Dry powder alkali-activated slag cements

Abstract

This paper reports on the results of an investigation into the possibility of producing dry powder alkali-activated slag cements as a ready-to-use product which can be packed in bags and mixed with water to produce a concrete. The cements were produced using a neutral granulated blast-furnace slag and sodium carbonate. To accelerate strength development at ambient temperatures, a combination of silica fume and slaked lime was used as accelerating admixture in the cement's formulation. Powder sodium lingosulfonate was added into the formulation to reduce the water demand of the cements; it also delayed setting and increased compressive strength. Alkali-activated slag concretes were produced using the developed cements. Compressive strengths in the range from 30 to 85 MPa were achieved for the concretes at 28 d. The accelerating admixture increased 1-d compressive strength for the alkaliactivated slag concretes cured at ambient temperature up to 25 MPa. The optimum concentration of sodium carbonate was equivalent to 3 . 5% and 4 . 5% sodium oxide (Na 2 O) for precast and in situ application, respectively.The accelerating admixture is recommended at 6% for dry powder alkali-activated slag cements. The accelerated ageing test showed that the dry powder alkali-activated slag cement had a sufficient shelf life.

Characterisation of the Hydration Products of a Chemically and Mechanically Activated High Coal Fly Ash Hybrid Cement

“…The production of hybrid cement requires less clinker than that for ordinary Portland cement, leading to a decrease in CO 2 emissions per tonne of hybrid cement manufactured. Hybrid alkaline cements is often preferred over their alkali activated counterparts because its hydration occurs at ambient temperature, and its production do not require the addition of highly alkaline chemicals, but rather rely on a safe source of alkali formed in situ (sodium hydroxide) to facilitate both the dissolution of any amorphous phases present in the source materials [5][6][7][8].…”

Properties and Microstructure of Na2CO3-Activated Binders Modified with Ca(OH)2 and Mg(OH)2

“…For the purpose of serving the one-part Na 2 CO 3 -activated slag binders as practical cementing materials in general applications, recent studies are extensively focused on the use of auxiliary activators to accelerate the kinetics of alkali activation [ 23 , 24 , 25 , 26 , 27 , 28 ]. Kovtun et al [ 29 ] enhanced the 1 day compressive strength of Na 2 CO 3 -activated slag concretes cured at ambient temperature up to 25 MPa via the additions of slaked lime (Ca(OH) 2 ) and silica fume. Akturk et al [ 30 ] observed that only the 3% Ca(OH) 2 addition promoted the hardening of the pastes within 6.5 h. Wang et al [ 31 ] revealed that the CaO addition was beneficial for the formation of C-A-S-H. Gao et al [ 32 ] suggested that the initial reaction between Ca(OH) 2 and Na 2 CO 3 was effective in removing the CO 3 2− ions in the aqueous phase to enhance the alkalinity.…”