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CHAPTER 3

EXPERIMENTAL INVESTIGATIONS 3.1 GENERAL

The choice of study area, the types of algal species considered, the details of

experimental investigations carried out under laboratory and field conditions, the

details of various analytical methods of investigations, phycochemical analysis and

macro-level studies carried out to ascertain the impact of biodeterioration, are

highlighted in this chapter.

3.2 MARINE ALGAE- DEFINITION, FIELD SURVEY AND

IDENTIFICATION

3.2.1 Definition

Seaweeds or benthic marine algae are the group of plants that live either in marine or

brackish water environment. Like the land plants, seaweeds contain photosynthetic

pigments and with the help of sunlight and nutrient present in the seawater, they

photosynthesize and produce food.

Seaweeds are found in the coastal region between high tide to low tide and in the sub-

tidal region up to a depth where 0.01 % photosynthetic light is available (Fig. 3.1).

Plant pigments, light, exposure, depth, temperature, tides and the shore characteristic

combine to create different environment that determine the distribution and variety

among seaweeds.

The important criteria used to distinguish the different algal groups based on the recent

biochemical, physiological and electron microscopic studies are: a) photosynthetic

pigments, b) storage food products, c) cell wall component, d) fine structure of the cell

and e) flagella. Accordingly, algae are classified into three main groups i.e. green

(Chlorophyta), brown (Phaeophyta) and red (Rhodophyta).

Seaweeds are similar in form with the higher vascular plants but the structure and

function of the parts significantly differ from the higher plants. Seaweeds do not have

true roots, stem or leaves and whole body of the plant is called thallus that consists of

the holdfast, stipe and blade (Fig. 3.2). The holdfast resembles the root of the higher

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plants but its function is for attachment and not for nutrient absorption. The holdfast

may be discoidal, rhizoidal, and bulbous or branched depending on the substratum it

attaches.

The stipe resembles the stem of the higher plants but its main function is for support of

the blade for photosynthesis and for absorption of nutrients from surrounding sea

water. The blade may resemble leaves of the higher plants and have variable forms

(smooth, perforated, segmented, dented, etc.). The important functions of the blade are

photosynthesis, absorption of nutrient. The most significant difference of seaweeds

from the higher plants is that their sex organs and sporangia are usually one celled or if

multi-cellular, their gametes and spores are not enclosed within a wall formed by a

layer of sterile or non reproductive cells.

3.2.2 Field survey and Identification

A quick field survey was carried out on a stretch of about 350 km coastline located on

the east coast of India, from Chennai (i.e. Madras, a sea port) to Karaikal. In the above

stretch of coastline, six prominent locations were selected such as ports, bridges etc.,

and the locally available algae where sampled and sent to Krishnamurthy Institute of

Algolgy, Chennai, for identification of the species. Based on the above input,

‘Chlorophyceae’ has been identified as the predominant class of marine algae present

in the above coastal stretches of east coast of India. Further, the predominant species

of the above class of algae were also identified as: (i) Enteromorpha clathrata (Roth)

(ii) Ulva fasciata (Delile) (iii) Chaetomorpha antennina (Bory; Kuetz). Salient

characteristics of the above three species are given in the Appendix B1.

3.3 CHOICE AND DETAILS OF STUDY AREA

The identified species of algae are also available throughout the east coast of India,

stretching from Madras to Kanyakumari - a distance of about 750 km. During the

course of field inspection, the various structures along the coast, wherein colonization

of algae is very highly prevalent has been identified and photographic views of them

are shown in Figs. 3.3 and 3.4. The above figures highlight the impact of algal

colonization on concrete structures. Based on the criteria of easy collection of algae

and the ease with which field studies can be conducted a local area is selected.

