# Pumping

Movement of material underneath the slab or ejection of material from underneath the slab as a result of water pressure. Water accumulated underneath a PCC slab will pressurize when the slab deflects under load.

- Canonical URL: https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/pumping/
- Last updated: 2026-11-01
- Review: reviewed by licensed professional engineers on the previous Pavement Interactive site, where reviewers were not recorded by name

## Description

Movement of material underneath the slab or ejection of material from underneath the slab as a result of water pressure. Water accumulated underneath a PCC slab will pressurize when the slab deflects under load. This pressurized water can do one of the following:

- Move about under the slab.
- Move from underneath one slab to underneath an adjacent slab. This type of movement leads to [faulting](https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/faulting/).
- Move out from underneath the slab to the pavement surface. This results in a slow removal of base, subbase and/or subgrade material from underneath the slab resulting in decreased structural support.

![Pumping in action.](https://pavementinteractive.org/wp-content/uploads/2009/04/Pumping1.jpg)

![Broken slabs.](https://pavementinteractive.org/wp-content/uploads/2009/04/Pumping2.jpg)

![Pumping damage.](https://pavementinteractive.org/wp-content/uploads/2009/04/Pumping3.jpg)

*Figures 1–3.* Pumping in action. Broken slabs. Pumping damage.

Figure 4. Pumping and [faulting](https://pavementinteractive.org/glossary/faulting/) failure mechanism described.

## Problem

Decreased structural support of the slab, which can lead to [linear cracking](https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/linear-cracking/), [corner breaks](https://pavementinteractive.org/glossary/corner-break/) and [faulting](https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/faulting/).

## Possible Causes

Water accumulation underneath the slab. This can be caused by such things as: a high water table, poor drainage, and panel cracks or poor joint seals that allow water to infiltrate the underlying material.

## Repair

First, the pumping area should be repaired with a full depth patch to remove any deteriorated slab areas. Second, consideration should be given to using [dowel bars](https://pavementinteractive.org/reference-desk/pavement-types-and-history/pavement-types/dowel-bar/) to increase [load transfer](https://pavementinteractive.org/reference-desk/pavement-types-and-history/pavement-types/load-transfer/) across any significant transverse joints created by the repair. Third, consideration should be given to stabilizing any slabs adjacent to the pumping area as significant amounts of their underlying base, [subbase](https://pavementinteractive.org/reference-desk/pavement-types-and-history/pavement-types/hma-pavement/) or [subgrade](https://pavementinteractive.org/reference-desk/design/design-parameters/subgrade/) may have been removed by the pumping. Finally, the source of water or cause of poor drainage should be addressed.