Papers by Keyword: Pozzolanic Activity

Abstract: Sugarcane bagasse ash (SCBA) is a by-product of the ethanol and sugar industry. SCBA is generally used as fertilizer or dumped in landfill, which has led to increasing environmental problems. In the recent years, SCBA has been investigated in the field of construction materials due to its pozzolanic character. This research aims at examining some physical and mechanical properties of mortars with partial replacement of sugarcane bagasse ash from sugar cane refineries. In the present case, the cement substitution was made with SCBA at 0%, 15%, and 30% of the binder (Cement + ash). The physical and mechanical testing of the mortar was carried out to determine the effect of ash addition on porosity, density, flexural and compressive strengths of the mortar. In general, the findings revealed that the mechanical and physical behavior of the mortar mixtures improved over time because of pozzolanic effects. On one hand, the physical changes were relatively restricted and do not show a well-established trend. On the other hand, reduction of mechanical strength was observed with the addition of SCBA, and with a 15% cement replacement percentage, it is possible to obtain a material with favorable physical and mechanical properties.

Abstract: High the quality and reliability of hydraulic engineering construction is the basis of civil engineering technology. The use of mineral additives in hydraulic concrete decreases heat dissipation, contribute to a reduced adiabatic rise in the temperature of concrete, improve its performance characteristics and increase durability. Application of such materials will reduce binder consumption without the decrease of concrete properties and mostly even impoving the properties of mortar and concrete. An indirect method of pozzolanic activity evaluation of low-calcium fly ash, volcanic slag, volcanic tuff and waste basalt powder was applied in the study. The investigation shows that volcanic slag is additive with the least volume increase at age of 30 days and it has high pozzolanic properties. The results show that it can be used as base pozzolanic additive for economically and technologically effective hydraulic concrete, superior to non-additive concrete. Use of pozzolanic additives will positively affect the environment due to Portland cement use decrease and the utilization of waste dumps, decrease cost of concrete and a more rational use of natural resources and sustainable development.

Abstract: Massive coal gangue waste delivers environmental disasters in China. Finding an effective, efficient, practical and value-added approach for large-scale disposal of coal gangue waste is very urgent. In this study, thermal treatment approach was conducted on coal gangue waster with the goal to improve its pozzolanic activity so that considerable replacement of Portland cement can be realized. XRD analysis, IR analysis as well as the evaluation on mechanical properties of mortar specimen were carried out to optimize thermal treatment program. The results indicate that coal gangue waste can be efficiently treated at 850°C in less than 30min to obtain pozzolanic activity of 108% at 7 days and 124% at 28 days. And an industrial product also shows similar improvement in pozzolanic activity to the lab results, and indicates the potential for producing eco-efficient cementitious materials.

Abstract: It is introduced to use a portable spectrometer along with a calibration model for rapid quality control of metakaolin in situ. Verification of the calibration model for predicting the values of two indicators: total acid solubility and mass loss during calcination, indirectly characterizing the pozzolanic activity of metakaolin.

Abstract: Introduction of finely disperse mineral additives of natural and man-made origin to Portland cement in order to improve the indicators of its physical-mechanical properties and partially replace clinker is one of the urgent directions for solving the resource and energy saving problems, as well as environmental protection problems in the production and application of building materials. The expansion of the raw material base of mineral additives can be achieved by using calcined polymineral clays, which are common in many regions of the Russian Federation, including the Republic of Mordovia. The article presents the results of research on the effects of calcination temperature and time of thermally activated polymineral clays of the Republic of Mordovia on their physical-chemical efficiency in cement systems. According to the study results of dehydration processes of clay minerals using the synchronous thermal analysis, it is established that the optimum calcination temperature for clays of Nikitsky and Staroshaigovsky deposits located in the area of 500–800 °C. This temperature range corresponds to the processes of the initial crystal structure restructuring of clay minerals of the kaolinite and illite groups, associated with their dehydroxylation, which contributes to the transition of these phases to the active form. The optimization of calcination parameters of polymineral clays based on the study results of influence of their additives on the mixed cement binder activity confirmed the thermal analysis data. It was found that the production of mineral additives with the highest values of the activity index is facilitated by 2-hour heat treatment of clays at 700 °C. At the specified calcination parameters, the replacement of 10% of Portland cement with the additive of thermally activated Nikitsky clay allows achieving the mixed binder activity that exceeds by 3 % the same indicator of mixed binder based on Portland cement and high-quality metakaolin.

