Article 2010 for wiki

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HIGH-ENERGY MECHANICAL ACTIVATION
OF CONCRETE MIXTURE
Vladlen Fridman
vfrid38@gmail.com
© Copyright 2010 by V.Fridman
ABSTRACT
The main principles of mechanical activation of mortars or mortar component of concrete using
the method of high-energy mixing (HEM) are presented. Among them are: the use of impeller
with minimal turbulence to achieve the highest level energy absorption by the mixture; the use of
sand to provide dissipation of energy and high shear conditions on the surface of cement
particles; the optimal combination of the following factors such as the rotor’s velocity, the
amount of specific energy, and geometrical parameters of the mixer. HEM increases the surface
activity of solid particles, which results in a higher volume of the water interacting with cement
to form the C-S-H gel. Thus, the initial process of cement hydration in films of the water layer 1-
2 nanometer thick spreads out over the entire volume of the cement - water matrix. HEM is an
effective way for industrial application nanotechnology of concrete. Among the achievements
are: accelerated final setting and an increase in early strength, even at low temperatures and less
than 0o
C, as well as the possibility of a 50% reduction in cement quantity with substitution by fly
ash, significantly decreasing energy consumption.
Keywords: acceleration hydration, early strength, syneresis, C-S-H gel, nanotechnology, energy
consumption, fly ash, penetration resistance, setting time, activation.
INTRODUCTION
The use of high levels of mechanical energy both before and during mixing is intended to
intensify cement hydration, thus increasing strength within the required period of time. Excess of
strength would enable to reduce cement quantity and to replace it by a finely dispersed material
that is less energy consuming, such as fly ash, well known to be a pozzolanic admixture.
The present study is not the first one to address this issue. Lindström and Westerberg [1] achieve
excess strength by means of dry- and wet-grinding cement in the so-called Sala Agitated Mill,
thereby significantly reducing the size of particles. They point to a linear correlation between
the amount of absorbed energy per 1 ton of cement and the increase in strength of concrete, the
latter reaching 18% in 3 days and 7.5% in 28 days (data calculations based on Fig. 2 of their
study). This noticeable effect weakens in the later periods of cement hydration.
K.-B. Park et al. [2] achieved a 10% increase in strength as a result of preliminary activation of
dry mixes in a spout-fluid bed lab-scale mixer. This process leads to the destruction of the
floccules formed by particles due to the turbulent flow into the inclined pipe and the impacts of

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particles on the plate, located at the output from the pipe. The dry mixes consisted of cement and
sand with ratios of 1: 2 and 1: 3.2; an alternate method combined the same ratios with a ternary
blend binder containing cement, fly ash, and micro silica proportioned 74:20:6. The authors
underline an increase in flexural strength and note an improvement in rheological properties in
mortars prepared with the above-mentioned dry mixes. However, the level of energy impact here
is lower than that presented by L & W [1], where the activation was not only accompanied by the
destruction of cement floccules, but also caused a significant diminution of the actual cement
particles.
R. Kumar et al. [3] used mechanical activation of class F fly ash by means of vibratory and
attrition milling, as well as a “jet-milled classified method”. A typical median particle size was
reduced from 36.0 to 5, 4.3 and 2.8 m respectively. This allowed for an increase in fly ash
quantity in Pozzolanic Portland Cement (PPC) production from 20% to 50 and 60 %.
Zivko Zekulic, Svetlana Popov et al. [4] mechanically activated the mixture of Portland cement
and 20% fly ash in a vibrating lab mill, equipped with rings for 3 min. They obtained a 57.9%
increase in strength in comparison with the non-activated mix. The strength reached was close to
the strength of cement without fly ash.
All of these methods propose a mechanical action prior to mixing the ingredients with water.
In contrast, H. Hodne et al. [5] carried out activation while cement was being mixed with water,
by means of increasing the rate of shear mixing. They employed three types of propeller blades
of various sizes and raised the speed to up to 12,000 rpm. The energy absorption was determined
to be 5.6 – 7.6 kJ/kg (2.54-3.44 kJ/lb) with a 2o
C (3.6o
F) increase in temperature. The authors
point to a more intense air entrainment into the slurry.
Marshal L. Brown et al. carried out a considerably more powerful process [6]. By utilizing high-
speed shear mixing of cement-water paste (w/c=0.24) pre-liquefied with a superplasticizer (SP),
the authors achieved a 17o
C (30.6o
F) increase in temperature and a boost in viscosity. An
analogous experiment was carried out simultaneously with the use of preliminary ground silica
flour and led to similar results in temperature and viscosity. They have shown that increased
viscosity and heating are caused primarily by friction between solid particles, as well as between
the paste and the walls and blades, and not by cement hydration.
Gary R. Mass [7] proposed a method of premixing the cement-water suspension in a high-speed
mixer before mixing it with fine and coarse aggregates in an ordinary mixer. Given the optimal
combination of speed and mixing time (unspecified in the article), he achieved a 20% strength
increase in 28 days. The author of the present article obtained the same result in a similar in-field
experiment conducted around the same time (in 1989) with the following parameters: w/c = 0.36,
impeller speed = 500 rpm (20 m/sec. or 65.6 ft/s at the end of the blade). Unfortunately, the
indicated strength increase required at least 15 minutes of premix time, which is undesirable.
The above methods represent the few existing examples that partly relate to the process of
activation outlined below. HEM method proposed for the same purpose of an increase in strength
is based on the mechanical activation of mortar, or mortar component of concrete, without
additional grinding.

