Belov V.V. «Dry mixes for production of cellular concrete: experimental research, prospects of production and applications»

Introduction

Modern residential construction technologies involve
use of new methods, effective construction materials that
provide influence onto life period of buildings and level of
comfort of residential space.

These issues are connected with concrete modification
methods, use of dry mixes and construction units in which
various modifying additives are applied. At that, quality is
improving while the overall cost of construction goes down.
Transfer to the use of dry pack mortar in foreign countries
happened several decades ago, thanks to their advantages,
such as convenient method of delivery and stock of dry
mixtures at a construction site, improved quality of construction
works, reduction of loss and transportation costs,
readiness for application, availability of delivery at temperature
below 0°C, and others.

Analysis of today’s situation in production of dry
mixes shows that their range practically does not include
mineral heaving mixes suitable to fill multi-layer framing
constructions or for other heat insulating purposes both
in a process of construction, and in a process of buildings
exploitation. Imported materials of this type are expensive
and frequently manufactured with polymer binding
agents, they can be inflammable, and do not meet requirements
of durability set to main bearing elements of stone
buildings.

Heat consumption for buildings heating in Russia is
three times as high as that in other countries with similar
climate conditions. According to a classification generally
accepted abroad, wooden houses are graded first by comfort
as a residential space, and houses of cellular (porous)
concrete occupy the second place. Europe is streets ahead
Russia by per capita production of cellular concrete. 113 European
plants produce 18 mln. m3 of aerated concrete and
gas silicate a year. Forced urge to overtake Europe, plus introduction of strict heat insulation standards (construction
norms and specifications SNiP 23-02-2003) in Russia, provides
a powerful impact for production of cellular concrete
products, both autoclave-cured and non-autoclave. The
latter gets the second birth, after 1950s, this «renaissance»
comes from relative easiness of non-autoclave concrete
production technology, low metal and energy consumption
of equipment for its manufacturing and, consequently, low
level of investments to set up production. This all resulted
in mass emergence of small producers of foam concrete
and simple equipment for its production. Russian market
of non-autoclave aerated concrete cannot provide quality
stability, because many producers use dubious equipment
and technology. Currently, there is a need for production
of non-autoclave aerated concrete of high quality, both for
cast-in-place construction, and for concrete products. This
purpose can be reached on account of use of aerated concrete
manufactured from dry aerated concrete mixes. It is
sufficient to stir the mix with a necessary amount of a liquid
component, and then place the received mixture into a
form or into a separated site. As a result, aerated concrete
of high quality that meets up-to-date requirements can be
obtained rapidly. This is why creation of high-quality dry
aerated concrete mixes for production of aerated concrete
is a problem of high importance.

1. Basic data on competent conposition of dry aerated concrete mixes and properties of aerated concrete

It is obvious that components of dry aerated concrete
mixes can be traditional dry materials used for production
of aerated concrete in accordance with State Standard
GOST 25485-89 «Aerated concrete. Technical specifications
». These are:

ƒƒ* binding agents: Portland cement and metallurgical
cement of degree not lower than M400 (GOST 10178-
85), calcium quicklime (GOST 9179-77), granulated
slag (GOST 3476-74), highly basic slag (industrial
standard OST 21-60);

ƒƒ* silica components: high-silica sand (GOST 8736-93),
fly ash of heat power plants (OST 21-60).

According to GOST 25485-89, other mineral components
that ensure normative properties of concrete can
be also applied for production of aerated concrete, such
as limestone, ground marshalite, glass sand, flint, calcium
sulfate dihydrate, chalk stone, microsilica, finely dispersed
mica, broken glass, broken ceramic and silicate bricks,
«Betonit», synthetic and mineral fibers, etc. Aerated concrete
can also contain blowing agents: aluminum powder of
grades PAP-1 and PAP (GOST 5494-95) as gas-geretating
agent, foaming agents in a form of concentrated solutions,
chemical admixtures accelerating hydration and setting
(Na2SO4, CaCl2 and others), plasticizers (S-3, LST) and other
components.

