Effect of natural pozzolan content on the properties of engineered cementitious composites as repair material

Abstract

In order to determine the effect of Natural Pozzolan (NP) content on the mechanical properties and durability characteristics on Engineered Cementitious Composites (ECC) as repair material. This study focused on the evaluation of the most factors influencing compatibility between the repair material and the base concrete including mechanicals properties such as, compressive and flexural strengths, elastic modulus, capillary absorption and drying shrinkage. The experimental results showed that natural pozzolan reduces the compressive strength and the flexural strength of ECC at all ages. The elastic modulus of ECC was remarkably lower than that of normal-strength concrete. This lower Young’s modulus is desirable for repair concrete, because it prevents the stresses induced by restrained shrinkage. In addition, the incorporation of high-volume natural pozzolan decreases significantly the coefficient of capillary absorption at long term and increases the drying shrinkage. Generally, based on the results obtained in the present experimental investigation, ECC can be used effectively as an overlay material over existing parent concrete.

Keywords

natural pozzolan / engineered cementitious composites / mechanical strengths / elastic modulus / capillary absorption / drying shrinkage

Introduction

Concrete today is the most widely used construction material in the world. However, durability of reinforced concrete structures is a major problem all around the world. Corrosion and environmental condition seem to be the most serious damages as they accelerate the deterioration of concrete structures leading to considerable financial costs for municipalities. Therefore, the destroyed section in the concrete structures which lowers its performance often requires rapid and durable repair. But, More than 50% of these concrete structures show earlier signs of distress and deterioration within a time period of five years [¹].

It is well-known that there are various techniques and repair materials to overcome the damage in the deteriorated structures, in order to improve their functional performance and durability [²,³]. These repair materials can generally be classified into three types: (i) cementitious materials, (ii) polymer modified cementitious materials and (iii) polymer concrete [⁴,⁵]. But a premature failure is generally due to the quasi-brittle of concrete [⁶], to the incompatibility of the combined system, and to inappropriate selection of repair materials has been observed in many cases [⁷,⁸].

Compatibility may be defined as the combination of the properties of repair materials and the substrate [⁹] which ensures that the combined system withstands the internal stresses and restrained volume change without cracking and bond failure over a designed period of time. In addition, the compatibility between overlay and substrate is mainly influenced by several factors comprising mechanical properties (compressive and flexural strengths, elastic modulus, etc.) and durability characteristics (drying shrinkage and capillary absorption) [⁸]. Consequently, the compatibility is the main criterion considered in the selection of repair material.

Despite the availability of various repair materials used to overcome the damage in the deteriorated structures, only few of them meet the demand for durable repair. The higher ductility and improved durability characteristics of Engineered Cementitious Composites (ECC), a special type of ultra-ductile fiber reinforced cementitious composite, suggests that this material is suitable for repair of concrete structures and can be used as an attractive alternative to conventional concrete overlay materials. ECC was originally invented at the University of Michigan in the early 1990s [¹⁰]. It is microstructurally tailored based on the micro mechanics design theory [¹⁰]. This group of material is characterized by high ductility with the strain capacity in the range of 3–7%, tight crack width approximately 60µm and moderate fiber volume fraction (typically 2%).

Due to environmental and economic reasons, there is a growing trend to use industrial by-products as supplementary materials or admixtures in the production of conventional high-performance and high-strength concrete mixtures. Several studies were conducted to investigate the properties of ECC incorporating pozzolanic materials such as, Fly Ash (FA), Silica Fume (SF), Metakaolin (MK), Ground Granulated Blast Furnace Slag (GGBFS) into ECC design. The majority of these experimental studies focus on the use of high volume of FA or binary blends of high volumes of FA and MK or SF, which have a high specific area. Zhu et al. [¹¹] investigated the effect of high volume of FA on the properties of ECC; the replacement level of FA was 50%, 60%, 70% and 80%. They concluded that increasing FA content increases remarkably the mid-span deflection and reduces the compressive and flexural strength. Additionally, Yang et al. [¹²] also indicated that the use of high FA content (up to 80% by weight) reduces the compressive strength of ECC, the crack width and the free drying shrinkage, and improve robustness (reduced variability) of tensile ductility. A recent study [¹³] has shown that the binary use of high FA content and MK improves significantly the mechanical properties and durability characteristics. In the same way, Zhu et al. [¹⁴] evaluated the effect of the binary use of high volume of FA and GGBFS, they found that GGBFS can increase drying shrinkage of ECC. Because of its high ductility and multiple cracking behavior, ECC has been proposed to be the most effective repair material [¹⁵–¹⁸]. When ECC is used as a repair layer over existing concrete substrate, its higher ductility and multiple cracking behavior can limit the internal stresses induced by drying shrinkage. Sahmaran et al. [¹⁹] reported that ECC can achieve adequate bond strength to other concretes even without surface preparation. Recently, Yıldırım et al. [¹⁸] have also found a good linear relationship between compressive strength and bond strength values in slant shear.

