SCIENTIFIC FUNDAMENT, INNOVATION, PRACTICE AND BENEFITS TO USE ZEOLITE TUFF IN CEMENT MANUFACTURING IN GEORGIA

Rajden Skhvitaridze 1 ,Teimuraz Kordzakhia 2 ,Giorgi Tsintskaladze 3 ,Irakli Giorgadze 1 and Shalva Verulava 1 . 1. Ph.D., Scientific Center "NanoDugabi", Georgian Technical University, Tbilisi, Georgia. 2. Ph.D. Leading Scientist, Ivane Javakhishvili Tbilisi State University, P.Melikishvili Institute of Organic and Physical Chemistry, Tbilisi, Georgia. 3. Ph.D. Leading Scientist, Ivane Javakhishvili Tbilisi State University, P.Melikishvili Institute of Organic and Physical Chemistry, Tbilisi, Georgia. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

212 Local economic problem. Deficiency and high durability of mineral cement additives. Since 1926 cement plants of Georgia used Ani (Armenia) pumice as a mineral additive in the process of cement grinding, and since 1956 also the granulated blast furnace slag of the Rustavi Metallurgical Combine. After the collapse of the Soviet Union, starting from 1991 the pumice import from Armenia had been shut down due to the appearance of customs duties on the import of materials and a rise in the cost of transportation, and blast furnaces and slag granulation in Rustavi stopped functioning. There was a shortage of materials used as a mineral additive. Cement manufacturers had to look for alternative materials for use in production. The way out of the situation was an innovative technical solution: -using non-traditional for the cement industry of the former USSR's mineral additives in the production of cement, for example zeolite tuff.
Zeolite tuff (ZT). "HEIDELBERGCEMENT GEORGIA", "EVROCEMENT" and other companies began to produce cement of the types EN 197-1: CEM II / B 32.5; CEM IV / B 32.5 and EN 413-1 -MC 22.5X, which contain 5 -40% ZT of the Dzegwi or Khandaki fields. It should be noted that they do not use ZT in the production of cement in other countries. Georgia and the Georgian cement producers are pioneers of using ZT in cement grinding process, which has several grounds. Let's consider them: Economic grounds. Obtaining high-tech and competitive systems based on local raw materials is one of the priority directions of Georgia's economy. ZT reserves in Georgia reach 300.0 million tons. It is an easily processed rock (Mohs hardness 3-5); It is extracted by open method; The distance from the existing ZT deposits to cement plants is only 15 -70 km; ZT in the cement "replaces" the most expensive component -clinker. All this is a precondition for the low cost of the produced cement.
Legal grounds. The agreement on Georgia's association with the European Union has created the need to develop technologies to protect the environment in Georgian cement plants. One of the ways to reduce the emission of harmful compounds into the environment is the decrease in the proportion of clinker during cement grinding, and correspondingly an increase in the proportion of mineral additives [1,2,3]; Formally, EN 197-1 [4] regulates that it is allowed to use a material which contains more than 25% SiO 2 in its composition as a mineral pozzolanic cement admixture. ZT meets the formal requirement of EN 197-1, because it contains at least 40% SiO2. Starting from 2014, the inclusion of ZT in cement is regulated in accordance with GOST R 56196-2014 [5], which must be carried out in accordance with the criteria (GOST 24640-91. [6]): "decrease in the proportion of clinker is greater than the decrease in cement activity" (All these normative documents are valid for the territory of Georgia).
Physical-chemical, and scientific grounds. Based on many years of research [7], we have been convinced that using a mineral additive of any type in the structure of the cement in an amount of up to 7%, increases its activity (strength), and above this limit -decreases. This dependence is represented by hyperboloid curves for various types of additive and cement ( Fig. 1). The graph shows with dotted line the change in cement activity (strength) when including and increasing the amount of the mineral additive of river crushed stone, ZT or basalt in the range of 5-7%; after increasing the amount of mineral additive above 7% -the activity (strength) of cement begins to decline. All this is explained by the fact that 213 small amounts of mineral additives stimulate the formation of crystalline hydrate-ettringite [7] during hardening of cement, which is confirmed by the well-known Dr. H. F. W. Taylor [8]. A question arise: -In what quantity is it possible to add mineral additives in cement composition? The answer: -During the production of cement, it is necessary to observe the criteria: "the decrease in the proportion of clinker in cement is greater than the decrease in cement activity (strength)" [6]. Inclusion of 5-7% of activated ZT in the composition of cement will allow to obtain cement with a strength of 62.5 MPa.
Since 1926 they used the Khandaki tuff in the grinding of cement at the Kaspi cement plant in Georgia, as a pozzolanic mineral additive, along with pumice stone, which required drying. Its humidity was in the range of 13-20%, which increased the cost of production and prime cost of cement and therefore, it's not been used from the 60s of the 20th century. Then they did not know that it contains 50-85% zeolitic mineral clinoptilolite {(Na, K) 6 [Al 6 Si 30 O 72 ] 24H 2 O}, which has a crystalline structure consisting of nanopores with diameters of 0.4-3.0 nm. The calcium tosilmorite-CSH calcium hydrosilicate gel formed during hardening of cement is a dispersed (3d) reinforced material with nano sizes.
