Influence of prewetted lightweight aggregates on the behavior and cracking potential of internally cured concrete at an early age
Introduction
With the increasing promoted use of high-performance concrete (HPC), decreasing water-to-cement (w/c) ratio is being applied in practice [1], [2], [3]. Although HPC can offer high strength and low permeability, this lower w/c ratio comes with other drawbacks, including high self-desiccation [4], [5] and high temperature rise in the concrete [6]. Self-desiccation, which induces marked autogenous shrinkage, leads to higher cracking potential [7]. Given that less water and more cement are used in HPC to attain high strength, the available water in the hydration progress decreases, and the inner concrete environment yields a lower chemical potential of water [8]. Although external water curing is utilized in HPC, its cracking potential is increased because of the low penetration of concrete with low w/c ratio [9]. Therefore, internal curing (IC) technology is employed to reduce the cracking potential [10]. IC, which is defined by the American Concrete Institute as “a process by which the hydration of cement continues because of the availability of internal water that is not part of the mixing water” was proposed by Robert Philleo as a means of avoiding self-desiccation using saturated lightweight fine aggregate in high-strength concrete in 1991 [11]. IC provides curing water equally throughout the cross section in the concrete structure, whereas external curing water can only penetrate several millimeters into concrete with low w/c ratio [9]. IC water can also increase the degree of reaction of the cement and other supplemental cementitious materials [9]. IC keeps the pores within the hydrating cement paste fluid filled and thus helps reduce or even eliminate capillary stress, thereby minimizing the likelihood of cracking [12]. An experimental study on the stress development, temperature drop necessary to crack, and cracking age of mortars containing prewetted lightweight aggregates (LWAs) with the dual ring test has shown a lower rate of stress development, higher temperature drop, and longer age to crack [9]. Internally cured concrete with a larger amount of LWAs shows a greater reduction in the rate and volume of autogenous shrinkage [2], and the use of LWAs with reduced stiffness can improve the shrinkage cracking resistance of concrete [13]. As a result, the cracking potential is reduced in internally cured concrete with prewetted LWAs.
Temperature stress testing machine (TSTM) is employed to study the early-age cracking behavior of concrete with prewetted LWAs [5], [14]. This device enables measurements directly after casting. This characteristic is important because autogenous shrinkage has to be measured accurately at very early age (<24 h). The characteristics of early-age concrete, including temperature change, strain, restrained stress, and creep, can be determined in one TSTM test [15]. Therefore, studying the cracking resistance of internally cured concrete with prewetted LWAs by using TSTM is necessary to thoroughly understand the mechanism.
The cracking resistance of early-age concrete is affected by the temperature history [6]. The isothermal condition is used to study the cracking resistance of early-age concrete by single or dual ring test [10], and semi-adiabatic or isothermal conditions are adopted with TSTMs [1], [5], [16], [17]. The performance of mortar with different amount of fly ash cured at semi-adiabatic condition was also investigated using the dual ring [6], [9]. The interior concrete of mass concrete is close to adiabatic temperature rise [6], [18]. The cracking resistance of early-age concrete under adiabatic conditions has been investigated with TSTM [19]. Cracking temperature drop is increased in internally cured concrete [12]. However, results on cracking resistance of internally cured concrete at early age under adiabatic conditions using TSTM remain lacking. Thus, the effect of prewetted LWAs on temperature change and the cracking resistance of concrete under adiabatic conditions should be studied.
