XY-CMA High-performance Anti-Cracking Expansion Agent
XY-CMA is an anti-crack expansion agent which uses calcium sulphoaluminate hydrate as expansion source and combines high-efficiency expansion and high-ductility materials. Mix a certain amount of XY-CMA in concrete in early and middle hydration can generate a large amount of calcium sulphoaluminate hydrate (entringite) that can cause expansion of concrete. Under the constraint of steel bars and vicinal position, a pre-compression stress of 0.3-0.8 Mpa can be built in the concrete structure, which can substantially offset the contraction force generated during the hardening process of concrete, thereby preventing or alleviating cracks derived from concrete shrinkage, and compacting the internal structure of concrete. XY-CMA can improve the pore structure of concrete, reduce the large porosity, reduce the total porosity, improve the compactness, and substantially improve the impermeability of concrete. Concrete in the dry environment of later hardening process or large volume concrete in the cooling period will have volume shrink, and the expansion generated by XY-CMA in the early and middle hydration can offset all or most of the shrinkage in the later stage. High-ductility materials in XY-CMA can greatly improve the elasticity and ductility of concrete, reduce the late shrinkage of concrete, improve the brittleness of concrete, and enhance the crack resistance of concrete. Therefore, XY-CMA high-performance expansion agent makes concrete have anti-crack and impermeable properties, achieving permanent anti-crack and impermeability of cement concrete structure. In the early stage of hydration, CA of XY-CMA first provides a large amount of expansion energy that some CA react with CA minerals and CaSO \ Ca (OH) to make the crystalloid grow further. The expansion generated in the early and middle hydration jointly compensate the shrinkage, while lagging expansion of calcined mineral materials produced by the rotary kiln facilitates to compensate the later shrinkage of concrete. During the expansion reaction, the minerals of XY-CMA improve early strength of concrete stimulated by the active minerals, and the early strength constrains early expansion in a certain degree to enhance the bending strength of concrete greatly. At the same time, the pre-stress under the constraint is developed, which enhances the stretch resistance of concrete, making its crack resistance and later shrinkage better than other expansion agents.
一、XY-CMA Properties
1.Concrete mixed with XY-CMA has same rheological properties before hardening as ordinary concrete;
2.The slump loss of concrete within 1 hour is greatly reduced compared to other types of expansion agent;
3.Impermeability mark ＞S12, which is superior to ordinary concrete;
4.The product has no corrosion to steel bars, no pollution to water quality, and higher sulfate resistance than ordinary concrete;
5.The product has good adaptability to other admixtures such as cement, water reducing agent, pumping agent, and antifreeze;
6.The product has advantages of controllable limited expansion rate, small dry shrinkage, good later crack resistance, good ductility, high concrete strength, small slump loss, and excellent thermal stability.
二、Reference dosage and use precautions
1.Construction follows the same specifications of ordinary concrete. However, XY-CMA is suitable for general-purpose cements of grade above 32.5, and the recommended amount is 6-8%;
2.The mixing ratio of XY-CMA in concrete should be accurate, on-site mixing time is 30s longer than ordinary concrete;
3.In order to exert its expansion efficiency, timely and adequate moisturizing maintenance is important. When the concreting is completed, watering maintenance is started after 2 hours of final setting, and the curing period is 7-14 days. It is necessary to keep the concrete surface moist that the wall shall be covered with hanged gunnysacks or sprayed water ;
4. XY-CMA mixed concrete is not suitable for construction under temperature condition over 80 ° C. When the construction temperature is below 5° C, insulation and antifreeze measures shall be adopted;
Concrete mixed with different types of admixtures has different effects in compensating shrinkage; thereby it is necessary to test the admixture before use.