Details

Autor(en) / Beteiligte

• Wong, H. S.
• Poole, A. B.
• Wells, B.
• Eden, M.
• Barnes, R.
• Ferrari, J.
• Fox, R.
• Yio, M. H. N.
• Copuroglu, O.
• Guðmundsson, G.
• Hardie, R.
• Jakobsen, U. H.
• Makoubi, K.
• Mitchinson, A.
• Raybould, P.
• Strongman, J.
• Buenfeld, N. R.

Titel

Microscopy techniques for determining water–cement (w/c) ratio in hardened concrete: a round-robin assessment

Ist Teil von

• Materials and structures, 2020-04, Vol.53 (2), Article 25

Ort / Verlag

Dordrecht: Springer Netherlands

Erscheinungsjahr

2020

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Water to cement (w/c) ratio is usually the most important parameter specified in concrete design and is sometimes the subject of dispute when a shortfall in concrete strength or durability is an issue. However, determination of w/c ratio in hardened concrete by testing is very difficult once the concrete has set. This paper presents the results from an inter-laboratory round-robin study organised by the Applied Petrography Group to evaluate and compare microscopy methods for measuring w/c ratio in hardened concrete. Five concrete prisms with w/c ratios ranging from 0.35 to 0.55, but otherwise identical in mix design were prepared independently and distributed to 11 participating petrographic laboratories across Europe. Participants used a range of methods routine to their laboratory and these are broadly divided into visual assessment, measurement of fluorescent intensity and quantitative backscattered electron microscopy. Some participants determined w/c ratio using more than one method or operator. Consequently, 100 individual w/c ratio determinations were collected, representing the largest study of its type ever undertaken. The majority (81%) of the results are accurate to within ± 0.1 of the target mix w/c ratios, 58% come to within ± 0.05 and 37% are within ± 0.025. The study shows that microscopy-based methods are more accurate and reliable compared to the BS 1881-124 physicochemical method for determining w/c ratio. The practical significance, potential sources of errors and limitations are discussed with the view to inform future applications.