Effect of Steel Fibers on Heat of Hydration and Mechanical Properties of Concrete Containing Fly Ash

Sajid Mehmood,Faheem Butt

doi:10.22581/muet1982.1901.07

Abstract

This study investigated the effects of steel fibers on the fresh and hardened properties, and heat of hydration of concrete containing FA (Fly Ash). A total of 192 samples were cast comprising cubes, cylinders, and prisms, for six concrete mixes with varying contents of steel fibers by volume and a fixed content of FA i.e. 15% by weight of cement. The semi adiabatic setup was used to monitor temperature rise due to the heat of hydration in the concrete mixes for fourteen days. The use of FA increased workability, and decreased early compressive strength, tensile strength and heat of hydration of concrete. However, an increase in the compressive strength of FA concrete was observed by the addition of steel fibers up to 0.9% whereas a consistent increase in the splitting tensile strength and modulus of rupture was observed with the addition of the steel fibers from 0.4-1.8%. Further the test results showed that increasing steel fibers content decrease the evolution of heat due to hydration. It was concluded that the FA concrete with steel fibers can be used in precast industry and mass construction projects due to the improved mechanical properties and lower heat of hydration.

Highlights

This study investigated the effects of steel fibers on the fresh and hardened properties, and heat of hydration of concrete containing FA (Fly Ash)
(ii) The replacement of 15% FA in concrete decreased early compressive strength (3 days) by 37% as compared to OPC mix whereas the addition of steel fibers from 0.4-0.9% in the FA concrete increased the same by about 38.5% as compared to FA15 mix and 2.4% as compared to OPC mix
The workability of FA concrete decreased by about 63% when the steel fibers are increased from 0.4-1.8% by volume of concrete

Summary

Introduction

This study investigated the effects of steel fibers on the fresh and hardened properties, and heat of hydration of concrete containing FA (Fly Ash). The use of FA increased workability, and decreased early compressive strength, tensile strength and heat of hydration of concrete. It was concluded that the FA concrete with steel fibers can be used in precast industry and mass construction projects due to the improved mechanical properties and lower heat of hydration. A decrease in early strength can be observed in concrete where cement is replaced with FA [18]. It becomes important generally, to improve early strength of concrete containing FA, for example, to make possible its use in pre-cast industry or in colder regions where formwork strips delay the further construction. Other supplementary materials like Silica Fume can improve the early strength of concrete but it will affect durability of concrete [19]

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Conclusion