The effects of proportion of replacement of 0%, 5%, 10%, 15%, and 20% silica fume on the properties of cpb were studied. Performance of alkali activated slag and alkali activated. The strength formation mechanism of cpb was explored through a combination of scanning electron. Materials free fulltext preparation of a new type of. Performance at high temperature of alkaliactivated slag.
Preparation and properties of alkaliactivated ggbfs thermal storage concrete 271 et al. Study on the early hydration of alkaliactivated slag. Performance at high temperature of alkaliactivated slag pastes produced with silica fume and rice husk ash based activators this study assessed the mechanical properties, and structural changes induced by high temperature exposure, of alkalisilicate activated slag cements produced with sodium silicates derived from silica fume sf and rice. Adding a curing agent can enhance the mechanical properties of soil including its compressive strength. Preparation and properties of alkaliactivated ground. Calculated composition of nasilicateactivated slag and the cs ratio molmol as a function of slag. Alkali activated slag mortar aasm mortar cubes of 70. Gruskovnjak empa, swiss federal laboratories for materials testing and research, du. The detected hydration products by xrd and tga were mainly csh and hydrotalcitelike phases, similar to those from other alkaliactivated slags. The strength of alkaliactivated slagfly ash mortar blends at ambient temperature wardhono, a, law, d and strano, a 2015, the strength of alkaliactivated slagfly ash mortar blends at ambient temperature, in procedia engineering 125. Alkaliactivated cements have a history starting from the 1940s, and table 1 summarizes a historical background about important events in the development of alkaliactivated cements. A new type of cemented paste backfill cpb was prepared using sodium hydroxide naoh as the activator, slag and silica fume sf as the binder, and tailings as the aggregate. Nevertheless, fundamental research on aam has blossomed.
Alkaliactivated slags aas are produced from ground granulated blast furnace slag ggbfs, a byproduct of iron production, and exhibit cementitious properties. The corrosion resistance of steel in alkaliactivated slag aas mortar was evaluated by a monitoring of the galvanic current and halfcell potential with time against a chloridecontaminated environment. Alkaliactivated slag cement concrete aascc has recently attracted interest due to its low environmental impact. As it is shown in part 1, alkaliactivated binders have emerged as an alternative to ordinary portland cement opc binders, which seem to have superior durability and environmental impact. The slags were hydrated in the presence of two different alkaline activators, naoh and na 2 sio 3 5h 2 o wg. Effect of alkali content on strength and microstructure of ggbfs paste. The hydration process of alkaliactivated slag cement, especially at earlyage, was studied by ftir, compared with that of portland cement. The thermodynamic model for alkaliactivated slag system developed by myers et al. Material science research using electron microscopy. Slag and activator chemistry control the reaction kinetics of. Thermodynamic modelling of alkaliactivated slag cements. In 2016, a paper published by a group of scientists determined that there is no presence of nash or kash in geopolymer cement see part 3 below. Thermodynamic modelling was performed using the gibbs energy minimisation software.
In the current study different steam curing temperatures have been tried to stimulated binding reactions in ctcs slag to investigate the. Aas concretes have been shown to have improved corrosion and freezethaw resistance compared to traditional cementbased concretes. Certain aggregates can be added to control the strength and thermal conductivity of concrete. The strength of alkaliactivated slagfly ash mortar. Effect of alkali content on strength and microstructure. Sodium hydroxide and potassium silicates were used as alkaline activators. Flexure strength and punching shear strength\r\n created date 20160309170847z. These data and the thermodynamic model used to describe maoh ldh are. There are two main families of alkali activated binders. Effect of drying rate on shrinkage of alkaliactivated.
The properties of alkali activated ggbs are dependent on the hydration and cement and time. This paper presents results of detailed investigations about the alkaline activation of ground granulated blast furnace slags whose chemical composition were modified. The practical problems mentioned are quick setting, the possibility of alkaliaggregate reaction. This increasing slag hydration reaction results in increased consumption of. Mechanical and microstructural characterization of alkali. Thermodynamic modelling article pdf available in advances in cement research 192.
Higher mgo content of the slag resulted in a faster reaction and higher compressive strengths during the first days. To understand the main properties of cement, a ubiquitous material, a sound description of its chemistry and mineralogy, including its reactivity in aggressive environments and it. In this study, two types of slag, a and b, generated in charcoal and coke blast furnaces, respectively, were activated with naoh in contents of 4, 5 and 6% to obtain alkaliactivated slag aas. Abstractthis study investigates the mechanical and microstructural characterization of alkaliactivated fly ashslag aafs mortars with various ratios of fly ash to slag. The reactive component of blast 47 furnace slag is a calciummagnesium aluminosilicate glass that dissolves under the high ph conditions 48 provided by the activator to form a hydrated phase assemblage that consolidates into a.
Alkali activated cements including geopolymer cements. The influence of different parameters on the hydration. Moreover, thermodynamic modelling revealed that a higher sa of slag leads to. Hydration products of alkali activated slag cement. Sodium silicatebased, alkaliactivated slag mortars part. Properties of alkali activated materials in comparison with standard portland cement are discussed. Practical problems and theoretical questions are discussed. The subjects of part 2 of this paper are prime materials, alkaline activators. Thermodynamic modelling is applied here to describe the phase assemblages of. The results show that as the temperature raise, the hydration rate and hydration heat of the aas cementing materials will remarkably accelerate. Iucr deciphering mineralogical changes and carbonation. Also, the durability of aam inservice has been demonstrated over several decades in belgium, finland, the former ussr and china, and more recently in australia. In instituto eduardo torroja, spain, since the early 1990s, palomo and puertas have studied the alkali activation of fly ash and blast furnace slag, respectively.
