净浆流动度损失与混凝土坍损的相关性研究

对粉煤灰取代水泥量、粉煤灰质量,砂的含泥量和外加剂掺量等因素对净浆流动度经时变化及混凝土坍落度损失的影响进行了研究,探索了净浆保持性与混凝土坍损间的关系。结果表明:砂的含泥量对混凝土的工作性能影响明显,当实验所用砂含泥量达到I、II类时,同掺量外加剂的净浆流动度保持性能可以较为准确地反映出混凝土的工作性能;当实验所用砂为III类时,净浆流动度保持性能优异的外加剂掺量增加10%推荐为混凝土的试拌试验掺量。

人工砂MB值对混凝土性能的影响研究

混凝土工程中,因混凝土需求量较大,天然骨料难以满足需求,各类性质差异较大的岩石均可用作混凝土的骨料,人工骨料中,粗骨料含泥裹粉量可通过目视感观判断,机制砂中往往不能确定是石粉还是泥粉,质量良好的石粉对混凝土是有益的,若人工砂中含有一定量的泥粉,会对混凝土质量及耐久性产生致命的危害,机制砂中细小颗粒是有利的石粉还是降低混凝土性能的泥粉,须通过亚甲蓝MB值检验。本文主要进行了MB值对混凝土单位用水量、含气量、混凝土抗压强度的影响,定量的分析了人工砂中MB值对混凝土的影响,通过这篇论文希望引起质量控制人员对人工砂中MB值的足够重视。

Strength Evaluation of Normal Strength and Self-compacting Reinforced Concrete Beams under the Effect of Impact Loading

This paper is devoted to investigate experimentally the strength evaluation of normal strength and self-compacting reinforced concrete beams under the effect of impact. The experimental work includes investigating of eight （180×250×1,200 ram） beam specimens. Three variables are adopted in this paper： tensile reinforcement ratio, type of concrete （NSC （normal strength concrete） or SCC （self-compacting concrete）） and height of falling （dropped） ball （1 m or 2 m）. The experimental results indicated that the number of blows increased with increasing of tensile reinforcement ratio and compressive strength by about 35% and 123%, respectively. Maximum mid-span deflection was increased with increasing falling height and decreased with increasing reinforcement ration and concrete compressive strength. The increasing of concrete compressive strength is more effective than increasing of the reinforcement ratio, it appeared that the percentage of increasing exceeds 50%. The ultimate strength is decreased with increasing the falling height for about 34%-44%.