Effect Of Alkali Sulfate On Physical Properties Of Portland Cement And Sensitivity Analysis

With the shortage of resources becoming more and more severe, the production cost is seeing incredibly increase. Inferior fuels such as the high sulfur are used to produce cement clinkers, which leads to incessant increase of sulfate in the cement with complicated sources and kinds. Aphthitalite, thenardite and arcanite is the main alkali sulfate in cement clinkers and the variation of theirs content may will have a greater impact hydration and hardening of cement.Most of the past studies concentrating on alkali sulfate have directly used analytical, while actually the sulfate in cement have gone through high temperature calcinations, which results in different effect on cement compared with analytical sulfates. it is necessary that research on the different effect of analytical and high-temperature calcination alkali sulfates on cement, the effect of high-temperature calcination alkali sulfate on cement and the sensitivity are discussed as well.We prepared the alkali sulfates of clinker by adopting high-temperature calcination. And with the increase of alkali content or SO3 content, compared the effect of hightemperature calcination and analytical alkali sulfate on water requirement of normal consistency, setting time, compressive strength, and volume stability of cement. It is confirmed that Effects of high-temperature calcination and analytical alkali sulfate on physical properties of cement are different.It found that crystal of alkali sulfates are changed after high-temperature calcination, by comparing the XRD image of thenardite and sodium sulfate, arcanite and potassium sulfate. This change may result in some differences influence of analytical and high-temperature calcination alkali sulfates on Cement.Selecting natural gypsum mixing into the cement, changing the content of the alkali sulfates, the effect of high-temperature calcination alkali sulfate on water requirement of normal consistency, setting time, compressive strength, and volume stability of cement are researched. The results show that: the water requirement of normal consistency of cement containing thenardite will be decreased, all of alkali sulfates can speed up the setting of cement, decrease the later age strength, increases the shrinkage of cement.Kruskal-Wallis test is used to explore the effect significance of alkali sulfates on cement properties. It found that: the probability that the effect of alkali sulfates on the water requirement of normal consistency and setting time of cement shows significance is more than 60%, and it's 95% for compressive strength. The probability that the effect of sulfates on volume stability of cement shows significance is more than 92% for aphthitalite, 84% for thenardite and 95% for arcanite. It proved that alkali sulfates have a significant effect on the properties of Portland cement.The sensitivity that alkali sulfates affect cement properties is analyzed by differential. The results show that: the sensitive point that alkali sulfates affect the water requirement of normal consistency of cement are about: the dosage of aphthitalite is 1.75%, the dosage of thenardite is 1.38%, the dosage of arcanite is 0.84%; The sensitive point of affecting setting time are about: the dosage of aphthitalite is 1.89%, the dosage of thenardite is 1.61%, the dosage of arcanite is 0.55%; The sensitive point of affecting compressive strength are about: the dosage of aphthitalite is 1.59%, the dosage of thenardite is 1.70%, the dosage of arcanite is 1.96%; The sensitive point that alkali sulfates affect the expansion of cement immerged in water circumstance are about: the dosage of aphthitalite is 2.4%, the dosage of thenardite is 2.07%, the dosage of arcanite is 0.8%; The sensitive point that alkali sulfates affect the drying shrinkage of cement are about: the dosage of aphthitalite is 1.81%, the dosage of thenardite is 2.16%, the dosage of arcanite is 2.81%.It showed that sensitive content of arcanite affecting on the performance of cement is less than 1%, adversely affect sensitive content of alkali sulfates on strength and shrinkage is higher.