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RESEARCH SIGNIFICANCE
In developing a more environmentally friendly concrete, the consumption of
Portland cement should be reduced. Manufacturing Portland cement is not only energy
consuming, but is also responsible for large emissions of CO2 [8]. Fly ash is recommended as a
partial substitute for cement. Class F fly ash is not hydraulically active, i.e. it does not have
binding properties, only pozzolanic ones. It will be demonstrated below how an impulse of
energy applied during a relatively short period of mixing time (2-4 min.) could successfully
activate cement or a two-component binder. The HEM technology makes it possible to reduce
the quantity of cement by up to 50% in the widely used concrete while maintaining the strength
of 35 MPa (5000 psi).
THE ESSENCE OF HIGH-ENERGY MIXING
The previous experiments carried out by the author showed a 20-30% increase in concrete
strength. They involved additional grinding of cement in the ball mill, with increased index of
specific surface from 350 to 550 m2
/kg, (or Blaine fineness from 3500 cm2
/g to 5500 cm2
/g).
This is in accordance with data given by Geoffrey Frohnsdorff [9]. These experiments showed
that flowability was reduced by more than half in the mortars prepared with additionally grinded
cement in ordinary mixers. A tendency for an increase in viscosity was also observed in regular
cement mortars when HEM was used. This is because flowability depends on the amount of
unbound water. To achieve the same level of reduction in flowability, one needs to consider the
following as mixing parameters:
1. The relative volumes of the bowl, rotated blades and the mixture.
2. The amount of consumed energy and velocity of rotation.
3. Turbulence reduction to prevent scattering of mixture.
4. The use of fine aggregate as a dissipater of energy in the mixture. Introducing of sand
may cut the activation time by 60-80% compared to the activation time of a cement-water
suspension with no sand. In fact, the solid particles of sand in high velocity conditions
increase shear stresses on the surface of cement grains, thus promoting their physical and
chemical activity.
The author established the rate of reduction in flowability of activated cement-sand
mortars as the first indicator of the activation level [10]. The frictional heating of the mixture is
the second parameter in HEM to be used to control the process.
Figure 1 depicts a schematic diagram of the lab mixer-activator (2.7 liters / 0.71 gal) in which the
first experiments were conducted. The results that were obtained using this lab mixer provided
the basis for manufacturing industrial mixer–activators capable of producing activated mixture of
up to 350 liters (0.46 cu. Y.). One of them is also shown in Figure 1.

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It was observed that, when applying the same activation time to mixtures of same proportions
and same materials (cement, sand), the specific consumed power and the temperature increase in
the mixture are volume independent.
In this process, the mixture moves horizontally and vertically (Fig.1). The horizontal motion
leads to activation of mixture, while the vertical one provides its circulation. In the prescribed
mixer-activator the velocity of activation was significantly higher than the velocity of
circulation. Therefore, the blades must be sufficiently thick to withstand abrasion, and should be
replaced when necessary.
CIRCULATION
ACTIVATION
Fig. 1 - Schematic diagram of the mixer-activator, and the industrial mixer-activator for
producing activated mortars 140 liters (32 gal.) of the volume.
The temperature increase is usually in the range of 20o
C (36o
F) - 30 o
C (54o
F) after mixing for 2-
4 minutes. This is due to turbulence reduction and the presence of an energy dissipater (sand),
which causes friction to give off heat. In hard mortars with zero initial flowability, the
temperature increase during activation is a more effective indicator. This is why the temperature
of activated mixture is chosen as the basic technological parameter in [11] and [12]. The process
of activation is conducted until temperature reaches 45-50o
C (113F-122o
F) due to frictional
heating [10], at which point an SP (or for expanded mortars, – SP with a gas-forming admixture)
is introduced into the mixture. The gas-forming admixture actively interacts with alkalis of
cement paste leading to the release of hydrogen and heat, consequently provoking an expansion
of the mixture. The mixture sets within a few minutes after expansion as a result of frictional and
exothermic heating.
The consumption of specific net energy in HEM (without accounting for lost energy in the
engine and transmission) depends on mix proportions and physical properties of materials. It
ranged from 22 to 45 kWh/ton of cement, which is significantly lower than in the case of
additional grinding: 60 – 120 kWh/ton of cement [1].

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Plasticizing HEM mortar
The increased viscosity of mortars prepared with additionally grinded cement is caused by
increase in total surface moistening of solid particles. Conversely, in the case of HEM, the same
effect can be explained as follows: the activated surface of solid particles of cement and sand
adsorbs more molecules of water than the non-activated one. The fact of adsorption makes this
process effective; although one should not exclude the possibility of deterioration of weak
substances and abrasion of solid particles. Both of the above processes (additional grinding and
HEM) result in a reduced quantity of unbounded water, which leads to higher viscosity of the
mixture.
Using SP to plasticize activated mortars of high viscosity is a necessary step in HEM technology.
HEM mortars require more SP to achieve the same level of flowability as non-activated ones. At
the same time, the stability of mortars is improved after activation. This useful feature, observed
in activated cement-sand mortars, makes it possible to cast small products such as roofing,
facing, and decorative tiles of any shapes and color, successfully replacing ceramics, which
require enormous expenditure of energy.
Thus, HEM creates favorable conditions for high degree of energy absorption by the mixture of
cement, sand, and water, leading to an increase in viscosity and temperature and requiring the
introduction of a SP. HEM is a type of mechano-chemical process based on an extensive surface
treatment of chemically active ingredients, which accelerates reactions of cement hydration.
EXPERIMENTAL INVESTIGATION
The primary goal of this research was to assess the effect of mechanical activation on the kinetics
of setting and strength increase of concrete and mortars in normal and low temperature
conditions. The experiment was conducted both on mixes that had only cement as a binder and
on those with cement and Class F fly ash.
Materials, mix proportions, and test methods
Materials
White Portland cement Type I, Lehigh Co, PA. Compound composition: C3S-72%, C2S-17%,
C3A-5%, C4AF-1%, Na2O+K2O-0.7%. Chemical composition: CaO-68.14%, SiO2-24.88%,
Al2O3-2.13%, Fe2O3-0.23%, K2O-0.42%, Na2O-0.28%, MgO-1.62%, LOI-1.70%, free Lime-
0.6%. Specific gravity is 3.15 g/cu cm, Blane Fineness 3670 cm2
/g.
Class F Fly Ash – Cayuga AES. Chemical composition: SiO2 – 49.9%, Al2O3 – 25.97%, Fe2O3 –
10.38%, CaO – 2.53%, MgO – 1.01%, TiO2 – 1.28%, Na2O – 1.02%, K2O – 2.54%, LOI –
3.06%; specific gravity – 2.5 g/cu cm, Blane fineness – 3800 cm2
/g.
Neither in conventional mixing nor in HEM did this type of fly ash demonstrate binding
properties, as studies have shown.
Dried fine and coarse aggregate were used. They were stored in room conditions.

