Foundation Damage due to Deterioration of Brick

Brick is considered here, as it is most common foundation materials and used over the world extensively; but actually not as broken chips in concrete. Once it was very common to have brick foundation and some of these foundations are also still serving as foundation of many hysterical buildings and also some are still using as dwelling structure.

Now-a-days new structures are also building when this construction material is available and structure is also light and less important. Considering environmental issue, now we are gradually trying to replace brick with other materials and also to have lighter structure it is replaced by hollow block made of many recycled materials.

Building bricks are specified in ASTM C62, which deals with bricks that are used in non-structural and structural brick works and whose appearance is not important factor.

“Glossary of Building and Civil Engineering Term”-BS6100 defines clay engineering bricks as clay units that are fired to produce a strong and dense semi-vitreous body which comply with most important engineering requirement like brick-compressive strength and water absorption.

The structural brick work use these two properties in both strength and durability point of view. Bricks are defines in UK as Class A and Class B.

The typical requirements of strength and water absorption of these two classes of bricks are:

Brick classes discussed in last part according to BS 6100 are applicable where acid resistance; low water absorption and strength are the main criteria of construction. But there have other observation that-

If water absorption is less than 12%, difficulties arise to derive proper bond between brick and mortar.

Another classification of bricks is also available and very common in our usual practice. These are

a. First class

b. Second class

c. Third class

d. Kiln rejects

We will discuss about all these classification in our upcoming posts. Here we will discuss about only first class and second class bricks.

In brief first class brick have uniform shape and size and have minimum crushing strength 10.5 N/mm². Of other important properties, water absorption should not be more than 15 percent of their dry weight.

Regarding second class brick, it has crushing strength 7 N/mm² (minimum) and water absorption is not more than 22%.

Dear reader we have discussed about strength and water absorption of different types of bricks let us know about how disruption occurs in brick foundation due to water absorption?

The water remains in brick, when get frozen produce frost damage that materializes by splitting or exfoliation of outside surface or parallel to it. Sometimes cracks become large and continue which results total disruption of bricks.

The severity of damage depends on other environmental conditions like

a. Moisture

b. Speed of freezing

c. No. of freezing-thawing cycles

Regarding frost resistance of brick we can include; it depends on

a. pore distribution

b. Water absorption

c. Strength

We have discussed about above material properties in earlier posts and as well in first portion of this topic. We hope you have an overall idea about frost deterioration/damage of foundation and foundation elements constructed with bricks.

ASTM Specification for Crushed Cement Concrete

Now-a-days we are worried about waste product and their safe disposal. Like other products concrete also becomes waste like

-old building

-unserviceable building

-serviceable building but owner need to construct better or more storied structure

-they may also come from other concrete structure like pavement made of concrete etc.

Our concern is not the source of concrete as waste; but is recycling them further as concrete constituents like coarse aggregates. We unconsciously use this concrete wastes for land development or other less productive work.

While specifying coarse aggregates ASTM C-33 provides following materials as coarse aggregates

a. Gravel

b. Crushed gravel

c. Crushed stone

d. Blast furnace slag cooled in air

e. Crushed hydraulic cement concrete

f. And a combinations of them are also permitted according to specification

We will discuss about classification of coarse aggregate according to same specification in the next posts.

ASTM doesn’t provide specific specification but recommended to take some precautions while using such concrete as coarse aggregate.

Note-6 of ASTM C33-03:

There have some satisfactory application of crushed hydraulic cement, but need additional precautions as follows:

a. Excess water is required as crushed aggregate are harsh in texture

b. May have such constituent that can induce

1. Alkali-aggregate reaction to new concrete

2. Sulfate attack to new concrete

c. Through their pores it may bring

1. Sulfate to new concrete

2. Chloride to new concrete

3. Organic materials to new concrete

d. When aggregate are derived from partially deteriorated concrete it may

1. Reduce freezing-thawing resistance

2. Negative influence on air void properties

3. Degrade or disintegrate during

-handling

-mixing

-placing

Foundation Damage due to Insect Attack

Another cause of conventional wood foundation damage is insect attack. They can attack foundations usually above ground level. The insects that are responsible for maximum damage are

a. Wood boring insect

b. Carpenter ants

In the last post we have leant about rotting damage of foundation. Like rotting these are also related to ambient temperature but less dependent upon moisture content within timber. This damage done by insects is more significant in wet or unseasoned timber member.

In dry timber member, the infestation is unlikely to occur. The word ‘infestation’ means presence of many pest organisms on surface of host (here timber) or in the soil or anything which remains in contact with host.

The capability of a timber member to fight with organisms resulting decay within it is called natural durability. Some timber species have such natural durability and can safely be used. But in case of species that posses less durability, have to be treated with preservative and require good practice both in design and construction to resist degradation discussed in this and last posts.

Within a country, some parts are less exposed to insect attacks than others. Most boring insects become active between (32⁰F and 85⁰F). Wood which is damaged by fungus rotting is readily vulnerable to be attacked by such insects. In case of poles and caissons at beaches, identical conditions are also observed.

Foundation Damage Due to Erosion of Natural Rock

Foundation is often rest on natural rock. The rocks are found to be eroded due to different erosion agent of ambient environment. Dear reader we have discussed about formation of soil, erosion of rocks, both chemical and physical properties of such soil.

When foundation of a structure rests on rock, the stability and subsequent damage of foundation depends on strength and durability of rock. Some rocks have greater strength but posses lesser durability and durability is very important factor in respect to longevity of foundation and structure over it.

The strength and durability of rock depend on distribution and amount of weaker and smaller mineral within it. When these minerals get worn out, everything is also broken down or dissolved which results no interaction between stronger minerals that once connected to each other by strong mineral bond.

These wearing actions left nothing but a stone that is merely composed of conglomeration of loosely connected particles. The deterioration accelerates when foundation surface is damaged, in addition, by following:

a. Frost action

b. Salt washing and like other process

Now how much time is required to take place such erosion process?

The usual duration is long. But some special rocks produce problem when exposed to erosion; these are

a. Limestone

b. Sandstone

c. Shale etc.

In our next post we will learn about foundation damage due to deterioration of bricks used as foundation material. Till then good bye.