Analysis of architectural concrete of Bahá'í Temple

The Bahá'í House of Worship is one of the most famous exposed aggregate concrete structures in the world. The stairs at the main entry of the building were cast and placed in 1942 and has combated the weathering elements of Wilmette, Ill., a northern Chicago suburb, for more than 50 years. The stairs were replaced in 1989 due to deterioration. These replacement stairs, however, have exhibited characteristics of accelerated deterioration. This research project addresses the historical references of the original concrete work done, past testing and investigations of the concrete structure, and a performance evaluation by mechanical and microstructural tests of both the 1942 original concrete and 1989 restoration concrete. It is found that one of the causes of the deterioration of the 1989 restoration concrete is a weak paste matrix. The cause of deterioration of the 1942 original concrete is a weak aggregate-matrix interface.