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Twenty eight days is a long wait to determine if desired strengths are going to be obtained, so three-day and seven-day strengths can be useful to predict the ultimate 28-day compressive strength of the concrete. A 25% strength gain between 7 and 28 days is often observed with 100% OPC (ordinary Portland cement) mixtures, and between 25% and 40 ...
The durability design of reinforced concrete structures has been recently introduced in national and international regulations. It is required that structures are designed to preserve their characteristics during the service life, avoiding premature failure and the need of extraordinary maintenance and restoration works.
The early strength of the concrete can be increased if it is kept damp during the curing process. Minimizing stress prior to curing minimizes cracking. High-early-strength concrete is designed to hydrate faster, often by increased use of cement that increases shrinkage and cracking. The strength of concrete changes (increases) for up to three ...
High-performance concrete (HPC) is a relatively new term for concrete that conforms to a set of standards above those of the most common applications, but not limited to strength. While all high-strength concrete is also high-performance, not all high-performance concrete is high-strength.
Durability is the ability of a physical product to remain functional, without requiring excessive maintenance or repair, when faced with the challenges of normal operation over its design lifetime. [ 1 ] : 5 There are several measures of durability in use, including years of life, hours of use, and number of operational cycles. [ 2 ]
The characteristic strength is defined as the strength of the concrete below which not more than 5% of the test results are expected to fall. [16] For design purposes, this compressive strength value is restricted by dividing with a factor of safety, whose value depends on the design philosophy used.
Fibers are added for long term durability of concrete. Glass [14] and polyester [15] decompose in alkaline condition of concrete and various additives and surface treatment of concrete. The High Speed 1 tunnel linings incorporated concrete containing 1 kg/m 3 or more of polypropylene fibers, of diameter 18 & 32 μm, giving the benefits noted ...
Concrete spalling from the ceiling of an office unit (interior) in Singapore, possibly due to rebar corrosion. Reinforced concrete can fail due to inadequate strength, leading to mechanical failure, or due to a reduction in its durability. Corrosion and freeze/thaw cycles may damage poorly designed or constructed reinforced concrete.