Time:10:00,October 28, 2019

Venue: 441 conference room, School of materials science and engineering, Jiading Campus

Topic：The role of moisture in fire spalling of concrete

Lecturer：

Leo Pel is an Associate Professor in the group transport in Permeable Media at the Department of Applied Physics, Eindhoven University of Technology (TU/e). He obtained his MSc in Applied Physics and received his PhD from the Department of Architecture, Building and Planningat TU/e for his thesis ‘Moisture transport in porous building materials’ in 1994. Following this, he worked as a Postdoctoral Researcher on development of a measurement method to determine moisture transport processes in porous materials. In 2006, he was a Visiting Researcher at the J. Paul Getty Museum and in 2008 he was a Visiting Fellow at Princeton University at the group of George Scherer. He is involved in various national and international projects focusing on understanding the durability of porous materials. In addition, he has taken part in various EU programs focusing on the conservation of our cultural heritage.

Abstract：

The question how concrete responds to a fire is one of the main questions in fire safety. During a fire, a building material can suddenly be heated up to temperatures well above 1000℃. At temperatures above 100℃ water inside the pores will start to boil. Simultaneously, in concrete, but also for example in gypsum, chemically bound water will be released by dehydration of the porous matrix. If the concrete has a low permeability, the vapour pressure inside will increase which can give rise to a sudden (explosive) failure of a material. Numerous heat and mass transfer models have been used to predict the moisture transport and its consequences on the strength and permeability of the concrete. However, these models are only of use if they can be validated. By using NMR we can get direct insight into the processes taking place and hence give as a tool to develop a simple model to determine the pressure build up. These measurements gave the first quantitative proof for the build-up of a moisture peak due to the vapour pressure build-up, which will be explained.

火焰作用下混凝土性能與結構是如何響應的是防火安全中的一個重要問題。建築材料在火焰的作用下，可瞬間升溫至1000攝氏度以上。不難想象，高于100攝氏度以上，建築材料内部的水分會處于氣化狀态。同時，混凝土中的組分(以石膏為例)，化學結合水亦會在脫水作用下通過孔隙釋放。如混凝土的滲透性較低，混凝土内蒸氣壓的激增勢必會導緻材料結構與性能的瞬間劣化(或爆裂)。以往研究應用了不同傳熱與傳質模型以預測水分傳輸特征，探索了水分傳輸特征對于混凝土力學性能與滲透性的影響。但由于研究方法的限制，這些模型均未被試驗數據所驗證，因而導緻相關研究成果缺乏普适性。本研究利用核磁共振技術，得到了關于火焰作用下混凝土水分遷移最為直接的信息，發展了一種關于蒸氣壓升高的簡易模型，并首次定量性地發現了蒸氣壓作用形成的水分信号峰，進一步結合試驗數據，本研究對水分信号峰産生原因及影響因素進行了深入的讨論。