Effect of Super-Absorbent Polymer on Shrinkage and Permeability of Self-Compacting Concrete (SCC)

Transcription

1 Effect of Super-Absorbent Polymer on Shrinkage and Permeability of Self-Compacting Concrete (SCC) Caijun Shi 1, Jianhui Liu 1, Kuixi Lv 1, Xianwei Ma 1, 2, Jian Zhang 1, Zemei Wu 1, 3 1 College of Civil Engineering, Hunan University, Changsha, 4182, China 2 Henan University of Urban Construction, Pingdingshan, Henan, 46736, China 3 Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla, Missouri, USA Abstract: This paper investigated the influences of super-absorbent polymer (SAP) on the workability, compressive strength, early autogenous shrinkage, dry shrinkage, water absorption, and chloride ion permeability of self-compacting concrete (SCC). Three SAPs with different particle sizes (3-75, , and microns) and four dosages (,.6%,.12%, and.18%), by mass of cement, were used. The results indicated that SAP had little effect on workability and compressive strength of SCC. The compressive strength slightly decreased with the increase of SAP particle size. The early-age autogenous shrinkage of SCC was reduced by using SAP. SAP with particle size of μm could more efficiently mitigate early-age autogenous (3 d) shrinkage and drying shrinkage of SCC. The drying shrinkage of SCC was reduced when the SAP dosage was less than.12%. Otherwise, the drying shrinkage was increased. The water absorption of SCC gradually increased with the increase of SAP dosage. SCC with SAP particle size in the range of 3-75 μm had the lowest water absorption and chloride ion diffusion coefficient as well. Incorporation of SAP increased the chloride ion permeability of SCC at 56 d. Keywords: Self-compacting concrete; Superabsorbent polymer; Compressive strength; Autogenous shrinkage; Drying shrinkage; Chloride ion permeability 1. Introduction Self-compacting concrete (SCC) is increasingly showing its advantages of environmental friendly, in terms of technical and economical characteristics [1], because of high density and stability without need of vibration. Due to its special composition, it has higher risk of cracking resulting from shrinkage than K.H. Khayat, SCC th International RILEM Symposium on Self-Compacting Concrete, ISBN: RILEM

2 74 Caijun Shi, Jianhui Liu, Kuixi Lv et al. conventional concrete [2]. Cracking may lead to reduced strength, decreased durability, loss of prestress in prestressed structural elements, and structural integrity. Thus, it's important to understand and control the shrinkage of SCC. The internal relative humidity of concrete will keep in a high level for a certain period of time by introducing additional water. It can replenish the cement consumption or evaporation of moisture, which can decrease the shrinkage of concrete. Super-absorbent polymer (SAP) is a high polymer material containing strong hydrophilic group. It is considered as an ideal curing material because of its ability to absorb a significant amount of liquid from surrounding environment and to release it, so as to provide water for cement hydration in the later hydration period. As we know, the internal humidity of cement decreases with further cement hydration after hardening. SAP has an obvious effect in reducing shrinkage due to its water absorption and release ability [3,5]. Han et al. [3] incoporated SAP into high-strength self-compacting concrete and found that SAP could significantly reduce the autogenous shrinkage and slightly decrease the drying shrinkage. SAP can affect other properties of concrete as well, such as workability, mechanical properties, and durability, etc. The mixed SAP could increase the degree of hydration of concrete with water to binder ratio (w/b) less than.42, and hence enhanced the strength development. However, the hollow voids introduced by SAP would reduce the strength of concrete. If the double effects achieve a balance, the strength of concrete could remain unchanged. If not, then one of the two effects will dominate, and hence lead to increase or decrease in strength [4]. Huang and Wang [5] found that addition of.4% SAP (with diameter of 6-15 mesh) did not reduce the compressive strength of ultra-high performance concrete (UHPC) at 28 d when the internal curing w/b was.7. Lure [6] found that.4% SAP and 5% extra water by the mass of cement had slight effect on the compressive strength of mortar when the water to cement ratio (w/c) was.3. However, the early-age (7 d) and later-age (28 and 56 d) compressive strength of cement paste were reduced by 2% and 1%, respectively. Hasholt and Jensen [7] reported that the addition of SAP can increase gel space ratio in cement paste. Although a lot of researches have been done on the effect of super-absorbent polymer on shrinkage and strength of SCC, very limited information focuses on the particle size. Moreover, the existence of the pores associated with SAP can change the durability of SCC. Therefore, it is important to investigate the overall properties of SCC incoporated with SAP. This paper aims at investigating the effects of the particle size and dosage of SAP on workability, compressive strength, shrinkage, water absorption, and durability (carbonation and chloride permeability) of SCC. Three SAPs with different particle sizes (3-75, and microns) were used. Four dosages of,.6%,.12%, and.18%, by mass of cement, were incoporated. It should provide importance significance in selecting appropriate particle size and dosage of SAP and eventually improving the overall properties of SCC.

