
In the construction industry, concrete is widely used in various engineering structures and plays a pivotal role. The stability of its performance and the reliability of the construction quality are directly related to the safety performance and service life of the building. However, during the actual construction process, a headache problem often occurs, that is, the phenomenon of concrete ‘pseudo-setting’.
This phenomenon not only causes delays in the construction schedule and causes unnecessary trouble for the construction team, but more seriously, it may also lurk in the structure of the project, posing a potential risk to the overall quality.
What is the phenomenon of concrete pseudo-setting?

Pseudo-setting, a term that describes an abnormal solidification or premature hardening of cement in the early stages. Specifically, the mixture shows signs of setting quickly within just a few minutes after the cement is mixed with water. It is important to note that there is a clear difference between pseudo-setting and rapid-setting, despite their similar appearance. During pseudo-setting, very little heat is released, and through vigorous stirring, the seemingly set paste can be returned to its plastic state, and the setting process can continue according to the normal time progression. This process does not have a negative impact on the final strength of the cement. In contrast, rapid or flash setting, which is usually caused by insufficient retarder, is very different. In this case, the mortar will quickly gain a certain strength in a short period of time, and once it reaches this state, even if you try to remix it, it will not be able to return to a plastic state.
After the phenomenon of pseudo-setting occurs, if the mortar is remixed, we will find that the depth of penetration of the Vicat needle when inserted into the mortar changes in a way similar to that in the normal setting process. This indicates that the pseudocohesive slurry can regain its original workability after remixing. However, the situation is quite different in quick-setting cement. Even after remixing, the insertion depth of the Vicat needle hardly changes, which reflects that the quick-setting cement slurry has quickly gained a high strength and it is difficult to restore its plasticity through simple stirring. Therefore, although both pseudo-setting and rapid-setting are problems that may be encountered during the use of cement, the impact of pseudo-setting is relatively minor. Nevertheless, pseudo-setting can still cause some disruption and difficulties in the construction process, and requires our attention and prevention in practical operations.
The occurrence of pseudo-setting is closely related to a variety of factors. In addition to conditions such as a high content of C3A in the clinker and excessive gypsum admixture, it is generally believed that the high temperature to which the cement is exposed during the grinding process is a major cause. This high temperature environment can cause a large amount of dihydrate gypsum to undergo a dehydration reaction and convert to hemihydrate gypsum. Subsequently, when cement is mixed with water, these hemihydrate gypsum particles will quickly dissolve in the water, and some of them will undergo a hydration reaction again, regenerating dihydrate gypsum and precipitating. These precipitated dihydrate gypsum particles will form a network structure of needle-like crystals, which will cause the slurry to set.
In addition, for some cements with a high alkali content, the potassium sulphate in them can react with the gypsum dihydrate in a specific way. Specifically, potassium sulphate reacts with gypsum dihydrate to form calcium potassium sulphate and water, and this reaction process further exacerbates the occurrence of false setting. Therefore, in the production and use of cement, strict control of various factors is necessary to avoid the adverse effects of false setting on project quality.
In general, the formation of pseudocement is a complex physicochemical process involving multiple factors such as cement composition, grinding conditions, temperature and moisture. In order to effectively prevent and solve the problem of pseudocement, we need to gain a deeper understanding of the interaction of these factors and take corresponding measures to optimise and control them.
The rapid growth of the resulting pseudogesso crystals can also be an important cause of pseudocuring. These rapidly growing crystals form a barrier in the slurry, interfering with the normal setting process. In addition, we have also noticed that even if a network structure consisting of crystals such as dihydrate gypsum is not formed in the slurry, abnormal setting may still be observed.
Researchers have come up with a new theory to explain this complex situation. They believe that the surfaces of cement particles may carry opposite charges for specific reasons. This charge distribution is inherently thixotropic, which means that it can trigger particle-particle interactions under certain conditions, leading to pseudocaking. This explanation provides a new perspective on the causes of pseudocaking and may provide clues for us to find more effective prevention and solutions.
Practical experience shows that the occurrence of pseudocaking is significantly reduced in cement mixed with other materials. In order to effectively prevent the dehydration of dihydrate gypsum during production, a series of necessary cooling measures are often taken during cement grinding. In addition, using gypsum with a higher content of anhydrous calcium sulfate as a raw material is also an effective way to reduce the occurrence of false setting. In addition to these adjustments in the production process, storing the cement under appropriate conditions for a period of time, or appropriately extending the mixing time when preparing the concrete, can also help eliminate the occurrence of false setting.
Causes of false setting in concrete

