EFFECT ON SLAG HYDRATION OF BLAST-FURNACE SLAG CEMENT IN DIFFERENT CURING CONDITIONS

In Japan, the usage of blast furnace slag in constr uction will increase due to environmental considera tions. However, the effect of curing condition and curing period on the hydration of cement and slag hydration in blen ded cements is not clear, nor is the relative contribution of cement a d slag hydration to strength and durability develo pment in blended cement. In this research, the cement and slag hydra tion ratio in blast-furnace slag cement under diffe rent curing conditions, such as temperature, relative humidity, and curing period, is measured using the selective dissolution method. It was found that hydration stops if relati ve humidity is less than 80%, and that if 80% relat ive humidity is maintained hydration can occur even at temperatures as low as 7 degrees Celsius. On the other hand, th e speed of hydration is faster at higher temperatures such as 40 degrees Celsius than at normal temperatures such as 20 degrees Celsius, so it can be concluded that the influence of temperature on blast-furnace slag in blast-furna ce slag cement is similar to that of temperature on ordinary Portland cement. The hydration of blast-furnace slag is als o influenced by mix proportions such as water-cement ratio and Blai ne’s fineness of cement. In the case of high watercement ratio, the hydration ratio of slag will increase and reach a h ig hydration ratio; however, in the case of low wa ter-cement ratio the hydration of slag will stop at a low hydration ratio at an early age. Using these results showing the hydration ratio of slag with different mix proportions and curing c onditions, estimation of the hydration of blast-fur nace slag cement under different conditions may be performed. Originality Until now, measurement of the hydration ratio of bl ast-furnace slag in blast-furnace slag cement has b een performed under sealed condition – which represents the ideal case – in order to clearly show the slag hydration . However, these conditions are not reflective of the actual conditi ons of concrete structures, so it is important to e stimate the hydration ratio of blast-furnace slag under real conditions c onsidering both varying temperatures and relative h umidity. It is also necessary to consider the effect of hydration ratio varying mix proportions and different types of blast furnace slag. Chief contributions Concrete structure is exposed to various environmen t such as drying condition, high relative humidity and different temperatures. And also internal condition in concre te structure is influenced high temperature by the heat of cement hydration. Estimation of the hydration of blast-fur nace slag in blast-furnace slag cement on different condition is necessary for estimating the properties and durabil ity of concrete structures. Currently, it is possib le to estimate durability properties such as drying and autogeneou s shrinkage, strength for concrete structures using ordinary Portland cement from hydration of cement on mix pro po tions, but it is difficult to apply the same met hods when using blast-furnace slag cement, because it is different of cement hydration and slag reaction. This researc h may contribute to increasing the usage of blast-furnace slag in co struction and thus helping to protect th e global environment.