Study On Hydration Of Anhydrite Pastes Using Electrical Resistivity Measurement

This paper is based on the natural anhydrite, single sulfate stimulate anhydrite and compound excitation anhydrite as the research object. Through studying its resistivity of hydration and differential curve, combined with anhydrite under different excitation state of hydration rate, compressive strength and the change of ion concentration, the anhydrite hydration hardening process is divided into stage dissolution period, nucleation period, acceleration period and stable period. Studies have found that the resistivity can correctly reflect stimulates the change of ion concentration in the process of hydration of anhydrite, the initial value, the lowest value and the differential value of different excitation conditions of anhydrite in reflect the anhydrite hydration hardening of different characteristics. The initial value of resistivity curve reflect the difference of the excitation agent type and dosage, the lowest value reflect general ion concentration and supersaturation of anhydrite concentration, the size of the differential curve reflects the dissolution of anhydrite and the rate of crystallization nucleation.Through studying the resistivity curve of natural anhydrite hydration this paper found that the initial resistivity and low resistivity is higher and the resistivity can reflect the slurry liquid ion concentration, thus the initial resistivity and low resistivity values are high consistent with supersaturation is low, so the natural anhydrite hydration hardening speed is slow, the resistivity curve rise slow, compressive strength is low and increase slowly. The study found that the natural anhydrite excitation has no acceleration period, it is because of its low supersaturation.Studying resistivity curve and its stage classification of anhydrite hydration with sulfate found that the initial value, the lowest value of anhydrite hydration with sulfate is lower than natural anhydrite,differential curve peak is higher and zero appear more quickly than natural anhydrite. Resistivity curve of anhydrite hydration with sulfate has obvious acceleration period, this is the most obvious difference between inspire anhydrite and natural anhydrite resistivity curve(except the calcined alum, calcined alum have significant expansion effect). Observing resistivity curve and differential curve found that the main purpose of exciting agent increased the supersaturation of anhydrite accelerate the hydration process, and make nucleation period in advance. Through analysising the strength, hydration rate and resistivity found that there is obvious correlation between the resistivity and the hydration rate there is also obvious correlation between resistivity and intensity.Studying resistivity of anhydrite with salt and cement showed that resistivity value of compound excitation anhydrite is low, the resistivity differential curve peak of compound excitation anhydrite is bigger. Although its dissolving process is not like anhydrite with sulfate the advancing significantly, but in the early hydration process, resistivity curve rises quickly, differential value of resistivity is higher, and it maintain a longer time. This shows that the salt and Portland cement not only greatly promote the dissolution of anhydrite crystal, and the hydration of cement hardening is accelerated, the effect of compound excitation anhydrite is superior to single excitation, the compressive strength grow faster.Studies of inspire anhydrite resistivity show that the hydration hardening of the anhydrite process follow the theory of dissolution, nucleation and crystallization. Whatever can accelerate the dissolve the anhydrite, increase the degree of supersaturation of anhydrite can promote the hydration hardening of the anhydrite, but the effect is obvious different, we can quickly distinguish through resistivity curve.