Fly ash is a waste product from thermal power plants where pulverized coal is used for the as per the literature review GouravHYPERLINK "http://biblioteca.universia.net/autor/Gourav,%20K.html", Studies, 2007. Fly ash is being utilized in the blended cements, additive for concrete and manufacturing of concrete blocks and bricks. Fly ash-lime-gypsum bricks are being manufactured and marketed throughout the country. The literature review on fly ash-lime-gypsum (FALG) mixtures as intended to manufacture bricks or blocks for masonry applications indicates several gaps in understanding the various aspects of the technology. The present thesis is an attempt to understand the behavior of compacted stabilized fly ash mixtures for the manufacture of fly ash bricks and characteristics of masonry using such bricks. A brief introduction to the technology of compacted stabilized fly ash bricks for structural masonry is provided. The main focus of the investigations is on arriving at the optimum stabilizer-fly ash mixtures considering density, stabilizer-fly ash ratio, curing conditions, etc. as the variables. Therefore the parameters/variables considered in the investigation include: (a) density of the compacted fly ash mixture, (b) stabilizer-fly ash ratio, (c) curing duration (normal curing and steam curing) and (d) dosage of additives like gypsum. The investigations clearly show the possibility of producing bricks of good quality using compacted fly ash-lime gypsum mixtures. Wet compressive strengths of 8- 10 MPa was obtained for compacted fly ash-lime-gypsum bricks at the age of 28 days. Wet strength to dry strength ratio for these bricks is in the range of 0.55 – 0.67. Initial tangent modulus for the fly ash-lime-gypsum bricks in saturated condition is in the range of 8000 – 12000 MPa. There is a large scope for selecting optimum mix ratios of Fly ash, sand, lime and other additives to obtain a specific designed strength for the brick. The thesis ends highlighting major conclusions of the investigations.
A general study conducted on M30 strength of neat FaL-G has indicated that 1.5 times of its dosage by weight, as against OPC, keeping the other aggregate same, renders a mortar or concrete of parallel grade strength. A Study on workability for M15 grade concrete has not shown any slump, unlike OPC. The additional 50% input of FaL-G cement might have rendered relatively better cohesion for wet concrete to show this phenomenon. Hence a different approach to study workability of FaL-G concrete has to be developed. Even at low workability, this can be considered as roller compacted concrete.
FaL-G can replace OPC in many avenues. The reinforcement behavioral studies in reinforced FaL-G cement concrete (RFCC) are in progress but the postulations indicate that the constituent of FaL-G being 1.5 times more than OPC by weight which in other words 3 times by volume of account of two to one ratio in densities, the specific area of cement matrix is relatively larger in RFCC than in RCC. Thereby reinforcement is more closely coated with cementitious gels and more safely ensured for water impermeability to veto the chances of corrosion. However FaL-G is weak abrasive product hence may be avoided on high abrasive prone areas, till its abrasive resistance is virtually improved. It is cheap in cost; transportation cost can be reduced by decentralizing the FaL-G cement activities.
Fly ash-based brick and cement are far superior in engineering properties over their conventional competitors. This knowledge needs to be disseminated globally, more so in second and third world countries, through tangible technical explanations (Bhanumathidas and Kalidas 2003). Although results of FaL-G bricks and hollow blocks were promising, and the technology could not be implemented due to initial consumer resistance in adapting to new...
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