Relationship between Porosity & Strength of Concrete

Porosity can be defined as the total volume of the overall volume of the pores larger than the gel pores, expressed as a percentage of the overall volume of the cement paste. The effects of pores smaller than 20mm in diameter were found to be negligible.

Porosity Factors Affecting Concrete Strength

The strength of concrete is fundamentally a function of the volume of voids in it. The strength of concrete is influenced by

• The volume of all the voids in the concrete
• Entrapped Air
• Capillary Pores
• Gel Pores
• Entrained Air

Relationship between Compressive Strength and Porosity

The relation between the compressive strength and the porosity is as follows.

Fig.1. Comparison of predicted and observed compressive strength ( Image Courtesy: Influence of porosity on compressive and tensile strength of cement mortar Xudong Chen, Shengxing Wu, Jikai Zhou College of Civil and Transportation Engineering, Hohai University, Nanjing, China

The relation between the Flexural strength and the porosity is as follows.

Fig.2. Comparison of predicted and observed Flexural Strength ( Image Courtesy: Influence of porosity on compressive and tensile strength of cement mortar Xudong Chen, Shengxing Wu, Jikai Zhou College of Civil and Transportation Engineering, Hohai University, Nanjing, China

The relation between the Splitting Tensile strength and the porosity is as follows.

Fig.3. Comparison of predicted and observed Splitting Tensile strength ( Image Courtesy: Influence of porosity on compressive and tensile strength of cement mortar Xudong Chen, Shengxing Wu, Jikai Zhou College of Civil and Transportation Engineering, Hohai University, Nanjing, China

Higher the porosity, lower is the compressive strength

Porosity of Aggregates on Concrete Strength

The porosity of the aggregate influences the

• Bond between the cement paste and the aggregate 
• Workability of the Fresh Concrete
• Strength of the Concrete