3.2.3 Concrete mixture "GBFS + soluble silicate"

The results of determination of compressive and bending strengths of the concrete specimens made using the alkali-activated slag cement with high-modulus soluble silicate, sodium metasilicate, and sodium carbonate as alkaline activators as well as their autogenous deformations are given in Table 6. The characteristics are varied depending on composition and curing conditions.

The development of shrinkage/expansion deformations of the concrete containing "GBFS + soluble silicate" as cement and crushed basalt rock as aggregate suggested to conclude that at almost complete similarity of regularities, they differ from that made using the alkali-activated Portland cement only in absolute values of characteristics—those are in some cases a little bit higher. A value of maximal expansion of the concrete containing "GBFS + soluble silicate" as cement and crushed basalt rock as aggregate within the ranges of experiment was 0.45– 0.91 mm/m (Table 6) and those in the case of the alkali-activated Portland cement —0.46–0.81 mm/m (Table 5).

A character of strength gain of all compositions for all temperature regimes is stable and without any drops (Table 6).

## 4. Conclusions

and bending, of the specimens compared to those concretes of 28-day age at t = 65°С. The addition of the metakaolin additive allowed to reduce the expansion

6.1

8.0

6.2

8.8

10.7

12.0

12.1

10.8

5.9

6.9

6.0

7.2

1.7

2.5

2.0

2.1

"GBFS + high-modulus soluble silicate + glassy waste product of basalt fibers production"

bending, MPa, age, days

78.0 6.0

116.0 7.4

> 95.0 6.3

115.0 8.2

94.9 10.9

100.3 9.0

> 88.7 11.9

111.0 11.3

85.0 5.8

97.0 7.3

82.0 6.1

98.9 7.2

40.2 2.2

43.3 2.4

40.3 2.3

44.8 2.5

Strength characteristics and autogenous deformations of the concretes using cement system "GGBS + soluble

Shrinkage (expansion) deformations, mm/m, age, days<sup>2</sup>

1.21 1.01 0.78

+0.58 +0.88 +0.91

1.19 0.85 0.73

+0.44 +0.46 +0.47

0.83 0.86 0.82

+0.63 +0.86 +0.87

0.66 0.63 0.65

+0.41 +0.44 +0.45

— 1.17 1.20 —

— +0.12 +0.15 —

— 0.71 0.73 —

— 0.13 +0.09 —

— 1.33 1.40 —

— 0.75 0.67 —

— 0.87 0.89 —

— 0.37 0.34 —

28 90 180 28 90 180

108.0 7.2

120.1 7.0

103.7 6.6

119.8 9.0

95.0 11.1

97.2 8.9

99.8 12.0

115.2 11.2

values at an age of 180 days to the safer level—0.74 mm/m.

L/S<sup>1</sup> Additive Temperature, °С Strength compressive/

"GBFS + high-modulus soluble silicate + crushed basalt stone"

65 103.3

65 100.3

65 102.0

65 108.0

65 94.8

65 95.2

65 42.4

65 42.1

"GBFS + high-modulus soluble silicate + expanded perlite"

"GBFS + high-modulus soluble silicate + crushed perlite rock"

0.36 — 20 61.7

Compressive Strength of Concrete

0.36 Metakaolin 20 81.3

0.45 — 20 92.0

0.45 Metakaolin 20 78.0

0.50 — 20 81.0

0.51 Metakaolin 20 79.8

0.35 — 20 37.0

0.36 Metakaolin 20 35.4

A minus sign (), shrinkage; plus sign (+), expansion.

glass" vs. curing conditions and concrete mixture design.

1

2

22

Table 6.

L/S, liquid-to-cement ratio.

The processes of structure formation in the ITZ "alkali-activated cementartificial aggregate" are studied. It is set that the interface between them practically disappears, which indicates about penetration of the elements and blurring the border between the cement stone and the aggregate.

It is established that the positive result of the processes of such interaction of the substances of cement elements and aggregate is the formation of alkaline and alkaline-alkali-earth alumina silicate hydrates—analogs of natural zeolites, transforming a destructive process of concrete corrosion into the constructive.

Comparative studies of the processes of the structure formation of the ITZ in the alkali-activated cement concretes with different alkali-susceptible aggregates confirmed that Al2O3 plays a determining role in these constructive processes.

It is shown that the addition of the metakaolin additive as an Al2O3-containing additive provides inhibition of alkaline corrosion processes, which is confirmed by long-term testing of strength characteristics and deformation (shrinkage/expansion) of concretes using different alkali-activated cements and alkali-susceptible natural aggregates.

Compressive Strength of Concrete
