# Durability and Time-Dependent Properties of Low-Cement Concrete

^{1}

^{2}

^{3}

^{4}

^{*}

## Abstract

**:**

^{3}, the former with very plastic consistency and the latter with dry consistency, which were combined with a large spectrum of cement replacement rates (up to 70%), through adding fly ash and limestone filler, and with different compactness levels. The main objectives were to study the influence of the formulation parameters on the properties: shrinkage and creep, accelerated carbonation and water absorption, by capillarity, and by immersion. The lifetime of structures produced with the studied LCC was estimated, considering the durability performance, regarding the carbonation effect on the possible corrosion of the steel reinforcement. LCC mixtures with reduced cement dosage and high compactness, despite the high W/C ratios, have low shrinkage and those with higher strength have reduced creep, however depending on W/C

_{eq}ratio. Those mixtures can be formulated and produced presenting good performance regarding carbonation resistance and, consequently, a long lifetime, which is mandatory for a sustainable construction. LCC with 175 kg/m

^{3}of cement dosage is an example with higher lifetime than current concrete with 250 kg/m

^{3}of cement; depending on the XC exposure classes (corrosion induced by carbonation), the amount of cement can be reduced between 37.5% and 42%, since the LCC with 175 kg/m

^{3}of cement allows reducing the concrete cover below the minimum recommended, ensuring simultaneously the required lifetime for current and special structures.

## 1. Introduction

_{2}emissions are released into the atmosphere for each ton of clinker produced [2]. Therefore, it is mandatory to develop new approaches allowing the production of structures using eco-efficient concrete with improved durability.

_{2}by 2030 and up to 8% by 2050 are expected. Associated with this measure, it is equally important to congregate the mechanical, time-dependent and durability properties, and the lifetime requirements of concrete structures. Currently, concerns about the durability and long-term performance of concrete are obstacles that limit the use of some additions in many applications. Water absorption, carbonation depth, shrinkage and creep performances are some of the parameters that can be used as indicators of durability and long-term performance of concrete.

_{0})-Equation (1), over age t is predicted by Eurocode 2 (EC2) [13] and by Model Code 2010 (MC10) [14], according to the following parameters: loading age (t

_{0}); type of cement; cross-sectional dimensions; compressive strength of concrete (f

_{cm}); and thermo-hygrometric conditions (relative humidity and temperature). The notional creep coefficient, φ0, is obtained from Equation (2) and considers those parameters, being the evolution curve obtained from Equation (3).

_{cs}, or total shrinkage, is the dimensional variation mainly caused by the combined effects of the drying shrinkage, ε

_{cd}, and the autogenous shrinkage, ε

_{ca}. However, the sum of drying and autogenous shrinkage values is a simplification, since both parameters are caused by the reduction of the relative humidity (RH) of the concrete. Drying shrinkage occurs due to evaporation at the concrete’s surface, while autogenous deformation is caused by partial emptying of the gel pores as a consequence of cement hydration [15,16,17]. Nevertheless, for concrete with reduced cement dosage, the major component is drying shrinkage, since autogenous component is very low. According to EC2 [13] and MC10 [14], the evolution of ε

_{cd}with age depends on the concrete strength, type of cement, geometry, curing conditions and initial age of drying. In EC2, the evolution of ε

_{ca}with age depends only on the concrete strength, while in MC10 it depends on both concrete strength and cement type. The drying shrinkage component, ε

_{cd}(t), can be estimated, according to EC2, using Equations (4)–(6). In these, the estimated drying shrinkage, ε

_{cd,0}, considers the most influent parameters mentioned above and β

_{ds}(t, t

_{s}) defines the shape of the shrinkage evolution curve.

^{226}Ra), thorium (

^{232}Th) and potassium (

^{40}K), and their specific activity may exceed the average specific activity [28]. The addition of fly ash to Portland cement can have an effect on the highest concentrations of natural radionuclides. Consequently, it is prudent to control the fly ash addition into cementitious matrix, by limiting its proportion.

## 2. Research Significance

## 3. Experimental Program

#### 3.1. Concrete Formulation

^{3}), with a target consistency of class S3 (very plastic consistency); (ii) low-cement (LC) series, with a reduced dosage (250 kg/m

^{3}), varying the effective cement dosage in substitution regime with the addition of limestone filler and fly ash, with a dry consistency and low cohesion.

^{3}), the water/cement (W/C) ratio consequently varies. The substitution of cement by additions was defined giving priority to the filler until a maximum equal to the cement mass was reached, followed by the complement of fly ash, when necessary, until the dosage for the binder powder was reached. A subseries of C concrete was also formulated, named C_B, varying the compactness values from 0.81 in C series to 0.835 and to 0.855 in mixtures C200B and C175B (Table 1). Once the parameters of the binding matrix were defined, the methods of the Faury’s granulometric curve [48,50] and the Alfred’s curve [51], being the latter developed by Funk and Dinger [52], were used to optimize the proportions of the aggregates, thus varying the aggregates proportions [50].

