7/21/2019 08chapter4-4.pdf(1) http://slidepdf.com/reader/full/08chapter4-4pdf1 1/48 4.4-1 4.4 RECYCLED CONCRETE (RC) AGGREGATE 4.4.1 Introduction The coarse aggregates chosen for this research project included: •14/10mm RC Aggregate manufactured by Recycling Industries Pty Ltd at the Laverton North recycling plant and; •14/10mm N (natural) Aggregate, a locally available basalt supplied by Boral Resources Pty Ltd and used as a control aggregate Both aggregates are commercially available products. The Class1, 14/10mm RC Aggregate is a ready to use concrete aggregate of a fixed grading. However, in the case of the 14/10mm N Aggregate, in order to keep the grading as a constant parameter in both aggregate, two single size aggregates; the 14mm and 10mm basalt aggregate were mixed to a required particle size distribution. In standard industry operations, similar or any other desired grading, is produced from a single sized aggregate, which is dozed and combined in the concrete batching process. Figure 4.4.1 presents the 14/10mm RC Aggregate in a stockpile at the Laverton North recycling plant. Figure 4.4.1 Stockpile of RC Aggregate As a general rule, the suitability of coarse aggregate as a material for concrete production is decided mainly due to its physical and mechanical properties. The Australian Standard AS2758.1-1998 ‘Aggregates and rock for engineering purposes, Part 1: Concrete aggregates’ specifies these properties and refers to testing procedures 800mm
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The coarse aggregates chosen for this research project included:
• 14/10mm RC Aggregate manufactured by Recycling Industries Pty Ltd at the
Laverton North recycling plant and;
• 14/10mm N (natural) Aggregate, a locally available basalt supplied by Boral
Resources Pty Ltd and used as a control aggregate
Both aggregates are commercially available products. The Class1, 14/10mm RC
Aggregate is a ready to use concrete aggregate of a fixed grading. However, in the caseof the 14/10mm N Aggregate, in order to keep the grading as a constant parameter in
both aggregate, two single size aggregates; the 14mm and 10mm basalt aggregate were
mixed to a required particle size distribution. In standard industry operations, similar or
any other desired grading, is produced from a single sized aggregate, which is dozed
and combined in the concrete batching process. Figure 4.4.1 presents the 14/10mm RC
Aggregate in a stockpile at the Laverton North recycling plant.
Figure 4.4.1 Stockpile of RC Aggregate
As a general rule, the suitability of coarse aggregate as a material for concrete
production is decided mainly due to its physical and mechanical properties. The
Australian Standard AS2758.1-1998 ‘Aggregates and rock for engineering purposes,Part 1: Concrete aggregates’ specifies these properties and refers to testing procedures
for a specific property. Thorough knowledge of the basic engineering properties of
coarse aggregate is fundamental, as it allows concrete technologists to design concrete
mixes.
This section of the report presents outcomes of the characterisation of selected recycled
concrete aggregate and differentiates the aggregate from comparable natural coarse
aggregate in a range of properties including: composition of aggregate particles, content
of foreign materials, particle and bulk densities, water absorption, and porosity. In
addition, the re-cementing potential of RC Aggregate is reported.
4.4.2 Composition – Cement Paste Residue Content
Pertinent to its composition, commonly used coarse aggregate (including basalt) used in
the production of concrete can be seen as a homogeneous material. However, the
composition of RC Aggregate is not so uniform, as the feedstock material used in its
production is already a composite in nature; cement paste and aggregate, and it may
consist of other waste.
To optimise the effectiveness of waste recovery and to minimise the variations of
recycled products, the concrete waste is separated at source from other C&D waste, and,
preferably delivered to recycling plants with minimal content of other waste materials.
The bulk of the concrete waste is crushed into smaller particles of specified size and in
the process, during particular stages, electromagnets or manual pickers remove any
foreign material including steel reinforcement. In general, variability of the raw
material does not affect the aggregate’s grading, however, the content of foreign
material in recycling products (RC Aggregate) depends strongly on the degree of
contamination of the feedstock material, and on the effectiveness of segregation of those
materials at various stages of the production process.