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Accordingly, Pondicherry coast located along the east coast of India was selected for

the present study. It is located south of Chennai (Madras) at about 140 km along the

east coast of South India. Pondicherry is bounded by the Bay of Bengal on the east and

all other sides are bounded by the South Arcot district of Tamilnadu. The latitude and

longitude of Pondicherry are: 11056’ N and 790

In order to study the biodeterioration of algae on concretes, sufficient numbers of

cubes (100x100x100 mm) were casted. Cubes thus cast were kept exposed in fresh

water and sea water (without colonization of algal on their surfaces), so as to serve as

‘control’ specimens for the biodeterioration studies. Further, colonization of algae on

concrete cubes were permitted under two environmental regimes, namely (i) under

controlled laboratory conditions and (ii) under actual field conditions in the chosen

study area. Concrete cubes ‘cured’ upto the normal age of 28 days were used for

colonization of algae. When the algal species were attempted to colonize on concrete

50’ E, respectively. Fig 3.5 shows the

location map of the study area. Pondicherry has an average maximum temperature of

31.5º C and an average minimum temperature of 23.9º C. The average annual rainfall

of the region is about 1300 mm.

3.4 LABORATORY AND FIELD INVESTIGATIONS

3.4.1 Choice of Grades of Concrete

As per IS 456 (2000), the minimum grade of concrete for use as a structural material

and (plain) concrete exposed directly along sea – cost shall be M20. Further, calcium

is the most essential for the metabolic activity of algae (see section 2.3.5). Generally,

higher grades of concrete contain higher amount of calcium and hence higher grades

of concrete are expected to provide a higher potential for the metabolic activity of

algae. In view of the above, two grades of concrete, namely M20 and M25 were

selected for the present study. The above two grades of concrete were expected to

influence the metabolic activity of the algae due to varying cement content present in

the mix. Indian Standard of mix proportioning [IS 10262 (1982)] was adopted for

obtaining the design mix proportions of the above two grades of concrete. Brief details

of the approach and mix proportioning calculations are given in Appendix B2.

3.4.2 Experimental Schemes

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cubes after 28 days, it was found that the entire algal species didn’t colonize, rather,

they became extinct. This phenomenon was observed upto 6 months of exposure, in

both the exposure conditions. The above phenomenon is quite expected as the algae

cannot survive such a high pH, that existed in fresh or at very young age of concrete.

However, as the age of concrete steadily increases the pH of concrete reduces due to

the hydration of concrete. Further, due to setting of equilibrium between the pH of

concrete and the exposure medium (i.e. sea water), the pH reaches a level which is

conducive for the colonization of algae. This is expected to take place only after 6

months. Hence, samplings of algal colonized specimens were done only after 9 months

of exposure in laboratory and field conditions for conducting various tests. Fig. 3.6

shows the very quick extinction of algae as soon as initiation of colonization in a fresh

concrete (under the laboratory condition).

Concrete cubes under the above two regimes were kept exposed for nearly two years.

After three months of exposure, concrete cubes were removed from the above two

environments and subjected to certain non-destructive tests like NDT, compressive

strength test and investigations using SEM and EDAX. Beyond three months and up to

18 months of exposure in the above two environments, the concrete cubes were

subjected to certain sophisticated analytical techniques like XRD, TGA and FTIR,

apart from the above investigations. Fig 3.7 shows the overview of experimental

scheme of investigations adopted in this study.

3.4.3 Control Specimens

M20 and M25 grade concrete cubes (24 numbers in each) were cast and kept

immersed in fresh and sea water (without the algal species) to serve as a ‘control’ for

the biodeterioration studies. Locally available potable water and the actual sea water

sampled from the coastal region of the study area were used. The characteristics of

water from the above two sources tested as per standards methods of APHA (2005) are

given in Table 3.1 and 3.2. Control specimens were also periodically removed from

the above two environments and subjected to a variety of test, as stated above.

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3.4.4 Algal growth on concrete cubes under laboratory conditions

Chlorophyceae was allowed to colonize on the concrete cubes kept in a commercially

available humidity chamber, which has inbuilt provision for imparting light energy

and maintaining humidity conditions for the sustained metabolic activity of the algal

species. Salient details of the humidity chamber are briefly described below.