3 Effect of Super-Absorbent Polymer on Shrinkage and Permeability of SCC Materials and Methods 2.1 Materials The cementitious materials used in this work include P.I Portland cement and fly ash. Their physical properties and chemical composition are shown in Table I. The particle size of coarse aggregate (natural gravel) was in the range of 5-2 mm with continuous gradation. Its apparent density was 261 kg/m 3. Fine aggregate (natural sand) had particle size of to 5 mm was used. Its fineness modulus and apparent density were 2.7 and 261 kg/m 3, respectively. The cumulative passing percentage of the fine and coarse aggregates are shown in Table II. Polycarboxylatebased superplasticizer (SP) with water reduction capability of 25% was used. Table I. Physical properties and chemical composition of cement and fly ash. SiO 2 Al 2O 3 Fe 2O 3 CaO MgO SO 3 Na 2O eq ignition loss Density (g/cm 3 ) Cement Fly ash Table II. Cumulative passing percentage of fine aggregate and coarse aggregate. Size (mm) River sand Gravel The saturated water absorption of SAP A was 26 g/g in deionized water and 21 g/g in tap water. The SAP A was spherical, with particle size in the range of 3-5 μm. It can be divided into three types with particle sizes of 3-75 microns (SAP A1), microns (SAP A2), and microns (SAP A3). The sizes with 1%, 5%, and 9% passing were denoted as d1, d5, and d9, as summarized in Table III. The variation of water absorption in cement paste filtrate (water to cement ratio was 1:1) determined by tea bag method is shown in Figure 1. When SAP was immersed in water, it absorbed a high amount of solutions in the first 1 minutes. The absorbed water then gradually released between 1 and 12 min, and remained constant afterward.

4 76 Caijun Shi, Jianhui Liu, Kuixi Lv et al. Water absorption (g/g) SAP A SAP A1 SAP A2 SAP A Time (min) Figure 1. Water absorption of SAP in cement paste filtrate. As shown in Table III, the water absorption of SAP A1 was slightly higher than those of the other SAPs in the 18 min. This was attributed to the larger liquid absorption area and faster volume balance after absorption. 2.2 Mixture proportion Table III. Particle size distribution of SAP. SAP A SAP A1 SAP A2 SAP A3 Size [μm] d1 [μm] d5 [μm] d9 [μm] The mixture proportion of SCCs are shown in Table IV. Table IV. Mixture proportion of SCC. Sample Cement Fly ash Water Sand Gravel IW SAP No. (kg/m 3 ) (kg/m 3 ) (kg/m 3 ) (kg/m 3 ) (kg/m 3 ) (kg/m 3 ) Wic/B We/B SN SN (A).2.3 SN (A).4.3 SN (A).6.3 SA (A1).4.3 SA (A2).4.3 SA (A3).4.3 SP* Superplasticizer; We/B Effective water to binder ratio; Wic/B Internal curing water to binder ratio; IW-Internal water