Hypothesis: interaction of ZT with CH, i.e. the reaction of pozzolanization will promote the formation of waterresistant nanoscale compounds with a fibrous-acicular plate habit: tobermorite CSH, stratlingite C 2 ASH 8 , and externgite C 3 A 3CaSO 4 31H 2 O, which leads to their wreath, (3d) self-nano reinforcement of the cementitious cement structure and a sharp increase in its strength (activity) [1.8.9]. To use ZT, it is necessary to know not only its chemical composition and structure, but also its behavior when grinding cement and making concrete, because during cement grinding the temperature in the mill reaches 200 ° C and ZT is being heated. Fig. 2 shows a derivatogram of ZT containing 60% clinoptilolite, from which it is evident that it is dehydrated at 130 ° C -(Hypothesis), this will lead to its activation -water found in the nano (0.4-3.0 nm) pores of clinoptilolite releases space -for example, for Ca (OH) 2 , i.e. to intensify the reaction "pozzolanization" [1,9], which will further contribute to an increase in the stability of the structure and durability of concrete.
On the diffractogram of crude ZT (Fig. 3 Technological grounds. During milling in tube ball mills, the cement heats up. It happens because, according to the data [10], the energy consumed at the grinding process (400 kWh) is used directly for grinding only partially, and 87% (390 kWh) is converted to heat, which causes dehydration of the water-containing components of the ground mixture -for example ZT. This heat can be used for drying a wet component (e.g. ZT) milled cement mixture. The theoretical dehydration temperature of ZT according to DTA is 130 ° C. ZT with grain sizes of 32 μm will be more easily and more rapidly dehydrated than with grain sizes of 80 μm, which leads to its Nano activation by absorption of Са(ОН) 2 . Proceeding from this, it can be assumed that the higher the temperature of thermal activation and the surface area of ZT, the higher will be its activity in the absorption of Са(ОН) 2 and the cement purity. The chemical composition of ZT used in the cement industry of Georgia is presented in Table 1, and the mineralogical composition and expected neoplasms in cement stone are shown in Table 2. 214  LAB Experiment. The average size of grains of any material is connected with a surface by the ratio Dm = 600,000 / h, x s cm; Hence, S = 600,000 / γ x Dm cm 2 / g. Here: S-ud.p. Cm 2 / g; Dm is the average particle size in microns; γuid weight of the material. ZT of the Dzegvi field was milled to the full passage through sieves №008 (80 μm) и №0032 (32 μm). Then the surface of the experimental ZT powders will be: S80 μm = 600000/2.1х 80 = 3571 cm 2 /g. S32 μm = 600000/2.1х 32 = 9523 cm 2 /g. The surface of the ZT at a grain size of 32 μm is 2.66 times larger than at 80 μm.
The crushed ZT was divided into 3 parts. 1-part before displacement with cement for 24h was held in a desiccatorat 20 0 С; 2-part before displacement with cement for 1 h dried at 100 0 С; 3the part before displacement with cement was also dried for 1 hour at 130 0 С. Thus, 6 tested ZT were prepared: ZT-1 (80 μm-20 0 С); ZТ-2. Testing the activity of ZT cement with grain sizes of 32-80 μm, according to ASTM C 311-05 [10], showed that the cement activity index with natural ZT of the Dzegvi field is higher than 75 and is 2days -76.7 (ZT-1) and 90.0 (ZT-1); after 28days -88.8 (ZT-1) and 100.9 (ZT-1); i.e. it is a hydraulic active material ( Table 3). The activity test according to ASTM C 311-05 procedure of the same ZT, but ground to particle sizes of 80 μm and 32 μm, and heat treated at 100 0 С and 130 0 С showed that grinding ZT to 32 μm in size and heat treatment at 100-130 0 С sharply increases the ZT activity index to 93.3 -118.5 respectively (ZT-2 -ZT-6). The practice of applying ZT with the use of energy efficient innovative technology. Since 2001, "Eurocement" uses Khandaki ZT as a mineral additive for grinding cement (Table 1). It is characterized by high humidity (13 -20%;), and requires drying -which is economically impractical at the current energy situation. Based on the situation, we have developed a highly economical way of drying mineral additives. The essence of the method is that the mineral additive is fed to the clinker conveyor for drying, and for the time the hot clinker, which has a temperature of 50 -300 0 C, is fed to the conveyor -onto a layer of moist mineral additive (Fig. 4). The technology is patented in the former USSR and in Georgia [12]. The answer: when grinding cement in a separator mill, the temperature inside the mill rises to 70-150 0 С. If the moisture content of the milled material does not exceed 6% [10], intensive heat exchange takes place, and therefore, simultaneously with grinding, with the help of the heated medium of the mill, drying or evaporation of water occurs, or dehydration or dehydration of the deformable material-that is, dehydration and activation of ZT, and the temperature of the cement upon leaving the mill is 40-60 ° C. Thus, grinding cement with the inclusion of ZT in a separator mill is an innovative energy-efficient technology! As a result, the strength of the cement obtained is higher, compared to cement in a mill without a separator.

Results and Recommendations:-
 ZT -without reducing the technical properties of cement and concrete, cement can be introduced in an amount of up to 40% by weight of the clinker, which is very important from an economic point of view, because the share of the most expensive and energy-intensive component in cement, clinker, decreases. This will also reduce the emission of harmful gases into the atmosphere by 40%: the CO 2 emission will decrease from 0,585-0,640 t/t.kl.up to 0,351-0,384 t/t.kl.; Emission of SOx from 1,150-9,180 kg/t.klup to 0,690-5,508 t/t.kl.; Emission of NOx from 0,285-1,140 kg/t.kl.up to 0,171-0,684 t/t.kl., which is very important from an ecological point of view.  Introduction of Dzegvi ZT into the cement composition in an amount of 5 -7%, after grinding in a separator mill, will allow to obtain cement with a strength more than 62.5 MPa.