Investigation on Frost Deterioration of Concrete Using Limestone Coarse Aggregate

虽然石灰石具有吸水率低、比重高的特点，但人们认为石灰石粗集料混凝土的冻融耐久性低于好的粗集料混凝土。本文研究了掺石灰石骨料混凝土的冻融耐久性。研究结果表明：(1)根据以往的试验研究，粗集料的基本性质并不能很好地解释混凝土的冻融耐久性。(2)根据石灰石粗集料的基本性质试验结果，石灰岩具有吸水率低、比重高、热系数低、石粉含量高的特点。(3)粗集料与砂浆之间温度系数的差异产生了温度应力，而石灰岩的低温度系数导致了较大的温度应力。认为温度应力影响混凝土的冻融劣化。(4)对于混凝土而言，石粉的存在具有降低含气量和提高冻融耐久性的作用。(5)不同体积的冻融试验和粗集料的表面积测定。认为温度应力大小对混凝土耐冻性影响不大。当粗骨料的数量变大时，混凝土的抗冻性变小。认为影响混凝土抗冻耐久性的裂缝数量变少。裂缝的数量被认为影响混凝土的冻融耐久性。

Although limestone is characterized by low water absorption and high specific gravity, it is said that frost durability of concrete with the limestone coarse aggregate is lower than concrete with the good coarse aggregates. In this paper, frost durability of concrete with the limestone aggregate is investigated. Results are shown as follows:(1) According to the investigation of the past experiments, frost durability of concrete was not explained satisfactory by the basic property of coarse aggreegate.(2) According to the test results of the basic property test of the limestone coarse aggregate, the limestone is characterized by low water absorption, high specific gravity, low thermal coefficient and high content of stone power.(3) Differences of the thermal coefficient between the coarse aggregate and mortar cause thermal stress, and the low thermal coefficients of limestone cause large thermal stress. It is thought that the thermal stress affects frost deterioration of concrete.(4) For concrete, an existence of stone powder has effects of reducing air content and improving frost durability.(5) Freezing and thawing tests varied volume and the surface area of the coarse aggregate was conducted. It is thought that the effect of the thermal stress magnitude on frost durabllity of concrete is small. When the number of the coarse aggregate becomes large, frost durability of concrete becomes small. It is thought that number of cracks affect frost durability of concrete becomes small. It is thought that number of cracks affect frost durability of concrete.