Page 64 - New Trends in Eco efficient and Recycled Concrete

40 New Trends in Eco-efficient and Recycled Concrete

as long as there is adequate management of these materials applied by engineers,
constructors or plant managers.

2.2.5 Processing and improvement techniques of BA
Several processing systems can help to modify the properties of BA to improve
their properties. Specifically, there are three research works in which different pro-
cesses were carried out.
Firstly, in the work of Rosales et al. (2017) several BBA processes were applied
to produce recycled mortar. The presence of light particles and organic matter con-
fer to the BBA certain physical and chemical characteristics which significantly
reduces the possibility of reuse. Three processes were applied on BBA, crushing,
burning and eliminating lightweight particles.
In this work, physical and chemical properties of unprocessed and processed
BBA were studied for comparison. The results revealed that by applying combus-
tion and crushing processes a relevant increase in the compressive strength of the
mortar was achieved for substitutions in respect to unprocessed BBA mortars. This
fact is very interesting because if additional physical processes are applied in BBA,
it is possible to significantly improve their properties to manufacture mortar and
concrete.
Secondly, Fukasawa et al. (2017) proposed the application of the syntheses of
potassium-type zeolites (K-zeolites) from BFA via a hydrothermal route, which
represents a novel use for this material. The syntheses of potassium-type zeolites
(K-zeolites) from BFA via a hydrothermal route were applied. An aqueous solution
extracted from biomass incineration with a high concentration of potassium was
employed to substitute the KOH solution in the synthesis of K-zeolites. In this work
they were combined this extract of BFA with coal FA.
Thirdly, Alkali activation of BFA combined with metakaolin (MK) has been
investigated in recent years. Several works have been carried out in this sense, and
will be discussed in a later Section 2.4 of this chapter.

2.3 Utilisations of biomass fly ash (BFA) and biomass
bottom ash (BBA) in concrete design

Major challenges will arise relating to the efficient management of BFA and BBA
by-products or waste. The primary concerns are ash storage, ash disposal, ash usage
and the presence of unburned carbon. The use of ash from the combustion of bio-
mass is conditioned by its physical-mechanical properties.
There is not much literature on the use of ashes coming from the combustion of
biomass in construction materials (especially in cement-based materials) and its use
is limited to materials of medium resistance, partially replacing some of its compo-
nents (cement or aggregates) so that the properties are not affected.