Historical Development of Material Properties of Concrete with Addition of Fly-ash

Transcription

1 Historical Development of Material Properties of Concrete with Addition of Fly-ash PAVEL PADEVĚT, ONDŘEJ ZOBAL Department of Mechanics Czech Technical University in Prague Thákurova 7, 66 9, Prague 6 CZECH REPUBLIC pavel.padevet@fsv.cvut.cz ondrej.zobal@fsv.cvut.cz Abstract: - The article is focused on the measuring unique data obtained from a water dam Orlik, situated in the Czech Republic. Orlik dam was built 6 years ago from concrete. First time in the world, fly ash was added to concrete, high number of reasons, reduce heat of hydration. Even today, after more than half a century building is in excellent condition. Based on historical sources and current measurement is possible to obtain valuable data about the material, which is currently very interesting. Adding fly ash to concrete can improve the properties of concrete and also to process waste material - ash. Experimentally obtained data are presented in the article, especially tension strength and compression strength. Key-Words: - Concrete, Fly-ash, Dam Orlik, Admixtures, Splitting Test. Introduction Waterworks Orlik is also currently one of the most important buildings built in the Czech Republic. The main importance of dam Orlik (Fig.) is the production of electricity. A side benefit is flood control, dam Orlik is part of the Vltava cascade, which ranks next Lipno dam lake, Hnevkovice, Kořensko, Kamyk, Slapy, Stechovice and Vrane []. In the period of construction between the years 96 to 96 years, was one of the most expensive buildings, the price was around billion crowns. The building had to be used in addition to large financial costs and a huge amount of material. Unusually for the period when construction took place, the proposal works consulted with researchers, a very important role played in this regard, employees of CTU in Prague. Production of Concrete Under the proposal was needed to produce 4, cubic meters of concrete per month, total over million m of concrete. Production was fully mechanized and automated. Due to higher prices and the unsuitability of crushed stone from local quarries and gravel terraces of the Vltava River Elbe was imported gravel. Construction of the dam Orlik The first part of the concrete dam was concreted in 96 and in 96 the building was transmitted to the operation. Although it seems almost incredible, everything was catching on the scheduled date. The intensity of construction is the fact that 8 % of the total building volume was concreted in two and a half years. Overall, the dam has been used 9, cubic meters of concrete []. Fig. : Dam Orlik; view from top of dam to the operating objects on the bottom of dams. ISBN:

2 The aggregates were sorted into five fractions (-, -, to, -, - mm) and transported through the construction of trains. It was transported over. million m of aggregates. Furthermore, it was transported to a construction of thousand tons of cement. Cement was used to cement plant Kraluv Dvur, but needed a thorough inspection, because of its very varied quality. It was established construction site inspection, and during the 9 construction was carried out various tests and non-destructive measuring the development of properties of concrete. The quality of production data indicates 9-day strength of concrete, which reached the concrete container labeled B8, % of prescribed values and core concrete B7 to 6 % of the values specified. Singleton was a way of continuous production of concrete in three horizontal mixers, which were needed to produce a huge amount of concrete, plus a total of different types of concrete. This was achieved by full mechanization and automation, and two alternating -hour working shifts in work week and a half days on Saturday and Sunday. The main work of concreters was to create body of the dam. Barrier strips were m wide; meters long; m high; cubic capacity of one blade was 9 m. Concrete was prepared in the traditional way with layers of cm "two manly" vibrator, which weights were 86 kg and a frequency of vibration the 9 cycles / min. Fig. : Temperature distribution over the vertical (left picture) and the stresses in the concrete (right picture), inside of the block. 4 The Role of Ash in Concrete Dam During the initial placement of concrete dams in 98 (about blocks, m of concrete) had a conventional concrete mix composition, when it was used to a cement. This also took place concrete in a relatively quick tempo to 4 m per month. After concreting, the arrival of colder periods began to appear on the block cracks. Cracks were typically mm wide and deep mostly to m, max m. To illustrate the problem of cracked concrete were measured temperature and temperature gradient was found to. C. The surface temperature was measured at C and within a block of +4 C at days old concrete. For the cause of the problem was the heat of hydration is determined. The tension in the concrete caused by different temperatures inside the block is shown in Fig. []. Solving the Heat of Hydration How to manage the development of hydration heat already at that time dealt with also in neighboring countries. Known these ways; cooling water distribution, adding ice semolina to the mixture of concrete, concrete cooling system stored pipes with flowing cold water. But the technological and economic reasons, these methods were proposed. Joined to another method has been successfully used abroad, adding to the power plant fly ash to the concrete. For this reason, from 99 to mix fly ash was added. Fly ash is to participate in the initial stage of hydration process and thus significantly reduces the temperature of concrete during early hydration. This intervention had only a positive influence on the development of hydration heat, but also a significant saving of cement, as compared to the construction of dams Slapy overall it was 6 thousand tons of cement, see Table., where is seen the ratio of cement and fly ash in concrete core of dam and packing parts of dam. ISBN:

