# Early-Age Cracking in Concrete: Causes, Consequences, Remedial Measures, and Recommendations
## 4 Factors Affecting Early-Age Cracking
### Materials and Mix Parameters  
The mixing of cement and water liberates hydration heat that causes thermal stress. Thermal stress, as a result of temperature variations, may exceed the early-age strength of concrete and lead to cracking. It is therefore necessary to study the relationship between strength development, modulus of elasticity, and the coefficients of thermal expansion and contraction to predict cracking [36]. Some researchers deduced that the cement type and content can play an important role in improving the performance of concrete, because the generation of hydration heat substantially depends on the type of cement and cement content [9; 12; 42; 43; 44]. Different types of cement exhibit unique fineness characteristics and efficiency in terms of dispersion [12]. The lowest cement content produces the lowest drying shrinkage [36]. The particle size of cement also influences its reactivity with water. The hydration process is faster with finer cement particles, resulting in the earlier setting of concrete [25; 45]. [PERSON] et al. [46] reported that CEM I and CEM III slag cements (CEM: calcium-enriched mixture) are more susceptible to autogenous shrinkage cracking in mortar, which was also confirmed by the denser network of microcracking observed through scanning electron microscope (SEM) analysis. However, [PERSON] et al. [44] pointed out that higher hydration heat does not necessarily lead to deformation and cracking, but increases the risk of cracking in concrete. Meanwhile, [PERSON] and [PERSON] [47] found that using different cement types in higher strength classes with almost equal water-to-cement ratio causes no significant difference in the cracking tendency. The water content of concrete also plays an important role in concrete cracking. The compressive strength increases and the drying shrinkage strain decreases for a concrete with lower water-to-cement ratio [48; 49]. However, a common problem in concrete with low water-to-cement ratio is autogenous shrinkage, which happens due to self-desiccation when the water-to-cement ratio is lower than 0.42 [50]. Conversely, when the water-to-cement ratio is increased, the concrete becomes more prone to bleeding [24]. There are larger amounts of fine particles in low-bleed concrete mixtures compared to high-bleed concrete. High-bleed concrete may produce greater differential settlement because it causes lower paste mobility and capillary pressure build-up. The potential of plastic settlement cracking increases because of the capillary pressure build-up, which increases the amount of vertical settlement [37]. Additional materials, such as mineral admixtures, water reducing admixture, shrinkage compensating cement, shrinkage reducing admixture, and self-compacting admixture have been used to improve concrete performance. The early-age cracking of concrete can be decreased by increasing the maximum allowable internal temperature difference before cracking and minimizing the thermal dilation effect of concrete, especially in mass concrete structure. [PERSON] et al. [51]found that the concrete produced with blending 50% Portland cement, 30% slag, and 20% fly ash performed better than the concrete containing 100% Portland cement, or the concrete with 35% Portland cement substitution with fly ash, or the concrete with 50% Portland cement substitution with ground granulated blast-furnace slag. Also, shrinkage reducing admixtures and self-compacting admixtures could reduce the drying shrinkage of concrete with the provision of adequate moist or wet curing [52] and decrease the surface tension of water [12]. They also produce lower heat of hydration, which reduces the thermal shrinkage of concrete [36]. However, it is not only the amount of hydration heat that may cause early-age cracking due to thermal gradient, particularly in massive structures. The diffusion of heat of hydration could also play a vital role. High-performance concrete has higher risk than the other concretes, because of the smaller hydration heat diffusion length [39].