The chamber is double walled, the inner one being made of stainless steel (304 / 316

grades) and the outer one of stainless steel or GI coated with epoxy powder. The space

between the double walls is filled with glass wool. The chamber is illuminated by a

bulb and cooling is provided by hermetically sealed compressor coupled with a air

cooled condensing unit. Stainless steel tubular heater with fins is provided to generate

steam and injecting it into the working chamber. Temperature is maintained using an

electronic digital temperature controller-cum indicator with dry and wet bulbs

(Fig. 3.8).

The ambient conditions maintained in the chamber for the experimental investigations

are as follows and they are partially based on the environments adopted by Dubosc et

al., (2001) for their experimental study.

(i) Samples were incubated under lighting conditions of 2000 lx, 12 h/day and

‘daylight’ with a white fluorescent lamp.

(ii) Temperature maintained at 300

(iii) Relative humidity (RH) maintained at 90%, through out the day.

C through out the day.

A variable temperature and R.H simulating the ‘day’ and ‘night’ effect, as was adopted

by Dubosc et al., (2001) could not be adopted in the present study, due to the

restriction imposed by the available equipment, that of the humidity chamber.

However, the above ambient conditions are generally, expected to accelerate the

colonization of algae, especially under laboratory condition, as they represent /

simulate the climatic conditions prevalent in the study area.

The algal colonization on concrete cubes in laboratory conditions is shown in Fig. 3.9.

3.4.5 Algal growth on concrete cubes under field conditions

Concrete cubes (M20 and M25 grades) were kept in the coastal area of Pondicherry

region (i.e. in the splash zone) where abundant growth of marine chlorophyceae was

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found so as to study biodeterioration under natural algal growth conditions (Fig.3.10).

The selected site has algal growth through out the year. Further the selected location is

expected to provide very good environmental conditions for the algal growth on

concrete cubes, as was evident during the field inspection undertaken prior to this

actual study wherein abundant growth of algae on stone and concrete surfaces were

found along the coastal stretches of the region. Moreover release of zoospores from the

existing attached surfaces is expected to attach on to the surfaces of concrete cubes

kept exposed in the coastal area and hence enhance the algal growth under the natural

marine environment Fig. 3.11. The ambient conditions and pH prevailed during the

study period are given in Appendix B3.

3.4.6 Sampling procedure

Specimens were periodically removed from the laboratory and field for conducting

various investigations. Before preparing the specimens for various analysis, the

biomass, namely the algal species colonized on the specimens were carefully scarped

and placed in sterile plastic containers and taken to the Krishnamurthy Institute of

Algology, Chennai, for identification and confirmation of species. Apart from the

above, samples were drawn from the concrete cubes for morphological

characterization. After conducting the compressive strength test (i.e. the destructive

test) the specimens were used for conducting various sophisticated analytical studies,

after duly completing the specific sample preparation procedure for each analytical

instrument investigation.

3.5 SOPHISTICATED ANALYTICAL INVESTIGATIONS

Samples drawn from algal colonized concretes i.e. from the control, laboratory and

field conditions, were subjected to various analytical investigations. The basic

principle involved in each method and the purpose of test etc., are briefly outlined

below. Scanning Electron Microscope (SEM) and Energy Dispersive X-ray analysis

(EDAX), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Fourier

Transform Infrared Spectroscopy (FT-IR) and Gas chromatograph – Mass

spectrophotometer (GC-MS) were the sophisticated analytical investigations

undertaken in this study.

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3.5.1 Scanning Electron Microscope (SEM)

It is generally used in petrographic analysis of cementitious materials and

microstructure studies of concrete. SEM imaging provides detailed images of the

microstructure that augment those from stereo and optical microscopy and the primary

advantages are the high-contrast images of the microstructure.

