Material Saving Qualities of Systems with Recycled Waste Reinforcement

The provided content discusses the suitability of precast concrete systems in waste reduction and environmental protection. The focus is on using recycled wastes and by-products from other production processes to mitigate construction costs and provide a reliable disposal mechanism. The study aims to measure the strength properties of these materials compared to regular concrete, with the objective of reducing material wastage and costs further while promoting environmental friendliness.

STUDENT NAME - 42908 - Assignment 2
By ‘Author Name’
“Modular Construction Using Precast Concrete in Order to Reduce Wastages and
Environmental Degradation”
Affiliation (MSc Profile or Track) & Study no
Abstract
Over the past few decades, there has been a growing necessity to cut down on wastages in the
construction sites. Unfortunately, the conventional construction systems provide for very
little to waste mitigating measures. A higher cost of production further comes up as a result
and environmental degradation comes about due to the fact that wastes are environmental
pollutants. This has promoted the adoption of precast concrete systems. The construction
(operation) process would change significantly due to the difference in material application
but this ultimately reduces the amount wastages. This is attributable to the off-site manner of
member element casting that happens in a minimal wastage industrial processes. With that in
mind, further research has been suggested to curtail wastages, costs and further improve
sustainability while using the precast concrete.
1. Introduction
With wastes accounting for close to 6% - 9% of total project costs in the construction
industry, the amount of losses is very significant considering the high cost of projects
(Blismas, et al., 2010). This industry still remains one of the most profitable sectors of the
economy which leads to most attempts to mitigate wastage in construction sites being
uneconomical, a factor which further facilitates construction to carry on without proper
preventive measures. As a result, both the technical and client parties incur huge costs
considering the fact that the wastes have to be accounted for. Building projects that utilize
concrete as the main material, in most cases, usually end up with a wastage factor of between
5% - 10% of the overall costs. These wastes also contribute to a variety of environmental
problems which have proven to be a setback in the construction industry. This waste material
is mostly in the form of concrete, used formwork, steel and it is usually a result of human and
environmental factors within the site environment (Tam, et al, 2005).
Whereas the disposal mechanisms currently being used help achieving a reduced waste
impact on the environmental, the responsibility falls upon engineers and contractors to find a
balance between waste free constructions and healthy profit margins. More alternatives that
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reduce the amount of wastages and improve the quality of work too therefore have to be
developed (Mao, et al., 2013). This is where modular construction techniques come in as
manufacturers can come up with environmentally friendly materials while at the same time,
implementing environmentally friendly building methods that also give way for the
incorporation of sustainable energy. While relying heavily on existing literature, this review
will concentrate on precast concrete systems explaining how and when these systems are
used, their material saving and environmental friendliness, the gaps in the research and
further link them to my research project.
2. Literature review
Modular construction systems categorically offer a solution to the issue of waste reduction.
This is advantageous for developers seeking to increase their profit margins based on the
favourable economies of scale of the total cost of the development. As argued by Lu Aye, T.
Ngo, R. H. Crawford, R. Gammampila and P. Mendisa, modular systems provides up to 51%
material saving by mass by incorporating reused materials in modular construction that used
timber, steel and concrete (Lu, et al., 2012). Concrete is one of these modular construction
materials whose application has been increasing gradually over the years for this very reason.
As a fact, a study by Weisheng Lu and H. Yuan indicates a wastage factor of only 2% or less
when utilizing precast concrete in construction (Lu, 2013).
In using precast concrete systems, the person using it may choose to go with a fully modular
approach or the inclusion in situ concrete during construction various stages. When
construction teams utilize this precast approach, however, they may do so for specific
member elements including slabs, columns and beams. The reasons for using these members
include good insulation, easy demolition, higher frame strength and cost reduction (Arif,
2010).
When looking at the various approaches to this system, 2 main approaches stand out whose
difference is in the percentage amount of precast elements used. They are discussed below.
Fully precast concrete systems: this is where all member elements are cast off site and
transported to the site. Some of the best examples of these of the application of precast
modular structures are artificial harbours and bridges. One of the most recognized examples
is the Mulberry Harbour that was temporarily constructed by the British during the Second
World War to provide a platform for quick offloading of cargo along the beaches of
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Normandy, France. At present, most bridges are constructed using prefabricated member
elements where the only in situ components are the abutment (Li, Z., et al., 2014).