Among the various supplementary materials, Natural Pozzolan (NP) is the most commonly available mineral admixture in Algeria which is usually available in large quantities and at a fraction of the price of cement. NP has been extensively used as a partial replacement for cement in concrete to improve its mechanical properties and durability characteristics [²⁰]. To the best of the authors’ knowledge, however, no information is currently available on the influence of the NP replacement rate on the properties of ECC. Accordingly, the aim of this paper is to evaluate the effect of Natural Pozzolan content on the properties of Engineered Cementitious Composite as a repair material.

In this study, the “Natural Pozzolan/Portland Cement” ratio (NP/PC) ranges from 1.2 to 3.2 by weight. The experimental investigation includes the most properties influencing the compatibility between repair material and substrate concrete such as compressive and flexural strengths, elastic modulus, capillary absorption and drying shrinkage.

Experimental Investigation

Materials

The control matrix materials were composed of cement, natural pozzolan, silica sand and high-range water-reducing admixture (HRWRA). CEM I 42.5 Portland Cement (PC) used in the production of ECC mixtures is from the cement plant of Zahana (Algeria). The natural pozzolan of volcanic origin used was extracted from Bouhamidi deposit located at Beni-saf (in the south of Algeria). Physical properties and chemical composition of PC and NP are presented in Table 1. The silica sand with a maximum grain size of 300 mm (0.01 in.), a mean size of 110 µm (0.004 in.) and a fineness modulus of 1.4 was used to form the matrix.

A Polyvinyl Alcohol Fiber (PVA) produced in Japan Kuraray Co., Ltd., was used at a moderate volume fraction of 2% in this study. The dimensions of the fiber are 8 mm in length and 39 µm in diameter, with a tensile strength of 1600 MPa and a density of 1300 kg/m³. The mechanical and geometrical properties are illustrated in Table 2.

In order to evaluate the effect of natural pozzolan on the properties of ECC, five ECCs were elaborated with different content of NP (NP/PC range from 1.2 to 3.2) in this study as shown in Table 3. The water-cementitious materiel ratio (w/cm) was kept constant at 0.29 in all ECCs mixtures. Appropriate adjustments were conducted in the amount of HRWRA in each mixture to achieve consistent rheological properties for better fiber distribution and workability. As shown in Table 3, increasing the content of NP increased the HRWRA demand. The ECC mixture with NP/PC ratio of 3.2 had the highest required amount of HRWRA.

Mixing and curing

ECCs mixtures were made by the use of mortar mixer. The mixing was performed in laboratory temperature at 23±2°C and 50%±5% RH. Solid ingredients, including PC, NP and sand, were firstly mixed at 100 rpm for 1 minutes. Secondly, water and HRWRA were added and mixed at 150 rpm for 1 minute and then at 300 rpm for 2 min more. After that, the fiber (PVA) were slowly added and mixed at 150 prm for an additional 3 minutes. Finally, the mixtures were cast into molds and were then demoled after 24 h. All specimens except shrinkage specimens were stored in a curing room and immersed in water up to the age of the test.

Deformability test for fresh mortar matrix mixture using mini-slump flow

In this experimental study, the workability was evaluated by measuring the slump flow using mini-slump flow (Diameter D₀ = 10 cm) placed on glass plate. The flow cone was filled with mortar (without fiber) immediately after mixing without vibration due to the self-compacting properties of ECCs. The mixture tended to spread after lifting the flow cone. The ECC deformability factor G is calculated by Eq. 1.

