Experimental methods to determine the feasibility of steel slags as supplementary cementitious materials

The hydration heat evolution of low clinker cements is studied in a dependence on the testing method and temperature. Four substitution rates of ordinary Portland cement by ground granulated blast furnace slag or siliceous fly ash were used—10, 30, 50 and 70 %. In all cases, the water/binder ratio of the cement paste was 0.5. The heat evolution and the heat evolution rate were monitored over 72 h with the use of two testing methods. The isothermal measurements were carried out with the use of TAM Air isothermal calorimeter at 20 and 50 °C. The heat evolution was also determined with the use of a semi-adiabatic calorimeter. Part I of the paper presents the results of the experimental tests and discussed the influence of mineral additives on the hydration heat evolution.

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Heat of hydration of low-clinker cements: Part I. Semi-adiabatic and isothermal tests at different temperature

Traditionally fly ash is thought to be glassy, spherical particle originating from pulverized coal combustion (PCC) at temperature up to 1700 °C. However, nowadays fluidized bed combustion (FBC) technology is spreading quickly around the world as it is an efficient and environmentally friendly method. FBC is also able to utilize mixtures of low-grade solid fuels (e.g., coal, lignite, biomass, and waste) that have fluctuating quality, composition, and moisture contents. However, this leads to a high variation in the produced fly ash quality, unlike PCC fly ash, and hence challenges when attempting to utilize this fly ash. In this study, the utilization of fluidized bed combustion fly ash (FBCFA) was reviewed using the Scopus database. The most promising utilization target for FBCFA from biomass combustion is as a fertilizer and soil amendment. In construction, the FBCFA from various fuels is utilized as cement replacement material, in non-cement binders, as lightweight aggregates and cast-concrete products. Other types of construction applications include mine backfilling material, soil stabilizer, and road construction material. There are also other promising applications for FBCFA utilization, such as catalysts support material and utilization in waste stabilization.

http://jultika.oulu.fi/files/nbnfi-fe2020061042520.pdf

Utilization of Fly Ashes from Fluidized Bed Combustion: A Review

Evaluation of compatibility of neutron-shielding boron aggregates with Portland cement in mortar

Acceleration of cement hydration – A review of the working mechanisms, effects on setting time, and compressive strength development of accelerating admixtures

Calorimetry was applied to an investigation of the early hydration of Portland cement (PC)–calcium aluminate cement (CAC) pastes. The heat evolution measurements were related to the strength tests on small cylindrical samples and standard mortar bars. Different heat-evolution profiles were observed, depending on the calcium aluminate cement/Portland cement ratio. The significant modification of Portland cement heat evolution profile within a few hours after mixing with water was observed generally in pastes containing up to 25% CAC. On the other hand the CAC hydration acceleration effect was also obtained with the 10% and 20% addition of Portland cement. As one could expect the compressive and flexural strength development was more or less changed—reduced in the presence of larger amount of the second component in the mixture, presumably because of the internal cracks generated by expansive calcium sulfoaluminate formation.

Calorimetry in the studies of cement hydration Setting and hardening of Portland cement-calcium aluminate cement mixtures

The calorimetric measurements were applied in testing the wastes collected from different furnaces in electric power plants as materials to be used in civil engineering. The fly ash materials were collected from two power stations based on different brown coal deposits and working with conventional and fluidized bed installation. The reactivity of high calcium fly ash from sub-bituminous coal combustion has been proved in calorimetric, conductometric, chemical shrinkage, and rheological measurements before their practical implementation on larger scale. Highly soluble components of fly ash contribute to the hydration products and structure formation, followed by setting and hardening of fly ash–cement mixture. These results have been the base of research project aimed in the innovative solutions dealing with the management of deposits of wastes generated as a result of coal combustion. The standardization and potential use on larger scale of these materials, necessary from the environmental point of view, seems to be the question of nearest future.

Calorimetry in testing waste materials from the brown coal combustion

Publisher Summary This chapter focuses on the production and the use of by-product gypsum in the construction industry. There are two groups of gypsum by-products that have been identified: chemical gypsum and desulphogypsum. The first by-product is produced by chemical processing and the second originates from the flue gas desulphurization installations in power stations. The compositions of the by-products differ substantially, primarily with respect to impurity content. Chemical gypsums are contaminated with the raw materials used in particular technologies, as well as the products of chemical processes. These contaminants affect the properties of by-product gypsum and subsequently formed binders. The desulphogypsum produced by the wet process is highly pure calcium sulphate dihydrate. Some impurities do not influence the reactions in the CaSO4–H2O system. However, if the SO2 sorbing agent is introduced to the flue gas stream without de-dusting or directly to the furnace, complex desulphurization products are formed.

Marek Gawlicki

Papers

Calorimetry in the studies of cement hydration Setting and hardening of Portland cement-calcium aluminate cement mixtures

Calorimetry in testing waste materials from the brown coal combustion

Production and use of by-product gypsum in the construction industry

The reaction of calcium aluminates with some basic solutions