It is a qualitative study and in the present study, this method was used to understand

the morphological changes that might have occurred due to biodeterioration induced

by the algal species. For SEM studies, samples were dehydrated by using an acetone

series; critical point dried; and gold coated at 10−3

It is a non-destructive analytical technique which reveals information about the

crystallographic structure, chemical composition, and physical properties of materials

and thin films. This technique is based on observing the scattered intensity of an X-ray

beam hitting a sample as a function of incident and scattered angle, polarization, and

wavelength or energy. This is a quantitative method and using this method, the

mineralogical changes induced due to biodeterioration can be studied. The concrete

samples were analyzed by powder XRD using Philips PW1710 diffractometer

available with Earth Science Department, Pondicherry University, Pondicherry, India.

It has a automatic slit under the following conditions: emission radiation = CuKα,

voltage=40kV, intensity=30nA, gonimeter speed = 0,1 20/s. Gonimeter calibration

was performed using silica standard and the data was interpreted using X’Pert High

mm Hg in sputter coat apparatus.

SEM and EDAX analysis were carried on in Hitachi S-3400N microscope, available

with Central Instrumentation Facility, Pondicherry University, Pondicherry, India.

3.5.2 Energy Dispersive X-ray analysis (EDAX)

This technique is used for identifying the elemental composition in a specimen. It

works as an integrated feature of a SEM, and can not operate on its own without the

latter.

In this study, the above method was used to obtain the elemental composition of the

specimens, before and after the biodeterioration induced by the algal species.

3.5.3 X-ray diffraction techniques (XRD)

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Score. Samples were ground in agar mortar and sieved to obtain fraction of particle

size less than 53µm, for the above test.

3.5.4 Thermogravimetric Analysis (TGA)

It measures the change in weight of the sample while it is heated at a constant rate (or

at constant temperature), under air (oxidative) or nitrogen (inert) atmosphere. This

technique is effective for quantitative analysis of thermal reactions that are

accompanied by mass changes, such as evaporation, decomposition, gas absorption,

desorption and dehydration. This is a quantitative method and using this method the

utilization of calcium for metabolic activity of algal species from the change in the

Ca(OH)2 content of the samples can be determined.

Concrete samples were powered in silica mortar and sieved through 75μm sieve.

About 1 gm of the sample was used for the analysis. It has a balance sensitivity of

0.1μg. Type R thermocouple (Pt-13% Rh/Pt) was used for measurement of

temperature in the instrument. The sample was taken in a ceramic crucible and heated

from the room temperature to 1000oC at a heating rate of 10o

For the preparation of the samples, approximately 1.5 mg of the <63 μm fraction was

carefully mixed with 100 mg of powdered anhydrous KBr in an agate mortar. A

pressure of 10 tonnes was applied to this mixture for 5 minutes in order to obtain

transparent pellets. Identification is based on comparison of the bands of the recorded

FTIR spectra with those of a reference literature (Baltakys et al., 2004). FTIR spectra

C/min using air as a

medium under static condition. TGA was done using Q600 thermal analyzer, available

with Central Instrumentation Facility, Pondicherry University, Pondicherry, India.

3.5.5 Fourier Transform Infrared Spectroscopy(FT-IR)

It absorbs electromagnetic radiation in the infrared region of the spectrum which

results in changes in the vibrational energy of molecule. The vibrational energy is a

kind of fingerprint of a compound. This property is therefore used for characterization

of organic, inorganic and biological compounds. The band intensities are proportional

to the concentration of the compound and hence qualitative estimations are possible.

69

were recorded using Thermo Nicolet 6700 spectrometer, available with Central

Instrumentation Facility, Pondicherry University, Pondicherry, India.

3.5.6 Gas Chromatograph – Mass Spectrophotometer (GC-MS)

It is composed of two major building blocks: the gas chromatograph and the mass

spectrometer. The gas chromatograph utilizes a capillary column which depends on

the column's dimensions (length, diameter, film thickness) as well as the phase

properties (e.g. 5% phenyl polysiloxane). The difference in the chemical properties

between different molecules in a mixture will separate the molecules as the sample

travels the length of the column. The molecules take different amounts of time (called

the retention time) to come out of (elute from) the gas chromatograph, and this allows

the mass spectrometer downstream to capture, ionize, accelerate, deflect, and detect

the ionized molecules separately. The mass spectrometer does this by breaking each

molecule into ionized fragments and detecting these fragments using their mass to

charge ratio. These two components, used together, allow a much finer degree of

substance identification.

