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

19

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 

 

closed pores in AAC concrete rises. This is due to fact that the hydrated AACs contain higher 

volume of gel pores compared than portland cement [17]. Accordingly, with increase in the 

content of alkaline component in AACs formation of gel with conditionally closed pores 

occurs with greater speed. This phenomenon determines formation of a more dense and 

impermeable structure of AAC concretes accompanied with higher freeze/thaw resistance. 

 

In addition, it is possible to control the porosity and accordingly freeze/thaw resistance of 

AAC concretes by addition of placticizing admixtures with various nature of main active 

ingredient, which must be selected depending on composition of AACs. In case of the AACs 

with 50...69% of slag the

 

maximum efficiency has sodium gluconate, i.e. salt of carbonic acid 

and alkali, and at 88...100% of slag in AACs the polyether as polyethylene glycol is effective. 

At the same time, polyacrylate esters, which are traditionally used in concretes based on 

portland cement, can be ineffective in AAC concretes due to destruction of their molecular 

structure in hydration medium of AACs. 

 

 

4. Conclusions 

 

Regularities of formation of pore structure of the AAC concretes were found to depend on 

slag contents and type of alkaline component of AACs. The possibility of obtaining AAC 

concretes with high freeze/thaw resistance from the concrete mixes with high slumps was 

shown. In general, the increase in slag contents in the AACs associated with higher contents 

of the alkaline component resulted in the lower volumes of open pores and higher volumes of 

conditionally closed pores. This phenomenon can be attributed to volumetric loss of ice 

resulted in the higher freeze/thaw resistance of the AAC concretes. Change of anionic part of 

the alkaline component from carbonate to silicate improved water absorption and porosity of 

the reference and plasticized AAC concretes. 

 

The polyester-based admixtures were found to be effective in the AACs only to some extent. 

With increase in contents of slag and alkaline component the application of admixtures based 

on polyethers and alkaline salts of carboxylic acids in the presence of sodium lignosulfonate 

was found to result in the formation of artificial pore structure of the plasticized AAC 

concretes. This phenomenon was found to create additional air space allowing water to 

expand during freezing and therefore the weakening of concrete structures under cyclic 

freezing and thawing was lower. 

 

 

Acknowledgments

 

The authors would like to acknowledge the contribution of the COST Action TU1404. 

http://www.tu1404.eu/ 

 

 

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20

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 

 

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