The purpose of this assignment is to give a summary of the article entitled Advances in Materials Applied in Civil Engineering (Flaga, 2000). The first portion of the report is dedicated to the development of civil engineering as a field and the changing availability of materials throughout. Flaga (2000) notes that brittle materials such as stone and brick dominated civil engineering in Europe between the era of Ancient Egypt and the First Industrial Revolution. The problem with such brittle materials is that they have a low tensile bending strength, which means that they cannot be effectively used for many horizontal elements. This began to change when arches and curvilinear vaults developed into segmental approaches to building horizontal elements (Flaga, 2000). Still, the early age of civil engineering was mainly limited by the types of materials available and their ability to be developed into certain designs.
The basic construction material of the 19th and 20th century, however, was steel. Steel and cement are both commonly used in construction today, and are a lot more flexible in their use than these earlier materials (Flaga, 2000). They have a high tensile strength, which means they are more useful for horizontal elements, and have a high compressive strength. Steel has also been developed continually over this period to have more desirable properties. Some examples of steel constructions are given in the article, including George Washington Bridge and the Tagus Bridge. Suspension bridges such as those listed continue to be built to this day, but they are reaching the limits of civil engineering and there is a need to develop new materials that are more appropriate for the engineering challenges of the 21st century and beyond (Flaga, 2000).
Flaga (2000) suggests that the carbon fiber reinforced polymer (CFRP) is the material that is most likely to replace this. Until now, CFRP has been mainly used in space and aviation. The article gives some of the basic properties of CFRP, including how it is made: it is a composition of very thin carbon fibers that have been embedded in a solid polyester resin (Flaga, 2000). The first use of this material in strengthening a bridge structure is in the Ibach Bridge of Switzerland, a process that began in 1991. It forms 55% of the laminated content of this bridge, and overall provides a tensile strength of 1900 MPa with a longitudinal elastic modulus of 129 GPa (Flaga, 2000). CFRP stay cables are extremely effective even in the face of high resistance to axial tension, despite the fact that the elastic modulus of these cables is similar to steel cables used in previous civil engineering projects.
Concrete is discussed again in some detail, but Flaga (2000) focuses on the structural material called high performance concrete, or HPC. This is created by adding silica fume and superplasticisers to concrete. This type of concrete has a high compression strength, a greater brittleness than standard concrete, and a lower porosity and absorbability than standard forms (Flaga, 2000). It also has an increased adhesion to reinforcements by up to 40% and a significant reduction in creeping. The article ends by discussing the other advanced elements that are often used in concrete-based engineering, including the addition of glass, carbon, and aramid in tendons. These can be used as wires and they have a low density compared with steel, making them much lighter for the same strength value. The SIFCON method is also discussed in some length. This process is used to repair damage to concrete pavements and roads and increase the compressive strength of concrete when added to holes in existing concrete structures.
- Flaga, K. (2000). Advances in materials applied in civil engineering. Journal of Materials Processing Technology, 106(1), 173–183.