The Study Of Dolomite Powder Composite Mineral Admixture Of Concrete

This paper generally depicts how concrete composite admixture that are anti-permeability and anti-freezing are produced through putting the dolomite fines into the cement mortar and concrete samples, by the principle that the cement base and the dolomite can produce alkali carbonate expansion reaction. This technology will play a good demonstration to the production and the application of functional concrete composite admixture.In the process of the concrete, because of the change of the moisture in the concrete, the hydration reaction of the cement, the temperature, all of them can lead to the volume contraction of concrete. The volume shrinkage of concrete and the crack from it can produce adverse effect to the bearing capacity of the concrete itself, working performance and the durability. This paper, through the determination of strength, the expansion and the contraction of samples in curing age, has confirmed the compensation effect on volume shrinkage when a certain number of dolomite fines are mixed in the cement. The X-ray diffraction proved that the dolomite fines in the cement has already formed the new hydration products. Contrast to the specimen microstructure observed by scanning electron microscope, confirmed that the alkali carbonate expansion reaction was positive when the dolomite fines were put into the cement, and that the micro cracks that formed by the volume shrinkage of cement hydration were eliminated. With the strength test of the Cement mortar specimens, we understand the influence of dolomite fines content on the cement strength, confirmed that it had no obvious adverse effect to the compressive strength and flexural strength of cement of dolomite powder admixture.This paper also analyzed the influence on the strength of the cement mortar samples through adding a variety of alkalis as initiators. Thus the activity of the dolomite and its suitable alkali initiators can be concluded. At the end of the paper, several tests on different strength, frost resistance, carbonation resistance, permeability and other performance of concrete with different dolomite fines were introduced, all of which have led to this conclusion that dolomite composite mineral admixtures can improve the permeability and the carbonation resistance of the concrete.So, using the principle that alkali excitation dolomite can generate volume expansion, associated with its reliable theory, low material consumption, obvious effects, low cost, concrete composite admixture that are anti-permeability and anti-freezing will have broad market prospect and high promotion value to the production and use of the concrete and mortar.