The Influence of Interfacial Transition Zone on Strength of Alkali-Activated Concrete DOI: http://dx.doi.org/10.5772/intechopen.90929

#### Figure 5.

The nature of flow of corrosion processes in the alkali-activated slag compositions with high-modulus soluble silicate is mostly similar to the compositions using

The influence of the curing conditions of the specimens on the development of the corrosion processes is shown in Figures 5 and 6, where results of observation of compositions using traditional (ordinary) and alkali-activated Portland cement with crushed basalt rock are given, which cured for 90 days at t = 20, 38, and 65°С and

It is shown that in this period at t = 20°С, there are practically no any signs of corrosion in the ITZ "cement stone-aggregate" in both compositions, both with and without the metakaolin additive, being fixed (Figure 5a, b). ITZ в additive-free compositions at t = 38°С (Figures 5c, 6c) are a little bit less expressed and even less at t = 65°С (Figures 5e, 6e). The presence of the kaolin makes the ITZ more clearly

The study on microhardness of the ITZ in the concretes with crushed basalt rock showed that the metakaolin additive within the alkali-activated cements intensifies

Reducing of silicate modulus of soluble silicate down to Мs = 1 (sodium metasilicate) and the use of solution of sodium carbonate (Figure 4a, e) leads to decreasing of corrosion products in the ITZ in the additive-free compositions compared to compositions using high-modulus soluble silicate (Figure 4a). The metakaolin additive influenced positively on slowing of corrosion processes in the

SEM images of the ITZ concrete—"GBFS-alkaline component-basalt rock" (а, c, e) without metakaolin additive; (b, d, f) with metakaolin additive; 1, cement paste; 2, ITZ; 3, aggregate. Curing conditions—90 days

alkali-activated Portland cement (Figure 4a, b).

ITZ (Figure 4b, d, f).

of steam curing at t = 65°С.

Compressive Strength of Concrete

expressed (Figures 5d, f and 6d, f).

constructive corrosion (Figure 7).

RH =100%.

12

Figure 4.

SEM images of the ITZ concrete—"Portland cement-water-crushed basalt rock" (а, c, e) without metakaolin additive; (b, d, f) with metakaolin additive; 1, cement paste; 2, ITZ; 3, aggregate. Curing conditions at t = 20, 38, 65°С 90 days after steam curing.

Thus, taking into account micro photos of the cement paste/alkali-susceptible aggregate ITZ, the following conclusions can be drawn:


At the temperature t = 65°С at an age of 90 days, disturbance of the ITZ is much more clearly expressed than that at t = 38°С, chiefly, in the concretes from cement without additives. Exceptions are the concretes with perlite, where the products of corrosion, probably, could distribute in a pore space of the aggregate and, above all, perlites are represented, chiefly, by a glassy phase with rather high contents of active alumina, which can bind rather effectively free alkalis, reducing, in this way, a risk of active silica-aggregate reaction. The metakaolin additive in all cases influences positively on reducing deposits of the products of corrosion in the ITZ.

#### Figure 6.

Micro photos of the ITZ concrete—"Portland cement + soluble glass-basalt rock" (а, c, e) without metakaolin additive; (b, d, f) with metakaolin additive; 1, cement paste; 2, ITZ; 3, aggregate. Curing conditions at t = 20, 38, 65°С 90 days after steam curing.

XRD patterns of the specimens, modeling the cement stone/alkali-susceptible aggregate ITZ, are shown in Figures 8–11.

Thus, in Figure 8 the diffraction characteristic of composition on the basis of basalt and Portland cement (ordinary and alkali-activated) after their hardening in the conditions of continuous steam curing for 360 days is represented.

