# Early-Age Cracking in Concrete: Causes, Consequences, Remedial Measures, and Recommendations
## 3 Causes of Early-Age Cracking
The increased stress due to odd shape and cracking from interior corners can cause re-entrant cracks in concrete elements [1]. They typically originate from beam pockets, window corners, or other openings. [PERSON] [14] attempted to identify the causes of the early-age cracking in concrete bridge deck through literature review and questionnaire survey throughout the United States. It was deduced that the high evaporation rate and subsequent high magnitude of shrinkage are the most common causes of cracking in concrete bridge deck. The other causes of early-age cracking identified were the use of high-slump concrete, excessive heat of hydration, inefficient curing procedures, improper sequence of concrete pouring, inadequate concrete cover, insufficient compaction, inadequate detailing of joints between new and old decks, etc. [14]. [PERSON] and [PERSON] [28] also identified the deck restraint, improper curing, high early-age modulus of elasticity, creep, shrinkage, and thermal strains as the causes of cracking in concrete bridge decks. Concrete creep is one of the major causes of the early-age cracking in concrete elements. It is defined as the result of numerous interatomic bond breaks happening at different time periods at different overstressed sites of concrete [29]. [PERSON] et al. [30] divided the creep into three types: basic creep, drying creep, and transitional thermal creep. Basic creep is strongly dependent on the age at loading and water content [29]. [PERSON] et al. [30] divided the age at loading into short-term chemical aging and long-term nonchemical aging. The effect of hydration process on the capillary pore structure in the cement paste reduces the creep compliance of concrete [29]. This is referred to as short-term chemical aging. In long-term nonchemical aging, the cement hydration in concrete is practically stopped and the basic creep decreases while the age at loading increases [29]. Drying creep, also referred to as Pickett effect [31; 32], occurs when concrete elements undergo deformation during drying as well is after drying. There are two major mechanisms for this form of creep--firstly, a macroscopic mechanism due to microcracking or strain-softening damage and secondly, a nanoscale mechanism due to stress-induced shrinkage [32]. According to the macroscopic mechanism, the nonuniform moisture distribution between the external and internal layers of concrete causes shrinkage to occur in these layers at different time periods due to the loss of water from capillary pores. Consequently, a tensile stress is induced that leads to local microcracking or tensile strain-softening damage in the surface layer, resulting in nonlinear inelastic deformation (unrecoverable creep) of concrete. The second mechanism is stress-induced shrinkage due to moisture loss and temperature rise [32]. Upon drying, a thermodynamic imbalance among the chemical potentials of various phases of pore water develops due to reduced pore vapor pressure and temperature rise [30], resulting in tensile stresses, which are balanced by compressive stresses (micro-prestress) in the surrounding concrete and consequently concrete shrinks. This phenomenon particularly occurs in the nanostructure of concrete comprising calcium silicate hydrates, very small capillary pores, and gel pores. The breakages of bonds in the calcium silicate hydrates may happen by an increase in the magnitude of micro-prestress. Transitional thermal creep is defined as the transient increase of creep due to changing temperature [30]. The first mechanism is an apparent macroscopic mechanism, which is, like drying creep, owing to thermally induced microcracking. Another mechanism is the nanoscale mechanism, in which the changing temperature alters the level of micro-prestress by changing the chemical potential of nanopore water [30].