摘要
随着土木工程建设事业的全方位发展,混凝土骨料资源受到了制约。优良的骨料在某些地区已经开发利用,剩下的是低品质骨料,从建筑经济上考虑,利用低品质骨料已成必然趋势。本文结合实际工程,立足于降低工程所需混凝土配制成本和提高地产建筑材料的利用水平,对使用低品质辉绿岩和细砂配制系列混凝土进行了试验研究。
本文首先对地产的两种材料——辉绿岩和青砂(细砂)进行调查评估,指出两种材料品质不良。辉绿岩因母岩强度低、呈节理状,致使加工出的碎石针片状颗粒偏大,约12%~15%,且级配不良;青砂细度模数在1.6~2.4之间波动,级配差。两种材料的品质都不稳定。
其次,作者主要对低品质辉绿岩青砂骨料混凝土的配制和基本性能进行了试验研究,结果表明:(1)对于辉绿岩,不论细集料采用黄砂还是青砂,辉绿岩混凝土的强度均略高于石灰岩混凝土;但辉绿岩碎石中的针片状颗粒及不良级配导致混凝土的工作性能差,离析泌水严重;(2)细砂在配制水灰比<0.4的高强混凝土中,对强度影响较大,可使强度降低50~10%;细砂的表面特性可使混凝土的粘度变小,容易出现泌水;(3)根据流变研究结果,利用辉绿岩石屑代砂,掺加粉煤灰等活性掺合料的方式可有效地解决辉绿岩细砂混凝土严重的离析泌水;(4)重视粗骨料的筛选,优化混凝土配合比可充分利用地产材料配制性能合格的高、中、低强度混凝土。
最后,作者介绍了辉绿岩细砂混凝土在实际工程中的应用情况,并总结出辉绿岩细砂混凝土的施工工艺。
With the rapid development of construction undertakings, the resource of concrete aggregates is restricted. In some areas, excellent aggregates have been exploited and utilized, only low-quality aggregates left. Considering from construction economy, utilizing low-quality has been an inexorable trend .In order to decrease the unit cost of concrete and increase the utilization of local building material, this paper, dealing with practical projection, studies on preparation of concrete with low-quality diabase and green sand (fine sand) as aggregates through experiment.
The investigation and evaluation on the two material diabase and fine sand have been summarized first in this paper, the quality of the two materials is poor. For diabase, the content of elongated and flaky particles in crushed stone is on the high side, about 12%~15% and its gradation is harmful. And for fine sand, its fineness modulus fluctuates between 1.6 and 2.4 and the gradation is harmful. Furthermore, the two materials are unstable in quality.
Secondly, preparation of concrete with low-quality diabase and fine sand as aggregates and its basic performance are mainly studied through experiment. The results show that:(l) No matter the fine aggregate using medium sand or fine sand, the strength of diabase concrete will be always a little higher than that of limestone concrete. But the elongated and flaky particles in crushed stone and its harmful gradation lead to poor workability, that segregation and weeping of concrete is serious; (2) In high-strength concrete with w/c less than 0.4,the fine sand will which will decrease by 5%~10%. The surface character of fine sand equally leads to segregation and weeping; (3) According to rheological research of fresh cement pastes, poor workability can be resolved through the way of utilizing diabase stone chips replacing sand as aggregate and mixing active material such as fly ash; (4) By selecting diabase aggregate, optimizing mixture ratio and rigorously enforcing construction course,low-quality diabase and fine sand can be fully ultilized into preparation of qualified concrete posesing highjnedium and low strength.
Finally, the author briefly discusses the application of diabase-fine sand concrete hi engineering, and summarizes a set of technology on the construction of this concrete.
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