Methods of heating the concrete for grouting the joints of the dam at the Zeya hydroelectric station

Conclusions

• 1. The electrical heating system of a joint with embedded electrodes, being technologically efficient in assembly and reliable in heating the zone of the joint being grouted, proved to be unconditionally preferable to the system of heating by tubular electric heaters through boreholes. All tests of systems of embedded electrodes were favorable and all sections were grouted successfully.

• 2. The experience of heating concrete by steam through a coil specially installed in a section showed the effectiveness of this method (with simpler installation of its components in comparison with the electrical heating system). It is necessary to continue work on the use of this method. Steam heating of concrete through boreholes is ineffective and requires large labor expenditures.

• 3. The method of heating concrete by injection of hot calcium chloride brine can be used only if the grouting system and joint are open and the section airtight. It should be carried out as an auxiliary measure during hydraulic testing and grouting after heating the concrete by either of the two other methods named above.

• 4. It is not advisable to use a system of regrouting with valve-type outlets if the concrete is frozen: First, grouting of frozen concrete is carried out at the maximum openings of the joint, which precludes additional opening during the operational period; second, the multiple-acting valves themselves can become clogged with salt during passage of hot brine through them.