5200CIV - Concrete Degradation, Permeability & Strength Lab Report

This Materials 1 lab report from Liverpool John Moores University (Unit Code: 5200CIV) investigates the degradation of concrete, focusing on the impact of cement replacement materials on compressive strength, ultrasonic pulse velocity (UPV), and surface hardness. The report details experiments using pressure regulators, permeability vacuum cells, Schmidt rebound hammers, and UPV testers to assess concrete samples with varying replacement contents, including PFA, GGBS, and micro silica. Results indicate that replacement materials generally improve concrete strength, UPV, and surface hardness, although surface quality and susceptibility to corrosive agents can vary. The report concludes that while replacement materials enhance certain concrete properties, careful consideration is needed to ensure overall durability and resistance to weathering.

Materials 1
Lab Materials Report
Liverpool John Moores University
Unit Code: 5200CIV

LAB MATERIALS
 Introduction:
the degradation of concrete by the degrading agents starts from the outer
surfaces where it is exposed to the agents. Due t the inadequate hydration, the
outer surfaces are usually at low toughness (Charmkar, 2017). In addition,
Charmkar, (2017) also noted that factors such as curing periods, autogenously
contraction and vaporization of cavity moisture are able to contribute to high
capillary efficiency of the materials near these surfaces. In an experimental
program, the effects of some of key factors such as curing, porosity, mix
designs and cement types use on material air permeability has been analyzed
and detected. In consistence with the conventional methods and discovered
flow law, the information for air penetration was tested. Most importantly, the
concrete materials can be calculated by considering the extreme permeability,
details of the core concrete pore and near surface structure, curing conditions
as well as the transport effectiveness (Figg, 1973 and Charmkar, 2017). The
main factors which contribute to the corrosion of concrete include the
movement of gases of presence of aggressive water solutions. Loss of water
and inadequate hydration in the exposed concrete surfaces lead to higher
coarser and more porosity systems when compared to inner parts of the
concrete which are not exposed to the agents (Charmkar, 2017). In addition,
other conditions which lead to more destruction of the exposed surfaces of
construction materials include high carbonization, presence of high levels of
ions and resilient impacts with high humidity and frosts. The concrete
toughness is defined by absorption properties as well as the permeation of
concrete surface (Charmkar, 2017).
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LAB MATERIALS
Permeability and durability of concrete can be tested using the defined
nondestructive methods. The presence of voids, cracks, faults and other key
factors of pre-cast or in-situ concrete in the surfaces can be tested using
Ultrasonic pulse velocity tester (Patel and Patel, 2011). The same method is
used for long term checking of constructions to determine their environmental
performance. In order to get information about permeability, creation of feed
rhythms of sounds into the material is done. Then gauge of the interval of the
pulse which the sound takes to go forth and back into the concrete from the
source antenna to the receiver valve is done (V.S, 2017). In addition, the same
method is able to bring out the information on concrete materials hardness or
durability. Another key method used is the accelerometer popularly known as
test hammer. The method utilizes the application of non-ruinous pressure to
estimate the quality of cement on the heap bearing limit (Patel and Patel,
2011). The end goal that the solid pound hits the solid is able to measure the
guidelines. Upon hitting the hard solid, the body bounces back. The level of
bouncing back is then measured by use of a gadget which can be translated to
compressive quality (Patel and Patel, 2011).
