Research On Anhydrite Expansion Admixture

During the technical development of modern concrete, concrete structure crack (especially early-age crack) becomes more and more serious and has been one of main research directions of civil engineering. Adding expansion admixture is the main material measures to control concrete structure crack in our country at present. Expansion admixture of concrete can offset the tension-stress caused by drying shrinkage or temperature lowing of concrete. It has a good compensation to shrinkage, and can improve the anti-cracking and anti-penetrating performance of concrete. It is often added to concrete top roduce expanding concrete or the anti-cracking and anti-penetratingconcrete, which are widely used in such engineering as waterproofing,anti-penetrating, mending etc. The expansion admixture include at present sulpho aluminate, (such as UEA, EA-L etc), calcium oxide, and some composite expansion admixtures. In practical uses, the major performances of concrete are associated with the quantities, types and the service conditions of the expansion-admixture. The expansion admixtures of concrete available at present still have many shortcomings, such as the greater quantities required, the non-relevance between developments of concrete strength and durability and expanding speeds of expansion admixture, the evaluation of expanding effects, the DEF of AFt etc. Unfortunately, few achievements in these aspects have been obtained all over the world.The previous researches show that anhydrite can be used in expansion admixtures as a kind of basic materisaLAccording to the composition of expansion admixtures and the anhydrite of jiangxia,we research and product the anhydrite expansion admixture with-the excellent property successfully.The research not only removes the fine crackles in the cement stones,but also applies a new developing way to the industrial waste gypsum.As far as the development of expansive admixtures is concerned,the research of guiding is significance in theory certainly.In order to research the effectiveness of expensive admixture in concrete, this thesis discusses the influence of water-binder ratio changing,quantity of expensive admixture changing, adding of mineral admixture to expensive effectiveness of the expansion admixture.The results indicate that the AG expansion admixture triturated by alunite and anhydrite and FG expansion triturated by fly-ash and anhydrite also have good expensive and resistace effectiveness,which can reach national standard.