Abstract: The replacing part of Portland cement with thermally activated clays will reduce the "clinker factor", which in turn will reduce greenhouse gas (CO₂) emissions. The metakaolin activity by the lime absorption method from a saturated lime solution and by binding Cao from limestone dough was determined. It is shown that the metakaolin interaction products with Ca (OH)₂ are characterized by a multiphase and are composed mainly of hexagonal and cubic hydroalumination calcium and various basicity poorly crystallized calcium hydro-silicates. The results obtained allow the Metakaolin to be considered a new, hydraulically active pozzolanic additive.

Abstract: Currently the replacement of primary raw materials in cement production is relevant topic. One of the potentially usable materials can be recycled glass. But its disadvantage is tendency to agglomeration. This experiment describes the effects of the milling agents on the milling process of the glass powder. At first step seven different milling agents were compared among others and next the dependence between pozzolanic activity and specific surface are were monitored for two of them. The utilization of milling agents increased glass specific surface area significantly. Nevertheless, pozzolanic activity of the glass can be reduced when using milling agents because they may also act to a certain extent repellently to the reaction solution.

Abstract: In this work, the preliminary study about the use of secondary lead smelting slag (SLSS) as an addition to Portland cement is presented. SLSS is a waste from a Colombian secondary lead smelter. The chemical, physical and mineralogical characteristics of the raw materials were evaluated by X-ray fluorescence, particle size and X-ray diffraction. To assess the SLSS pozzolanic activity, the ASTM C618 standards were used. Additionally, cement pastes added with SLSS as Portland cement replacement in proportions of 0, 5, 10, 20 and 30% were prepared, to study the hydration process at 7, 14 and 28 of curing times. To determine the hydration products the technique of X-ray diffraction was used. Furthermore, the environmental test TCLP (Toxicity Characteristic Leaching Procedure) was performed in pastes with 28 days of curing time. Results showed that SLSS reported an index of pozzolanic activity of 87%, this value meets the standard (greater than 75%). The hydration process showed that since early curing time the waste presented a good reactivity. TCLP results satisfied the environmental standards. The outcomes showed that this waste could be used as a partial replacement of Portland cement.

Abstract: Use of waste materials in concrete is now a global trend for efficient waste management so as to achieve a sustainable green environment and with the added advantages of preserving the natural resources as well as producing a better performing concrete. This study examined the properties of concrete containing ground waste glass powder (GP) as partial replacement for cement. The waste glass was finely grounded into powder and the morphology imagery of the powder materials was carried out using scanning electron microscopy (SEM). Moreover, the chemical composition of the glass powdered material was determined using X-ray fluorescence (XRF). Laboratory tests were carried out to determine the strength activity index, workability, split tensile and compressive strength properties of the concrete with 0%, 15%, 18%, 21%, 24%, 27% and 30% partial replacement of cement with the ground waste glass powder. The results showed that the oxides composition of the glass powder meets the requirements for pozzolanic material, while the SEM morphology shows materials of amorphous flaky solid masses, and based on the 28-day strength activity index, concrete containing 21% cement replacement shows a higher strength index above therecommended 75%. It was also observed that workability of the concrete reduced with increase in percentage glass content while significant improvement of the compressive strength of the concrete was achieved at 21% cement replacement, after which a decrease in strength with increasing percentage glass content was observed. The revealed results were confirmed by the microstructural examination using SEM showing a denser concrete at 21% cement replacement but increase porosityas the glass content increases. However, a decrease in split tensile strength was observed with increasing glass content. The results clearly showed that it is possible to produce moderate strength sustainable concrete for structural application using 20% glass powder as cement replacement.

Abstract: Waste ceramic powder originating from the contemporary hollow bricks production is studied as a supplementary cementitious material in mortar composition. For the ceramic powder and cement, the measurement of chemical composition is done using XRF analysis. XRD device is used for the amorphous phase content measurement. The particle size distribution of ceramics and cement is accessed on a laser diffraction principle. Pozzolanic activity of ceramic powder was determined by the modified Chapelle test. The blended binder containing ceramic powder in an amount of 8, 16, and 24% of mass of cement is used for the preparation of mortars which are then characterized using the measurement of basic physical properties and mechanical properties. Among the basic physical properties, bulk density, matrix density and total open porosity are measured. The mechanical resistivity of mortars with blended binder is accessed by the compressive strength, flexural strength, and dynamic Young’s modulus measurement. Additionally, pore-size distribution of the developed mortars is analyzed using mercury intrusion porosimetry. Experimental data shows that an application of 24% waste ceramics in the blended binder provides sufficient mechanical resistivity of the mortar.