5 Effect of Super-Absorbent Polymer on Shrinkage and Permeability of SCC 77 Four dosages of,.6%,.12%, and.18% by the mass of cement were incoporated. They were desiganated as SN, SN1, SN2, and SN3, respectively. Besides, three SCCs with three different particles sizes (A1, A2, and A3) at a constant of.12% were used. They were designated as SA1, SA2, and SA3, respectively. 2.3 Experimental methods Workability The workability of SCC was mainly characterized by slump flow, T 5, L-flow test, and sieve analysis. The superplasticizer dosage was adjusted to ensure that the slump flow of the control mixture (SN) was 65±5 mm, and other mixtures maintain the same with the control one Compressive strength The compressive strength of SCC was measured in accordance with the Chinese Standard GB/T [8] by using mm cubic specimens. The specimens were demolded after one day of casting, and then cured in standard curing room until testing age of 3, 7, and 28 d Autogenous shrinkage Autogenous shrinkage of the mortar was measured according to ASTM C [9], where the concrete mixture was casted into a thin, corrugated polyethylene mold. By using this method, the volume deformation of flow state mortar could be transferred to length deformation. Each mixture had two specimens, and average values were reported. Data was collected through a multi-channel data acquisition instrument Dry shrinkage The drying shrinkage of SCC was measured following the Chinese Standard GB/T [1]. Fresh concrete was casted into mm molds. After casting, concrete specimens were cured in standard curing room (T = 2 ± 1 C and RH 98%) for 24 h. The specimens were then demolded and kept in standard curing room for 48 h. After that, specimens were moved into a chamber with a temperature of 2±2 C and relative humidity of 5±5%. The original length of specimens was measured. The length of specimens at 1, 3, 7, 14, 28, and 56 d were recorded to evaluate drying shrinkage Water absorption

6 78 Caijun Shi, Jianhui Liu, Kuixi Lv et al. The water absorption can reflect the effect of SAP on pore structure and permeability of SCC. Cube mortar specimens with size of mm according to Chinese Standard GB/T [11], was prepared. Water absorption after 28 d standard curing was determined Carbonation The carbonation resistance of SCC was measured in accordance with the Chinese Standard GB/T [1]. Three cube specimens with size of mm were prepared for each mixture, and cured in the standard curing room for 28 d. Specimens were dried for 48 h at 6 C before experiment. Four surfaces of the specimens were sealed with wax for keeping two opposite profiles in open situation. Then, these specimens were placed into a carbonation chamber with CO 2 concentration of 2±3%, temperature of 2±5 C, and humidity of 7±5%. The carbonation depths of the specimens were measured in 3, 7, 14, and 28 d. Then an alcoholic solution of 1% phénolphtaleine was immediately sprayed on the fresh surface. The phénolphtaleine solution was sprayed again after 3 min when obvious coloration cannot be observed. The measurements started at 1h±15min after spraying and completed without a pause. The carbonation front was measured at 5 points on each face. To locate these points the edge length was divided into 8 distances, and the 5 central points were used only. The carbonation depth (d k) was determined using a ruler or a sliding gauge which perpendicular to the surface of the cube with a precision of.5 mm. The depth of the front was measured on all four faces of cubes giving a total 2 measurements. The mean depth was calculated and recorded for each face and average values were reported Chloride permeability In order to evaluate the chloride permeability of concrete and indirectly reflect the pore structure of SCC, the rapid chloride migration coefficient was measured in accordance with the Standard NT Build 492 [12]. 3. Results and Discussion 3.1 Workability Workability of SCC mixture is shown in Table V. The slump flow of SCC was slightly reduced compared with the control group SN, while the T 5 was slightly increased. According to the results of the L-box test, the SAP had little effect on the passing capability, and the ratios of H 2/H 1 were between.815 and.85. Besides, the SCC mixture had a tendency of increasing segregation by adding the SAP based on the results of segregation test.

7 Effect of Super-Absorbent Polymer on Shrinkage and Permeability of SCC 79 Table V. Workability of SCC mixtures. Slump flow The ratio of Sample No. L-flow H 2/H 1 segregation D (mm) T 5 (s) SN SN SN SN SA SA SA Compressive strength The influences of the dosage of the SAP on the compressive strength of SCC at 3, 7, and 28 d are shown in Figure 2. Compressive strength (MPa) SN SN1 SN2 SN Curing age (d) Figure 2. Effects of SAP dosages on compressive strength of SCC. The compressive strength of the control group SN were 25.9, 34.4, and 38.8 MPa, respectively, at 3, 7, and 28 d. With the SAP A dosage increased, the early-age compressive strength (3 d) of SCC increased. However, SAP A had no obvious reduction on later-age compressive strength. Compared with the control group, the compressive strength of SN1 at 3 d was almost similar, but was obvious reduced at 7 and 28 d. For SN2 mixture, the compressive strength was slightly higher than that of SN, while was similar for SN3 at three different ages. It was reported that the SAP could release water into cement matrix for a long time after absorbing water. The increased degree of hydration of cement lead to improvment in compressive strength. However, the introduced pores of SAP can reduce the strength of concrete [4]. If the enhancement effect of hydration degree of cement matrix could

