[en] 1 - Nature of physical problem solved: Format: ANISN, DOT, MORSE; Number of groups: The neutron energy range (15 MeV to thermal) is described by 104 groups. The gamma-ray energy range (10 MeV to 0.02 MeV) is described by 22 energy groups. Nuclides: N, O, Al, H, K, Si, Ca, Na, C, and Fe. Origin: For all materials, except C and K, was the Defense Nuclear Agency Working Cross Section Library dated September 1972. The K and C data came from ENDF/B-3. Weighting spectrum: For the neutrons 1/E in the fast range and Maxwellian (300 deg.K) in the thermal range. For the gamma-ray interaction a flat weighting function was used. The DLC-27 library was generated for use in albedo studies of neutrons incident on various types of concrete. It is probably also suitable for neutrons, gamma-rays, or coupled neutron and secondary gamma-ray transport through concrete-like materials. It is a coupled set of neutron and gamma-ray cross sections for the elements N, O, Al, H, K, Si, Ca, Na, C, and Fe. 2 - Method of solution: The AMPX system was utilized to generate the entire coupled library in a single computer run. For all materials except C and K, the basic evaluated data from which the multigroup library was derived was the Defense Nuclear Agency Working Cross Section Library dated September 1972. The K data came from ENDF/B-3. The C was ENDF/B-3 with photon production added to describe a single inelastically and isotropically produced gamma-ray. The neutron energy range (15 MeV to thermal) is described by 104 groups having the same energy structure as used for DLC-9. The gamma-ray energy range (10 MeV to 0.02 MeV) is described by 22 energy groups. For generating the multigroup neutron interaction and gamma-ray production cross sections, the assumption was made that the neutron flux variation (weighting function) was 1/E in the fast range and Maxwellian (300 deg.K) in the thermal range. For the gamma-ray interaction multigroup cross section generation, a flat weighting function was used. The neutron and gamma-ray scattering processes are represented by a P5 Legendre expansion