Drying Shrinkage and Durability Studies on Alkali Activated Slag Concrete Using Different Activators

Abstract

The production of OPC is responsible for about 7% of the world's CO 2 emissions, lead to the search for more environ mentally viable alternative to cement. One of those alternative material is alkali-activated slag (AAS) where ground granulated blas t furnace slag is used not as a partial replacement to cement but as a sole binder in the production of concrete. The durability performance of alkali-activated slag concrete with sodium silicate, with and without addition of hydrated lime, sodium hydroxid e with lime and sodium carbonate as activators are studied. All the activators are used at 8% Na 2 O (by weight of slag) and 4% of hydrated lime by total weight of solid binder content if used as a retarder. Drying shrin kage was measured up to 40 days. The d urability potential of AAS concrete was investigated by testing for o xygen permeability and porosity. Among different AAS concrete Na 2 C0 3 activated concrete (SC8) showed less shrinkage, wh ich is little bit higher than OPC concrete with same w/c (CM 2) but lower than OPC/Slag b lended mix (SLG60) where as water-glass activated slag showed highest drying shrinkage. A mong AAS concrete, L.S.S activated slag concrete without addition of lime (SS8) showed lower porosity, wh ich was even little b it lower than the OPC concrete having same w/c rat io (CM 2) at the age of 28days. NaOH act ivated slag concrete (SS8L4) showed high porosity than other AAS concrete in both water and dry curing conditions, whereas Na 2 CO 3 act ivated slag concrete showed comparable porosity with OP C concrete (CM2). Therefore, the use of SC as an activator for slag concrete is recommended, since it results in adequate strength, comparable or lower shrinkage to control mixes and almost equal or co mparable porosity. KEYWORDS: Alkali activated slag concrete, durability, permeab ility, drying shrinkage and porosity. NOTATIONS: AAS = Alkali activated slag, C-S-H = Calciu m Silicate Hydrate, DC = Dry Curing, GGBS = Ground granulated blast-furnace slag, L.S.S = Liquid sodium silicate, Ms = Modulus of silica, OPC = Ord inary Portland cement, SC = Sodiu m Carbonate, SH = Sodiu m Hydro xide, UPV = Ult rasonic pulse velocity, WC = Water Curing, DC = Dry Curing.