8 8 Caijun Shi, Jianhui Liu, Kuixi Lv et al. compensate the weakening effect from SAP pores, the compressive strength could keep close with the control group. This agrees well with the results reported by Bentz etc. [13]. The influences of the particle size of the SAP on the compressive strength of SCC at 3, 7, and 28 d are shown in Figure 3. The compressive strength of SCC decreased with the increase of SAP particle size. Compared with control group SN, the 3 and 28 d compressive strengths of SA1 were increased by 6.9% and 1.%, respectively, while the 7 d compressive strength was reduced by 1.5%. For group SA2, the 3 d compressive strength was increased by 2.3%, while the 7 and 28 d compressive strength decreased by 1.2% and 7.7%, respectively. However, the 3, 7 and 28 d compressive strengthes of SA3 group were reduced by 3.1%, 4.4%, and 3.1%, respectively. When same curing water was introduced, the SAP particle size could affect SAP water absorption/desorption rate, distribution in the matrix, and pore size. Therefore, the SAP particles size had the most significant influence on the compressive strength of concrete at later-age [14]. Compressive strength (MPa) SN SA1 SA2 SA Curing age (d) Figure 3. Effects of SAP particle sizes on compressive strength of SCC. 3.3 Autogenous shrinkage The autogenous shrinkage of SCC mortar with different dosages of SAP is shown in Figure 4. It is suggested that the autogenous shrinkage developed very fast in the early stage, and remained almost stable after 24 h. The 3 d autogenous shrinkage of the control group SN was 1668 με. The 3 d autogenous shrinkages of SN1, SN2, and SN3 mixture reduced by 25.1%, 27.8%, and 62.5%, respectively. It can be also seen that the SN1 and SN2 mixture had the similar autogenous shrinkage (3 d), while the SN3 had the lowest autogenous shrinkage. The internal curing water to binder ratio of SN1, SN2, and SN3 were.2,.4, and.6, respectively. This suggested that the early autogenous shrinkage of SCC mortar was reduced with the increase of internal curing water. Autogenous shrinkage is the apparent volume or length change of cement-based material under the seal and isothermal condition [15]. The chemical shrinkage could be completely transformed into apparent volume change during the

9 Effect of Super-Absorbent Polymer on Shrinkage and Permeability of SCC 81 plastic stage. Hardened cement paste could be partially bear volume change caused by chemical shrinkage. Meanwhile, as the internal relative humidity decreased, capillary meniscus could form leading to capillary contraction stress [6]. Therefore, when internal relative humidity (IRH) was reduced, water can gradually transfer from the SAP pores to cement paste. The higher SAP dosage has greater amount available water to migrate, so that the internal relative humidity (IRH) of concrete decreased more slow. Thus, the capillary stress and autogenous shrinkage become smaller. Wang et al. [16] showed that introducting SAP and internal curing water could significantly delay the IRH reduction, and improved early autogenous shrinkage of concrete. Autogenous shrinkage (μm/m) SN (W IC /B=.) SN1 (W IC /B=.2) SN2 (W IC /B=.4) SN3 (W IC /B=.6) Age (h) Figure 4. Effects of SAP dosages on autogenous shrinkage of SCC mortar. The autogenous shrinkage of SCC with different SAP particle sizes within 72 h is shown in Figure 5. With the increase of particle size, the internal curing water to binder ratio of group SA1, SA2, and SA3 was maintained at.4. Compared to SN, the autogenous shrinkages of SA1, SA2, and SA3 at 3 d were reduced by 25.7%, 33.5%, and 1.3%, respectively. This suggested that SAP with particle size of μm was more efficient in reducing autogenous shrinkage. The internal moisture of SAP is controlled by van der Waals force. At the beginning, the water can spread into surrounding environment with greater diffusion rate. However, due to the bondage of more side chains, moisture diffusion rate is gradually decreased [17]. Moisture diffusion from the large size of SAP particles was faster than that of the small particle size. The SAP particle size can lead to two opposite effects. Space distance of smaller particles could improve the effectiveness of internal curing (IC), while the higher controlling power of water molecules could reduce the effectiveness of internal curing (IC) [18]. For larger particle size of SAP, the particle spacing is larger. This is not conducive to the internal curing water migration to every part of the cement. For smaller particle size of SAP, the effectiveness that the internal curing water migrates into surrounding cement would be reduced.