It is possible to increase a potential of binding agent
in dry aerated concrete mixes on account of its filling with
mineral structure-forming additives. It should be taken into account that the minimal surface area of a filler should
total 200 m2/kg. The most effective is use of a carbonate
filler, as a strength of interpore partition at carbonate filler
is higher than that at quartz filler. Reasons for increase of
strength of interpore partitions in aerated concrete are
connected with modification of its structure. Use of fillers
made of recycled materials, such as ash, slag and others
that have higher surface activity compared with sand
but lower compared with cement, is not sufficiently effective
due to instability of their properties, as some authors
consider. This problem has been researched in numerous
works, which state that gas concrete mixtures with additives
of ash and slag have a wide range of setting time: less
than 25 min and more than 50 min. Water adsorption at fly
ash from heat power plants may take 4 hours from the beginning
of tempering. At that, in 5 min an effect of false
setting can be observed due to very strong adsorption of
water from intergranular space. The mixture loses plasticity
while a process of gas generation is not completed yet
(when aluminum powder is used as blowing agent), which
leads to imperfection of a brick cell structure. To make a
process of gas generation normal and obtain a fast-blowing
aerated concrete from dry aerated concrete mixes that
contain fly ash from heat power plants, Selivanov V.M.,
Shiltsina A.D. and Gnyrya A.I. in their report [1] suggest
that a fly ash together with other components of a mixture
should be additionally grounded to a fine dispersed
condition. As a result, aerated concrete with the following
properties (Table 1) can be obtained from dry aerated concrete
mixes.

When a component composition of dry aerated concrete
mixes is being developed, special attention should be
paid to selection of a binding agent. It is known from literature
sources, that use of cement with increased content of
alite and tricalcium aluminate ensures production of aerated
concrete with maximal durability and minimal shrinking
deformation. Use of portland-blastfurnace cement and
portland-pozzolan cement leads to decrease in durability
of aerated concrete, deteriorates its air resistibility and increases
shrinking deformation.

1

High activity of binding agent is directly proportional
to its dispersiveness. A possibility of high-dispersed cement
use has been studied in a range of research works. Kuznetsov
V.A. and Shershnev Yu.M. [2] offer to use a dry mix
«Aeromix» of the following composition to prepare aerated
concrete of average density 400-600 kg/m3: Portland cement
М500-D0 – 70%, fine-ground cement (size of particles
up to 5 my) – 20-30% of a binding agent weight, fine-ground
quartz river sand (size of particles up to 40 my) – 30% a binding
agent weight, fine-ground neutral chalk stone, water insoluble
crystallizer and viscosifier ST-1, setting accelerator.

Specific features of aerated concrete hardening in
presence of sodium silicate have been recently studied
by many researchers. At the same time, there is practically
no experience of use of liquid glass in dry mortar and
especially in dry aerated concrete mixes. This is why it is
necessary to study a possibility to use ground silicate block
(dry powder) as a binding agent in composition of dry aerated
concrete mixes. In Russia, hydrated sodium silicate
is produced according to terms of reference TU 6-18-161-
82 under the name «sodium meta-silicate». Its formula is
Na2SiO3•9H2O, the product is a fine crystalline powder of
white color with gray tone.

Most commonly sodium silicate as a binding agent for
aerated concrete is used in liquid form. In such a case, dry
aerated concrete mix is prepared as a composition of solid
components, and then a necessary amount of liquid glass is
added at a tempering stage. An example of such material is
a heat insulating material «Evolit-thermo» (TU 5767-012-
53743439-03) [3, 4, 5], that is prepared on-site from dry aerated
concrete mix and liquid glass. «Evolit-thermo» has an
average density of 180-450 kg/m3, compression strength
of 0,25-1,3 MPa, water adsorption not more than 7% for 24
hours, heat conduction coefficient of 0,048-0,09 Wt/(m, °C)
at (25±5) (Table 3).

Today it is impossible to prepare quality dry mortar
and especially dry aerated concrete mix without modern
modifying chemical additives: accelerators of hardening
and hydration, plasticizers, antifreezing admixtures, etc.
The most commonly used are additives of sodium salts
accelerating the rate of durability increase for aerated
concrete. Influence of powdered polymer additives, and plasticizer S-3 onto gas generation of a mixture is not well
studied yet.

Table 2. Technical data of material «Evolit-thermo» (according to V.F. Korovyakov)

The most frequently used «dry» gas generating agent
in production of aerated concrete is aluminum powder. Gas
generating ability of aluminum powder rises sharply when
a fraction of 40 micron and finer is used. Powder of grades
PAP-1 and PAP-2 meets this requirement. To ensure effective
gas generation, it is very essential to remove films
from a surface of gas generating agent. To remove a fat
film, powder is treated with surfactants and baked in electric
ovens. It is also possible to accelerate pore formation on
account of additional grinding of blowing agent to a fine degree.
Partial deparaffination of powder also takes place at
a process of additional grinding. At the same time, a statement
of authors of one aforementioned work – Selivanov
V.M., Shiltsina A.D. and Gnyrya A.I. is not well reasoned
when they say that quality parameters of aerated concrete
can be automatically reached on account of better use of
blowing agent, aluminum powder, in process of it grinding
together with other components of raw materials mixture
thanks to removal of paraf-fin film from aluminum powder
particles and stripping its inside surface at grinding. It
is obvious that better conditions of paraffin removal from
powder and its more complete use are reached at conventional
treatment with a surfactant solution.

