30. Lime-pozzolana as an alternative cementing material

Portland cement is in short supply in many developing countries, but can be replaced in many applications by lime-pozzolana mixture. A project to manufacture lime-pozzolana mixture using as pozzo-lana a volcanic ash from Mt. Meru in Northern Tanzania is described. Suitable mix proportions for mortars, plasters and blockmaking were derived from laboratory and field testing. Significant cost saving as well as increased local employment and reduction of cement imports can be achieved.

1. Portland cement is today considered an essential material for all construction programmes in developing countries: few, if any, projects are considered which do not depend to some extent on cement. Yet in the majority of developing countries the indiginous supply of cement is considerably less than the demand. Essential projects are frequently held up for lack of it; and local supplies have to be supplemented by imports, often at a huge cost in foreign exchange and transportation. Although rapid progress has been made in expanding the local supply by building new cement factories, the capital cost of such factories is very considerable, and the increase in cement production has not kept pace with the increase in demand. Many engineers in third world countries have therefore begun to consider alternative ways of building, by which the need for Portland cement is reduced or eliminated.