10 82 Caijun Shi, Jianhui Liu, Kuixi Lv et al. Autogenous shrinkage (μm/m) SN (W IC /B=.) SA3 (W IC /B=.4) SA1 (W IC /B=.4) SA2 (W IC /B=.4) Age (h) Figure 5. Effects of SAP particle sizes on autogenous shrinkage of SCC mortar. 3.4 Dry shrinkage Figure 6 shows the change in drying shrinkage for samples with different dosages of SAP A up to 56 d. For SN1 and SN2 groups, adding SAP improved the drying shrinkage of SCC. The drying shrinkage of control group SN was 573 μm at 56 d. It reduced by 9.1% and 2.3%, respectively, for group SN1 and SN2 when compared to the SN. Group SN3 had a lower drying shrinkage in the early and later age, and, byt higher than that of SN group after 21 d. When external relative humidity was lower than the internal moisture, the internal curing water was released into the cement matrix and reduced the drying shrinkage of SCC. SN3 with higher dosages of SAP increased the drying shrinkage. This was because the excessive SAP could introduce more pores in SCC, and the SAP releasing water into the matrix could not support further increasing in water loss due to drying. Han [3] found that the SAP could slightly reduced the drying shrinkage of high-strength self-compacting concrete. Soliman [19] showed that SAP significantly increased drying shrinkage of UHPC. When SAP and internal curing water were used at the same time, the internal curing water increased the porosity of concrete and the risk of the water loss rate. At the same time, the SAP internal moisture can slow the falling rate of concrete internal humidity.

11 Effect of Super-Absorbent Polymer on Shrinkage and Permeability of SCC 83 Drying shrinkage (μm/m) SN SN1 SN2 SN Age (d) Figure 6. Effects of SAP dosages on drying shrinkage of SCC. The change in drying shrinkage of SCC with different particle size of SAP within 56 d is shown in Figure 7. Compared with the control group, the 56 d drying shrinkages of groups SA1, SA2, and SA3 were decreased by 1.3%, 27.9%, and 21.%, respectively. This showed similar trend as the autogenous shrinkage indicated. The drying shrinkage of SCC depended on SAP particles spatial proximity and the effectiveness of internal moisture migration into surrounding environment. Drying shrinkage (μm/m) SN SA1 SA2 SA Age (d) Figure 7. Effects of SAP particle sizes on drying shrinkage of SCC. 3.5 Water absorption The effects of SAP dosage and particle size on the water absorption of SCC is shown in Figure 8. The water absorption of control group (SN) was 4.47%. Compared to the control group, the water absorption of groups SN1, SN2, and SN3 increased by 1.6%, 12.5%, and 1.6%, respectively. Therefore, the water absorption of SCC increased with the increse of SAP dosage. When concrete specimens were submerged in water, they would absorb moisture driven by capillary suction to fill the pores in concrete [2]. The concrete adsorption was closely related to the pore

