Pore Structure and Strength Prediction of Fly Ash Concrete


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Title: Pore Structure and Strength Prediction of Fly Ash Concrete

Author(s): A.-S. Cheng, T. Yen, Y.-N. Sheen, and K.-C. Jane

Publication: Special Publication

Volume: 242


Appears on pages(s): 419-432

Keywords: capillary porosity; fly ash concrete; strength prediction

Date: 4/1/2007

This research aims to investigate the pore structures of fly ash concrete and the relation between porosity and compressive strength, and accordingly to establish a strength prediction model. In the study, three water-to-binder ratios (0.35, 0.50, 0.70) and three substitution ratios of cement with fly ash (10%, 20%, 30%) were selected for preparing concrete specimens. These specimens were tested at six ages from 1 day to 91 days for compressive strength and MIP porosity measurement. Test results show that the fly ash concrete consisted of more micro-pores that were larger than 0.05µm at an early age (7 day),but this portion of micro-pores evidently decreased after 28days. It was also found that the capillary pore volume had the closest relation with the strength of fly ash concrete, and the correlation coefficient reaches to 0.954. To establish the strength prediction model, a prediction equation of capillary porosity in fly ash concrete was firstly developed. The proposed prediction model is shown as the following: f'c=a·ln(W/B)+b·ln(R)+c·ln(age)+d·ln(Vc)+e. The calculated results show that the proposed model compared favorably with the other prediction model.