Royak G. S., Dobkin V. S., Kozodaev G. A. «Silicate microspheres for light concrete»

Summary: the results of experimental researches confirming
possibility of application of silicate microspheres with small
volumetric weight for manufacture of light concrete and thermally
insulating compositions are described.

The purpose of research included studying possibility
of regulation of portland cement binding agents` properties
by admixtures of microspheres and finding ways of
application of the developed materials in construction industry.
Samples of various mixtures were tested in order
to estimate mechanical strength, volumetric weight, heat
conductivity and frost resistance factors.

At light concrete manufacturing the optimum quantity
of the additives admixed to portland cement lays
within the limits of 20-40% by weight. Ratios of portland
cement to silicate microspheres shown in table 1 were
chosen for the research.

Series of 3 similar samples each were prepared for
definition of following properties:

•Humidity (W),

•Compression strength (R),

•Volumetric weight of a material (γ),

•Factor of heat conductivity (λ),

•Water absorption (W).

Table 1

Samples after formation and one day period of initial
hardening were put into steam curing chamber: 7 hours
rise of temperature up to +70° С, 6 hours curing at +70° С,
final decrease in temperature down to +20° С within
8 hours.

Diagram 1. Dependence of concrete sample durability on the content of microspheres

Table 2

Table 3

Samples after curing were dried up in drying cabinet
at +40 °С within two days.

Values of volumetric weight for samples series are
shown in table 2.

Values of heat conductivity factor for samples series
are shown in table 3.

As can be seen from tables 2 and 3, introduction
of silicate microspheres’ admixture to portland cement
of 20-35% by weight reduces volumetric weight of the
hardened samples in 2-3 times.

Results of heat conductivity factor measurements
of the samples hardened in various hardening and drying
terms also confirm increasing of thermal protecting properties
in 2-3 times.

Compression tests’ data for aerated and hardened
cement paste with silicate microspheres’ admixture
with allowance for scaling factor and humidity of a material
are shown in тable 4, as well as values of volumetric
weight.

Freeze-thaw durability tests were carried out for
series 1 samples (see Table 1). Water saturated samples
50×50×50 mm in size after 16 cycles of freezing at minus
20° C and thawing in water at room temperature did not
show any visible changes. Water absorption of samples
varied from 6,5 up to 12,21%.

Diagram 2. Dependence of heat conductivity of the sample on the content of microspheres

Diagram 3. Dependence of volumetric weight of the sample on the content of microspheres

Results of researches are brought together on
diagrams 1-3. They prove that in using silicate microspheres
as a component ample opportunities are available
for achievement of desired strength, weight and
thermal insulation parameters of light concrete and cement.
Obtained data can be used in production of light
concrete and cement.

Conclusions:

Developed compositions proved to be progressive
material for application in construction industry as a basis
for production of light concrete and cement mortar
of various application, e.g.:

•Construction concrete;

•Construction concrete with thermal insulation properties;

•Thermal insulation concrete;

And also:

•wet plaster mix;

•facade mortar;

•mortar for restoration.

Table 4


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