def c_conductivity_EC_T(Temp, limit='lower'):
    """ concrete thermal conductivity at elevated temperature, accord. EN 1992-1-2 (pp. 28)
	
	Parameters
	----------	
	Temp : float or np.array
		(array of) Temperature in range 20 - 1200 [°C]
		
	limit : String
		'lower'  = lower bound Eurocode conductivity - recommended value (default)
		'upper' =  upper bound Eurocode conductivity - value for composite structures

	Returns
	-------
	lambda_c : float or np.array
		 thermal conductivity of concrete [W/m K]
	 
	Example use
	-----------
	>>> import numpy as np
	>>> import magnelPy.SFE as sfe
	>>> Temp = np.arange(20,1101,20)
	>>> eps = sfe.ThermalTools.c_conductivity_EC_T(Temp)		 
	"""
    if limit == 'lower':
        return 1.36 - 0.136 * (Temp / 100) + 0.0057 * (Temp / 100) * (Temp /
            100)
    if limit == 'upper':
        return 2.0 - 0.2451 * (Temp / 100) + 0.0107 * (Temp / 100) * (Temp /
            100)