^{3}) and the amount of binder powder (having 250 kg/m

^{3}in LC concrete and 350 kg/m

^{3}in C concrete). In the LC series, formulation by the Alfred’s curve (mixtures LC75, LC125, LC175 and LC250) was considered. The other series or subseries (LC_F, C and C_B) were formulated using the Faury’s reference curve. In LC250 mixture, a compactness variation, between 0.86 and 0.80, and consequently the W/B ratio were also considered for LC mixture with 250 kg of cement dosage (resulting in LC250 and LC250A mixtures). The dosages of all constituents mentioned are shown in Table 1.

#### 3.2. Workability and Mechanical Properties of Concrete

_{cm7,}f

_{cm28}, f

_{cm56}(compressive strength measured at 7, 28 and 56 days respectively). At 28 days of age, the following properties were also characterized: splitting tensile strength, f

_{ctm,sp}, according to EN 12390-6 [56] in three prismatic test specimens of 100 × 100 × 200 mm

^{3}; flexural strength, f

_{ctm,f}, following the standard EN 12390-5 [57] in two prismatic test pieces of 100 × 100 × 400 mm

^{3}; the Young’s Modulus, E

_{cm}, according to the specification of National Laboratory of Civil Engineering (LNEC) E-397 [58] in two prismatic specimens of 100 × 100 × 400 mm

^{3}. The average values of that properties are shown in Table 2.

#### 3.3. Durability and Time-Dependent Tests

^{3}prismatic specimens (Figure 1), and the total shrinkage, ε

_{cs,}(Figure 1), was characterized according to the specification LNEC E398 [60], testing two twin prismatic specimens of 100 × 100 × 500 mm

^{3}for each concrete.

^{3}prismatic specimens; (ii) water absorption by immersion, which was carried out on cubic specimens with 100 mm edge and according to LNEC E394 specification [62]; and (iii) accelerated carbonation test, carried out following the LNEC E391 specification [63], using two cylindrical samples with 100 mm diameter and 50 mm height, for each considered exposure period (7, 14, 28, and 42 days).

## 4. Results and Discussion

#### 4.1. Shrinkage

_{cs}, measured in the test specimens of each mixture, is shown in Figure 3. The LC series concretes (with 250 kg of binder powder) have developed generally reduced shrinkage values, between 215 and 430 μm/m at 210 days, although they tend to increase with cement dosage increase. Concretes of C series (with 350 kg of binder powder) have values between 500 and 570 μm/m at 210 days, in concrete with a compactness of 0.81 and tends to gradually reduce with compactness increase, in C200 and C175B concretes, although having similar value of equivalent cement, their compactness is 0.84 and 0.86, respectively.

_{ds}(t,t

_{0}), Equation (6), the value of the second part of the denominator was adjusted, from 0.04 to a β

_{shape}coefficient, Equation (7), which can assume values of 0.06 for concretes of C series and 0.08 for concretes of LC series, allowing a better adaptation of the evolution with age (Figure 4b), in comparison to experimental results. With this adjustment, the shrinkage values predicted at 210 days become about 88% to 91% of the value at infinite time. It should be noted that the autogenous shrinkage component is very low in this type of concrete, being the prediction less than 10% in all concrete and less than 5% in most mixtures.

^{−6}. The dispersion of two concretes to that correlation (Figure 5b) suggests that there are even other parameters influencing the shrinkage amplitude.

#### 4.2. Creep

_{c}(t) (Figure 6), with the load having been applied at 28 days of age to assure a proper maturity of concrete. Since an early loading age promotes higher creep deformation for concrete in general, for this type of concrete it is advisable that the load occur at minimum age of 28 days, considering the lower evolution of strength and maturity of these concretes. The creep was evaluated in all concretes, including the LC and LC_F series (with variation of the granulometric curve), Figure 6b, with only C75 and C125 concretes being excluded since they have reduced mechanical performance for structural purposes. Regarding the influence of the granulometric curve, used in the formulation of LC concrete, on concrete creep, no apparent influence was noticed. The concretes with lower equivalent cement dosage (LC75 and LC125, with C

_{eq}of 85 and 125, respectively) have similar evolutions and amplitudes, with creep coefficients close to 1.6 at 210 days of age. LC175 concrete has a smaller creep amplitude compared to those mentioned (creep coefficient close to 1.3 at 210 days of age), as expected, because it has a higher cement dosage and greater strength. Despite the reduced influence of the granulometric curve is proven in creep coefficient, the creep deformation is lower in concrete with Alfred’s curve, since the Young’s modulus of those concretes (LC75, LC125 and LC175) are 11% to 30% higher than those formulated by the Faury’s curve (LC75F, LC125F and LC175F). That difference is higher in concretes with a lower cement dosage and decreases with the increase of its dosage. With the exception of LC250A concrete (concrete with high W/B ratio and reduced compactness, 0.80) and C200 (concrete with compactness of 0.84), which showed a creep coefficient at 210 days, from 1.92 to 2.12, respectively. The remaining concretes show a similar evolution and amplitude, whose coefficient is around 1.6 at 210 days. Part of the influence of these values is evidenced by the different mechanical strengths, as mentioned.

