Experimental investigation on the compressive strength and shrinkage of concrete with pre-wetted lightweight aggregates X.F. Wang, C. Fang, W.Q. Kuang, D.W. Li, N.X. Han, F. Xing ⇑ Guangdong Key Laboratory of Durability in Coastal Civil Engineering, College of Civil Engineering, Shenzhen University, Shenzhen, Guangdong 518060, China highlights  Three types of PLWA with five volume fractions were studied.  Internal curing shows great influence in the evolvement of the compressive strength and the shrinkage.  PLWA combined with expansive agent is effective in reducing shrinkage.  A unified model is presented for the prediction of the compressive strength and shrinkage of concrete with PLWA. article info Article history: Received 22 April 2017 Received in revised form 17 July 2017 Accepted 29 July 2017 Keywords: Lightweight aggregate concrete (LWAC) Hydration degree Compressive strength Shrinkage Predictive model abstract Experimental studies are presented on the influence of three types of pre-wetted lightweight aggregates (PLWA), through their volume fractions and moisture content, on the compressive strength and shrinkage of concrete and expansive concrete. Via integrated thermal analysis, the hydration degree during 7 d– 28 d was found to be increased by the internal curing. The use of PLWA increased the shrinkage at 240 d due to the significant increase in the shrinkage deformation during the age of 28 d–90 d caused by internal curing. The results also suggest that incorporation of 10-Mas. % expansive agent is useful to diminish the shrinkage, especially by its combined use with PLWA. Predictive models for the compres- sive strength and shrinkage of concrete containing PLWA were discussed and a unified model predicting the compressive strength and shrinkage of concrete containing PLWA was suggested. Ó 2017 Published by Elsevier Ltd. 1. Introduction Shrinkage, as well as the compressive strength, was considered as the essential parameters for the design of concrete structures [1]. Deleterious volume change in constrained condition easily causes tensile stress and leads to the initiation and propagation of micro cracks [2], which may impair the durability and compro- mise the performance of concrete structures. Hence, developing new technologies that help to alleviate these negative impacts is necessary. Pre-wetted lightweight aggregate (known as internal curing (IC)) [3–6] has been reported as an effective strategy in reducing autogenous shrinkage and preventing cracking at early age. It is known that, autogenous shrinkage and drying shrinkage are usu- ally due to the drop of moisture inside material caused by the envi- ronmental drying and the cement hydration [7]. Water stored in the pores of PLWA is available to aid in curing [4,8,9], thereby negating the effects of self-desiccation and the moisture loss. Research on the internal curing has indicated that cracking poten- tial could be effectively reduced by the dispersion of the internal water reservoirs [10,11]. Expansive agent [12,13] was also usually used in concrete to compensate the shrinkage. The negative volume change of con- crete can be reduced to some extent via the counteraction between the swelling of expansive agent and the shrinkage of concrete. The components of expansive agent react with water to form ettringite which is the main source of expansion [14]. As reported in Ref. [15], several thousands of micro strains of expansion can be pro- duced by expansive cements. And synergistic effect between IC and expansive agent has been justified in shrinkage control [1]. Many researchers have suggested the beneficial effects of PLWA and expansive agent at counteracting the effect of shrinkage and cracking at early age [3], whereas few studies have investigated the effect of PLWA’s moisture content and volume fraction [4] on the time-dependent compressive strength and shrinkage of con- http://dx.doi.org/10.1016/j.conbuildmat.2017.07.224 0950-0618/Ó 2017 Published by Elsevier Ltd. ⇑ Corresponding author at: Guangdong Key Laboratory of Durability in Coastal Civil Engineering, Shenzhen University, 3688 Nanhai Ave, Shenzhen, Guangdong 518060, China. E-mail address: xingf@szu.edu.cn (F. Xing). Construction and Building Materials 155 (2017) 867–879 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat