Research on Concrete Temperature Control and Crack Prevention for Pumping Station Complicated Structure

Abstract

The water passageway structure of pumping station is both mass concrete structure and complicated structure. Cracks always appear in these areas during construction period. It will shorten the building life, and endanger the safety of pumping station. Three dimensional finite element method is adopted to simulate the temperature field and stress field of pump station in construction. The considering loads include gravity, temperature, autogenous volume deformation, and creep. The temperature and the first principle stress duration curves of easily cracking area are analyzed in different cases. After optimization of different temperature control measure, the tensile stress of different areas in early age or later age can be controlled lower than tension strength, and the cracking prevention safety factor can be raised. It is found that pipe cooling, surface insulation, pouring intermission, structure constrains can change the tensile stress obviously for pumping station. The influence of these factors is separately concluded.

The Cracking Mechanism and Anti-Cracking Measures for Hydraulic Mass Concrete

“…The microscopic cracks are mainly divided into gelling crack, cement cracks and aggregate cracks, and the generation mechanism of different kinds of cracks is different. Microscopic crack is inevitable, and it has characteristics such as nonpenerability and irregular distribution, however, microscopic cracks will not affect the stability of structure [2].…”

“…The Design of Concrete Raw Materials The Choices of Cement Type. While concrete is concreting, adiabatic temperature rising will reduce if we choose low hydration heat cement [9] . The Design of Cement Dosage and Unit Water-Use.…”

“…The Optimization of Aggregate Gradation and Mixture Ratio. A good grading of aggregate can reduce the unit water use and dosage of cement the, even can improve the tensile properties of concrete [2] [10]. Proper mixture ratio can effectively improve the compactness and peaceability of concrete, and reduce the generation of temperature cracks, the desiccation cracks and the shrinkage cracks [10].…”

“…Water reducing agent is an important measure to reduce the hydration heat and the generation of cracks. Air-entraining agent can introduce a large number of evenly distributed , stable and closed tiny air bubbles in the process of mixing with concrete, the bubbles make the concrete elastic modulus decrease, and they are good for improving crack resistance of concrete [9]. When the air content of concrete keeps 4 %, it will have a good effect on the prevention of cracks [10].…”