There are two methods for fire damage assessment of buildings which are explained below:
- Differential Thermal Analysis (DTA) – Lab Test – Determination of qualitative and quantitative composition of specimen of concrete
- X-ray Diffraction (XRD) – Lab Test – To assess the extent of deterioration in concrete exposed to fire
Differential Thermal Analysis (DTA)
DTA is utilized for the study of the physical and chemical alterations that happen in a substance when it is warmed up so as to depict the substance. It is basically related with the degree of alteration of temperature of a specimen as it is warmed at a uniform rate of heat flow.
The standard on which DTA is depended is that when a substance is gradually heated, its temperature increases but when the substance experiences any endothermic reaction, for example losing water, losing CO2, alteration in crystalline structure or decomposition, its temperature remains uniform throughout.
The outcome of DTA are indicated in the form of DTA curves. The specimen and an inert substance are warmed in detached containers and the change of temperature amongst the two is chronicled by resources of thermocouples which produces an electrical signal each time there is a temperature change amongst the reference and the specimen. At the point where there is no endothermic reaction in the specimen, there would not be any change in the temperature amongst the reference and the specimen and henceforth no electrical signal would happen. Any endothermic alteration would yield a thermal differential and consequently an electric pulse. The incidence of the pulse looks like as a peak in the DTA curve which is a plan of temperature versus electrical signal produced. Benefit of DTA over TGA is that the variations not connecting weight loss can also be noticed.
By looking at the DTA curve of an example with that for known mixes, subjective composition of the specimen can be mediated. Quantitative synthesis of the specimen can likewise be judged by measuring the size of the crest in the DTA curve. The crest size is straightforwardly connected with measure of warmth required in a transition.
However, in case there is a chance that a solid example is examined, endothermic peak because of calcium hydroxide is found at 500 degC. The peak because of transformation of silica happens at 570 deg.C. At the point when different fire harmed tests of cement are subjected to DTA, the nearness of crest at 500 deg.C demonstrates that calcium hydroxide is available and that the example has not been subjected to temperature more than 500 deg.C. In the event that pinnacle of 570 deg C is just present, it implies that silica transformation had not happened in the specimen and it was not subjected to temperature more than 570 deg.C. On the off chance that no pinnacle is there, it implies that example was subjected to temperature surpassing 500 deg.C.
X- ray Diffraction (XRD)
X – beam diffraction depends on the rule that a precious stone of a substance has a special diffraction design. At the point when monochromatic X –ray pillar falls on a gem it gets reflected by the different crystalline planes. Obstruction happens among the different reflected shafts bringing about a diffraction design comprising of dull and splendid edges, contingent on the stage contrast among the meddling bars.
A crystal whose structure is obscure can be recognized by acquiring its diffraction example and contrasting it and diffraction example of officially distinguished gem. The diffraction example of a solitary crystal comprises of various single spots yet when powder test is utilized, the diffraction on example comprises of a progression of diffraction lines.
By this procedure the span of crystal planes the sub-atomic structure of the example can be resolved. It can likewise be discovered whether the example is a solitary compound or comprises of more than one compound. If there should arise an occurrence of polymers, level of crystallinity can be discovered in light of the fact that the non-crystalline part will disperse the X-beam shaft to give a persistent foundation while the crystalline segment will give spasmodic diffraction design.
As respects to the evaluation of the fire harm, X-beam diffraction can be utilized to decide the degree of crumbling in solid that has been subjected to flame. The temperature to which the harmed concrete has been subjected to can be controlled by this technique.