Uncontaminated, 14/10mm RC Aggregate consists of some particles of natural
aggregate (fine and coarse fraction), of particles of natural aggregate coated with some
cement paste residue (cpr), and of particles of pure cpr. The size of these particlesranges from sporadic 19mm aggregate pieces, though majority of them are of 14 and
The Australian Standard AS 2758.1-1998 ‘Part 1. Concrete aggregates’ sets the content
limits for some impurities in aggregate, which include sugars, soluble salts, organic
mater and clay minerals. The content limits in both fine and coarse aggregate set
control measures to eliminate any adverse effects of these impurities on the strength,
abrasion resistance, surface finish and durability of concrete. Organic matter, sugar, or
any other carbohydrates influence setting time by delaying or suspending the set of
cement in concrete. A higher than permitted level of soluble salts in aggregate can
cause disintegration of concrete and corrosion of steel reinforcement, whereas, clay
minerals in aggregate cause strength reduction and volume changes.
The content of impurities in alternative concrete aggregate also has its limitations.
Commercial specifications for 14/10mm RC Aggregate set the maximum content of all
foreign materials of 1% by mass in Class 1A, and 2% in Class 1B aggregate. The
specifications do not take into account soluble salts or sugar content, but rather high
density materials such as steel reinforcement; and low density materials such as wood
and other organic matter. Figure 4.4.5 presents a breakdown by standard particle sizesof a sample of the 14/10mm RC Aggregate into foreign materials and uncontaminated
aggregate.
Figure 4.4.5 Sample of 14/10mm RC Aggregate with segregated foreign materials
The amount of foreign materials in the 14/10mm RC Aggregate was determined from a
number of representative samples weighing 5kg that were randomly selected from
monthly batches of the aggregate. The RC Aggregate was dried in a laboratory oven at
a temperature of 103 ±2°C, sieved, then any organic and inorganic materials other than
clean pieces of the aggregate were isolated and their mass determined. Figure 4.4.6
presents the average percentages of all foreign materials in Class1, 14/10mm RC
Aggregate determined over a period of three years.
1.23
1.51
0.81
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
Jan-Dec 1999 Jan-Dec 2000 Jan-Aug 2001
Period of time
P e r c e n t a g e b y w e i g h t
Figure 4.4.6 Average content of foreign materials in 14/10mm RC Aggregate
The results show that the average total content of all physical contaminants in RC
Aggregate range between 0.81% and 1.51% with a few extreme cases where the highest
content of 5% in sample RCA_08_00 was noted. In general, the total level of foreign
material in the aggregate is below the limit indicated in the manufacturer’sspecification.
Furthermore, the amount of low density particles within RC Aggregate was determined.
After the segregation of uncontaminated particles and any foreign materials in RC
Aggregate, the aggregate was immersed in water to identify low density particles. The
low density particles were then dried and weighed. The test results show an average
content of 0.025%, which is considered as insignificant. It was observed that inmajority of tested aggregate, low density particles were not present. Figure 4.4.7
presents the average content of particles lighter that 1,000kg/m3 in 14/10mm RC
Aggregate measured over a period of three years.
0.04
0.01
0.03
0.00
0.01
0.01
0.02
0.02
0.03
0.03
0.04
0.04
0.05
0.05
Jan-Dec 1999 Jan-Dec 2000 Jan-Aug 2001
Period of time
P e r c e n t a g e b y w e i g h t
Figure 4.4.7 Average content of low density (<1,000kg/m3) particles in 14/10mm
RC Aggregate
The number and amount of different types of foreign materials in RC Aggregate ishighly dependent on the concrete waste stream, which is instigated by the choice of
demolition method and whether significant separation of concrete waste from other
C&D debris is employed. The content of foreign materials also depends on the
handling of feedstock at the recycling plant and on the effectiveness of their removal
during the crushing process.
The production of 14/10mm RC Aggregate at the Laverton North recycling plant isgoverned by quality assured (QA) procedures. The manufacturer makes every effort to
minimise the amount of different categories of foreign materials in the aggregate,
especially those which contribute to volume instability such as; bricks, gypsum, wood,
clay lumps, and plate glass. Figure 4.4.8 presents the average number of different types
Figure 4.4.12 Foreign materials in 14/10mm RC Aggregate
An investigation into the composition and presence of physical contaminants revealed
that the presence of cement paste residue and foreign materials is intrinsic to RC
Aggregate. It also became apparent that although both the cpr and physical
contaminants are kept in a well defined range, they have a significant bearing on the
basic engineering properties of RC Aggregate.
