Nonconventional Concrete Technologies Renewal of the Highway Infrastructure (1997) / Chapter Skim
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5 Systems Approach to Concrete Technology
5 Systems Approach to Concrete Technology
Pages 74-85
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From page 74... ...
structures. The committee has concluded that major advances in the development and application of nonconventional concrete technologies require the use of a MSE systems approach.
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From page 75... ...
On the nanometer length scale, the inherent lower limit of the size of atoms means that structure and processes would have to be considered ctifferently-from larger length scales, in which matter can be regarded as continuous. On the molecular level, particles grow by various random processes that generate fractal structures.
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From page 76... ...
One special advantage of concrete relative to other manufactured materials is the longer length of time required for processing (i.e., initial mixing through transport to pouring) , which offers ample opportunity to adjust material composition and mixing conditions.
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From page 77... ...
The concept of model-based design within the context of a systems approach is not a new concept. It has been slowly evolving as computational power increases and is being increasingly appliecl to the fabrication of "high-tech" systems, including weapons systems, aircraft, and automobiles (NRC, 1988, 1989, 1993, 1995a, 1995c)
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From page 78... ...
Empirical knowledge is generally insufficient because it is not possible to perform empirical experiments on the full system uncler every condition. But understanding, for example, how chlorides penetrate the concrete and attack the reinforcement fundamentally allows one to combine higher-order effects computationally in model-based performance and reliability assessments, including requirements for earthquake zones, fire resistance, lightweight applications, etc.
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From page 79... ...
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From page 80... ...
This implies that far more extensive research into the theoretical interrelationship among synthesis and processing, structure and composition, properties, and performance of concrete materials is required (Figure 1-11. Second, given more extensive materials and process knowledge, better mechanistic computational models are needed to understand the behavior of the materials and structures during fabrication and in-service.
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From page 81... ...
Fundamental Issues and Computational Models If one assumes that the required funciamental materials information clescribec3 above is available, the next issue is how to use this information to optimize the fabrication and manufacturing processes and to enhance the properties and performance of the final structure. Once again, optimization requires the clevelopment of mechanistic models and computational tools that span all length scales, from atomic/molecular to macroscopic.
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From page 82... ...
Modern integrated sensors can be procluced in a modern semiconductor device fabrication facility at a per-device incremental cost of as low as a few cents. Low cost produces the lion arithmetic operations per second.
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From page 83... ...
structure and thereby potentially reduce total life-cycle costs. For this approach to succeed, the costs of structure must not be viewed just from the perspective of the lowest cost of original construction.
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permit the accumulation of data that couIc! be fed back into the model-based design methoclology as well as allow cost-effective, localized repairs that would minimize maintenance costs while maximizing in-service time by eliminating routine preventative maintenance.
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From page 85... ...
complex issue, since the "systems approach" paradigm requires that the cliscussecl technology enablers be considerec! over all length scales for the cement, the concrete, ancl then the structure itself.
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