Alkaliactivated materials are considered thirdgeneration binders after lime and ordinary portland cement opc. Introduction in order to reduce environmental effects and pollution caused in manufacturing of cement there is a need in search for an alternative material, the newly developed geopolymer concrete helps up to replace conventional concrete. Tem and sem characterization of alkali activated slag figure 1. Performance of alkaliactivated slag concrete, the university of sheffield, sheffield.
Slagalkali cements1,2, alkaliactivated gypsumfree cement 3, cements of the pyrament 4 type or geopolymeric binders 5,6,7 are new types of inorganic binding agents whose common feature is alkaline activation of clinker or substances with latent hydraulic properties, such as slag or fly ash. The calculations predict the formation of cash, stratlingite and hydrotalcite in different alkaliactivated slag systems, which agrees well with experimental findings. Products of the slag hydration are first summarized from observations in literature. Present state and future of alkaliactivated slag concretes. Alkali activated cements and concrete civil engineering. Effect of curing conditions on the compressive strength. Effect of slag chemistry on the hydration of alkali. Reactivity and hydration property of synthetic air quenched slag. Alkaliactivated slag aas is one type of alkaliactivated cement product that can offer superior. Advances in cement research, volume 12, issue 4, 1 oct 2000 163172. Activation of ground granulated blast furnace slag by. This binder has exhibited excellent mechanical strength and durability, but some mixtures have demonstrated short setting times or excessive shrinkage. Topics for future work in this field are suggested.
We classify this new kind of binders as the third generation cement after lime and ordinary portland cement opc, and it is now accepted that alkaliactivated cements have emerged as an alternative to opc, which. The hydration and the microstructure of three alkali activated slags aas with mgo contents between 8 and wt. Alkali activated systems understanding the influence of curing conditions and activator typechemistry on the mechanical strength and chemical structure of fly ashslag systems by ussala chowdhury a thesis presented in partial fulfillment of the requirements for the. Influence of slag chemistry on the hydration of alkali. Hydration mechanisms of activated blast furnace slag dora 4ri. Alkaliactivated blast furnace slag cements have been studied since the 1930s due to its high compressive strength, they can exceed 100 mpa in 28 days. Gemsrelated publications gemselektor paul scherrer institut. The use of nonstandard aggregate and other industrial byproducts, as well as the low costs of this type of concrete are presented. Authors thermodynamic modelling applications of gems. Manufacture on a commercial basis is underway in the uk, australia, usa and possibly, china. Overview of the stateoftheart on the alkali activated materials since 1973 in department of glass and ceramics in prague. The composition of solid and liquid phases of alkaliactivated slag systems was investigated by thermodynamic modelling.
Thermodynamic modelling of bfspc cements under temperature. Delft university of technology thermodynamic modeling and. It can also be activated directly with alkali salts to give a clinkerfree binder. The concept of alkali activated materials aam as an alternative to portland cement has been knownsince at least 1908. Influence of micronised biomass silica on the workability. Reaction models are proposed to quantify the hydration products and to determine the composition of csh from alkaliactivated slags aas. Alkaliactivated cements and concretes caijun shi, della. Alkali activated cementitious material and concrete. These two types of binders can be manufactured by directly mixing alkaline activators sodium, potassium alkalis and salts into ground metallurgical slags, fly ashes and natural pozzolans. It has a latent hydraulic reactivity, which can be catalyzed by proper activators to form cementitious materials.
The main hydration products include csh, hydrotalcite, hydrogarnet, afm phases c4ah and c2ash8 and ettringite. The limited utilization of thermodynamic modelling in the hydration of alkaliactivated slag is mainly due to. Ftir study on earlyage hydration of alkaliactivated. Resistance of alkaliactivated slag concrete to chloride.
The main hydration products include csh, hydrotalcite, hydrogarnet, afm phases c 4ah and c 2ash 8 and ettringite. The difference of microstructure between portland cement concrete and alkaliactivated slag concrete and its consequences for their properties, especially for very high strengths and corrosion resistance, is discussed. Most studies on alkaliactivated systems are on amorphous materials and a detailed study on the effect of temperature on the hydration reaction in crystalline slags is scarce. However, few studies have quantitatively analyzed the compressive strength and microstructure of soils to explore the impact of changes in the microstructure on compressive strength. International journal of innovative research in science. Geopolymer, alkali activated materials, microstructure, fly ash the paper presents an overview of the stateoftheart on the alkali activated materials since 1973 in department of glass and ceramics in prague. Preparation of alkali activated slag aas mortar and concrete. The early hydration of alkaliactivator slagaas cementing material is studied by changing the environment temperature, the proportion of slag and fly ash, water glass module, and dosage of sodium silicate.
Materials free fulltext the effect of changing fly. The low casi ratio in slag improves its resistance to aggressive chemical materials such as acids, chlorides and. Low temperature calorimetry and alkaliactivated slagsthesis. For chloride transport, rapid chloride penetration test was performed, and chloride binding capacity of aas was evaluated at a given chloride. Alkali activated cement, slag pastes, hydration products vol. Such alkaliactivated slag aas materials have been used in china, eastern europe, scandinavia, and the former ussr. Phase diagrams for alkaliactivated slag binders sciencedirect.
Thermodynamic modeling can be used for the understanding of the interactions between the. The 5th international conference of euro asia civil engineering forum eacef5, surabaya, indonesia, 1518 september 2015, pp. Groundgranulated blast furnace slag ggbfs is an amorphous byproduct of the steel industry. Talling and brandstetr 39 obtained optimum strength for a slag blaine. The comparison of alkaliactivated slag aas with ordinary portland cement opc showed that. Neither were cshii and caoh2 found in the aas pastes. In addition, the cost of curing agents is too high to be widely used.