QAQC in Construction

1. Drying Shrinkage Concrete by nature is a porous material. This means that when it is curing, the water in the concrete takes up space. As concrete hardens, it loses its moisture through evaporation resulting in empty capillary pores and a slightly smaller shape. This process is known as drying shrinkage. Since concrete is very rigid, this shrinkage causes an increase in tensile stress, which may lead to, cracking, internal warping, or external deflection. Concrete cracks when the drying shrinkage stresses exceed the tensile strength of the concrete. The spacing and size of cracks depend on the amount of shrinkage, degree of restraint, and amount and type of reinforcement. Drying shrinkage is the number one reason for cracks in concrete. 2. Lack of / improper use of control joints Control joints are most commonly installed in slab-on-grade concrete that is used in places such as driveways, pavements, house slabs, basement floors, and industrial spaces.  Control joints are general...

Cementitious Materials in Concrete Define and classify various cementitious materials; Understand the effects of cement fineness on water demand and concrete strength properties Recognize the importance of controlling the heat of hydration in concrete; and Identify the types of blended cement and the performance benefits of each for certain applications. List the standard tests used to determine properties of hydraulic cement; Understand why the water demand changes when using fly ash and pozzolans; Discuss the differences in strength gain for concretes with and without pozzolan replacement of cement; and Recognize the advantages of using ground granulated blast furnace slag and silica fume in concrete. Explain the synergistic effects of using multiple Supplementary Cementitious Materials (SCMs) in a concrete mixture. Recall methodologies for evaluating ternary and quaternary blends of materials for use in concrete. Describe considerations for construction using ternary and quaternary ...