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Item Characterization of Mechanical and Microstructural Properties of FA and GGBS-Based Geopolymer Mortar Cured in Ambient Condition(2021) Prasanna K.M.; Tamboli S.; Das B.B.Fly ash-based geopolymer mortars require heat curing to achieve its properties, which limits its practical application at ambient conditions. The present study was aimed to accomplish the need for application of fly ash-based geopolymers for practical viability without any heat curing by inclusion of ground-granulated blast furnace slag (GGBS). The results revealed that inclusion of GGBS as a partial replacement to fly ash (FA) in geopolymer mortar, which is cured in ambient curing condition, can be able to achieve required setting time and compressive strength. Amalgamation of GGBS with class FA as binder in geopolymerization lend a hand to attain compressive strength as well as setting time which is analogous to ordinary Portland cement (OPC). Microstructural properties were studied using scanning electron microscopy. © 2021, Springer Nature Singapore Pte Ltd.Item Application of Andreassen and Modified Andreassen Model on Cementitious Mixture Design: A Review(2021) Snehal K.; Das B.B.Cement is a widely used construction material and its consumption on large-scale causes environmental degradation; thus, more emphasis is being given on industrial by-products as alternative materials to cement for their sustainable usage. It is necessary that varying particle size of supplementary cementitious particles is to be used for filling the voids to form a dense particle-packed concrete. The selection of right combination of material is tedious job by trials involving different replacement materials and the resultant concrete may show unexpected results; thus, a more suitable method is the selection of materials based on optimum packing of particles. To select the optimum size of replacement materials particle packing models are essential, so that a low-cement concrete can be prepared which will be ecological as well as economical with improved density, low porosity and high compressive strength. It is found that there are different models have been developed to achieve optimal packing. However, application of Andreassen and modified Andreassen models for the particle packing of multiple ingredients of cementitious matrix found to be largely being accepted by the researchers. This paper reviews the application of Andreassen and modified Andreassen models for the effective particle packing investigations on cementitious particles. It also reviews the software’s employed for designing various cementitious mixtures based on Andreassen and modified Andreassen models. © 2021, Springer Nature Singapore Pte Ltd.Item A Review on Mechanical and Microstructure Properties of Reinforced Concrete Exposed to High Temperatures(2021) Goudar S.K.; Gedela S.K.; Das B.B.This paper presents the recent research progress on the response of concrete exposed to fire or high temperatures. The main highlight of this review paper is a compilation of previously reported data regarding the variations in mechanical properties and microstructure properties of concrete when exposed to high temperatures. The concrete structures get deteriorated at the macro- and microscopic levels due to high-temperature exposure. The macro-level damages can be measured with degradation in mechanical properties such as the reduction in compressive strength, weight loss, changes in elastic properties, reduction of bond strength in reinforced concrete, etc. The macro-cracks on the surface of concrete causes spalling which can be observed after exposing the concrete samples to more than 300 ℃. The compressive strength of the concrete reduces slightly till 400 ℃, and when the temperature increased to 600 ℃, there was an exponential reduction in the compressive strength of concrete. Another important parameter is bond strength degradation, which plays a crucial role in durability issues. To understand the deterioration phenomenon and changes in mechanical properties, the changes at the level of the microstructure of concrete need to be understood. Dehydration of products causes deterioration of mechanical properties and weight loss of concrete when exposed to high temperatures. At different temperatures, the microstructure changes and the response of hydration products such as calcium hydroxide (CH), CSH gel, unhydrated cement and capillary water reported by previous researchers are compiled and discussed. © 2021, Springer Nature Singapore Pte Ltd.Item Fast Setting Steel Fibre Geopolymer Mortar Cured Under Ambient Temperature(2021) Prasanna K.M.; Theodose I.; Shivaprasad K.N.; Das B.B.Cement and cementitious materials are being used worldwide as the most popular multipurpose construction materials but the greenhouse gas such as carbon dioxide (CO2) produced during its manufacturing process creating a huge environmental hazard, thus efforts have been made for alternative binders. Geopolymer binder is new age binder alternative to ordinary Portland cement in infrastructure projects because it is produced from eco-friendly and industrial waste materials. This study was aimed to produce fast setting with ground-granulated blast-furnace slag (GGBS) in fly ash-based geopolymer mortar incorporated with steel fibres cured under ambient temperature. In this research, alkaline to binder ratio was varied from 0.5 to 0.8, crimped steel fibre are varied from 0.5 to 1.5% by total volume of binder and combination of fly ash (FA) and GGBS (100%:0%, 90%:10%, 80%:20%, 70%:30%, 60%:40% and 50%:50%) as binder were used for preparation of fibre geopolymer mortar. The tests conducted include stetting time and flowability of geopolymer mortar, compressive strength and microstructural characterisation of steel fibre geopolymer mortar. The tests for compressive strength were carried out on standard size of mortar samples at curing period of 3, 7 and 28 days. It is noted from the test results that increase in GGBS content setting times were decreased; however, the compressive strength of fly ash-based geopolymer mortar increased. The highest compressive strength at 28 days of curing period was found to be 69.5 MPa, which is obtained with content of 1% of steel fibres and alkaline to binder ratio of 0.6 with 50%:50% binder’s proportions. Further, it is observed that the incorporation of steel fibres in plain geopolymer mortar have enhanced the compressive strength and optimum dosage of fibres was found to be 1%. © 2021, Springer Nature Singapore Pte Ltd.