# Early-Age Cracking in Concrete: Causes, Consequences, Remedial Measures, and Recommendations
## 3 Causes of Early-Age Cracking
At the early stage, when the concrete is still soft, autogenous shrinkage is only attributed to the chemical changes driven by cement hydration, but at a later stage (after approximately 5 h), it is mostly due to self-desiccation, which is intensified by certain mix ingredients (silica fume and superplasticizer) and low water-cement ratio [24]. Therefore, there is a higher risk of autogenous shrinkage in high-strength and high-performance concretes. Higher coarse aggregate content, the use of very fine and high-angularity sand, poor aggregate gradation, incompatible mineral and chemical admixtures, inadequate curing, delayed finishing, high rate of evaporation from concrete surface, and sudden temperature drop are the major causes of plastic shrinkage cracking. Plastic settlement is one of the common causes of early-age cracks in hardened concrete. The vertical settlement of solid particles and the associated vertical restraint result in differential settlements. Moreover, during the casting of concrete, bleed water moves to the surface, while solid particles settle downwards because of gravity. If the concrete is locally restrained from settling, the settlement of solid particles induces stress. When this stress exceeds the strength of fresh concrete, cracking will happen at the source of restraint [25]. Increased coarse aggregate fraction, the presence of very fine sand, poor aggregate gradation, incompatible chemical admixtures, deficient curing, excessively hot conditions, inappropriate control joints, too large joint spacing, and abrupt temperature changes are the main reasons of random cracking in concrete elements [1]. Early loading, the use of dry concrete mixture, poor aggregate gradation, the incorporation of very fine and highly angular sand, inappropriate materials combination, ineffective curing, improper design dimensions, defective joint design, differential support conditions, an excessively hot ambient environment, and rapid temperature decrease are the major reasons of longitudinal cracking in concrete elements. External loading factors such as vibration, traffic, and wind on hardening concrete should not be ignored. The external loading provides extra stress on concrete. However, the tensile strength of early-age concrete is relatively low although it increases with age [26]. In other words, the tensile strength of concrete is very low at the initial stage, especially during the first 3 h, but becomes several times larger in the next few hours [27]. When the tensile stress due to external loading exceeds the ultimate tensile strength of concrete, cracking occurs in concrete. Higher content of coarse aggregate, unsuitable aggregate gradation, the use of very fine and highly angular sand, the incorporation of incompatible concrete constituents, inadequate curing, inappropriate element dimensions, deficient control joints, misplacement of dowels and/or tie bars, poor stability, extremely hot surrounding environment, and rapid temperature drop are the key causes of transverse cracking in concrete elements [1]. Equipment or traffic loading at the early-age, inadequate curing because of late or poor coverage, excessive curling and warping stresses caused by very long dimensions, poor stability causing excessive deflection under load, and very close dowel and/or tie bars preventing joint corner relaxation are the major reasons for corner cracking in concrete elements [1]. Skewed joints, late sawing, sawing along wind direction, and high wind are some of the reasons for pop-off cracks in concrete elements such as pavement slabs [1]. Mismatched joints in adjacent lanes, joints matching in location but of different types, and cracking from transverse joints in previously paved adjacent lanes can cause sympathy cracks in concrete pavement [1]. High workability, slow setting time, low viscosity, shallow placement of distribution reinforcement as well as dowel or tie bars, and large aggregate size are the major reasons for settlement cracks in concrete pavement [1].