Lignosulphonate is a widely used plasticizing admixture in concrete. It is well documented that different qualities of this material give different performance in concrete. Depending on what kind of concrete that is needed, workability can be controlled by adding different amounts or qualities of the lignosulphonate. This investigation compares the adsorption of lignosulphonate on three different portland cements, to the rheological properties of cement pastes made from the same cements. The adsorption isotherms were calculated from depletion experiments. A rheometer with bob-cup geometry was used to measure the rheological properties of the cement pastes. The plasticizing effect of lignosulphonates in cement paste slurries was confirmed. Recent advances have given a novel lignosulphonate with superplasticizer performance. This investigation demonstrates these improved properties achieved by this novel lignosulphonate by determining the differences in adsorption of the different lignosulphonates, on cements with different chemical characteristics.

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.

The working mechanism of a polycarboxylate superplasticizer (PC) which is a new generation of superplasticizer (NSP) is investigated. This NSP shows a shrinkage reducing effect as well as a water reducing effect with adequate slump retention in a wide range of water cement ratio by introducing a shrinkage-reducing component (SRC) into the molecular structure. Superplasticizers have been thought to be adsorbed on cement hydrates and to show their particle dispersing effects by modifying the inter-particle potentials. On the other hand, shrinkage reducing agents of the organic type have been thought to exist at the interface between the aqueous and the pore phases in hardened cement paste and to show their shrinkage reducing effects by reducing the surface tension, which occasionally results in the degradation of freezing and thawing (F/T) resistance. In this study, the mechanisms of NSP are discussed. By building a SRC into the molecular structure, the entrained air system is expected to be controlled successfully compared to traditional shrinkage-reducing agents (SRA) and so the degradation of F/T resistance can be avoided. With the progress of hydration, SRC is released from NSP and the surface tensions decreases, which results in the reduction of drying shrinkage.

Corrosion of stainless steel bars in concrete was investigated using sound and pre-cracked concrete specimens. Three types of stainless steel were investigated, such as 18Cr, 18Cr-8Ni and 18Cr-12Ni-2.5Mo. Concrete specimens were exposed to two environments, where wetting and drying alternately repeated. One was in the outdoor with atmospheric temperature, and the other was in a controlled chamber, where the temperature was 60°C during wetting and 15°C during drying. The detail investigation was carried out after two years. No corrosion was observed on stainless steel bar in both sound and pre-cracked concrete exposed to outdoor. The maximum chloride ion concentration was 7.0 kg/m3 for 18Cr-8Ni, 8.0 kg/m3 for 18Cr-12Ni-2.5Mo and 6.0 kg/m3 for 18Cr at the crack region of concrete. This result indicated that the chloride ion threshold level for stainless steel was larger than these values under marine environment with atmospheric temperature. No corrosion was observed on both 18Cr-12M-2.Wo and 18Cr in both sound and pre-cracked concrete exposed to controlled chamber. However, corrosion was observed only for 18Cr-8Ni at the crack region, even when the chloride ion concentration at the crack region was 6.0 kg/m3. This was considered to be due to the effect of a high temperature.

Self-Consolidating Concrete (SCC) is recognized by those in the industry as a mixture that can flow into place and completely fill formwork with little or no vibration. This concept immediately brings to mind an image of a highly fluid concrete mixture that flows like water. It is the level of fluidity that provides the self-consolidation and ease of placement characteristics that both precast concrete producers and concrete con-tractors are anticipating when they use SCC. The characteristic of fresh concrete stability, however, is also important although it may sometimes be overlooked. Stability is critical both during the placement operations (dynamic stability) as well as once placement is complete (static stability). Because the stability of the SCC mixture has significant impact on the final hardened properties of the concrete, it should be considered during the mixture development and quality control process. This paper outlines some of the variables that influence SCC static stability and provides insight on how to control them.