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Mortars with and without fly ash are cured initially in distilled water or NaCl solution for 7, 28, 56, and 91 days and then exposed to the accelerated carbonation. The influence of chloride ion on the depth of carbonation is evaluated. Furthermore, mortars initially cured in distilled water are exposed to the accelerated carbonation condition and then immersed in NaCl solution to study the influence of carbonation on penetration of chloride ion. In both cases, electrochemical properties of steel reinforcement embedded in the specimen are measured. The penetration depth of chloride ion in fly ash mortar immersed in NaCl solution is larger at an early age, but becomes almost the same as that of the control mortar later. The depth of carbonation of mortar cured initially in NaCl solution is smaller than that in distilled water, and the same trend is observed, independent of initial curing period and the addition of fly ash. Fly ash mortar shows higher carbonation depth than the control mortar. Corrosion current of steel reinforcement in mortar is affected by both carbonation depth and chloride ion penetration.

The lining of underground cavities for storage of natural gas requires a proper cementing paste as does the cementing of casing in boreholes placed in salt beds. The following properties of the cementing pastes are required: high corrosion resistance, minimal shrinkage, even some expansion, high leak tightness, good bond to steel and rock, proper rheology and strength. The following blended cements were investigated: cement "Nowa Huta" 25 with 40% blast-furnace slag (bfs), cement "Rejowiec" 45 for bridge construction and cement with 70% bfs. The cements were mixed with NaCl brine at a concentration 310 g NaCl/L at liquid to solid ration 0.45. The properties of pastes, such as density, rheological, sedimentation and filtration characteristics; time of setting; strength development and shrinkage were determined. The phase composition of pastes was studied by XRD and the microstructure was observed under SEM. The best results were obtained for the pastes with the blast-furnace slag.

The resistance to freezing-and-thawing and chloride diffusion of antiwashout underwater concrete was investigated to evaluate the applicability for tidal zone in cold districts or reinforced concrete structures in marine environments. Comparisons were made with ordinary portland cement concrete of similar mix design. Two types of cement (ordinary portland cement and portland blast furnace slag cement) were used. Two types of blast furnace slag (Blaine fineness 500 and 700 m²/kg) were used as a cement replacement (slag content 30 and 50 percent by weight). The results show that antiwashout underwater concrete without blast furnace slag shows poor resistance to freezing-and-thawing compared with normal concrete. But the freezing-and-thawing resistance can be improved with blast furnace slag. This is due to the fact that concrete containing blast furnace slag has dense pore structures. Pore volume in the range of 10 to 10 3 nm in radius decreases significantly with blast furnace slag. Similarly, chloride diffusion depth becomes smaller with blast furnace slag.

The effectiveness of one ground granulated blast furnace slag, two condensed silica fumes (high-silica/low-alkali, low-silica/high alkali), and three pulverized fly ashes (low-alkali/low-calcium, low-alkali/moderate calcium, high-alkali/high-calcium) have been evaluated in the presence of two very alkali-silica reactive aggregates from Canada, a siliceous limestone and a rhyolitic tuff. Mortar bars and concrete specimens were made with various admixture contents and different cements (high- and low-alkali), and tested for expansion with the accelerated mortar bar method (ASTM C 9-P214) and the concrete prism method (CAN/CSA-A23.2-14A). The mineral admixtures were also submitted to the pyrex mortar bar method (ASTM C 441). Based on the results, the ASTM C 441 test is not recommended for assessing the effectiveness of mineral admixtures in suppressing expansion due to alkali-aggregate reaction, unless account is taken of a number of modifications concerning mix design (admixture content, water/cement ratio, alkali content, etc.) and performance criteria. Pyrex does not behave like a natural aggregate. The results from ASTM C 9-P214, using a limit of 0.1 percent expansion at 14 days, are in agreement with those from the concrete prism method, which is the most recommended test procedure. However, when testing concrete, the alkali content of the mix must always be increased to 1.25 percent of the mass of cement (Na?2O equivalent), otherwise the test is not accelerated sufficiently and low expansion will be observed in the presence of reactive aggregates, even with no mineral admixtures. The long-term effectiveness of mineral admixtures against alkali-aggregate reactions (AAR), in particular silica fume, is presently questioned by a number of workers. Therefore, it is firmly recommended that conservative limits be used when conducting laboratory tests on concrete specimens, and that the tests be extended to at least two years. The mineral admixture under study should be used in amounts such that expansion never exceeds 0.04 percent in the long term (two years or more). A more conservative, and more recommended, performance criterion is to obtain expansion in the long term that is similar to that of a control made with a low-alkali cement and containing no mineral admixture

In tunnels built according to the New Austrian Tunnelling Method, the shotcrete shell is often in contact with ground water. Depending on the amount and type of water, chemical compounds in the shotcrete are dissolved and transported into the drainage pipes and the main outfall. Due to precipitation of the dissolved compounds, the maintenance of the drainage systems is very expensive. Furthermore, the main outfall is loaded with water of a high pH-value. It was found that as well as Ca(OH)2, the alkalies in the shotcrete are responsible for the degree of leaching. Therefore, the accelerators needed for such shotcretes, which are based mostly on alkalies, have to be reduced as much as possible. This can be done sufficiently if silica fume is used in connection with slag cement to make the shotcrete sticky enough, so that it adheres to the rocks.