Development of Fly Ash & Bottom Ash Based Alkali Activated Paver Blocks

Abstract

Paver blocks made of different materials have been in use since thousands of years. Con- crete paver blocks has been extensively used in many countries for quite some time as a specialized problem-solving technique for providing pavement in areas where conven- tional types of construction are less durable due to many operational and environmental constraints. Today, the demand of paver blocks is increasing day by day as they are the most preferred choice for paving of footpaths, parking plots, bus stops, industries, etc. More advanced interlocking designs of paver blocks have increased the public appeal due to its aesthetic beauty. Ordinary Portland cement (OPC) is used as the primary binder to concrete paver blocks. However, it is well known that the production of OPC not only consumes significant amount of natural resources and energy but also releases substantial quality of carbon dioxide to the atmosphere. The global cement industry contributes around 2.8 billion tons of the greenhouse gas emissions annually, or about 7% of the total man-made greenhouse gas emissions to the earth's atmosphere. It is es- sential to find alternatives to make environment friendly concrete to produce paver blocks. One of the alternatives to produce environmentally friendly concrete is the development of inorganic alumina-silicate polymer or alkali activation of aluminosilicate materials and al- kaline liquids, called alkali activated concrete, which utilize the polycondensation process to attain the strength. Aluminosilicate materials should be rich in by-product materials such as y ash, bottom ash, slag, rice-husk ash, red mud, etc. Alkaline liquids are soluble in nature and have sodium and potassium base. By exploring use of the y ash and bottom ash based alkali activated paver blocks two environment related issues are tackled i.e. the high amount of CO2 released to the atmosphere during production of OPC and utilization of y ash and bottom ash. In this major project, the basic information and design parameters of paver blocks such as materials, size, shape, weight, colour, area, mix proportion, compaction type, mix ho- mogeneity, manufacturing process, cost of production, cost of purchase, type of machine used, cost of machine, etc. are to be collected from the different local manufacturing plant of paver blocks to study the mix proportion and casting procedure of paver blocks. For experimental work Class F y ash and bottom ash from local suppliers has been used to produce alkali activated paver blocks. Experimental work comprises investigation on consistency and setting time of alkali ac- tivated mortar with different proportion of y ash and bottom ash. To develop the mix design of paver blocks, the effect of variation in source material and other salient parameters on compressive strength of alkali activated concrete has been investigated. Parameters related to source materials such as ratio of y ash to bottom ash 70:30, 50:50 and 30:70 and amount of source material in the range of 393 kg/m3 to 429 kg/m3 are to be varied. Other parameters includes alkaline liquid to source material ratio 0.35 and 0.4, alkaline liquid ratio 2 and 2.5, concentration of NaOH solution 8M, 10M, 12M 14M and 16M, addition of super plasticizer 0% and 1%, extra water content 10% and 15%, rest period 1 day and 2 day etc. have been varied throughout investigation. The parameters giving satisfactory and economical results are selected for making y ash and bottom ash based alkali activated paver blocks. The density of alkali activated paver blocks was found equivalent to that of conventional OPC paver blocks. The zigzag type paver blocks of 60 mm thickness as per IS provisions has been casted for the investigation of the properties of the paver blocks i.e. compressive strength, abrasion resistance and water absorption. Results of properties of alkali activated paver blocks have been compared with the the results of commercially available OPC paver blocks. Specimens have been tested at 7 and 28 days, respectively.