_{c}(t,t

_{0}), Equation (3), the exponent of that ratio, α

_{t}, was adjusted from 0.30 to 0.15, Equation (8), obtaining a better adaptation of the evolution with age (Figure 7b). With this adjustment, the values of the creep coefficient, predicted at 210 days of age, become about 84% to 87% of the value at infinite time.

_{eq}), which represents the mass ratio between water and equivalent cement, presents the best fit (Figure 9).

_{cm}) coefficient, Equation (9), the result of the correlation obtained was incorporated in determining this coefficient. Due to the verified dispersion, the amplitude of the correlation was reduced in order to ensure conservative predictions, resulting in a new proposal to predict coefficient β(f

_{cm}), expressed by Equations (10) and (11).

_{eq}ratio, the creep curves of the characterized concrete have much better adjustment compared to experimental results (Figure 11).

#### 4.3. Water Absorption by Immersion

_{eq}also has an important influence, albeit less than the previous parameter, since as the equivalent cement increases, this ratio decreases, and the calcium silicate hydrates (CSH) gel resulting from hydrated cement occupies the voids inside the matrix, also reducing absorption, because the matrix is more dense and less porous. The ratio that incorporates compactness and W/C

_{eq}was studied, which provides the best correlation, and this relation is shown in Figure 13a. The high correlation between immersion absorption and this relation is shown in Figure 13b.

#### 4.4. Capillary Water Absorption

_{i}, Sa(t

_{i}), in mg/mm

^{2}.

^{3}, concrete LC250A have reduced compactness of 0.8, being the main reason for high capillary absorption.

^{3}of fly ash in the paste, while the compactness of LC125 concrete is 0.86 but does not contain fly ash. Due to the significant difference between the compactness of the two concretes, it would be expected that the difference between the capillarity absorption values would be significant. This situation did not occur, thanks to the presence of fly ash that allows the reduction of absorption by capillarity.

^{3}, and approximately equal compactness, however differing on powder content (250 kg/m

^{3}on LC175 and 350 kg/m

^{3}on C175B) and on fly ash content (C175B contains 75 kg/m

^{3}of fly ash). The combination of fly ash with cement may be associated with that improvement in C175B binder paste, because this addition allows the development of new compounds that fill the pores of concrete matrix.

_{a}(in milligrams per square millimeter) as a function of the square root of time, obtained for each mixture, as well as the slope that expresses the capillary absorption coefficient of the concrete. According to Browne’s classification cited in Coutinho [4]: high quality for concretes whose capillary absorption coefficients, S

_{a,}are less than 0.1 mg/(mm

^{2}·min

^{0.5}); medium quality for concretes whose coefficients are between 0.1 e 0.2 mg/(mm

^{2}·min

^{0.5}). It can be seen that C75 concrete can be classified as medium quality, C250 starts with medium quality and obtains a better classification over time, while the rests are classified as high quality.

#### 4.5. Carbonation

_{d}, in millimeters. Looking at the carbonation development curves along the square root of time (Figure 18), it appears that the carbonation speed, in most of the characterized concrete, is practically constant over square root of time. For a linear time scale, the speed is higher in the first days and tends to be slower over time, because after carbonation, the resulting products occupy the empty spaces in the pores of the concrete matrix and hinder the diffusion of carbon dioxide in the concrete, decreasing thus the carbonation rate.

_{d}after 42 days of exposure to carbon dioxide and W/C

_{eq}, whose correlation coefficient, R

^{2}, is approximately 0.92.

^{3}of binder powder, being that dosage 350 kg/m

^{3}in C series (Table 1). Maintaining the compactness, there is a higher linear but inverse correlation between the carbonation depth, C

_{d}, and the equivalent cement dosage (Figure 20).

_{2}necessary to consume all the remaining CH, thereby facilitating the decrease of pH. On the other hand, the positive effect is that from this reaction results in a denser structure in the hardened cement paste, which will hinder the diffusion of carbon dioxide and thus leads to slower carbonation speeds. Due to this situation, the dosage of fly ash is generally limited. The recommended proportions of cement replacement are of 0% to 40%, according to Teixeira et al. [31], as they argue that its use of large volumes presents some problems and one of them is the decrease of the pH concrete that leads to carbonation problems.

^{2}equal to 0.84. This correlation is frequently analyzed in carbonation studies, but according to Neville [19], this approach is a gross, but debatable, simplification. Changes in the composition parameters can improve the mechanical properties, however, they can reduce the chemical durability.

^{3}, with only 175 kg/m

^{3}of cement, and with high carbonation resistance.

