The role of materials science after the Mexico City earthquakes in 1985
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I. INTRODUCTION
The Mexico City earthquake of September 1985 killed thousands of people and destroyed many buildings. The effects of the earthquake have motivated many studies by the international scientific community, especially by countries that have urban centers in highseismicity zones. The analysis of the destruction caused by this earthquake has been very valuable for improving design criteria and building codes. In fact, there were two earthquakes, one on September 19 and the other the following day. The first earthquake was larger, and this is the one we refer to in this paper. The strength of the earthquake was 8.1 on the Richter scale. In the sector of Mexico City lying on the basin of the former Lake of Texcoco, the frequency of vibration, with a period of 2 seconds, was particularly deleterious to buildings between 6 and 15 stories in height. After the earthquakes of September 1985, research work was intensified in order to develop new alternatives for safer construction in seismic zones. Increments in safety may be achieved by increasing knowledge of ground structure and movement,1 improving design criteria and reviewing construction practices,2'3 and introducing better structural materials.4 Analyses have been made especially of structures that are particularly vulnerable to earthquakes and indeed were severely damaged in September 1985.2 Localized structural defects have also been reported. Many buildings failed in the joints of structural components,2 some of these failures being related to welds both in reinforcing bars4 and in steel members.5 In this paper we describe research activities on cements and steels, which research was initiated after the 1985 Mexico City earthquake. We will review some evidence obtained by the analysis of reinforcing bars of buildings which collapsed or were severely damaged by 658
http://journals.cambridge.org
J. Mater. Res., Vol. 5, No. 3, Mar 1990
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the earthquake and the aftereffects in the alloy design and fabrication of reinforcing bars with mechanical and metallurgical features especially attractive for earthquake-resistant construction. We shall dedicate an entire section from a research point of view to the field of cements, mortars, and concretes. We will not concentrate on standard cements, but rather will try to show how profitable, both scientifically and economically, basic research in cements can be. In particular we shall describe the properties and uses of polymer-modified cements and will attempt to convince the reader that cement-based materials could play an important role in tomorrow's materials science.
II. CEMENTS AND CEMENTITOUS MATERIALS A. The status of the Mexican cement industry before 1985
The cement industry in the world is a profitable economical and technological activity. Nearly every highly-developed country has an important cement industry. In Mexico the cement industry is a well established and dynamic activity. The total installed production capacity of the country amounts to nearly 33 million tons and th
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