Behavior of the activated alkali cement (AAC) obtained from blast furnace slag, rice husk ash (RHA) and metakaolin (MK)

Reference	Presenter	Authors (Institution)	Abstract
04-028	Caroline Angulski da LUz	FRARE, A.(Universidade Tecnologica Federal do Paraná); Perardt, M.(Universidade Universidade Tecnologica Federal do Paraná); da LUz, C.A.(UTFPR); Pereira Filho, J.(Universidade Tecnológica Federal do Paraná);	Alkali-activated cements (ACC) are usually obtained from materials rich in CaO, SiO2 and Al2O3 such as ground blast furnace slag (GBFS), fly ash or metakaolin (MK), which are activated by solutions of sodium hydroxide (NaOH), potassium hydroxide (KOH) and silicates. Depending on the chemical composition of raw materials, AAC forms a calcium silicate hydrated (C-S-H) or amorphous aluminosilicate as a hydrated compound. In the last years, some residues have been investigated as alternative raw material in AAC. The rice husk is generated during the process of the grain and it is widely used as fuel in furnaces and boilers thus generating another residue, the rice husk ash (RHA), which is rich in silica (SiO2). In this paper, the goal was to improve the compressive strength of AAC produced from GGBFS, by adding the rice husk ash (RHA) ash and metakaolin (MK) in order to increase the formation of C-S-H or amorphous aluminosilicate. Two type of slags were used: acid, generated in charcoal furnace, and basic, generated in coke furnace. MK as source of Al2O3 and NaOH as alkaline activator were also used. RHA was used as replacement of the slag in order to meet the SiO2 / Al2O3 = 5 ratio, as recommended by literature. The water/cement ratio was 0.4. The results showed that at 28 days, AAC obtained only from GBFS presented 17 MPa while AAC containing RHA and MK presented 25 MPa. The microstructural analysis showed a higher formation of both C-S-H or amorphous aluminosilicate, indicating that metakaolin, as source of Al2O3, and riche husk ash, as source as SiO2, could improve the chemical characteristics of slag to use in AAC.
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