#### 4.6. Lifetime of Structures and Minimum Concrete Cover Regarding Carbonation

_{min,dur}, to assure the required resistance against corrosion of the reinforcement during the intended service life for reinforced concrete structures (corrosion induced by carbonation) and to predict the service lifetime of the reinforced concrete structures using the developed concretes and the standard covers. Those calculations were based on the degradation model by corrosion of reinforcements, developed by Tuutti, and on the recommendations described on LNEC specification E465 [70]. Two types of structures were considered: (i) current structures with an intended service lifetime (t

_{g}) equal to 50 years, with a reliability class RC2 (structural class S4), which corresponds to a safety factor γ equal to 2.3; (ii) special structures with a t

_{g}equal to 100-year-old, with a reliability class RC3 (structural class S5), which corresponds to a safety factor γ equal to 2.8.

_{di}, at several days of exposure to carbon dioxide, with a concentration, C

_{acel}, approximately equal to 90 × 10

^{−3}kg/m

^{3}, the carbonation resistance, R

_{C65}(kg·year/m

^{5}), was determined using Equation (12). The results are shown in Table 4.

_{ic}, is the difference between the intended service lifetime for the reinforced concrete structure, t

_{g}, and the propagation time, t

_{p}, affected by the safety factor mentioned above, see Equation (13). The propagation time depends of the environmental exposure class and was considered the minimum accordingly to the specification of LNEC E465 (Table 5).

_{min,dur}, is determined using Equation (14) and considering a time equal to t

_{ic}(Table 6 and Figure 22). The result is the carbonation depth, C

_{di}, for those conditions, which corresponds to the c

_{min,dur}, k

_{0}is a factor related to the test conditions and is equal to 3, t

_{0}is the reference period and is equal to 1 year, k

_{2}is related to concrete curing and assumes a value of 1, the parameters k

_{1}and n, range between 0.2 and 0.41, and between 0.09 and 0.18, respectively.

_{min,dur}, using some concretes are impractical, in particular, structures and structures located in environmental exposure class XC4. The LC75, C75, LC125 and C125 concretes require, in most cases, a minimum cover higher than the minimum value recommended by EC2, with differences ranging between 5 and 84 mm, for current structures, and between 10 and 128 mm, for special structures, depending on the environmental exposures’ classes. These results show that those concretes are not appropriate, or in certain cases are not the best option, to provide the proper protection against corrosion. On the other hand, the LC175, C175B, LC250, C200B and C250 concretes provide the proper resistance regarding carbonation, and in a high number of situations, have a higher resistance than that considered in EC2, since the minimum covers required are lower than those presented in the code, achieving a difference up to 17 mm.

^{3}does not have a significant influence on the carbonation resistance if mixtures have a relatively low compactness (Figure 23b,d). In this analysis, it is quite evident the positive influence of increased compactness, because a lower compactness implies a higher concrete cover, even if a higher dosage of cement is used. Using mixtures with a 350 kg/m

^{3}of total powder (C series) is possible to slightly reduce the required compactness to achieve a similar carbonation resistance, comparatively with the produced concretes with 250 kg/m

^{3}of total powder (LC series), because higher quantities of powder improve the workability, which may reduce the porosity of the matrix [64].

_{eq}ratio reflects both effects analyzed above, compactness and equivalent dosage of cement, in one parameter. This ratio was related with c

_{min,dur}and it is clear that a ratio above 0.72 increases significantly the concrete cover required to protect the reinforcement steel (Figure 23). This limit is a slightly higher than those recommended in EN 206 (Table 7), meaning that there is a margin for optimization if the constituents and the distribution of the particles size were properly defined. The correlation presented in Figure 24 also allows both effects to be considered, the compactness (that is inversely related with W/B ratio) and the equivalent cement dosage.

^{3}of cement, which is also lower than the minimum standard recommendation of 280 kg/m

^{3}for XC2 and XC3 and 300 kg/m

^{3}for XC4. So, the quantity of cement can be reduced by between 37.5% to 42%, depending on the environmental exposure classes XC. These results are very important because they have significant impact on the structures cost and simultaneously demonstrate that this concrete is clearly eco-friendlier.

_{ic}value, knowing the remaining variables, and in this case C

_{di}was considered equal to the minimum cover presented in EC2. Knowing the t

_{ic}and t

_{p}values, the service lifetime, t

_{g}, was determined using Equation (13).

_{C65}, more than enough for the exposure class XC, having a margin to decrease the minimum cover used in reinforced concrete structures. On XC2 conditions, the service lifetime values are quite high because the carbonation depth, C

_{d}, is very low in terms of environmental conditions. For special structures and under XC4 in wet regime conditions, only the LC175 and C250 presents a proper performance, since they are the only ones with a predicted service lifetime higher than 100 years.

^{3}. Nevertheless, it is generally possible to produce concretes with low-carbon cements that provide a proper performance against carbonation and, consequently, a long service life, which is a major step to achieve a more sustainable construction sector.

