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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.

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.

A research program was conducted in which the temperature rise of mortars and the durability of concrete containing fly ash were studied. The study of the effect of fly ash on the temperature rise of mortars included the use of both ASTM C 618 Class C and Class F fly ashes. Control tests were conducted on mortars containing ASTM C 150 Type I, Type I-II, and Type III cements, and comparison tests were conducted on mortars containing 20, 27.5, and 35 percent fly ash by volume of cement. It was found that the use of Class F fly ash resulted in a reduction in the temperature of the mortar, whereas the partial replacement of cement with Class C fly ash did not lower the mortar temperature, regardless of the type of cement used. Resistance to scaling in the presence of deicing salts and abrasion resistance tests were conducted on concrete samples cast from 21 batches of concrete. Variables studied included fly ash type, fly ash content, and curing conditions. Both ASTM Class F and Class C fly ashes were used to replace 25 or 35 percent of the cement by volume, and curing conditions included combinations of 50, 75, and 100 F with 50 and 100 percent relative humidities.

The resistance to deicer scaling of lean concretes containing fly ash was evaluated using ASTM C 672-84. Concretes were prepared at cement contents of 250, 305, and 335 kg/m3. Six fly ashes were chosen for evaluation at cement replacement levels of 25 and 50 percent by mass in each of the mixtures. Specimens representative of residential flatwork were prepared and cured for 1 and 7 days under moist conditions, then air-dried until initiation of testing at 35 days of age. Results indicate that all mixtures containing fly ash exhibit more rapid and severe scaling than those mixtures prepared with cement alone at the same total cementitious material content. Scaling was found to increase with a decrease in the total cementitious content of the mixture and an increase in the amount of cement replaced. Data on compressive strength, and characteristics of air-void systems in these concretes are also presented.

A study was conducted to determine whether pulverized fuel ash, granulated blast furnace slag, and natural pozzolana contribute effective alkalies and whether such alkalies lead to alkali-silica reaction (ASR) damage. Mortar bars were prepared in accordance with ASTM C 227 but stored at 20 C, and using three factory-produced cements, three Type F pulverized fuel ashes, three blast furnace slags, and four natural pozzolans at three or four different levels of substitution. The reactive aggregate component was Beltane opal substituted at the pessimum level, as well as zero and three near-pessimum levels. The selection of the materials and their substitution levels were adjudged to represent as wide as possible present-day usage. Deleterious expansion defined as > 0.0 percent within 4 years was taken as the criterion of failure. The results have been applied to demonstrate the deduction of practical guidelines for the use of composite hydraulic binders in situations in which ASR is a consideration. Limiting total alkali contents of composite hydraulic binders as function of the substitution ratio of the three mineral additives are suggested. The analysis of the results demonstrates that if the effective alkalies derived from portland cement are taken as 100 percent, then those derived from pulverized fuel ash and natural pozzolana can be taken as 17 percent and those derived from blast furnace slag as 50 percent of total alkalies. There is also evidence of somem mineral additives, particularly at high substitution levels, not simply acting as dilutents but exhibiting a positive ASR-suppressive effect.