Durability of High-Performance Cement-Based Materials
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DURABILITY OF HIGH-PERFORMANCE CEMENT-BASED MATERIALS LESLIE STRUBLE*, EDWARD GARBOCZI**, AND JAMES CLIFTON** *University of Illinois, 205 N. Mathews, Urbana, IL 61801 "**NationalInstitute of Standards and Technology, Gaithersburg, MD 20899 ABSTRACT There is considerable research now underway on high-performance cement-based materials, in particular on issues of processing, microstructure, strength, and related properties. However, very little research has been undertaken regarding the durability, or service performance, of these materials. Therefore the durability of high-performance cement-based materials can only be inferred from the service performance of ordinary materials or from a basic understanding of the factors affecting service performance. In this paper we review what is known about the durability of fiber reinforced concrete, high performance concrete, DSP, and MDE Durability is discussed from the standpoint of general issues - fluid permeability, ionic diffusivity, and pore fluid composition. Much research is needed in order to predict or improve the durability of high performance cement-based materials. INTRODUCTION Portland cement concrete is so widely used as a construction material that it is difficult to imagine modem life without it. Concrete is inexpensive, versatile, durable, and fairly strong in compression (typically 20-30 MPa). However, concrete is quite brittle; like any brittle material, its tensile strength is considerably lower than its compressive strength (about one-tenth). This brittleness seriously limits structural design and use of concrete. Furthermore, it has been shown recently that concrete strength may be substantially improved by incorporating basic knowledge gained through materials science concerning the relationships between processing, microstructure, and properties. Therefore considerable research is now underway on high-performance cement-based materi-
als that provide increased toughness and higher strength. Much of this research is being carried out through the National Science Foundation Science and Technology Center for
Advanced Cement Based Materials' [1]. Thus far, the focus of research has been on strength and toughness, with little research on durability (i.e., long term performance in the intended service environment). The object of this paper is to assess the durability of these new, high-performance cement-based materials. In assessing durability, we have chosen to concentrate on two fundamental aspects of durability, which dominate the durability of all cement based materials, transport processes and the composition of pore fluid. The materials that are the subject of this paper fall into two categories, construction materials and specialty materials (ceramic materials synthesized at low temperatures via cement hydration reactions). The construction materials are fiber reinforced concrete and high performance concrete, and the specialty materials are DSP (for densified with small particles) and MDF (for macro defect free). Levels of strength and fracture
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