Aim concreted was hardened and compacted using a

Aim

The aim of this experiment was to determine how the
workability of fresh concrete and hardened concrete is effected by the water
content value.

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Introduction

Construction of civil engineering structures
require background information on the compressive strength of concrete. For
example, if a sample of concrete has low tensile strength it would be crucial
to reinforce it a material that does have high tensile strength such as, steel
rods. Reinforcement of such materials would increase the overall tensile
strength of the concrete allowing it support larger loads (Fanella, 2015,
p.274)1.

Experimental
Procedure

In order to determine the workability of fresh
concrete the slump test was conducted.

The procedure began by placing the aggregates,
cement and sand into a bucket after being weighed. To manufacture the concrete
mix, water was added. The amount of water added varied for each group (refer to
table 1).

A cone mould (100mm top diameter, 200mm bottom
diameter and 300mm in height) was moistened to allow a reduction of surface
friction on slump (About Civil)2.
The freshly manufactured concrete was then poured and compacted using a metal
rod into the mould. After the mould was filled and excess concrete was scraped
off, the mould was lifted in an upward steady motion revealing the unsupported
concrete. Due to the lack of support, the concrete slumped. The decrease in
height of the fresh concrete from before and after the mould was removed is
referred to as slump (refer to table 1).

To measure the compressive and tensile strength
values, fresh concreted was hardened and compacted using a vibrating table with
at a speed of 400hz, in accordance to the BS EN 12390-2:2009(The British Standard
Institute)3.

Fresh concrete was hardened into the following
shapes; 100mm cubes, 100mmx100mmx500mm beam and 100mm in diameter by 200mm
height cylinder (The British Standard Institute)4.

The concrete moulds were left to cure at 20ºC under
water and were tested 14days after curing.

The beam was used to determine the flexural tensile
strength of the concrete sample. The Zwick Rowell Z350 universal testing
machine was used. The beam sample experienced a loading rate of 0.5kN/s until a
fracture appeared on the specimen (refer to table 3).

The cube samples were used to test the compressive
strength of concrete. The cubes were singularly placed in the ELE ADR- Auto 2000KN
compression testing machine (refer to table 2). The same machine was used on
the cylinder sample (refer to table 3). All samples experienced a 0.3kN/s loading
rate. The duration of both tests were dependent on when a fractured appeared on
the surface of the samples.

1 David A. Fanella.(2015). Reinforced Concrete Structures: Analysis and
Design, Second Edition. McGraw Hill Professional. Original work
published 2015.

2 Aboutcivil.org, Concrete Slump Test
Procedure, Applications & Types of Slump. Retrieved from:
https://www.aboutcivil.org/concrete-slump-test.html. Date accessed: 25/01/2018

3
British Standards Institute. (2009). BS EN 12390-2: Testing Hardened Concrete.
Part 2- Making and curing specimen for strength tests. Retrieved from https://bsol.bsigroup.com/

 

4
British Standards Institute. (2009). BS EN 12390-3. Compressive strength of
test specimens. Retrieved from https://bsol.bsigroup.com/Search/Search?OriginPage=Biblio%2Bsearch&facets=IcsCode_91&currentPage=1&pageSize=50&sortingOption=RelevanceDesc.
Date Accessed: 09/01/2018

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