Research On Metamorphic Powder As Eco-Cement Additive

A sustainable development of cement industry is a necessity required by coordinated development of economy, society and environment. The production of the traditional cement has not only consumed the massive energy and the resources, but also has caused the pollution for the environment. It has become the new tendency using all kinds of rejectamenta to produce eco-cement. The present use of Portland cement is highly damaging to environment due to high quantities of CO₂ emissions. It is known that for each ton of Portland cement production one ton of CO₂ is produced. The use of Portland cement is on rise especially in developing countries. Hence, there is an urgent need of alternative ways for reducing the amount of CO₂ emissions due to Portland cement production and use. Partial substitution of Portland cement using reactive additions has become more vital, not only due to economic reasons, but also to environmental ones. Fly ashes from coal burning power plants have been used extensively for this purpose. In many countries, other sources of pozzolanic materials should be sought and investigated.The metamorphic rock is one of three kinds of mineral rocks. It is widely distributed in our country and has been mined and utilized widely. Along with the mining and utilization of metamorphic rocks, a great number of wasted materials are produced. This wastes resource and pollutes seriously environment. In order to promote utilization ratio of resources and decrease damage and pollution for the environment in the process of exploitation, abate the carbon dioxide (CO₂) massive emission in cement Production, in view of the metamorphic rock reject from some stone material factory of Beijing Fangshan, a series of research trial has been carried on.Based on the previous research on cement and concrete additive, the chemical composition, density and the grain-size distribution of metamorphic rocks are tested through X beam fluorescence method, the Li bottle and the centrifugal granularity method. Effects of metamorphic rocks with different volume on mechanical properties of cement mortar are studied by determining the flexural strength and compressive strength. The pozzolanic reactivity of different metamorphic rocks before and after high temperature is evaluated. Effects of Metamorphic rocks with different volume on water loss ratio and dry-shrinkage ratio of cement mortar are also tested. Moreover, partial metamorphic rock powders by high-temperature treatment are used to replace some 10%-20% of cement; the flexural strength and compressive strength of cement-based composite materials are tested. And the high-temperature treatment process is determined through differential scanning calorimetry-thermo gravimetric analysis. At the same time, the same tests of fly ash are carried on, and comparison and analysis of two groups are carried out.The test result indicated that, the metamorphic rock powder has certain pozzolanic reactivity. The high-temperature treatment may enhance the pozzolanic reactivity of partial metamorphic rocks, specially the strength at 1 day. The partial type metamorphic rock has the improvement function to the dry-shrinkage performance of cement paste. The different type metamorphic rock is different to the dry-shrinkage performance of cement paste. The cement-based composite material has the good mechanics performance when the content of the metamorphic rock powder is lower then 15%. The optimum addition of metamorphic rock powder is 10%-15%.