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Using admixtures to replace part of cement can effectively reduce environmental pollution. Many concrete gravity dams have been planned for Tibet, where the resource of fly ash (FA) is scarce but the resource of tuff is abundant. Compared with the more mature and widely used FA concrete in gravity dams, the application of tuff concrete is rare, and the hardening mechanism of the cement–tuff binary cementation system and the performance of tuff concrete still need to be further studied. In view of this, the hydration and hardening mechanism of the cement–tuff binary cementation system using varying percentages of tuff contents (0%, 25%, and 50%) are discussed, and the mechanical properties (e.g., strength, modulus) and durability performance (e.g., freeze-thaw, carbonization) of tuff normal concrete are investigated in this paper. The microstructure of the cement–tuff system shows that additional tuff powder promotes the hydration of clinker in cement, which increases the calcium hydroxide content [ Ca(OH)2 ] and leads to a higher porosity at early curing age. Results show that the amount of tuff content is almost positively correlated with porosity. The additional tuff in concrete increases the earlier splitting tensile strength, ultimate tensile value, and drying shrinkage, which also slightly reduces the frost resistance and little affects the compressive strength, tensile strength, elastic modulus, impermeability, and carbonation depth. Tuff normal concrete shows better performance than FA concrete in some aspects. The results show that tuff materials can be used to replace FA, and tuff normal concrete can be applied to the construction of concrete gravity dams in areas where fly ash is scarce and tuff is abundant. [ABSTRACT FROM AUTHOR]

The primary aim of this research was to analyze the seismic performance of the Guoduo gravity dam. A nonlinear FEM method was implemented to study the deformation, stress, and overall stability of dam under both static and dynamic loading conditions, including both normal and overloading conditions. A dam seismic failure risk control method is proposed based on the cracking mechanism induced by the dynamic load to ensure dam safety and stability. Numerical simulation revealed that (1) under normal static and dynamic loading the symmetry of the displacement distributions is good, showing that the dam abutments and riverbed foundation have good overall stiffness. The stress distribution is a safe one for operation under both normal water loading and seismic loading. (2) Attention should be paid to the reinforcement design of outlets of the diversion dam monoliths, and enhance the capability of sustaining that tensile stress of dam monoliths. (3) The shape of the dam profile has a significant effect on the dynamic response of the dam. (4) By employing the “overload safety factor method,” the overall seismic fortification is as follows: K1=1.5, K2= 2~3, and K3= 3~4. [ABSTRACT FROM AUTHOR]

• Rock-filled concrete technology is new in mass concrete construction. • Hydration temperature rise of rock-filled concrete is lower than normal concrete. • Rock-filled concrete dam is easy to crack in high-altitude and cold regions. • Proposed temperature control measures of RFC dam in High-altitude and Cold Regions. High-altitude and cold regions (HACR) have extremely low temperatures accompanied by frequent cold currents in winter, causing significant thermal stress and cracking in concrete structures. Based on previous studies, by using ABAQUS as the development platform and FORTRAN as the development tool, a calculation program for temperature fields during concrete dam construction and operation processes was established to test the accuracy of the program. Jinqiao Rock-filled Concrete (RFC) Gravity Dam, located in HACR of Tibet, China, is as an example to simulate the thermal stress under three working conditions. The results show that: (1) the hydration temperature rise of RFC is lower than that of normal concrete; the use of RFC can reduce the temperature and thermal stress of the concrete dam. (2) In HACR, installing an insulation layer on the surface of the dam body can significantly increase the surface temperature and reduce its difference and tensile stress, meeting the requirements of temperature control and crack prevention. [ABSTRACT FROM AUTHOR]