Utilisation of sodium silicate activated blast furnace slag as an alternative binder in paste backfill of high-sulphide mill tailings

An efficient solution to increase the sustainability of building materials is to replace Portland cement with alkali-activated materials (AAM). Precursors for those systems are often based on water-cooled ground granulated blast furnace slags (GGBFS). Quenching of blast furnace slag can be done also by air but in that case, the final product is crystalline and with a very low reactivity. The present study aimed to evaluate the cementitious properties of a mechanically activated (MCA) air-cooled blast furnace slag (ACBFS) used as a precursor in sodium silicate alkali-activated systems. The unreactive ACBFS was processed in a planetary ball mill and its cementing performances were compared with an alkali-activated water-cooled GGBFS. Mixes based on mechanically activated ACBFS reached the 7-days compressive strength of 35 MPa and the 28-days compressive strength 45 MPa. The GGBFS-based samples showed generally higher compressive strength values.

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SODIUM SILICATE ACTIVATED SLAG-FLY ASH CEMENT

Proceedings of International Structural Engineering and Construction ◽

10.14455/isec.res.2014.43 ◽

2014 ◽

Vol 1 (1) ◽

Author(s):

Jan Pieter Vermeulen ◽

Natalie Lloyd

Keyword(s):

Blast Furnace ◽

Fly Ash ◽

Silica Fume ◽

Sodium Silicate ◽

Blast Furnace Slag ◽

High Strength ◽

Chemical Balance ◽

Aluminum Hydrate ◽

Activated Slag ◽

Furnace Slag

This research examines an alternative binder, Alkali Activated Cement (AAC), examining the fresh and hardened mechanical properties of twelve AAC mortar mixes with varying mixture proportions of blast-furnace slag, fly ash, sodium silicate (the alkali activator), and additional water. In addition to the Slag-Fly Ash mortars, nine mixtures with blast-furnace slag, silica fume, aluminum hydrate, sodium silicate, and water were tested. For all mortars, the compressive strength was exponentially related to the water/activator-solids ratio. Mortar strengths at 28 days ranged from 5 MPa to 20 MPa. Increasing the slag to binder-solids ratio from 0.1 to 0.2 increased the strength with water to binder ratios from 0.2 to 0.4. However, rapid or almost instantaneous setting times were observed for a slag to binder-solids ratio of 0.2. The research concluded that using a carefully chosen mix design can prevent quick setting while still achieving high strength and acceptable workability. It is suggested the CaO to binder-solids ratio remain below 0.07; a sodium silicate to binder solids ratio of around 0.25 is optimal; a water to binder-solids ratio should be around 0.3. When replacing fly ash, a Si/Al ratio above 2 is recommended. This research concluded that other solids (Silica Fume and Aluminum Hydrate) could replace Slag and/or Fly Ash if the overall chemical balance of the system is maintained.

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Effect of Sodium Silicate Properties in Alkali-Activation of Mexican Blast Furnace Slag

MRS Proceedings ◽

10.1557/opl.2016.4 ◽

2016 ◽

Vol 1813 ◽

Author(s):

O. F. Cortés-Salmerón ◽

M. L. García-Chávez ◽

T. A. García-Mejía

Keyword(s):

Blast Furnace ◽

Sodium Silicate ◽

Blast Furnace Slag ◽

Alkali Activation ◽

X Ray Diffraction ◽

Weight Percentage ◽

Average Value ◽

Accelerated Curing ◽

Compressive Strength Test ◽

Furnace Slag

ABSTRACTThe present work is a study on alkali activation of Mexican blast furnace slag, using sodium silicate. The aim is to produce an optimal specimen, homogeneous without carbonation, and with small fraction of crystalline phases, similar to CSH, which provide mechanical properties suitable to use in the construction industry. The samples were prepared using sodium silicate activator solutions with modulus (SiO2/Na2O) of 1.25, 1.5, and 1.75. The weight percentage of Na2O in the activator solutions was added at 4, 6 and 8% relative to the slag weight. The prepared samples were stored in sealed molds, at room temperature (20°C), during 7 days. The X-ray diffraction has revealed the presence of an amorphous phase, semi crystalline clinotobermorite phase and signals of calcium carbonate for the samples of 4 and 6 % of Na2O; in contrast with the 8% Na2O, where the latter signals almost disappeared. The specimen selected as optimal was prepared with an activator concentration of 8% of Na2O /Slag, and SiO2/Na2O of 1.25. A specimen under these optimal conditions was prepared with accelerated curing (40°C, humidity, 48 hours), and a compressive strength test was attained, with an average value of 52 MPa at 3 days.

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Cementitious composites of pulverised fuel ash and blast furnace slag activated by sodium silicate: effect of Na2O concentration and modulus

Advances in Applied Ceramics ◽

10.1179/174367606x120151 ◽

2006 ◽

Vol 105 (4) ◽

pp. 201-208 ◽

Cited By ~ 52

Author(s):

J. I. Escalante García ◽

K. Campos-Venegas ◽

A. Gorokhovsky ◽

A. Fernández

Keyword(s):

Blast Furnace ◽

Sodium Silicate ◽

Blast Furnace Slag ◽

Cementitious Composites ◽

Fuel Ash ◽

Furnace Slag

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Autogenous Deformation of Alkali-Activated Blast Furnace Slag Concrete Subjected to Variable Curing Temperatures

Advances in Civil Engineering ◽

10.1155/2019/6903725 ◽

2019 ◽

Vol 2019 ◽

pp. 1-8 ◽

Cited By ~ 4

Author(s):

Katalin Orosz ◽

Abeer Humad ◽

Hans Hedlund ◽

Andrzej Cwirzen

Keyword(s):

Blast Furnace ◽

Diffraction Analysis ◽

Sodium Silicate ◽

Blast Furnace Slag ◽

Curing Temperature ◽

X Ray Diffraction ◽

X Ray ◽

Activated Slag ◽

Furnace Slag ◽

Alkali Activated

Deformations of alkali-activated slag concrete (AASC) with high MgO and Al2O3 content, subjected to variable curing temperature were studied. Sodium silicate and sodium carbonate were used as alkali activators. The obtained results showed development of deformations consisting of both shrinkage and expansion. Shrinkage appeared not to be affected by the activator type, while the expansion developed after the cooling down phase in stabilized isothermal conditions and did not stop within the duration of the tests. X-ray diffraction analysis performed shortly after the cooling down phase indicated the formation of crystalline hydrotalcite, which was associated with the observed expansion. A mixture with a higher amount of sodium silicate showed less expansion, likely due to the accelerated hydration and geopolymerization leading to the increased stiffness of the binder matrix.

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