Previous workers have shown that the air-void system in air-entrained concrete containing a superplasticizer tends toward larger bubbles. This effect leads to spacing factors larger than the 0.2 mm normally accepted as a requirement for durability. Nevertheless, concretes containing such admixtures generally have been found to be frost-resistant. The present work is an attempt to understand the reasons for durability when the accepted 0.2 mm spacing factor requirement is not met. The distribution of air-void sizes in air-en-trained concretes made with and without a naphthalene sulfonate type superplasticizer were examined, using a new microprocessor-based Rosiwal linear traverse apparatus. The individual chord intercepts available with this system were fitted to a zeroth-order logarithmic distribution function, and the parameters of the fitted function were related to frost resistance as tested for by ASTM: C 666, procedure A. Concretes containing the superplasticizer were frost-resistant, despite spacing factors in excess of 0.2 mm. The most frequently encountered chord lengths in superplasticizer-con-taining concrete did not change relative to equal slump refer-ence concrete.

More than twenty naphthalene sulphonated formaldehyde condensates have been synthesized with various degrees of polymerization. This was evaluated by viscosity measurements of the polymer in water solution. Polymer adsorption, zeta potential, fluidity and compressive strength of cement mixtures have been examined as a function of the degree of polymerization and the polymer dosage. Polymer adsorption, zeta potential and fluidity increase by increasing the polymer dosage in the range of 0.25 -2.00 % by weight of cement. Polymer adsorption, zeta potential, fluidity increase by increasing the degree of polymerization. However, above a certain degree of polymerization all the above mentioned properties do not change further. Cement particles adsorb the polymer molecules and this causes an increase in the electrical charge on the cement surface. This results in a better dispersion of cement particles and a more fluid system. However, even if there is a certain interaction between fluidity and zeta potential, the latter is not the only parameter controlling the fluidity of the system. At the same water/cement ratio, by increasing the degree of polymerization the strength is, in general, slightly increased and this seems to be related to a better dispersion of cement particles.

Strength, elasticity, shrinkage, swelling and creep of water-cured and steam-cured concretes (made with a rapid-hardening Portland cement) with and without the superplasticising admixture, Irgament ‘Mighty’ 150, have been compared over a period of one year. The mixes have the same workability but the one with the admixture clearly has a lower water-cement ratio. Compared with the admixture-free concrete, the superplasticiser concrete has a higher strength and a higher modulus of elasticity when continuously stored in water from the age of one day. However, when exposed to drying at the age of two days, the superplasticiser concrete has higher shrinkage and creep at a constant stress-strength ratio, and, at later ages, lower compressive strength and modulus of elasticity. For the tests in which the same two concretes were subjected to a six-hour cycle of steam curing and then stored in water, the compressive strength and static modulus of elasticity are initially higher but, at later ages, this is reversed for the superplasticiser concrete; in addition, the creep is higher for this concrete. When the same steam-cured concretes are exposed to drying at the age of one day, none of the properties investigated is affected by the presence of the superplasticiser.

The studies reported were concerned with the application of high-strength concrete to structural members as related to some aspects of their design, construction and behavior. With regard to construction, tests were performed on the consistencies and strengths of concretes of low water-cement ratios using superplasticizers. The superplasticizers used were the 5 brands being marketed in Japan. The influence on consistency of fineness of cement was also studied. In examinations made by design calculations, monorail piers were used as case studies. The relation between concrete strength and cross-sectional dimensions, and quality of reinforcing bars required when applying high-strength concrete to structural members were investigated. In structural tests, the stresses, bending strengths and ductilities of model piers using high-strength concrete were studied.

A series of laboratory and field studies were conducted to determine the engineering properties of concretes containing a sulphonated naphthalene formaldehyde condensate superplasticizer (MIGHTY). In laboratory studies, conventional and superplasticized concretes with slumps from 12 to 21 cm were placed into moulds for full-size, single-frame models of reinforced concrete structures for measurements of form pressures and response to internal vibration as well as tests on the strengths and drying shrinkage in finished structures. Superplasticized concrete indicated greater response to vibration than and equal form pressures to conventional low-slump concrete. Higher core strengths were obtained with superplasticized concrete than with conventional concrete, while no change was observed in drying shrinkage with addition of the admixture. Further studies were conducted on ordinary and lightweight aggregate concretes in the construction of a ten-storey, reinforced concrete structure. Higher fluidity was observed in super-plasticized concrete, while the same trends as in the laboratory were observed regarding form pressure and core strengths. The test results on pumpability indicated that superplasticized lightweight aggregate concrete can be pumped at a lower pressure to a height of fifty meters without adversely affecting concrete properties.