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The control tests showed the moisture level of 0.15-0.5% for coarse and 0.20% for fine
aggregate.
“Sand for all purpose” (Quikrete) – Sand 1 and “Windham Sand” (CT) – Sand 2 were used with
Fineness Modulus respectively 2.02 and 2.57, specific Gravity SSD 2.71 g/cm3
(169.18 lbs/ft3
)
and 2.69 g/cm3
(167.93 lbs/ft3
). Specific surface of sands: 49 cm2
/g, and 36.3 cm2
/g
respectively.
Granit from Cherenzia, RI - 9.5-19mm (3/8”-3/4”), specific gravity SSD 2.642 g/cm3
(164.93
lbs/f3
), 1.12 soundness, and limestone from New England Silica, Inc - 5-25mm (1/4”-1”),
specific gravity SSD 2.9 g/cm3
or 181 lbs/ft3
, 4.0 soundness were used as a coarse aggregate for
concrete.
Admixtures:
1. SPECCO W-30, Melamine-formaldehyde-sodium bisulfite copolymer “Melment”, in powder,
meets the requirements of ASTM C-494, Type F.
2. Polycarboxylic Ether “SiKa ViscoCrete 3010”, 50% aqueous solution, density 1.12, high
range water reducer that meets the requirements of ASTM C-494 Type A, F.
3. Polycarboxilate polymer ‘SiKa ViscoCrete 6100, liquid, density 1.02 meets the requirements
of ASTM C-494, Type F.
4. “ADVA-100”, High Range water Reducer, ASTM C-494 Type F. Produced Grace W.R,
5. Non-chloride hardening accelerator – SiKa Rapid-1 meets the requirements of ASTM C 494
Type C.
Admixture quantities are given in percents of cement (or cement plus fly ash) mass, as well as in
kg/m3
and lbs/Y3
for concrete mixture.
Mix proportioning, properties of mixtures
The typical proportions of ingredients, in percents of mass for mortars and mortar component of
concrete in this experiment, are: Cement / Sand / Water = 1:2:0.37-0.38.
With fly ash as a supplemental cementitious material, the proportions were as follows:
Cement / Fly Ash / Sand / Water = 1:1:2:0.37- 0.38.
The quantity of HRWR admixture was higher in HEM mortars in comparison with the
conventional ones (as specified above). The data of concrete mixtures are given in Table 1. All
concrete mixtures were repeated twice: mixtures signed “A” included limestone aggregate, Sand
1 and SP “SiKa WiscoCrete 3010”, mixtures signed “B” had granit aggregate, Sand 2, and SP
“SiKa WiscoCrete 6100”.
Conditions of mixing
The conditions of premixing in the lab process were consistent for all variants: mixing dry
ingredients for 2 min., adding water and wet hand-mixing for about 1-1.5 min. Admixture was
introduced at the end of mixing into the control variant, and at the end of activation for the HEM
variant.

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Energy consumption: for HEM mortar with fly ash: 14.25 - 34.2 Кj / kg (6.5 - 15.5 Kj/lb) of
mixture (mixing time 2.5 – 6.0 min), for HEM mortar without fly ash: 11.5 - 26.7 Kj / kg (5.2 -
12.1 Kj/lb) of mixture (mixing time 2.0 - 4.0 min).
Using a lab mixer-activator, both mortar and mortar component of concrete were produced; the
latter was subsequently mixed manually with the coarse aggregate. In the process of activation,
temperature fluctuation and gross (net) energy consumption were continuously measured.
The experiments were conducted at ambient temperature 20-24o
C (68-75.2F), 50 - 55% relative
humidity; the temperature of the control mixture was 21-23o
C (70-74o
F), and the initial
temperature of HEM mixtures was 35-45o
C (95-113o
F).
Test Methods
Cylinders of 76.2mm (3") in diameter and 152.4 mm (6") in height were cast from the concrete
mixture, and cubes of 50x50x50mm (2”x2”x2”) were cast from mortars. The control specimens
were prepared in the same fashion, only without activation. Curing of specimens was maintained
according to ASTM C-192/C192M-05 “Practice for making and Curing Concrete Test
Specimens in the Laboratory.” To determine the kinetics of initial and final setting for activated
and non-activated mortars, the method of penetration resistance was used according to ASTM C
403/C403M-05 “Time of setting of concrete mixtures by penetration resistance.” Compressive
strength of mortar samples was tested in accordance with “Standard Test Method for
Compressive Strength of Hydraulic Cement Mortars using 50-mm (2-inch) Specimens” ASTM C
109/C 109M-05; concrete samples: ASTM C39/C39M-05 “Standard Test Method for
Compressive Strength of Cylindrical Concrete Specimens”.
Flowability of mortars was determined according to the modified “Standard Test Method for
Flow Consistency of Controlled Low Strength Material (CLSM), ASTM D 6103-04”with a
reduced size of plastic tube - 100 mm (4”) length of 50 mm (2”) in interior diameter.
EXPERIMENTAL RESULTS AND DISCUSSION
Flowability of mortars
The results in flowability of activated and control mortars are shown in Table 2.
In the tests specified below, the quantity of SP was determined so as not to exceed the level at
which signs of bleeding begins to occur. In the activated mixture, that level is much higher than
in the non-activated and depends on the properties of the admixture (Table 2, variants 3, 4, 7, 10,
15). Some of the HEM mortars, prepared with the dosage of SP equal to the control ones,
showed a lower level of flowability (Table 2, variants 2, 6, 9, and 14). The mortars 11, 12, 13
were prepared by gradually reducing the quantity of admixture ADVA-100 (Grace W.R.). These
results illustrate how non-bleeding mixtures were achieved.

