The workability of cement concrete refers to the comprehensive properties of cement concrete mixture, such as fluidity, difficulty in segregation and easy tamping. The main factors affecting the workability of concrete are as follows: 1. The influence of cement content and consistency. In order to flow under the action of self-weight or external vibration, the internal resistance of concrete mixture must be overcome. The internal resistance of mixture mainly comes from two aspects, one is the friction between aggregates, and the other is the cohesion of cement slurry. The friction between aggregates mainly depends on the thickness and amount of cement slurry on the surface of aggregate particles. The cohesion of cement slurry mainly depends on the dryness of cement slurry, that is, the consistency of cement slurry Under the condition of keeping the water-cement ratio of concrete mixture unchanged, the more cement slurry is used, the thicker the slurry layer is wrapped on the surface of aggregate particles, the better the lubrication effect is, the friction between aggregates is reduced, and the concrete mixture is easy to flow, so the fluidity is large. On the contrary, it is small. However, if the amount of cement slurry is too much, the amount of aggregate will inevitably decrease, resulting in bleeding and bleeding, which consumes a lot of cement. If the amount of cement slurry is too small, so that the gaps between aggregates can't fill or cover the surface of all aggregates, the mixture will collapse and the cohesiveness will become worse. Therefore, the dosage of cement slurry in concrete mixture should not be too little, but not too much, to meet the liquidity requirements of the mixture. Under the condition of keeping the dosage of concrete cement unchanged, reducing the mixing water consumption will thicken the cement slurry, increase the cohesion of the cement slurry, make the cohesiveness and water retention good, and reduce the fluidity. Increasing water consumption is the opposite. Too little water is added to concrete, that is, the water-cement ratio is too low, which is not only too low in fluidity, but also difficult to form compactness under certain construction conditions because of the convergence and poor cohesiveness of concrete. However, if too much water is added, the water-cement ratio is too large, and the cement slurry is too thin, the mixture will have serious stratification and bleeding, which will seriously affect the strength and durability of concrete. Therefore, it is absolutely impossible to increase liquidity simply by adding water. It is necessary to adjust the fluidity of the mixture by increasing the amount of cement slurry while keeping the water-cement ratio unchanged. From the above discussion, it is clear that both the influence of cement quantity and the influence of cement consistency are actually the influence of water. Therefore, the decisive factor affecting the workability of concrete mixture is the amount of mixing water. Second, the influence of sand ratio sand ratio refers to the percentage of sand quality in concrete to the total sand quality. Sand ratio refers to the combination of sand and gravel in concrete. The change of sand ratio will greatly change the total surface porosity of aggregate, so it has a significant impact on the workability of concrete mixture. When the sand ratio is too large, the total surface area and porosity of aggregate will increase. When the amount of cement slurry in concrete is constant, the surface area of aggregate particles will be relatively thin, the mixture will become dry and thick, and the fluidity will become smaller. If the fluidity remains unchanged, it is necessary to increase the cement slurry, which will consume more cement. On the other hand, if the sand ratio is too small, there are too many stones and too little sand in the mixture, and the amount of mortar formed is not enough to wrap the surface of stones and fill the gaps between stones. When there is not enough mortar lubricating layer between stones, it will not only reduce the fluidity of concrete mixture, but also seriously affect its cohesiveness and water retention, resulting in aggregate segregation, cement slurry loss and even concrete collapse. As can be seen from the above, the sand ratio should not be too large or too small when configuring concrete, because a reasonable sand ratio value should be selected. The so-called reasonable sand ratio refers to the sand ratio value that can make the concrete mixture obtain the maximum fluidity and maintain good cohesiveness and water retention performance under the condition of certain water consumption and cement consumption. Third, the influence of the properties of the constituent materials (1) the influence of cement varieties. The fluidity of concrete mixture mixed with slag cement or pozzolanic cement is smaller than that mixed with ordinary cement under the condition of a certain amount of cement and water. This is because the density of the former cement is smaller, so their absolute volume is larger under the same amount of cement, so the concrete is thicker under the same amount of water. If they want to achieve the same plunge, the former will be thicker every time. (2) The influence of aggregate properties refers to the variety, gradation, particle thickness and surface shape of aggregate used in concrete. Under the condition of a certain amount of concrete aggregate, the fluidity of concrete mixture mixed with pebbles and river sand is better than that mixed with gravel and mountain sand: the fluidity of concrete mixture mixed with graded aggregate is good, but the fluidity of concrete mixture mixed with fine sand is poor, but the cohesiveness and water retention are good. (3) Influence of Additives Adding water reducing agent or air entraining agent to concrete mixture can obviously improve the fluidity, and air entraining agent can also effectively improve the cohesiveness and water retention of concrete mixture, which also plays a very beneficial role in the strength and durability of hardened concrete. Fourthly, the influence of mixture storage time and ambient temperature. As time goes on, the concrete mixture will become more and more dry and thick, and the slump will gradually decrease. This is because part of the water in the mixture is gradually absorbed by the aggregate and part of it is evaporated, as well as the hydration of cement and the gradual formation of cohesive structure. The workability of concrete mixture is also affected by temperature. With the increase of ambient temperature, the slump of concrete will be lost faster, because the water evaporation and chemical reaction of cement will proceed faster. Exchangeability. The main characteristic of concrete is workability. Workability refers to whether concrete is easy to operate, uniform and dense. The factors that affect the workability mainly include the following aspects. 1) water consumption; 2) water cement ratio; 3) sand ratio; 4) Other influencing factors: cement varieties, aggregate conditions, time and temperature, additives, etc. (2) Mechanical properties of ordinary concrete structures. 1) compressive strength and strength grade of concrete. Concrete strength includes compressive strength, tensile strength, bending strength and shear strength, of which compressive strength is the highest, so concrete is mainly used for compressive strength. 2) Compressive failure characteristics of ordinary concrete. The compressive failure of concrete mainly occurs at the interface between cement stone and aggregate. Before concrete loading, there are actually small cracks on the interface between coarse aggregate and cement stone. . 3) Factors affecting the strength of concrete. The main factors affecting the strength of concrete are: (1) cement strength and water-cement ratio. Age. (c) Curing temperature and humidity. (d) Construction quality, which is the basic factor affecting the strength of concrete. 4) Measures to improve concrete strength. The measures to improve the strength of concrete are: using high-strength cement, using hard concrete mixture, using moist heat treatment (steam curing and autoclaving curing), improving TT technology, strengthening mixing and vibrating (using new technologies such as concrete mixing water magnetization and concrete mixing stone), and adding additives (such as adding water reducer and early strength agent). (3) Deformation characteristics of ordinary concrete. 1) chemical shrinkage. 2) Wet and dry deformation. 3) Temperature deformation. 4) Deformation of concrete under load. Concrete deformation can be divided into elastic deformation and plastic deformation. Creep refers to the deformation of concrete that increases with time under continuous load, which is called creep. Creep deformation increases rapidly in the initial stage, then gradually slows down, and generally lasts for 2 ~ 3 years before it gradually stabilizes. But how to improve the workability of concrete There are several methods often used in the construction process: 1. When the slump value is less than or greater than the design requirements, increase or decrease the dosage of cement slurry under the condition of constant water-cement ratio, or decrease or increase the dosage of coarse and fine aggregate proportionally under the condition of constant sand ratio. 2。 Select the best sand ratio. 3。 Improve the gradation of sand and gravel. 4。 Minimize coarse sand and gravel. 5。 Increase the amount of cement slurry. 6。 Use additives (water reducer, plasticizer). So ... . . . The above information is for reference only.