This thesis deals with development of shrinkage reducing admixtures designed for alkali activated materials based on blast furnace slag. The main task of this work is to select the most suitable shrinkage reducing admixture based on experiments, in which can be observed minimal shrinkage and at the same time it will not adversely affect the properties of alkali activated blast furnace slag. In the experimental part of the work, test beams containing shrinkage reducing admixtures were prepared, in which the shrinkage and loss of weight were measured. Moreover, the mechanical properties of individual beams, such as tensile strength and compressive strength, were measured. Next, the surface tension of individual shrinkage reducing admixtures was measured in a mixture with pore solution. The hydration process of alkali activated materials under the action of reducing shrinkage admixtures was monitored by calorimetric analysis. The microstructure of the prepared samples was observed by scanning electron microscopy.

High performance concrete (HPC) provides a long lasting, durable concrete that is typically used in bridge decks due to its low permeability, high abrasion resistance, freeze-thaw resistance and strength. However, this type of concrete is highly susceptible to the deleterious effects of both autogenous and drying shrinkage. Both types of shrinkage occur when water leaves small pores , (< 50 nm) in the paste matrix to aid in hydration or is lost to the surrounding environment. Autogenous deformation (self-desiccation) occurs as the internal relative humidity decreases due to hydration of the cementitious material. Drying (and subsequent shrinkage) occurs when water is lost to the environment and continues until the internal relative humidity is equivalent to the ambient relative humidity. Typically, the magnitude of autogenous shrinkage is less than that of drying shrinkage. These two types of shrinkage do not act independently, and the total shrinkage is the aggregation of the two shrinkage mechanisms. It is imperative to minimize the amount of shrinkage in restrained members, such as bridge decks, to reduce the cracking potential. Various methods have been researched to minimize both types of shrinkage. Two methods to that have been reported to reduce shrinkage were selected for further research; internal curing using pre-soaked lightweight fine aggregate (LWFA) and shrinkage reducing admixtures (SRAs). The purpose of this study was to determine the long-term drying shrinkage performance of these two methods while reducing the external curing duration of 14 days for new bridge deck construction as specified by the Oregon Department of Transportation. In addition to monitoring drying shrinkage, durability testing was performed on concrete specimens to ensure these shrinkage mitigation methods performed at levels similar to concrete with the current mixture design. Freeze-thaw testing, permeability testing and restrained drying shrinkage testing were conducted. It was concluded that the combination of SRAs and pre-soaked LWFA was the most effective method to reduce longterm drying shrinkage for all curing durations (1, 7, and 14 day). Additionally, for durability testing, it was found that the use of SRAs performed the best in freeze-thaw testing, chloride permeability and restrained shrinkage. / Graduation date: 2012

Alkali activated materials, especially when activated with waterglass, are subjected to substantial drying shrinkage that hinders their broader industrial application. The effect of shrinkage reducing admixtures (SRA), based on poly(propylene glycol), on drying shrinkage of alkali activated blast furnace slag (BFS) mortars was studied. The aim of this thesis is to determine the efficiency of SRA as well as the influence of different type of alkali activator with varying silicate modulus on drying shrinkage characteristics. It was observed that the high amount of alkalis positively influenced the effect of SRA. The higher the amount of alkalis, the lower the drying shrinkage was. It also caused more water to be incorporated in the alkali activated structure and prevent it from evaporation. Thus, the weight change of such mortars was the lowest. Reduced effect of SRA on mechanical strength properties was observed in mortars with low amount of alkalis which was connected with delayed hydration resulting in insufficient amount of created C-S-H gel. The presented thesis further discussed and underlines the role of different kinds of alkali ions as well as their amount on the properties of alkali activated BFS systems.

Volume changes are one of the priority characteristics of concrete that plays an important role place mainly in the durability of structures as such. These low volume changes are required especially for structures as: industrial concrete floors, massive structures and waterproof structures. One of the possibilities in reducing these changes is the use of mineral admixtures with suitable grain curve of aggregate. Another possibility is the use of shrinkage reducing admixtures. There can occur problem with efficiency (long term age) with other components of the mixture. Therefore, the effort of this work is to use the avaible processes for maximum reduction of shrinkage and hydration temperatures.