the construction site of the Inguri hydroelectric project and was devoted to the topic "Acceleration of methods of quality control of hydrotechnical concrete." The conference was attended by more than 70 representatives of 37 planning, research, and construction organizations and of institutes of higher learning of the country, 25 reports were presented. The opening address of Doctor of Technical Sciences Prof. V. V. Stol'nikov was devoted to a review of current accelerated methods of concrete quality control and to the task of the conference.The increased level of demands placed on the concrete of dams and the diversity of concrete characteristics which require daily control were pointed out. Many standard characteristics (maximum tension, impermeability, shrinkage, swelling) have been introduced for the first time into the new State Standard GOST 4795-67. The most important requirements imposed on newly proposed accelerated methods of control should be: a) simplicity and flexibility of the methods of accelerated determinations; b) possibility of statistical analysis of the results; c) reliability of the determinations themselves and reproducibility of the obtained results.

Knowledge of the real properties of concrete in a structure and their changes during service permits solving many important problems related with the design of reliable, durable, and economical dams of different types. Such problems include an estimate of the correspondence between actual properties of concrete in a structure and the properties accepted when designing and the degree of reliability of determining strength and other qualities of concrete in dams by different methods.This problem has been studied in the International Committee on Concrete for Large Dams and a number of participating countries (France, USA, Great Britain, Japan, Norway, Australia, Czechoslovakia, and Sweden) have presented their opinions on this matter. The International Committee of Concrete has made a report on these data (September, 1967) and presented it to the 9th Congress on Large Dams. The main features of the report and conclusions are given below.In order to determine the behavior, life, and reliability of a dam after a certain service period it is necessary to know not only the concrete strength but also a large complex of other properties and their changes in time and under the effect of external factors. Therefore, reliable and well-founded methods of estimating the properties of concrete in structures are needed. A comparison of the views held in various countries concerning the value of methods and their areas of application permit making certain general conclusions with regard to the problem in question.Inspection and Testing of Outside Surface of Concrete Structures. The condition of a structure and the concrete properties are estimated first of all by a careful visual inspection of the dam and by determination of the strength of its outside surfaces. Such an inspection reveals the directions of a more detailed study and should be accompanied by a study of the documents on the composition of cement and concrete, and of observations during concreting, and also by tests of control samples.Instruments designed to determine the impact strength of a concrete surface are often used in practice for testing outside surfaces. Experience in Russia and abroad has shown that this method is useful mainly for detecting poor concrete situated near the surface and therefore is regarded as a supplement to other methods. It can be used also for a comparative estimate of the behavior of surface layers of concrete in parts of structures subject to alternate freezing and thawing, and is an auxiliary means of determining the degree of frost action on concrete.Coring and Sawing of Large Concrete Specimens. Large sections of concrete are cut out by drilling or other methods, which are then machined to impart the proper shape and tested for compressive strength. In Japanese practice this method is considered most reliable.

The IX International Congress on Large Dams took place in Istanbul, Turkey, September 4-9, 196q. The Congress was opened by the Prime Minister of Turkey, Suleiman Demirel, and the Minister of Power, Refet Sezhgin. The USSR delegation which took part in the work of the Congress consisted of M. Zh. Akhmetov, P. N. Gorienko, O. P. Zhebenev, N. M. Miloslavsk, S. M. Slissk, L. A. Tolkachev, V. B. Heifetz, L. I. Shrneleva, and V. V. Stop nikov (chairman).Two hundred nine reports were presented to the Congress from various countries on four principal questions. All of the questions were discussed at the plenary sessions. A general reporter and five experts selected from various countries spoke in advance, after which open discussion was conducted under the guidance of the chairman selected for that particular question. Each general report summarized the present status of the question and reflected the principal positions expressed in the reports of the various countries. A short resum6 on all four questions is presented below.Question 32. "The safety of dams from the point of view of the foundations and the stability of reservoir banks," was covered throughly in the papers. The session was conducted with the participation of general reporter A. Bourgin (France), session chairman S. Brown (USA), and experts L. Muller (Austria), D. Finzi (Italy), M. Rocha (Portugal), T. Nillson (Sweden), and F. Nickell (USA).