(1)\mathrm{\Gamma }={\displaystyle \frac{{{\displaystyle D}}_{\mathrm{1}}-{{\displaystyle D}}_{\mathrm{0}}}{{{\displaystyle D}}_{\mathrm{0}}}},

where G is the deformability factor; is the average of two orthogonal diameter measurements and D₀ is the diameter of the bottom of the slump cone.

Specimen preparation and testing

For each mixture, several prism specimens (40×40×160 mm³) were carried out for the compressive and flexural strength, absorption and shrinkage tests. Cylinders measuring 50 mm in diameter and 100 mm in length were prepared for elastic modulus test. The following sections present the complete detailed testing program.

Compressive and flexural strengths

The compressive and flexural strengths’ tests were conducted at 3, 7, 28 and 90 days in accordance with the EN 12190-6 [²¹]. The reported results are the average of three flexural specimens and six compression tests.

Elastic modulus

Measurements of the elastic modulus were carried out using cylindrical specimen (100 mm in diameter and 50 mm in height). All mixtures were firstly cast into mold and demolded after 24 h. Then, the samples were immersed in water until the age of test (28 and 90 days). After that, the specimens were oven-dried at 105 °C for 24 h to calculate their density. An ultrasound test was used for measuring ultrasonic wave propagation velocity through the samples which depends on their density. Fig. 1 shows the transducers disposition through the specimen using the transmission direct method. In order to obtain reliable ultrasound measurements, a smooth diamond saw bond plane has been used to ensure a smooth surface. The dynamic elastic modulus can be calculated by the Eq. 2.

(2){{\displaystyle E}}_D=\rho V^{\mathrm{2}},

where E_D is the elastic modulus GPa; \rho is the density of dry specimens kg/m³; and V is the sound speed km/s.

Absorption

In order to investigate the durability properties, the absorption test was chosen in this study. Half-prism specimens 40×40×80 mm³ were prepared to determine the capillary absorption coefficient at 28 and 90 days in accordance with EN 1015-18 [²²]. At the end of 28 and 90 days, samples were firstly oven-dried at 105 °C for 24 h to obtain dried mass (W₁). All surfaces of the specimen except their bottom and top side were then wrapped with epoxy resin so that water penetration could only occur in one direction as shown in Fig. 2.

Shrinkage

For the drying shrinkage, three prism specimens with two embedded copper heads at two long ends are used for measurements as shown in Fig. 3. After 1 day curing in molds covered with plastic paper, the specimens were demolded and covered with an adhesive band at both ends in order to avoid evaporation of water and they were kept in laboratory at a temperature of 23±2 °C and 55±5% RH. A frame for shrinkage measurement equipped with a micrometer precision comparator. Figure 3 illustrates the position of specimen in the measurement frame. Shrinkage strain for all mixtures is measured up to 90 days.

Results and Discussion

Deformability test for fresh mortar

The incorporation of pozzolan materials such as fly ash, silica fume, and natural pozzolan modified significantly the deformability of the mortar due to their high specific area. In the present study, mini-slump flow test was conducted to evaluate the workability of ECCs mixtures without PVA fiber.

The w/cm was kept constant and a slight adjustment in the amount of HRWRA in all ECC mixtures in order to attain a flowability factor (G) of 3.4±0.4 [²³] without segregation and to achieve consistent rheological properties for better fiber distribution. The mini-slump flow test was conducted two times immediately after mixing. Figure 4 shows the slump flow spread measured for the ECC mixture, with an average of 42 cm (G= 3.2).

It should be noted that the flowability factor values (G) obtained in this study ranged from 3.1 to 3.3 with a good resistance against segregation and bleeding. It is also apparent from Table 3 that the HRWRA demand increases with an increase in natural pozzolan replacement level due to the higher surface area of NP particles compared to that of Portland cement.

