Preliminary geologic and engineering assessment of the pyroclastic deposits in the central part of Harrat Rahat

Abstract EN

Cenozoic volcanic rocks cover vast areas in the Arabian Shield consisting mainly of lava flows associated with pyroclastic deposits namely scoria and cinders.

Markets for pyroclastics include aggregate for road construction and surfacing, lightweight concrete and light weight-heat-insulating building blocks.

These pyroclastic deposits are also the main source for the natural pozzolanic material in the Kingdom.

The purpose of this investigation is to survey the central part of Harrat Rahat and locate the most suitable sources of these deposits.

A reconnaissance survey was performed on over thirty volcanic cones in the specified area and four cinder cones that seem to have suitable scoria deposits both from the economic and engineering points of views, were selected.

The preliminary investigations on these sites suggest that Jabal Halat ash Shaykh show the best scoria occurrence in the investigated area.

Jabal Al Hala and Jabal as Sahiliyah have suitable quantities of scoria while Jabal Suwah has limited scoria resources.

The geology and geomorphology of the four sites are presented in this work.

Some geological and geomorphological observations during this survey may help in identifying other craters that may make good sources of scoria deposits in other areas.

Results of preliminary laboratory investigations indicate that the material could be economically utilized as lightweight aggregate, cement additive and as heat insulating material.

The measured parameters are compared with the specifications required by the ASTM and other designations.

The results of the strength activity index and alkali silica reaction tests were not encouraging, due to a technical problem, and the tests will be repeated on finer material.

Detailed economic and engineering investigations of the scoria deposits and concrete mixes made out of these materials are now in progress.