The total cement paste residue content in the 14/10mm RC Aggregate was found to be
27%, which can be affixed to pieces of natural aggregate or be found in pure cement
paste form.
The foreign material content in 14/10mm RC Aggregate is on average 1.18%. The most
frequently present foreign materials in the aggregate include brick and wood particles.During the testing period it was observed that the number and amount of physical
contaminants declined; a result of improvements in the production process of the
aggregate.
4.4.4 Cement Content and Elemental Composition of RC Aggregate Fines
A grading analysis of 14/10mm RC Aggregate showed that the content of very fine
particles is quite considerable, although consistent with the limits set by the
the fines, it can be concluded that a 2% content of particles smaller than 75μm in
14/10mm RC Aggregate, could have an equivalent cementing potential of
approximately 0.57% of GB cement.
More extensive studies using XRD and methodology similar to that described in this
section are currently being undertaken to further investigate the influence of cement
paste residue on chemical bonding in concrete made from RC Aggregate.
The Scanning Electron Microscopy was used to investigate the differences in elemental
(oxide) composition between natural and RC Aggregate, and to analyse mechanically
induced cracks in recycled aggregate.
Examination of the elemental composition aimed at supplementing the study of the re-
cementing potential of the fines and of cement paste residue of 14/10mm RC
Aggregate. Representative powder samples, mainly derived from the aggregate’s fines
(some powder samples were obtained from crushed cpr) and solid samples purposely
prepared or cut from RA Concrete were used. Areas as large as possible of powder and
solid samples were analysed using Energy Dispersive X-ray facilities to determineelemental (oxide) composition. Figure 4.4.14 presents SEM powder samples of RC
Aggregate and sample holders, whereas Figure 4.4.15 presents a Backscatter electron
(BSE) image of RC Aggregate fines.
Figure 4.4.14 Powder samples of RA Concrete – SEM examination
An analysis of BSE images reveals that approximately 95% of GB cement particles are
significantly smaller than 75µm, and that the predominant particle size is approximately15µm. The slightly lighter colour of the cement particles seen on the BSE images is
indicative of calcareous elements. The ED X-ray analysis plot of the GB shows that
approximately 75% of the total content of the cement is calcium, in one of its oxide
forms.
Solid samples of RC Aggregate were analysed using the same procedures and testing
environment. Figure 4.4.21 shows a typical example of a Backscatter Electron image of
A relationship between SSD particle density and cement paste content was also
investigated. Figure 4.4.24 presents a linear correlation between SSD and cpr content.
2.44 2.44
2.55 2 .44 2.45 2.49 2.44 2.47 2.46 2.40 2.38
2.47
y = -0.004x + 2.4788
0.00
5.00
10.00
15.00
20.00
25.00
R C A
_ 0 8 & 0 9 & 1 0
_ 9 9
R C A
_ 0 5 & 0 6 & 0 7
_ 0 1
R C A
_ 0 2 & 0 3 & 0 4
_ 0 1
R C A
_ 0 5 & 0 6 & 0 7
_ 0 0
R C A
_ 1 1 & 1 2 & 0 1
_ 0 1
R C A
_ 0 8 & 0 9 & 1 0
_ 0 0
R C A
_ 0 2 & 0 3 & 0 4
_ 0 0
R C A
_ 0 5 & 0 6 & 0 7
_ 9 9
R C A
_ 0 2 & 0 3 & 0 4
_ 9 9
R C A
_ 1 1 & 1 2 & 0 1
_ 0 0
R C A
_ 0 8 & 0 9 & 1 0
_ 0 1
R C A
_ 0 1
_ 9 9
c p r [ % ] & s a t u r a t e d s u r f a c e d r y d e n s i t y [ t / m 3 ]
cpr [%]
SSD [t/m3]
Linear (cpr [%])
Linear (SSD [t/m3])
Figure 4.4.24 Relationship between cpr content and saturated surface dry density
of 14/10mm RC Aggregate
It is evident that the SSD particle density of 14/10mm RC Aggregate is dependent onthe content of cement paste residue as would be expected. An increased amount of cpr
in the aggregate results in a lower SSD particle density.