## 5. Conclusions

- Shrinkage: (i) LCC concrete with high compactness of 0.86 and reduced powder dosage (250 kg/m
^{3}) promotes reduced shrinkage, tending to increase with the increase of cement dosage; however, in concrete with powder dosage of 350 kg/m^{3}, the increase of compactness tends to gradually decrease shrinkage; (ii) due to the inadequacy of the EC2 prediction of shrinkage, compared to experimental values, a correction is proposed to improve the curves development, where a β_{shape}coefficient assumes different values (0.06 for concrete with powder of 350 kg/m^{3}and 0.08 for concrete with powder of 250 kg/m^{3}); (iii) beyond the parameters considered by the concrete codes, the concrete compactness has a noticeable influence on the amplitude of concrete shrinkage, mainly when combined with reduced binder powder (250 kg/m^{3}) and very reduced cement dosage, where the experimental/prediction ratio of shrinkage can go down to 0.4. - Creep: (i) the granulometric reference curve (Faury vs. Alfred), in concrete with reduced binder powder (250 kg/m
^{3}), does not have a relevant influence on the evolution and amplitude of creep coefficient; (ii) similarly to the known behavior of current concrete, the creep coefficient is highly influenced by the concrete strength; thus, LCC presents reduction of creep coefficient for concrete with high compactness (0.86) and higher cement dosage (175 kg/m^{3}), which has also higher strength; (iii) a divergence between the shape of the creep curve experimentally obtained and that according to EC2 is noticeable; however, the shape of the creep curve can be improved significantly by adjusting the α_{t}coefficient on β_{c}(t,t_{0}) parameter, from 0.30 to 0.15, for LCC; (iv) there is a huge difference between experimental and EC2 predicted values for the creep of LCC, mainly in concretes with lower cement dosage and with lower compactness (0.80 to 0.81), thus with higher W/B ratio, the creep being ratio experimental/code around 0.3; (v) W/C_{eq}ratio has a significant influence on that difference, therefore, a corrective parameter is proposed to be included on the β (f_{cm}) coefficient of EC2 to significantly improve the code prediction, namely ${\mathsf{\beta}}_{\mathrm{Ceq}}=2.5\text{}\times \text{}{\left(\mathrm{W}/\mathrm{Ceq}\right)}^{1.5}$, which was obtained by correlation analysis. - Water absorption by immersion: (i) the increase of compactness has a great influence on the reduction of water absorption, since the values for concretes with lower compactness (0.80 to 0.81) are close to 15% and those values reduce to below 10% for concretes with compactness of 0.86; (ii) the W/C
_{eq}ratio also has an influence on absorption, although it is less significant; thus, the relation that incorporates compactness and that ratio, (W/C_{eq})^{0.2}/Compactness^{6}, proved by correlation analysis, has high influence on water absorption. - Water absorption by capillarity: (i) high compactness of LCC combined with higher cement dosage significantly reduces the capillary absorption; (ii) fly ash addition as partial replacement of cement also promotes a significant decrease in capillary absorption; however, its excessive dosage may jeopardize the concrete performance regarding capillarity; (iii) the capillary coefficients of the LCC characterized allow all concretes to be classified as high quality, except the one with reduced compactness (0.81) and very reduced cement dosage (75 kg/m
^{3}). - Carbonation resistance: (i) maintaining the cement dosage, compactness increase has a significant influence on reducing carbonation depth, since the LC series (concrete with high compactness of 0.86 and with 250 kg/m
^{3}of binder powder) exhibits much lower carbonation depth than the corresponding C series (concrete with lower compactness and 350 kg/m^{3}of binder powder); (ii) maintaining the binder dosage, the carbonation depth decreases with the increase of cement or equivalent cement dosages, since it reduces the W/C_{eq}ratio; (iii) the higher the amount of fly ash incorporated in the concrete, replacing cement dosage, the lower the carbonation resistance, because it increases the carbonation velocity; (iv) it is possible to produce concrete with good structural performance, with low binder powder of 250 kg/m^{3}and only 175 kg/m^{3}of cement dosage, developing higher carbonation resistance, in circa 10%, than current formulation concrete with 250 kg/m^{3}of cement dosage and binder powder of 350 kg/m^{3}. - Minimum cover required to avoid corrosion induced by carbonation: (i) it is necessary to use a minimum cement dosage, since only concretes with cement dosage equal or higher than 175 kg/m
^{3}(even though with very different formulation parameters) have adequate resistance to carbonation for general exposure; for those concretes the minimum required covers are lower than those presented in EC2, reaching differences of up to 17 mm; (ii) the compactness increase has also high influence on reducing the minimum cover, since it increases the concrete strength and carbonation resistance; reducing the concrete compactness implies increasing the cover, even if higher cement dosage is used; the LCC with 175 kg/m^{3}of cement and compactness of 0.86 presents much higher resistance to carbonation compared to that of all formulated concrete, including those with equivalent cement dosage between 200 and 250 kg/m^{3}. - Lifetime of structures due to carbonation exposure: (i) higher cement dosages promotes longer lifetime; concretes with at least 175 kg/m
^{3}of cement dosage have, submitted to XC2 and XC3 conditions, service lifetime values above the minimum, for current (50 years) and special (100 years) structures and, for XC2, the values are quite high; (ii) for special structures and under XC4 in wet conditions, only the LC175 and C250 have adequate performance, the first due to the high compactness and the latter due to higher cement dosage, being the only mixtures with an expected lifetime of more than 100 years. - LCC mixtures with a good performance and a long lifetime: (i) concrete with at least 175 kg/m
^{3}of cement dosage reveals adequate combined mechanical, time-dependent and durability performances; (ii) concrete LC175 (with high compactness of 0.86 and powder dosage of only 250 kg/m^{3}) is revealed to be the most eco-efficient of the concretes studied herein, since for current and special structures, and for any type of XC exposure, it is possible to reduce the cover below the standard minimum, presenting a long lifetime; (iii) the amount of cement can be reduced between 37.5% and 42%, depending on the environmental exposure classes XC, comparing the LCC concrete which contains only 175 kg/m^{3}of cement with the minimum recommendation of 280 kg/m^{3}, for XC2 and XC3, and 300 kg/m^{3}for XC4.

