During the last decades new cementitious materials were available. These represent a technical revolution with respect to the traditional concretes. The most important innovative "High Tech" materials are Self-Compacting Concretes (SCCs). In the present paper the compositions, the performances and some practical applications of high-performance SCCs are shown. In particular, some performance improvements carried out in our laboratories are shown for these specific uses: a) SCC for a Building Engineering application (S. Peter Apostle Church in Pescara, Italy) with white concrete characterized by a marble-like skin; b) SCC in the form of high-strength concrete with compressive strength over 90 MPa devoted to a work in the field of Civil Engineering (World Trade Cen ter in San Marino); c) SCC in the form of mass concrete structure with a reduced risk of cracking in duced by thermal difference between the nucleus and the skin of the elements; d) SCC in the form of lightweight precast concrete with a density of 1750 kg/m3, 28-day compressive strength of 35 MPa, and 28-day flexural strength of 5 MPa; e) SCC in the form of a shrinkage-compensating concrete for reinforced concrete walls 8 m high and 55 m long.

A long-term research study on anti-corrosion products for reinforced concrete exposed to aggressive environmental conditions was initiated in 1990. The performance of products was evaluated through accelerated laboratory testing and natural site expo-sure conditions as tidal zone, above ground and below ground. An exposure site on the Dubai creek shore is designated for long term performance testing at different ages ex-tending up to ten years. A series of physical and electrochemical testing were performed in three phases. The prime objective of the first phase was to assess the performance of the various products, and to assess the practical value of different electrochemical test methods. The focus of the second phase testing shifted towards a more comprehensive evaluation of the test methods. The interim results have been presented at different international conferences. The focus of third phase, which was performed in early 2000, was to observe the actual extent of corrosion sustained by the rebar. This paper presents the final data to substantiate conclusions relating to ingress of chlorides for the various exposure conditions (threshold values), provides recommendations for corrosion monitoring for new structures and test methods for evaluating products and future research requirements.

Magnetic Resonance Imaging (MRI) is a nondestructive technique that can be used to spatially resolve distributions of certain nuclei. Lithium is a relatively sensitive nucleus for MRI. Therefore, it is possible to directly measure the distribution of lithium in cement based materials. Lithium salts are used in concrete to suppress alkali-silica reaction. The MRI relaxation parameters associated with lithium in cement-based materials are relatively short by traditional MRI standards. Due to the short relaxation parameters, special MRI measurement techniques and hardware considerations had to be developed in order to quantify lithium distributions in cement based materials. MRI has the potential to play an important role in concrete technology. While this method has been developed for laboratory studies, measurements could be made on cores extracted from existing concrete structures.

Delayed ettringite formation (DEF) occurs at late ages and the related heterogeneous expansion in a hardened concrete can produce cracking and spalling. There are two different types of DEF depending on the sulphate source: DEF caused by external sulphate attack (ESA) or internal sulphate attack (ISA). In the present paper only ISA-related DEF is studied with reference to the following three parameters: a) the sulfate content in the clinker phase of the cement; b) the curing temperature; c) the presence of preliminary cracks in concrete specimens. Concretes manufactured at room temperature (20°C) do not show any form of DEF-related expansion independently of the SO3 content of the clinker (1—2%) or the portland cement (2-4%). On the other hand, concretes steam-cured at 90°C and then kept under water show significant expansion related to DEF provided that the SO3 con-tent of the portland cement is relatively high (> 4%). The higher SO3 content in the clinker phases (> 2%) or the presence of preexisting cracks accelerates the DEF-related expansion. Deposition of ettringite fiber crystals occurs in the preexisting cracks or within the new microcracks. Curing at temperatures lower than 80°C, preferably lower than 70°C, is strongly recommended to avoid DEF-related risk. Blended cements with a lower SO3 content should be used in case this limit in curing temperature cannot be safely ensured.

This paper presents the introduction of a steel fiber made by a pre-cast manufacturer suitable for plant-produced products and transit-supplied concrete. The fiber con-figuration allows fiber manufacturing to be done in-house as are the other concrete products. Toughness test results indicate equivalent or improved performance with lab mixtures compared with other steel fibers available and tested. Tests were conducted with both wet (laboratory and transit mixture) and dry cast techniques for testing samples and full-scale three-edge bearing tests for dry cast pipe. Performance issues were identifiable for the sample casting techniques, compression strength, maturity, and toughness tests with fiber reinforcement. Pipe tests were conducted for the first visible crack, the first 0.25 mm crack, and the ultimate load with fabric reinforcement only, fiber reinforcement only, and then with both fabric and fiber reinforcements. Concrete mixture proportions for the pipe were constant with three dosages of fiber used: 0.25, 0.50, and 0.75 percent by volume.