2.15
2.20
2.25
2.30
2.35
2.40
2.45
2.50
1 2 3 4 5 6 7 8 9 10 11 12
Sample group
D r y d e n s i t y [ t / m 3 ]
Figure 4.4.25 Dry particle density of 14/10mm RC Aggregate
Figure 4.4.30 Particle size distribution of 14/10mm RC Aggregate – average of
1999 – 2003 samples
Control samples were prepared from single-size aggregates; 10mm and 14mm. Firstly,
volumes of RC Aggregate of a particular size were measured. Test portions of naturalaggregates were determined using identical volumes of comparable RC Aggregate.
This was consistent with the approach that is taken when concrete mixes are designed;
however, it also resulted in a very small deviation in the grading of the natural aggregate
compared with those of the 14/10mm RC Aggregate. The difference in the particle size
distribution of the two aggregates was deemed as negligible, therefore not requiring any
adjustments. Table 4.4.3 presents the grading of some of the basalt samples used as a
control aggregate.
Table 4.4.3 Particle size distribution of 14/10 mm Natural Aggregate – percentage
Figure 4.4.34 Example of powder (<150μm) samples of neat cement pastes of
various cement/water ratios (0.2w/c, 0.4w/c and 0.8w/c)
Figure 4.4.35 Example of solid sample of cement paste residue of RC Aggregate
obtained from concrete of known w/c ration of 0.4
A representative number of cement paste residue test portions of the 14/10mm RC
Aggregate were selected. The sample suite of the cpr collected and examined
corresponds to a testing period of four (4) years. The test portions were selected from
aggregate samples that were mechanically broken at the compositional examination of
14/10mm RC Aggregate. According to a degree of possible carbonation, the cement
paste residues were classified into three categories; LOW (slightly weathered cpr, and
of or corresponding to, a good quality, very low w/c ratio of approximately 0.2 or to
natural aggregate), MODERATELY (reasonably weathered cpr, and of or
corresponding to, an average quality cement paste w/c ratios of approximately 0.4 to
0.6) and HIGHLY (distinctly weathered cpr, and of, or corresponding to a poor qualityof cement paste, of w/c ration of approximately 0.8). Tables 4.4.4 and 4.4.5 present the
BET porosity is expressed in terms of total pore volume, pore size distribution, poresurface area, and pore diameter. Figure 4.4.36 shows an adsorption isotherm of the
reference 0.4 w/c ratio paste. The isotherm is characteristic of porous solids and the
hysteresis loop created by the adsorption and desorption branches indicate a uniform
distribution of pores of different sizes in the pore size range ranging between 17Å and
3μm. A similar pattern and shape of isotherms in all samples of the cement paste
residue have been observed. This confirms that the microstructure of cement paste
consists of a reasonably evenly distributed network of pores as was expected.
Figure 4.4.38 presents an example of an isotherm of one of the cement paste residue
samples, which has been classified as highly weathered.
HIGHLY weathered sample of cpr (s_147) , adsorption isotherm
0
5
10
15
20
25
30
35
40
45
50
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Relative pressure [p/po]
V o l u m e a d s o r b e d [ c c / g ]
Figure 4.4.38 BET isotherm of HIGHLY weathered cpr (s_147)
The highly weathered cement paste residues of 14/10mm RC Aggregate have pore size
distribution spread relatively evenly over the whole porosity range measured by BET
nitrogen adsorption. It could also be concluded that the shape of the isotherm is similar
to the isotherms produced by other referenced samples or of the cpr samples.
Figure 4.4.39 shows the BET isotherm of one of the moderately weathered cement pasteresidue samples, which has a porosity characteristic of standard concrete with a design
water/cement ratio of between 0.4 and 0.6. Prior to the BET nitrogen adsorption
examination, this sample (s_229) was subjected to a non-destructive SANS porosity
Test results of the BET nitrogen adsorption examination of the total porosity of highly
weathered cpr of 14/10mm RC Aggregate defined a range of porosity from 7.3% to
27.9%. The total porosity in majority of the samples is below the reference porosity of
17.5%. The average total porosity of significantly weathered cpr is 15.4%.
The total porosity reference standard established for moderately weathered cpr was
8.1%. Figure 4.4.42 presents results of the BET examination of total porosity of
moderately weathered cpr of the 14/10mm RC Aggregate.
