Study On Chemical-activated High Volume Blast Furnace Slag In Concrete With High Strength By Steam-curing

Because blast furnace slag has many advantages, such as potential activity, green,low cost and improve the durability of concrete, so it could replace cement partially andreduce the cost. But the mixing amount of blast furnace slag is generally only about30%in the actual production of the current concrete prefabricate industry. Therefore, inthis paper, the slag-cement gel system, which contents50%blast furnace slag, will beactivated by chemical activators and high temperature steam-curing. The type anddosage of the optimal activators will be determined through the tests of the concretesteam-cured strength, and the mechanism of alkali and sulphate activators activatingslag-cement gel system will be studied through the micro analysis. The main contents ofthe research are as follows:First of all, the dosage of blast furnace slag, which was determined through thetests of the concrete steam-cured strength,was50%of the total gelled material.Polycarboxylate superplasticizer had the best performance of strength increasing andwater reducing, which was determined through the tests of the concrete steam-curedstrength and slump.Secondly, the effects of different activators adding alone on slag-cement gel systemwill be analyzed through the tests of the concrete steam-cured strength. The resultsshow that alkaline activators can reduce the steam-cured strength of high volume blastfurnace slag concrete, such as Na₂SiO₃·9H₂O、NaOH and Na₂CO₃, even if the dosage isvery small; CaO has a certain excitation effect. When the sulphat activators are addingalone separately, such as Na₂SO₄、CaSO₄·0.5H₂O and CaSO₄, they all have a certainexcitation effect, and the excitation effect of CaSO₄·0.5H₂O is the best. Thirdly, the effects of different activators adding together on slag-cement gelsystem will be analyzed through the tests of the concrete steam-cured strength. Theresults show that binary mixed alkaline activators play a role of negative effects on theconcrete steam-cured strength; binary mixed sulphat activators play a role of positiveeffects on the concrete steam-cured strength; binary mixed alkaline and sulphatactivators play a role of negative effects on the concrete steam-cured strength; under thesame conditions, ternary mixed CaO, Na₂SO₄, and CaSO₄·0.5H₂O has the bestexcitation effect on slag-cement gel system, they can make the concrete steam-curedstrength15%more than the benchmark.Finally, the activation mechanism of different kinds of activators on theslag-cement gel system will be analyzed by X-ray diffraction （XRD） and scanningelectron microscopy （SEM） tests of cement paste samples.