Influence of admixtures on the properties of alkali-activated slag mortars subjected to different curing conditions

Abstract This paper presents the influence of shrinkage-reducing (SHR) and superplasticizing and set-retarding admixtures (SSRe) on the properties of slag pastes and mortars activated by liquid sodium silicate with different dosage and modulus ratio. Properties in the fresh and hardened state for these binders were investigated by means of measuring some properties including setting time, flowability, flexural strength, compressive strength, carbonation and shrinkage. In this study, fifteen pastes and mortars were prepared. Liquid sodium silicate was used to activate the slag at two sodium concentrations, 4% and 6% by mass of slag. Liquid sodium silicate and sodium hydroxide were blended to obtain 0.75 and 1 modulus ratio of SiO 2 /Na 2 O. Results showed that although the higher percentage of sodium in the activator produced a higher strength, workability and setting times rapidly decreased with the higher sodium concentration due to instantaneous reaction and quick hardening of slag activated by liquid sodium silicate. None of the admixtures generally had an impact on the setting times of alkali-activated slag (AAS) pastes. SSRe admixture increased the flow rate of AAS mortars while SHR admixture partially affected the flow values of AAS mortars. SHR admixture exhibited a slight decrease in the carbonation depths of AAS mortars. SSRe and particularly SHR chemical admixtures reduced the shrinkage of AAS mortars. However, the shrinkage values of AAS mortars still were higher than those of ordinary Portland cement (NPC) mortars. Curing conditions had a significant effect on the mechanical behavior in the hardened state of AAS mortars compared to NPC mortars.

[1]  F. Puertas,et al.  Effect of Superplasticizer and Shrinkage-Reducing Admixtures on Alkali-Activated Slag Pastes and Mortars , 2005 .

[2]  Francisca Puertas,et al.  Effect of superplasticisers on the behaviour and properties of alkaline cements , 2003 .

[3]  Jay G. Sanjayan,et al.  Resistance of alkali-activated slag concrete to acid attack , 2003 .

[4]  J. Sanjayan,et al.  Workability and mechanical properties of alkali activated slag concrete , 1999 .

[5]  Jay G. Sanjayan,et al.  Early age strength and workability of slag pastes activated by NaOH and Na2CO3 , 1998 .

[6]  V. M. Malhotra,et al.  Properties and Durability of Alkali-Activated Slag Concrete , 1992 .

[7]  Theo Fett,et al.  Determination of Strength , 1999 .

[8]  F. Puertas,et al.  Carbonation process of alkali-activated slag mortars , 2006 .

[9]  Darko Krizan,et al.  Effects of dosage and modulus of water glass on early hydration of alkali–slag cements , 2002 .

[10]  T Hakkinen.  THE PERMEABILITY OF HIGH STRENGTH BLAST FURNACE SLAG CONCRETE , 1992 .

[11]  Silvio Delvasto,et al.  Morteros de cementos alcalinos. Resistencia química al ataque por sulfatos y al agua de mar , 2002 .

[12]  Francisca Puertas,et al.  Alkali-activated slag mortars: Mechanical strength behaviour , 1999 .

[13]  Serdar Aydın,et al.  Mechanical and microstructural properties of heat cured alkali-activated slag mortars , 2012 .

[14]  P. L. Pratt,et al.  Alkali-activated slag cement and concrete: a review of properties and problems , 1995 .

[15]  Erich D. Rodríguez,et al.  Effect of binder content on the performance of alkali-activated slag concretes , 2011 .

[16]  J. Sanjayan,et al.  Effect of elevated temperature curing on properties of alkali-activated slag concrete , 1999 .

[17]  S. A. Al-Saleh,et al.  Effects of drying conditions, admixtures and specimen size on shrinkage strains , 2006 .

[18]  K. Folliard,et al.  Properties of high-performance concrete containing shrinkage-reducing admixture , 1997 .

[19]  Jay G. Sanjayan,et al.  Cracking tendency of alkali-activated slag concrete subjected to restrained shrinkage , 2000 .

[20]  P. L. Pratt,et al.  Factors affecting the strength of alkali-activated slag , 1994 .

[21]  V. Lehtonen,et al.  Durability of Concrete Made With Alkali-Activated Slag , 1989, "SP-114: Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete: Proceedings of the Third International Conference".

[22]  Jay G. Sanjayan,et al.  Strength and shrinkage properties of alkali-activated slag concrete containing porous coarse aggregate , 1999 .

[23]  M. Ghrici,et al.  Mechanical and durability properties of cement mortar with Algerian natural pozzolana , 2006 .

[24]  J. Sanjayan,et al.  Microcracking and strength development of alkali activated slag concrete , 2001 .

[25]  C. Atiş,et al.  Alkali activation of mortars containing different replacement levels of ground granulated blast furnace slag , 2012 .

[26]  Jiang‐Jhy Chang,et al.  A study on the setting characteristics of sodium silicate-activated slag pastes , 2003 .

[27]  Cengiz Duran Atiş,et al.  Influence of Activator on the Strength and Drying Shrinkage of Alkali-Activated Slag Mortar , 2009 .

[28]  Jay G. Sanjayan,et al.  Alkali activation of Australian slag cements , 1999 .

[29]  M. Chi.  Effects of dosage of alkali-activated solution and curing conditions on the properties and durability of alkali-activated slag concrete , 2012 .

[30]  Francisca Puertas,et al.  Effect of Shrinkage-reducing Admixtures on the Properties of Alkali-activated Slag Mortars and Pastes , 2007 .

[31]  Jay G. Sanjayan,et al.  Effect of admixtures on properties of alkali-activated slag concrete , 2000 .

[32]  Keun-Hyeok Yang,et al.  Properties of cementless mortars activated by sodium silicate , 2008 .

[33]  Jay G. Sanjayan,et al.  Resistance of alkali-activated slag concrete to carbonation , 2001 .

[34]  C. W. Richards,et al.  Effect of curing and heat treatment history on the dynamic mechanical response and the pore structure of hardened cement paste , 1973 .

[35]  S. Al-Otaibi,et al.  Durability of concrete incorporating GGBS activated by water-glass , 2008 .

[36]  Rachel J. Detwiler,et al.  Backscattered electron imaging of cement pastes hydrated at different temperatures , 1990 .

[37]  W. Yeih,et al.  Effects of gypsum and phosphoric acid on the properties of sodium silicate-based alkali-activated slag pastes , 2005 .