Compressive and flexural strengths

Figure 5 displayed the compressive strength of ECCs mixtures with various natural pozzolan contents at the age of 3, 7, 28 and 90 days. Each data is an average of the compressive strength as determined from six prismatic specimens. As shown in Fig. 5, the compressive strength obtained of each mixture increased with age and curing with significant enhancing at 90 days. For example, when curing age extends from 28 to 90 days, compressive strength of ECC_1.2 and ECC_ 3.2 increased 25% and 30%, respectively, it can be attributed to the pozzolanic properties of natural pozzolan. The pozzolanic reaction leads to denser microstructure and higher compressive strength results. These are in agreement with several experimental results in cementitious materials [²⁰].

As seen in Fig. 5, the compressive strength of all mixtures decreases as the natural Pozzolan-Portland cement ratio increases. The highest compressive strength was obtained by ECC_1.2 (replacement 55% of cement) due to the high cement content. It should be noted that the use of high volume of natural pozzolan provides a drop in the strength values until NP/PC ratio of 2.2. For instance, the compressive strength of ECC_1.7, ECC_2.2, ECC_2.7 and ECC_3.2 decreases respectively 18%, 39%, 43% and 41% as compared to ECC_1.2 at 28 days. Meanwhile, natural pozzolan content became ineffective beyond NP/PC ratio of 2.2. Therefore, ECC_2.2, ECC_2.7 and ECC_3.2 mixtures have nearly the same compressive strength at 90 days as shown in Fig. 5.

Therefore, the lower strength for ECCs with high content NP could be explained by the following reasons. Firstly, the content of NP is relatively high in proportion to cement, so relative low cement content provided only limited Ca(OH)₂ for the secondary hydration of natural pozzolan, which resulting in relatively low compressive strength of matrix. The second reason is that the secondary hydration of NP can only reach a very limited reaction degree because of the lower (w/cm= 0.29) ratio of ECCs. However, at 75% replacement of cement (NP/PC= 3.2), the compressive strength at 28 days can also exceed the nominal compressive strength for Normal-strength concrete (30 MPa). Thus, ECCs with various natural pozzolan contents can be used in different civil engineering applications.

Figure 5 shows the flexural strength of ECCs mixtures with various natural pozzolan contents at 3, 7, 28, and 90 days. Each data is an average of the flexural strength as determined from three prismatic specimens. It is clear that the flexural strength decreased by increasing the natural pozzolan content at all ages, especially for ECC_2.7 and ECC_3.2 at early age. Both compressive strength and flexural strength show a similar trend as seen in Fig. 5. The various NP/PC ratios show a similar effect on the compressive and flexural strength. Flexural strength from 3 days to 28 days increases gradually as NP increases. The flexural strengths of ECC_1.2 and ECC_1.7 at the age of 28 days are 23.1 MPa and 21.6 MPa, but the strength only increased 0.7 MPa and 1.8 MPa from 28 days to 90 days respectively. However, there is an increase of 6 MPa for ECC_2.2, 5 MPa for ECC_2.7 and ECC_3.2 from 3 days to 28 days, which means that the high volume NP has a profound influence on the strength of ECC specimens. The reasons being explained this behavior is the secondary hydration, which is limited by the lower w/cm, still enhances the strength of ECC specimens. It can be seen that the flexural strength of ECCs is very higher than the flexural normal-strength concrete due to the strain hardening behavior and tensile ductility of ECC. ECC exhibits significant strain-hardening behavior and ductility under tension and deflection-hardening behavior under flexure. The pseudo strain-hardening behavior in ECC is achieved by sequential development of multiple tight crack widths of less than 60 mm, instead of continuous increase of the crack opening. This tight crack can be explained by the PVA fiber, the matrix and the interface between PVA fiber and matrix. Therefore, as the tensile load increases, the interfacial bonding between the fiber and matrix is stronger enough. In one word, while strain-hardening and ultra-high tensile strain capacity, ECC can sustain very large deformation without damage localization.

Elastic modulus

The elastic modulus and shrinkage strain are generally the important properties regarding the dimensional stability which is the most important factor influencing the compatibility between the repair materials and substrate concrete [⁸,²⁴,²⁵]. Therefore, a similar or lower E_D and shrinkage than that of typical concrete are required to achieve a durable repair. The elastic modulus of different ECCs mixtures produced in this study is illustrated in Fig. 6. Each data point form Fig. 6 is an average of the elastic modulus as calculated from two cylinder specimens. As seen in Fig. 6, the elastic modulus values varied from to 21.05 to 25.02 GPa at 28 days which were lower than that of normal-strength concrete due to the absence of large coarse aggregate [²]. These findings are in conformity with those reported by other researchers [²⁶].

