Strength Characteristics of Alkali-Activated Slag Mortars with the Addition of PET Flakes.

Agnieszka Kocot,Tomasz Ponikiewski,Jacek Katzer,Andrzej Ćwirzeń

doi:10.3390/ma14216274

Abstract

The production of ordinary Portland cement is associated with significant CO2 emissions. To limit these emissions, new binders are needed that can be efficiently substituted for cement. Alkali-activated slag composites are one such possible binder solution. The research programme presented herein focused on the creation of alkali-activated slag composites with the addition of PET flakes as a partial substitute (5%) for natural aggregate. Such composites have a significantly lower impact in terms of CO2 emissions in comparison to ordinary concrete. The created composites were differentiated by the amount of activator (10 and 20 wt.%) and curing temperature (from 20 to 80 °C). Their mechanical properties were tested, and a scanning electron microscope analysis was conducted. Compressive and flexural strengths ranging from 29.3 to 68.4 MPa and from 3.5 to 6.1 MPa, respectively, were achieved. The mechanical test results confirmed that a higher amount of activator improved the mechanical properties. However, the influence of the PET particles on the mechanical properties and microstructure varied with the curing temperature and amount of activator. Areas that require further research were identified.

Highlights

In 2018, the global production of cement exceeded 4000 Mt
Ground granulated blast furnace slag (GGBFS), which is typically used as a pozzolanic material added to Portland-cement-based systems, can be activated with strong alkalis
Tests conducted by Patel and Shah [12] proved that concrete based on GGBFS activated by sodium silicate and sodium hydroxide and cured at temperatures above 60 ◦C achieves higher compressive strength in comparison to concrete cured at ambient temperature

Summary

Introduction

In 2018, the global production of cement exceeded 4000 Mt. Cement production is the third greatest source of global CO2 emissions. Substitution of OPC with alternative binders [6] could significantly lower the carbon footprint of concrete [6] Such binders have been developed over the last few decades, and binders activated with alkali solutions seem to be the most promising [7]. Ground granulated blast furnace slag (GGBFS), which is typically used as a pozzolanic material added to Portland-cement-based systems, can be activated with strong alkalis. Replacing natural aggregates with PET particles decreased the compressive strength and lowered the durability [21]. PET particles, apart from traditional cementitious composites, have been used in the production of alkali-activated slag mortars [28]. The research programme presented tested the mechanical properties of alkali-activated composites based on GGBFS and cured at different temperatures.

Materials and Methods

Findings

Discussion

Conclusions