Concrete Handling

Source: Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA Concrete consists of two phases, a cement paste phase comprised of cement, water, and air, and an aggregate phase comprised of coarse and fine aggregates. There are two key considerations when designing a concrete mix. First, the concrete must be workable and easy to cast in the forms in its fresh condition, even when the forms are packed with steel reinforcement. In this condition, it is the...

Source: Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA In a previous laboratory focused on concrete in compression, we observed that concrete can withstand very large stresses under uniaxial compressive forces. However, the failures observed were not compressive failures but failures along shear planes where maximum tensile forces occur. Thus, it is important to understand the behavior of concrete in tension and particularly its maximum strength...

Source: Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA There are two distinct stages in a construction project involving concrete. The first stage involves batching, transporting, and casting fresh concrete. At this stage, the material is viscous, and the workability and finishability are the key performance criteria. The second stage occurs when the hydration process begins shortly after the concrete is placed in the form, and the concrete will...

Source: Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA Concrete and asphalt are by far the most common construction materials used today. Concrete is a composite material consisting of cement, water, air, coarse aggregate, and fine aggregates. Fine aggregates are typically sands and coarse aggregates are natural or crushed rocks. Chemical admixtures to modify certain specific properties are also commonly used (i.e., superplasticizers to make the...

Source: Diego Reinero & Jay Van Bavel—New York University Whether it's refraining from having a second serving of ice cream, studying instead of attending a fun party, or deciding to put money away in a savings account, sacrificing short-term outcomes in favor of long-term outcomes (i.e., delaying gratification) is a central tenant of self-control. When people apply self control, they engage numerous psychological processes to help them achieve their goal. These self-regulatory processes...