Corresponding to the XRD analysis data, a phase composition of the hydrated dispersions based on ordinary Portland cement and basalt (Figure 8, curve 2), modeling the ITZ, is represented, chiefly, by the following hydrate new formations: high-basic calcium silicate hydrates of the C6S3H (d = 0.335–0.284–0.246–0.237– 0.225–0.180 nm), C2SH (d = 0.284–0.270–0.246–0.190–0.180 nm) types, and lowbasic phases of the C3S2H3 (d = 0.56–0.284–0.184 nm) type. The presence of Са(ОН)2 (d = 0.487–0.311–0.261–0.193–0.180 nm) and СаСО<sup>3</sup> (d = 0.303–0.229– 0.21–0.193–0.188 nm) also was fixed. Also there are set weak lines of the C2АH4 (d = 7.17–0.376–0.266–0.258–0.246 nm) type. It is well-known that via the presence of chemically active silica and alkalis, in this case Са(ОН), which is present in the pores of the hardened concrete, a deleterious reaction "alkali-silicic acid" takes place actively with formation of alkaline metal silicate gel in the aggregate/cement stone ITZ. XRD analysis is not fixing X-ray amorphous phase of calcium silicate gel, which may be forming in the ITZ and weakening it, but taking into elemental distribution in the ITZ and extremely high expansion deformations of composite materials with basalt (up to 2.15 mm/m), such possibility exists and mostly is confirmed by the higher contents of Са and Si in the ITZ.

Use in the composition with basalt of the alkali-activated Portland cement leads to the changes in diffraction picture of the ITZ model (Figure 8, curve 3). Thus, hydration depth of Portland cement is rising, resulting in reducing intensiveness of the diffraction lines. Transformation of phase formation processes took place in the direct of formation of low-basic silicate hydrates of calcium CSH(I) (d = 0.283–0.270–0.247–0.179 nm) type and tobermorite (d = 0.560–0.307–0.299–0.283–0.227–0.208–0.183 nm). The reflexes of Са(ОН)2

Hardness of the ITZ "cement stone-basalt" (а) cement stone + water; (b) cement stone + soluble silicate; (c) GBFS + soluble silicate. Curing conditions—60 days of continuous steam curing at t = 65°С.

The Influence of Interfacial Transition Zone on Strength of Alkali-Activated Concrete

DOI: http://dx.doi.org/10.5772/intechopen.90929

In the ITZ silica, content reduces rapidly; at the same time, the quantity of aluminum and sodium is rising. Thus it is possible to make a conclusion about synthesis in the ITZ of sodium and mixed sodium-calcium alumina silicates, confirming by the results of X-ray diffractogram analysis (Figure 9, curve 2). Thus,

are totally absent.

15

Figure 7.

The Influence of Interfacial Transition Zone on Strength of Alkali-Activated Concrete DOI: http://dx.doi.org/10.5772/intechopen.90929

#### Figure 7.

XRD patterns of the specimens, modeling the cement stone/alkali-susceptible

Micro photos of the ITZ concrete—"Portland cement + soluble glass-basalt rock" (а, c, e) without metakaolin additive; (b, d, f) with metakaolin additive; 1, cement paste; 2, ITZ; 3, aggregate. Curing conditions at t = 20,

Thus, in Figure 8 the diffraction characteristic of composition on the basis of basalt and Portland cement (ordinary and alkali-activated) after their hardening in

Corresponding to the XRD analysis data, a phase composition of the hydrated dispersions based on ordinary Portland cement and basalt (Figure 8, curve 2), modeling the ITZ, is represented, chiefly, by the following hydrate new formations: high-basic calcium silicate hydrates of the C6S3H (d = 0.335–0.284–0.246–0.237– 0.225–0.180 nm), C2SH (d = 0.284–0.270–0.246–0.190–0.180 nm) types, and lowbasic phases of the C3S2H3 (d = 0.56–0.284–0.184 nm) type. The presence of Са(ОН)2 (d = 0.487–0.311–0.261–0.193–0.180 nm) and СаСО<sup>3</sup> (d = 0.303–0.229– 0.21–0.193–0.188 nm) also was fixed. Also there are set weak lines of the C2АH4 (d = 7.17–0.376–0.266–0.258–0.246 nm) type. It is well-known that via the presence of chemically active silica and alkalis, in this case Са(ОН), which is present in the pores of the hardened concrete, a deleterious reaction "alkali-silicic acid" takes place actively with formation of alkaline metal silicate gel in the aggregate/cement stone ITZ. XRD analysis is not fixing X-ray amorphous phase of calcium silicate gel, which may be forming in the ITZ and weakening it, but taking into elemental distribution in the ITZ and extremely high expansion deformations of composite materials with basalt (up to 2.15 mm/m), such possibility exists and mostly is

the conditions of continuous steam curing for 360 days is represented.

confirmed by the higher contents of Са and Si in the ITZ.

aggregate ITZ, are shown in Figures 8–11.

38, 65°С 90 days after steam curing.

Compressive Strength of Concrete

Figure 6.

14

Hardness of the ITZ "cement stone-basalt" (а) cement stone + water; (b) cement stone + soluble silicate; (c) GBFS + soluble silicate. Curing conditions—60 days of continuous steam curing at t = 65°С.

Use in the composition with basalt of the alkali-activated Portland cement leads to the changes in diffraction picture of the ITZ model (Figure 8, curve 3). Thus, hydration depth of Portland cement is rising, resulting in reducing intensiveness of the diffraction lines. Transformation of phase formation processes took place in the direct of formation of low-basic silicate hydrates of calcium CSH(I) (d = 0.283–0.270–0.247–0.179 nm) type and tobermorite (d = 0.560–0.307–0.299–0.283–0.227–0.208–0.183 nm). The reflexes of Са(ОН)2 are totally absent.

In the ITZ silica, content reduces rapidly; at the same time, the quantity of aluminum and sodium is rising. Thus it is possible to make a conclusion about synthesis in the ITZ of sodium and mixed sodium-calcium alumina silicates, confirming by the results of X-ray diffractogram analysis (Figure 9, curve 2). Thus,

Figure 8.

XRD patterns of the ITZ of model systems: (1) "Portland cement-basalt"; (2) "Portland cement-basalt-water"; (3) "Portland cement-basalt-soluble silicate." Curing conditions—360 days at t = 65 3°С and RH = 100%.

#### Figure 9.

XRD patterns of the ITZ of model systems: (1) "Portland cement-metakaolin-basalt"; (2) "Portland cementmetakaolin-basalt-water"; (3) "Portland cement-metakaolin-basalt-soluble silicate." Curing conditions— 360 days at t = 65 3°С and RH = 100%.

at curve 3 appears lines of the Na2OAl2O34SiO22H2O (d = 0.56–0.343–0.293– 0.252–0.174 nm) and 2Na2O2CaO5Al2O310SiO210H2O (d = 0.654–0.467–0.353– 0.283–0.270 nm) phases.

hydroxide ions, significantly reduces risk of corrosion processes in the ITZ in destructive form. This correlates well with the data in [9], corresponding to which the presence of active alumina in the Portland cement stone significantly reduces

XRD patterns of the ITZ of model systems: (1) "Portland cement-metakaolin-perlite"; (2) "Portland cementwater-metakaolin-perlite"; (3) "Portland cement-soluble silicate + metakaolin-perlite." Curing conditions—

XRD patterns of the ITZ of model systems: (1) "Portland cement-perlite"; (2) "Portland cement-perlite-water"; (3) "Portland cement-perlite-soluble silicate." Curing conditions—360 days at t = 65 3°С and RH = 100%.

The Influence of Interfacial Transition Zone on Strength of Alkali-Activated Concrete

DOI: http://dx.doi.org/10.5772/intechopen.90929

The last consideration is absolutely confirmed in the case of replacement of ordinary Portland cement by alkali-activated Portland cement with the metakaolin additive. Thus,

alkali concentration in the pore space of Portland cement stone.

Figure 10.

Figure 11.

17

360 days at t = 65 3°С and RH = 100%.

Introducing of the metakaolin additive to ordinary Portland cement mixes with water significantly not changing diffraction picture (Figure 9, curve 3). However, as it seems from Figure 9, in the ITZ significantly reducing content of Са, and also The Influence of Interfacial Transition Zone on Strength of Alkali-Activated Concrete DOI: http://dx.doi.org/10.5772/intechopen.90929

Figure 10.

XRD patterns of the ITZ of model systems: (1) "Portland cement-perlite"; (2) "Portland cement-perlite-water"; (3) "Portland cement-perlite-soluble silicate." Curing conditions—360 days at t = 65 3°С and RH = 100%.

#### Figure 11.

XRD patterns of the ITZ of model systems: (1) "Portland cement-metakaolin-perlite"; (2) "Portland cementwater-metakaolin-perlite"; (3) "Portland cement-soluble silicate + metakaolin-perlite." Curing conditions— 360 days at t = 65 3°С and RH = 100%.

hydroxide ions, significantly reduces risk of corrosion processes in the ITZ in destructive form. This correlates well with the data in [9], corresponding to which the presence of active alumina in the Portland cement stone significantly reduces alkali concentration in the pore space of Portland cement stone.

The last consideration is absolutely confirmed in the case of replacement of ordinary Portland cement by alkali-activated Portland cement with the metakaolin additive. Thus,

at curve 3 appears lines of the Na2OAl2O34SiO22H2O (d = 0.56–0.343–0.293– 0.252–0.174 nm) and 2Na2O2CaO5Al2O310SiO210H2O (d = 0.654–0.467–0.353–

XRD patterns of the ITZ of model systems: (1) "Portland cement-metakaolin-basalt"; (2) "Portland cementmetakaolin-basalt-water"; (3) "Portland cement-metakaolin-basalt-soluble silicate." Curing conditions—

XRD patterns of the ITZ of model systems: (1) "Portland cement-basalt"; (2) "Portland cement-basalt-water"; (3) "Portland cement-basalt-soluble silicate." Curing conditions—360 days at t = 65 3°С and RH = 100%.

Introducing of the metakaolin additive to ordinary Portland cement mixes with water significantly not changing diffraction picture (Figure 9, curve 3). However, as it seems from Figure 9, in the ITZ significantly reducing content of Са, and also

0.283–0.270 nm) phases.

360 days at t = 65 3°С and RH = 100%.

Figure 9.

16

Figure 8.

Compressive Strength of Concrete

It is known that there exist no absolutely inert aggregates. All aggregates more or less react to the cement stone. But in some cases in the ITZ, destructive processes took place, with "negative effect of corrosion," meaning with gradual destruction, and in other cases—structure formation processes with the "positive effect of corrosion," meaning without destruction and moreover with improvement state

The Influence of Interfacial Transition Zone on Strength of Alkali-Activated Concrete

In the alkali-activated cement concretes, especially cements containing the metakaolin additive, at the surface of the aggregates appears a dense film of new formation mostly represented by alumina silicate hydrate composition, which prevents further admission of new portions of alkalis to the aggregate. Thus a way, due to the partial corrosion of aggregate at the initial stages, on its surface it is forming

On the contrary to alkali-activated cement concretes, in ordinary Portland cement concretes, gel-like new formations in the ITZ act as semipermeable films. That means that alkalis are able to easy penetrate through new formations to aggregate grain and new products of corrosion are accumulating under that film, increasing osmotic pressure and leading to the degradation of ITZ and destruction

Thus, in the result of provided studies, the effectiveness of introduction into the alkali-activated cement compositions with alkali-susceptible aggregates of active alumina represented by metakaolin was proven, which makes it possible to bond extra alkalis effectively and regulate structure formation processes in the cement stone/alkali-susceptible aggregate ITZ, using partial surface corrosion of the aggre-

The results of determination of compressive and bending strengths of the concrete specimens made using the Portland cement as well as their autogenous

Taking into account data from the Table 4, depending upon curing conditions of compositions and using as a criteria corrosion in the ITZ and the admissible values of expansion of the specimens not exceeding 1 mm/m (0.1%) [42] with simultaneous consideration of their strength characteristics, the following conclu-

Curing of Portland cement specimens at t = 20°C more or less considerable corrosion in all control ages (28–180 days) for all composition is not fixed, not depending upon composition of the specimens. Strength (compressive and bending) characteristics of the specimens in these curing conditions at the given ages

Reducing of shrinkage in the concretes made with basalt aggregates at an age of

The metakaolin additive considerably decreased autogenous deformations of shrinkage of the Portland cement containing specimens compared to additive-free compositions, losing at the same time strength of the specimens compared to

90 and 180 days compared to that in 28-day age is set as insignificant, which witnesses the beginning of a reverse process, meaning free development of corro-

sion processes in the ITZ of the concretes made using aggregates.

gate for synthesis in the interface of the zeolite-like hydrate phases.

