Improved Durability of High-Strength Concrete Due to Autogenous Curing

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Title: Improved Durability of High-Strength Concrete Due to Autogenous Curing

Author(s): S. Weber and H. W. Reinhardt

Publication: Special Publication

Volume: 170

Issue:

Appears on pages(s): 93-122

Keywords: Absorption; chemical analysis; compressive strength; curing; drying shrinkage; high-strength concrete; hydration; lightweight aggregates; pore size distribution; porosity.

Date: 7/1/1997

Abstract:
Curing of concrete is essential for reliable performance of concrete structures. The recommendations concerning curing of high-strength concrete are contradictory. The traditional ways of curing fail in the case of high strength concrete. A higher porosity in the vicinity of edges, microcracks due to self desiccation and shrinkage, and reduced compressive strength affect the durability of high performance concrete. Therefore, another approach is followed which consists of a new idea for supplying curing water in the interior of the concrete, by using lightweight expanded clay aggregates. When a shortage of water in the hydrating cement paste occurs, the water from the lightweight aggregates is transported by capillary suction or by capillary condensation into the smaller pores of the cement paste, thereby permitting continuous hydration. About 25% by volume of the aggregates are lightweight. The improved durability due to the higher degree of hydration, an improved density of the hydrated cement paste, less drying shrinkage and higher com-pressive strength have been shown by experiments. Test results from differen-tial thermal analyses, X-ray diffraction, mercury porosimetry, water absorp-tion, drying shrinkage and compressive strength are presented and compared with normal weight concrete with 100% natural aggregates.