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The reduction in the useful-service life of reinforced concrete structures in the coastal areas of the Arabian Gulf is of major concern to the construction industry. The harsh climatic conditions, high level of chloride and sulfate contamination in the environment, low quality and contaminated aggregates, and substandard construction practices constitute the major causes of deterioration of reinforced concrete structures in less than 10 years in this part of the world. Since the concrete deterioration phenomena are strongly permeability dependent, mineral admixtures and industrial by-products, such as natural pozzolan, fly-ash, blast-furnace-slag, and silica-fume are increasingly used to improve its durability. Among the mineral admixtures and industrial by-products, fly-ash and silica-fume are considered to be more beneficial due to their superior performance in improving concrete durability. However, to attain beneficial properties, pozzolanic concrete needs early and extended curing compared with normal portland cement concrete. This is of particular concern in the Arabian Gulf environment, where the high ambient temperatures, solar radiation and blowing winds make curing a difficult process. Therefore in this study, the effect of temperature and drying as well as different curing conditions on the compressive strength development in normal Portland, silica-fume and fly-ash cement concretes was evaluated. The test specimens were cured in the laboratory and under field conditions, and tested 1,3,7, 14,28, 60 and 90 days after casting to evaluate the compressive strength development. The results indicated an increase in the compressive strength, in both the normal, fly-ash and silica-fume cement concrete specimens with the period of curing. Field curing had more negative effect on the strength development in concrete specimens containing fly-ash and silica-fume than in the plain concrete specimens. High temperature casting and curing increased the compressive strength in both plain and fly-ash concretes. Drying during curing produced the highest strength the silica-fume concrete specimens compared to plain and fly-ash concretes.

The Siberian State Academy for Mining and Metallurgy (SSAMM) and Uglestrinproject have developed a project for complex utilization of waste produced by burning brown coals from Kansk-Achinsk Power Complex at the Abakan thermal power plant. The project provides for total utilization of ashes and slags to the thermal power plant for producing finished ‘cementless’ binder and aggregate, finished ‘cementless’ fine ash/slag concrete and mortar, precast reinforced concrete structures and small products (silicate brick). Previous investigation of ash and slag from the thermal power plant and concretes on their base was completed in 1995. After grindiig and introducing silica mme, ash and slag to meet the requirements of State Standard 25818-91, concrete is in accordance with State Standard 26633-91. The technological complex providing loo-percent utilization of waste products from the TPP includes departments for grinding ash with a storage, for producing sand from slag with a storage, molding with concrete mixers and premises for admixtures. The project has been approved by a nature committee of the Khakass Republic and is in accordance with the ecological standards. The construction of the complex is currently under way.

In Thailand, the utilization of fly ash as a concrete admixture has been increasing gradually. However, there are no local standards regulating the use of fly ash. Mixing of concrete usually follows standards that contain requirements, especially temperature, that are difficult or sometimes impossible to satisfy. Therefore, this research was carried out to verify the influence of temperature, hot (Thailand) and temperate (Japan) climate, on the strength and durability properties of fly ash mortar. Also, to propose an optimum range of cement replacement percentage and water-binder ratio for each kind of fly ash under Thai (simulated) and Japanese climate conditions. From this investigation, it was found that fly ash exhibited advantages in strength and durability of mortar under high temperature. The strength activity index of both fly ash mortars were satisfied in accordance with ASTM C 618 under all temperatures considered. Furthermore, the optimum range of cement replacement and water-binder ratio became wider with increasing temperature. Thus, fly ash is recommended to be used under high temperature.

A significant influence of the type of cement on the pozzolanic reaction is well known with respect to fly ash. Principally, looking at silica fume, these effects must be similar. The investigations described in the paper focused on extremely high pozzolan additions compared with practice (fly ash up to 60 mass silica fume up to 25 mass-%). The objective of the research work was to explore the meaning of characteristic properties of the cement with regard to pozzolanic reaction. The most relevant parameters to be included in these inve-stigations were the amount of Ca(OH)z provided by the hydration of the cement (depending on the clinker content) and the alkali content of the pore solution (depending on the cements contribution due to readily soluble alkalies). The results of systematic variations (varying clinker contents of the cement, additional supply of Ca(OH)2 and alkalies) reveal the distinction in the significance of the different parameters.

Elasticity, shrinkage, and creep to one year were measured on 150 mm diameter by 300 mm cylinders made from concrete with crushing strengths of 40 and 70 MPa and slumps of approximately 80 mm. Within each strength grade a 25% fly ash replacement concrete was designed to match the normal portland cement (NPC) slump and 28 day strength. Creep samples were loaded at 3, 7, 14 and 28 days after water curing at 27°C and then tested in air at 25 o C and 65% relative humidity to approximately match Hong Kong’s sub-tropical climate. The maximum interval between readings was 14 days. Interface creep cylinder surfaces were ground. Hong Kong materials were used. The ash has a cementing efficiency that varies from 74 to 114% and typically has a silica content of 52% and an alkali oxide content of 3%. The admixtures used were a lignosulphonate/carbohydrate retarding water reducer/plasticiser, and a napthalene sulphonate and modified lignosulphonate superplasticizer. Hong Kong elasticities can be low due to the aggregates used; a granite in this study. There was little difference between the NPC and fly ash pairs of concrete samples at the end of one year. The similarity is considered to be due to the high fly ash cementing efficiency and the relatively high humidity testing regime. There was little variation in the 12-month elasticities and shrinkages between the four curing ages but big decreases in the 12-month load induced specific creeps.