Study On The Water Reducing Agent JUS Applied To High Performance Concrete

High performance has become the emphasis and orientation in the development of concrete technology. Admixtures are absolutely necessarily to meet all kinds of properties of high performance concrete. Polycarboxylic water reducing agents have been noticed widely because it can depress the quick slump loss that is easily brought by high range water reducing agents, but their applications have been limited because of the high price. To reduce the cost, the polycarboxylic component that is made by ourselves is commixed with the other components that have all kinds of purposes, and a kind of high performance water reducing agent JUS has been manufactured. The experiments show that JUS has the water reducing effect much the same as Naphthalene series high range water reducing agents and depresses the slump loss in the condition that the final setting is not retarded. The early strength is accelerated slightly.The effects of JUS on the rheological properties of the paste were examined and the reasons that improve the rheological properties have been discussed by means ofζpotential,combined water amount, heat of hydration, DTA, TGA and so on. The polycarboxylic component J possesses the comb type structure. It is the out side chains(C>16) of J that counteract the particles to combine one another when the surface of particles is covered with JUS, so the paste are avoided to flocculate for some time. Compared with naphthalene series high range water reducing agent, not only the negativeζpotential is augmented, but also the period of time keeping the higher negativeζpotential is prolonged when JUS is mixed into the cement paste. Maintaining the high cohesion potential energy for a long time is one of the reasons that the fluidity loss is decreased. In addition, because of the strong screening function of JUS the cement hydration velocity falls much more in the inducement stage that corresponds to the fluidity loss of the paste. Therefore, it is an important reason as well that JUS reduces cement paste fluidity loss.The actions of JUS are mostly at the initial hydration stage. After the inducement stage, along with the screening action removing the hydration activation energy at the stage controlled by the interface reaction in the paste mixing JUS is smaller than that in the paste without any admixture and the hydration velocity in the paste mixing JUS is higher than that in the paste without any admixture. The amount of hydration products in the paste mixing JUS catches up with that in the paste without any admixture quickly. Therefore, JUS doesn't prolong the final setting time and increases the early strength slightly. XRD, DTA and TGA show that JUS doesn't change the type and quantity of the hydration products. SEM photographs show that JUS doesn't change the shape, size and distributing state of the hydration products. JUS does no harm to the strength development.