The Influence Of Powder Content In Aggregate On The Performance Of Concrete Water Reducer

This paper is based on National973Key Basic Research Development Program in China, deals with the influence of the powder content in aggregate on the performance of concrete water reducer.Choosing sodium lignosulfonate water reducer, naphthalene water reducer and polycarboxylate water reducer, the paper studies the influence of the powder (clay powder and rock powder)content on them through working performance (setting time, fluidity, slump constant, workability),mechanical properties(7d strength and28d strength),and also with testing methods XRD(X-ray diffraction),SEM(scanning electron microscope) to see the hydration process, investigates the influence of the powder content in Aggregate on the performance of concrete water reducer systematically and comprehensively. The main work and results are as follows:1.Research on the influence of powder content on the setting times and fluidity of cement paste added these three water reducer.The setting times of cement paste added these three water reducer were shorten with the increasing of powder content. The initial and1h fluidity of cement paste added these three water reducer decreases with the increasing of clay content. The initial fluidity of cement paste added sodium lignosulfonate and polycarboxylate are decreases at the first and then get increased while the naphthalene has the opposite trend. And about1h fluidity of cement paste, naphthalene and polycarboxylate has a same trend that decreases after increasing firstly, while the sodium lignosulfonate stay the same.2. Research on the influence of powder content on7d and28d compressive strength of cement paste added these three water reducer.7d and28d compressive strength of cement paste added those three water reducer get increased slightly within the rock content.3. Research on the XRD and SEM test of the hydration products of cement added clay or rock powders.A small amount of clay powder can promote hydration, but when more than a certain range, clay powder will absorb water reducer, inhibit the hydration. Powder granules on hydration products can play a role to the nucleation, promote hydration, but above a certain range, because of the adsorption of water reducing, the particle dispersion effect becomes worse, hydration inhibited.4. Research on the influence of powder content on working performance of concrete added these three water reducer.With the clay powder replacing cement, keeping the concrete match ratio, slump constant decreases as the clay powder content rising, workability gets better. In the case of replacing cement by rock powder, keeping the concrete match ratio, slump constant get better within8%rock content. And with the rock powder content increases, workability gets better.5. Research on the influence of powder content on mechanical properties of concrete added these three water reducer.With the clay powder replacing cement, keeping the concrete match ratio, concrete compressive strength of7d and28d gradually decrease along with the clay content increases. In the case of replacing cement by rock powder, keeping the concrete match ratio, concrete compressive strength of7d and28d gradually rising along with the clay content increases within the8%rock content.