Makarova N.E. [6] tested a method of powder treatment,
under which gas generating agent is being ground
together with dry quartz sand and an additive of acetoformaldehyde
resin ACF-3M. At that, oxide and paraffin
film are removed from surface of powder. At quartz
grinding, bonds braking at formation of free radicals take
place on its surface. Under usual conditions, life span of
those radicals is limited, and quartz rapidly loses its activity.
At grinding at medium of reactive organic compound
(aceto-formaldehyde resin), a polymer that is chemically
adsorbed at surface of quartz, «adheres» fine particles of
powder to surface of sand particles. At that, a process of
powder floating is prevented, and high degree of a mixture
homogeneity is reached.

A process of gas generation can be intensified by adding
chemical admixtures into air-entrained mix. For example,
admixture of calcium chloride CaCl2 intensifies a gas
release reaction, as chlorine ions in alkaline medium accelerate
a process of aluminum solving thanks to their adsorption
on oxidized surface of particles and replacement
of oxygen ions in that surface. This phenomenon promotes
solving of passivating film on aluminum particles at presence
of hydroxide ions. It is possible that other chlorides
(NaCl, KCl) can solve film on aluminum particles.

It was found by Fedynin N.I. [7] that carbon particles
of unburned fuel contained in fly ash of heat power
plants, formed numerous galvanic couples of micro-electrodes
(microelements) with particles of aluminum. Those
couples are in contact with electrolyte – liquid phase of
a mixture. Electromotive force that appears in a system
accelerates and deepens reaction between aluminum
powder and calcium hydroxide, intensifies other physical
and chemical processes. At that, the time of gas generation reduces by 2-2,5 times, the final volumetric gain of a
mixture grows by 5-8%.

In mixes, air-entrained with foaming agent, stability
and adhesion are ensured at a balance of capillary and disjoining
pressure of film water in a zone of capillary convexconcave
lenses, as well as by surface tension forces. Therefore,
it is reasonable to use stabilizing agents in a form of
finely dispersed mineral components, and apply an accelerator
of cement system setting, to increase stability of air cells.
Finely dispersed particles «protect» air cells of a solid phase.
In this case, however, all components of a mixture should be
dry. At the same time, water solutions of foaming agents are
usually used for production of aerated concrete. It is possible
to transfer them into the dry state applying two main methods,
according to Khozin V.G. and Magdeev U.Kh. [8]:

1. Sorption (by mixing with powdered or granulated porous
adsorbent being potentially useful component of
aerated concrete).

2. Chemical (hydration) – by mixing foaming agent with
mineral compounds that undergo a hydration reaction,
for example with calcium oxide, hemihydrate
gypsum and others.

For two methods of obtaining dry foaming agent, optimal
ratios between concentrated foaming agent, adsorbent
and hydratable substances have been determined. At
the first case, the obtained mixture have been dried at a
temperature of 100-105°С to the constant weight (Batalin
B.S., Raskopin S.V. and Pryakhin I.P. offer to dry foaming
agent at temperature not higher than 80°С under condition
of preliminary dispergating, and sometimes without it), in
the second case the product obtained as a result of hydration
reaction was ground.

In the work by Khozin V.G. and Magdeev U.Kh., dry
aerated concrete mix was prepared by a method of intensive
intermixing of all components, such as cement, dry
foaming agent and, if necessary, a filler. Preparation of
aerated concrete with tempering dry aerated concrete mix
with water has been carried out in a laboratory mixer with
a blade rotation rate of 1500 rev/min. Samples hardening
was carried out in metal forms under natural conditions.

Experimental results – properties of aerated concrete
D400-D500 are shown at Tables 3, 4.