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

- Ecra (European Cement Research Academy). Calcined Clay: A Supplementary Cementitious Material with a Future. Available online: https://ecra-online.org/fileadmin/ecra/newsletter/ECRA_Newsletter_3_2019.pdf (accessed on 14 July 2020).
- Colaço, R. Reduce the Environmental Impact of Cement (In Portuguese). Constr. Mag.
**2019**, 90, 12–14. [Google Scholar] - CEMBUREAU. Cementing the European Green Deal—Reaching Climate Neutrality along the Cement and Concrete Value Chain by 2050. Available online: https://cembureau.eu/media/1948/cembureau-2050-roadmap_final-version_web.pdf (accessed on 14 June 2020).
- Coutinho, J.S. Improving the Durability of Concrete by Treating Formwork, 1st ed.; FEUP: Porto, Portugal, 2005. (In Portuguese) [Google Scholar]
- Bažant, Z.P. Prediction of Concrete Creep and Shrinkage: Past, Present and Future. Nucl. Eng. Des.
**2001**, 203, 27–38. [Google Scholar] [CrossRef] - Neville, A.M. Properties of Concrete, 5th ed.; Pearson: London, UK, 2012. [Google Scholar]
- Costa, H. Structural Concretes of Light Aggregates. Applications in Prefabrication and Reinforcement of Structures. Ph.D. Thesis, University of Coimbra, Coimbra, Portugal, 2012. (In Portuguese). [Google Scholar]
- Lopez, M. Creep and Shrinkage of High Performance Lightweight Concrete: A Multi-Scale Investigation. Ph.D. Thesis, Georgia Institute of Technology, Atlanta, GA, USA, 2005. [Google Scholar]
- Klausen, A.E.; Kanstad, T.; Bjøntegaard, Ø.; Sellevold, E. Comparison of Tensile and Compressive Creep of Fly Ash Concretes in the Hardening Phase. Cem. Concr. Res.
**2017**, 95, 188–194. [Google Scholar] [CrossRef] - Chu, S.H. Effect of Paste Volume on Fresh and Hardened Properties of Concrete. Constr. Build. Mat.
**2019**, 218, 284–294. [Google Scholar] [CrossRef] - De Sousa Coutinho, A. Concrete Manufacturing and Properties; LNEC: Lisbon, Portugal, 2006; Volumes 1–2. [Google Scholar]
- Lopez, M.; Kahn, L.F.; Kurtis, K.E. Effect of Internally Stored Water on Creep of High-Performance Concrete. ACI Mat. J.
**2008**. [Google Scholar] [CrossRef] - EN 1992-1-1. Eurocode 2—Design of Concrete Structures Part 1-1: General Rules and Rules for Buildings; CEN: Brussels, Belgium, 2010. [Google Scholar]
- CEB-FIP Model Code. First Complete Draft-Vol.1. In fib–International Federation for Structural Concrete; EPFL: Lausanne, Switzerland, 2010. [Google Scholar] [CrossRef]
- Lura, P.; Bisschop, J. On the Origin of Eigenstresses in Lightweight Aggregate Concrete. Cem. Concr. Compos.
**2004**, 26, 445–452. [Google Scholar] [CrossRef] - Lura, P.; Jensen, O.M.; Van Breugel, K. Autogenous Shrinkage in High-Performance Cement Paste: An Evaluation of Basic Mechanisms. Cem. Concr. Res.
**2003**, 33, 223–232. [Google Scholar] [CrossRef] - Dueramae, S.; Tangchirapat, W.; Chindaprasirt, P.; Jaturapitakkul, C.; Sukontasukkul, P. Autogenous and Drying Shrinkages of Mortars and Pore Structure of Pastes Made with Activated Binder of Calcium Carbide Residue and Fly Ash. Constr. Build. Mater.
**2020**, 230, 116962. [Google Scholar] [CrossRef] - Costa, H.; Júlio, E.; Lourenço, J. New Approach for Shrinkage Prediction of High-Strength Lightweight Aggregate Concrete. Constr. Build. Mater.
**2012**, 35, 84–91. [Google Scholar] [CrossRef] - Neville, A.M.; Brooks, J. Concrete Technology, 2nd ed.; Pearson: London, UK, 2010. [Google Scholar]
- Mehta, P. High-Performance, High-Volume Fly Ash Concrete for Sustainable Development. In International Workshop on Sustainable Development and Concrete Technology; Iowa State University: Beijing, China, 2004; pp. 3–14. [Google Scholar]
