Rock Pozzolana

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...