What are alkali activated cements?
Alkali-activated concrete (AAC) is defined as a class of cement-free concrete that is an alternative to Portland cement concrete (PCC). Instead of using ordinary portland cement (OPC) and water, AAC uses other supplementary materials like blast furnace slag (BFS) or fly ash (FA) along with an alkaline activator.
What is an alkali activator?
They were applied two alkaline activators which were mixed, and granulated blast furnace slags (GGBFS) were used as a precursor. Activators were prepared using Sodium hydroxide flakes with 99% purity with a sodium silicate solution (Na2O. Then these activators were mixed applying the adequate alkaline concentration.
What is the difference between geopolymer and alkali activated cement?
Generally in the literature, the ligands with precursors based on alumina and silica are treated as geopolymers, while alkali activated cement are based on precursors rich in calcium.
Which material can be activated using alkaline solution to form geopolymer concrete?
Production of geopolymer cement requires an aluminosilicate precursor material such as metakaolin or fly ash, a user-friendly alkaline reagent (for example, sodium or potassium soluble silicates with a molar ratio MR SiO2:M2O ≥ 1.65, M being Na or K) and water (See the definition for “user-friendly” reagent below).
Is cement an alkali?
The alkali content refers to the content of Na2O and K2O in cement. The condition for concrete to conduct the alkali-aggregate reaction is that the cement must contain alkali.
How do you make an alkaline solution for geopolymer concrete?
6 M to 12 M of NaOH solution and sodium silicate in acquis form (containing 50% water) are used in ratios (called alkalinity ratio Na2SiO3/NaOH = 1 to 2.5) to form a alkaline solution for geopolymer.
What is meant by geopolymer?
Geopolymers are inorganic, typically ceramic, alumino-silicate forming long-range, covalently bonded, non-crystalline (amorphous) networks. Raw materials used in the synthesis of silicon-based polymers are mainly rock-forming minerals of geological origin, hence the name: geopolymer.
What is Portland cement concrete?
Portland cement is the basic ingredient of concrete. Concrete is formed when portland cement creates a paste with water that binds with sand and rock to harden. These ingredients, when heated at high temperatures form a rock-like substance that is ground into the fine powder that we commonly think of as cement.
What is Ggbs in construction?
GGBS (Ground Granulated Blast-furnace Slag) is a cementitious material whose main use is in concrete and is a by-product from the blast-furnaces used to make iron. This ‘granulated’ slag is then dried and ground to a fine powder.
What is low alkali cement?
Low-alkali cements are portland cements with a total content of alkalies not above 0.6 percent. These are used in concrete made with certain types of aggregates that contain a form of silica that reacts with alkalies to cause an expansion that can disrupt a concrete.
What is alkali-activated concrete?
Alkali-activated concrete (AAC) is defined as a class of cement-free concrete that is an alternative to Portland cement concrete (PCC). In AAC, the cement is entirely replaced by an alternative binder.
What is the main hydration product of alkaline activated slag cement?
The main hydration product of alkaline-activated slag cement at room temperature is calcium silicate hydrate gel (C-S-H). The characteristics of slag and the activator used also influence the formation of minor hydration products.
What is the difference between clinker and cement?
The resulting hard substance, called ‘clinker’, is then ground with a small amount of gypsum into a powder to make ordinary Portland cement, the most commonly used type of cement (often referred to as OPC). Portland cement is a basic ingredient of concrete, mortar, and most non-specialty grout.
What is the difference between Vicat Cement and Portland cement?
Vicat’s cement is an artificial hydraulic lime, and is considered the ‘principal forerunner’ of portland cement. The name portland cement is recorded in a directory published in 1823 being associated with a William Lockwood and possibly others.
