The water-cement ratio refers to the weight ratio of the water consumption in the concrete mixture to the cement consumption, and in the case of the determination of the constituent materials, the water-cement ratio is the main parameter that determines the strength, durability and a series of other physical and mechanical properties of the concrete. 
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(1) The influence of water-cement ratio on the strength of concreteThe size of the water-cement ratio directly affects the size of the concrete strength, when the water-cement ratio is larger, the cement particles in the concrete mixture are relatively less, the distance between the particles is larger, and the colloid produced by hydration is not enough to fill the void between the particles, in addition, the excessive water evaporates and leaves more water air, so that the concrete strength is reduced. On the contrary, the water-cement ratio is small, the distance between cement particles is small, the colloid produced by cement hydration is easy to fill the void between the particles, and the water space left after evaporation is also low, and the concrete strength is high. However, the water-cement ratio is too low, resulting in too little water, cement hydration is difficult, part of the cement can not be fully hydrated, and it is not conducive to the improvement of strength. (2) The influence of water-cement ratio on the workability of concrete
The water-cement ratio decreases, the slurry consistency increases, the mobility of the concrete mixture decreases, the mixture is astringent, and it is difficult to vibrate and compact. At this time, more admixtures are needed to improve workability and improve the construction performance of concrete. The water-cement ratio becomes larger, the consistency of the slurry becomes thinner, although the fluidity increases, the cohesion and water retention become poor, the sinking speed of the aggregate becomes faster, and the concrete mixture is easy to produce delamination, segregation and water leakage, which seriously affects the strength and durability of concrete.
(3) The influence of water-cement ratio on the durability of concrete
Concrete durability is the ability of concrete to resist various physical and chemical damage in the use environment, which directly affects the safety and performance of the structure, including impermeability, frost resistance, chemical erosion and alkali aggregate reaction, etc., and the water-cement ratio plays a key role in the durability of concrete.
1) Effect on concrete carbonization.
Concrete carbonization refers to the process of CO2 diffusion from the air to the concrete, and the carbonization rate is affected by the amount of cement or the Ca(OH)2 content in the cement stone and the compactness of the concrete. On the one hand, the smaller the amount of cement in concrete, the less the amount of Ca(OH)2 produced by hydration, the less resistance to diffusion, and the faster the carbonization rate. On the other hand, the water-cement ratio increases, the porosity of concrete increases, the compactness decreases, and the carbonization rate increases. On the contrary, the water-cement ratio is reduced, the compactness of the concrete is enhanced, the porosity is reduced, and the carbonization rate is slower.
2) Effect on chloride diffusion.
The size of the water-cement ratio has an important impact on the ability of concrete to resist chloride ion diffusion, and the larger the water-cement ratio, the greater the chloride ion binding capacity of concrete.
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3) Effect on anti-osmosis.
Impermeability refers to the ability of concrete to resist the infiltration of water into the concrete capillary pores, generally speaking, the smaller the concrete water-cement ratio, the higher the compactness, the better the impermeability. The larger the water-cement ratio, the more interconnected and irregular capillary pores in the concrete, the porosity of the cement stone increases, and the permeability is strong, when the water-cement ratio is greater than 0At 6 o'clock, the impermeability of concrete increases dramatically. However, too small water-cement ratio is not conducive to the full hydration of cement, and the compactness will also be reduced, and the permeability will increase. In the water level change areas such as hydraulic building foundations, water retaining and overflow buildings, wing walls, etc., the water-cement ratio during construction should be strictly controlled, generally at 038～0.Between 4.
4) Anti-freeze effects.
The frost resistance of concrete refers to the performance of concrete that it does not fail and its strength is not significantly reduced after being subjected to multiple freeze-thaw cycles under service conditions. The influence of water-cement ratio on the frost resistance of concrete has the following points: firstly, the water-cement ratio is too large, and the sinking rate of aggregates with different particle sizes is different in the vibration process, resulting in the stratification of slurry and aggregate, more cement slurry floats on the surface, the wear resistance is poor, and the concrete is easy to form surface erosion when it is damaged by freezing and thawing. Therefore, in alpine areas, especially in the frozen environment with water contact, the water-cement ratio of concrete should be appropriately reduced to improve the frost resistance. Secondly, the size of the concrete bubble and the spacing of the bubble decrease with the decrease of the water-cement ratio, and increase with the increase of the water-cement ratio. In the case of similar air entrainment of concrete, the larger the water-cement ratio and the larger the spacing of bubbles, the worse the frost resistance of concrete. Finally, as the water-cement ratio increases, the total volume and pore size of the internal pores of the concrete become larger and larger, and the ice expansion pressure and osmotic pressure generated in the freeze-thaw process are larger, and the frost resistance of the concrete will inevitably decrease.
(4) The influence of water-cement ratio on concrete cracks
The larger the water-cement ratio, on the one hand, the more moisture in the concrete mixture, the more water evaporates, and the greater the shaping shrinkage generated. On the other hand, the increase of the water-cement ratio will prolong the coagulation time of the concrete mixture, prolong the generation time of the force of concrete to resist plastic shrinkage, weaken the force of resisting plastic shrinkage, and the concrete is prone to cracks. When the water-cement ratio is low, the homogeneity and cohesion of the concrete become better, the plastic settlement is smaller, and the width and total area of plastic shrinkage cracks are smaller. Therefore, under the condition of meeting the construction requirements, the water-cement ratio should be reduced as much as possible.
(5) The influence of water-cement ratio on concrete shrinkage
The shrinkage of concrete is made up of two parts: the volumetric shrinkage of the cement gel itself (so-called condensation) and the volumetric shrinkage (so-called dry shrinkage) caused by the loss of water from the concrete. The size of the water-cement ratio has a great influence on the dry shrinkage of concrete, and the larger the water-cement ratio, the greater the dry shrinkage. The water-cement ratio is 06. The concrete shrinkage value ratio is 04 increases the shrinkage by about 40%. The greater the water consumption of the concrete mixture, the greater the dry shrinkage, and it is necessary to use admixtures to control the water-cement ratio and workability. The smaller the water-cement ratio, the higher the temperature of the concrete due to hydration, the greater the early temperature deformation value, the self-shrinkage of the concrete and its rate increase with the small water-cement ratio, and the low water-cement ratio will produce a large self-shrinkage in the early stage of concrete hardening.