This paper describes the properties of lightweight aggregate concrete consisting of high performance artificial lightweight aggregate. The concrete was developed in order to be used on a rigid frame prestressed concrete bridge with a length of 256m. The concrete had good pumpability, resistance to freezing and thawing action, and high strength. The maximum equivalent horizontal pumping distance of the concrete was more than 150m with no prewetting of the lightweight aggregate. The compressive strength of the concrete was about 6OMPa and the elastic modulus was more than 21GPa.

An equation was formulated for estimating the plastic viscosity of cement paste containing an air-entraining admixture, which is a commonly used chemical admixture for concrete. Air-entraining admixtures slightly increase the plastic viscosity of neat cement paste. The viscosity equation was derived by incorporating this effect, to minimize the difference between the estimation and measurement. The ratio of the plastic viscosity estimated from the proposed viscosity equation to the measured plastic viscosity was found to be approximately 1, the anticipated value. Viscosity equations for mortar and concrete also formulated based on an existing viscosity equation were found to be valid even when the plastic viscosity of the matrix changed.

A test apparatus called "dilatometer" has been developed to predict the dosage of lithium nitrate (LiNO3) required to control ASR expansion as a function of the alkali level and aggregate reactivity. The dilatometer is instrumented so as to monitor within a short period of time the volumetric expansion of the siliceous gel produced by a siliceous aggregate. The rationality of this test procedure was explored from comprehensive laboratory experiments related to the effects of temperature, normality of NaOH test solution, and LiNO3 dosage. Determination of the level of expansion within 30 hours, using this method enables one to predict the dosage of LiNO3, which is now being used as an ASR mitigating agent, needed for a particular aggregate to control expansion due to ASR. Based on the test results, it is anticipated that this test method will be useful for predicting the optimum dosage of LiNO3 required for a particular aggregate type and source.

A detailed investigation on the concrete specimens made with different chemical admixtures was carried out after 10 years of exposure in the marine splash environment. Chemical admixtures include air-entraining admixture (vinsol), water-reducing admixture (lingosulfonate group), various high-range water-reducing and air-entraining admixtures (naphthalene, melamine, polycarboxyl and amino-sulfonate group), and drying shrinkage reducing admixture (glycol ether plus amino alcohol derivatives). The specimens were tested for carbonation depths, chloride ingress, oxygen permeability, electrochemical and physical evaluations of corrosion of steel bars in concrete, porosity and mineralogy of the mortar portion, and SEM (Scanning Electron Microscopy) investigation of steel-concrete interface. Naphthalene group of high-range water-reducing and air-entraining chemical admixture shows relatively better performance with respect to the strength development and chloride ion ingress in concrete. The use of shrinkage reducing admixture shows no harmful effect after 10 years of exposure. The specially adopted method of casting concrete used in this study causes a formation of good steel-concrete interface that prevents the initiation of corrosion even for water soluble chloride concentration around 1.5% of cement mass.

This paper describes a part of a current European research programme (started March 2001) addressing superplasticizers of improved properties. The number of different cement types and blended cements is increasing. Incompatibilities of the cementitious compounds with admixtures can therefore not be excluded, especially at low water/cement ratios. Polycarboxylate superplasticizers with variations of side chain length, content of anionic groups and degree of polymerisation of the backbone were synthesised. The interaction of these polymers with different cements and cement blends was investigated by measuring adsorption, flow of cement pastes and mortar tests. Interesting performance differences can be seen between the different superplasticizer-cement combinations, especially at low water to cement ratios. The results of the paste flow can be explained with the polymer structure and the cement chemistry and can be used to predict polymer performance in mortar. The low alkali cement shows lower sensitivity to differences in structure of polycarboxylate superplasticizers than cements with higher alkali content. The adsorption of polycarboxylate polymers on cement is driven by the structural features of the polymer and can be directly related with the flow of the cement paste.