Page 184 - New Trends in Eco efficient and Recycled Concrete

156 New Trends in Eco-efficient and Recycled Concrete

Figure 6.2 Architectural mortar produced with waste glass cullet.

cement paste may develop deleterious expansion. Besides, the inclusion of waste
glass as aggregates in cement-based materials might lead to a modest decrease in
compressive strength resulting from the relatively weaker interface between the
cement paste and the smooth GC aggregates. Therefore, at the Hong Kong
Polytechnic University (PolyU), Lu et al. (2017a) used different supplementary
cementitious materials (SCMs) (e.g., fly ash, ground granulated blast-furnace slag,
metakaolin and waste GP) to improve the mechanical and durability properties of
architectural mortar prepared with 100% glass aggregates.
The experimental results suggested that the strength of glass-based architectural
mortars incorporating SCMs were comparable, and even superior, to that of the
pure cement mortar (see Fig. 6.3A). Although 50% cement was replaced by the
SCMs, the cement mortars produced with 100% GC after 90 days of curing could
achieve a compressive strength of 50 MPa and a flexural strength of 6 MPa, which
is sufficient for various applications in construction. Furthermore, the durability
results indicated that the addition of the SCMs could significantly reduce the drying
shrinkage of glass-based cement mortar. All the glass-cement mortars prepared with
SCMs showed favourable resistance to fire and lower strength losses after heating

to 800 C. In particular, the replacement of cement by SCMs suppressed the ASR
expansion to below the limiting level (see Fig. 6.3B).
In order to explore the feasibility to maximise the re-utilisation of waste glass in
cement mortars, Lu et al. (2017b d) employed waste glass not only as decorative
aggregates, but also as a supplementary cementitious material by milling the waste
cullet into glass power in the architectural mortar. They evaluated the performance
of the glass-based (both as aggregate and SCM) cement mortars in terms of fresh,
mechanical and durability properties. In terms of the fresh properties, when the par-
ticle size of the GP was reduced to the same level as that of the cement, the work-
ability and the stiffening rate of GP modified mortar were similar to that of the
control mortar. Similarly to other SCMs, the incorporation of GP could also signifi-
cantly reduce the drying shrinkage of the glass mortars regardless of its fineness.
Furthermore, using the GP and glass aggregates simultaneously could effectively