International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 05 Issue: 01 | Jan-2018 www.irjet.net p-ISSN: 2395-0072 © 2018, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 1056 Influence of flyash on Fineness, Porosity and Permeability of Flyash blended Cement paste Priyanka Singh 1 , N.D.Shah 2 , P.K.Majumdar 3 1 Research Scholar, Department of Civil Engineering, C.U.Shah University, Gujarat, India 2 Professor & Dean, School of Engineering, P. P. Savani University, Gujarat, India 3 Professor, Department of Civil Engineering, C.U.Shah University, Gujarat, India ---------------------------------------------------------------------***---------------------------------------------------------------------- Abstract - This paper investigates the effects of the fineness of flyash cement paste on the porosity and permeability of mortar mixtures with replacement of cement at different percentages. The fly ash were used to replace Portland cement at replacement percentage of 0% (which was the control mix), 10%, 20%, 30%, 40%, and 50% by cement weight. Test results demonstrate that using fly ash as a cement replacement resulted in a reduction in the maximum temperature rise in mortar because of the fineness of the fly ash. The effects of the fineness and shape of fly ash on the porosity and air permeability of cement pastes were investigated. Portland cement was outmoded with fly ash at the dosages of 0, 10%, 20%, 30%, 40% and 50% by weight replacement. The results show that the porosity and air permeability of the pastes are influenced by the shape, fineness, and replacement level of fly ash. The permeability of cement fly ash pastes decreases with the increase in re- placement level and fineness. Decrease in porosity and permeability are due to a combined effect of the packing of fine particles, the pozzolanic reaction of fly ash, and the hydration of cement. Key Words: Flyash, Fineness, Permeability, Porosity, Cement flyash paste. 1. INTRODUCTION In designing concrete structures, durability is one of the most paramount properties to be considered, in additament to the competency of the structure to resist all loads. Concrete durability depends largely on fluids in form of liquid or gas mi- grating through hardened concrete. Concrete is a porous material; ergo, moisture kinetics’ can occur by flow, diffusion, or absorption. The ingress of sundry ions, liquid, and/or gas from the environment is responsible for deterioration and damage of concrete .It is generally accepted that the pore structure and porosity of pastes, mortars, or concrete are among the most consequential properties and vigorously affect both its mechanical properties (creep, and shrinkage) and convey properties (permeability, diffusion, and absorption). Convey properties are intimately cognate to the resistance of concrete structures to sundry durability quandaries and controlled by the pore size distribution network of hardened cement pastes and concrete. Fly ash is a pozzolanic material and a by-product from combustion of pulverized coal in an electricity power plant. Characteristics of fly ash vary due to coal type and combustion condition. Utilization of this fly ash is still constrained due to the lack of understanding on the characteristics of fly ash itself and the properties of fly ash concrete. Albeit many re- searchers investigated the influences of fly ash on the porosity and air permeability of coalesced cement pastes, few re- searchers were found dealing with the fineness and shape of fly ash and their influences on the properties of hardened cement pastes. Understanding the effects of the fineness and shape of fly ash on the porosity and air permeability of cement pastes will lead to an incrementing utilization of fly ash in concrete. 2. Experimental Program The chemical composition of cement and flyash with the percentage is tabulated in Table 1. Table 1. Chemical composition of cement and flyash Oxide Composition Cement (%) Fly Ash (%) SiO 2 21.28 56.58 Al 2 O 3 5.6 27.83 Fe 2 O₃ 3.36 4 CaO 64.64 4.3 MgO 2.06 1.4 SO 3 2.14 - Fineness’s of cement and fly ash is shown in Table 2. It can be observed that the fineness of the raw material is increasing from cement to fly ash after being processed. From the Blaine fineness test, the fineness of cement resulted is 3100.43 cm²/g; while the fineness of fly ash as collected is 5502.62 cm²/g. From these results, it can be seen that fly ash is finer than cement. Table 2. Fineness of cement and fly ash Material Fineness (cm²/g) Cement 3100.43 Fly ash 5502.62 A constant dihydrogen monoxide-to-binder ratio (w/b) of 0.35 was maintained in this study. Cylindrical paste specimens with 38 mm in diameter and 65 mm in height