During summer seasons of 1982 and 198S the authors collected observations on rate of soil thawing under and around shallow tundra lakes. Two lakes were studied: A on the terrace 10 m a.s.1. in northern Kafliöyra whereas B at about 40 m a.sJ. in southern margin of Sarsdyra. The lakes indicated considerable variation of water lavels (10—20 m) caused by limited water bodies (to 40—80%) at the end of the observation period. Soil thawing was studied in sections across lake basins and to 20 m around them. A thawing rate was found greater under the lakes than in their surroundings and it was noted to be in the same time the quicker the larger was the lake. Studies of the lake B proved also that increase in the reservoir depth made a greater rate and depth of summer thawing. This process varied also considerably in time. At the beginning of a polar summer the dry soil of elevated tundra thaws sooner while permafrost under water reservoirs gets conserved. Later on (in August) a quick aggradation of active layer in noted under the lake. A heat accumulated in water bodies prolongs the soil thawing as well.
The phase composition of the cement paste phase of concrete containing fly ash from circulating fluidized bed combustion (CFBC) was studied. The motivation was to broaden the knowledge concerning the microstructure and the durability of concrete containing new by-products from the power industry. Several air-entrained concrete mixes were designed with constant water to binder ratio and with substitution of a part of the cement by CFBC fly ash (20%, 30% or 40% by weight). X-ray diffraction tests and thermal analysis (DTG, DTA and TG) were performed on cement paste specimens taken from concrete either stored in water at 18° C or subjected to aggressive freeze-thaw cyclic action. The evaluation of the phase composition as a function of CFBC fly ash content revealed significant changes in portlandite content and only slight changes in the content of ettringite. The cyclic freeze-thaw exposure did not have any significant influence on the phase composition of concrete with and without the CFBC fly ash.
Mid-winter rapid rise of temperature in the vicinity of Arctowski Station, King George Island (West Antarctica) was studied in 1991. Depending on circumantarctic migration of cyclones, sudden drop in air pressure and foehn-like phenomenon intensified by local topography occurred. Two such events are described on May 13 and June 28, against meteorological conditions during autumn and winter. Extreme intensification of morphogenetic processes caused degradation of a snow cover, immense meltwater discharge, radical transformation of slopes, effective aeolian activity and dynamic modifications in a sea-shore zone.
The recycle of the building and demolition waste could reduce project expenses and save natural resources as well as solve problem about environmental risks incurred during the disposal of building waste. In this study, waste C30 concrete is taken an experimental material. The mass loss, ultrasonic velocity, dynamic modulus of elasticity and cubic compressive strength of recycled coarse aggregate concrete whose coarse aggregate replacement percentage is 25%, 50%, 75%, and 100% are tested and compared with NAC when the cycles of freezing and thawing are 0, 25, 50, 75, 100, 125, 150, 175, and 200 times. The results show: (1) Generally, the loss of mass, ultrasonic velocity, dynamic modulus of elasticity and cubic compressive strength constantly increase with the growth of freezing and thawing cycles. (2) Compared with the recycled concrete of other replacement percentages, the RAC50 shows relatively close performance to NAC in mass loss, the change of dynamic modulus of elasticity and cubic compressive strength. (3) Performances of RAC25 specimens are better than the other RAC specimens for the ultrasonic wave velocity.