Application of Fly ash and Bottom ash Based Alkali Activated Concrete Paver Blocks for Design and Construction of Rural Pavements

Abstract

Keywords: Alkali Activated Concrete, Fly ash, Bottom ash, Paver Blocks, Pavement, Mechanical Properties, Durability Properties The major problem the world is facing today is the environmental pollution. In paver block industry, portland cement is mainly used as a binder in concrete. 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-pro ducts as a substitute for OPC to manufacture concrete paver blocks. Present investigation relates to cement free alkali activated binder using combination of fly ash and bottom ash for manufacturing of paver blocks. No cement is used for the production of paver blocks and hence the final pro duct is sustainable. Paver blocks are a special solid and unreinforced precast piece of concrete which is now used for various applications such as footpaths, parking plots, bus stops, industries, pavement etc. But the paver blocks which are available locally are made of ordinary portland cement. However, it is well known that the production of OPC not only consumes significant amount of natural resources and energy but also releases substantial quantity of carb on dioxide to the atmosphere. By exploring use of the fly ash and bottom ash based alkali activated concrete paver blocks, two environment related issues are tackled with i.e. the high amount of CO 2 released to the atmosphere during the production of OPC and utilization of abundantly available & not so well utilized fly ash and bottom ash. The present investigation is started by collecting the basic information related to commercially available paver blocks like variations in constituent materials, size and shape, compressive strength, cost of paver blocks, etc. from different paver block manufacturers. The experimental work is aimed at making a rural pavement using alkali activated concrete paver blocks. For using alkali activated concrete paver blocks in the pavement, their cost shall be less as compared to that of commercially available paver blocks as well as their mechanical & durability properties shall be at par with the commercially available paver blocks. For developing the optimized mix design of alkali activated concrete paver blocks, optimization of various constituents such as aggregate content(%), alkaline solution to source material ratio, source of bottom ash, etc. are varied. From the results of said trial mixes, the parameters giving satisfactory and economical results are selected for making fly ash and bottom ash based alkali activated concrete paver blocks. The unipaver type paver blocks of 60 mm thickness as per IS provisions have been cast. Mechanical properties of the paver blocks such as compressive strength, flexural strength, split tensile strength, abrasion resistance, etc. are evaluated. Durability properties of paver blocks such as water absorption, acid resistance, alkali resistance, sulphate resistance and leachate test are also investigated for alkali activated concrete paver blocks and corresponding compared with commercially available paver blo cks. A small prototype pavement of size 2.5 m width and 4 m length is designed and constructed at the Nirma University campus using the fly ash and bottom ash based paver blocks prepared as discussed above. Half stretch of the said pavement contained paver blocks of alkali activated concrete & the remaining half stretch of the pavement is cast using the commercially available paver blocks of M 35 grade. Visual inspection is in process to find any damage in form of cracks and deformation on the pavement. No cracks or deformation is observed even after 6 months of completion of construction of the pavement. For evaluating suitability of alkali activated concrete paver blocks for low volume traffic, a rural pavement of size 2.5 m width and 16 m length is designed and constructed at nearby Jaspur village using the alkali activated concrete paver blocks of M 35 grade. After 3 months of completion of construction of pavement, no damage in the form of cracks and deformation is observed. Parametric study is carried out to evaluate the change in mechanical properties by changing the shape of paver blocks from Unipaver to Hexagon as well as of Brick. Also change in mechanical properties is evaluated by changing the thickness of paver blocks from 60 mm to 80 mm. The parametric study is further extended by evaluating the change in mechanical properties of the paver blocks by changing the source of major constituents like the fly ash and bottom ash from gandhinagar thermal power plant to cuttack thermal power plant.