12 84 Caijun Shi, Jianhui Liu, Kuixi Lv et al. structure, so the water absorption of concrete could determine the effective porosity. Therefore, the effective porosity of SCC decreased with the increase of SAP dosage and the internal water-binder ratio. SAP can change the pore size distribution and pore connectivity in concrete, and the total porosity of concrete depends on the total water to binder ratio [21]. Water absorption SN SN1 SN2 SN3 SA1 SA2 SA3 Sample No. Figure 8. Effects of SAP dosages and particle sizes on water absorption of SCC. Compared to the control group, the water absorption of groups SA1 reduced by 2.%, while SA2 and SA3 increased by 16.3% and 1.7%, respectively. Therefore, the effective porosity of the group SA2 was largest, while that of the group SA1 was lowest. 3.6 Carbonation The carbonation depth of SCC mixed with different amount of SAP A is shown in Figure 9. The carbonation depth of the control group SN was 12.7 mm in 28 d. Compared to the control group, the 28 d carbonation depth of SN1, SN2 and SN3 increased by 2.5%, 11.%, and 8.7% respectively. Thus, the carbonation depth of SCC decreased with the increase of internal curing water to binder ratio. The water absorption results showed that the porosity of SCC increased gradually with the increase of internal curing water to binder ratio. At the same time, in the presence of SAP, the internal curing water was released into the surrounding cement grains, which promoted further hydration of cement, and increased the Ca(OH) 2 content. The carbonation resistance of SCC was affected by relative humidity, permeability, and alkalinity of concrete. Beushausen et al. [22] found that the carbonation depth of cement mortar gradually reduced with the increase of SAP dosage without extra internal curing water. Assmann [23] found that the carbonation depth of concrete incoporated with SAP was slightly higher than that of the control group. Therefore, the balance between SAP dosage and additional water to binder ratio had significant effect on the carbonation depth of concrete.

13 Effect of Super-Absorbent Polymer on Shrinkage and Permeability of SCC 85 Carbonation depth (mm) SN SN1 SN2 SN Carbonation age (d) Figure 9. Effects of SAP dosages on carbonation depth of SCC. The change in carbonation depth of SCC mixed with different particle sizes of SAP A is shown in Figure 1. The 28 d carbonation depths of SA1, SA2, and SA3 were 11.8, 13.2, and 12.7 mm, respectively. Compared to control group SN, the carbonation depth of SA1 was decreased by 7.1%, while increased by 3.9% for SA2. However, there was little change for SA3. This suggested that the carbonation resistance of SCC mixed with the smallest particles size of SAP was the best. The water absorption results showd that the group mixed with SAP A1 had the lowest porosity, which reduced the penetration rate of CO 2 in concrete. Carbonation depth (mm) SN SA1 6 SA2 SA Carbonation age (d) Figure 1. Effects of SAP particle sizes on carbonation depth of SCC. 3.7 Chloride permeability The influences of SAPs on the chloride ion permeability of SCC is shown in Figure 11. It was indicated that internal curing water increased the SCC chloride ion permeability. Hasholt et al. [7] reported that the addition of SAP can increase gel space ratio in cement paste. As the gel space increased, the capillary porosity volume and connectivity of cement paste reduced. With the same internal curing water to

14 86 Caijun Shi, Jianhui Liu, Kuixi Lv et al. binder ratio and dosage of SAP, chloride ion migration coefficients was lowest for SA1. This was because that the smaller size of SAP A1 reduced the connectivity of the pores in SCC. Chloride ion migration cofficient( 1-12 m 2 /s) SN SN1 SN2 SN3 SA1 SA2 SA3 Sample No. Figure 11. Effects of SAP on chloride migration coefficient SAP. 4. Conclusions Based on the results from the above tests, the following conclusions can be drawn: (1) The slump flow of SCC was slightly reduced with the addition of SAP, while T 5 was slightly increased. According to the L-flow test results, SAP has little effect on the passing ability. (2) With the increase of internal curing water to binder ratio, the compressive strength of SCC remainded unchanged. But it decreased slightly with the increase of SAP particle size. (3) The early autogenous shrinkage of SCC mortar was reduced with the increase of internal curing water. The drying shrinkage increased as the SAP dosage increased. SAP with particle size of μm could significantly reduce the autogenous and drying shrinkage of SCC. (4) The water absorption and carbonation depth of SCC increased with the increase of SAP dosage. Among the three particle sizes of SAP, SCC with the smallest particle size had the the lowest water absorption and the best carbonation resistance. (5) With the same internal curing water to binder ratio and SAP dosage, introducing the internal curing water increased the chloride permeability of SCC, and the chloride migration coefficient of SCC with particle size of 3-75 μm was lowest.