As it follows from the data listed in a table, strength of
aerated concrete D400 made from dry mix of the first type
(sorption method of liquid foaming agent transformation
into dry state) is higher than that of a standard sample at all
periods of hardening. At that, admixture of dry mix of anion
surfactant ensures a considerable increase in strength
compared with a standard composition, and also compared
with a composition without additives №2. It should be noted
that all samples of aerated concrete made of dry aerated
concrete mix have lower shrinkage at the age of 28 days.
Comparison of strength parameters of aerated concrete
prepared from dry mixes of the second type (transformation
of liquid foaming agent into dry state with hydration)
with aerated concrete of the first type and with a standard sample shows the following. Aerated concrete made from
dry mixes of the second type leave standard samples behind
by strength, but it is inferior to aerated concrete made
of dry mixes of first type (composition 2). Chemical nature
of foaming agent carrier (adsorbent or crystallohydrate)
plays a considerable role, and this is a subject for following
studies. Nev-ertheless, better strength properties of aerated
concrete made from dry mix are obvious.

Table 3. Properties of aerated concrete made of dry aerated concrete mixes of first type (according to V.G. Khozin and U.Kh. Magdeev)

Table 4. Properties of aerated concrete made of dry aerated concrete mixes of first and second type (according to V.G. Khozin and U.Kh. Magdeev)

2. Experemental studies
Raw materials components:

ƒƒ* portland cement PC 500-DO;

ƒƒ* flu ash from heat power plants in Tver (Tverskaya
TETs-4) and Moscow (Moskovskaya TETs-22);

ƒƒ* aluminum powder of grade PAP-2;

ƒƒ* chemical additives — sodium sulphate and super-plasticizer
S-3.

In this work, Portland cement manufactured by
Oskoltsement, grade PC 500-D0 has been used. Mineral
composition and specific surface area of the cement met
requirements of the state standard GOST 25485 and construction
standards SN 277-80.

Main properties of cement:

ƒƒ* average activity at age of 3 days 20,3 MPa;

ƒƒ* packed density 1190 kg/m3;

*ƒ true density 3110 kg/m3;

ƒƒ* specific surface area 266 m2/kg;

ƒƒ* normative thickness of cement paste 26,5%.

As an ash filler, flu ash from heat power plants in Tver
(Tverskaya TETs-4) and Moscow (Moskovskaya TETs-22)
has been used.

As a gas generating agent, aluminum powder of grade
PAP-2 has been taken.

As an alkali admixture for preparation of dry blowing
mixes, sodium sulphate has been used. This admixture
accelerates the growth of plastic strength of raw materials
mixture and also a process of aerated concrete hardening.
In order to reduce a water/solid phase ratio and to increase
a strength of interpore partitions and honeycomb composite
material in general, admixture of super-plasticizer S-3
(in dry form) has been used in a range of compositions of
dry blowing mixes. This admixture has considerable water-
reducing effect.

Experimental technique

After weighing, all raw material components in dry
form have been fed into a grinding-mill for 30 min grinding.
In a process of mixed grinding, ash reached an optimal
dispersivity. At that, thanks to dispersion and fragmentation
of ahs particles in a process of mixed grinding of mixture
components, a number of active centers on surface of
ash particles is growing, which enables to partially involve
low active dumped ash into a process of concrete setting.
Apart from this, components were evenly distributed in a
volume of mixture, and aluminum powder was partially
deparaffinated at a process of grinding. Then, a dry mixture
was poured into hardening water with temperature
of 45°С, and intermixed during 3 min with a propeller stirrer
at 150-200 rev/min. For some compositions, sulphanole
had been added to hardening water before batching. Sulphanole
was added for better deparaffination of aluminum
powder and additional pore formation in raw materials
mixture, in a form of 20% solution, in amount of 0,25% of a
hardening water weight.

Prepared raw materials mixture has been poured into
forms with dimensions of 10x10x10 cm preliminary heated
in a drying oven up to 40-50°С. In two hours after pouring
into the forms (usually, mixture blowing completed in
30-40 min), a «heel» was cut off with a metal string with a
diameter of 0,2 mm, and forms with samples were exposed
into a steam-curing chamber for 15oe2 hours. Then, the
samples were steamed according to a scheme of 1,5+8+1,5
hours at a maximum temperature of 85oe5°С. After form
removal, samples of gas-ash concrete were exposed into a
drying oven, where they were dehydrated at 105-110°С to
the constant weight. Then, average density and compression
strength of dry samples were determined according to
the existing standards.

Results of experiments for selection of optimal composition
of dry blowing mixes for production of non-autoclave
gas-ash concrete.

