Mechanical and Fresh Properties of Multi-Binder Geopolymer Mortars Incorporating Recycled Rubber Particles

Abstract

This paper examines the performance of multi-binder conventional geopolymer mixes (GCMs) with relatively high early strength, achieved through curing at ambient temperature. Mixes incorporating ground granulated blast-furnace slag (GGBS), fly ash (FA) and microsilica (MS) and sodium metasilicate anhydrous, were assessed in terms of workability, mechanical properties and embodied carbon. A cement mortar was also prepared for the sake of comparison. The best performing GCM was then used as a reference for rubberised geopolymer mixes (RuGM) in which the mineral aggregates were replaced by recycled rubber particles in proportions up to 30% by volume. Experimental results were combined with embodied carbon estimations in a multi-criteria assessment to evaluate the performance of each material. A mix with a 75/25 GGBS-to-FA ratio, in which 5% MS was added, had the best performance in terms of strength, workability, water absorption and environmental impact. The compressive strength was above 50 MPa, similar to that of the cement mortar. The latter had significantly higher embodied carbon, with factors ranging between 3.48 to 4.20, compared with the CGM mixes. The presence of rubber particles reduced the mechanical properties of RuGM proportionally with the rubber amount, but had similar workability and embodied carbon to CGMs. Finally, a strength degradation model is validated against the tests from this paper and literature to estimate the compressive strength of RuGM, providing reliable predictions over a wide range of rubber contents.

Workability and Durability of Concrete Incorporating Waste Tire Rubber: A Review

“…The presence of rubber improved the workability of the composite binder ground polymer mortar, but the effect was not significant. The mixes with the highest rubber content (30%) had an average 5% higher flow diameter over the reference group mixes, and the mixes with a lower rubber content (20%) had an average 8% higher flow diameter over the reference group mixes [35]. The workability of light-rubber concrete with ordinary silicate cement was not as good as that of light-rubber concrete with geopolymers, with the former being approximately 56% lower than the latter.…”

“…5, the effect of eggshell powder on the slump was not as great as that of tire powder. In the case of no eggshell powder, the Table 1: Slump of RC with varying RA size and content adapted with permission from reference [19], Copyright © 2021, Elsevier B.V., reference [20], Copyright © 2010, Springer, reference [34], Copyright © 2015, Elsevier B.V., reference [21], Copyright © 2008, Elsevier B.V., reference [30], Copyright © 2007, Springer, reference [35] slump value at 5% rubber powder replacement rate decreased by approximately 13%. However, when the eggshell powder replacement rate was 15%, the slump value was 0 with an increase in rubber content.…”

“…However, it was approximately 17% lower than that in the control (REF). The smaller the rubber particles, the more likely they are to absorb water, probably because the presence of the alkali exciter increases the surface roughness of the rubber particles [35]. At low rubber admixtures, the slump of concrete with 5-10 mm rubber particles was larger than that of 2-5 mm, but as the admixture increased to 40%, the slump of the coarser-grained self-compacting rubber concrete was approximately 50 mm lower than that of the finer group, as can be seen from Fig.…”

Evaluation of One-Part Slag–Fly-Ash Alkali-Activated Mortars Incorporating Waste Glass Powder

“…Calcium-rich binders are useful to achieve high mechanical early-strength, though GGBS-only AAMs have quick setting time limiting the practical application of one-part AAM systems (Abdelmonim and Bompa, 2021). Some amount of FA is needed as alumina release is quicker than the silica release in one-part AAM.…”

Progress in Sustainability and Durability of Concrete and Mortar Composites

“…Another pressing issue of the modern society is related to the increasing number of discarded worn tires. In view of ever stricter regulations in terms of landfills, tire components found their way in mortar and concrete mixes either in terms of distributed textile and steel fibers as reinforcement or as aggregates [19,20].…”