1. Cement quality issues
Cement is the core cementitious component of concrete, and its quality has a decisive impact on the overall performance of concrete. When cement contains excessive fine powder, alkali metal oxide or other impurities, these components may accelerate the chemical reaction between the cement and water, resulting in the formation of a large amount of hydration products in a relatively short period of time. This rapid hydration reaction often causes the phenomenon of false setting, which brings unnecessary trouble to construction. In addition, the freshness of cement is also a factor that should not be ignored. Expired or damp cement is more likely to have the problem of false setting because its internal chemical composition may change.
2. Improper use of admixtures
The use of admixtures has become an important means of improving the workability of concrete in various aspects of concrete construction. However, this improvement is not flawless, as the selection and use of admixtures requires a high degree of accuracy and rationality. Once the admixture is used improperly, such as overusing certain accelerators or early strength agents, it may disrupt the balance of the hydration reaction of the cement and accelerate the process. This accelerated reaction can cause the concrete to lose its proper fluidity in a very short period of time, which in turn can lead to the phenomenon of false setting.
3. Construction environment
The variability of the construction environment is a factor that cannot be ignored in concrete construction, especially its potential impact on the phenomenon of pseudo-setting. Specifically, when the construction environment is in high temperatures, low humidity or windy conditions, these extreme environmental factors can significantly accelerate the evaporation of moisture from the surface of the concrete. With the rapid loss of water, a hard crust will quickly form on the surface of the concrete, while the interior may remain in a plastic state. This condition of hardened surface and incomplete setting is typical of the phenomenon of pseudo-setting.
4. Mixing and transportation problems
In the mixing and transportation of concrete, time management and mixing speed control are particularly critical. If the mixing time is too long or the mixing speed is insufficient, cement particles may settle and stratify. This uneven mixing state not only interferes with the normal hydration reaction of the cement, but may also be a trigger for the phenomenon of false setting. In addition, management during transportation is also very important. If the concrete is subjected to excessive vibration or impact during transportation, its internal structure may change, resulting in abnormal interaction between cement particles and thus causing false setting.
How to prevent and solve the phenomenon of concrete pseudocementation?

1. Strictly control the quality of cement
Ensuring the quality of cement is good and fresh without impurities is the primary task for effectively preventing the phenomenon of concrete pseudocementation. Before construction, a comprehensive quality inspection of the cement must be carried out to verify whether it meets industry standards and engineering requirements. This step is crucial, because only high-quality cement can ensure the stability and reliability of concrete during construction. At the same time, the storage environment of cement should not be ignored. It is important to ensure that the storage area is dry, ventilated, and away from moisture and sources of pollution to prevent the cement from deteriorating due to moisture or contamination. In addition, regularly checking the storage status of the cement and disposing of expired or damp cement in a timely manner are also important measures to ensure the quality of the cement. Through these strict quality control measures, we can effectively reduce the occurrence of false setting of concrete, thereby ensuring construction quality and project safety.
2. Reasonable use of admixtures
In concrete engineering, the proper use of admixtures is crucial. When selecting admixtures, the specific needs of the project and the conditions of the construction site must be fully considered to ensure that the selected admixture is suitable for the actual situation. In particular, caution should be exercised when using accelerators and early strength agents, as excessive use of these admixtures can significantly accelerate the hydration reaction of the cement, which may cause the concrete to harden too quickly, thereby increasing the risk of false setting. At the same time, the process of mixing admixtures also requires strict control to ensure that the admixtures are evenly distributed in the concrete to ensure uniformity and consistency in the overall performance of the concrete. By taking these measures, the problem of false setting caused by improper use of admixtures can be effectively reduced, and the quality and reliability of concrete engineering can be further improved.
3. Optimise the construction environment
In order to effectively deal with the impact of adverse construction environments such as high temperatures, low humidity or strong winds on concrete, optimising the construction environment has become a key task. When working in these extreme conditions, effective measures must be taken to reduce the rate of evaporation from the concrete surface. For example, the concrete surface can be covered with a damp cloth to form a protective barrier and reduce direct evaporation. Another effective method is to spray a moderate amount of water mist to increase the humidity of the air and keep the concrete surface moist. These measures can not only significantly slow down the drying rate of the concrete surface, but also reduce the occurrence of false setting.
In addition, it is also crucial to arrange the construction time properly. The construction unit should pay close attention to the weather forecast and avoid concrete construction in extreme weather conditions. By choosing the appropriate construction period, the impact of adverse environmental factors on the quality of concrete can be effectively avoided. The comprehensive application of these measures will create a more favourable environment for concrete construction, thereby ensuring the stability and reliability of construction quality.
4. Improve mixing and transportation methods
In order to further improve the quality of concrete and reduce the occurrence of pseudo-setting, we must carefully optimise the mixing and transportation methods. First, the mixing process should ensure moderate timing and uniform speed to avoid the settlement and stratification of cement particles. Through precise mixing control, we can achieve thorough mixing of cement, aggregate and other additives to ensure the uniform distribution of concrete components.
Second, in the transportation process, we need to pay special attention to reducing the impact of vibration and impact on concrete. Excessive vibration can lead to damage to the internal structure of the concrete, which can cause problems such as false setting. Therefore, it is important to choose the right transport equipment and route. For concrete transported over long distances, we can adopt the strategy of mixing and transporting in batches. This method not only maintains the workability of the concrete, but also effectively reduces the changes in concrete properties caused by long-distance transportation.
In summary, by improving the mixing and transportation methods, we can better ensure the quality of the concrete, reduce the risk of false setting, and provide strong support for the smooth progress of the project.