The design of a project determines the performance requirements of the concrete in terms of the compressive strength needed and level of durability to withstand weather conditions. High-strength concrete is defined as having a compressive strength of 6,000 psi (40 MPa) or greater. The last couple of decades have seen a demand for stronger concrete. The Portland Cement Association reports that two buildings in Seattle, Washington were constructed using concrete that has a compressive strength of 19,000 psi.
In order to design high-strength concrete, research and time is put into optimizing and controlling each component of the mix. The concrete needs to have a lower water-cementitious material (W/C) ratio that is somewhere in the range of 0.23 to 0.35, and usually requires a superplasticizer admixture.
Moreover the high-strength concrete requires an aggregate that is durable and strong and is the optimal size and coarseness to ensure the ideal bond with the cement paste. Generally the mix will contain a mineral admixture such as silica fume or fly ash (Class C or F) to prevent free calcium hydroxide crystals from forming that can affect the strength of the concrete.
There are many kinds of projects that require high-strength concrete such as the construction of long-span bridges and decks or projects that have unique architectural features. Without high-strength concrete, it would not be possible to construct the super tall skyscrapers of today. Another advantage to the stronger concrete is that columns can be made smaller but still be as supportive while offering more usable interior space.
Conco is taking a more active role in the Portland area with our expansion of high-quality commercial concrete services. We bring our years of experience delivering dependable services since 1959, and a vast portfolio of noteworthy and large-scale projects from throughout the Western U.S. Our work includes commercial, industrial, educational and multi-residential construction as well as public works projects.