 The major equipment which are utilized in the above experiments
include:
Experiment 1:
 Pressure regulator/pump
 Permeability vacuum cell
Experiment 2:
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LAB MATERIALS
 Schmidt Rebound Hammer
 Control compressive testing machine
 Pundit
 Method:
First, vacuum is created in the 2-diameter chamber. The vacuum is directed to
the key surface of the concrete by the use of the couple of tabular rings, which
is generated by two discrete chambers. The vacuum cavity is created for about
30 to 60 seconds whereby after that readings going as high as 50 mbars
relating to the materials and device. The valve to the outlet 2 is then shut and
the internal cavity is inflated and separated from the device. The compression
is increased as the air within the crevices of the device moves over the outer
materials all the way to the chamber. The constant air permeability has a direct
relation to the amount of compression in the surface of the material. In
addition, compression controller is installed to regulate the compression in the
external area, which is at equilibrium with the internal compartment. The
regulation of uni-movement of air in the internal area is able to make sure that
the penetrability of air, represented by kT in m2 can be measured by the
following formula;
kT=[V_c/A]^2 μ/(2εP_a ) ((ln (P_a+∆P_i)/(P_a-∆P_i ))/(√(t_f )-√(t_o )))^2
Where:
kT= air-permeability and it is measured in m2
V_c= inner cell Volume measured in m3
A= area of inner compartment m2
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LAB MATERIALS
μ= air viscosity which is a constant at (= 2.0 .10-5 Ns/m²)
ε= outer surface concrete porosity (assumed = 0.15)
Also, another procedure which can be applied to experiment 2 is;
first, the rebound hammer is placed at normal reading by hitting it against
anvil. This ensures that the hammer will be able to reflect the accurate
readings. After resetting, the hammer is held at right angle to the surface of the
concrete surface. Any orientation can be used to conduct the testing according
t ones preference as long as the hammer is held at right angle to the material.
At the end, the same procedure is repeated on other key samples which has
cement replacement materials.
 Results:
after completing the experiment, the different replacement contents are added.
This helps to improve the quality of the concrete. According to the figure
below has the evidence that the different air permeability constant and
Schmidt hammer are able to realize the different replacement materials.
According to table one, it is clear that UPV values for PFA are slight lower
when comparing them with same measurement for 100% concrete. In addition,
GGBS concrete and CSF concrete have increased UPV measurement. This
shows that the replacement materials are able to improve the compactness of
the concrete materials. Also, the Schmidt hammer is able to increase. Same
way, the resulting compressive strength of the concrete is able to increase.
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LAB MATERIALS
The different replacement materials are able to increase the strength, UPV as well as
the surface hardness of concrete materials as seen in the experiment 2. Moreover, the Kt
values are also able to indicate an increase using this method. Nevertheless, the trend is not
uniform as seen in the table a drop in the Kt value for GGBS replaced material is
experienced. The depth of the air penetration is able to experience the same penetration.
Nevertheless, as the GGBS values decreased, the PFA and silica values recorded an increase.
Additionally, even with the increase in strength of the replacement material, UPV and surface
hardness of the concrete were unable to improve the quality of the concrete surface and
therefore able to expose the material to the corrosive agents.
 Experiment 2 Results:
 Ultrasonic pulse velocity (UPV) measurements (km/sec)
concrete PFA Concrete GGBS
Concrete
Micro silica
(CSF) Concrete
4.767 4.674 4.845 5.042
 Schmidt Hammer measurements
concrete PFA Concrete GGBS
Concrete
Micro silica (CSF)
Concrete
36.9 39.6 41.8 47.9
 Compressive Strength measurements
concrete PFA Concrete GGBS
Concrete
Micro silica (CSF)
Concrete
19.7 21.15 25.2 26.16
 Normal and Cement replacement w/c 0.5–
 PFA (Pulverized Fuel Ash) 30%–
 GGBS (Ground Granulated Blast Furnace Slag) 60%–
 Micro Silica (condensed silica frame) 10%–
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LAB MATERIALS
Cement
content
Water Fine Agg.
360 180 518 437 874
Cement
content
Water Fine Agg.
252 180 518 437 874 108
Cement
content
Water Fine Agg.
144 180 518 437 874 216
Cement
content
Water Fine Agg.
