| Summary: | 碩士 === 國立臺灣科技大學 === 營建工程系 === 106 === The use of ground granulated blast-furnace slag (GGBFS) as cement replacement has a lot of advantages. From experimental results, on w/b ratio of 0.3, at age of 28 days, the compressive strength of 10% GGBFS blended paste and mortar reached the values up to 82.25 MPa and 92.78 MPa, respectively. Cement substitution with GGBFS up to 50% led to similar or slightly higher strength at ages of 28 and 56 days as compared with that of the control sample. Based on the experimental data, the mathematical equation to predict the compressive strength of paste and mortar at ages of 28 and 56 days as a function of w/b and GGBFS percentage of OPC replacement has been proposed..
Although the addition of GGBFS has many benefits, its initial lower hydration rate leads to lower early strength. Therefore, in this study, an attempt of using the sodium silicate (waterglass) as alkaline solution was carried out as chemical activator to promote the early strength of GGBFS blended paste. However, the incorporation of 5% and 10% of waterglass led to degradation of mechanical properties especially on compressive strength. Reduction of compressive strength of alkali-activated GGBFS blended paste with 10% waterglass was 7.5%, 47.2% and 24.8% for w/b of 0.3, 0.4, and 0.5, respectively, compared with the compressive strength of non-alkali-activated GGBFS blended paste. Thus, using 5% or 10% of sodium silicate to partially replace the mixing water is unable neither to enhance the pozzolanic reaction of blended paste nor to improve the early age strength.
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