In his opening speech, V. V. StoI'nikov, Doctor of Technical Sciences, chairman of the coordination commission for hydraulic concrete, stated that the construction of hydraulic plants in the northeastern, northern, and eastern parts of the country brings along several new requirements the concrete has to meet. These requirements have been laid down in the new State Standard 4795-68, which was worked out by the B. E. Vedeneev AII-Union Scientific-Research Institute of Hydraulic Engineering. Many new requirements, such as ultimate strength, capacity to absorb water, shrinkage and swelling, etc., have been introduced. Great care is paid to the frost resistance of the concrete, especially at temperatures below --20~ V. V. Stol'nikov pointed to the chief shortcomings in the practice of setting up specifications for materials for hydraulic concrete; the conditions which the concrete has to stand are not examined with due consideration, and it occurs often that only the general directives of standard specifications are used, whereas the particular circumstances under which the structures must exist are not taken into account, nor are the structural peculiarities of the buildings and their construction methods. What is needed is a more comprehensive and creative approach to the design of the composition of the concrete and to its purpose in accordance with the environmental conditions of the concrete used in structures.Fillers for hydraulic concrete must also be considered with great care, and one may not confine oneself to a former approach that had been used in the construction of gravity structures. Today, fiIlers sometimes do not have the required high quality, though the requirements the concrete has to meet have been raised considerably since the power industry has turned to building thin arched dams and dams in seismic regions of the country. V 9 V. StoI'nikov emphasized the importance of testing the materials at construction sites by piling up and testing experimental blocks of sufficient size on an artiUery shooting range.Three main problems were put at the discussion of the conference:1. Experience gathered with concrete materials in the construction of hydraulic structures.2. Experience gathered in drawing up specifications for materials for various types of concrete for hydraulic structures.3. Investigation of and tests with hydraulic concrete and materials for preparing such concrete.

The problem of estimating the behavior of dams of various types after a certain interval of their operation attracts continously the attention of designers and constructors all over the world. At the Ninth International Congress on Large Dams*, 53 papers from 26 countries were presented on this problem (No. 34), which was the subject of a detailed discussion. The papers examined concrete as well as earthfill and rockfill darns. The most compreheusive was the analysis of problems of concrete deterioration. From the USSR a paper was presented by S. Ya. Eidelman (VNIIG) devoted to the results of instrumental observations at the Bratsk Hydroelectric plant,"The 50th Anniversary of the Great October." The problem was examined at the Congress under various aspects, most important of which were the design of dams, the observation of dams during the period of operation, repair and reconstruction, and the general problems of organizing and systematically controlling the behavior of dams of various types.As noted in a series of papers and emphasized by the general reporter D. Bullet (U.S.A.), the causes of deterioration and premature wear of dams are generated by insufficient investigation and poor study of the construction region, and also by design deficiencies, and particuiarly, by the incorrect selection of the dam type, and by the lack of adjustment of the dam to the actual conditions in which the construction works. Thus, according to the Czechoslovak National Committee, during the last 15 years several failures involving dams of heights between 5 and 21 m occurred because of the poor study and insufficient bearing capacity of the foundations. A failure involving a flood protection dike of 5.1 m height on the Danube occurred for the same reason.The comprehensive consideration of the climatic and operation factors which produce deterioration of the concrete in the operation process is very important. The modern state of the science of concrete and the level of knowledge of its properties make it possible to ensure a long and safe life service of hydraulic structures. However, 11 papers reported the destruction of concrete by frost because of interaction between the cement alkali and the aggregate, incorrect selection and specification of concrete requirements, and poor quality of concrete preparation and compaction during execution of the work. The papers emphasized that these destructive processes can be reduced to a minimum by the correct selection of the cement, aggregate, and additives, the ratio between the component parts of the concrete mix, careful casting, compaction, and curing of the concrete. The papers stressed especially the requirements of using aggregates of high quality and air entraining agents, and also of thermal protection of the concrete in the earlier stages to eliminate possible damage during the construction period.