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The chemical resistance of alkali-activated slag pastes and mortars in chloride solutions was studied. The four basic slag-alkali binding materials were prepared using granulated blast furnace slag, copper slag, and a mix of both these components. NaOH and Na?2CO?3 were used as activators. Some pastes and mortars containing 10 percent active silica additive were also made. The mortars were cured in standard conditions as well as subjected to low-pressure steam curing. The chemical resistance of alkali-activated slag mortars was compared with the chemical resistance of OPC mortars. The water-to-solid ratio was kept constant at 0.40. The samples cured in water were considered as reference samples. It has been found that the alkali-activated slag binders are chemical resistant in chloride solutions. These results were found not only from chemical resistance in chloride solutions and compressive and flexural strength tests, but also from the SEM observations of microstructure. The difference between the chemical resistance of slag and OPC mortars is probably the consequence of phase composition and porosity of the hydration products

Data on setting time, strength, modulus of elasticity, drying shrinkage, and compressive creep of concrete containing a low-calcium fly ash under hot and humid (28 ñ 2 C, 75 ñ 15 percent, relative humidity) climate are reported. Tests were carried out for Grade 25 and 35 concretes. The cement replacements with fly ash were 0, 20, and 40 percent, by weight. Between 3 and 90 days under moist curing (28 ñ 1 C), fly ash concrete gives rise to strength increases of about 110 and 230 percent with the fly ash contents of 20 and 40 percent, respectively, compared to an increase of about 65 percent for the control concrete. The relationship between the modulus of elasticity and compressive strength was not influenced by the partial replacement of cement by fly ash. Both grades of concrete with 40 percent fly ash content and moist cured initially for 7 days showed about 35 percent more drying shrinkage after 90 days of drying than the corresponding shrinkage for the control concrete. However, the shrinkage was found to be about 7 percent lower than that for the control concrete when the initial moist curing period was increased from 7 to 28 days. For Grade 35 concrete, the creep coefficient of concrete with fly ash content of 40 percent was 11 percent lower than that of the control concrete. However, Grade 25 concrete showed a 4 percent higher creep coefficient for fly ash concrete with the same 40 percent fly ash content.

Studies were done on the physical, mechanical, and geochemical properties of candidate cementitious materials for sealing a geologic nuclear waste repository in a tuff host rock environment. One sanded cementitious grout contains substantial replacement of cement by low-calcium fly ash and silica fume, yet maintains a water-cementitious solid ratio of 0.32 for a fluid grout. The ash and fume were used to achieve a higher SiO2 and Al2O3 content more compatible with the tuff geochemistry than a plain portland cement. One possible application for such materials is fracture sealing near waste canister emplacement holes. The effects of temperatures from 15 to 300 C on the material properties were investigated. Initial compressive strengths of materials cured at 38 C for 7 to 900 days ranged from 100 to 125 MPa. Other properties investigated include bond strength (to tuff), water permeability, interfacial permeability, Young's modulus, density, porosity, expansive stress, and phase changes. Samples heated to 150 C for extended periods (28 days), either dry or hydrothermally, maintained their strength and well-bonded microstructure, while the results of heating at 300 C were mixed, with some strengths remaining high (95 to 110 MPa) and others diminishing (44 to 51 MPa). The water permeability did not increase much at 150 C but did increase at 300 C.

Approximately 400 x 106 of low-level radioactive alkaline salt solution will be treated at the Savannah River Plant (SRP) Defense Waste Processing Facility (DWPF) prior to disposal in concrete vaults at SRP. Treatment involves the removal of Ca+ and Sr+2 followed by solidification and stabilization of potential contaminants in saltstone--a hydrated ceramic wasteform. The release of chromium, technetium, and nitrate from saltstone can be reduced significantly by substituting hydraulic blast furnace slag for portland cement in the formulation designs. Slag-based mixes are also compatible with Class F fly ash used in saltstone as a functional extender to control heat of hydration and reduce permeability. A monolithic wasteform is produced by hydration of the slag and fly ash. Soluble ion release (NO-3) is controlled by the saltstone microstructure. Chromium and technetium are less leachable from slab mixes than cement-based wasteforms because these species are chemically reduced to a lower faience state by ferrous iron or other ions such as Mn in the slag and are precipitated as relatively insoluble phases, such as Cr(OH)3 and TcO2.

Studies on the carbonation of concrete with fly ash and corrosion of reinforcements have been going on since 1962 at 16 research organizations in Japan. As already reported for intermediate ages, it has been shown that the depth of carbonation can be evaluated by compressive strength at the age of 28 days, which is very common value for specifying the concrete quality regardless of whether or not fly ash has been added. A number of findings have been made concerning the influence of exposure conditions on the depth of carbonation. This paper compiles the final test results at 20-year age, to augment the results previously reported for the intermediate ages. These studies also provide much verification data with respect to the durability of fly ash concrete. These test results are reflected on the Japanese standard specification for concrete cover.