Test method for concrete spalling using small electric furnace

Abstract

SUMMARYConcrete spalling can cause severe damage to concrete structure when exposed to fire. The spalling mechanisms are not very well understood. For the testing of spalling, full-scale structural members should be used, as spalling tests are sensitive to size effects. Full-scale testing in large furnace is costly and is not suitable for testing large number of concrete mixture trials. The standard and hydrocarbon fire time-temperature curves have rapid temperature rise during the initial phase. This temperature rise requires a gas furnace with high heating capacity and cannot be generated by electric muffle furnace commonly available in many laboratories.This paper presents a method to carry out spalling test in small-scale specimens with exposure to rapid temperature rise using a commonly available electric furnace in the laboratories. The tests are based on 150 mm diameter cylinders that are laterally confined to simulate full-scale structural members. The cylinder surface is exposed to rapid temperature rise by exposing through vertical and/or horizontal holes in pre-heated small electric furnace. Some unconfined 100 mm diameter cylinders were also exposed horizontally to test the performance of confinement. The paper shows that the hydrocarbon fire and standard fire exposure can be simulated by manipulating the exposure location of the surface of the concrete cylinder. Ordinary Portland cement concrete cylinders with different strengths were tested and different spalling patterns were observed. The spalling patterns matched the test results from a gas furnace fire test simulating the fire curves. The tests demonstrated that the method is an effective and convenient technique to predict the spalling risk of a concrete.

The effect of various fire‐exposed surface dimensions on the spalling of concrete specimens

“…In a small-scale test method proposed by Hertz et al [15] only the front side of a cylinder is exposed to fire while the whole cylinder is surrounded by a steel mantle. This methodical approach simulates a part of a fireexposed surface of a concrete slab or wall [16]. Here, the test results appear to confirm those retrieved from a full-scale test, but in other studies, results of small-scale tests are contradictory, even with the same concrete mixture [17].…”

“…Further six TCs (No. [11][12][13][14][15][16] were fixed at the rear side of the specimen (Figure 2). The detailed positions of all TCs are given in Table III.…”

Fire induced concrete spalling in combination with size effects

“…Table 1 shows different publications of single-sided fire tested concrete specimens for one specimen size and comparative multi-scale studies. It is not possible to investigate the size effect by comparing small scale specimens [21,22], intermediate scale specimens [23,24] and large members [25] provided by different studies. The spalling of the specimens increases while comparing these studies of small scale specimens [21] and full scale members [25].…”

Possibilities of observation of behaviour of concrete- and cement-based composite materials exposed to high temperatures

“…1 For experimental verification of smaller test specimens, the research team at the Brno University of Technology, Faculty of Civil Engineering, built new testing furnace (dimensions of the inner space are ca 800 × 800 × 800 mm, see Fig. 1).…”