Page 1 of 17
European Journal of Applied Sciences – Vol. 9, No. 6
Publication Date: December 25, 2021
DOI:10.14738/aivp.96.11475. Dorcas, O. B. (2021). Investigating the Strength Properties of Concrete containing Construction & Demolition waste using Response
Surface Methodology Techniques (RSM). European Journal of Applied Sciences, 9(6). 629-645.
Services for Science and Education – United Kingdom
Investigating the Strength Properties of Concrete containing
Construction & Demolition waste using Response Surface
Methodology Techniques (RSM)
Oluyemi-Ayiniowu Bamitale Dorcas
School of Engineering & Engineering Technology
Department of Civil Engineering, Federal University of Technology
Akure, Nigeria
ABSTRACT
The framework through which waste from Construction and Demolition activities
could be reused in concrete was developed using the Response Surface
Methodology techniques. An experimental design to determine the proportions of
CDW waste which include Recycled Concrete Aggregate (RCA) and Recycled Fine
Aggregate (RFA) to be mixed with other concrete constituents using Central
Composite Design (C.C.D) orthogonal design was performed. Four factor variables
which include %RCA to replace granite, Water-cement ratio, %RFA to replace river
sand and RCA aggregate size was used while the response variable is the concrete
compressive and flexural strength. Thirty (30) experimental runs were generated
and conducted. The result was then analyzed using the RSM regression analysis. The
result showed that %RCA showed the highest influence on both compressive and
flexural strength of the CDW concrete. The Contour analysis also showed the
behavior of the strength properties of CDW concrete to different variations of the
factor variables. The research showed that the use of CD waste in concrete
production help improve the properties of concrete.
Keywords: Response surface methodology; Construction and demolition waste; Central
Composite Design; Flexural Strength; Compressive Strength.
INTRODUCTION
Buildings, roads, highways, bridges, utility facilities and dams are examples of civil-engineering
structures where significant volumes of construction materials are used. When new buildings
and civil engineering structures are renovated or demolished, construction and demolition
(CD) materials are produced. Concrete, glass, plastics, salvaged building components and other
large, heavy materials are frequently contained in CD components. According to Shen et al. [8],
“C & D waste is as a combination of surplus constituents generated from construction,
renovation and destruction activities such as site clearance, land excavation and roadwork and
demolition”. The majority of CD trash generated in Nigeria is being disposed of in out-of-state
landfills, with only a small percentage being recycled.
From 2015 to 2019, construction and demolition (CD) activities in Nigeria produced 1.13 billion
tonnes, whereas in the United States they produced over 530 million tonnes [9]. When
compared to other industrial categories, construction operations in Nigeria are the second
greatest generator of garbage, second only to the plastics, food and beverage industry,
Page 2 of 17
630
European Journal of Applied Sciences (EJAS) Vol. 9, Issue 6, December-2021
Services for Science and Education – United Kingdom
accounting for 35 percent of total waste creation [9]. According to the Environmental
Protection Agency’s waste characterization analysis in the Advancing Suitable Materials
Management 2018 fact sheet, slightly over 455 million tonnes of CDW debris were diverted into
next use (recycling) out of 600 billion tonnes of CDW waste created in the United States while
the remaining were sent to landfills. The situation in underdeveloped countries in which
Nigeria belongs to is the inverse. The majority of garbage created in Nigeria, including CDW, are
disposed of in landfills. Unlike some other construction waste materials, which can either be
reused in the construction process or sold, CDWs can only be utilized as a filler material, and
the vast majority of it (more than 90 percent) ended up in landfills. However, the rapid growth
in real estate construction over the last three years has resulted in a scarcity of land and had
forced urban housing development near landfills, posing numerous environmental risks. As the
rate of development rises, more CDWs will be generated, causing greater waste management
issues. As a result, sustainable alternatives to reusing construction demolition wastes (CDWs)
created in the building industry are required [10].
LITERATURE REVIEW
Concrete is the most frequently used construction material in the world; the raw ingredients
required are readily available in most parts of the globe, and its manufacture does not
necessitate sophisticated or expensive machinery [1]. Concrete is a high-strength, long-lasting
composite material made up of cement, fine and coarse aggregate. The rapid rise of
urbanization and industrialization has resulted in a substantial increase in consumption.
