A structural investigation relating to the pozzolanic activity of rice husk ashes

Journal Article · Sun Jun 15 04:00:00 EDT 2008 · Cement and Concrete Research

DOI:https://doi.org/10.1016/j.cemconres.2007.10.004· OSTI ID:21130730

Fraaij, Alex ^[1]; Klaassen, Adri A.K.; Kentgens, Arno P.M. ^[2]

---

1. Civil Engineering and Geosciences, Materials Science and Sustainable Construction, Delft University of Technology (Netherlands)
2. Physical Chemistry/solid-state NMR, Institute for Molecules and Materials, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen (Netherlands)

Various factors determine the applicability of rice husk ash (RHA) as a pozzolanic material. The amount and accessibility of reactive sites is thought to be a key factor. A structural study of RHA samples in relation to their reactivity has been performed; Silica in RHA formed by burning rice husk in a laboratory furnace under continuous supply of air have been characterized as a function of incineration temperature, time and cooling regime. The characterization methods included chemical analyses, conductivity measurements, microscopic analysis, X-ray diffraction (XRD) and {sup 29}Si magic-angle spinning (MAS) nuclear magnetic resonance (NMR). In line with earlier observations, the analyses show that the highest amounts of amorphous silica occur in samples burnt in the range of 500 deg. C-700 deg. C. The {sup 29}Si NMR data allow direct identification of the reactive silanol sites in the RHA samples. De-convolution of the NMR spectra clearly shows that the quickly cooled RHA resulting from burning rice husk for 12 h at 500 deg. C has the highest amount of silanol groups. This sample also induced the largest drop in conductivity when added to a saturated calcium hydroxide solution giving an indication of its reactivity towards lime. Therefore, this RHA is the favorable sample to be used as pozzolanic cement additive.

• OSTI ID: 21130730
• Journal Information: Cement and Concrete Research, Journal Name: Cement and Concrete Research Journal Issue: 6 Vol. 38; ISSN 0008-8846; ISSN CCNRAI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ADDITIVES
ASHES
AVAILABILITY
CALCIUM HYDROXIDES
CEMENTS
CHEMICAL ANALYSIS
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
REACTIVITY
SILICA
SILICON 29
TEMPERATURE RANGE 0400-1000 K
X-RAY DIFFRACTION