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Q. What are the important factors affecting permeability? A. Permeability indicates the ability of liquids or gases to flow under pressure through concrete. Low permeability is a principal requirement for concrete exposed outdoors. While the permeability of concrete is primarily determined by the water-cementitious material ratio (w/cm ), paste fraction, and maximum aggregate size, it also significantly influenced by age, consolidation, curing temperature, drying and the inclusion of chemical or supplementary cementitious materials (SCMs). All these factors interdependently influence the interconnected porosity in the cement paste as well as microcracks within the concrete matrix. While air entrainment might be expected to increase the permeability of concrete. However, because air entrainment improves workability, reduces the mixing water required, and reduces bleeding, and therefore the number of continuous bleed channels, the overall effect of air entrainment will usually be reduced permeability. On the other hand, porosity may be exacerbated by external factors such as incomplete consolidation and curing, which may ultimately lead to leakage and reduce permeability and durability. References: SP-1(02); ACI 201.1R-08; ACI PRC-365.1-17; ACI PRC-225-23; ACI PRC-544.11-22; ASTM C1202 Topics in Concrete: Concrete Fundamentals; Durability; Permeability
Q. What are the important factors affecting permeability?
A. Permeability indicates the ability of liquids or gases to flow under pressure through concrete. Low permeability is a principal requirement for concrete exposed outdoors. While the permeability of concrete is primarily determined by the water-cementitious material ratio (w/cm ), paste fraction, and maximum aggregate size, it also significantly influenced by age, consolidation, curing temperature, drying and the inclusion of chemical or supplementary cementitious materials (SCMs). All these factors interdependently influence the interconnected porosity in the cement paste as well as microcracks within the concrete matrix. While air entrainment might be expected to increase the permeability of concrete. However, because air entrainment improves workability, reduces the mixing water required, and reduces bleeding, and therefore the number of continuous bleed channels, the overall effect of air entrainment will usually be reduced permeability. On the other hand, porosity may be exacerbated by external factors such as incomplete consolidation and curing, which may ultimately lead to leakage and reduce permeability and durability.
References: SP-1(02); ACI 201.1R-08; ACI PRC-365.1-17; ACI PRC-225-23; ACI PRC-544.11-22; ASTM C1202
Topics in Concrete: Concrete Fundamentals; Durability; Permeability