Discussion Pielert (2006, p.289)2 suggest w/c to
The analysis of figure 2 suggests
as the water content increases the slump value is also seen to increase. The
noticeable trend further implies, concrete mixtures with higher w/c values to
also have higher workability. However more workable mixtures are prone to be weak
in strength. Because of this, Caldarone (2009, p.87)1
states it would be more beneficial to use fine aggregates when manufacturing
concrete as it wouldn’t increase workability to the extent were it loses its
strength making it easier to work with without loss in strength.
In figure 2 the graph shows a
slight decrease in slump when the water content was at the highest. This can be
considered an anomaly which has risen due to inconsistencies during the slump
test procedure. An example maybe that the concrete was too tightly compacted
into the mould, therefore once the mould was removed the concrete was unable to
slump correctly, thus allowing an inaccurate reading to be recorded.
Lamond and Pielert (2006, p.289)2
suggest w/c to have a direct relationship with the compressive strength of
concrete. This is because although concrete does need a certain amount of water
to keep hydrated and develop strength, when excessive water is present the
strength is actually decreased. This decrease in strength occurs as there are
more water filled pore spaces between the grains (Wilby,1991)3.
However figure 3 does not support this claim as there is no evident
relationship shown between the water to cement ratio and the compressive
strength. Absence of this evidence in the results may be due to errors which
occurred during the experimental procedure. For instance, the machinery used
may have not been calibrated correctly before use leading to inaccurate readings
being recorded. Errors may have also risen when the calculations for the
compressive strength values were conducted.
Figure 1 shows us as the water
content increases the density decreases. This behaviour can be supported by the
idea that when concrete has a higher water content value it also has an
increased volume of voids decreasing both the density and strength.
Lastly figure 4 shows the flexural
test to be higher than the splitting tensile stress. However both of these
values when compared to the compressive strength value are significantly lower.
This difference in values is evident because when compressive force is placed
upon a concrete specimen a higher amount of energy is needed to break the
atomic bonds causing an increased amount of energy being needed to be able to
break the bonds (Caldarone, 2009, p.85)5. However figure 4 does not
show a clear trend and therefore it would be crucial to repeat the tests to get
more accurate and precise readings.
In conclusion, increased water content increased
the workability of fresh concrete and thus in hand should have decreased the
compressive strength of hardened concrete. However the results collected only
supported the relationship between w/c and workability. To continue the
compressive strength values were found to be significantly high compared to the
flexural and splitting tensile stress values. However a clear link between both
the flexural and splitting tensile stress values against the cement to water
ratio was not portrayed across the result. Overall the lack of correlation
amongst the recorded results suggest further tests need to be carried out to
gain a more accurate and clear understand of the behaviour of concrete.
Caldarone, M.A. (2009).High strength
concrete, a practical guide. USA: Taylor & Francis. (Original work
2 Lamond, J.F., Pielert, J.H.(2006). Signifiance of Tests and Properties of
Concrete and Concrete-Making Materials. USA: ASTM International.
Wilby,C.B. (1991) Concrete material &
Structures. Cambridge: Press Syndicate of the University of Cambridge.