Preparation of autoclaved aerated concrete using copper tailings and blast furnace slag

Aerated concrete (AC), such as cellular concrete, autoclaved aerated concrete (AAC), and non-autoclaved aerated concrete (NAAC), having excellent insulation properties, is commonly used in buildings located in cold regions, such as Nur-Sultan in Kazakhstan, the second coldest capital city in the world, because it can contribute to a large energy saving. However, when the AC is directly exposed to the repeated freeze and thaw (F-T) cycles, its F-T resistance can be critical because of lower density and scaling resistance of the AC. Moreover, the evaluation of the F-T resistance of the AC based on the durability factor (DF) calculated by using the relative dynamic modulus of elasticity may overestimate the frost resistance of the AC due to the millions of evenly distributed air voids in spite of its weak scaling resistance. In the present study, the F-T resistance of NAAC mixtures with various binary or ternary combinations of ground granulated blast-furnace slag (GGBFS) and micro-silica was assessed mainly using the ASTM C 1262/C1262M-16 Standard Test Method for Evaluating the Freeze-Thaw Durability of Dry-Cast Segmental Retaining Wall Units and Related Concrete Units. Critical parameters to affect the F-T resistance performance of the NAAC mixture such as compressive strength, density, water absorption, air–void ratio (VR), moisture uptake, durability factor (DF), weight loss (Wloss), the degree of saturation (Sd), and residual strength (Sres) were determined. Based on the determined parameter values, frost resistance number (FRN) has been developed to evaluate the F-T resistance of the NAAC mixture. Test results showed that all NAAC mixtures had good F-T resistance when they were evaluated with DF. Binary NAAC mixtures generally showed higher Sd and Wloss and lower DF and Sres than those of ternary NAAC mixtures. It was determined that the Sd was a key factor for the F-T resistance of NAAC mixtures. Finally, the developed FRN could be an appropriate tool to evaluate the F-T resistance of the NAAC mixture.

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Influence of fly ash and blast furnace slag on characteristics of geopolymer non-autoclaved aerated concrete

Transport and Communication Science Journal ◽

10.47869/tcsj.72.1.4 ◽

2021 ◽

Vol 72 (1) ◽

pp. 25-32

Author(s):

Le Tuan Anh ◽

Nguyen Thuy Ninh ◽

Le Quoc Phong Huu ◽

Le Sinh Hoang ◽

Nguyen Khoa Tan

Keyword(s):

Blast Furnace ◽

Fly Ash ◽

Blast Furnace Slag ◽

Curing Conditions ◽

Aluminium Powder ◽

Autoclaved Aerated Concrete ◽

Alkaline Agent ◽

Alumino Silicate ◽

Aerated Concrete ◽

Furnace Slag

Geopolymer materials are known as sustainable and environmental material. The main constituents of geopolymer material are alumina and silicon, which can be activated in an alkaline environment. In this paper, the reaction of alumino-silicate materials in the alkaline agent is investigated on geopolymer non-autoclaved aerated concrete (GNAAC). The main constituents of GNAAC are fly ash (FA), blast furnace slag (BSF), lime, gypsum, aluminium powder, and alkaline solution. In the mix proportions, FA and BSF are used to replace crushed sand and cement. The results indicate that the GNAAC can be produced similarly as traditional autoclaved aerated concrete. Besides, the flow diameter of the mixture using blast furnace slag is lower than that of fly ash. The temperature and expansion ability decrease with an increase in FA/BFS – Lime and alkaline content. Furthermore, the compressive strength of GNAAC can be determined by synthesizing geopolymer without steam and pressure curing conditions.

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