Clogging in permeable concrete: A review

TLDR: The clogging mechanism and current mitigating strategies are reviewed in order to inform future research needs and to develop permeable concrete that can be poured on-site, which produces a pore structure with significantly reduced tortuosity.

About: This article is published in Journal of Environmental Management.The article was published on 2017-05-15 and is currently open access. It has received 146 citations till now. The article focuses on the topics: Pervious concrete & Clogging.

Figures

Fig. 4. Correlation between permeability and porosity for a wide range of permeable concretes reported in the literature.

Fig. 5. Permeable concrete (a) as cast and (b) and rotated, showing the bottom is completely blocked by paste drain down, due to excessive cement paste content, w/c ratio and/or compaction. The sample is a 100 mm cube.

Fig. 1. Cross-section of a typical permeable concrete with porosity of 22%.

Fig. 2. Schematic cross-section of a typical sustainable urban drainage system incorporating a

Fig. 7. Schematic showing the pathway with a tortuosity of 1 and various pathways through

Fig. 6. Schematics showing how different sized particles are likely to clog permeable concrete: a) large particles relative to the pore size are predominantly caught at the top surface or migrate only a short distance into the concrete; and b) fine particles migrate deeper into the permeable concrete where they cause clogging.

Frequently asked questions

Q1. What are the contributions mentioned in the paper "Clogging in permeable concrete: a review" ?

This paper reviews the clogging mechanism and current mitigating strategies in order to inform future research needs. The pore structure of permeable concrete and characteristics of flowing particulates influence clogging, which occurs when particles build-up and block connected porosity. The potential for clogging is related to the tortuosity of the connected porosity, with greater tortuosity resulting in increased potential for clogging. 

Q2. What are the main uses of retarders?

Retarders are used to extend workability by decreasing the rate of cement hydration and reduce excessive heat of hydration during early ages. 

Q3. What is the definition of permeable concrete?

Permeable concrete is characterised by highly interconnected porosity, typically in the range of15–35% vol. that allows water to flow rapidly through the pore structure. 

Q4. What is the way to clean a clogged pavement?

When pavements are clogged with coarse sand particles that are mainly deposited on the surface, vacuum sweeping, pressure washing or a combination improves permeability. 

Q5. What was the effect of sand on permeability?

Combination of silty clay and sand caused the highest reductions in permeability, with complete clogging after a small number of cycles. 

Q6. What are the main reasons why permeable concrete pavements are more susceptible to damage from improper?

Permeable concrete pavements are more susceptible to damage from improper curing thanconventional concrete pavements because of the high surface area and open void structure. 

Q7. What is the important factor influencing permeability of traffic lanes?

For instance, traffic lanes have lowerinfiltration capacity compared to parking spaces because of the greater amount of sediments that typically falls on traffic lanes (Henderson and Tighe 2012). 

Q8. How many cycles to failure was found for clogged specimens?

The average number of freezethaw cycles to failure was 93 for clogged specimens compared to 180 for unclogged specimens, and 80 for saturated specimens compared to 193 for unsaturated specimens. 

Q9. What is the reason why Henderson and Tighe (2011) found that it is extremely difficult to restore?

Henderson and Tighe (2011) also observed that it is extremely difficult to restore permeability to initial values for pavements that had low initial infiltration rates (due to poor mix design and/or improper construction). 

Q10. What is the main requirement of the mix design?

Various mix proportioning methods have been recommended, and the most important requirement is to provide sufficient cement paste to bind aggregates to achieve the required strength and high void content. 

Q11. What is the way to reduce the porosity of aggregates?

Blending aggregates of different sizes improves mechanical properties, but this is not recommended for permeable concrete because it reduces porosity and infiltration rates (Schaefer et al., 2006). 

Q12. What is the effect of maintenance methods on permeable concrete?

Schaefer et al. (2011) observed that maintenance methods were more effective on high porosity samples, but had negligible effect on specimens with <15% porosity. 

Q13. Why are permeable concrete pavements not finished?

Permeable concrete pavements are not finished in the same way as normal concrete because floating and trowelling operations close surface voids (Tennis et al., 2004; ACI, 2010; Obla, 2010). 

Q14. How did they measure the porosity of permeable concrete?

Manahiloh et al. (2012) measured porosity profiles of permeable concrete cores using X-ray tomography to assess the effect of age on the nature and extent of clogging.