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Table 2- Flowability of mortars
Mortar
variant
Variant
of SP
Proportions of
Ingredients
W/C, or
W/(PC+FA)
SP/PC, or
SP/(PC+FA),
%
Flowability
cm/(in)
Notes
1.Control
2. HEM
3. HEM
4. HEM
SiKa
WiscoCrete
3010
PC/SAND
1 : 2
0.37 0.57
0.57
1.4
1.52
9.4 (3 ¾”)
6.0 (2 ¼”)
10cm(4”)
15.5cm(6 ¼”)
No
bleeding
5.Control
6. HEM
7. HEM
SiKa
WiscoCrete
6100
PC/FA/SAND
1 : 1 : 4
0.38 0.60
0.60
0.79
22.8 cm (9”)
9 cm (3 ¾”)
25.4 cm (10”)
No
Bleeding
8. Control
9. HEM
10.HEM
SPECCO
Melment
W-30
PC/SAND
1 : 2
0.38 0.55
0.55
1.4
15.5 cm (6 ¼”)
6 cm (2 ¼”)
22.5cm (8 ½”)
No
Bleeding
11.Control
12.Control
13.Control
14. HEM
15. HEM
GRACE.
ADVA-100
PC/SAND
1 : 2
0.38 0.86
0.75
0.65
0.75
1.02
21.5cm (8 ½”)
20.5 cm (8”)
17.5 cm (6¾”)
5.5 cm (2 ¼”)
21 cm (8 ¼”)
Bleeding
Bleeding
No bleeding
No bleeding
No bleeding
Activated mortars require more SP to achieve the same or higher level of flowability. There were
no signs of bleeding in the HEM mortars with SP quantity increased by 30% and more, as
compared to the control mortars. This was typical in mixtures prepared with all considered SPs,
which have distinct formulas. Therefore, HEM aids stability, which is very important in
flowable mortars.
Setting in normal conditions
Figure 2 shows HEM to be responsible for an extraordinary acceleration of initial and final
setting in cement mortars. According to ASTM standard C 403/C403M-05, the time of initial
setting should be determined when the penetration resistance is 3.5 MPa (500psi). Using this
criterion, the initial setting time for activated mortars was between 2.5 –6.5 hours (mortars 3,4),
depending on the quantity of SP. Starting from this point, the penetration resistance of activated
mortars with SP develops much faster, similar to the mortars without SP (1, 2). The time of final
setting in activated mortars was determined at the penetration resistance of 27.6 MPa (4000psi),
as per the ASTM standard, and took place at 4 and 8 hours in mortar with SP=0.67% and in
mortar with SP=1.25% respectively. On the other hand, for conventionally mixed mortar, the
time of initial setting was between 9-10 hours; and final setting was reached after 21-22 hours
(mortar 5, Fig. 2). The activated mortar without SP (mortar 1, Fig.2), having 0.5 hour of initial
setting ends the setting period within 1 hour after the activation is complete.

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2- Hand Mixing (SP=0.0%)
1- High-Energy mixing (SP=0.0%)
4- High-Energy mixing (SP= 1.25%)
3- High-Energy mixing (SP= 0.67%)
PenetrationResistance,MPa
210
20
10
40
30
53
Hours
10
80
60
50
70
90
6000
PenetrationResistance,psi
15 20
1000
23
500
4000
2000
12000
8000
10000
14000
Fig.2 - Setting of mortars by method of penetration resistance (SP shown in percents of cement
quantity).
The initial setting time of the non-activated mortar without SP (mortar 2, Fig.2) was 1 hour,
final setting – 3 hours. Mortars 1 and 2, prepared without SP were tough, non-workable
mixtures, which were tamped during manufacturing of samples.
Setting of mortars with fly ash
Fig. 3 shows the penetration resistance of mortars with 50 % of the cement content replaced by
fly ash. The difference between mortars with SP (3, 4) and without SP (1, 2) is apparent. The
retardation activity of SP (SiKa ViscoCrete 3010) develops here similar to mortars without fly
ash (Fig 2). But initial setting of activated mortar occurs in about 14 hours, i.e. 7-7.5 hours later
because the quantity of active binder - cement is half as much. The time of initial setting for both
activated and non-activated mortars is almost the same. The crucial difference is observed after
14-15 hours, when penetration resistance of the activated mortar increases much faster (similar to
mortar without SP) than the non-activated mortar. The final setting occurs in the former after 16
hours; in the latter after 33 hours.

