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Conflicting information on the freeze-thaw resistance of superplasticized concrete is given in the literature. For this reason, the Research Centre of the German Cement Industry instigated an extensive research program. Superplasticizers based on melamine and naphthalene sulfonates were used in the main program and lignosulfate-based products in a subsidiary program. Some of these contained de-airing agents. The air-void distribution and the spacing factor were measured as well as the freeze-thaw resistance with deicing chemicals. When superplasticizers were used in a high-workability air-entrained concrete, the number of pores with a diameter up to 300 æm decreased, while the content of pores larger than 500 æm and the bubble spacing factor increased. Small pores coalesced and formed larger pores. Although the air content of the fresh concrete was sufficient, the superplasticized concrete sometimes had a spacing factor above 0.20 mm. For this reason, concrete with superplasticizers did not always have adequate freeze-thaw resistance. An influence due to the type of superplasticizer could not be detected, while the de-airing agents of the superplasticizers had a considerable effect. Some additional tests with plasticizers and retarders show that these admixtures also alter the air-void distribution or air-entrained concrete.

The basic principle of preventing the deterioration of reinforced concrete structures is to inhibit the wet corrosion of reinforcing bars. According to the principle, the effective inhibition of the penetration of carbon dioxide, oxygen, water, and chloride ions is required to make highly durable concrete. Mortars are prepared with various contents of chemical admixtures and cement modifiers to meet such requirements, and tested for strength, water absorption, chloride ion penetration, and carbonation. From the test results of the mortars, effective admixtures are selected for concrete mixes. The strength, chloride ion penetration, carbonation, and drying shrinkage of concretes containing the selected admixtures are examined. In conclusion, the simultaneous addition of polymer dispersions and alkyl alkoxy silane at a polymer-cement ratio of 0.5 percent is recommended for the highly durable concrete.

Atomic Energy of Canada Limited is undertaking a research and development program on cement-based grouts for possible use in sealing an underground nuclear fuel waste disposal vault. Silica fume and superplasticizer were added to a finely reground sulfate-resistant portland cement to produce a durable, low-permeability grout that would penetrate very fine fissures in granitic bedrock. The superplasticizer additive permits very low water-cement ratio grouts (w/c less than 0.6 by mass) that exhibit no segregation or bleed. The silica fume additive contributes to improved chemical stability and leach resistance of the grout. The developed grout has been injected into granitic rock at AECL's Underground Research Laboratory in Canada and at the NEA/OECD Stripa Facility in Sweden. No problems were encountered in the field trials in mixing, handling, or pumping of the grout. The injected grout produced only a very limited geochemical signature in the ground water and appears capable of penetrating microfissures in the granite with apertures of less than 20 æm.

The construction procedure of a nuclear containment concrete structure recently built required a highly workable concrete to facilitate placing around heavily congested steel embedments and reinforcements. Use of a superplasticizing admixture was considered essential. A test program was undertaken with several commercially available admixtures to study the properties of the fresh and hardened concrete made with low-heat cement (CSA: A5 Type 40). Under controlled conditions, four of these products met the construction requirements without adversely affecting the properties of the concrete.

Laboratory studies have been carried out to determine the leachability of the adsorbed superplasticizer (an Na-sulfonated naphthalene formaldehyde condensate) and its location within the structure of hardened cement tastes. The superplasticizer, labelled with 35 S, was incorporated in a reference cement-based grout (90 percent Type 50, 10 percent silica fume, 0.4 ó w/c ó 0.6). Static leaching tests were used to determine the release of labelled superplasticizer to solutions as a function of temperature, groundwater composition, and grout surface area to groundwater volume ratio. The quantity of 35 S in the leachate was determined using liquid scintillation counting. Electron-microautoradiography combined with scanning electron microscopy and energy dispersive x-ray spectroscopy were used to identify the cement phases containing the labelled superplasticizer. The results show that superplasticizer can be leached from grouts, but the cumulatively released quantities are very small (approximately 10(12 kg/mý). Most of the released superplasticizer appears to come from the capillary pore space of the hardened grout; however, some release may result from dissolution of the cement phases. Increasing temperature and/or grout surface area to groundwater volume ratio increases the release rate of superplasticizer. Analyses, using electron-microautoradiography and scanning electron microscopy, indicate that the majority of the adsorbed super plasticizer resides on the C-A-H phases and the calcium-rich phases of C-S-H in the cement.