一、UEA-H mixed concrete features and application technique

1.Compared to ordinary concrete without UEA-H, UEA-H mixed concrete has similar fluidity before setting. The slump loss of UEA-H mixed concrete is faster than ordinary concrete with shorter setting time, but does not affect the construction;

2.As the amount of UEA-H increases, the expansion rate of concrete augments, and strength reduces. When preparing contraction concrete, the mixing amount is 8-10% of cement, and limited expansion rate is 2-3×10-4, forming a self-stress of 0.2-0.7 Mpa in the concrete;

3.Under the specified mixing amount, compressive strength of concrete over 28 days is similar to that of ordinary concrete without UEA-H, but the late strength continues to increase;

4.The impermeability index of UEA-H mixed mortar is ≥S30, which is greatly superior to ordinary concrete. The frost resistance mark D is >150, and has no corrosion to steel bars;

5.The sulfate resistance and seawater corrosion resistance of UEA-H mixed concrete is better than that of ordinary concrete, without pollution to the water. UEA-H can be mixed with other admixtures, but must be determined through test.

二、Usage precautions of UEA-H high-performance low-alkali expansion agent

1.Design

(1)The mixing ratio of UEA-H high-performance and low-alkali expansion agent is the same as that of ordinary cement concrete. When preparing impermeable concrete, it shall be according to the regulations: the amount of cement should not be less than 300kg/m3. The mixing amount of UEA-H high-performance low-alkali expansion agent (E) is calculated by E/C+E, C represents cement, E represents expansion agent, which is 8-10% of cement, for special structural parts the mixing amount is 12%. The mix rate of UEA-H high-performance low-alkali expansion agent should be determined through testing. It is not only necessary to measure the slump, strength and impermeability of the concrete mixed with expansion agent, but also to measure the limited expansion ratio of the concrete. According to standard GBJ719, the characteristic index of the compensation contraction concrete mixed with expansion agent is: the limited expansion ratio after 21-day maintenance is ≥ -0.020%. The concrete must meet design specifications. The user should calculate the mixing amount of expansion agent according to different structural parts to meet the requirements of compensation contraction;

(2)The spacing of post-concreting joints mixed with expansion agent can be extended to 60m, ultra-long structure exceeds 60m can use expansion reinforcement belt to replace post-concreting, with continuous or intermittent seamless design and construction method, which are the patents of China Building Materials Academy. Technical consulting services can be sought from China Building Materials Academy to ensure the quality of the project

2.Construction management

(1)During construction, the mixing ratio shall be according to the design requirements to ensure the accuracy of mixing amount of expansion agent. The mixing time of on-site concrete has to be 30s longer than the ordinary concrete to ensure the mixing uniform of expansion agent and cement and water reducer, improving the evenness of the mortar. The distribution and vibration of the expansion concrete has to be carried out in accordance with the construction specifications;

(2)The post-concreting maintenance of UEA-H high-performance low-alkali expansion agent is very important that according to the climate situation it shall carry out on-time moistening maintenance and the time interval should be no less than 14 days. The wall's formwork should be made of plywood with good moisture retention. When the concreting is finished, set water pipes at the top to sprinkle the wall. The formwork shall be removed on the 5th day, then cover the wall with gunnysack and spray water as soon as possible. The hydrating maintenance is 10-14 days;

Even use compensation contraction concrete, the concreting shall be carried out in sections of 30-40m, with an expansion belt in a width of 2m between each section, and set a steel draught plate. On the 28th day, use expansion concrete to backfill. The maintenance is no less than 14 days. After 14-day maintenance, the basement shall be covered with soil as soon as possible. The storey should have wall enclosure construction, the roof should apply waterproof insulation layer as soon as possible.