3 Strength in compression Concrete Dosage 8 days 9 days Bore kg/m MPa MPa MPa Core + 9 part Packing part Table : The composition of the core concrete and packing concrete for construction of dams. Dosage is described: cement + fly-ash. Tests were performed in a hydraulic test machine. For this reason, it was possible to obtain a descending branch and the working diagram, as presented in the figures (Fig. 6 ). 6 Experimental Part of the Present The obtained solid cores were prepared for experiments. Given that the maximum aggregate size in concrete was cm, the need for a body to experiment with a diameter greater than cm (Fig. ). For reasons of size was used body height of approximately. cm [4]. Fig. 4: Bore obtained from dams. For experimental testing was available specimen of the height of cm. The compression areas of specimen were repaired with cement paste and the specimen of subsequently tested in compression []. Specimen, compression strength 4 Stress (MPa) -,6 -,4 -, - -,8 -,6 -,4 -, Strain (*.) Fig. : Compression test of one of specimens. Fig. : Specimen prepared for splitting test. 6 specimens were used for experiments, which were carved from the bores. Bores were obtained from the body of the dam during air-conditions tubes in concrete preparing. Size drill allowed takes an external barrel diameter cm. The total length of the canal was drilled m. Nevertheless, there are bores of approximately 6cm. The specimens were prepared for splitting the body test and the compression test. Splitting test was performed as a classical Brazilian test [6]. The cylindrical body was centric compressed by linear loading (Fig. ). The body was broken lateral tension.,,, Specimen No.,, Strain (*.) Fig. 6: Splitting test of specimen No. prepared ISBN:

4 Specimen No. Specimen No. S tre ss (M P a ),,, Strain (*.) Fig. 7: Splitting test of specimen No. prepared 4, 4,,, Strain (*.) Fig. : Splitting test of specimen No. prepared Stress (M Pa),,, Specimen No Strain (*.) Fig. 8: Splitting test of specimen No. prepared 4, 4,,, Specimen No Strain (*.) Fig. 9: Splitting test of specimen No. 4 prepared Stress (M Pa),,, Specimen No Strain (*.) Fig. : Splitting test of specimen No. 6 prepared Specimen No. Peak Load (kn) Strength (MPa) Table : Peak load and strength from splitting test. 7 Conclusion Due to the large number of surviving documents from the building construction is possible if the dam make backward analysis and gain valuable time dependence of material properties. ISBN:

5 Orlik dam is historically very valuable building, which at that time brought new ideas in the use of concrete. Today, concrete is the basic building material, which offers new possibilities for the use of fly ash. Experimentally was verified increase of compressive strength from MPa to the 4MPa. Change in compressive strength occurred over a period of 6 years. Although data on the transverse tensile strength of the historical sources are not available, it can be expected to that the development of the property is the same course as the compressive strength. Transverse tensile strength provides a clear confirmation of increase in compressive strength [4], [6]. In transversal tensile test has confirmed increase in value over time. The presented graphs show a gradual downward shape of the branch, which brings with it a great prediction of the energy stored in the concrete. The data obtained provide very valuable insight into the evolution of material properties over a long period of time. Acknowledgements This work was supported by project GACR under No. P4//8. References: [] Keil J., Construction of the dam Orlik - collection of essays, the national water company building, 966 (in Czech language). [] Hydroprojekt Prague: Waterworks Orlik elaborate summary - Volume / 4 - text, 96. [] Hydroprojekt Prague: Waterworks Orlik elaborate summary - Volume / 4 - part of the drawing, 96. [4] Neville, A.M., Properties of Concrete, John Wiley & Sons, (997), ISBN [] Zobal, O. Padevět, P.: Compressive strength and the tensile strength in bending after 8 days, Proceedings of the Conference Nano and Macro Mechanics, Prague, ISBN [6] Van Mier, J.G.M., Fracture Processes of Concrete CRC Press (997), ISBN ISBN: