Applications of High Alumina Cement
CSA cement is a special cement with high strength, rapid setting time and low shrinkage. The main minerals of CSA cement is dicalcium silicate (C2S) and calcium sulfoaluminate (C4A3S). It is widely used to chemical construction materials such as dry-mix mortars, shot concrete, concrete repair and etc.
Applications of High Alumina Cement
Construction requirements for high alumina cement
1. The water consumption of high alumina cement in the mortar strength test shall be determined when the water-cement ratio is 0.45 and the mortar fluidity reaches 110-130 mm. When the mortar fluidity produced under the condition of 0.45 water-cement ratio is within the range of 110-130mm, the mixing water amount of molding mortar can be converted from the 0.45 water-cement ratio(243ml). If the mortar fluidity is less than 110 mm or more than 130 mm, the amount of mixing water shall be accordingly decreased or increased to separately prepare the mortar and remeasure the fluidity until it reaches the following range: If the fluidity is less than 110 mm, increase the amount of water to make it reach 110-119 mm; if it is more 130 mm, reduce the amount of water to make the fluidity reach 121-130 mm. In these two conditions, the mixing water amount of molding mortar is calculated according to the water-cement ratio which is in accordance with the fluidity requirement. The fluidity of cement mortar shall be implemented in accordance with GB 2419-81 Test Method for fluidity of Cement Mortar.
2. After molding, cure the specimen of high alumina cement mortar in a curing box with the mold for 6 hours where the temperature is 20±3℃ and the relative humidity is over 90%, then remove the mold and put the specimen into 20±2℃ water for curing. It allows to extend the maintenance time of the cement with slower setting and hardening speed in the moisture box, but the curing time in water shall be recorded and the specimen shall not be placed in the same pool with other kinds of cement specimen. The strength test for 1 day age shall be carried out within 24±1 hour from the time of molding.
Attention points of high alumina cement uses in building projects
1. In the construction process: generally it can not be mixed with Portland cement, lime and other gelatination substances which can precipitate calcium hydroxide and the mixing equipment must be washed clean before use.
2. It should not be used in the projects which need to meet with a lot of alkaline solution.
3. The hydration heat of high alumina cement is concentratedly released in the early stage, so watering and curing shall be started from the hardening. Generally it should not be used to pour mass concretes.
4. The high alumina cement concrete should be designed on the basis of stability because its strength decreases greatly in later period. The stability strength of high alumina cement concrete shall be determined by the lower strength value of the 7th day and 14th day after curing the demolding specimen in 50±2℃ water. It can produce the concrete whose stable strength is above 200 kg/cm when the cement adapted is above No.525, water-cement ratio is less than 0.40, and the cement content exceeds 400 kg/m3.
5. The curing temperature shall not be higher than 50℃ when accelerating the hardening of the concrete with steam curing.
6. When used for reinforced concrete, the reinforcement protective layer shall not be thinner than 3cm.
