NATURAL SCIENCES AND NEW TECHNOLOGIES
81
Computer Modelling & New Technologies, 2000, Volume 4, No.1, 81-83
Transport and Telecommunication Institute, Lomonosov Str.1, Riga, LV-1019, Latvia
PERSPECTIVE WAYS OF DIRECT CONCRETE HYDRO-
ISOLATING CAPABILITY CONTROL AND REGULATION
A.S. KOROLYOV, L.Y. KRAMAR, B.Y. TROFIMOV
South-Ural State University, Chelyabinsk, Russia
The problem of cement hydro-isolation and concrete water impermeability is discussed. A relationship between concrete
hydro-isolation capability and its consistence from water-cement ratio (W/C) is also investigated.
In last years the problem of cement hydro-isolation and concrete water impermeability acquires
new actuality. This tendency has next reasons: 1) increasing of the demand for building construction
secondary protection providing results in distributive and inexpensive hydro-isolating materials need; 2)
this purpose can be achieved effectively by using the cement plasters and concrete for making plastering
or bearing coverings; 3) receiving of the cement hydro-isolation with required quantity defines the
necessity of hydro-isolating cement materials designing and controlling methods improving
.
The analysis
of whole knowledge concerned with these problems showed impossible to answer objectively how to
define and what defines the quantity of hydro-isolating cement mortars and concrete.
The absence of objective hydro-isolation capability characteristic is concerned with the specifies
of concrete impermeability nature
.
Impermeability of cement concrete depends on its working width.
There were shown in different research works /2,5/ that hydro-static pressure in concrete decreases right
proportionally to the distance from its pressured surface. Nevertheless the water impermeability
atmospheres tested on concrete samples of standard width cannot be performed for the same concrete of
other width with satisfactory exactness. Our research results show that this is related with capillary
phenomena in imbibing cement paste porosity system
.
It is necessary to include capillary pressure in
pressure balance inside concrete body because it can exceed 2..3 at. On this base the new accelerated
method of concrete water impermeability definition was built. It includes next stages:
1) definition of average water impermeability macro-pores radius (>0.1mk in radius):
r =
√
[8
η
[h
0
lnh
0
/(h
0
- h) - h]/
τρ
g] ,
where
η
= 10
-3
is the water viscosity, Pa
.
sec;
ρ
= 1000 is the water density, kg/m
3
; g = 9.8 is the gravity
constant, m
2
/sec; h is the height of water imbibing defined on the air-dried sample placed on wet surface
after
τ
= 1 test hour (3600 sec), m; h
0
is the maximum height of water imbibing defined on the air-dried
sample placed on wet surface after
τ
= 24 test hour, m.
2) calculation of water-resistance characteristic in atmospheres per meter of concrete width:
2
σ
cos
θ
/rh
0
10
-5
= t ,
where
σ
= 72.2х10
-3
N/m is the water surface tension;
θ
= 0 is the moistening angle.
3) calculation of maximum water imbibing height h
max
(required concrete working width) under the
definite hydro-static pressure
∆
P:
h
max
= (
∆
P + th
0
)/t ;
4) calculation of concrete water impermeability for definite working width
δ
:
∆
P = t
δ
- th
0
.
NATURAL SCIENCES AND NEW TECHNOLOGIES
82
The data of this methodic correlation are shown in Table (а
с
is the air impermeability coefficient,
C/S/G is cement-sand-gravel ratio,
∆
P-calc is the calculated water impermeability, W is the
water
impermeability defined by standard methodic, time of hardening in days). Using this methodic it is
possible to get objective and relative concrete hydro-isolation characteristic - t. Also this methodic can be
used for any liquid impermeability definition.
