Influence of test set up on sulphate swell measurements

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Paramor, R., Mcgrath, E., Beetham, P. ORCID: 0009-0005-7125-4141 and Belton, D., 2021. Influence of test set up on sulphate swell measurements. In: British Lime Association Symposium on UK-Lime Research, Virtual, 21 October 2021.

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Abstract

Sulphate swell is a known risk in lime stabilisation and existing literature attributes this to water inundation causing growth of ettringite or thaumasite. Recent studies show sulphate swell is greater at UK site relevant temperatures of 10°C compared to the 20°C often used in laboratory tests and that a mould around samples could limit water ingress.

This study assessed the swell potential of a low and high sulphate soil treated with 3% quicklime. A range of different swell test set ups promoted environments potentially relevant to site scenarios. Two of the swell test methods were based around British Standard methods for soaked California Bearing Ratio (CBR) and accelerated swell tests but using 10°C soaking water and variations saturated with gypsum. A third novel set up (The NTU sulphate swell test) permitted 10°C water to access specimens via a 1-2mm sand surround and including variations with aerated water intended to promote thaumasite growth.

Findings confirm the pathway for water access is highly influential in the degree of swell measured by tests at 10°C, with the most swell measured in the unconfined accelerated swell tests. Adding gypsum to the soaking water caused up to 6.5% expansion in low sulphate samples that otherwise did not swell in tap water, and even higher expansion (22%) in the high sulphate soils. Swell was much less in CBR tests with intermediate amounts in the NTU test. Mineralogy tests indicate only very small amounts of ettringite formed in any specimen and the sulphate swell appears due to unbound water and a potential swell mechanism is discussed.

Item Type:

Conference contribution

Creators:

Paramor, R., Mcgrath, E., Beetham, P. and Belton, D.

Date:

October 2021

Identifiers: