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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,

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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