Preparation And Performance Of The Novel Ecological Concrete Expansion Agents

The tailings were used to produce expansion agents by mineral composition design, ingredients calculation, grinding and appropriate calcining process in this paper. Disscuss the feasibility of using tailings to prepare expansion material by analysising composition of concentrates and tailings firstly, and prepare the novel ecological expansion agents with early expansive behaviour and delayed expansive behaviour to compensate the shrinkage of different kinds of concrete structures by determine the proportion of magenisit tailings and dolomite taiings, TG-DSC, SEM, XRD and the liquid conductivity method were applied to measure performance of the novel ecological expansion agents lastly. The influence of calcining system of expansion agents, variety, dosage, admixture, and curing condition on mechanical properties and deformation properties of paste, mortar and concrete was researched.The experimental results are shown following:1 According to XRD and chemical analysis of raw materials, tailings after pretreatment and concentrates were close in content, Which proved that it was feasible to use tailings to produce the novle eclogical expansion material.2 Magnesite completely was decomposed respectively calcined at T₁℃under 90 min holding time, T₂℃under 60 min holding tim. Based on the complete decomposition fo Magnesite tailings, the higher the calcinations temperature, the longer the holding time, the worse the activity of MgO. The smaller the particle fineness of MgO it was, the better the activity of MgO. According to TG-DSC and taking into account the needs of industrial production and heat loss of burning equipment, the lowest calcination temperature was T₁℃.3 With the amount increase of expansion agents, the strength increased gradually. Compared with the strength of mortar without any expansion agents, the strength of mortar with expansion agents increased by 2% and 15%.4 Expansion of paste and mortar added with B and F expansion agents can reach 80%-90% of that with A. The expansive properties of expansion agent are greatly affected by many factors. The paste and mortar added with expansion agent calcined between T₁℃and T₂℃, expansion at the early stage are faster, and it is slower at the later stage; the paste and mortar added expansion agent calcineda at T₃℃, expansion at the early stage are slower, it is faster at later stage. With the amount increase of expansion agent, the expansion increased correspondingly. The higher the curing temperature it is, the faster the expansion.it is. Fly ash restrains expansion caused by CaO and MgO. Hydration of CaO fasters and expansion is mainly at early stage while hydration of MgO slows and expansion is mainly at later stage.