In the present study, the fatty acids present in algal species is ascertained using

Perkin-Elmer Auto System XL Gas Chromatograph – Mass Spectrophotometer (GC-

MS) with 11/73 DEC computer system, available in Chemistry Department, Anna

University, Chennai, India.

3.6 PHYCOCHEMICAL INVESTIGATIONS OF ALGAL SPECIES

Algal samples collected from the laboratory and field studies were subjected to

phycochemical investigations to ascertain the source and the constituents responsible

for the observed biodeterioration of concrete cubes, if any. The collected samples were

washed thoroughly to remove epiphytes, animal casting, attached detritus and sand

particles and the wet weight was taken. It was rinsed with distilled water and shadow

dried using aeration to avoid breakdown of secondary metabolites under sunlight and

high temperature prevailing in this part of the country. The dried algal materials were

weighed, chopped and milled. Then the samples were subjected to various procedures

to isolate fatty acids from the dried algae, the brief details of which are described in

70

Appendix B4. The extract from the above samples are used for FTIR and GC-MS

studies for identifying the various fatty acids present in the sample.

3.7 MACRO LEVEL STUDIES

Apart from the above two types of investigations (i.e. phycochemical and sophisticated

analytical methods), concrete specimens which were subjected to biodeterioration by

the algal species were subjected to: visual examination, non-destructive and

destructive tests. Ultra-sonic and rebound hammer tests and the compressive strength

were used to understand the changes in the macro level characteristics like loss in

compressive strength etc.

Specimens which were subjected to significant biodeterioration only were considered

for the above macro level studies according to IS: 13311 (Part 1 & 2) - 1992 and

IS: 516- 1959.

3.7.1 Visual Examination

Control specimens and algal colonized concrete specimens at 18 months under both

the exposure conditions, were subjected to visual examinations, to examine and record

the various physical changes that have taken place. Measurement of actual overall

dimension, (normal) diagonal and solid diagonal, weight, presence of cracks, pore (if

any) and the nature of pores (if present ) such as: size, diameter and depth, were

carried out. Further, pH and CaO of the control and algal colonized specimens were

determined and compared qualitatively with the results from analytical techniques.

Change in pH, especially reduction in pH of concrete can be independently determined

by the ‘phenolphthalein pH indicator test’. For the above test the surface of control and

algal colonized concretes were sprayed at the (top) surface with a standard

phenolphthalein indicator solution (i.e. 1gm phenolphthalein and 90 ml ethanol -

95% v.v ethanol, and diluted to 100 ml using distilled water). If there is change in

color (i.e. from colorless to purple red color), then it indicates that the concrete is still

highly alkaline. Otherwise, it indicates no change in color (i.e. the indicator will

remain colorless) thereby indicating that there is no change in alkalinity of concrete.

The above observations are made immediately after spraying the standard indicator

solution and after 24 hours.

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The results from the above observations are used to draw inferences on the effect of

biodeterioration of concrete.

3.7.2 Ultra Sonic Pulse Velocity (UPV) Testing

This method is based on the principle that the velocity of an ultrasonic pulse through

any material depends upon the density, modulus of elasticity and Poisson’s ratio of the

material. Comparatively higher velocity is obtained when concrete quality is good in

terms of density, uniformity, homogeneity etc.

The ultrasonic pulse is generated by an electro acoustical transducer. When it is

induced into the concrete from a transducer, it undergoes multiple reflections at the

boundaries of the different material phases within the concrete and a complex system

of stress waves are developed, which includes longitudinal (compression), shear

(transverse) and surface (Reyleigh) waves. The receiving transducer detects the onset

of longitudinal waves which is the fastest. The velocity of the pulses is almost

independent of the geometry of the material through which they pass and depends only

on its elastic properties.