As argued by researchers R. Lawson, R. G. Ogden and R. Bergin, precast concrete systems
have a proven record of maintaining high levels of structural durability and stability as all the
member elements have better tensile and compressive strengths compared to the conventional
in situ members (Lawson, et al., 2011). This provides the client and contractor with a better
schedule management and waste saving system. When considering the economies of scale,
larger projects that use precast concrete are ultimately much cheaper to run and develop than
their in situ concrete alternatives.
The economic aspect of this system can however be non-existent when comparing to the
conventional systems currently in use. This mean that, for smaller structures, the economies
of scale apply. Where development projects are smaller, there are significantly less wastes
and time spent and this usually less and this leaves very little room for extra economic
recovery (Blismas, et al., 2010). In actual sense, they could end up being more expensive than
the conventional concrete systems. This is because of their relatively higher production costs.
Questions have also been raised by researchers about their seismic performance with some
researchers suggesting they could be weak.
Partial precast concrete systems: these is usually when the construction utilizes both precast
and in situ concrete in the same project. These practices are currently incorporated in high-
rise structures such as warehouses plazas, residential high-rise blocks, bridges, harbours.
These may not be as strong as precast structures but they also exhibit high levels of structural
durability and reliability (Azman, et al., 2010). Partial precast concrete systems can be an
advantage to developers constructing small units as, they are much cheaper than their
alternatives e.g. those with three floors or less (Azman, et al., 2010).
The major disadvantage that this system is that it is prone to wastages when comparing it to
the alternatives. In actual sense, waste is significantly reduced when comparing the
development to concrete structures cast right there on site. They are, prone to some slight
wastage as using the in situ cast concrete system leads to wastage.
The research gaps existing in the in the body of knowledge relating to precast systems is in
complementary sustainable material incorporation. While it has been noted that modular
construction does, in a lot of cases utilize reused materials, very few materials have been
researched on that complement the precast concrete systems. These materials could include
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recycled reinforcement fibres made of a variety of materials that could include steel, nylon,
fibreglass, organic sisal fibres etc (Wang, et al., 2010). Cement admixtures and alternative,
sustainable alternatives to both coarse and fine aggregates could also be researched on that
are both environmental friendly and reduce overall construction costs.
3. Evaluation
The research conducted in this field indicated both positives and negatives, some of which
are in direct contrast with each other. While Arif, in his journal paper highlighted precast
systems as being more cost effective than other construction methods, W. Lu and H. Yuan
greatly emphasize the additional costs of the transportation associated with precast systems
(Arif, 2010), (Lu, 2013). These normally come about as some construction sites are far away
from the factories which, in comparison to conventional methods using in situ material that
are readily available, is fairly costlier.
M. Kamali and K. Hewage in their research on the life cycle of modular structures argue that
modular construction provides a better life cycle, a point E. M. Generalovaa, V. P.
Generalova and A. A. Kuznetsovaa agree with in a different research paper ( Kamali, 2016),
(Generalova, et al., 2016). With this in mind, further research can be done to increase this life
cycle and overall sustainability. R. N. Swamy, in 1990, conducted a research in fibre
reinforced concrete but their application was limited to in-situ cast concrete. Even then there
was a reduction in the amount of reinforcement used and also member dimensions e.g. slab
and beam depths were significantly reduced (Swamy & ed., 1990).
It is with this in mind that this research focuses on the effect of using sustainable fibres
during the casting of precast elements that provide for a similar or better life cycle, cut down
overall costs and are environmentally friendly. In utilizing them, material wastage will be
assessed comparing the material saving qualities of systems using both precast with
conventional reinforcement and those with environmental friendly reinforcement mechanism.
The reinforcement alternatives researched on will be limited to only those that are recycled
wastes and by products of other production processes that would go to waste. The reasoning
behind this research is that, while mitigating the amount of constructions event further, they
would also provide a solution to the increasingly challenging task of providing reliable and
safe disposal mechanism (Oyedele, et al., 2014). In reusing these waste materials, the
construction costs are ultimately lowered and adoption would be easier to propagate by
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marketing. The strength properties are to be measured and compared to regular concrete with
an objective target of examining whether they can provide a much better deal in the long run.
4. Conclusion
The review above illustrates the in-depth study that has been conducted in order to establish
the suitability of precast concrete systems in waste reduction and environmental protection.
While a lot of these systems have been adopted and are largely being utilized, the question of
reducing material wastage and costs even further has been raised. It is with these in mind that
further research has been suggested fibre reinforced precast concrete. These assumed result
would be further reduction in wastages, costs and more environmental friendliness.
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