1、PDF外文：http:/ ： 英文原文 TEMPERATURE CONTROL OF THE MASSIVE CONCRETE OF THE KRASNOYARSK HYDROELECTRIC STATION DAM A. P. Dolrnatov and S. Z. Neidlin UDC 627.821.2 : 666.972.021.21.035.83 (282.251.2) During recent years a number of large hydroschemes with high massive concr
2、ete dams have been bnilt in areas of the USSRin an area of extreme climate. A number of problems arise in the erection of massive dams under severe climatic conditions related to the prevention of fissuring in the concrete and obtaining a monolithic structure. Typical features of the construction of
3、 large hydroschemes are the large volumes of concrete and the extremely limited time for pouring them, which means a high rate of concrete placing. Measures for controlling the temperature of the concrete on a large scale were adopted practically for the first time in the Soviet Union in the constru
4、ction of the Krasnoyarsk hydrocomplex. The severe climatic conditions at the site (mean annual temperature +0.4 , maximum long range temperature +37 and minimum, -54 ) introduced serious difficulties in obtaining monolithic mass structures and ptaced special demands on the concrete and its pla
5、cement. In order to obtain monolithic concrete structures,the "Technical regulations for carrying out concreting" lays down the following temperature conditions for blocks with columnar section (plan dimensions 15 x 11.5 m, height 3 to 9 m): a) maximum temperature in blocks placed on fresh
6、 concrete (less than 1 month old) must not exceed 40 ； b) maximum temperature in blocks placed on old concrete (more than i month old) and rock must not exceed 28 ； c) the temperature drop between the core and faces must not exceed 23 ； d) temperature of the concrete at the moment when the intercolu
7、mnar construction joints solidify (cementation) must not be more than 5 in the bottom 20 meters from the foundation and 8 in the remaining mass. A number of measures were envisaged for controlling the temperature of the dam concrete, namely: the use of cements with average thermal proper
8、ties (mineralogical composition of the clinker C3S = 47-48%； C3A = 6-6.5%； heat liberation of the slag Portland cement (40% slag) on the 28th day 73-75 kcal/kg)； zonal placing of the concrete； the use of heated formwork (from 15 September to 15 April) keeping the blocks stripped in winter only under
9、 heated covers and using three types of formwork depending on the concreting season, with coefficients of heat transfer K = 0.8, 1.5 and 3.0 kcal/m2 h degree； prior cooling of the concrete； and cooling by cold water circulating through coils laid in the concrete. Fissuring was markedly reduced by th
10、ese measures. While in 1961 there were three cracks per 1000 m3 a concrete, 1.24 in 1962, 1.12 in 1963, and 0.42 in 1964,there were only 0.16 in 1965. The number of cracks rose sLightly in 1967 on account of a smaller proportion of cooled concrete and the higher grading of the concrete on the top se
11、ctions of the structure. Table 1 sets out the main cooling characteristics of the concrete to temperatures at which cementation of the joints could be undertaken. Piped cooling for reducing the peak of the exothermic temperature rise of the concrete was brought into use during the summer of 1963 and
12、 employed generally from 1964. During this period there was a sharp drop in the fissuring rate in the concrete. During 1961 to 1963 the concrete in the spillway apron and the crest of the first stage was not cooled and at the same time the temperature rise of the concrete masonry was limited by redu
13、cing the height of the blocks near the rock to 0.7-1 m and by the small growth of the structures in height. Concrete placing in the second-stage excavation and in the first-stage excavation was carried out above the crest using piped cooling. The numerator shows the amount of concrete placed o
14、r cooled during the year； the denominator shows the volume and increase in the amount. 200,000 m S of this concrete was cooled using water cooled in a refrigeration plant. Concrete placing in the top section of the dam, which is intended for completion by 1969-1970, will be carried out withou
15、t artificial cooling. Cooling of the concrete during the construction of the Krasnoyarsk hydroelectric station was carried out in two stages. In the first stage cooling was used for reducing the exothermic peak of the freshly placed concrete and in the second stage for further cooling of the mass do
16、wn to the temperature where it is made monolithic. First stage cooling was carried out usually in the summer only but from 1965, with the introduction of high blocks, it was carried out in winter. From 1966 the first stage cooling was carried out continuously for the purpose of improving the concret
17、e stress in the immediate vicinity of the cooling pipes, accelerating cooling of the block, for rendering the joints between columns monolithic and improving reliable performance of the cooling coils (leaching). The second stage usually starts at the end of August with a water temperature of 15-18 . During this period the concrete is cooled mainly from a temperature above 25-30 , for the purpose of further reducing the temperature towards the winter season and in preparation for cooLing in winter with water at a temperature of 0.5-1 .