3.2 Physical-mechanical properties of concretes

3.2.1 Concrete mixture "Portland cement + water"

3.2.1.1 Curing conditions: t = 20 °C, RH = 100%

deformations are given in Table 4.

sions can be drawn.

tended to increase.

additive-free compositions.

19

of the ITZ.

of concrete in general.

protective dense and impermeable capsule.

DOI: http://dx.doi.org/10.5772/intechopen.90929

#### Figure 12.

XRD patterns of the ITZ of model systems: (1) "GBFS-basalt"; (2) "GBFS-soluble silicate-basalt"; (3) "GBFSmetakaolin-basalt"; (4) "GBFS-soluble silicate-metakaolin-basalt." Curing conditions—360 days at t = 65 3°С and RH = 100%.

according to Figure 9, curve 2, hydration of Portland cement deepens, forming finegrained crystalline structure. The zeolite-like new formations—Na2OAl2O34SiO22H2O (d = 0.561–0.343–0.293–0.251–0.174 nm), Na2OAl2O33SiO22H2O (d = 6.53–5.87–4.36– 2.86–2.19 nm) and 2Na2O2CaO5Al2O310SiO210H2O (d = 0.654–0.467–0.353–0.285– 0.269 nm)—are synthesizing in the ITZ, which is proven by increasing of Al and Na and reducing of Са content in the ITZ.

Use of alkali-activated slag cement is characterized by the more active synthesis in the alkali-susceptible aggregate/cement stone ITZ of the low-basic hydrate new formations as silicate, so as alumina silicate composition (Figure 12). This process becomes greatly active exactly in the presence of metakaolin additive. Thus, in the model system of the ITZ "alkali-activated slag cement stone-basalt aggregate," there are fixed zeolite-like new formations of the Na2OAl2O34SiO22H2O (d = 0.56– 0.343–0.293–0.252–0.174 nm) and Na2OAl2O33SiO22H2O (d = 0.653–0.587– 0.436–0.286–0.219 nm) types as well as low-basic silicate hydrates CSH(I) (d = 0.530–0.304–0.28–0.181 nm) and xonotlite 6CaO6SiO2H2O (d = 0.425–0.389– 0.368–0.330–0.307–0.284–0.270–0.204–0.195 nm). That is confirmed by analysis of the elemental distribution in the ITZ of the taken composition (Figure 12). Thus, in the presence of metakaolin additive, reflexes of the mentioned above new formations became sharper. Moreover, there is fixed new formation 2Na2O2CaO3Al2O310SiO212H2O type (d = 0.715–0.495–0.412–0.314–0.266 nm), which is also classified as zeolites (Figure 12, curve 4).

Metakaolin additive reduces Ca content not only in the ITZ but also in cement stone, showing possibility of synthesis of the aluminosilicate hydrates of mixed sodium-calcium composition not only in the ITZ but in the cement matrix as well.

### The Influence of Interfacial Transition Zone on Strength of Alkali-Activated Concrete DOI: http://dx.doi.org/10.5772/intechopen.90929

It is known that there exist no absolutely inert aggregates. All aggregates more or less react to the cement stone. But in some cases in the ITZ, destructive processes took place, with "negative effect of corrosion," meaning with gradual destruction, and in other cases—structure formation processes with the "positive effect of corrosion," meaning without destruction and moreover with improvement state of the ITZ.