- Coutinho, J.S. Eco-Efficient Concrete with Waste. In JMC’2011-1st Journeys on Building Materials; FEUP: Porto, Portugal, 2011; pp. 171–214. (In Portuguese) [Google Scholar]
- Mehta, P. Sustainable Cements and Concrete for the Climate Change Era—A Review. In Proceedings of the Second International Conference on Sustainable Constrution Materials and Tecnologies, Università Politecnica delle Marche, Ancona, Italy, 28–30 June 2010. [Google Scholar]
- Mehta, P.; Monteiro, P. Concrete in the Era of Global Warming and Sustainability. In Concrete: Microstructure, Properties, and Materials, 4th ed.; McGraw-Hill Education: New York, NY, USA, 2014. [Google Scholar]
- Bentz, D.P.; Hansen, A.S.; Guynn, J.M. Optimization of Cement and Fly Ash Particle Sizes to Produce Sustainable Concretes. Cem. Concr. Compos.
**2011**, 33, 824–831. [Google Scholar] [CrossRef] - Bogas, J.A.; Real, S. A Review on the Carbonation and Chloride Penetration Resistance of Structural Lightweight Aggregate Concrete. Materials
**2019**, 12, 3456. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Chen, J.J.; Ng, P.L.; Chu, S.H.; Guan, G.X.; Kwan, A.K.H. Ternary Blending with Metakaolin and Silica Fume to Improve Packing Density and Performance of Binder Paste. Constr. Build. Mater.
**2020**, 252, 119031. [Google Scholar] [CrossRef] - Shafiq, N.; Kumar, R.; Zahid, M.; Tufail, R.F. Effects of Modified Metakaolin Using Nano-Silica on the Mechanical Properties and Durability of Concrete. Materials
**2019**, 12, 2291. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Özdiş, B.E.; Çam, N.F.; Canbaz Öztürk, B. Assessment of Natural Radioactivity in Cements Used as Building Materials in Turkey. J. Radioanal. Nucl. Chem.
**2017**, 311, 307–316. [Google Scholar] [CrossRef] - Mehta, P.; Monteiro, P. Concrete: Microstructure Properties and Materials, 4th ed.; McGraw-Hill Education: New York, NY, USA, 2014. [Google Scholar]
- Proske, T.; Hainer, S.; Rezvani, M.; Graubner, C. Eco-Friendly Concretes with Reduced Water and Cement Content – Mix Design Principles and Application in Practice. Constr. Build. Mater. J.
**2014**, 67, 307–430. [Google Scholar] [CrossRef] - Teixeira, E.; Branco, F.; Camões, A. Eco-Efficient Concrete Study through the Use of Biomass Fly Ash. In Proceedings of the 3rd Luso-Brazilian Congress on Sustainable Construction Materials, Coimbra, Portugal, 14–16 February 2018. (In Portuguese). [Google Scholar]
- Nasvik, J. Sustainable Concrete Structures—How to Use Concrete for Sustainable Purposes. Concr. Constr.
**2013**, 2, 765–778. [Google Scholar] - Costa, H.; Alves, H.; Freitas, E.; Júlio, E. Mechanical Performance of Concrete with Low Cement Dosage. In Proceedings of the National Meeting of Structural Concrete–BE2016, Coimbra, Portugal, 2–4 November 2016. (In Portuguese). [Google Scholar]
- Fennis, S.; Walraven, J.; Uijl, J. Compaction-Interaction Packing Model: Regarding the Effect of Fillers in Concrete Mixture Design. Mat. Struct.
**2013**, 46, 463–478. [Google Scholar] [CrossRef] - Król, A.; Giergiczny, Z.; Kuterasińska-Warwas, J. Properties of Concrete Made with Low-Emission Cements CEM II/C-M and CEM VI. Materials
**2020**, 13, 2257. [Google Scholar] [CrossRef] - De Weerdt, K.; Haha, M.; Le Saout, G.; Kjellsen, K.; Justnes, H.; Lothenbach, B. Hydration Mechanisms of Ternary Portland Cements Containing Limestone Powder and Fly Ash. Cem. Concr. Res.
**2011**, 41, 279–291. [Google Scholar] [CrossRef] - Bentz, D.P.; Sato, T.; de la Varga, I.; Weiss, W.J. Fine Limestone Additions to Regulate Setting in High Volume Fly Ash Mixtures. Cem. Concr. Compos.
