دانلود رایگان مقاله بررسی چند روش متاکائولین و سرباره مخلوط خمیر سیمان پرتلند

ABSTRACT

Increasing incorporation of metakaolin (MK) into field concrete mixtures necessitates careful study of the portland cement/MK hydrating systems. While a number of studies have been conducted on MK blends with cement, the current knowledge on its effect on hydration products and paste microstructure remains incomplete. This study evaluated the effect of MK on the nature of hydration products through X-ray diffraction, while the effect on microstructure was assessed by measuring porosity with nitrogen adsorption and determining nanoindentation modulus as well as volume fractions of CSH with varying packing densities. The 10MK paste hydrated for 7 days was compared to the plain ordinary portland cement (OPC) paste as well as to paste containing 52% slag (52SL). No significant effect was observed on the nature of hydration products with MK or SL addition. However, nitrogen-accessible porosity increased with MK and SL addition, the increase being larger with SL. The average indentation modulus for hydration products decreased with addition of MK and SL which corresponded to increasing nitrogen accessible pores.

4. Conclusions

The following conclusions can be made based on the findings of this study: • Generally, addition of chemical and mineral admixtures did not change the main hydration products for mixtures cured at 23 °C. No significant differences in phase consumption were observed with addition of 10% metakaolin or 52% slag compared to the control paste at 7 days. • Despite the similarity in phase consumption and the hydration products formed, nitrogen adsorption measurements indicated an increase in LGP volume with addition of 10% MK and 52% SL as well as an increase in the fraction of capillary pores accessible by nitrogen adsorption technique. • Nanoindentation measurements also indicated an increase in CSH porosity with 10% MK and 52% SL addition, the highest increase resulting from SL incorporation which is in agreement with nitrogen adsorption measurements. • Additionally, a linear relationship was observed between the average elastic modulus of the hydration products obtained from nanoindentation and the volume of LGP from N2 adsorption. A linear relationship was also observed between the average elastic modulus and compressive strength.