It is apparent that the high volume NP effectively decreases the elastic modulus at all ages. When the NP/PC ratio increased from 1.2 to 3.2, the modulus decreased from 28.54 GPa to 23.3 GPa at 90 days. A slight increase of elastic modulus was observed at 90 days. For example, the elastic modulus of ECC_3.2 mixture increases from 21.05 GPa at 28 days to 23.3 GPa at 90 days. As a repair materiel, ECC can accommodate the internal stresses and the deferential volume change induced by restrained drying shrinkage without delamination of the interface due to the lower elastic modulus and the strain-hardening behavior. Additionally several researchers [⁷,¹⁵,¹⁶] noted that ECC is potentially an effective and good repair material because of its high ductility.

Water absorption

The results of capillary absorption coefficient are illustrated in Fig. 7. It can be clearly seen that the use of high volume pozzolan contents increases significantly the coefficient of capillary absorption at 28 days. For example, at 28 days, the coefficient K increases from 0.42 to 0.92 when the NP/PC ratio increases from 1.2 to 3.2. It should be noted that the higher compressive and flexural strength results correlate with the lower capillary absorption coefficient. The possible reason that explains the higher coefficient (K) values of ECCs mixture incorporating high volume NP content is the lower densification of the matrix due to the slow pozzolanic reaction of natural pozzolan and insufficient curing time. These results agree with those reported by Özbay et al. [¹³] when they investigated the mechanical properties of ECC incorporating high volumes Fly Ash and Metkaolin.

As displayed in Fig. 7, the capillary absorption coefficient of each mixture decreases considerably at 90 days. The coefficient (K) of ECC_1.2 mixture decreases from 0.42 at 28 days to 0.04 at 90 days. It is well known that, in general, this coefficient is directly related to the internal pore structure. The main reason for the significant enhancement of the capillary absorption is the sufficient curing period required for the pozzolanic reaction which reduced the permeable voids. The capillary pores are reduced by the formation of secondary C–S–H gel due to the pozzolanic activity, and hence the reduction in the capillary water absorption of ECC which enhanced the matrix densification and improve the microstructure. As shown in Fig. 7, only the mixtures ECC_1.2 and ECC_1.7 at 28 days are lower than the maximal limit required by EN 1504-3 (≤0.5) [²⁷]. Further, all mixtures meet the requirement specified by the EN 1504-3 at 90 days.

Drying shrinkage

The results of the free shrinkage deformation measurements of all ECCs mixtures until 90 days are shown in Fig. 8. Each point of Fig. 8 represents the average free drying shrinkage measurements of two specimens. The w/cm ration was kept constant at 0.29 in all ECCs mixture, so varying water requirement was not a factor for drying shrinkage. According to the results provided in Fig. 8, it appears clearly that the drying shrinkage deformation of ECCs produced in this study is higher than that of normal concrete which is the direct result engendered from the absence of coarse aggregate. The drying shrinkage of all ECCs mixtures evolved very fast at early age and got stable in later age. This was found in agreement with the results obtained by Yang et al. [²⁴] and Xinqi et al. [²⁸]. As seen in Fig. 8, the drying shrinkage of ECCs ranged from 490 to 1169 µm at 90 days which are very lower than those reported by others researchers [¹²,¹³] when they investigated the use of high volume Flay Ash in the production of ECCs. However, the ECC_1.2 mixture exhibits the lowest shrinkage value at 90 days. For example, at 55% replacement of cement (NP/PC=1.2), the drying shrinkage is 490 µm at 90 days, while those obtained by Yang et al. [¹²], and Özbay et al. [¹³] approximately were 1700 and 1000 µm, respectively. It should be noted also that the lowest shrinkage value correlate with the highest compressive strength and the lowest capillary absorption coefficient result. These lower shrinkage deformation values can be attributed to the high matrix densification which may prevent water evaporation.

