鋼纖維應用於自充填混凝土之研究

Abstract

混凝土為目前營建工程中使用最普遍且最廣泛的材料，但混凝土屬於脆性材料且具有抗拉強度及抗彎能力較弱等缺點，故必須與鋼筋搭配使用，但混凝土水化過程中會因為溫度變化、體積變化及化學作用等影響產生裂縫，加快鋼筋腐蝕速度，而添加纖維可有效抑制混凝土裂縫形成及控制裂縫持續擴張情形，使混凝土由脆性破壞轉變為具有韌性及延展性，進而提升混凝土基本力學性能，發展成不易產生裂縫的複合材料。 本研究測試添加鋼纖維於自充填混凝土中，藉由鋼纖維提供優異的抗拉及抗彎能力與晚期卜作嵐反應形成緻密填充效果，以提升自充填混凝土的基本力學性能。試驗中使用不同鋼纖維含量製作不同水膠比之試體，均以飽和石灰水養護至齡期，待達齡期1-7、14、28、56、90天時，依據試驗所得之工作性、抗壓、劈裂、抗彎強度、收縮應變及表面電阻率，觀察鋼纖維試驗組與基準組間關係，並探討抗彎試驗中，其試體中點位移、裂縫深度及裂縫寬度的開裂行為。 由試驗結果得知添加鋼纖維對於各齡期之抗壓強度、劈裂強度、抗彎強度皆有正面助益，強度會隨纖維含量增加而逐漸提升，但鋼纖維對抗壓強度的助益有限；鋼纖維確實具有良好的收縮抵抗及韌性提升的作用，且水膠比愈低其抑制收縮變形的效果愈好。

Concrete is currently the most commonly and widely used material in construction engineering. However, concrete belongs to brittle material and also has disadvantages, including low tensile splitting strength and bending strength. Consequently, it has to be used along with steel. But another question is that it will produce cracks owing to the change of heat, volume, and chemical action during the hydrated reaction of cement, accelerate steel corrosion rate. Therefore, adding fiber can effectively suppress crack formation and control continued expansion cracks, make concrete from brittle failure to have toughness and ductility, and thus enhance the basic mechanical properties of concrete to develop into a composite material not easily to have cracks. This project devotes to testing about adding steel fiber into Self-Compacting Concrete(S.C.C.), with steel fiber providing excellent tensile splitting strength and bending strength, along with lately Pozzolan reaction to form a dense filling effect, and promote the basic mechanical properties of Self-Compacting Concrete. Among the test, we use different steel fiber contents to product different water cementitious ratio test specimens, all of these are cured in saturated lime water until the age of concrete reach( age : 1~7 , 14 , 28 , 56 , 90), then we test their workability, compressive strength, tensile splitting strength, bending strength, volume stability, and surface electric resistance, to observe the relationship between the fiber experimental group and the basic group, and investigate test specimens of displacement, crack depth, crack width to the behavior of cracking among the bending test. According to the test results, we know that adding steel fiber is definitely workable for any ages of compressive strength, tensile splitting strength, bending strength. Strength will gradually grow up with increasing fiber content, but steel fiber has limited useful to compressive strength conversely. Steel fiber does have good shrink resistance and offer toughness. Also, the lower water cementitious ratio it is, the better effect of suppressing shrinkage it will be.