Properties of Concrete at Elevated Temperatures

Table 2

Values of the main parameters of the stress-strain relationships of NSC and HSC at elevated temperatures as specified in EN1992-1-2: 2004 [4].

Temp. °F	Temp. °C	NSC						HSC
		Siliceous agg.			Calcareous agg.			𝑓^′𝑐,𝑇/𝑓^′𝑐(20^∘C)
		𝑓^′𝑐,𝑇/𝑓^′𝑐(20^∘C)	𝜀𝑐1,𝑇	𝜀cu1,𝑇	𝑓^′𝑐,𝑇/𝑓^′𝑐(20^∘C)	𝜀𝑐1,𝑇	𝜀cu1,𝑇	Class 1	Class 2	Class 3
68	20	1	0.0025	0.02	1	0.0025	0.02	1	1	1
212	100	1	0.004	0.0225	1	0.004	0.023	0.9	0.75	0.75
392	200	0.95	0.0055	0.025	0.97	0.0055	0.025	0.9	0.75	0.70
572	300	0.85	0.007	0.0275	0.91	0.007	0.028	0.85	0.75	0.65
752	400	0.75	0.01	0.03	0.85	0.01	0.03	0.75	0.75	0.45
932	500	0.6	0.015	0.0325	0.74	0.015	0.033	0.60	0.60	0.30
1112	600	0.45	0.025	0.035	0.6	0.025	0.035	0.45	0.45	0.25
1292	700	0.3	0.025	0.0375	0.43	0.025	0.038	0.30	0.30	0.20
1472	800	0.15	0.025	0.04	0.27	0.025	0.04	0.15	0.15	0.15
1652	900	0.08	0.025	0.0425	0.15	0.025	0.043	0.08	0.113	0.08
1832	1000	0.04	0.025	0.045	0.06	0.025	0.045	0.04	0.075	0.04
2012	1100	0.01	0.025	0.0475	0.02	0.025	0.048	0.01	0.038	0.01
2192	1200	0	—	—	0	—	—	0	0	0

The Eurocode classifies HSC into three classes*, depending on its compressive strength, namely,
(i) class 1 for concrete with compressive strength between C55/67 and C60/75,
(ii) class 2 for concrete with compressive strength between C70/85 and C80/95,
(iii) class 3 for concrete with compressive strength higher than C90/105.
The strength notation of C55/67 refers to a concrete grade with a characteristic cylinder and cube strength of 55 N/mm² and 67 N/mm², respectively.
*Note: where the actual characteristic strength of concrete is likely to be of a higher class than that specified in the design; the relative reduction in strength for the higher class should be used for fire design.