Properties of cementless mortars activated by sodium silicate

Abstract

The present paper reports the testing of twelve alkali-activated mortars and a control ordinary portland cement (OPC) mortar. The main aim is to develop cementless binder activated by sodium silicate powder. An alkali quality coefficient combining the amounts of main compositions of source materials and sodium oxide (Na 2 O) in sodium silicate is proposed to assess the properties of alkali activated mortars, based on the hydration mechanism of alkali-activated pastes. Fly ash (FA) and ground granulated blast-furnace slag (GGBS) were employed as source materials. The ratio of Na 2 O-to-source material by weight for different mortars ranged between 0.038 and 0.164; as a result, alkali quality coefficient was varied from 0.0025 to 0.0365. Flow loss of fresh mortar, and shrinkage strain, compressive strength and modulus of rupture of hardened mortars were measured.The compressive strength development of alkali activated mortar was also compared with the design equations for OPC concrete specified in ACI 209 and EC 2. Test results clearly showed that the flow loss and compressive strength development of alkali-activated mortar were significantly dependent on the proposed alkali quality coefficient. In particular, a higher rate of compressive strength development achieved at early age for GGBS-based alkali-activated mortar and at longterm age for FA-based alkali-activated mortar. In addition, shrinkage strain and modulus of rupture of alkali-activated mortar were comparable to those of OPC mortar.

Hydration and properties of sodium sulfate activated slag

“…Yang et al [39] reported that the initial flow of an alkali activated mortar decreased with an increase of Na 2 O content when they used sodium silicate powder as an activator. Yang and Song [40] used sodium silicate powder and sodium hydroxide powder to produce AAS mortars.…”

Properties of Foundry Sand, Ground Granulated Blast Furnace Slag and Bottom Ash Based Geopolymers under Ambient Conditions

“…Ground Granulated Blast furnace slag, a by product obtained from the steel industries is a glassy, granular, non metallic material consisting essentially of silicates and aluminates of calcium and other bases. Addition of GGBFS is said to enhance geopolymerisation and increase the compressive strength mix [ [19][20][21][22][23], Ambily (2011Ambily ( ,2012]. Moreover GGBFS proves to be an effective binder to produce better quality than Ordinary Portland Cement concrete (OPC) [25,26].…”

Flow and Compressive Strength of Alkali-Activated Mortars

“…Yang et al 14 . Sodium hydroxide powder was also added in groups I and II to control the molar ratio (SiO 2 /Na 2 O) of the sodium silicate at the same Na 2 O/SM ratio.…”

“…Yang and Song 14,16 showed that the compressive strength development of GGBS-based AA mortar according to age could be modeled using the formula recommended by ACI 209 17 as follows:…”

“…However, the Na 2 O/SM ratio cannot reflect the effect of the molar Si-to-Al ratio and calcium content in the source material on the mechanical strength of alkaliactivated paste. Yang et al 14 proposed an alkali quality coefficient A Q as an effective index to evaluate the workability and compressive strength of AA mortars using sodium silicate and sodium hydroxide powders: Table 3 gives the range of input data in training, validation and test subsets used to develop the 14 NNs. Training, validation and test subsets had 50%, 25%, and 25% of all specimens in the database, respectively.…”