Removal of hydrogen sulfide gas using coal fly ash – blast furnace cement composite

The number of complaints regarding offensive odors from service industries, such as restaurants and garages, has recently increased. In this study, we aimed to develop an adsorbent for hydrogen sulfide gas derived from domestic wastewater and reveal the mechanisms of its removal. The adsorbent used for hydrogen sulfide gas removal was prepared by mixing coal fly ash and blast furnace cement with a mixing ratio of 87:13 by mass percentage. The optimum calcination temperature of the adsorbent was 700 °C to achieve a high removal performance for both dry and humid hydrogen sulfide gas. The X-ray absorption fine structure analysis revealed that hydrogen sulfide was removed on the adsorbent by oxidizing to sulfate. A pilot-scale experiment was conducted to evaluate the removal performance of hydrogen sulfide gas derived from domestic wastewater using the developed adsorbent. For a week, the average removal percentage of hydrogen sulfide gas derived from domestic wastewater remained at 99.1%. Therefore, the developed adsorbent for hydrogen sulfide gas is promising and cost-effective for promoting the recycling of coal fly ash.

Study of the influence of magnetized ferromagnetic additives on the processes of cement hydration

One of the essential tasks for a sustainable future is to reduce harmful emissions into the atmosphere significantly. Cement production is the world’s largest industrial carbon pollutant, accounting for 8 % of global emissions. More than 2.2 gigatons of carbon dioxide are emitted into the atmosphere every year. Therefore, reducing the energy intensity of products and reducing the number of harmful emissions in cement production is becoming critical. One strategy to reduce cement production emissions is to reduce the most energy-consuming component in cement – clinker. In this case, various activation methods are used for maintaining the same level of cement activity. One of these methods is the impact on the hardening binder with magnetic fields. The paper presented a study of hydration processes of blast-furnace cement activated by a magnetized ferromagnetic additive. The work established that the introduction of pre-magnetized ferromagnetic dust into blast-furnace cement composition has an activating effect on binder hydration. It shows that activation occurs both in the initial and long periods of hardening. The nature of the mutual influence of the components of the hydration system alite-lime-slag in a modified binder was revealed. The investigation determined that the ferromagnetic additive, intensifying the process of slag hardening, increases the proportion of hydrated slag by 1.5-2 times. It was revealed that the formation of the ettringite framework in the modified binder’s gel is completed within one day. It is shown that in the subsequent periods, hydration of aluminates occurs mainly due to the formation of tricalcium aluminate hexahydrate (C3AH6), which excludes destructive processes in the late periods of binder hardening. It has been established that under the action of a ferromagnetic additive, the degree of crystallization of hydro silicates in the modified binder increases.

Acoustic emission method as a tool for the assessment of influence of the temperature variation on destructive processes created in early age concrete

During the early age concrete treatment (curing and hardening) the damage process appears i.e., microcracks in the cement paste, propagation of internal microcracks, and formation of microcracks on the surface of concrete that affect concrete. It can be the serious source that initiate cracks that will propagate in the further loading stage, thereby affecting the overall strength and durability of structures. Hence, it is quite important to have a tool to identify the damage processes created up during the early age concrete treatment. The Identification of Active Damage Processes (IADP) acoustic emission method, modified to suit the tests on non-loaded concrete, was applied to determine and locate the damage processes that appears during the hardening conditions taking into account the temperature fluctuations on which construction structures are exposed (constant temperature of 22ºC or cyclic temperature variations in the range -5ºC/+42ºC) in non-loaded concrete produced with basalt aggregate and blast furnace cement. It is shown that the modified IADP method, can be used to assess the influence of the temperature variation on damage process in early age non-loaded concrete. As an example, concrete produced with basalt aggregate and blast furnace cement was used.

Analysis of the Properties of Expansive Concrete With Portland and Blast Furnace Cement

The properties of expansive concretes made of two types of cement: Portland cement CEM I and blast furnace slag cement CEM III were tested. The expansion of the concrete was caused by using an expansive admixture containing aluminium powder added in an amount of 0.5; 1 and 1.5% of cement mass. It was found that the compressive strength of concrete with CEM I decreased after using an expansive admixture in the amount of more than 0.5% of the cement mass. The compressive strength of concrete with CEM III decrease after addition of admixture in the entire range of dosages used. On the basis of electrochemical measurements, it was found no influence of an expansive admixture on corrosion of reinforcing steel. The use of an expansive admixture causes a slight increase in the effective diffusion coefficient of chloride ions in concrete.

Preliminary Study on Additives for Controlling As, Se, B, and F Leaching from Coal Fly Ash

The application of paper sludge ash as an additive in controlling the leaching of trace elements has been satisfactorily effective to date. Previous studies have found that paper sludge ash has a promising effect in controlling the leaching of arsenic, selenium and boron. The content of calcium oxide in paper sludge ash is believed to be one of the important factors in decreasing the concentration of trace elements in leachate. Therefore, this study aimed to verify the effect of paper sludge ash in the leaching process and to propose an effective and applicable suppressing material that can control the leaching of As, Se, B and F simultaneously. In light of this aim, Ca(OH)2, PS ash 8 and blast furnace cement (BF cement) were tested as single and mixed additives in two different coal fly ashes (FA C and FA H). The results indicate that the application of a mixture of additives is necessary to control the leaching of trace elements. A mixture of PS ash 8, Ca(OH)2 and blast furnace cement (BF cement) was proposed to be an applicable and suitable additive that could suppress arsenic, selenium, boron, and fluorine leaching simultaneously.

Results of the freeze resistance test, swelling index and coefficient of permeability of finegrained mining waste reinforced with cements

The article presents the result of laboratory tests for mining waste with grain size of 0 to 2 mm stabilized with cement. Used for stabilization of cement CEM I 42.5 R and blast furnace cement CEM III / A 42.5N - LH / HSR / NA and a plasticizer sealant. Cement was added to the mining waste test in the proportions of 5 - 8% in relation to the skeleton's weight. For the cemented samples, the freeze resistance test, swelling index, coefficient of permeability and pH of water leachate were tested. The addition of a cement binder resulted in diminishing the water permeability of mining waste and limiting the leaching of fine particles from the material.