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在商品混凝土生产中外掺磨细粉煤灰和外加剂(简称“双掺”)已成为一项成熟的技术正日益得到推广和应用。但是“双掺”技术在应用时有些问题是不容忽视的,本文就此作一浅析,以期引起大家的重视。一、粉煤灰胶凝系数及掺量粉煤灰是以氧化硅、氧化铝为主要成份,含有相当多的玻璃体或其它无定形物质。粉煤灰本身并不具有水硬性,只有在与石灰或水泥混合后再拌以水才能产生明显的强度,因此外掺磨细粉煤灰的混凝土配合比设计是在同标号不掺粉煤灰的混凝土等效前提下,采用超量取代法,即粉煤灰掺量大于其所取代的水泥量,一部份代替水泥,一部份代替砂子,使混凝土和易性不变。粉煤灰胶凝系数K实际上就是指1kg粉煤灰在混凝土中对强度的作用,即相当于不掺粉煤灰混凝土同等强度中Kkg水泥的作用。因此不必须根据不同标号、不同龄期的混凝土采用
The inclusion of finely ground fly ash and additives (referred to as “dual blending”) in commercial concrete production has become a mature technology that is increasingly being promoted and applied. However, some problems in the application of “double-blended” technology can not be ignored. This article makes an analysis on this, in order to arouse everyone’s attention. First, the fly ash gel coefficient and the amount of fly ash is silica, alumina as the main component, containing a lot of glass or other amorphous material. Fly ash itself does not have hydraulic properties, and only when mixed with lime or cement and then mixed with water can produce significant strength. Therefore, the mix proportion design of concrete with finely ground fly ash is the same without adding fly ash. Under the equivalent premise of concrete, an oversubstitution method is adopted, that is, the amount of fly ash is greater than the amount of cement that it replaces, part of it replaces cement, and part of it replaces sand, so that the workability of concrete does not change. The cement coefficient K of fly ash is actually the effect of 1kg fly ash on concrete strength, which is equivalent to the effect of Kkg cement without the same strength of fly ash concrete. Therefore, it is not necessary to use concrete according to different labels and ages.