In the alkali-activated cement concretes, especially cements containing the metakaolin additive, at the surface of the aggregates appears a dense film of new formation mostly represented by alumina silicate hydrate composition, which prevents further admission of new portions of alkalis to the aggregate. Thus a way, due to the partial corrosion of aggregate at the initial stages, on its surface it is forming protective dense and impermeable capsule.

On the contrary to alkali-activated cement concretes, in ordinary Portland cement concretes, gel-like new formations in the ITZ act as semipermeable films. That means that alkalis are able to easy penetrate through new formations to aggregate grain and new products of corrosion are accumulating under that film, increasing osmotic pressure and leading to the degradation of ITZ and destruction of concrete in general.

Thus, in the result of provided studies, the effectiveness of introduction into the alkali-activated cement compositions with alkali-susceptible aggregates of active alumina represented by metakaolin was proven, which makes it possible to bond extra alkalis effectively and regulate structure formation processes in the cement stone/alkali-susceptible aggregate ITZ, using partial surface corrosion of the aggregate for synthesis in the interface of the zeolite-like hydrate phases.

### 3.2 Physical-mechanical properties of concretes

#### 3.2.1 Concrete mixture "Portland cement + water"

The results of determination of compressive and bending strengths of the concrete specimens made using the Portland cement as well as their autogenous deformations are given in Table 4.

Taking into account data from the Table 4, depending upon curing conditions of compositions and using as a criteria corrosion in the ITZ and the admissible values of expansion of the specimens not exceeding 1 mm/m (0.1%) [42] with simultaneous consideration of their strength characteristics, the following conclusions can be drawn.

#### 3.2.1.1 Curing conditions: t = 20 °C, RH = 100%

Curing of Portland cement specimens at t = 20°C more or less considerable corrosion in all control ages (28–180 days) for all composition is not fixed, not depending upon composition of the specimens. Strength (compressive and bending) characteristics of the specimens in these curing conditions at the given ages tended to increase.

Reducing of shrinkage in the concretes made with basalt aggregates at an age of 90 and 180 days compared to that in 28-day age is set as insignificant, which witnesses the beginning of a reverse process, meaning free development of corrosion processes in the ITZ of the concretes made using aggregates.

The metakaolin additive considerably decreased autogenous deformations of shrinkage of the Portland cement containing specimens compared to additive-free compositions, losing at the same time strength of the specimens compared to additive-free compositions.

according to Figure 9, curve 2, hydration of Portland cement deepens, forming finegrained crystalline structure. The zeolite-like new formations—Na2OAl2O34SiO22H2O (d = 0.561–0.343–0.293–0.251–0.174 nm), Na2OAl2O33SiO22H2O (d = 6.53–5.87–4.36– 2.86–2.19 nm) and 2Na2O2CaO5Al2O310SiO210H2O (d = 0.654–0.467–0.353–0.285– 0.269 nm)—are synthesizing in the ITZ, which is proven by increasing of Al and Na and

XRD patterns of the ITZ of model systems: (1) "GBFS-basalt"; (2) "GBFS-soluble silicate-basalt"; (3) "GBFSmetakaolin-basalt"; (4) "GBFS-soluble silicate-metakaolin-basalt." Curing conditions—360 days at

Use of alkali-activated slag cement is characterized by the more active synthesis in the alkali-susceptible aggregate/cement stone ITZ of the low-basic hydrate new formations as silicate, so as alumina silicate composition (Figure 12). This process becomes greatly active exactly in the presence of metakaolin additive. Thus, in the model system of the ITZ "alkali-activated slag cement stone-basalt aggregate," there are fixed zeolite-like new formations of the Na2OAl2O34SiO22H2O (d = 0.56– 0.343–0.293–0.252–0.174 nm) and Na2OAl2O33SiO22H2O (d = 0.653–0.587– 0.436–0.286–0.219 nm) types as well as low-basic silicate hydrates CSH(I)

(d = 0.530–0.304–0.28–0.181 nm) and xonotlite 6CaO6SiO2H2O (d = 0.425–0.389– 0.368–0.330–0.307–0.284–0.270–0.204–0.195 nm). That is confirmed by analysis of the elemental distribution in the ITZ of the taken composition (Figure 12). Thus, in the presence of metakaolin additive, reflexes of the mentioned above new for-

