Applicability of high carbon ferrochromium slag as an aggregate for ultra high strength concrete

为了将高碳铬铁渣作为超高强度混凝土的骨料，研究了高碳铬铁渣的矿物学组成及其在胶凝基质中的碱反应性。从特征微观结构和微观破坏两方面研究了其反应性和表面纹理对高强砂浆和RPC （Reactive Powder Concrete：超高强混凝土）力学性能的影响。本研究的主要结果如下：(1)高碳铬铁渣与水泥浆体基质具有潜在的反应性。(2)矿渣与碱性水泥基体的反应不会导致混凝土因碱硅反应而变质。(3)渣粒的反应和粗糙的组织有助于提高粘结强度和抗裂纹扩展能力。(4)水胶比极低的硅灰砂浆在水中固化时，收缩和膨胀同时发生。(5)低水胶比砂浆发生微裂缝的机理应考虑水泥水化后期产生的内部膨胀压力。(6)矿渣可作为超高强度混凝土的骨料。然而，掺矿渣混凝土的最佳配合比和热处理可能与天然骨料混凝土不同。熔渣中二氧化硅的溶解影响结晶反应产物的生长及其形貌。

In order to use high carbon ferrochromium slag as an aggregate for ultra high strength concrete, mineralogical compositions of the slag and its alkali reactivity in cementitious matrix are investigated. Effects of its reactivity and surface texture on mechanical properties of high strength mortars and RPC (Reactive Powder Concrete : ultra high strength concrete) were investigated in terms of characteristic microstructures and microscopic failures. The major outcomes in this study are as follows.(1) The high carbon ferrochromiurn slag has the potential reactivity with cement paste matrix.(2) The reaction of the slag with alkaline cement matrix does not result in the deterioration of concrete due to alkali silica reaction.(3) The reaction and rough texture of the slag particles contribute to the increase in bond strength and crack growth resistance.(4) When silica fume mortars with an extremely low water/binder ratio were cured in water, shrinkage and swelling occurred simultaneously.(5) Generation of internal expansive pressure due to the late cement hydration should be taken into account as a mechanism to cause maicrocracks in mortars with low water/binder ratios.(6) The slag can be used as an aggregate for ultra high strength concrete. However, the optimum mix proportion and the thermal treatment for the concrete with the slag may be different than those for concretes with natural aggregates. Dissolution of silica in the slag affects the growth of crystalline reaction products and their morphology.