UPV method is a convenient technique for investigating structural concrete. For a

good quality concrete the pulse velocity will be higher and for poor quality it will be

less. If there is a crack, void or flaw inside the concrete, which comes in the way of

transmission of the pulses, the pulse strength is attenuated and it passes around the

discontinuity, thereby making the path length longer. Consequently, lower velocities

are obtained.

The actual pulse velocity obtained depends primarily upon the materials and mix

proportions of concrete. Density and modulus of elasticity of aggregate also

significantly affects the pulse velocity. Any suitable type of transducer operating

within the frequency range of 20 KHz to 150 KHz may be used. Piezoelectric and

magneto-strictive types of transducers may be used and the latter being more suitable

for the lower part of the frequency range. The electronic timing device should be

capable of measuring the time interval elapsing between the onset of a pulse generated

at the transmitting transducer and on its arrival at the receiving transducer. Two forms

of the electronic timing apparatus are possible, one of which use a cathode ray tube on

72

which the leading edge of the pulse is displayed in relation to the suitable time scale,

the other uses an interval timer with a direct reading digital display. If both the forms

of timing apparatus are available, the interpretation of results becomes more reliable.

In the present study, TICO ultrasonic Instrument was used for the UPV test and

qualifying of concrete is assessed using the guidelines given in Table 3.3, in terms of

the ultrasonic pulse velocity.

3.7.3 Rebound Hammer Test

This method is based on the principle that the rebound of an elastic mass depends on

the hardness of the surface against which a mass strikes. When the plunger of rebound

hammer is pressed against the surface of concrete, the spring controlled mass rebounds

and the extent of such rebound depends upon the surface hardness of concrete. The

surface hardness and hence the rebound are taken to be related to that of the

compressive strength of concrete. The rebound value is read - off along a graduated

scale and is designated as the rebound number or rebound index. The compressive

strength of concrete can be read directly from the graph provided on the body of the

hammer.

In this study DIGI Schmidt 2000 was the make used for rebound hammer test. Table

3.4 gives the quality of concrete in terms of standard values of rebound number. In this

study, the calibration curve (as furnished by manufacturer) was directly used to obtain

the compressive strength of concretes. The values thus obtained are used in discussion

of results and to draw inferences.

3.7.4 Compressive Strength of Concrete

Compressive strength is the capacity of a material to withstand axially directed

pushing forces. When the limit of compressive strength is reached, materials are

crushed. The compressive strength of concrete is taken as its most common

performance measure and used in designing various structures. The compressive

strength is calculated from the failure load divided by the cross-sectional area resisting

the load and reported in units of N/mm2. In this study the test was carried on AIMIL

Compression Test- 3000 tonnes capacity machine.

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3.8 SUMMARY SEM, EDAX, XRD, TGA, FTIR, GC-MS were the various analytical techniques used

for various qualitative and quantitative studies related to biodeterioration. Further,

macro-level studies on algal colonized studies (NDT and compressive strength) were

conducted to ascertain the extent of biodeterioration. The results from the above

studies are presented and discussed in detail, in the next chapter (i.e. Chapter 4).

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Table 3.1 Physical and chemical characteristics of potable water (IS: 10500-2003)

Sl.No. Characteristics Value 1. Turbidity (Units: JTU scale) 2.5 2. Colour (units: platinum-cobalt

scale) 5.0

3. Taste and odour Unobjectionable 4. pH 7.0 to 8.5 5 Total dissolved solids (TDS) 500 6 Total hardness (CaCO3) 200 7 Chlorides (Cl) 200 8 Sulphates (mg/l) 200 9 Fluorides (as F) 1.0

10 Nitrates (as NO3) 45 11 Calcium (as Ca) 75 12 Magnesium (as Mg) 30 13 Iron (as Fe) 0.1 14 Manganese (as Mn) 0.05

Note: Values in Sl.No (5) to (14) are in mg/l

Table 3.2 Characteristics of sea water (Wild et al., 1991)

