Pervious concrete is a stormwater management practice used in the United States, Europe, China, Japan, and many other countries. Yet, the design of pervious concrete mixtures to balance strength and permeability requires more research. Sphere packing models of pervious concrete were used in compressive strength testing simulations using the discrete element method with a cohesive contact law. First, three mixtures with varied water-to-cement (w/c) ratios and porosities were used for model development and validation. Next, an extensive database of simulated compressive strength and tested permeability was created, including 21 porosities at three w/c ratios. Analysis of the database showed for pavement applications where high permeability and strength are required, advised porosity is 0.26-0.30, producing average strengths of 14.4, 11.1, and 7.7 MPa for w/c ratios of 0.25, 0.30, and 0.35. The model can guide the mixture design to meet target performance metrics, save materials and maintenance costs, and extend the pavement life.

This study uses neutron radiography (NR) and visual inspection to quantify water penetration in concrete samples exposed to water pressure on one face. It provides experimental data regarding the impact of mixture proportions on the hydraulic permeability of concrete. Specifically, it illustrates the influence of water-to-cement ratio (w/c), curing duration, entrained air content, and coarse aggregate (CA) size and volume on water transport. In addition, this paper quantifies the impact of permeability-reducing admixtures (PRAs) on water transport in concrete. It was observed that decreasing the w/c and/or increasing the curing duration reduced the fluid transport. Liquid and powder PRAs efficiently reduced fluid transport in concrete without impacting the compressive strength. The liquid PRA showed more consistent results, likely due to better dispersion than the powder PRA. Fluid ingress in concrete samples appears to increase with entrained air content due to a lower degree of saturation (DOS) at the start of the test. Increasing the CA volume fraction or decreasing the CA size will increase the fluid transport in concrete due to an increase in the connectivity of the interfacial transition zone. The influence of entrained air content, curing duration, CA volume fraction, and CA size was less noticeable on mixtures with PRA due to the higher density and low permeability of these samples compared to control samples.

This study clarifies the effects of moisture (expressed as percentage saturation degree of permeable pore voids: PSD) on water ingress properties of concrete and establishes a region where PSD does not affect the quantitative water absorption. Experimental measurements and FEM simulation results for ordinary Portland cement (OPC) concrete pre-conditioned to equilibrium moisture formed plateaus between 21-58% PSD. Non-continuous finer capillary pores (ϕ10 nm [3.937 x 10-4 mil, thou] to ϕ100 nm [3.937 x 10-3 mil, thou]) constitute the empty pores within the plateau region before tests. Water sorptivity of OPC and GGBFS cement concrete blocks at several degrees of surface moisture with internal moisture gradients validate the existence of the plateau within the PSD range. Measuring short-term water absorption within this plateau region eliminates the effects of initial surface moisture content on the measured properties and evaluates the continuity and connectivity of pores, which is the major indicator of the durability of concrete.

Self-healing is a process by which concrete is able to recover its properties after the appearance of cracks, which can improve mechanical properties and durability, and reduce the permeability of concrete. Self-healing materials can be incorporated into concrete to contribute to crack closure. This study aims to evaluate the influence of crystalline admixtures and silica fume on the self-healing of concrete cracks. The rapid chloride penetration test was performed on cracked and uncracked samples, from which it was possible to estimate the service life of concretes. The concretes were characterized by tests of compressive strength and water absorption by capillarity. The use of crystalline admixtures did not have a negative influence on concrete properties but did not favor the chloride penetration resistance. The concrete with silica fume showed the lowest charge passed and highest values of estimated service life.

The durability performance of geopolymer concrete against severe environmental conditions is important for implementing geopolymer binders as alternatives to ordinary portland cement (OPC). In this experimental investigation, the impact of adding graphene on the durability characteristics of geopolymer concrete was examined. Graphene was added at 0.5% by weight of aluminosilicate precursors in geopolymer concrete. Permeability, salt ponding, capillary sorptivity, and immersion in chemical agents were performed to assess the durability characteristics of geopolymer concrete without and with graphene, which were also compared with the durability characteristics of OPC concrete without and with graphene. It was found that the addition of graphene in geopolymer concrete reduced the permeable voids by 12% and water absorption by 9%, and improved the resistance against chloride penetration and sulfuric acid exposure. The compressive strength of geopolymer concrete increased by 20% with the addition of graphene. Also, an approximately 70% reduction in the initial and final rate of water absorption was observed in geopolymer concrete with the addition of graphene.