The potential of using the stainless steel coatings to protect steel reinforcing bars from corrosion especially in a salt contaminated concrete environment was evaluated. Type 304, 3 16 and 420 stainless steel coated coupons and reinforcing bars were prepared using the Twin-Wire Electric Arc (TWEA) and High Pressure/High Velocity Oxygen-Fuel (HP/HVOF) processes. Metallographic examinations were conducted to determine the coating density and the oxide content. The corrosion resistance of the coatings was evaluated using linear polarization and salt spray techniques. The stainless steel coating prepared using the HP/HVOF process had a much superior corrosion resistance performance than those prepared using the TWEA process. The former process produced a dense, low oxide content coating while the latter produced relatively porous coatings.The oxide content of the coating in the TWEA process can be significantly reduced using argon or nitrogen as primary and arc jet gases. This did not have a significant effect on porosity of the coating.

This paper describes changes of stress and strain during the setting of prismatic specimens incorporating polymer mortar. A new apparatus measures setting shrinkage stress and strains developed at both ends of polymer mortar specimens while at constant temperature. This apparatus is simple in structure, consisting of a noncontact type displacement device and a load measuring device. The relationships of setting shrinkage stresses and strains, and elastic modulus of three kinds of polymer mortar are reported. Furthermore, the mechanical properties of three kinds of polymer mortar were investigated. Finally, the deflection and strain that occur when polymer mortar is overlaid on ALC (Autoclaved light weight concrete) beams includes both analysis and experimental data on the two layered structure.

Generally, high-performance concretes can be defined as types of concretes that meet one or more performance requirements in a specific way. Usual concretes are concretes with a compressive strength up to 55 Mpa and fly ash contents of around 20 mass.% relative to the total binding components (c + f). In the production of high-strength concretes (compressive strength > 65 Mpa), silica fume has been used usually in order to achieve the expected strengths at low w/c. In the production of mass concretes blast-furnace slag cements with a high percentage of slag are preferred in order to reduce the heat of hydration released by the cement reaction. The objective of the investigations presented in this paper was to produce high-strength and mass concretes with fly ash and to characterize the performance of these concretes. For this purpose, concretes with fly ash contents of 10, 20 and 30 mass.% relative to (c + f) at w/c between 0.33 and 0.43 are investigated. The properties and the performance of these concretes are presented using the parameters compressive strength and their stress-strain behavior. Beyond this, the performance of mass concretes with high fly ash contents is presented by the example of laboratory experiments and field studies at two newly-built power plants in the East German federal states. Concretes with reduced portland cement contents and fly ash contents between 30 and 60 mass.% relative to (c + f) were used in laboratory tests. Fly ash contents of 53 and 42 mass.% relative to (c + f) were used to produce monolithic base slabs with a concrete volume between 17,000 and 22,000 m3 (production in one operation). The performance of these concretes is shown using the parameters compressive strength development, heat of hydration development and their Ca(OH)z-content.

SP-171 The Canada Centre for Mineral and Energy Technology (CANMET) of Natural Resources of Canada, Ottawa, has played a significant role in Canada over 35 years in the broad area of concrete. In August 1997, CANMET in association with the American Concrete Institute and other organizations in Canada and New Zealand, sponsored the Third CANMET/ACI International Symposium on Advances in Concrete Technology in Auckland, New Zealand. The main purpose of the symposium was to bring together representatives from industry, universities, and government agencies to present the latest information in the subject area of the symposium, and to explore new areas of needed research and development. More than 50 papers from 15 countries were received and reviewed in accordance with the policies of the American Concrete Institute. Thirty-three of the papers were accepted for presentation and publication. In addition to the refered papers more than 20 other papers were presented and distributed at the symposium.

The basalts of the central Auckland area, classified as nepheline basanites, exhibit a high potential for alkali release. When they are combined with Waikato River sand in concrete, an expansive reaction could occur with the alkali release. Methods developed at the New Zealand Institute for Industrial Research and Development (IRL) were applied to the few failed public structures at Auckland. These showed levels of contribution by the basalt of sodium and potassium in the pore solutions of the concrete exceeding 5kg Na20eq/m3. Bulk chemical and x-ray diffractometric phase analysis of the Auckland nepheline basanites reveal only minor variations. Feldspathoids (nepheline and in the case of Mt. Wellington basalt also leucite) are singled out as the main alkali-releasing phases. Their content can be estimated from the composition of a simple acid leach. This determines only the full alkali-release potential which is probably not frequently developed in Auckland concrete structures. Experimental mortars attain these high alkali-release levels if small aggregate grain size and high W/C are applied. At moderate W/C (eg 0.47) and curing time (eg one year) the rate of alkali release in concrete develops greater differences between and within quarries. These differences are controlled by the interstitial surface area and the phases that can be accessed by the pore solutions. Their alkali release decreases in the following order: feldspathoids (nepheline and leucite) > interstitial glass > feldspar (labradorite). Slow cooling of the lava, and incipient alteration have a delaying effect on alkali release. Screening tests that are faster than mortar curing and address these variables are: a ) analysis of alkaline leachates using 0.3 M LiOH and 0.3M tetramethylammoniumhydroxide (TMA-OH). b ) the measurement of internal surface area and micropore volume of the basalt by absorption-desorption porosimetry or sorption characteristics for heavy alkalies (Rb, Cs). C> electron microprobe investigation of alkali-bearing phases. Although none of these tests on its own provides all the desired information, the analysis of the alkaline leachates is likely to provide a practical measure for the eve1 of alkali that will be released.