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Tulaganov Abdukabil Abdunabiyevich, Doctor of technical sciences, professor, Rector of the Bukhara State University, Uzbekistan E-mail: abdukabiltulaganov@gmail.com Mukhamedbaev Abduvali Abdusattarovich, Candidate of technical sciences, docent, Tashkent Chemical-Technological Institute, Uzbekistan E-mail: sciencecemtech@mail.ru Atadjanov Shavkat Yusupovich, Independent aplicant, Tashkent Institute of Architecture and Construction, Uzbekistan E-mail: shavkat.atadjanov@bekabad-cement.uz Mukhamedbaeva Masuda Abduvaliyevna, Master, assistant,
Tashkent Chemical-Technological Institute, Uzbekistan E-mail: sciencecemtech@mail.ru
CEMENTS WITH REDUCED COMPOSITION OF PORTLAND-CEMENT CLINKER
Abstract. The results of studies to reduce the amount of clinker in the cement without lowering the grade are presented. As a partial replacement of clinker, it is proposed to use a mineral additive consisting ofbasalt and steel slag. Keywords: cement, clinker, mineral additive, basalt, steel slag, grade.
Introduction
One of the effective directions of reducing energy costs in the production of cement is the decreasing the clinker part on the behalf of using other structural components of cements. These measures give also the possibility of the decreasing the critical emissions of carbon dioxide into the atmosphere solving the ecological issues of the production.
The term "Composite Portland cement" is used by the European standards into the cements where as a fundamental composition of the component granulated blast-furnace slag, amorphous siliceous rocks, natural pozzolan, limestone, lime ash are used to the combinations of these cements with each other [1].
In the world cement industry there is a tendency of substantial reduction in the share of the clinker in the cement. According to the data [2] in 1990 the percentage of the clinker in the cement was 0.9 kg/kg, in 2003 it was reduced to 0.85 kg/kg, and in 2010 it was 0.80 kg/kg. It means that 0.20 kg/kg of the cement consists of alternative substances, which are considered as the mineral additives.
In parallel with the development of human civilization the issues of the pollution of environment with the wastes of the technological origin are rising. In relation with that the works on the protection of the environment, conservation of nature and their transfer to the next generation in its unmodified form are in progress all over the world.
There are many reasons of usage of wastes. Firstly, they could be used to improve the properties of the cements, on the other hand -for the reduction of the share of the clinker in the cement. Namely, the reduction of the clinker in the cement is reached by the reduction of emissions of CO2.
With the intensification of the requirements for the protection of environment and the balanced usage of natural resources, it is understandable that there are efforts to reduce the cost of the manufactured goods. In this case one of the perspective directions is the usage of steel smelting slag in the production of cement after its fractioning and magnetic enrichment.
Steel smelting industry is one of the important branches of the economy. Technology of the production of steel and steel smelting production is energy and resource-intensive process. In the process of steel smelting production, besides to the metal slag which is the waste of the production process is formed. Slags of steel smelting are stored in the slag-heaps, as a result needs the maintenance of special treatment for increasing the effectiveness of their usage. It is possible in the process of mechanical, chemical and thermal activation. The most perspective, according to our point of view is the mechanical treatment with the consecutive division into fractions. The intervening magnetic separation of the grinded slag allows excluding from the structure of the slag magnet attractive components. This enrichment of the wastes allows
CEMENTS WITH REDUCED COMPOSITION OF PORTLAND-CEMENT CLINKER
the realization of ideas on their processing in the construction materials includingcement.
The authors [3] determined that the possibility of the introduction of the 15% of this slag as an additive into the cement. The researchers [4] studied the main characteristics and possibility of the usage of steel smelting slag as anadditive. It was shown [5] that in the introduction in the steel smelting slags with the structure tolerable to decay 30% lime and 5% gypsum the astringent substance with the activity of 20 MPa.
Aim of the research. Our researches were intended for the study of thepossibility of the usage of steel smelting slag as an additive in the production of cement, without the worsening of the physical-mechanical properties and the reduction of type of astringent.
Characteristics of the materials and the methods of the research. In the survey the clinker with the structural content 65,3% C3S and 7,5% C3A, fractional waste of the steel smelting production with the size less than 5 mm (slag) and basalt rock was used.
The chemical structure of the basalt rock, mass% losses in the calcinations - 6.35; Si02-46.09; Al203-10.54; CaO-8.47; MgO-8.91. S03-0.81; Chemical structure of slag. mass (%): Si02-18.6; Al203-5.01-5.96; Fe203-19.50-20.50; CaO-41.38-42.10; Mg0-12.50-12.60; SO- 0.10-0.20; R203-0.18-0.22.
Supplements were added in diverse proportions in the grinding of clinker. Grinding of clinker with supplement was completed in the conditions of lab during 1 hour and 20 minutes and in the industrial conditions - according to the tech-
nological regulations. For the preparation of cement solution standard sand was used, and for bibbing - tap water was used. For identification of mechanical assurance factor of the cements beam - sample with the size 4x4x16 cm from the structure of cement : sand=1:3. Methodology of tests - standard.