8.1
4.2
7.1
8.2
6.8
4.8
8.4
6.5
5.75.55.55.4
5.34.7
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
c o n t r o l 0 . 4 c p *
[ s_
2 1 4 ]
M W
c p r [ s
_ 1 7 2 ]
M W
c p r [ s
_ 2 2 5 ]
M W
c p r [ s
_ 2 2 7 ]
M W
c p r [ s
_ 2 1 3 ]
M W
c p r [ s
_ 2 3 0 ]
r c a_ 0 4
_ 1 *
[ s_
2 0 7 ]
M W
c p r [ s
_ 2 3 2 ]
M W
c p r [ s
_ 1 4 8 ]
r c a_ 0 4
_ 3 *
[ s_
2 0 8 ]
M W
c p r [ s
_ 1 4 6 ]
r c a_ 0 4
_ 2 *
[ s_
2 1 6 ]
M W
c p r [ s
_ 2 2 9 ]
r c a_ 0 4
_ 4 *
[ s_
2 0 9 ]
B E T p o r o s i t y [ % ]
Figure 4.4.42 BET porosity of MODERATELY weathered cement paste residue of
14/10mm RC Aggregate
The results indicate that the majority of samples have a total porosity lower than the
reference porosity of 8.1% and that the average total porosity of moderately weathered
cpr is 6%.
In order to assume a classification system, cement pastes that required a much higher
energy input in segregating cpr from natural aggregate were classified as slightly
weathered even though the weathering was not measured . Some of the samples (s_145,s_171, s_173) also had pieces of natural aggregate, which were difficult to isolate. A
porosity standard of 0.9% was established for the LOW weathered cpr (sample s_174).
Figure 4.4.43 presents total porosity of slightly weathered cement paste residues.
0.9
2.31.9
1.4
2.9 3.0
3.5
5.85.7
3.93.73.7
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
c o n t r o l c p + n a
[ s_
1 7 4 ]
c o n t r o l c p + n a
[ s_
1 4 5 ]
c o n t r o l c p + n a
[ s_
1 7 1 ]
L W
c p r [ s
_ 1 7 3 ]
L W
c p r [ s
_ 2 0 6 ]
L W
c p r [ s
_ 1 4 3 ]
L W
c p r [ s
_ 2 0 3 ]
L W
c p r [ s
_ 2 0 5 ]
L W
c p r [ s
_ 2 2 4 ]
L W
c p r [ s
_ 2 0 4 ]
L W
c p r [ s
_ 2 0 2 ]
L W
c p r [ s
_ 2 2 6 ]
B E T p o r o s i t y [ % ]
Figure 4.4.43 BET porosity of slightly (LOW) weathered cement paste residue of14/10mm RC Aggregate
Test results show that the total porosity in all of the cement paste residue samples
exceeded the reference porosity. The average BET porosity in slightly weathered cpr of
14/10mm RC Aggregate is 4% and of cement paste residue containing some natural
aggregate is 1.87%.
Furthermore, the pore volume was analysed in terms of the total pore volume (BETrange from 17Å to 3μm) and volume of micropores. All samples of the cement paste
residue of 14/10mm RC Aggregate were categorised as ‘old cpr’ and an average of all
the data is presented in the following figures. Figure 4.4.44 shows an average total pore
volume in cpr and compares it against the three reference standards (e.g. ‘0.2w/c cp’ -
0.2 water/cement ratio new cement paste)
An average total volume of pores in the cement paste residue of 0.036cm
3
/g ischaracteristic of slightly weathered pastes. A relatively low total volume of pores in the
BET porosity range (17Å to 3μm) could indicate that pores in weathered cpr are bigger
than 3μm, and that the volume of such pores was not measured.
0.032
0.058
0.093
0.036
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
old cpr 0.2w/c cp 0.4w/c cp 0.8w/c cp
Sample group
T o t a l p o r e v o l u m e [ c m
3 / g ]
Figure 4.4.44 BET - Total pore volume of cement paste residue (old cpr) -
comparison with porosity standards
However, the volume of micropores is higher than those of the reference standards,
which indicates that through the weathering process or other in-service mechanisms,minute pores are created or access to already existing pores is made possible. Figure
4.4.45 presents an average volume of micropores in the cpr of 14/10mm RC Aggregate.
0.00023
0.00087
0.00136
0.00200
0
0.0005
0.001
0.0015
0.002
0.0025
old cpr 0.2w/c cp 0.4w/c cp 0.8w/c cp
Sample group
M i c r o p o r e s v o l u m e [ c m
3 / g ]
Figure 4.4.45 BET – Micro-pore volume of cement paste residue (old cpr) –
content, content and re-cementing qualities of fines, particle size distribution, particle
and bulk density, water absorption, and porosity.
