Title: Alkali-Activated Natural Pozzolan/Slag Concrete: Fresh and Strength Properties

Author(s): Meysam Najimi and Nader Ghafoori

Publication: Symposium Paper

Volume: 326

Issue:

Appears on pages(s): 18.1-18.8

Keywords: alkali activation; binder combination; fresh properties; natural pozzolan; slag; strength properties

DOI: 10.14359/51711000

Date: 8/10/2018

Abstract:
This study assesses the fresh and strength properties of alkali-activated natural Pozzolan/slag concretes. For this purpose, three alkali-activated concrete mixtures were made using natural Pozzolan/slag combinations of 30/70, 50/50 and 70/30; sodium hydroxide/sodium silicate combination of 70/30; sodium hydroxide concentration of 1.75M; and an alkaline activator solution-to-binder ratio of 0.54. A reference Portland cement concrete was made with a similar water-to-cement ratio of 0.54 for the purpose of comparison. The studied properties included flow, setting time, unit weight, compressive strength, tensile strength, and elastic modulus. The flow and setting time of alkali-activated concretes considerably reduced with increases in slag portion of binder. Their flow was lower than that of the reference Portland cement concrete. The setting times of alkali-activated concretes were in acceptable ranges and close to those of Portland cement concrete. For all the strength properties evaluated, a 50/50 combination of natural Pozzolan and slag produced the highest ultimate strength values. The increase in slag portion of binder to 70%, however, accelerated the initial reactions, leading to the highest early-age compressive strengths. The compressive strengths of alkali-activated concretes reached to similar values produced by the reference Portland cement concrete. A similar trend was found for tensile strength and elastic modulus.