Obtained data and their discussion. Manifestation of the hydraulic activity of the steel smelting slag is related with the fact that in its structure physical - chemical processes assistingin the increase of their hydraulic activity are undergoing. Quartz substances undergo isomorphs modifications and go into the more active form of siliceous rocks which assist to active bonds of CaO, evolved in the hydratization of cement minerals, and marl materials which are abundant in the structure of slags experience structural changes that's the kaolinite is dehydrated and its transition into the more active form - methakaolinite.
Mechanism of the process of hydratization and the solidification of composite cements could be presented in the following way. In the process of the hydratization of cement the alkalinity of the environment increases which will assist to the destruction of introduced mineral additives which in its turn will determine the process of hydratization en route to the reduction of the preparedness of the products of the solidification of the cement.
According to the results of the lab tests obtained, the introduction of the basalt and slag as amineral additive into the cement allows getting quality cement in its usage in the accessible local materials and the wastes of the production. The value of the durability corresponds to the requirements of GOST (table 1).
Table 1. - Results of the lab tests of cements
№ Supplement Tonine of grinding,% The time of clamping together, h-min. Durability, pressure, MPa
Basalt Slag starts ends 28 days
1. 8.0 7.0 92.0 2-35 4-45 40.7
2. 15.0 5.0 92.4 2-45 4-55 41.1
3. 8.0 8.0 92.0 3-05 4-55 41.0
4. 7.0 8.0 91.6 2-05 4-15 42.9
5. 8.0 7.0 88.0 2-35 4-55 40.9
6. 7.0 12.0 91.5 2-45 4-25 41.5
Table 2.- The results of the industrial tests of cements
№ Supplement Tonine of grinding,% The time of clamping together, h-min Durability, pressure MPa
Basalt Slag starts ends Steam 28 days
1 2 3 4 5 6 7 8
1. 8.0 7.0 87.2 2-45 4-45 24.2 40.4
2. 15.0 5.0 86.4 2-25 4-35 24.5 40.1
3. 8.0 8.0 87.6 2-05 4-35 24.5 40.1
4. 7.0 7.0 87.2 2-25 4-35 24.9 40.3
5. 8.0 7.0 87.2 2-25 4-45 24.7 40.0
1 2 3 4 5 6 7 8
6. 7.0 12.0 85.6 2-05 4-25 24.3 40.2
7. 7.0 9.0 87.6 2-25 4-45 24.5 40.4
8. 8.0 10.0 88.0 2-25 4-35 24.4 40.1
9. 8.0 9.0 87.6 2-05 4-35 24.2 40.8
10. 9.0 9.0 88.2 2-35 4-35 24.2 40.3
The results of the lab tests are tested in the pipe spherical mills having the size 2.6 x 13 m in the industrial conditions (table 2). With the production of test sample of cements, it was revealed that the introduction ofbasalt and slag into the cement allows to the increase of the water cement ratio. Average density of cement mixture varies between the range of26-27.75%. The presence basalt and slag extends the beginning of clamping for 10-40 minutes, and end to 20-30 minutes.
The longest time for clamping has the composition which has basalt 6-8% and slag 7-12%. Mechanical assurance factor of the Portland cements with the diverse slag tenor and basalt rock reaches to 40.1-40.8 MPa [6].
With the basalt composition of 8% and slag of 9% the assurance factor of the multicomponent cement reaches to the sample Portland-cement.
Conclusions. Consequently in the usage of the steel smelting slag it is possible to save part of the expensive clinker, recycle the wastes of the metallurgy, satisfy the requirements of the cement plant in the active mineral additive and produce
cement without the reduction of the assurance factor and the type of astringent.
In general the proposed multi component compositions of the cements on the basis of local raw materials and industrial wastes could be accepted to industrial output. The efficiency of the usage of additives depends on the quality of the clinker, type and quantity of introduced additive, and the multi com-ponential charge. The multiplication of components of the mix of the cement grinding, in some situations requires the establishment of extra measures in the introduction of mineral additives. But, the cheapness of the raw material and the wastes of the industrial output is the impulse not only for the reduction of the cost of ready products but also for the intro of measures in the usage of locally nontraditional raw material, protection of the environment in the industrially developed regions. Combing the several components of mineral additive it is possible to receive cement without worsening the physico-mechanical properties and the reduction of the type of astringent.
References:
1. Muller Ch. Performance of Portland-composite cement // Cement International.-1/2008.- P. 44-53.
2. Крайчук Л. А. Цементы с пониженным содержанием клинкера в мировой цементной промышленности // Строительные материалы. 2006.- № 9.- С. 45-47.
3. Cerjan-Stefanovic S., Rastovcan-Mioc A., Novosel-Radovic V. J. Mechanical properties of cement with addition of electric furnace lag // Metallurgija, Zagreb,- No. 2.- P. 93-98.
4. Stevula L., Madej J., Dyda M. LD-Steelwork slags: fundamental properties and behavior as concrete aggregate // Miner. Slov.- No. 2. 1996.- P. 135-140.
5. Шишкин В. И., Воронин К. М. Вяжущие из сталеплавильных шлаков // Современные проблемы строительного материаловедения.1998.- С. 202-205.
6. Патент UZ IAP 04771. Цемент / Ш. Ю. Атаджанов, Э. И. Курбанов Ф. Кадырова, А. А. Мухамедбаев, К. Шакамалов // Заявл. 06.12.2010. Опубл. 29.11.2013, Бюл.- № 11.
