T201 Cultural Geology and Heritage Stone: Use, Petrology, Quarrying, Engineering Properties, and Other Aspects of Stone Used for Buildings, Monuments, Sculpture, or Otherwise Relating to the Interface of Stone with Human Culture Past and Present

Tuesday, 6 November 2018
1:30 PM - 5:30 PM
Room 133

A STUDY ON THE SOUNDNESS OF PARENT ROCKS IN SRI LANKA

Paper number: T201-5
Program: Technical Sessions
Time: 2:30 PM – 2:50 PM

Authors

Abstract

Geologically nine tenth of Sri Lanka is made up of high grade metamorphic rocks of Precambrian age. The remaining rocks are sedimentary rocks of predominantly Miocene age in the north-west with some Jurassic sediments and scattered igneous intrusions through the regional metamorphic rocks (Cooray,1984). Studies on the engineering properties of different rock types provide a prior knowledge on the quality of such rock types as well as potential locations of suitable sources for the industry. The property “soundness” of a material measures the tendency to split into pieces similar to physical weathering during expansion and contraction processes within it. This soundness varies according to the type of minerals in a rock and its’ origin. If rocks are using for aggregates for concrete or other applications the estimation of their soundness is necessary. With the aim of that, fresh rock samples of different rock types were collected from quarries and exposed rocks in different localities in Sri Lanka to study the variation of soundness property in different rock aggregates. Samples were tested in the geotechnical engineering laboratory using sodium sulfate solution according to the Standard Method ASTM C88-99a (1999)[1]. Accordingly charnockite/charnockitic gneiss shows the lowest loss of weight percentage (less than 1.9%) as the highly sound rock for aggregates. Miocene limestone is the highly unfavorable rock (more than 25%). Results for other rocks are given in the Table.

Table. Results of laboratory test for soundness of different rock types in Sri Lanka.

Rock type

Soundness value/ or Range of values %

Number of samples tested

Metamorphic Rocks

Chranockite/ charnockitic gneiss

0.24-1.89

27

Charnockitic garnet/ hornblende/

biotite gneiss

0.34-2.82

7

Amphibolite

0.39

1

Microcline/ Granitic gneiss

0.47-1.1

3

Garnet/ biotite gneiss

2.29-9.5

5

Quartzofeldspathic gneiss

2.34-3.37

3

Marble

2.5-5.2

3

Hornblende biotite gneiss/

migmatite

3.5-6.5

3

Quartzite

5.0-6.88

3

Intrusive rocks

Pink granite

0.75

1

Pegmatite

3.79

1

Sedimentary rocks

Miocene limestone

25-30

3

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-315446

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