10
20
10
1
0
1032
40
20
30
50
2000
500
40
1000
30
0
7000
6000
5000
4000
3000
1- High-Energy Mixing (SP=0.0%)
3- High-Energy Mixing (SP=1.0%)
Fig.3 - Setting of mortars with cement and fly ash (SP shown in percents of cement + fly ash
quantity).
Analysis of results in penetration resistance of mortars with and without fly ash has shown that
the hydration reactions in activated mortar were temporarily slowed down by SP. Growing
crystals of hydration products may overcome the resistance of SP films at the time of initial
setting because of mechanical activation. The further increase of penetration resistance continues
almost parallel to curves 1 and 2 (Fig. 2, 3), i.e. similar to hard mortars without SP. Non-
activated mortars with SP develop penetration resistance more slowly and achieve final setting
significantly later than activated ones.
HEM actively accelerates setting of mortars. When working with HEM in hot weather
conditions, adding fly ash instead of a part of cement may slow the time of initial setting. A
comparison of setting development of activated mortars with and without SP shows the
important role of this admixture, and not only in the increase of flowability. SP “SiKa
ViskoCrete 3010”, for instance, works in activated mortars as a retarding admixture as well, and
may be used to control setting time.
Syneresis in activated mortars
During this study, the surface of fresh mortar samples taken from activated and non-activated
mixtures were scrutinized in relative humidity (RH) of 40-50% and 95%. Figures 4 a-d show the
exterior appearance of specimens magnified x 100.

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a) Control, just after b) Control 8 hours after c) HEM, just after d) HEM, 3hours
mixing mixing (50% R.H.) mixing after mixing.
Beginning of
setting, syneresis.
Fig.4 - Views of samples surface magnified x 100, taken during the test of penetration
resistance.
There were no immediately apparent differences between activated and non-activated mortars,
except in color: the former was paler in contrast to the yellowish tone of the latter. The white
(pale) color of fresh HEM mortar, visible under microscope, belongs to the thick layer of gel of
white Portland cement covering yellow grains of sand. The fresh control mortars show a
yellowish hue, because the color of sand grains prevails. Within 2.5-3 hours, the water drops
began to appear on the surface of the HEM mortar with 0.67% of SP (Fig. 4 d) nearly matching
the initial setting time. After 4- 4.5 hours (final setting) the drops of water were apparent even
without magnification (Fig. 5). Such discharge of water, known as syneresis, is typical in gels.
Fig. 5 - Specimens in box, 95% ambient RH, syneresis of HEM mortar - right.
Syneresis is much more noticeable in the HEM mortar, since most of the free space between hard
particles is filled with C-S-H gel. In contrast, the surface of non-activated samples appeared dry
with RH levels of both 50% or less and 90% or more.

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According to T.C. Powers [13], when cement and water interact the thickness of the film of
water adsorbed by the surface of cement does not exceed 1.8 nm, approximately 10-13 diameters
of water molecules attracted to cement granules by the Van-der-Waals forces. T.C. Powers refer
to B.V. Deryagin, who asserts that water in this layer has properties different from the free water,
occupying the remaining volume. These ideas are substantiated by Bö Johnson’s study [14] of
the interaction between C3S particles and water, which shows the surface charge of the particles
at the distance of over 2 nm dropping almost to neutral.
Bozhenov U.M. states that the water layer potentially a 150 nm (0.15 m) thick and consisting of
molecules oriented in chains may be attracted by the surface of solid particles [15]. Considering
these data and knowing the specific surface of cement and sand, the calculated total volume of
the attracted water in 1 kg of conventionally mixed mortar (Portland cement – 296.4 g, sand –
592.9 g, water – 110.7 g) will be 17.5 cu cm, i.e. no more than 20% of water incorporated into
the mixture. Thus, 80% of free water remain incapable of producing C-S-H gel and may
potentially evaporate; resulting in micro-cracks on the surface of non-activated specimens under
50% RH within 8 hours after mixing. That is due to evaporating water and drying shrinkage (Fig.
4b). The conditions of 95% RH prevented water from evaporating and therefore cracks on the
surface. These results are consistent with the study of T.C. Powers and many other authors.
The syneresis observed on the surface of activated samples starting at 3 (Fig. 2, mortar 3) and 5-
6 hours (Fig.2, mortar 4) points to the formation gel and active growth of crystals in the cement
matrix. The modern theory of cement gel aging, as outlined in J. Thomas and Hamlin Jennings’
research [16], attributes this process to an increase in the degree of polymerization
(polycondensation) of the silicate network that frees water molecules. Using the conventional
method of mixing as their basis, the authors experienced difficulties observing syneresis, as it is
hindered by the presence of significant amounts of non-gel phases. Thus, the quantity of expelled
water may be considered as an indicator of C-S-H gel quantity in mortars. The water discharge in
HEM mortar remains unaffected by the fluctuations in ambient RH (from 48% to 95%), unlike
the conventional mixture, where water migration is influenced primarily by the changes in
relative humidity. Thus, the initial process of cement hydration in films of the water layer 1-2
nanometer thick spreads out over the entire volume of the cement - water matrix. Therefore
HEM can be considered as an effective way for industrial application nanotechnology of
concrete.
Setting of mortars in temperatures below freezing
Three cement mortars identically proportioned (Portland cement/Sand/Water = 1/2/0.37) were
tested in freezing conditions. Mortar 1 was hand-mixed with HRWR “SiKa ViscoCrete 3010”
(0.7% of PC).Mortar 2 was super plasticized, hand mixed, similarly to mortar 1, and with the
accelerator ‘Rapid-1’ varied from 25 oz/cwt to 90 oz/cwt (1.5-5.6% of cement mass). Mortar 3
was with same HRWR in the quantity 1.2% of PC, HEM for 5 minutes, with net energy
consumption of 49.5 Kj/kg (22.4 Kj/lb). After mixing, mortars 1 and 2 were stored in normal
temperature for 2 hours, before being immersed in a freezing chamber. They showed 0.5MPa (73