The general trend in Fig. 8 shows that the use of high volume NP content increases the drying shrinkage in ECCs mixtures. These results can be explained by the following reasons. Firstly, at early age, the natural pozzolan was ineffective due to it slow pozzolanic reaction. This is consistent with the compressive strength results shown in Fig. 5 where the use of the NP decreases compressive strength at early age and will be higher beyond 28 days because of the pozzolanic properties of NP that increase the densification of the matrix. Secondly, the use of high volume NP in the production of ECCs increases their porosity and average pore diameter which may have worsened their microstructure and durability properties. Thirdly, NP can increase the amount surface water which can accelerate internal moisture evaporation due to the irregular particles shape. Fourthly, a possible mechanism contributing to the increasing of drying shrinkage in ECCs is the lower matrix densification due to shape of NP addition. The matrix densification is typically attributed to the shape, pozzolanic property, and micro-filer effect of NP.

This also confirmed the result of the capillary absorption. The capillary absorption coefficient was effectively reduced at 90 days due to the sufficient curing period required for the pozzolanic reactivity, forming additional C-S-H gel and leading to an enhanced microstructure and durability properties and decrease the porosity of ECC.

Conclusions

This paper presents the results of an experimental research study that investigates the effect of natural pozzolan content on the properties of engineered cementitious composite as repair material. The following conclusions can be drawn:

• The use of high volume natural pozzolan reduces the compressive and flexural strengths of ECCs at all ages. In addition, the compressive and flexural strengths of each ECC mixtures are significantly enhanced at 90 days due to the pozzolanic reaction.

• Due to the strain-hardening characteristic, the flexural strengths are significantly higher than that of normal-strength concrete.

• At 28 days, the strengths of ECC_1.2 and ECC_1.7 are 56 and 46 MPa, respectively, which can meet the requirement for class R4 according the standard EN 1405-3. In contrast, all ECCs mixtures' of this study showed a strengths higher than 40 MPa at 90 days, which can be used in many different applications.

• The lower values of elastic modulus of ECCs mixtures used in this study are desirable for concrete repair, because they prevent the internal stresses induced by restrained shrinkage.

• Increasing the content of natural pozzolan in the ECCs mixtures worsened their durability properties at early age by increasing significantly their capillary absorption coefficient. On other hand, remarkable improvement was found after a curing period of 90 days which is attributed to the high densification of matrix.

• Increasing the content of the NP increases the drying shrinkage. But, the results obtained are significantly lower than those reported by other researchers which have studied the effect of other mineral additives (Fly Ahs, Silica Fume, Metakaolin, etc.) on the shrinkage of ECC.

• From the results presented in this study, it can be concluded that ECC is potentially a good repair material according to the standard EN 1405-3 [²⁷] due to its appropriate properties in terms of mechanical properties, durability characteristic and dimensional stability with the existent substrate concrete.

References

[1] Matthews S. CONREPNET: Performance-based approach to the remediation of reinforced concrete structures: Achieving durable repaired concrete structures. Journal of Building Appraisal, 2007, 3(1): 6–20

[2] Zhou J. Performance of engineered cementitious composites for concrete repairs. PhD Thesis, Delft University of Technology, Netherlands, 2011

[3] Mallat A, Alliche A. Mechanical investigation of two fiber-reinforced repair mortars and the repaired system. Construction & Building Materials, 2011, 25(4): 1587–1595

[4] Al-Zahrani M, Maslehuddin M, Al-Dulaijan S, Ibrahim M. Mechanical properties and durability characteristics of polymer-and cement-based repair materials. Cement and Concrete Composites, 2003, 25(4): 525–537

[5] Emberson N K, Mays G C, Mays G C. Significance of property mismatch in the patch repair of structural concrete. Part 3: Reinforced concrete members in flexure. Magazine of Concrete Research, 1996, 48(174): 45–57

[6] Li M. Multi-scale design for durable repair of concrete structures. PhD Thesis, University of Michigan, USA, 2009

[7] Li V C, Horii H, Kabele P, Kanda T, Lim Y. Repair and retrofit with engineered cementitious composites. Engineering Fracture Mechanics, 2000, 65(2): 317–334

[8] Pattnaik R. Investigation into compatibility between repair material and substrate concrete using experimental and finite element method. PhD Thesis, Clemson University, USA, 2006