2Na2O2CaO3Al2O310SiO212H2O type (d = 0.715–0.495–0.412–0.314–0.266 nm),

Metakaolin additive reduces Ca content not only in the ITZ but also in cement stone, showing possibility of synthesis of the aluminosilicate hydrates of mixed sodium-calcium composition not only in the ITZ but in the cement matrix as well.

mations became sharper. Moreover, there is fixed new formation

which is also classified as zeolites (Figure 12, curve 4).

reducing of Са content in the ITZ.

t = 65 3°С and RH = 100%.

Compressive Strength of Concrete

Figure 12.

18


L/S, liquid-to-cement ratio.

2 A minus sign (), shrinkage; plus sign (+), expansion of the specimens in relation to a basic measurement.

#### Table 4.

Strength characteristics and autogenous deformations of the concretes using cement system "OPC + water" vs. curing conditions and concrete mixture design.

3.2.1.2 Curing conditions: t = 65°C, RH = 100%

The most considerable changes, so as it was expected, were found in the structure of the ITZ of the specimens made using Portland cement curing at t = 65°С. So, at an age of 180 days in the concrete specimens with crushed basalt rock without admixture, extremely high (dangerous) values of expansion—1.08–1.17 mm/m were found, reflexing in some drop of strength characteristics, both compressive

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

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

"Portland cement + soluble silicate + crushed basalt rock"

65 115.5

65 111.1

"Portland cement + soluble silicate + chopped off-size basalt fibers"

65 93.9

65 90.9

65 88.0

65 88.9

"Portland cement + high-modulus soluble silicate + expanded perlite"

65 44.4

65 44.2

5.1

The Influence of Interfacial Transition Zone on Strength of Alkali-Activated Concrete

7.0

5.0

7.1

8.9

10.3

5.8

11.2

6.1

6.8

6.2

7.1

2.0

2.7

2.1

2.7

"Portland cement + high-modulus soluble silicate + crushed perlite rock"

354 — 20 59.8

DOI: http://dx.doi.org/10.5772/intechopen.90929

354 Metakaolin 20 92.1

454 — 20 44.0

454 Metakaolin 20 62.4

51 — 20 75.2

52 Metakaolin 20 73.7

36 — 20 39.9

37 Metakaolin 20 37.7

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

vs. curing conditions and concrete mixture design.

1

2

21

Table 5.

L/S, liquid-to-cement ratio.

bending, MPa, age, days

76.0 4.8

128.1 6.5

106.0 5.3

126.9 7.7

69.6 8.7

93.5 11.4

73.3 6.9

103.8 12.0

> 79.3 5.9

91.0 7.4

76.1 6.2

93.0 7.3

42.3 2.3

45.5 2.5

43.5 2.2

47.0 2.8

28 90 180 28 90 180

128.2 6.4

132.0 6.4

117.7 6.3

130.0 7.3

> 81.9 10.9

88.7 9.1

88.0 9.3

109.8 11.8

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

0.63 0.55 0.51

+0.18 +0.70 +0.81

0.61 0.49 0.36

+0.09 +0.45 +0.48

0.47 0.41 0.38

+0.12 +0.63 +0.72

0.58 0.60 0.57

+0.10 +0.44 +0.46

— 1.10 1.15 —

— +0.16 +0.18 —

— 0.64 0.67 —

— 0.04 +0.10 —

— 1.22 1.26 —

— 0.68 0.66 —

— 0.79 0.83 —

— 0.38 0.34 —


The Influence of Interfacial Transition Zone on Strength of Alkali-Activated Concrete DOI: http://dx.doi.org/10.5772/intechopen.90929

Table 5.

Strength characteristics and autogenous deformations of the concretes using cement system "OPC + soluble glass" vs. curing conditions and concrete mixture design.

at an age of 180 days in the concrete specimens with crushed basalt rock without admixture, extremely high (dangerous) values of expansion—1.08–1.17 mm/m were found, reflexing in some drop of strength characteristics, both compressive

3.2.1.2 Curing conditions: t = 65°C, RH = 100%

curing conditions and concrete mixture design.