Table 5. Matrix for planning and experimental results for selection of dry blowing mixes compositions

Selection of compositions of dry blowing mixes based
on fly ash from heat power plant TETs-4 was carried out
by way of varying factors of ash/cement, aluminum/solid
phase and water/solid phase within the frames of the experiment
plant. The weight ratio ash/cement was varied
within the limits of 0,75 to 1,5; weight ratio aluminum powder/
solid phase (total weight of cement and ash) – from
0,075% to 0,15%; water/solid phase ratio – from 0,45 to 0,55.
Experiment plan table and experimental results are shown
on the Table 5.

Pic. 1 Isolevel lines of average density in dry condition (dotted line) and strength (full lines) of gas-ash concrete for different content of aluminum powder in dry mixture aluminum/solid (A/S) and water/ solid ratio (W/S)

Table 6. Calculated compositions of dry blowing mixes

Diagrams of dependence of density and compression
strength of gas-ash concrete on content of aluminum powder
at different values of water/solid phase ratio, as well as
isolevel lines of these properties of the material (Pic. 1) enable
to create a basis for selection of optimal compositions
of dry blowing mixes for production of gas-ash concrete
with density between 650 and 800 kg/m3 (Table 6).

Further experiments had a purpose to decrease density
of gas-ash concrete when the strength is sufficient. At
the beginning, values of variable factors in a mathematical
model describing dependence of density were counted.
It appeared that the minimal value of average density in
dry state – 616 kg/m3 could be reached when the ratio
ash/solid phase totaled 0,15% (maximal level of this factor
in experiments) and water/solid phase totaled 0,51. In this
case, ultimate compressive strength totaled 1,42 MPa.

Further reduction of gas-ash concrete density, under
condition that its strength stays sufficient, is possible
on account of increasing the share of sodium sulphate up
to 1,5% of a total weight of cement and ash if counted on a
dry basis, some increase of aluminum powder content, and
introduction of admixture S-3 at a quantity of 0,75% of cement
weight.

Table 7. Physico-mechanical properties of non-autoclave aerated concrete produced from dry blowing mixes

Table 8. Range and discreteness of variable factors in composition of dry aerated concrete mixes for production of non-autoclave gas-ash concrete

Properties of gas-ash concrete prepared from dry
blowing mixes (Table 7) show that suggested compositions
of dry blowing mixes and methods of their preparation enable
to obtain gas-ash concrete that meets requirements of
GOST 25485 set to non-autoclave concrete in a wide range
of strength and density.

Limits within which variable factors of dry aerated
concrete mixes composition and their discretisation for selection
of composition are shown at Table 8.

Further improvement of dry blowing mixes technology
with a purpose to reduce a download onto grindingmill,
power consumption and to raise productivity can be
reached by way of excluding grinding of such relatively
dispersed component as cement. It was suggested to grind
only ash component together with aluminum powder and
chemical admixtures. Ground mixture of these components
was then intermixed with cement, and received mixture
was poured into hardening water, into which sulphanole
had been preliminary added in a form of 20% solution at
a quantity of 0,25% of hardening water weight. At that, it
appeared that it is necessary to increase a dosage of sodium
sulphate and aluminum powder, and also to introduce an
additional alkaline admixture (that also accelerates setting)
to obtain heat insulating aerated concrete of rather
low density and suffi-cient strength. After testing a range of alkaline admixtures including potash, soda ash and calcium
chloride, the latter was selected for its better effect.

Table 9. Parameters of gas-ash concrete compositions made of dry aerated concrete mixes based on ash from heat power plant TETs-22 manufactured under improved technology, with optimal properties

Table 9 shows characteristics of two compositions of
numerous tested, on basis of ash from heat power plant
TETs-22. These compositions have optimal combination of
density and strength for use as constructional and heat insulating,
and as heat insulating material.

Consumption of raw materials for preparation of
gas-ash concrete from aforementioned dry blowing mixes,
per 1 m3.

Constructional and heat insulating non-autoclave
gas-ash concrete of density grade D 600 and strength
class B 1,5:

ƒƒ* Portland cement M 500 – 280 kg;

ƒƒ* Ash from TETs-22 – 280 kg;

* ƒƒAluminum powder – 0.87 kg;

ƒƒ* Super-plasticizer S-3 – 2.1 kg;

ƒƒ* Sodium sulphate – 5.6 kg;

ƒƒ* Calcium chloride – 5.6 kg;

ƒƒ* Sulphanole (20 % solution) – 0.7 l;

* ƒƒWater – 285 l.

