A study of the effect of light-burnt dolomite on the hydrationof alkali-activated Portland blast-furnace slag cementWan-Hee Yanga, Dong-Woo Ryub, Dong-Cheol Parkc, Woo-Jae Kimd, Chee-Ho SeoaaDepartment of Architectural Engineering, Konkuk University, 1, Hwayang-dong, Gwangjin-gu, Seoul 143-701, Republic of KoreabDepartment of Architectural Engineering, Daejin University, San 11-1, Sundan-dong, Pochon, Gyeonggi-do 487-811, Republic of KoreacR&D Center, Intchem Co., Ltd., 489-3, Maetan-dong, Yeongtong-gu, Suwon, Gyeonggi-do 443-370, Republic of KoreadResearch & Engineering Division R&D Center, POSCO E&C, 180-1, Songdo-dong, Yeonsu-Gu, Incheon 406-840, Republic of Koreah i g h l i g h t s?In Na2SO4-activated Portland blast-furnace slag cement, the hydration heat increased with the addition of LBD.?A delay of the initial setting time was observed with the addition of LBD.?The compressive strength improved with the addition of LBD.?The pore structure of the paste became dense after 28 days of aging.a r t i c l ei n f oArticle history:Received 29 April 2013Received in revised form 16 January 2014Accepted 22 January 2014Available online 21 February 2014Keywords:Alkali-activated cementBlast-furnace slagLight-burnt dolomiteSodium sulfateHeat of hydrationa b s t r a c tThis study used the typical powder alkaline material anhydrous sodium sulfate (Na2SO4) as an activatorin a system in which Portland cement (1020%) and ground granulated blast-furnace slag (GGBS, 8090%)are generally mixed and added to light-burnt dolomite (LBD), one of the economical lime materials. Theireffect on the hydration and strength of the cement was then analyzed. According to the analysis, the 1stpeak of the minute heat of hydration increased after mixing the LBD. On the other hand, for the 2nd peak,a slight delay was observed. As a result of the mixing, the cumulative heat of hydration increased.Although the rate of setting decreased, the strength of the material improved after the 3rd, 7th and28th days. In other words, it was confirmed that the pore structure of the paste became dense after28 days of aging.? 2014 Elsevier Ltd. All rights reserved.1. IntroductionPortland cement is the most widely used construction material1,2, but it accounts for approximately 5% of greenhouse gas emis-sions 2.Therefore, there have been many studies on various materials toreduce the use of or substitute Portland cement with the goal ofreducing environmental pollution 2. In particular, alkali-acti-vated slag cement (AASC) is economically advantageous becausethe industrial by-products can be effectively used. Furthermore,so far, great characteristics substituting Portland cement are re-ported through various studies in AASC, and some countries havepartially used it 3. However, AASC has lower resistance of carbon-ation than Portland cement 35, and it has greater drying shrink-age 3,610.In addition, ground granulated blast-furnace slag (GGBS) whichis commonly applied to the AASC, has been used to manufactureconcrete along with Portland cement in concrete manufacturingin various countries with advanced steel industries 3,11,12.On the other hand, there are some problems with AASC thatprevent this material from being a practical replacement for Port-land cement. For example, this material is not compatible with theexisting facilities used to manufacture ready-mix concrete 13. Atpresent, there are two ways to manufacture AASC: the use of liquidalkaline materials and the use of powdered alkaline materials. Inthe former method, additional tank to store liquid activator is re-quired to use these liquid materials in the conventional ready-mixed concrete factories. In the second method the powdered alka-line materials can be easily used in the conventional ready-mixedconcrete manufacturing facilities thorough premixing when manu-facturing either slag powder or slag cement.Well-known representative powder-phase activators are sodiumsulfate and sodium carbonate; sodium sulfate is slightly morehttp:/dx.doi.org/10.1016/j.conbuildmat.2014.01.0710950-0618/? 2014 Elsevier Ltd. All rights reserved.Corresponding author. Tel.: +82 2 3436 7898; fax: +82 2 3436 7897.E-mail address: (W.-H. Yang).Construction and Building Materials 57 (2014) 2429Contents lists available at ScienceDirectConstruction and Building Materialsjournal homepage: (for the industrial product, the cost of sodium sulfate isabout 50% of the cost of sodium carbonate), and sodium sulfate isknown to improve the strength of cementitious materials by gen-erating ettringite because of sulfate included in lime-basedcementing materials 3.The light-burnt dolomite (LBD) is one of economical powder-phased lime materials, and it generates Ca(OH)2from the reactionwith water, leading to an applicability as an activator. In the con-ventional study 14,15, there was a practice of using (?10%) Mag-nesia (MgO) for the purpose of drying shrinkage reduce in AASCusing liquid activator (mainly sodium silicate solution), and in thisstudy,