Early-age creep is important in evaluating the cracking resistance of concrete. The restrained stress and cracking potential in early-age mortar cured at isothermal condition with different amount of prewetted LWAs or concrete are influenced by creep [10], [14], [20]. The early-age creep of concrete is difficult to measure because physical and chemical properties simultaneously change at early ages [21]. Creep strain of early-age concrete can be obtained by simultaneous testing on restrained and free shrinkage specimens with TSTM [15]. TSTM has been utilized to indirectly determine the tensile creep of high-strength concrete under uniaxial non-constant tensile loading at early ages [1]. A few studies have concentrated on the early-age creep of concrete mixed with prewetted LWAs, but the effect of prewetted LWAs on creep has not been systematically investigated [22]. The creep of internally cured concrete with prewetted LWAs under non-constant stress has been studied with modified TSTM [5], and the amount of total water (mix water and IC water) is kept the same [14] while the total w/c was normally increased by internal curing water provided by LWAs to promote hydration. An experimental study on the compressive creep of internally cured concrete under constant loading has been conducted [22]. The tensile creep of internally cured concrete under changing restraint degree has been conducted with the dual ring test [14]. The restraint degree of ring was changing constantly [10] and cannot be controlled. Test result shows that the creeps of early-age concrete under constant and varying restraint degree are different, and the development of stress and microcracking of concrete was also affected by the creep [20]. Thus, the cracking resistance of concrete is influenced by restrained degree. Investigation on the early-age tensile creep of internally cured concrete with LWAs under constant restraint degree is still lacking. Although the amount of prewetted LWAs has been shown to affect the efficiency of IC on concrete [23], the effect of the amount of prewetted LWAs on tensile creep has not been studied. Thus, the influence of the amount of prewetted LWAs on creep of internally cured concrete with different amounts of total water under constant restraint degree needs to be further investigated using TSTM.
However, the majority of available studies concerning the cracking resistance of internally cured concrete with prewetted LWAs did not simultaneously consider temperature history, autogenous shrinkage, restraint, and creep under adiabatic conditions [6], [10]. Although internally cured concrete with prewetted LWAs has been adopted in several projects [24], [25], such as the Indiana deck, it has not been used in mass concrete in which the temperature variation is close to adiabatic condition. Thus, whether and how prewetted LWAs influence the cracking resistance of concrete need to be investigated. The effect of prewetted LWAs on temperature history, restrained stress development, autogenous shrinkage, creep behavior, and cracking potential needs to be studied further to better understand the cracking resistance of concrete with prewetted lightweight clay aggregates.
Section snippets
Mixture proportions
Four concrete mixtures with low w/c ratio were used in this study. The mixture proportions, designated as LWA-0, LWA-10, LWA-30, and LWA-50. Mixture LWA-0 is the reference concrete with no IC, and Mixtures LWA-10, LWA-30, and LWA-50 use IC with prewetted LWA [14], [26]. For the internally cured concrete in which part of the normal-weight coarse aggregate is replaced with LWAs, the replacement ratios of coarse aggregates are 10%, 30%, and 50% of the total volume of coarse aggregates for Mixtures
Effect of prewetted LWAs on concrete temperature
The reaction of cement with water is exothermic and results in a temperature rise of tens of degrees (K) in massive concrete members [40]. When the structure cools down, the concrete contracts and may crack if restrained [41]. Eq. (2) was used to calculate the temperature rise of concrete.where is the temperature rise of concrete in °C, is the highest temperature of concrete before cracking in °C, and is the initial temperature of concrete in °C.
Fig. 4 shows that the
Conclusions
This paper presents the experimental findings on the effect of prewetted LWAs on the behavior and cracking potential of internally cured concrete under adiabatic conditions. Analysis was based on temperature difference, strain difference, restrained stress induced under a restrained condition, tensile and compressive creeps, and induced stress relaxation with four groups of different prewetted LWA mixture proportions of internally cured concrete. This research quantified the amount of prewetted
Acknowledgements
The open foundation of State Key Laboratory for Disaster Reduction in Civil Engineering of Tongji University (Grant No. SLDRCE 13-MB-05) is gratefully acknowledged. Support of the Fundamental Research Funds for Central Universities (Grant No. 2014B07114) is also gratefully acknowledged. The financial support of the National Natural Science Foundation of China (Grant Nos. 51578215, 51279051 and 51008113), Special Fund for Water Conservation Research in the Public Interest (Grant No. 201101014),
References (72)
- et al.
Volume change and cracking in internally cured mixtures made with saturated lightweight aggregate under sealed and unsealed conditions
Cem. Concr. Compos.
