Studies on Good Use of Inferior-Quality Aggregates in Concrete Structures for Agriculture

为了更好地利用劣质骨料在农业混凝土结构中的应用，对东北、关东、东海、北国、关西、中部、九州北部和南部的劣质骨料进行了调查。通过试验发现，每个地区的骨料类型都可以作为混凝土材料，通过试验测定其级配、比重、吸水性、安定性、碱集料反应、抗压强度和力学性能。为了控制碱集料反应，在混凝土中掺入少量的灰分，并对掺灰混凝土的碱集料反应进行了研究。为了延长池塘混凝土墙的使用寿命，必须确保不会因水泥在凝结和硬化过程中产生的热量而产生温度应力而产生裂缝。采用有限元方法求解了直角坐标系下的三维导热问题，预测了池塘混凝土墙体的温度分布。采用普通硅酸盐水泥和钢模板的三维有限元模型预测的最高温度和混凝土内部温差分别为39ﾟC和29ﾟC，为了减小最高温度和混凝土内部温差，可以使用硅酸盐高炉水泥B、减水剂和胶合板模板。该模型预测的最高温度为36ﾟC，混凝土内部温差为25ﾟC。该三维模型可用于预测混凝土墙体温度，从而为规划系统的研究提供便利。

In order to make good use of inferior-quality aggregates in concrete structures for agriculture, investigations were carried out on aggregates used for this purpose in Tohoku, Kanto, Tokai, Hokuriku, Kansai, Chugoku, and northern and southern Kyushu.It was found that the types of aggregate in each region could be utilized as materials for concrete from experiments to determine grading, specific gravity, absorption, soundness, alkali-aggregate reaction, compressive strength and mechanical properties.In order to control the alkali-aggregate reaction, a small percentage of ash was mixed with the concrete, and the alkali-aggregate reaction of the ash-mixed concrete was investigated. This confirmed the availability of ash for this purpose.In order to extend the life of farm pond concrete walls, it is necessary to ensure that no cracks form as a result of temperature stresses created by the heat generated in the cement during setting and hardening. A three-dimensional heat conduction problem in a Cartesian coordinate system was solved using the finite element method for predicting the temperature distribution in farm pond concrete walls. The maximum temperature and internal concrete temperature difference predicted by the three-dimensional finite element model using normal Portland cement and a steel form are 39ﾟC and 29ﾟC respectively.In order to reduce the difference between the maximum temperature and internal concrete temperature, Portland blast-furnace cement B, an admixture for reducing the water content and a plywood form may be used. The maximum temperature and internal concrete temperature difference predicted by this model are 36ﾟC and 25ﾟC, respectively. This three-dimensional model should be useful for predicting concrete wall temperatures, thus facilitating the study of planning systems.