Proceedings of the International rilem conference Materials, Systems and Structures in Civil Engineering 2016

3

International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

Purpose of the study were comparative tests of volume stability and to reveal specific features 

of corrosion processes in case of alkali- susceptible aggregates taking place in the concretes 

made from traditional portland cement and alkali activated portland cement and to study a 

possibility to prevent destructive processes in concretes made from cements with the 

increased contents of alkalis due to introduction into the cement composition of Al

2

O

3

-

containing additive   metakaolin.

 

 

 

2.  Raw materials and testing technique  

 

Used in the studies as aluminosilicate component of the alkali activated portland cement was 

a strength class 42,5 ordinary portland cement. A specific surface of the portland cement was 

under control with the help of a Blaine apparatus and varied within the range of 

320…350 m

2

/kg. 

 

 

In testing compressive strength, a basalt rock (fraction   2.50 mm) was used as aggregate. A 

glassy bar from cast basalt was used to simulate an interfacial transition zone and to study it. 

A ratio between the cement and aggregate was taken as 1:3.

 

 

Used as alkaline activator in the cement was sodium soluble glass (SG) in a form of solution 

with silicate modulus Ms=2.87 and  =1300 kg/m

3

.

 

 

A metakaolin was used as an active mineral additive. A quantity of the metakaolin additive in 

the cement was 15% by mass. A specific surface of the metakaolin was of around 1860 m

2

/kg. 

Chemical composition of raw materials is given in Table 1. 

 

Table 1: Chemical composition of raw materials. 

Raw material 

Oxide content, % by mass 

SiO

2

 

Al

2

O

3

 

Fe

2

O

3

 

MnO 

CaO 

MgO 

K

2

O 

Na

2

O 

SO

3

 

LOI 

Basalt (natural rock) 

50.20  14.00  6.34  0.24  8.35  6.60  0.71  2.27  0.08  0.55 

cast basalt (from melt) 

50.00  15.30  6.23  0.30  9.21  5.58  0.77  2.18  0.15 

 

portland cement 

21.80  5.30  4.90 

  65.90 11.10 

0.22 

0.99  0.20 

metakaolin 55.10 

35.40 

4.27 

 

3.01 0.92 

 

 

0.28 0.07 

 

The interfacial transition zone was studied with the help of a scanning electron microscopy. 

Thin sections were cut from the specimens “cement-aggregate” – 1:2 to study an interfacial 

transition zone. Above, elemental distribution in the interfacial transition zone and its 

microhardness were studied. 

 

The study of hydration products in the interfacial transition zone between the alkali- 

susceptible aggregate and the cement stone was done with the use of X-ray analysis. One 

more model of the interfacial transition zone (the specimens containing a mix of ground basalt 

powder and the cement taken in a ratio 1:1 mixed with the soluble glass) was used in the 

study. Curing conditions   360 days of continuous treatment at t= 38 3 º  and RH= 100%. 

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4

International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

 

Determination of strength was done on beam specimens 25 25 255 mm (cement: aggregate= 

1:2 by mass). Two days after the specimens were taken from the molds and placed for further 

hardening at t = 38 º  and RH  100% into thermostats.  

 

Linear deformations were measured using a digital strain gauge to an accuracy of up to 

0.01 mm. Basic measurement was taken 2 days after the molding immediately after the 

specimens were taken from the molds. Curing conditions   the same as used in the 

determination of strength.

 

 

 

3.  Results and discussion 

 

3.1  Volume stability and strength. 

The results of changes in strength characteristics and deformations of the specimens are given 

in Table 2.

 

 

Table 2: Strength and deformations of the specimens made from portland cement.  

Nos Composition 

Compressive/flexural strength, MPa, 

after, days 

Deformations: shrinkage ( ) 

/expansion (+), mm/m, after, days 

28  90  180 270 360  28  90  180 270 360 

1 

portland cement 

+ H

2

O 

72.30 

7.30 

74.30 

10.30 

74.00 

10.00 

75.30 

8.90 

73.00 

8.10 

0.41 

0.18 

0.02  +0.06 +0.14 

2 

portland cement 

+ H

2

O + MK 

67.00 

6.40 

64.20 

7.10 

66.80 

7.00 

67.70 

6.80 

67.00 

6.90 

0.16 

0.10 

0.06 

0.02  +0.10 

3 

portland cement 

+ SG  

80.30 

7.10 

109.70 

6.70 

133.30 

6.30 

132.80 

6.20 

130.30 

6.00 

0.20  +0.09 +0.21 +0.28 +0.30 

4 

portland cement 

+ SG + MK 

104.40 

6.30 

119.80 

7.20 

127.20 

7.50 

130.70 

7.40 

131.00 

7.60 

0.19 

0.10 

0.08 

0.03 

0.01 

Remarks: 

1.

 

SG   soluble glass with  s = 2.87 and   = 1300 kg/m

3

. 

2.

 

MK   metakaolin in a quantity of 15% of the total cement mass. 

 

As is clearly seen from the results given in Table 2, values of the expansion deformation of 

the specimens tend to decrease with introduction into the cement composition of active Al

2

O

3

 

within the metakaolin.  

 

It is clearly seen that with increase in quantity of active Al

2

O

3

 even with the increased 

contents of Na

2

O in the mixtures the specimens maintained their volume stability (Table 3). 

 

The specimens without metakaolin additive (Compositions 2 and 4) after one year of storage 

have the highest values of expansion compared to those with metakaolin additive. Above, as a 

result of expansion the first specimens showed a tendency to continuous decline of strength 

characteristics (Compositions 1 and 3), whereas the specimens 2 and 4 showed a tendency to 

constantly increase of  strength characteristics.

 

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