(2009) The influence of temperature on autogenous volume changes in cementitious materials containing shrinkage reducing admixtures
Cem. Concr. Compos.
(2012)- et al.
Protected paste volume in concrete: extension to internal curing using saturated lightweight fine aggregate
Cem. Concr. Res.
(1999) - et al.
An experimental approach for the analysis of early-age behavior of high-performance concrete structures under restrained shrinkage
Cem. Concr. Res.
(2007) - et al.
Evaluation of water transfer from saturated lightweight aggregate to cement paste matrix by neutron radiography
Nucl. Instrum. Methods Phys. Res.
(2009) - et al.
Application of internal curing for mixtures containing high volumes of fly ash
Cem. Concr. Compos.
(2012) - et al.
Internal curing of high-performance concrete with pre-soaked fine lightweight aggregate for prevention of autogenous shrinkage cracking
Cem. Concr. Res.
(2008) - et al.
Effect of curing temperature and type of cement on early-age shrinkage of high-performance concrete
Cem. Concr. Res.
(2001) - et al.
Effect of autogenous deformation on the cracking risk of slag cement concretes
Cem. Concr. Compos.
(2011) - et al.
The influence of the initial moisture content of lightweight aggregate on internal curing
Constr. Build. Mater.
(2012)
On the origin of eigenstresses in lightweight aggregate concrete
Cem. Concr. Compos.
Separation of thermal and autogenous deformation at varying temperatures using optical fiber sensors
Cem. Concr. Compos.
Controlling the coefficient of thermal expansion of cementitious materials – a new application for superabsorbent polymers
Cem. Concr. Compos.
Estimation of temperature effects on autogenous shrinkage of concrete by a new prediction model
Constr. Build. Mater.
Influence of temperature on autogenous deformation and relative humidity change in hardening cement paste
Cem. Concr. Res.
Benefits of internal curing on service life and life-cycle cost of high-performance concrete bridge decks – a case study
Cem. Concr. Compos.
Water-entrained cement-based materials: I. Principles and theoretical background
Cem. Concr. Res.
Tensile creep behavior of high strength concretes at early ages
Mater. Struct.
Self-desiccation and its importance in concrete technology
Mater. Struct.
Parametric assessment of stress development and cracking in internally cured restrained mortars experiencing autogenous deformations and thermal loading
Adv. Civil Eng.
Concrete science and reality
Internal curing-constructing more robust concrete
Struct. Mag.
Role of lightweight synthetic particles on the restrained shrinkage cracking behavior of mortar
J. Mater. Civil Eng.
Testing system for determining the mechanical behavior of early age concrete under restrained and free uniaxial shrinkage
Mater. Struct.
Effects of construction time and coarse aggregate on bridge deck cracking
ACI Mater. J.
Crack resistance evaluation for dam concrete based on temperature stress testing machine
J. South East Univ. (Natl. Sci. Ed.)
Tensile creep behavior of concrete subject to constant restraint at very early ages
J. Mater. Civil Eng.
Tensile basic creep: measurements and behavior at early age
ACI Mater. J.
Effect of internally stored water on creep of high performance concrete
ACI Mater. J.
Internal curing of concrete paving: laboratory and field experience
Quantifying stress development and remaining stress capacity in restrained, internally cured mortars
ACI Mater. J.
Internal curing efficiency of prewetted LWFAs on concrete humidity and autogenous shrinkage development
J. Mater. Civil Eng.
Concrete: Structure, Properties, and Materials
Cited by (80)
Influence of seawater and sea sand on early-age performance and cracking sensitivity of concrete
2023, Journal of Building EngineeringPredicting the crack width of the engineered cementitious materials via standard machine learning algorithms
2023, Journal of Materials Research and TechnologyCracking failure behavior of high strength concrete containing nano-CaCO<inf>3</inf> at early age
2023, Cement and Concrete CompositesEffect of recycled ceramic aggregate on hydration heat and permeability of high performance concrete
2023, Cement and Concrete CompositesEffect of internal curing on early-age properties of concrete under simulative natural environment in arid regions
2023, Construction and Building Materials