Title: Temperature-related performance factors for chemical demolition agents
Authors: Minh Phuoc Huynh; Debra F. Laefer; Jenny McGuill; Aisling White
Urban Modelling Group, School of Civil Engineering, University College Dublin, Newstead G67, Belfield, Dublin 4, Ireland
Urban Modeling Group, Center for Urban Science and Progress, New York University, 1 MetroTech Center, 19th Floor Brooklyn, NY 11201, USA
Freeman Beesley M&E Consultants, Brighton, East Sussex, UK
Kerry Group, Dublin, Ireland
Abstract: Soundless chemical demolition agents (SCDAs) are percussion-free alternatives to blasting for selective demolition. Although known to be temperature sensitive, to date their performance has not been quantified in ambient environments below 20°C. This paper examines 6 large-scale specimens at 16.1-19.3°C. Substantially slower response than that reported by manufacturers was documented. Initial cracking required 25 + h and continued for 4-8 days. Cracks opened rapidly after minimum demolition time [(MDT)-cumulative cracking around the perimeter reaching ~25 mm], which was at 42 and 70 h, respectively in 16.8 and 33.1 MPa specimens. Post-MDT, crack width opening velocities were 0.35-0.96 mm/h, approximately one-third to two-thirds pre-MDT velocities. A 0.5°C ambient temperature drop delayed MDT by 6.5 h amongst equi-sized specimens of the same strength. Generally, MDT correlated with material strength (irrespective of ambient temperature or specimen size), whereas time to first crack was more influenced by temperature. Also, SCDA reapplication proved effective for incompletely cracked specimens.
Keywords: concrete; cracking; demolition; expansive cements; masonry conservation; SCDAs.
Int. J. of Masonry Research and Innovation, 2017 Vol.2, No.2/3, pp.220 - 240
Submission date: 23 May 2016
Date of acceptance: 20 Dec 2016
Available online: 03 Aug 2017