Optimizing Cementious Content in Concrete Mixtures for Required Performance





INTRODUCTION
Concrete is the most commonly used material for all types of construction, and cement is a primary component. The cement content of a mixture is commonly perceived to control concrete strength. Based on this perception, a minimum cement content is often specified that may exceed the amount needed to achieve the desired strength and durability. This excess amount has a negative impact on cost and the environment for the following reasons:


Cement is the most expensive component in concrete Cement contributes about 80 percent of the carbon dioxide (CO

) burden of a concrete mixture

Cement production emits approximately 5 percent of global CO

and consumes about 5 percent of global energy

Previous studies suggest that increasing cement content in a mixture does not necessarily contribute to increasing strength (Wasserman et al. 2009, Popovics 1990). In addition, the high cement content will cause the mixture to become sticky and may lead to increased risk of shrinkage and cracking problems. Therefore, cement content should be balanced to achieve the required performance while minimizing risk of these problems. Despite the published studies and documentation, there continues to be a misconception that more cement in a mixture design means a better performing mixture.


Increasing cement content can have a negative impact on performance and durability by increasing shrinkage and the consequent risk of cracking. Although workability is increased by increasing cement content, it causes higher internal temperatures in the concrete during the finishing and curing processes.


Reducing excess cement content in concrete mixtures helps to reduce costs as well as the environmental and energy impacts associated with making cement.

This study investigates the effects of changing cement content and paste volume on strength and durability.


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