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The SO_4~(2-)concentration distributions in surface region of cement mortar immersed in sulfate solution at early stage were measured by layered sampling method combined with chemical analysis, and the diffusion coefficients of SO_4~(2-)anions in surface region of mortar into internal area were calculated by means of instantaneous plane diffusion theory. The experimental results showed that the SO_4~(2-)concentration gradually reduced when the diffusion depth increased in the surface region of mortar. Diffusion coefficient(D) was relevant with the concentration and kind of environmental sulfate solution, which reduced with immersion time at the beginning, and then rose slowly after a period of time. The calculation of initial diffusion coefficient(D_0) and starting time of deterioration(t_∞) caused by sulfate attack was further attempted based on the data of diffusion coefficient, and it was found that D_0 and t∞ were all relevant with concentrations of sulfate and different kind of sulfate as well. 相似文献
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An appropriate proportion of alkali activated slag cement, abbreviated as AASC later, was determined based on strength test of paste specimens. Results showed that AASC prepared from 14% low modulus water glass and blast furnace slag presented its compressive strength of hardened cement paste of 69.6, 84.0 and 91.8 MPa at 3, 7, and 28 d curing ages respectively. Flowability of the fresh tailings-cement pastes and the strength development of hardened tailings-cement paste were also tested both in the cases with addition of AASC and Portland cement. The fresh tailings-cement paste added with AASC presented much better flowability and the corresponding hardened paste presented higher compressive strength, especially the long term strength, than those added with Portland cement. Therefore, tailings paste added with AASC allowed lager solid content than that of Portland cement in order to keep the similar flowability. SEM observation on the microstructure of the hardened tailings-AASC mixture pastes showed obvious cementation effect. MIP measurements also showed that the total porosity of the hardened tailings-cement pastes decreased, and the portion of larger pore also decreased when the dosage of AASC increased. It is believed that AASC is more suitable to be used as a binder for the stabilization of zinc-lead tailings and for its backfilling operation than Portland cement. 相似文献
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提出建立基于生命周期的数控转塔冲床寿命分布模型,揭示包含早期故障期和偶然故障期的故障机理和规律.模型表明,采取可靠性增长技术措施后的数控转塔冲床故障间隔时间分布是形状参数接近于1的威布尔分布,故障率A(t)曲线残存少许的浴盆曲线的左侧面,削掉了故障率高的曲线段,说明早期故障大部分已经在主机厂消除,可靠性增长的技术措施已经收到明显效果.基于生命周期的寿命分布模型的建立,为科学评估数控转塔冲床的可靠性水平提供了理论依据. 相似文献
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为了进一步提高爆燃压裂工艺设计与效果预测水平及工程应用效果,基于爆燃压裂原理和油藏渗流理论,利用保角变换方法,建立了爆燃压裂油井产能计算模型(包括流体从油藏边界渗流到爆燃裂缝的渗流外阻模型,和流体在裂缝中渗流入井的渗流内阻模型)并编制了计算软件。以低渗油藏油井F31-10井为例,计算、分析了油藏参数和爆燃裂缝参数对爆燃压裂油井增产效果的影响规律。研究结果表明:爆燃裂缝长度、裂缝数量和爆燃裂缝导流能力对油井增产效果有影响,影响程度由大到小依次是爆燃裂缝长度、裂缝数量和爆燃裂缝导流能力;在爆燃裂缝长度和裂缝数量一定的条件下,存在一个最佳的爆燃裂缝导流能力;爆燃压裂后油井增产倍数为1.365~2.115,且增加爆燃裂缝长度和爆燃裂缝数量比增加爆燃裂缝无因次导流能力对增产更有利。 相似文献
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通过水泥砂浆强度试验方法研究了水泥熟料-粉煤灰体系中添加CaO、Na2SO4、明矾等化学物质对其中的粉煤灰活性的激发效果,同时借助于XRD和SEM分析了水泥硬化浆体的组成和微观结构.研究结果表明:CaO-Na2SO4-明矾复合添加能够很好地激发粉煤灰活性,使粉煤灰水泥早期强度降低程度减小.采用42.5等级硅酸盐水泥熟料,粉煤灰掺量高达50%时水泥强度仍然能够达到42.5等级指标.XRD分析表明,CaO-NaSO4-明矾复合激发剂的加入引起了水泥硬化体样品中石英和Ca(OH)2衍射峰的降低,说明它们在一定程度上促进了水泥水化放出的Ca(OH)2与粉煤灰中酸性氧化物的反应,从而加剧粉煤灰潜在活性的快速释放.水泥硬化体样品的SEM照片显示,CaO-Na2 SO4-明矾的加入,使粉煤灰球体表面腐蚀明显,硬化体结构更加致密化. 相似文献
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