Recycled Glass as Aggregate for Architectural Mortars

Francesca Tittarelli,Alessandra Mobili,Chiara Giosuè

doi:10.1186/s40069-018-0290-3

Abstract

The possibility of recycling mixed colour waste glass as it is for manufacturing decorative architectural mortars, has been investigated. In mortars, the 0–33–66–100% of calcareous gravel volume has been replaced with recycled glass cullets, with no other inorganic addition. To mitigate the possible alkali–silica reaction, mixes with a hydrophobic admixture were also compared. The obtained results show that the replacement of calcareous gravel with glass cullets of similar grain size distribution permits to reduce the dosage of the superplasticizer admixture to obtain the same workability of fresh mortar; it does not affect significantly the mechanical performances, the water vapour permeability and the capillary water absorption but it reduces significantly the drying shrinkage deformation. The used recycled glass is classified as no reactive in terms of alkali–silica reaction neither in water nor in NaOH solution following the parameters of the current normative, even in the absence of the hydrophobic admixture. The hydrophobic admixture further delays the expansion trigger but not the speed of its propagation.

Highlights

1.1 Waste Glass Three different types of glass are produced: flat glass, hollow glass, and wool and glass yarn
The same results have been obtained by Jian-Xin Lu and Chi Sun Poon in Alkali Activated Cement (AAC) mortars as the replacement level of natural sand by glass cullet was increased (Lamond and Pielert 2006)
The expansion increases with the dosage of recycled glass in the mix, and at the 100% of gravel replacement with waste glass it remains lower than the limits prescribed by the rule for classifying the aggregate as reactive, both with and without the hydrophobic admixture (Fig. 9)

Summary

Background

1.1 Waste Glass Three different types of glass are produced: flat glass, hollow glass, and wool and glass yarn. Green and brown glass sand mortars proved to be innocuous, regardless of the replacement level, whereas clear glass can exhibit potential deleterious properties (Sikora et al 2016) Supplementary cementitious materials, such as fly ash (FA) (Kou and Poon 2009; Parghi and Shahria Alam 2016), metakaolin (MK) (Guo et al 2015; Ling and Poon 2011), ground granulated blast furnace slag (GGBS) (Ling and Poon 2014; Li et al 2017) and nanosilica (Sikora et al 2016; Aly et al 2012) are well-known to be able in reducing the alkali–silica reaction in concrete because the amount of alkali hydroxide can be reduced by the pozzolanic reaction (Carsana et al 2014; Shayan and Xu 2004; Topçu et al 2008; Corinaldesi et al 2016). Since ASR is an expansive reaction that occurs between soluble silica and the cement alkalis only in the presence of water (Penacho et al 2014), hydrophobic treatments, which make concrete less susceptible to water saturation, could mitigate the possible arising of the phenomenon

Experimental Investigation

Results and Discussion

Capillary Water Absorption and Expansion Due to Alkali–Silica Reaction

Conclusions