13
psi) and 0.35MPa (50 psi) of initial penetration resistance, respectively. Mortar 3 has shown no
penetration resistance immediately after mixing prior to being stored in a freezing chamber. In
this case, the influence of frictional heating of activated mixture on subsequent cement hydration
was ruled out. Penetration resistance tests were carried out on the specimens after they were
removed from the freezing chamber and left to thaw for 1.5 hours (melting time of ice). The
temperature in the freezing chamber was kept constant at about -13o
C (8o
F). The test results are
shown below in Figure 6. The average results for mortar 2 with accelerator ‘Rapid-1’, based on
the data of 5 mortars with the dosages of this admixture indicated above, are presented.
In comparison to the hand-mixed mortars (with and without accelerator ‘Rapid-1’), the
penetration resistance of activated mortar develops much faster after 8 hours of freezing, i.e. the
liquid phase remains active and does not freeze. This is likely due to the fact that the liquid phase
in HEM mortar is mainly represented by the C-S-H gel with its the smallest capillary pores filled
with a supersaturated solution, and water bound by the solid particles. Under the same
conditions, all unbound (bulk) water contained in pores and capillaries of the ordinary mixture
will freeze, its freezing point being no lower than -8o
C (17.6o
F) according to Olson et al [17].
According to this author’s data, the water freezes in the smaller capillary pores at –23o
C (-9.4F);
the freezing of supersaturated solution in gel pores occurs at –40o
C (-40o
F). This will
conceivably apply to the entire liquid phase in the HEM mortar. Therefore, the initial process of
cement hydration in freezing conditions of -13o
C (8.6o
F) for HEM mortar is much more
intensive (Fig. 6, mortar 3).
50
30
20
10
0
3Hand Mixing
(mortar 1)
2
1
15 20
High-Energy Mixing
(mortar 3)
Hand Mixing
w/Rapid 1
(mortar 2)
5000
40
7000
8000
6000
4000
10
Hours
50
1000
3000
2000
Fig. 6 - Penetration resistance in freezing conditions -13o
C (8.6F)
Aside from penetration resistance, a strength increase in concrete under freezing conditions was
also observed. Activated and non-activated mortars without accelerator were used as the mortar

14
part for preparing two variants of concrete by adding coarse aggregate into ready mortars. Final
mixtures: Portland cement – 415 kg/m3
(704 lbs/Y3
), sand – 830 kg/m3
(1400 lbs/Y3
), limestone
aggregate – 1106 kg/m3
(1865 lbs/Y3
), water -153 kg/m3
(257 lbs/Y3
) were used to prepare
samples of concrete. HRWR SiKa 3010(50%) was added in quantity of 7.43 kg/m3
(12.52
lbs/Y3
) into control mixture, and 14.1 kg/m3
(23.8 lbs/Y3
) into activated mixture. All samples
were placed in freezing chamber at -13o
C (8.6o
F) for curing. The compressive strength tests were
completed after removing samples and thawing them at room temperature for 1.5 hours (melting
time of appropriate quantity of ice). Even after 28 days, it was impossible to remove the
specimens of hand-mixed concrete intact from the molds, due to their lack of strength. The
activated concrete specimens were removed from the plastic molds after 3 days of storage in the
freezing chamber and showed 141 psi (1.0 MPa) of average strength. Those kept for 28 days
showed 429 psi (3.0 MPa).
Thus, the process of cement hydration took place in the temperature much lower than 0o
C. It is
consistent with Deryagin’s data on the significant change in the properties of water in boundary
layers, including freezing temperature. In [18] he states that the Van-der-Waals forces,
electrostatic forces, and hydrogen bonds of water molecules to atoms of solid substrate are
responsible for these phenomena. It is likely that mechanical activation by HEM favorably
amplifies these factors. Further investigation is required to estimate their role in HEM
technology.
Strength increase at low temperatures
To assess the kinetics of concrete strength increase at temperatures between 0 and 5o
C (32-41o
F),
the specimens of concrete, proportioned as mentioned above, were stored at +3о
С (37o
F).
Figure 7 shows data on compressive strength after 3 and 28 days in low temperature conditions.
The Manual for Highway Construction of AASHTO («Cold Weather Concreting») recommends
discontinuing the placing of concrete at temperatures below +4.4 Co
(40o
F). By contrast, HEM
makes concreting at low temperatures possible.

15
CompressiveStrength,MPa
5
10
15
20
25
45
35
30
40
CompressiveStrength,psi
28 days3 days
1000
2000
3000
Hand Mixing
High-Energy Mixing
5000
4000
6000
7000
Fig. 6 - Development of strength in activated and non-activated concrete
at +3o
C (37.4F).
Strength of concrete and mortars with High Volume Fly Ash (HVFA)
It is well known that the principal disadvantage of using fly ash in concrete is its impact on early
strength [3]. In connection with this, experiments were conducted to determine a way to speed up
the HVFA binder hydration. In these mortars, 50% of total cementitious materials were replaced
by class F fly ash.
The following variants were compared:
- Mortar without fly ash (100% Portland cement type 1), conventional mixing
- Same mortar, aсtivated by HEM
- Mortar with 50% fly ash, conventional mixing
- Same mortar, activated by HEM
With conventional mixing, no improvement in workability was observed with fly ash, in contrast
to the mortar without fly ash. This fact made it impossible to lower the water quantity. The ratios
of water to cementitious materials (0.38:1) and of cementitious materials to sand (0.5:1)
remained the same in all the variants.

