Effect of superplastizicer type on the fresh and strength properties of alkali activated slag composites

Abstract

Nowadays, the demand for green concrete has increased due to the greenhouse gas emissions and uncontrolled pollution from the cement industry. At the same time, the green concrete should exhibit better mechanical properties and durability characteristics when replacing conventional concrete without compromising on the fresh properties. A better solution for the production of green concrete is to use air cured Alkali Activated Slag (AAS) composites, an innovative and sustainable binding material with very low carbon footprint. However, AAS exhibits demerits such as quick setting and poor workability and this demands the use of superplasticizers in such binder systems which are less explored thus far. Hence, this paper presents a study on the influence of superplasticizer type on the fresh and strength properties of AAS mortar. Paste/mortars were prepared with alkali activators composed of sodium silicate and sodium hydroxide and tested to study the setting times, workability, and evolution of compressive strength. It is found that the fresh properties are improved by increasing the alkali to binder ratio and the dosage of superplasticizer. Both sulphonated naphthalene formaldehyde (SNF) and polycarboxylate ether (PCE) based admixtures were found to be effective in alleviating the negatives of air cured alkali activated paste/mortar systems.