TABLE. Comparative results of water impermeability tested by standard and accelerated methods
№
Consistence
of concrete
h,
m
h
0
,
m
r,
mk
t,
at/m
δ
,
m
∆
P-
calc,
at
а
с
,
cm
3
/sec
W,
at
1 C:S:G=1:2:4,
W/C=0.7 0.031 0.080 1.36 13.4 0.15 0.94 0.530
-
2 C:S:G=1:2:4,
W/C=0.5 0.017 0.046 0.98 32.1 0.15 3.34 0.290
2
3 C:S:G=1:2:4,W/C=0.45 0.013 0.035 0.86 48.3 0.15 5.55 0.160
4
4 C:S=1:2,
W/C=0.47 0.015
0.040 0.93 39.0 0.15 4.29 0.217 4
5 C/S=1:2,
W/C=0.42 0.012 0.030 0.87 55.7 0.15 6.7 0.110 6
6 C/S=1:1.6,
W/C=0.43 0.011 0.030 0.86 56.3 0.15 6.8 0.110 6
7 C/S=1:1.6,
W/C=0.43 0.006 0.015 0.61 158.6 0.15 21.4 0.005 >20
modifier add, 3 days
0.02
0.82
0.210
-
8 C/S=1:1.6,
W/C=0.43 0.004 0.010 0.50 291.0 0.15 40.7 0.003 >20
modifier add, 28 days
0.02
2.91
0.180
2
Figure 1. Dependence of concrete water resistance characteristic from W/C and C/S
0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8
W/C-ratio
t, at/m
110
100
90
80
70
60
50
40
30
20
10
0
C/S=1:1
C/S=1:2
C/S=1:3
C/S=1:4
3 days
3 days
3 days
3 days
28 days
28 days
28 days
28 days
NATURAL SCIENCES AND NEW TECHNOLOGIES
83
The second problem - of relationship between concrete hydro-isolation capability and its
consistence has a main root in impermeability dependence from water-cement ratio (W/C). It is known
that in this dependence the critical value of W/C exists /1, 2/. With its exceeding the very rapid lost of
impermeability occurs (Fig.). If before W/C-critical right proportional dependence is noticed, after this
point it transforms to function where W/C take place in power.
There are many different W/C-critical values in various researches /1, 2/. Authors supposed that
these controversies exist because properties of aggregate were not taken into account as properties of
cement were. From this point on the base of experimental data the formulae for mortars W/C-critical
definition was derived:
W/C-cr = NV + S/C(WR) ,
where NV is the normal viscosity of cement paste defined on Vika’s device; S/C is the sand-cement ratio
in mixture; WR is the water requirement or water-holding capability of sand. According to this function a
W/C of cement mixture for hydro-isolation must be less than W/C-cr.
The same condition is actual in case of additives-modifiers using. Many additives were used in our
research work for concrete impermeability increasing. The most effectiveness was obtained with water-
saturable polymer additives such as epoxy /3/ etc. Test results showed a little effectiveness of the most
modifiers which were used in mixtures with W/C exceeding W/C-cr. Derived principals of cement hydro-
isolation designing gave a possibility of making plasters with highest water impermeability, strength,
frost and sulfate resistance. Authors patented /6/ new modifier-additive for making plasters with water
impermeability more than 16 atmospheres of hydrostatic pressure, compressive strength - >45 MPa,
adhesion - >0.5 MPa, frost resistance - >200 cycles in 5% NaCl, sulfate resistance in saturation with
concentration of sulfate-ions 10000 mg per liter. High quantity and satisfactory price of these materials
permitted their using for hydro-isolation of metro tunnels and fundaments, aerodrome covering repair /4/,
reservoirs etc.
The started research work is continued to combine full recommendations for cement hydro-
isolation and corrosion-resistant isolation designing and providing.
References
[1]
Akhverdov I.N. (1961) High strength concrete. Strojizdat, Moscow. 162p.
[2]
Verbetsky G.P. (1976) Strength and durability of concrete in water environment. Strojizdat,.
Moscow. 128p.
[3]
Gijutsu K. (1987) Concrete of high durability. Takenaka, Tokyo. 17 p.
[4]
Dashevsky E.M., Parfenov A.P. (1975) Repair of artificial aerodrome coverings. Transport,
Moscow. 232p.
[5] Powers T.C. (1955) Hydraulic pressure in concrete. Proceedings of american society of civil
engineers 81, No. 742
[6]
Seleznev G.I., Trofimov B.Y., Kramar L.Y., Korolyov A.S., Purgin A.V. (1998) Patent of Russian
Federation. No. 98101622 from 27.01.98.
Received on the 23
rd
of March 2000