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

"Portland cement + water + crushed basalt rock" 36 — 20 70.1

Compressive Strength of Concrete

38 Metakaolin 20 64.2

45 — 20 39.8

48 Metakaolin 20 45.4

53 Metakaolin 20 66.4

"Portland cement + water + expanded perlite" 37 — 20 31.0

38 Metakaolin 20 29.2

1

2

20

Table 4.

L/S, liquid-to-cement ratio.

"Portland cement + water + crushed perlite rock" 51 — 20 68.2

bending, MPa, age, days

76.0 9.3

72.8 9.2

75.2 6.7

56.3 6.9

40.8 12.2

50.3 7.8

50.8 12.1

40.0 7.9

76.0 9.0

72.8 9.0

73.1 6.9

54.3 6.9

34.1 2.0

37.2 1.9

35.0 2.3

37.7 2.3

77.7 11.1

70.9 9.0

76.6 7.0

52.0 6.7

45.9 11.1

48.4 7.9

52.2 11.6

38.8 7.2

7.1

9.4

6.8

7.2

10.2

11.9

9.8

8.9

7.0

9.3

6.8

7.1

1.4

2.5

2.0

2.4

A minus sign (), shrinkage; plus sign (+), expansion of the specimens in relation to a basic measurement.

65 75.9

65 69.0

"Portland cement + water + chopped waste of basalt fiber production"

65 52.7

65 46.4

65 73.8

65 53.0

65 36.4

65 36.1

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

0.50 0.44 0.40

+0.15 +0.69 +1.08

0.41 0.30 0.23

+0.10 +0.52 +0.74

0.46 0.41 0.30

+0.11 +0.55 +0.99

0.38 0.34 0.20

+0.13 +0.48 +0.59

— 0.51 0.56 —

— +0.11 +0.23 —

— 0.48 0.49 —

— +0.07 +0.18 —

— 0.65 0.70 —

— 0.41 0.35 —

— 0.53 0.59 —

— 0.29 0.27 —

28 90 180 28 90 180

The most considerable changes, so as it was expected, were found in the structure of the ITZ of the specimens made using Portland cement curing at t = 65°С. So,

Strength characteristics and autogenous deformations of the concretes using cement system "OPC + water" vs.

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

3.2.2 Concrete mixture "Portland cement + soluble silicate"

varied depending on composition and curing conditions.

depending on composition and curing conditions.

3.2.3 Concrete mixture "GBFS + soluble silicate"

DOI: http://dx.doi.org/10.5772/intechopen.90929

—0.46–0.81 mm/m (Table 5).

4. Conclusions

natural aggregates.

23

stable and without any drops (Table 6).

border between the cement stone and the aggregate.

The results of determination of compressive and bending strengths of the concrete specimens made using the alkali-activated Portland cement as well as their autogenous deformations are given in Table 5. The characteristics are varied

The Influence of Interfacial Transition Zone on Strength of Alkali-Activated Concrete

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

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

A character of strength gain of all compositions for all temperature regimes is

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

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.

firmed that Al2O3 plays a determining role in these constructive processes.

It is established that the positive result of the processes of such interaction of the

Comparative studies of the processes of the structure formation of the ITZ in the alkali-activated cement concretes with different alkali-susceptible aggregates con-

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


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

#### Table 6.

Strength characteristics and autogenous deformations of the concretes using cement system "GGBS + soluble glass" vs. curing conditions and concrete mixture design.

The Influence of Interfacial Transition Zone on Strength of Alkali-Activated Concrete DOI: http://dx.doi.org/10.5772/intechopen.90929

### 3.2.2 Concrete mixture "Portland cement + soluble silicate"

The results of determination of compressive and bending strengths of the concrete specimens made using the alkali-activated Portland cement as well as their autogenous deformations are given in Table 5. The characteristics are varied depending on composition and curing conditions.
