International Concrete Abstracts Portal

In 1997, CANMET in association with the American Concrete Institute and several other organizations in Australia sponsored the Fourth International Conference on the subject. The conference was held in Sydney, Australia. More than 120 papers from 30 countries were received and peer reviewed in accordance with the policies of the American Concrete Institute; 81 were accepted for publication. The accepted papers deal with all aspects of durability of concrete, including chloride and sulphate attack, freezing and thawing cycling, alkali-aggregate reactions, cathodic protection, and the role of supplementary cementing materials to enhance durability of fiber-reinforced concrete and performance of repaired concrete structures. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP170

This paper presents a laboratory accelerated method for measuring the effective chloride diffusion coefficient of concrete using the static diffusion cell technique. The method is based on initially saturating specimens with chlorides before testing them, in order to accelerate the time required to achieve steady state diffusion. The effective diffusion coefficient can be obtained after 7 to 10 weeks. Saturation of specimens was achieved by two procedures. The first one was simple vacuum-saturation, the second method was saturation by the applied voltage technique using 30V or 40V potential difference. The results of these experiments showed that saturating the specimens with chlorides does not affect the diffusion process, as indicated from the chloride concentration profiles across the specimens before and after testing in the diffusion cells. The steady state condition during the diffusion test is only achieved at 10 to 14 days of diffusion time. This is a relatively short time when compared to the time that it takes to obtain results using the conventional method. The total test period was reduced to 7 weeks to obtain the effective diffusion coefficient through relatively thick concrete and mortar specimens (25 mm). Data obtained for a wide range of mortars treated with surface coating compounds and for high performance concrete is compared with values of diffusion coefficients obtained from the unsteady state ponding method. A reasonable statistical conversion equation is proposed in order to compare or convert values of one test to another.

An organic shrinkage reducing agent consists mainly of lower alcohol alkylene oxide adducts. It has a great effect of reducing drying shrinkage. There are few studies on durability of concrete with the shrinkage reducing agent. This paper presents the results of a study on durability of concrete with the shrinkage reducing agent exposed to outdoor in a cold district for 10 years. Flexural strength, compressive strength and dynamic modulus of elasticity of concrete with the organic shrinkage reducing agent has not shown any problems as same as concrete without the agent even at the age of 10 years. Therefore, in a cold environment, it is thought that concrete with the shrinkage reducing agent, which contains a sufficient air content, will not be deteriorated by freezing and thawing action.

Ferronickel slag is a by-product produced when refining ferronickel from nickel ores. Investigations were conducted for a long time to use this hard slag as aggregate in concrete, and it was standardized in October 1992 as JIS A 5011 (Slag aggregate for concrete). However, one of the types produced in Japan was excluded from the standard, as it was alkali-aggregate reactive. The authors applied various measures specified in other standards to suppress reactivity of this type of ferronickel-slag aggregate, and experimentally confirmed that the following measures are effective: (i) the use of low-alkali cement, (ii) addition of fly ash, and (iii) addition of ground granulated blast-furnace slag.

This paper describes the results of the study on the durability evaluation of Mt. Pinatubo blended cement mortar under accelerated conditions of acidic, sulphate and alkali-silica reactive regimes. Various types of ejecta materials and percentage cement replacements (i.e., 10, 20, 30, 40, 50, 60, 70, and 80%) were investigated to determine the optimum type and proportion in a cement-based mortar matrix based on the criteria of strength, dimension stability, resistance to alkali-aggregate reaction and severe environmental conditions. Test results indicated that the use of Pinatubo pozzolans are effective mineral dmixtures against acidic, sulphate, alkali-aggregate reactions. Optimum pozzolans proportions ranges from 40-60% under varying conditions. Dimension stability and shrinkage properties of mortar with Pinatubo pozzolans are basically comparable to plain portland cement mortar, indicating stability of the pozzolans as a concrete constituent material. Alkali-aggregate reactivity test of selected samples of Pinatubo aggregate also showed innocuous characteristics.