The results indicate that the selected 14/10mm RC Aggregate has a specific set of well
defined unique properties. Some of the physical properties of the aggregate are specificto the material. For example, content of cement paste residue and content of various
remnants of other waste material in the aggregate are intrinsic to the waste material used
in production, and to RC Aggregate.
A relatively high content of fine particles smaller than 75μm in 14/10mm RC Aggregate
is another unique property of the material. The fines appear to have some re-cementing
potential, which can contribute to hydration of cement in concrete made from RC
Aggregate. Another property of the aggregate that has potential to be beneficial from a
concrete technology view point is its shape.
However, some of the aggregate’s properties including inconsistent water absorption
and higher porosity have to be closely monitored and controlled if the aggregate is used
in concrete.
Table 4.4.7 presents a summary of the basic engineering properties of 14/10mm RC
Aggregate.
Table 4.4.7 Average engineering properties of 14/10mm RC Aggregate – summary
Property Unit 14/10mm RC
Aggregate
Reference /
basalt
Cement paste residue content % 27 0Foreign material content % 1.18 0Fines (<75μm) content % 2 0Re-cementing potential % of GB 0.5 0Particle density (SSD) kg/m3 2,450 2,750Bulk density (compacted) kg/m3 1,420 1,700Water absorption % 4.67 0.5
Total porosity (range 17Å - 3μm) % 7.22 0.86Total pore volume(range 17Å - 3μm) cm3/g 0.036 0.32Total volume of micropores cm3/g 0.002 0.00023Total surface area(range 17Å - 3μm) m2/g 10.73 6.41Total surface area of micropores m2/g 2.79 0.4Pore average diameter (range 17Å - 3μm) Å 142.2 200Particle size distribution 14/10mm 14/10mmElemental composition Calcium rich Silica rich
The test results generated at this stage of the experimental program defined the basic
engineering properties of 14/10mm RC Aggregate. The majority of the data wassubsequently used in other stages of the experimental and developmental program of
this research project. The next section reports on an examination of concrete made from
4.4.4 Cement Content and Elemental Composition of RC Aggregate Fines ...114.4.5 Particle Density .......................................................................................194.4.6 Bulk Density ...........................................................................................234.4.7 Particle Size Distribution ........................................................................244.4.8 Water Absorption....................................................................................274.4.9 Porosity ...................................................................................................294.4.10 Discussion of the Results ........................................................................44
Figure 4.4.1 Stockpile of RC Aggregate...........................................................................1Figure 4.4.2 Particles of RC Aggregate (A – cement paste residue only, B and C –
natural aggregate coated with cpr) ............................................................................3Figure 4.4.3 Relative composition of 14/10mm RC Aggregate (sample
RCA_11_00_s1&s2).................................................................................................3Figure 4.4.4 Composition of 14/10mm RC Aggregate (after additional segregation)......4Figure 4.4.5 Sample of 14/10mm RC Aggregate with segregated foreign materials .......5Figure 4.4.6 Average content of foreign materials in 14/10mm RC Aggregate...............6Figure 4.4.7 Average content of low density (<1,000kg/m3) particles in 14/10mm RC
Aggregate..................................................................................................................7Figure 4.4.8 Average number of foreign materials in 14/10mm RC Aggregate...............8Figure 4.4.9 Occurrence frequency of foreign materials in 14/10mm RC Aggregate ......9Figure 4.4.10 Average weight [g] of various foreign materials per typical, 4kg samples
of 14/10mm RC Aggregate .......................................................................................9Figure 4.4.11 Examples of foreign materials in 14/10mm RC Aggregate......................10Figure 4.4.12 Foreign materials in 14/10mm RC Aggregate..........................................11Figure 4.4.13 Equivalent GB cement content in 14/10mm RC Aggregate.....................12Figure 4.4.14 Powder samples of RA Concrete – SEM examination.............................13Figure 4.4.15 BSE image of RC Aggregate fines ...........................................................14Figure 4.4.16 ED X-ray analysis of RC Aggregate fines................................................14Figure 4.4.17 BSE image of natural aggregate (basalt) fines .........................................15Figure 4.4.18 ED X-ray analysis of natural aggregate (basalt) fines ..............................16Figure 4.4.19 BSE image of GB cement.........................................................................17
Figure 4.4.20 ED X-ray analysis of GB cement .............................................................17Figure 4.4.21 BSE image of cement paste residue .........................................................18Figure 4.5.22 Elemental composition of natural and 14/10mm RC Aggregates -
