如何限制混凝土缸？（4种封盖方法）

Capping of Concrete Cylinders

需要封盖以使表面光滑，以在混凝土缸上施加压缩载荷。仅使用适当的方法限制圆柱混凝土测试样品。当圆柱测试样品的末端不在0.05 mm之内的平面时，需要限制这些测试样品。盖的表面应与样品轴成直角。封盖样品后，通过直边和触角仪检查盖的纯度，在不同直径上至少进行三个测量。帽子变得像可行的一样薄，在测试样品时不应损坏。

We can use any one of the following 4 methods for capping the cylindrical concrete test specimen.

1. 整洁的水泥上限
2. 硫封
3. 石膏石膏盖
4. 水泥砂浆封盖

1. Neat Cement Capping

1. 通过以所需的水/水泥比混合水泥和水来制备僵硬的水泥糊。
2. 将其放置2到4个小时，以避免盖子收缩的趋势。
3. Using a scoop, place some amount of stiff neat cement paste on top of the cylindrical test specimen.
4. Take a glass plate having thickness not less than 6.5 mm and diameter at least 25 mm larger than the diameter of the test specimen.
5. Using this glass plate, press down the stiff cement paste by giving the plate a rotary motion until it makes complete contact with the rim of the mould. Before doing this, apply a thin layer of oil or grease on the glass plate to avoid adhesion of the paste with the glass plate.
6. 在给板上的旋转运动时，请确保板始终保持平行于末端表面。准备帽后，它留了一段时间来变得艰难。
7. Repeat the same procedure to cap the other end of the cylindrical test specimen.

笔记

• This type of capping is done after 4 hours of molding the concrete, so that the concrete completely settle down in the mould.
• 水泥酱应具有所需的强度，以使帽子在施加负载时不会受到损坏。

2.硫上限

1. 在适当的温度下加热硫化合物（由2至3份硫组成至惰性填充剂的1部分），直到达到倒倒的稠度为止。
2. 取一勺融化的硫，然后将其倒入盖霉菌中。在执行此操作之前，请在盖霉菌上涂一层薄薄的油或油脂，以避免液体硫与盖霉菌的粘附。
3. 此后，立即将圆柱测试样品的一端放入含有液体硫的盖霉菌中，然后按下。将其保持在这个位置，直到硫变硬。
4. After that, tap the cap mould downward and remove the cylinder from the cap mould.
5. Repeat the same procedure to cap the other end of the cylindrical test specimen.

笔记

• This type of capping is done after removing the concrete cylinder from the mould.

3.石膏灰泥盖

1. 通过以所需的比例混合石膏和水来制备硬石膏。在准备糊状的同时，将其充分混合。这将有助于石膏增强力量。
2. Using a scoop, place some amount of gypsum plaster on top of the cylindrical test specimen.
3. Take a glass plate having thickness not less than 6.5 mm and diameter at least 25 mm larger than the diameter of the test specimen.
4. Using this glass plate, press down the stiff gypsum plaster by giving the plate a rotary motion until it makes complete contact with the rim of the mould. Before doing this, apply a thin layer of oil or grease on the glass plate to avoid adhesion of the plaster with the glass plate.
5. 在给板上的旋转运动时，请确保板始终保持平行于末端表面。After preparing the cap leave it for 20 to 30 minutes to become hard.
6. Repeat the same procedure to cap the other end of the cylindrical test specimen.

笔记

• This type of capping is done after removing the concrete cylinder from the mould.

4. Cement Mortar Capping

1. Prepare a mortar using cement similar to that used in the concrete and sand which passes 300 micron sieve and retained 150 micron sieve. The mortar should have a water/cement ratio not higher than that of the concrete of which the specimen is made.
2. 如果在样品表面收集了任何自由水，请用海绵或吸水纸或其他合适的吸收材料将其取出。
3. Prepare the cap by applying mortar firmly on the specimen and compact it with a trowel to a slightly convex surface above the edges of mould.
4. Then using a glass plate, press down the cap so formed, with a rotary motion until it makes complete contact with the rim of the mould. Apply a thin layer of oil or grease on the glass plate to avoid adhesion of mortar with the plate.
5. 将玻璃板放在位置，直到从模具中取出样品。

笔记

• This type of capping is done after 4 hours of molding the concrete, so that the concrete completely settle down in the mould.