以微觀力學模式探討混凝土材料之彈性模數

混凝土為非均質之複合材料，其彈性行為是一個值得研究的課題。由本校（國立宜蘭技術學院）土木材料實驗室所執行混凝土抗壓試驗的數據結果發現，對於各種不同強度之混凝土材料，其實際量測所得之彈性模數值，不僅低於各種理論方法之預測值，甚至往往亦比現今常用經驗式之預測值為低，因此混凝土材料之彈性模數須要進一步之驗證與研究。混凝土材料乃為由水泥糊體將不同性質之粗細骨材，膠結而成之複合材料。當混凝土材料受到力量的作用時，水泥糊體及骨材將共同分擔此力量。因此，相對應之變形量便應該與骨材之空間幾何排列及骨材相互接觸區間之行為有關。所以，建立一個新的模式來探討混凝土材料之彈性模數時，顆粒微觀力學理論乃是合宜之工具。本研究所提出之微觀力學模式，與傳統連體力學方法之不同，在於本微觀力學模式將混凝土材料中之骨材視為獨立之顆粒，而由黏結材料給予膠結之。基於應用微觀力學理論於混凝土材料之考量，本研究將混凝土材料之微觀結構簡化為兩相：黏結材料及骨材顆粒。本研究首先將對混凝土材料之配比設計方法進行整理歸納，對各種不同強度之混凝土進行有系統之足量試驗，以獲得可靠具代表性之實測結果。混凝土材料配比設計之整理歸納結果，亦為本研究所提出之微觀力學模式中參數決定時之依據。本研究所提出之微觀力學模式，將可考慮混凝土之組成材料的特質、骨材之空間幾何排列、骨材之平均配位數等資訊，以對混凝土材料之彈性模數作出正確的預測。本微觀力學模式，將可應用於預測混凝土材料應力—應變關係及相關顆粒黏結材料之後續研究。

關鍵字

混凝土；微觀力學；彈性模數；複合材料

並列摘要

Concrete is a composite material made of different constituents. Elastic modulus of concrete is one of the desirable properties to predict. According to the experimental results of the concrete compression tests conducted at the civil engineering material laboratory of National I-Lan Institute of Technology (NIIT), the measured elastic moduli of the concrete with different compressive strength are lower than the predicted results from the theoretical methods. Furthermore, the measured results are also lower than the predicted results from the well-known empirical methods. Concrete consists of cement paste and aggregate particles. When the concrete material is loaded, both cement paste and aggregates share the load. Therefore, the corresponding deformation of concrete takes the packing structure as well as the inter-particle contacts of aggregates into consideration. As a result, the micromechanical consideration is suitable for developing a new model for predicting the elastic modulus of concrete. Compared with the conventional continuum mechanical approach, the proposed model treats the aggregates as discrete particles bound by cementation material. According to the requirement of the proposed micromechanical model for elastic modulus of concrete, this study treats concrete as a simplified heterogeneous material composed of two phases only: binder and particle. This study will review concrete mixed design in order to perform a series of experimental tests for the concrete with different compressive strength and to obtain the representative and reliable measured elastic moduli. The parameters for the proposed model will be determined by the conclusion of reviewing concrete mixed design. The proposed micromechanical model considers the properties of the constituents, the geometry of aggregates, and the coordination number. Therefore, the proposed model is capable to predict the reasonable elastic modulus of concrete. The proposed model can be applied to predict the stress-strain relation of concrete as well as be used for further study of cemented materials.

並列關鍵字

Concrete ； Micromechanical model ； Elastic modulus ； Composite material

國際替代計量

以微觀力學模式探討混凝土材料之彈性模數

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