summary..................................................................................................................18Figure 4.4.23 Saturated surface dry density of 14/10mm RC Aggregate .......................19Figure 4.4.24 Relationship between cpr content and saturated surface dry density of
14/10mm RC Aggregate .........................................................................................20Figure 4.4.25 Dry particle density of 14/10mm RC Aggregate......................................20Figure 4.4.26 Relationship between cpr content and dry particle density in 14/10mm RC
Aggregate................................................................................................................21Figure 4.4.27 Relationship between cpr content and apparent density in 14/10mm RC
Aggregate................................................................................................................22Figure 4.4.28 Bulk density of the 14/10mm natural and RC Aggregates.......................24
Figure 4.4.29 Particles of 14/10mm RC Aggregate retained on 13.2mm, 9.5mm, 6.7mm,4.75mm, 2.36mm and 75μm sieves (from right to left).........................................25
Figure 4.4.30 Particle size distribution of 14/10mm RC Aggregate – average of 1999 –2003 samples...........................................................................................................26
Figure 4.4.31 Comparison of particle size distribution of natural aggregate and14/10mm RC Aggregate .........................................................................................27
Figure 4.4.32 Water absorption of 14/10mm RC Aggregate measured by the weigh-in-water method...........................................................................................................28
Figure 4.4.33 Relationship between cement paste residue (cpr) content and waterabsorption in 14/10mm RC Aggregate ...................................................................29
Figure 4.4.34 Example of powder (<150μm) samples of neat cement pastes of variouscement/water ratios (0.2w/c, 0.4w/c and 0.8w/c) ...................................................30
Figure 4.4.35 Example of solid sample of cement paste residue of RC Aggregateobtained from concrete of known w/c ration of 0.4 ................................................30
Figure 4.4.37 BET isotherm – 0.8w/c ratio, neat cement paste ......................................32Figure 4.4.38 BET isotherm of HIGHLY weathered cpr (s_147) ..................................33Figure 4.4.39 Example of MODERATELY weathered cpr (BET sample s_229)..........34Figure 4.4.40 Example of LOW weathered cpr (BET sample s_226)............................34Figure 4.4.41 BET porosity of HIGHLY weathered cement paste residue of 14/10mm
RC Aggregate..........................................................................................................35Figure 4.4.42 BET porosity of MODERATELY weathered cement paste residue of
14/10mm RC Aggregate .........................................................................................36Figure 4.4.43 BET porosity of slightly (LOW) weathered cement paste residue of
14/10mm RC Aggregate .........................................................................................37Figure 4.4.44 BET - Total pore volume of cement paste residue (old cpr) - comparison
with porosity standards ...........................................................................................38Figure 4.4.45 BET – Micro-pore volume of cement paste residue (old cpr) – comparison
with porosity standards ...........................................................................................38Figure 4.4.46 BET – Total pore surface area of cement paste residue (old cpr) –
comparison with porosity standards........................................................................39Figure 4.4.47 BET – Micropore surface area of cement paste residue (old cpr) –
comparison with porosity standards........................................................................40Figure 4.4.48 BET – Average pore diameter of pores in cement paste residue (old cpr) –
comparison with porosity standards........................................................................40Figure 4.4.49 BET porosity of HIGHLY weathered RC Aggregate...............................41
Figure 4.4.50 BET porosity of MODERATLY weathered RC Aggregate.....................42Figure 4.4.51 BET porosity of LOW weathered RC Aggregate.....................................43
Table 4.4.1 Particle density of 14/10mm RC Aggregate – results summary..................22Table 4.4.2 Particle size distribution of 14/10 mm RC Aggregate – percentage passing
.................................................................................................................................25Table 4.4.3 Particle size distribution of 14/10 mm Natural Aggregate – percentage
passing.....................................................................................................................26Table 4.4.4 RC Aggregate samples examined by the BET nitrogen adsorption.............31Table 4.4.5 RC Aggregate samples examined by the BET nitrogen adsorption –
classification by degree of weathering....................................................................31Table 4.4.6 Porosity of 14/10mm RC Aggregate – summary results .............................44Table 4.4.7 Average engineering properties of 14/10mm RC Aggregate – summary....45