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

13

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 

 

Table 1: Chemical composition of AACs components. 

Component 

Oxides, % by mass 

LOI 

SiO

2

 Al

2

O

3

 Fe

2

O

3

 MnO  MgO  CaO  N

2

O SO

3

 

clinker 21.30 

5.70 

4.62 

- 

1.20 

65.90 

0.30 

0.86 

0.12 

slag 39.00 

5.90 

0.30 

0.50 

5.82 

46.94 

- 

1.54 

- 

 

Soda ash (Na

2

CO

3

) and sodium metasilicate pentahydrate (Na

2

SiO

3

5

2

O) were used as 

alkaline components. In the production of the AACs under "all- in- one" technology (alkaline 

components in the form of solids) it is required to use sodium lignosulfonates (further, LST) 

in order to provide the required setting times and strength. In order to intensify a grinding 

process and to prevent sorption of moisture from air and preserve properties of the AAC an 

admixture of ethyl hydro-siloxane polymer was also used. 

 

The AAC compositions are shown in Table 2. Fineness of the AACs (measured as specific 

surface by Blaine) was 4500 cm

2

/g. The contents of alkali metal compounds (alkaline 

activators) were taken over 100% of the aluminosilicate components in accordance with [13].  

In order to change a consistency of the AAC concrete mixtures from class S1 (that of the 

reference composition) to class S4 at ambient temperature of 20±2 ºC, complex admixtures 

(further, CA) based on LST in combination with corresponding plasticizing admixtures (taken 

in quantities of 1.5% by the AAC) were used.  

 

The plasticizing admixtures varied in nature of main active substances: 1 – surfactant based on 

polyacrylate esters, Type PA (traditional superplasticizer "Dynamon SR 2”, Mapei); 2 - 

surfactant based on polyethers (polyethylene glycol “PEG-400”, JSC "Barva"); 3 - surfactant 

based on sodium gluconate (“Mapetard SD 2000”, Mapei), which is traditionally used as a 

retarder. 

 

Table 2: Compositions of the AAC. 

# of composition 

Basic composition 

1 

50% slag, 50% clinker, 2% Na

2

CO

3

, 1% LST 

2 

50% slag, 50% clinker, 3% Na

2

SiO

3

5

2

O, 1% LST 

3 

69% slag, 31% clinker, 2,5% Na

2

CO

3

, 1% LST 

4 

69% slag, 31% clinker, 3,5% Na

2

SiO

3

5

2

O, 1% LST 

5 

88% slag, 12% clinker, 3% Na

2

CO

3

, 1% LST 

6 

100% slag, 4.7% Na

2

CO

3

, 0.8% LST 

 

In these studies in order to determine the influence of variables (cement composition and 

nature of main active substance of admixtures) on capillary porosity and freeze/thaw 

resistance of the AAC concrete, one cement composition was chosen. The standard 

composition of the AAC concrete was taken in accordance with [14], kg/m

3

: cement - 350; 

silica sand - 740; granite gravel: 330 (5/10) and 780 (10/20). 

 

Water absorption and porosity of the AAC concretes were studied in accordance with 

methodology of the national standard of Ukraine [15]. According to this method, the concrete 

cubes (100 mm) after 28 days were dried up to a constant weight at t= 105±10 °C. Then, the 

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14

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 

 

specimens were saturated with water until a constant weight would be obtained at t= 20±2 °C. 

The values of porosity were calculated from the values of average density and water 

absorption of the concrete specimens.  

 

Freeze/thaw resistance was studied in accordance with third test method prescribed by the 

national standard of Ukraine [16]. According to this accelerated method, the concrete cubes 

(100 mm) were saturated with a 5% solution of NaCl at t= 18±2 °C and after that were 

subjected to freezing at t= -50 °C. Thawing was done in a 5% solution of NaCl. A class of 

concrete in freeze/thaw resistance was designated as a number of alternate freezing and 

thawing at which a mean compressive strength decreased by no more than 5%. The 

freeze/thaw resistance of concrete was assessed by the correspondence between permissible 

number of freezing-thawing cycles on the used accelerated method and on first (basic) method 

prescribed in mentioned standard. 

 

 

3. Research 

results 

 

As a result of the study a conclusion was drawn that changes in slag contents, type and 

content of alkaline component affected porosity and consequently freeze/thaw resistance of 

the AAC concrete depending on the nature of main active substance of plasticizer. 

 

The use of polyester - based CA in the AAC concretes containing 50% of slag and 2% of soda 

ash (composition #1) lead to slight increase in water absorption and open capillary porosity of 

the AAC concretes (Fig. 1; Fig. 2) to 3.7% and 8.8%, respectively, compared to those of the 

reference composition: water absorption of 3.4% and volume of open capillary pores of 8.1%. 

 

a)                                                                           b)                                                     

 

Figure 1: Water absorption of the AAC concretes vs. type of surfactants as ingredient of CA 

and slag contents in the AACs, % (see Table 2): a) #1, #3, #5, #6; b) #2, #4.

 

With increase in slag contents in the AACs up to 88% the effectiveness of modification of the 

AAC concretes by this CA tended to significantly decrease and was accompanied by decline 

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