Rock Pozzolana

About 1.2 square kilometer underlain deposit of hard rock at Maddhapara of district Dinajpur, may be a versatile source of pozzolana in Bangladesh. At present, the mine is designed to produce boulders and aggregates from the underground reserve to meet the requirement of flood control, construction of coastal and town protection embankment, construction and maintenance of bridges, roads and highways, embankment, river training, railway ballast, high rise buildings, decoration tiles and other heavy duty construction works. The rock deposit is overlain by about 140m of unconsolidated sediments. Below this, the basement is the Archean era and subdivided into the kaolinized granodiorite, the weathered granodiorite and fresh granodiorite. Dykes of micro-granodiorite (Fig. 1), fine grained silicified whitish granite (Fig. 2) and pegmatite is thinly inserted in the basement. In the upper part of the basement, the granodiorite was highly weathered and thus is friable. The rock exhibits gr...

Numerous patents, publications, reviews and reports on the beneficial utilization of rice husk ash have appeared during last few decades [ Proceeding of Joint UNIDO-ESCAP-RCTT-PCSIR Workshop on Production of Cement Like Materials from Agro-waste, p 135-49, 1979 ] . In India rice husk has been put to use in some specific areas as renewable source of energy, development of pozzolanic/cementitious materials, filling materials etc. The suitability of rice husk ash as a soil stabilizer were also studied by Okereke of Nigeria [ Housing Science, Vol. 18(1), p 23-42, 1991 ] and he claimed that rice husk ash has some pozzolanic properties which with little addition of cement can effectively stabilizer lateritic soil. One of the earlier reference to potential benefits of using rice husk ash for making cement was published in 1956. [ Agricultural Experimental Station, Louisiana State University, Bull. No.507, 1956 ]. The characteristics of rice husk ash were studied in relation to utilizat...

When pulverized coal is burnt in kiln the ash is carried forward in the gases as fused (soften) particles which solidify into a roughly spherical shape. It is called as fly ash or pulverized fuel ash. The properties of this material as a pozzolana was first reported on in 1937 and its use in concrete started to develop in the USA in the following decade particularly for mass concrete dams. Later its use became wider and spread out to many other countries. In India f ly ash, an industrial by-product from thermal power plants, with annual generation of approximately 108 million tones and its proven suitability for variety of applications as admixture in cement/concrete/mortar, lime pozzolana mixture (bricks/ blocks) etc. is claimed as an ideal material which attracts the special attention. Cement and concrete industries account for 50% fly ash utilization at present. Up to 35% of suitable fly ash can directly be substituted for cement blending material. Addition of fly ash significa...

Gaize is soft, porous, highly siliceous, sedimentary rock containing a proportion of clay, which is found distributed over a considerable area in Ardennes and Meuse valley in France. Often fossiliferous, it may contain a fraction of carbonate and clay. Sometimes, silicified beaches are found in diffused form. Silicification results of impregnating the porosity of the silica colloidal type called opal [silica hydrated compound, SiO 2 .nH 2 O] with traces of Mg, Ca, Al, Fe, As, Na, K etc. It contains silica in a gelatinous condition and has a density of only 1.4 after drying. The rock has been used in the raw state as a pozzolana, but usually it is burnt at a temperature of about 900 ° C . Moler earth, a typical type of diatomaceous material is naturally occurring, soft, siliceous sedimentary rock that is easily crumbled into fine white to off-white powder. It has a particle size ranging from less than 3 micrometer to more than 1 millimeter but typically 10 to 200 micrometers. The po...

The pozzolanic properties of burnt clays were well known to the Romans, who utilized ground clay bricks and tiles as a substitute for the natural volcanic ash pozzolanas. The value of burnt clay as an addition to fat lime mortars to obtain hydraulic properties has also long been known in India and Egypt, where it passes under the names Surkhi and Homra. Experiments on burnt clay-lime mortars were carried out a century ago in connection with the rebuilding of London bridge, while still earlier Smeaton had tried them, without success, as a mortar ingredient for the Eddystone lighthouse. A Swedish engineer, Bagge of Gothenburg and Count Chaptal in France, both experimented in the eighteenth century with burnt-clay pozzolana. Vicat mentioned burnt-clay pozzolanas in papers published in 1843 and 1857, and they were discussed at some length in Captain Smith’s translation of Vicat’s Mortiers et Ciment Calcaries. A pozzolanic cement consisting of ground burnt clay and portland cement was desc...

According to the source of availability pozzolana is classified as natural pozzolana and artificial or synthetic pozzolana. The word pozzolana is derived from volcanic ash used by Romans in Italy, at Pozzuoli which was first identified as natural pozzolana. Most of the traditional natural pozzolana belongs to the group of volcanic ashes, slate and shales, diatomaceous earth etc. that were being used since the innovation of Portland cement. Besides the natural pozzolana lot of artificial pozzolana are now produced as by product in industries. Among the artificial pozzolana fly ash, burnt clay, blast furnace slag are most commonly used for manufacture of composite cement. Recent investigations on granite rock indicate very good pozzalanic behaviour. On the other hand granitic rocks are abundant in the nature. It may contribute a new direction for economical production of pozzolana.             Pozzolana is extensively used as an addition...

Granite for its high strength and texture is abundantly used for building construction. It may also be used as a source of natural pozzolana. Pozzolana is a siliceous or siliceous and aluminous material which, in itself, possesses little or no cementitious value but which will, in finely divided form and in the presence of water, react chemically with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties. Certain granite rocks have been identified which posses the pozzolanic character and can be used as cementing material in construction.