324 180 518 437 874 36
 Results for experiment 2:
Control PFA(30%) GGBS (60%) Micro Silica
(10%)
Kt-Perminability
coefficient (
1.484 1.49 1.308 2.753
L-depth of air
penetration
Quality class of
concrete surface
Bad (4) Bad (4) Bad (4) Bad (4)
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LAB MATERIALS
 Discussion:
from the available results, it can be seen that the replacement materials are
able to improve the strength, the UPV and also the surface hardness of the
concrete materials. The literature of these conclusions can be found on the
available documents. The different materials which are used for replacement
are able to have different effects on concrete as seen in the graph below
(Charmkar, 2017). Also, Charmkar also notes that the replacement materials
are able t0o influence the compressive strength of a material. Split tensile is
affect6ed by the addition of the different substances to the concrete (V.S,
2017). The quality of the replacement material when added into concrete is
able to reduce both the split tensile and flexural strength (Nehdi, Pardhan and
Koshowski, 2004). T5hios is the main reason which can be provided for the
deviation of 60% observed ion GGBS, there the depth of penetration reduces
instead of increasing. Essential amount of concrete is usually replaced in most
experiments which seek to test replacement materials and lead to an increase
of resultant air absorption rate increase (V.S, 2017). Nevertheless, this was not
experienced in this experiment. The main reason for this observation is the
use of different materials while replacing concrete. The materials have
different air and water absorption rates. The different characteristics can be
seen whereby micro silica is highly hydroscopic, while PFA has moderate air
and water absorption rates. GGBS is used in this experiment due to its low
water absorption capacity (Patel and Patel, 2011). For all replacement
materials, the UPV measurement is able to increase meaning that the materials
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LAB MATERIALS
decreases air permeability of the concrete. When the air permeability
decreases, concrete quality of the material improves therefore the structure or
brick designed from the replacement material turns to be more stronger when
compared with 100% concrete. The measurements from Schmidt hammer are
able to show this. In this experiment, measurements of 100% concrete of
Schmidt hammer were recorded as 36.9. The hardness in the concrete was
recorded from an increase of the measurement of PFA and GGBS concrete
which increased. In addition, micro silica has high water and air absorption
rates and led to the highest Schmidt measurement. Direct relationship was
noted from the experiment between the strength of concrete and UPV
measurements. Therefore, this shows that the more replacement materials are
added to the concrete, the improvement and hardness in the concrete is
achieve. Nevertheless, it is observed that the hardness increase does not
contribute to the surface quality. The three substances were able tom make
concrete more susceptible to corrosive agents. This is confirmed by the
increased rate of penetration that is seen in the PFA, GGBS and micro silica.
Thus, even with the success of replacing material being able to improve its
hardness and UPV outcome of the concreted, it was able to it to weathering
agents because of the poor surface hardness.
 Conclusion:
As per the experiment, increase in UPV, Schmidt hammer, and strength
measurements were achieved. This is the same in the many literatures which
are able to indicate that the effect of adding replacement material to concrete
increases strength. From the experiment, the strength of concrete is increased
when the replacing material is increased by reducing the air permeability. In
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LAB MATERIALS
addition, it is also established that regardless of the increased improved
concrete hardness due to the replacement materials, the surface quality was not
affected. This meant that the concrete surface could still be exposed to the
corrosive agents occasionally.
 References:
Charmkar, C. (2017). Compressive Strength and Workability of Concrete
Using Stone Dust as Partial Replacement of Sand and Glass Powder as
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LAB MATERIALS
Cement. International Journal for Research in Applied Science and
Engineering Technology, V(VIII), pp.427-442.
Figg, J. (1973). Methods of measuring the air and water permeability of
concrete. Magazine of Concrete Research, 25(85), pp.213-219.
Nehdi, M., Pardhan, M. and Koshowski, S. (2004). Durability of self-
consolidating concrete incorporating high-volume replacement composite
cements. Cement and Concrete Research, 34(11), pp.2103-2112.
Patel, P. and Patel, D. (2011). Effect of Partial Replacement of Cement with
Silica Fume and Cellulose Fibre on Workability & Compressive Strength of
High Performance Concrete. Indian Journal of Applied Research, 3(7),
pp.263-264.
V.S, S. (2017). Experimental investigation of strength properties of concrete
with partial replacement of cement with glass powder and fine aggregate with
foundry sand. International Journal Of Engineering And Computer Science.
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