Because natural aggregate makes up more than 70% of the volume of concrete, any increase in
its use will increase the amount of natural aggregate consumed [11]. In Nigeria, around 40
billion tons of natural aggregate are consumed each year in the manufacturing of concrete to
meet the various needs of the construction industry. Concrete is a non-sustainable material due
to this vast use of natural resource. Thousand of years are required to create a natural aggregate
source. The pace of natural aggregate formation is substantially lower than the current rate of
consumption, which can only lead to its depletion. [12]. As a result, efforts to find and employ a
suitable alternative construction material that is both cost-effective and viable in terms of
strength and durability have intensified [1]. Because CDW is made from building debris, it has
qualities that are similar to natural aggregates, such as high-water absorption that can be
lowered by adding tiny granular particles. The use of CDW as a substitute aggregrate for
concrete reduces natural aggregate usage as well as landfill difficulties. [13].
Response Surface Methodology (RSM) is a statistical analytic technique in which each response
is linked to a set of variables in order to evaluate the effect, relationship and interaction
between the variables and the response. RSM analysis entails creating a series of experiments
and collecting the experimental results as responses, then validating the accuracy and
optimizing the variables to satisfy the intended response using response surface numerical
models. [2]. RSM is a useful statistical method for designing experiments, generating models,
evaluating factors and finding the best search conditions. RSM is frequently employed in
circumstances where a number of variables influence one or more performance aspects, such
as the response. It’s used to improve one or more responses or to meet a set of requirements.
[3-6]. RSM offers statistically proven predictive models that may be tweaked to discover the
best process set-up. When numerous factors influence one or more performance attributes or
reactions, RSM is commonly utilized. RSM, as an optimization tool, is used to improve one or
more responses or to meet a set of requirements. RSM interprets experimental results using a
Page 3 of 17
631
Dorcas, O. B. (2021). Investigating the Strength Properties of Concrete containing Construction & Demolition waste using Response Surface
Methodology Techniques (RSM). European Journal of Applied Sciences, 9(6). 629-645.
URL: http://dx.doi.org/10.14738/aivp.96.11475
non-linear response surface approach and gives sufficient experimental interpretations as part
of the final result [14]. The stages involved in most RSM applications include:
o A screening factor, which is run to reduce the number of factors (independent) variables
to a relative few, so the procedure will be more efficient and require smaller number of
runs or tests.
o Determination is made on current levels of the major effect factors resulting in a value
for the response that is close to the optimum region. If the current levels of the factors
are not consistent with optimum performance, then the experimenter must adjust the
process variables that will lead the process toward the optimum level.
o Researchers carry out the chosen experimental design according to the selected
experimental matrix.
o Mathematical/statistical models of the experimental design data are developed by
fitting linear or quadratic polynomial functions. The fitness of the models then needs to
be evaluated.
o The stationary points (optimum values) are obtained for the variables
MATERIAL AND METHODS
Materials Used
Grade 42.5 Portland cement, high range water reduction admixture, river sand with a specific
gravity of 2.58 as fine aggregate, granite passing through sieve size 20 as coarse aggregate, and
portable water for mixing were utilized in the concrete preparation. The water admixture was
employed to improve the concrete’s workability. The Recycled Coarse Aggregate (RCA) or
simply recycle aggregate (RA) used in this study was extracted from construction demolition
waste at recycling centers. The Recycled Fine Aggregate (RFA) used consisted of broken glass
and ceramic tiles. These materials was extracted from construction demolition wastes and then
grounded together into finer particle sizes corresponding to that obtained from the Response
Surface Methodology C.C.D experimental design.
Experimental Mixing and Casting
The cement rate was kept constant in the concrete mix samples, while the river sand was
partially replaced by recycled fine aggregate (RFA) and the granite by recycled coarse
aggregate. The Central Composite Design type of the Response Surface Methodology
Experimental designs determined the percentages of replacement in both circumstances. A
tilting drum mixer was used to make the concrete mix. The mixer’s revolution speed was
60rpm, and the total mixing time was variable. Compressive and flexural strength tests were
performed on 100mm x 100mm x 100mm casted cubes and 225mm x 450mm beams
respectively. The casted samples were prepared by pouring the concrete into a pre-lubricated
mould and compacting it in three stages. These samples were then covered in wet sacks for 24
hours in the laboratory before being de-moulded and cured in water before testing. The
compressive and flexural tests were performed after 28 days
Compressive Strength Test
The compression testing machine was used for the testing. Before putting the specimen, the
bearing surface of the supporting and loading rollers were wiped clean. The specimens were
positioned by applying a weight on the uppermost surface of the specimens. The specimens
were positioned with the loading device with great care. The maximum load was recorded
when the dial stopped moving while the load was steadily increased. The specimen’s