影响波特兰水泥环境和硬化的因素

(1)水泥组成的影响

The mineral composition of cement and their ratios are the main factors affecting the setting and hardening of cement. As mentioned above, various mineral components will reveal different characteristics when reacting with water. For example, theincrease of C3A能够加快水泥的设定和硬化率，而且水合热量高同时。

Generally speaking, if mixed materials are added into the cement clinker, the anti-erosion will increase, and the heat of hydration and the early strength will decrease.

(2)The Mixing Amount of Gypsum

Gypsum is called the retarding agent of cement which is mainly used for regulating the setting time of cement and is an indispensable component. Without gypsum, cement clinker can condense immediately by mixing with water and release heat. The major reason is that C3A in the clinker can dissolve in water quickly to generate a kind of calcium aluminate hydrate, a clotting agent, which will destroy the normal use of cement. The retardation mechanism of gypsum is: when cement is hydrated, gypsum reacts with C3A quickly to generate calcium sulfoaluminate hydrate which deposits and forms a protection film on the cement particles to hinder the hydration of C3A and delay the setting time of cement.

If the content of gypsum is too little, the retardation affect will be unobvious. Too much gypsum will accelerate the setting of cement because gypsum can generate a clotting agent itself. The appropriate amount of gypsum depends on the content of C3A in the cement and that of SO3 in gypsum, and it also related to the fineness of cement and the content of SO3 in clinker. The amount of gypsum should account for3%-5%of the cement’s mass. If the content of gypsum exceeds the limit, it will lower the strength of cement and it can even lead to poor dimensional stability, which will cause the expanded destruction of cement paste. Thus, the national standard requires that the content ofSO3should not be more than3.5％。

（3）The Impact of Cement’s Fineness

The size of cement particles directly affects the hydration, setting and hardening, strength and heat of hydration.

水泥颗粒是较好的，总表面积越大，与水接触的区域越大。因此，水合将快速，设置和硬化将相应地加速，并且早期强度将很高。

然而，如果水泥颗粒太小，则它们容易与水中的水和天空中的二氧化钙反应以破坏水泥的储存。如果水泥太好，硬化过程中的收缩大大。因此，水泥是较好的，能量越大，成本越高。通常，水泥颗粒的晶粒尺寸在7-200pm以内（0.007-0.2mm）。

（4）The Impact of Curing Conditions

The curing environment has sufficient temperature and moisture which is conducive to the hydration and setting and hardening process of cement and benefits the development of the early strength. If the moisture of the environment is very dry, the water in the cement will evaporate, leading to insufficient hydration and ceasing of the hardening. Serious cracks will happen sometimes.

通常，温度在固化时升高，水泥的水合和早期强度的发展变得快速。如果硬化过程在低温下发生，则尽管强度的发展缓慢，但最终的强度不会受到影响。但如果温度低于0⁰C，水泥的水合将停止，强度不仅会停止生长，而且由于水的冷凝，也会破坏水泥膏的结构。

在实际项目中，水泥产品的设定和硬化过程通过蒸汽固化和高压釜固化加速。

（5）The Impact of Curing Age

水泥的水合和硬化是长期的持续过程。随着水泥颗粒中各种熟料矿物质的水合度的增加，凝胶将生长，毛细血管孔隙率会降低，这使得能够随着年龄的增加而上升。事实证明，水泥在28D后迅速发展，28D后缓慢地发展。

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（6）混合水含量的影响

如果水泥消耗不变，混合含水量的增加将增强毛细血管孔隙的量，降低水泥浆料的强度，并延长凝固时间. Therefore, in practical projects, the amount of water and cement will be changed without modifying the water-cement ratio (the minimum amount of cement is regulated to ensure the durability of concrete) when the liquidity of cement concrete is adjusted.

（7）混合物的影响

波特兰水泥的水合，设定和硬化受C3s，C3A的约束。所有影响C3S的水合的所有混合物，C3A都可以改变水合的性能，波特兰水泥的凝固和硬化。例如，加速剂剂（如CaC12，Na2SO 4）可以加速水合和水泥的硬化并改善其强度。相反，延迟剂（如钙木硫酸钙）可以延迟水泥的水化和硬化，并影响早期强度的发展。

(8)The Impact of Storage Conditions

The inappropriate storage will expose cement to moisture. The particle surfaces agglomerate because of hydration which seriously reduces the intensity. Slow hydration and carbonization will happen due to the impact of the water and C02 in the air, even though the storage is good.

3个月后强度降低了10％-20％，6个月后达到15％-30％，1年后25％-40％，因此水泥的有效储存期为3个月，不应储存水泥许久。