16
Cement 50%,FA 50%, conv.mixing
Cement 50%, FA 50%, HEM
Cement 100%, conv.mixingCompressivestrength,MPa
30
10
0
20
70
50
40
60
80
Cement 100%, HEM
Compressivestrength,psi
4000
2000
0
10000
8000
6000
12000
1 3 28 60 90 days
Fig. 8 - Compressive strength of activated and non-activated mortars.
Table 1- Mix Proportions and properties of concrete
Variant
of concrete
Ingrédients Quantity,
kg/cu.m.*
A B
Plastic
Density
kg/cu.m*
A B
Air, %
Slump, in
Vebe, sec.
A B
1.Cement 100%,
Conventional
mixing
Cement
Sand, QuiKrete
Water
Aggr: Limestone
Granit
SiKa 3010
SiKa 6100
408 410
815 821
155 157
1094
1046
7.8
2.77
2427 2490 1.8 2.54
0.0
25 - 30

17
2.Cement 70%,
Fly Ash 30%
Conv. mixing
Cement
Fly Ash
Sand, Windham
Aggr: Granit
Water
SiKa 6100
268
134
803
1031
150
2.73
2389 2.41
0.0
25 - 30
3.Cement 70%,
Fly Ash 30%
HEM
Cement
Fly Ash
Sand, Windham
Aggr: Granit
Water
SiKa 6100
272
136
815
1046
152
4.16
2425 0.74
0.0
15 - 20
4. Cement 50%
Fly Ash 50%,
HEM
Cement
Fly Ash
Sand, Quikrete
Water
Aggr: Limestone
Granit
SiKa 3010
SiKa 6100
202 205.3
202 205.3
808 821
151 156
1095
1038
10.9
4.81
2406 2494 0.98 0.65
0.0
10 - 15
5. Cement. 50%
Fly Ash 50%,
Conv. Mixing
Cement
Fly Ash
Sand, Quikrete
Water
Aggr: Limestone
Granit
SiKa 3010
SiKa 6100
199.5 200
199.5 200
798 802
149 152
1069
1025
7.6
2.71
2373 2431
3.3 2.49
0.0
20 - 25
*)Lbs/Y3
= 1.683kg/m3
Figure 8 shows a significant increase in strength after the first 24 hours and over the next 3, 28,
60 and 90 days, when activation by HEM was used. This increase occurs in both mortars with
50% fly ash in the binder, and in those completely without fly ash.
The accelerating effect was attained not only in mortars, but also in concrete where the mortar
component was high energy-mixed (Fig. 9). The main difference between proportions of HEM
and hand-mixed concrete is the increased quantity of HRWR admixture that results from a higher
stability of mechanically activated mixtures (Table 1). In activated mixtures, there is evidence of
a higher specific gravity and a lower entrained air quantity, as compared to non-activated
mixtures. All concrete mixtures were characterized by similar consistency – zero slump in all,
and workability by the Vebe method, of 10-20 sec. for HEM mixtures, and 20-30 sec. for control
mixtures. Each variant was repeated at least 6 times (3 times with granite coarse aggregate and 3

18
times with limestone one), except the mixes with 30% of Portland cement replaced by fly ash,
which were repeated 3 times with granite coarse aggregate.
The results in strength of concrete (Fig. 9) are shown in form similar to the results of PPC
strength tests given in [3; page 169; Fig. 7], prepared with vibratory milled fly ash, in order to
easily compare the effectiveness of HEM vs. High-Energy milling.
H
C
CompressiveStrength,psi
C
50%
H
30%0%
28 days
1000
0
2000
4000
3000
5000
6000
H
C
50%
H
30%0%
15
10
20
30
25
35
40
0
5
3 days
C
CompressiveStrength,MPa
C - conventional mixing, H - HEM
C
C
- mixes A with granit and SiKa-6100
- mixes B with limestone and SiKa-3010
Quantity of fly ash, class F
Fig. 9 - Compressive strength of activated and non-activated concrete.
According to the data on strength (Fig. 9), concrete with an activated mortar component
containing 30% and 50% of Class F fly ash showed 5000 psi (30-35 MPa) 28 days compressive
strength, which is no lower than the control concrete without fly ash. This is true in both kinds of
coarse and fine aggregates as well as HRWR admixtures most often used in concrete.
The consumption of energy during activation was about 18.5 kWh per cu. m of concrete or 45
kWh per 1 ton of cementitious materials (not accounting the energy loss in motor and
transmission). These data were compared with the method of additional cement grinding
characterized by the same level of energy consumption (Table 3), calculated from formulas of
concrete strength gain given in [1].
Table 3-Strength increase with the different methods of activation (* data are taken
from L. Lindström and B. Westerberg [1])

19
VARIANT
Effect of Strength increase, %
24 hours 3 days 28 days
1.Fine Ground
Cement * 22.5 13.9 5.6
2.Cement 100%,
HEM 68 33 25
3.Cement 50%, FA-
50%, HEM 132 56 37.6
The above data shows that activation by HEM is more effective than the method of additional
grinding, in terms of the relative increase in strength.
Taking into consideration the results in strength of samples that contained HVFA (Fig.9), we
conclude that, when activation by HEM is used, up to 50% of cement (202 kg per cubic meter or
341 lbs/Y3
.) could be replaced with class F fly ash without losing strength. The energy consumed
in manufacturing this quantity of cement would total 314 kWh (calculated using data from [8]).
Given the 12.6 kWh of gross energy consumed during activation of this quantity of cement by
HEM (expected energy losses of 40% included), the actual amount of saved energy is
approximately 300 kWh per 1 cubic meter (230 kWh per 1 Y3
) of concrete.
FURTHER RESEARCH
An increased volume of gel content in mechanically activated mortar component might reduce
capillarity in concrete. This phenomenon will help avoid penetration by the chlorine ion, as well
as reduce cracks forming in concrete under high and dynamic loads. These two points require
further investigation. The study of relevant mechanical properties such as static modulus of
elasticity, Poisson’s ratio in compression, as well as creep and shrinkage should be carried out.
There are some preliminary results after conducting freezing/thawing tests of HEM concrete with
and without fly ash. These tests should be continued with the aim of obtaining reliable data on
the durability of HEM concrete. HEM technology and High-Energy milling of fly ash [3], both
result in lower Portland cement consumption and should be investigated in combination to see if
this effect will amplify.
Another area worth investigating is the benefit that the increase in volume of the C-S-H gel
might bring to the field of Portland cement solidification and stabilization of hazardous waste
consisting of heavy metals as was shown in [19].
CONCLUSION
1. Based on the abovementioned experiments, it was suggested that the indices of
flowability reduction, temperature increase, and specific energy consumption should be used to
monitor the process of HEM.
2. HEM can potentially increase volume of bound water to form the C-S-H gel. Therefore, the
classical nano-process of initial cement hydration in conventional technology is spreading in the