[9] Hassan K, Brooks J, Al-Alawi L. Compatibility of repair mortars with concrete in a hot-dry environment. Cement and Concrete Composites, 2001, 23(1): 93–101

[10] Li V C. On engineered cementitious composites (ECC): a review of the material and its applications. Journal of Advanced Concrete Technology, 2003, 1(3): 215–230

[11] Zhu Y, Yang Y, Dang H, Yao Y. Mechanical properties of engineered cementitious composites with high volume fly ash. Journal of Wuhan University of Technology-Materials Science Edition, 2009, S1: 166–170

[12] Yang E H, Yang Y, Li V C. Use of high volumes of fly ash to improve ECC mechanical properties and material greenness. ACI. Journal of Materials, 2007, 104(6): 620–628

[13] Özbay E, Karahan O, Lachemi M, Hossain K, Duran Atiş C. Investigation of Properties of Engineered Cementitious Composites Incorporating High Volumes of Fly Ash and Metakaolin. ACI Materials Journal, 2012, 109(5): 565–571

[14] Zhu Y, Yang Y, Yao Y. Use of slag to improve mechanical properties of engineered cementitious composites (ECCs) with high volumes of fly ash. Construction & Building Materials, 2012, 36: 1076–1081

[15] Lim Y M, Li V C. Durable repair of aged infrastructures using trapping mechanism of engineered cementitious composites. Cement and Concrete Composites, 1997, 19(4): 373–385

[16] Wang S, Li V C. High-early-strength engineered cementitious composites. ACI Materials Journal, 2006, 103(4): 97–105

[17] Li V C. High performance fiber reinforced cementitious composites as durable material for concrete structure repair. International Journal for Restoration, 2004, 10(2): 163–180

[18] Yıldırım G, Sahmaran M, Al-Emam M, Hameed R, Al-Najjar Y, Lachemi M. Effects of Compressive Strength, Autogenous Shrinkage, and Testing Methods on Bond Behavior of High-Early-Strength Engineered Cementitious Composites. ACI Materials Journal, 2015, 112(4): 409–418

[19] Sahmaran M, Yucel H E, Al-Emam M, Yaman I O, Guler M. Bond Characteristics of Engineered Cementitious Composite Overlays. In: Transportation Research Board 92nd Annual Meeting, 2013, 13–1578

[20] Ghrici M, Kenai S, Said-Mansour M. Mechanical properties and durability of mortar and concrete containing natural pozzolana and limestone blended cements. Cement and Concrete Composites, 2007, 29(7): 542–549

[21] EN 12190-6. Products and systems for the protection and repair of concrete structures-Test methods- Determination of compressive strength of repair mortar, 1999

[22] EN 1015-18. Methods of test for mortar for masonry, Part 18: Determination of water absorption coefficient due to capillary action of hardened mortar, 2003

[23] Lepech M D, Li V C, Robertson R E, Keoleian G A. Design of green engineered cementitious composites for improved sustainability. ACI Materials Journal, 2008, 105(6): 567–575

[24] Yang Y, Yao Y, Gao X, Deng H, Yu P, GAO X, Deng H, Yu P. Shrinkage reducing measures for engineering cementitious composites. Wuhan University Of Technology-Materials Science Edition, 2008, 23(6): 907–911

[25] Decter M. Durable concrete repair—Importance of compatibility and low shrinkage. Construction & Building Materials, 1997, 11(5): 267–273

[26] Li M, Li V C. High-Early-Strength Engineered Cementitious Composites for Fast, Durable Concrete Repair-Material Properties. ACI Materials Journal, 2011, 108(1): 3–12

[27] EN 1504-3. Products and systems for the protection and repair of concrete structures- Definitions, requirements, quality control and evaluation of conformity-Part 3: Structural and non-structural repair; 2006

[28] Xinqi M, Zhao T, Zhang P. Optimization of shrinkage and crack resistance performance of Engineered Cementitious Composites (ECC). Electric Technology and Civil Engineering (ICETCE), International Conference on, IEEE, 2011, 6: 534–538

RIGHTS & PERMISSIONS

Higher Education Press and Springer-Verlag Berlin Heidelberg