Heat insulating non-autoclave gas-ash concrete of
density grade D 500 and strength class B 1:

ƒƒ* Portland cement M 500 – 230 kg;

ƒƒ* Ash from TETs-22 – 230 kg;

* ƒƒAluminum powder – 0.87 kg;

*ƒƒ Super-plasticizer S-3 – 1.7 kg;

* Sodium sulphate – 6.9 kg;

*ƒƒ Calcium chloride – 4.6 kg;

*ƒƒ Sulphanole (20 % solution) – 0.6 l;

* ƒƒWater – 235 l.

Patents for invention of the Russian Federation have
been issued for compositions and methods of preparation of
non-autoclave gas-ash concrete made of dry aerated concrete
mixes.

For production of pilot batches of gas-ash concrete
from dry blowing mixes, company Antikorstroy
(Moscow) selected two aforementioned compositions
based on flu ash from heat power plant TETs-22:
constructive and heat insulating, and heat insulating
– according to GOST 25485. These compositions have
the most favorable combination of average density
and compression strength for production of the most
widely used walling.

Test samples of gas-ash concrete were made according
to GOST 10180-90 by means of sawing-out control
blocks with dimensions 40х40х20 cm after they had
been thermally treated in steam-curing chamber under
a scheme recommended by construction rules SN 277-
80: heating up to the temperature of 85oe5° С during 1,5
hours, isothermal exposition for 8 hours and decrease of
temperature during 1,5 hours (the whole cycle of thermal
treating takes 11 hours).

1

Pic. 2 Scheme of dry aerated concrete mixes production

Samples of gas-ash concrete were tested for
strength (after hardening under normal conditions
during 28 days), thermal conductivity (for samples of
heat insulating concrete of density grade D500 and constructive
and heat insulating concrete of density grade
D600), freeze-thaw durability and drying shrinkage
(for constructive and heat insulating concrete D600).
Thus, their compliance with requirements of GOST
25485 was estimated.

Based on results of experimental-industrial approbation
and tests of pilot batches of gas-ash concrete
made of dry blowing mixes, technological scheme of
production (slide 14) and technical specifications for dry blowing mixes used for production of non-autoclave
ash-containing aerated concrete have been developed.

3. Prospects of production and applications

Decision considering feasibility and effectiveness of
production of gas-ash concrete from dry blowing mixes
containing flu ash from heat power plants should be based
on comparison with traditional non-autoclave cellular concrete
containing ground sand. It is necessary to compare
costs for use of these materials in building units and constructions,
in particular in building blocks with constructive
and heat insulating properties, and also as heat insulating
material itself. The calculations are based on compositions
of constructive and heat insulating gas-ash concrete made
of dry aerated concrete mixes, given in the present work,
and compositions of traditional non-autoclave aerated concrete
of similar use. Average market price of those compositions
components was taken.

Examples of calculation of economical effectiveness
for aforementioned materials when used for production of
building blocks with constructive and heat insulating function
are shown at Table 10, when used for production of
heat insulating material – at Table 11.

Calculations show that application of a newlydeveloped
technology for production of non-autoclave
gas-ash concrete from dry aerated concrete mixes containing flu ash from heat power plants enables to reduce
costs by average 20% on account of effectiveness of raw
materials use. At that, cement consumption reduces by
30%, and on account of reduction of material consumption
for building elements, as well as energy consumption
in a process of their production, overall reduction of
costs for production of gas-ash concrete from dry aerated
concrete mixes totals not less than 30-35% if compare
to similar materials. Additional energy saving and ecological
effect is reached thanks to use of flu ash of heat
power plants as a core raw material.

4. Conclusion

The present work suggests a technology for production
of non-autoclave gas-ash concrete with preliminary
preparation of dry raw materials mixture that contains
all necessary components and chemical admixtures. After
tempering with water and intermixing in usual mixer,
raw materials mixture is poured into forms, where
it is blowing and then hardening at normal conditions
or with minor thermal treatment. Technical specifications
and process regulations for production of dry cellular
concrete mixes used to make non-autoclave gas-ash
concrete on base of flu ash from heat power plants have
been developed.

Mineral dry blowing mixes of light weigh can be
applied to fill construction joints, knots, caverns in walls
and heat insulating elements and blocks forming no «cold
joints» and ensuring solidity of a block. Results of the work
enable to combine advantages of gas-concrete technologies
and technologies of dry mixes, and improve a method
for production of non-autoclave gas-ash concrete using a
complex of chemical admixtures. As a result, highly effective
construction materials can be obtained. These materials
have satisfactory physical and mechanical properties,
they are environmentally safe, their cost and energy
consumption are low.

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