15 Effect of Super-Absorbent Polymer on Shrinkage and Permeability of SCC 87 References [1] Shah, S. P. and Lomboy, G. R. (215). Future research needs in selfconsolidating concrete. Journal of Sustainable Cement-Based Materials, vol. 4, n. 3-4, p [2] Craeye, B., De Schutter, G., Desmet, B., Vantomme, J., Heirman, G., Vandewalle, L., Cizer, Ö., and Kadri, E. H. (21). Effect of mineral filler type on autogenous shrinkage of self-compacting concrete. Cem. Concr. Res., vol. 4, n. 6, p [3] Han, J., Fang, H., and Wang, K. (214). Design and control shrinkage behavior of high-strength self-consolidating concrete using shrinkage-reducing admixture and super-absorbent polymer. Journal of Sustainable Cement-Based Materials, vol. 3, n. 3-4, p [4] Hasholt, M. T., Jensen, O. M., Kovler, K., and Zhutovsky, S. (212). Can superabsorent polymers mitigate autogenous shrinkage of internally cured concrete without compromising the strength?, Constr. Build. Mater., vol. 31, p [5] Huang Zheng yu, and Wang Jia. (212). Effects of SAP on the performance of UHPC, Bulletin of the Chinese Ceramic Society, vol. 31, n. 3, p [6] Lura, P. (23). Autogenous deformation and internal curing of concrete. TU Delft, Delft University of Technology. [7] Hasholt, M. T., and Jensen, O. M. (215). Chloride migration in concrete with superabsorbent polymers. Cem. Concr. Compos.,vol. 55, p [8] Chinese Standard GB/T , (22). Standard for test method of mechanical properties on ordinary concrete, China Architecture & Building Press. [9] ASTM, C Standard Test Method for Autogenous Strain of Cement Paste and Mortar. [1] Chinese Standard GB/T , (29). Standard for test methods of longterm performance and durability of ordinary concrete, China Architecture & Building Press. [11] Chinese Standard GB/T , (28). Test methods of autoclaved aerated concrete, Standards Press of China. [12] NT Build 492, (1999). Concrete, mortar and cement-based repair materials: chloride migration coefficient from non-steady-state migration experiments, NordTest, Espoo. [13] Bentz, D. P., Geiker, M., and Jensen, O. M. (22, June). On the mitigation of early age cracking. In: International Seminar on Self-Desiccation and Its Importance in Concrete Technology, Vol. 15, p , Persson, B. and Fagerlund, G. (Eds.), Lund, Sweden. [14] Zhutovsky, S., Kovler, K., and Bentur, A. (211). Revisiting the protected paste volume concept for internal curing of high-strength concretes. Cem. Concr. Res., vol. 41, n. 9, p

16 88 Caijun Shi, Jianhui Liu, Kuixi Lv et al. [15] Kovler, K., and Jensen, O. (27). Internal curing of concrete: State-of-the-Art Report. of RILEM Technical Committee. 196-ICC. [16] Wang, F., Zhou, Y., Peng, B., Liu, Z., and Hu, S. (29). Autogenous shrinkage of concrete with super-absorbent polymer. ACI Mater. J., vol.16, n. 2, p [17] Mönnig, S., (29). Superabsorbing additions in concrete: applications, modelling andcomparison of different internal water sources, Dissertation, Stuttgart University. [18] Zhutovsky, S., Kovler, K., & Bentur, A. (211). Revisiting the protected paste volume concept for internal curing of high-strength concretes. Cem. Concr. Res., vol. 41, n. 9, p [19] Soliman, A. M., and Nehdi, M. L. (211). Effect of drying conditions on autogenous shrinkage in ultra-high performance concrete at early-age. Mater. Struct., vol. 44, n. 5, p [2] Rose, D. A., (1965). Water movement in unsaturated porous materials, RILEM Bulletin, vol. 29, p [21] KONG, X., and ZHANG, Z. (213). Effect of Super-absorbent Polymer on Pore Structure of Hardened Cement Paste in High-strength Concrete. Journal of The Chinese Ceramic Society, vol. 41, n. 11, p [22] Beushausen, H., Gillmer, M., and Alexander, M. (214). The influence of superabsorbent polymers on strength and durability properties of blended cement mortars. Cem. Concr. Compos., vol. 52, p [23] Assmann A. (213). Physical properties of concrete modified with superabsorbent polymers. Stuttgart University, Germany,.