated for using during temperature ranges between 35˚C to 45˚C where as the other mix having ratio 100:0 (F100) for temperature ranges between 20˚C to 30˚C. Mechanical properties of the selected alkali activated concrete mixes are evaluated like compressive strength, split tensile strength, flexural strength, impact energy and abrasion resistance. Durability properties such as water impermeability, acid attack, chloride attack, sulphate attack and shrinkage are evaluated for checking the suitability of the selected alkali activated concrete for the rigid pavement. From the results it is observed that the performance of the alkali activated concrete is higher compared to control concrete. Monitoring of the alkali activated concrete paver blocks pavement constructed at Jashpur Village near Ahmedabad during April, 2017 is carried out after ten months in February, 2018. The properties of the paver blocks extracted from the pavement are evaluated which includes the compressive strength, breaking load, abrasion resistance and leachate test after the completion of ten months after the execution of the pavement. The results of the above said properties of the paver blocks are compared with the corresponding properties of the paver blocks after 28 days. The higher rate of abrasion is observed due to vehicular traffic after ten months. Flexural cracks on the bottom face of paver blocks were observed due to coarser sub grade used for the pavement and poor surface finishing during manufacturing of the alkali activated concrete paver blocks. Flexural strength and compressive strength is reduced after ten months of the construction. The properties of the virgin alkali activated concrete paver blocks like impact energy and shrinkage is evaluated and the results are compared with the commercially available OPC concrete paver blocks. The theoretical prediction of drying shrinkage of the paver blocks is carried out by the Gilbert method and the results are compared with the experimental results. The performance of alkali activated concrete paver blocks for aforesaid properties is better as compared to commercially available OPC concrete paver blocks.