20
entire volume of the cement-water suspension in concrete. HEM can be considered as an
effective way for industrial application nanotechnology of concrete.
3. HEM is effective for High Volume Fly Ash concrete. Though lacking in binding properties,
Class F Fly Ash could be used for partial (up to 50%) replacement of cement.
4. The proposed method successfully accelerates the process of cement hydration, even in
low temperatures and also under freezing conditions.
5. After in-plant approbation, HEM is recommended for casting cement-sand roof and siding
tiles, paving stones (to substitute ceramic materials), as well as HVFA expanded mortar to
replace lightweight aggregate concrete.
6. High-energy mixing of mortar or mortar component of concrete during several minutes in
specially designed mixer-activator may be considered as a more energy-effective method,
alternative to additional grinding of Portland cement.
REFERENCES
[1] L. Lindström and B. Westerberg, “Fine Ground Cement in Concrete-Properties and
Prospects,” ACI Materials Journal 100 (5) (2003), pp. 398-406.
[2] K. -B. Park, J.L. Plawsky, H. Littman, J.D. Paccione, “Mortar properties obtained by dry
premixing of cementitious materials and sand in a spout-fluid bed mixer,” Cement, Concrete
Research. 36 (4) (2006), pp. 728-734.
[3] Rakesh Kumar, Sanjay Kumar, S.P. Mehrotra, “Towards sustainable solutions for fly ash
through mechanical activation. Review,” Resources Conservation & Recycling 52 (2007).
pp.157-179.
[4] Zivko Sekulic, Svetlana Popov, Mirjana Duricic, Aleksandra Rosic, “Mechanical activation
of cement with addition of fly ash,” Materials Letters 39 (1999), pp. 115-121, Elsevier.
[5] H. Hodne, A. Saasen, A.B. O’Hagan, S.O. Wick, “Effects of time and shear energy on the
rheological behavior of oil well cement slurries,” Cement Concrete Research 30 (2000), pp.
1759-1766.
[6] M.L. Brown, H.M. Jennings, W.B. Ledbetter, “On the generation of heat during the mixing
of cement pastes,” Cement Concrete Research 20 (1990), pp. 471-474.
[7] Gary R. Mass, “Premixed Cement Paste,” Concrete International 11 (1989), pp. 82-85.
[8] N. Martin, E. Worrell, L. Price, “Energy Efficiency and Carbon Dioxide Emissions
Reduction Opportunities in the U.S. Cement Industry,” Ernest Orlando Lawrence Berkeley
National Laboratory, 9 (1999), p.3
[9] G. Frohnsdorff, “Blended cements,” ASTM International (1986), p.19.
[10] V.V. Fridman, K.M. Katz, “Method of producing of agitated mineral binder,” Certificate of
Invention, USSR #1668344 8/1991.
[11] V.V. Fridman, F.M. Krantov, I.M. Reznikov, “Metod V.V. Fridman dlia proizvodstva
aktivirovannoi stroitel’noi smesi,” Patent #2017701, Russian Federation, 8/1994.
[12] V.V. Fridman, “Method for producing construction mixture for concrete,” Patent USA
#5,443,313 8/1995

21
[13] T.C. Powers, “Nature of Concrete,” Concrete and concrete – making materials, 1966, pp.
61 – 72.
[14] Bo Jösson, “Cement – The real Nanotechnology,” Abstract,
http://www.fos.su.se/%7Egunnar/seminarier/Abstract.pdf
[15] Bazhenov U.M.” Technology of Concrete,” Moscow, “Vysshaja shkola”, 1978, pp.51-52
[16] Jeffrey J. Thomas, Hamlin M. Jennings, “A colloidal interpretation of chemical aging of the
C-S-H gel and its effects on the properties of cement paste,” Cement and Concrete Research 36
(2006), pp. 30-38.
[17] R.A. Olson, B.J. Christensen, R.T. Coverdale, S.J. Ford, G.M. Moss, H.M. Jennings, T.O.
Mason, E.J.Garboczi, “Interpretation of the impedance spectroscopy of cement paste via
computer modeling III: Micro structural analysis of frozen cement paste,” Journal of Material
Science 30, (1995), pp. 5078-5086
[18] Deryagin B.V., Churaev N.V., Zorin Z.M., “Structure and properties of boundary layers of
water,” Izvestiya Akademii Nauk SSSR, Physical Chemistry, No. 8 (1982), pp.1698-1710
[19] W.A. Klemm “Ettringite and Oxyanion-Substituted Ettringites – Their Characterization and
Applications in the Fixation of Heavy Metals…” Portland Cement Association 1998, pp. 2, 7, 42

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