Effect of Mitigating Strength Retrogradation of Alkali Accelerator by the Synergism of Sodium Sulfate and Waste Glass Powder

This work aims to utilize waste glass powder(WGP)as a plementary material to mitigate the strength shrinkage caused by the alkaline accelerator.Waste glass power was used to replace cement by 0%,10%,and 20%to evaluate waste glass powder on the alkaline accelerator’s strength retrogradation.The results show that the strength improvement effect of unitary glass powder is inconspicuous.Innovative methods have been proposed to use sodium sulfate and waste glass powder synergism,using the activity of amorphous silica in glass powder.Compared with the reference group,the compressive strength of 28d mortar increases by 67%when the sodium sulfate content is 2.5%,and the replacement amount of waste glass powder is 10%.Besides,XRD and SEM analysis of hydration products also confirmed that the synergistic effect of sodium sulfate and waste glass powder could reduce strength inversion.The findings presented in this paper are pivotal for using waste glass to solve the problem of strength inversion caused by the alkaline accelerator.

Effect of CSH Crystal Nucleus on Steam-Free Cured Fly Ash Precast Concrete Components

The measures of steam curing and early-strengthening agents to promote the precast components to reach the target strength quickly can bring different degrees of damage to the concrete.Based on this,the new nanomaterial CSH-the hydration product of cement effectively solves these measures’disadvantages,such as excessive energy consumption,thermal stress damage,and the introduction of external ions.In this paper,the effect of CSH on the early strength of precast fly ash concrete components was investigated in terms of setting time,workability,and mechanical properties and analyzed at the microscopic level using hydration temperature,XRD,and SEM.The results showed that under the same workability,CSH could significantly reduce the amount of admixture,shorten the final setting time,almost not affect the initial setting time,and accelerate the hydration of cement.At the optimum dose of 5%,the mechanical properties of the specimens were improved by more than 98%within 12 h of hydration,resulting in an earlier release time of 12 h and no risk of strength inversion later.The results of this paper give theoretical support to the behavior of precast components under steam-free curing.

选钼回水中铝离子对辉钼矿可浮性的影响机制

通过辉钼矿浮选实验、Zeta电位测试、Al^3＋溶液化学分析及X射线光电子能谱分析（XPS）,研究了选钼回水中的Al^3＋对辉钼矿可浮性的影响及其作用机制.结果表明,铝离子会恶化辉钼矿的浮选指标,并导致其表面Zeta电位显著偏移,表明辉钼矿表面有Al^3＋吸附;Al^3＋在溶液中主要以铝离子、羟基铝离子、氢氧化铝沉淀形式存在,后两者具有极强的极性,能吸附在辉钼矿活泼的＂棱＂上,铝离子与辉钼矿＂棱＂氧化生成的MoO4^2-反应生成钼酸铝沉淀;由于辉钼矿＂棱＂的面积比＂面＂的面积小很多,而铝离子主要吸附在＂棱＂上,因此铝元素含量不多,但其确实能吸附在辉钼矿表面,且既有物理吸附也有化学吸附.

Ca^(2+)和 Mg^(2+)对辉钼矿可浮性的影响对比

通过辉钼矿单矿物浮选试验,Ca^(2+),Mg^(2+)的溶液化学计算及辉钼矿表面Zeta电位和XPS检测,对比研究了Ca^(2+),Mg^(2+)对辉钼矿可浮性影响的差异性。结果表明,Ca^(2+),Mg^(2+)均会吸附于辉钼矿表面,改变辉钼矿表面Zeta电位并对辉钼矿的可浮性产生抑制作用,且随pH值增大,抑制作用增强;碱性条件下Mg^(2+)对辉钼矿可浮性的抑制强于Ca^(2+),且pH>9.0时,两种离子抑制作用的差异性更明显;pH=11.0时,Mg^(2+)为800 mg/L的矿浆中辉钼矿的回收率较Ca^(2+)为800 mg/L的矿浆中辉钼矿的回收率下降约34个百分点;Ca^(2+),Mg^(2+)均能与辉钼矿“棱”上的MoO4^(2–)结合形成钼酸盐沉淀,通过化学吸附的形式存在于辉钼矿表面;当pH>9.15时,钙仍以Ca^(2+),Ca(OH)+的形态存在并吸附于辉钼矿表面,且Ca^(2+)矿浆Zeta电位随pH增大呈上升趋势,但镁则以Mg(OH)2形态沉积于辉钼矿表面,且Mg^(2+)矿浆Zeta电位随pH增大迅速降低,这是两种离子对辉钼矿可浮性抑制作用不同的主要原因。