Sl.No. Characteristics Value 1 Calcium 410 2 Chloride 19,700 3 Potassium 390 4 Bromide 65 5 Iron < 0.02 6 Silica 0.04 - 8.0 7 Sodium 1,900 8 Fluoride 1.4 9 Strontium 13 10 Bicarbonate 152 11 Magnesium 1,310 12 Sulphate 2,740 13 Barium 0.05 14 Nitrate < 0.7 15 Manganese < 0.01 16 TDS 35,000 17 pH 8.1 18 Salinity 3.5%

Note: Values in Sl.No (1) to (16) are in mg/l

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Table 3.3 Grading of concrete using pulse velocity

Pulse Velocity (km/sec)

Concrete Quality (Grading)

Above 4.5 Excellent

3.5 to 4.5 Good

3.0 to 3.5 Medium

Below 3.0 Doubtful

Table 3.4 Grading of concrete using rebound number

Average Rebound Number Quality of Concrete

>40 Very good hard layer

30 to 40 Good layer

20 to 30 Fair

< 20 Poor concrete

0 Delaminated

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Fig. 3.1 Beach profile showing low tide and high tide

Fig. 3.2 Structure of a seaweed/ marine algae

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3.3 (a) Pondicherry port

3.3 (b) Ariyankuppam, Pondicherry

3.3 (c) Cuddalore port

78

3.3 (d) Kalpakkam

3.3 (e) Kovalam beach

3.3 (f) Tharangampadi, near Karaikal

Figs. 3.3 (a – f) Photographic views of algal colonization

in various places

79

Figs. 3.4 Photographic views of algal colonization during various seasons of the

year along Pondicherry coast

80

Fig. 3.5 Location map of the study area

Note: Locations are

1. Chennai (Madras) Port

2. Kalpakkam

3. Pondicherry Port

4. Ariyankuppam, Pondicherry

5. Cuddalore Port

6. Karaikal Port

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3.6 (a) At concrete age of 28 days

3.6 (b) At concrete age of 30 days

3.6 (c) At concrete age of 35 days

Figs. 3.6 (a – c) Photographic view showing algal extinction within a few days of initiating colonization on a fresh concrete

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Fig. 3.7 Overview of experimental scheme adopted

M20 and M25 grade concrete cubes are cast and allowed to cure for 28 days

M20 and M25 grade concrete cubes are kept immersed in potable water

M20 and M25 grade concrete cubes are colonized with algae under field condition

M20 and M25 grade concrete cubes are colonized with algae under laboratory condition

M20 and M25 grade concrete cubes are kept immersed in sea water

Sophisticated Analytical Techniques

Phycochemcial Investigations

Macro-level studies

SEM

EDAX

FTIR

XRD

TGA

Identification of marine algae

Identification of fatty acids secreted by metabolic activity of algae

Visual examinations

NDT on algal colonized concretes

Compressive strength test

Qualitative and Quantitative studies (3-24 months)

Mechanism of biodeterioration

Total effect on the substrate due to biodeterioration

83

Fig. 3.8 (a) Front view of the humidity chamber

Fig. 3.8 (b) Outer view showing the components

Fig. 3.8 (c) Inner view showing the components

Figs. 3.8 (a – c) Photographic view of the humidity chamber used for colonization of algae in the laboratory

84

(a) (b)

(c) (d)

(e) (f)

Figs. 3.9 (a – f) Photographic views showing the various stages of algal colonization on concrete cubes in the laboratory condition

85

Fig. 3.10 -Photographic view of concrete cubes kept in field

Condition

Fig. 3.11 (a) Development of algal stains

Fig. 3.11 (b) Germination of zoospores

on concrete Fig. 3.11 (c) Algal growth in field

condition Figs. 3.11 (a – c) Photographic views showing the algal colonized on concrete cubes in

field condition

A

A