**2012**, 34, 11–17. [Google Scholar] [CrossRef] - Kakali, G.; Tsivilis, S.; Aggeli, E.; Bati, M. Hydration Products of C3A, C3S and Portland Cement in the Presence of CaCO3. Cem. Concr. Res.
**2000**, 30, 1073–1077. [Google Scholar] [CrossRef] - Menéndez, G.; Bonavetti, V.; Irassar, E. Strength Development of Ternary Blended Cement with Limestone Filler and Blast-Furnace Slag. Cem. Concr. Compos.
**2003**, 25, 61–67. [Google Scholar] [CrossRef] - EN 206-1. Concrete–Part 1: Specification, Performance, Production and Conformity; CEN: Brussels, Belgium, 2007. [Google Scholar]
- Björnström, J.; Chandra, S. Effect of Superplasticizers on the Rheological Properties of Cements. Mat. Struct.
**2003**, 36, 685–692. [Google Scholar] [CrossRef] - Saha, A. Effect of Class F Fly Ash on the Durability Properties of Concrete. Sust. Environ. Res.
**2018**, 28, 25–31. [Google Scholar] [CrossRef] - Chi, J.M.; Huang, R.; Yang, C.C. Effects of Carbonation on Mechanical Properties and Durability of Concrete Using Accelerated Testing Method. J. Mar. Sci.Technol.
**2002**, 10, 14–20. [Google Scholar] - Binici, H.; Shah, T.; Aksogan, O.; Kaplan, H. Durability of Concrete Made with Granite and Marble as Recycle Aggregates. J. Mater. Process. Technol.
**2008**, 208, 299–308. [Google Scholar] [CrossRef] - Hussain, S.; Bhunia, D.; Singh, S. Comparative Study of Accelerated Carbonation of Plain Cement and Fly-Ash Concrete. J. Build. Eng.
**2017**, 10, 26–31. [Google Scholar] [CrossRef] - Proske, T.; Hainer, S.; Rezvani, M.; Graubner, C. Eco-Friendly Concretes with Reduced Water and Cement Content: Mix Design Principles and Experimental Tests. Constr. Build. Mater. J.
**2016**, 67, 63–87. [Google Scholar] [CrossRef] - De Schutter, G. Evaluation of Water Absorption of Concrete as a Measure for Resistance against Carbonation and Chloride Migration. Mater. Struct.
**2004**, 37, 591–596. [Google Scholar] [CrossRef] - Faury, J. Le Bêton, 3rd ed.; Dunod: Paris, France, 1958. [Google Scholar]
- Freitas, E.; Costa, H.; Louro, A.S.; Pipa, M.; Júlio, E. Adherence between Steel Bars and Concrete with Low Binder Dosage. In Proceedings of the National Meeting of Structural Concrete–BE2016, Coimbra, Portugal, 2–4 November 2016; pp. 1–13. [Google Scholar]
- Lourenço, J.; Júlio, E.; Maranha, P. Expanded Clay Lightweight Aggregate Concrete; APEB: Lisbon, Portugal, 2004. (in Portuguese) [Google Scholar]
- Fennis, S.; Walraven, J. Using Particle Packing Technology for Sustainable Concrete Mixture Design. Heron
**2012**, 57, 73–101. [Google Scholar] - Funk, J.; Dinger, D. Derivation of the Dinger-Funk Particle Size Distribution Equation. In Predictive Process Control of Crowded Particulate Suspensions: Applied to Ceramic Manufacturing; Springer US: Boston, MA, USA, 1994; pp. 75–83. [Google Scholar] [CrossRef]
- EN 12350-2. Testing Fresh Concrete–Part 2: Slump-Test; British Standard Institution: London, UK, 2009. [Google Scholar]
- EN 12350-4. Testing Fresh Concrete Part 4: Degree of Compactability; British Standard Institution: London, UK, 2009. [Google Scholar]
- EN 12390-3. Testing Hardened Concrete Part 3: Compressive Strength of Test Specimens; British Standard Institution: London, UK, 2009. [Google Scholar]
- EN 12390-6. Testing Hardened Concrete–Part 6: Tensile Splitting Strength of Test Specimens; British Standard Institution: London, UK, 2009. [Google Scholar]
- EN 12390-5. Testing Hardened Concrete Part 5: Flexural Strength of Test Specimens; British Standard Institution: London, UK, 2009. [Google Scholar]
- E 397. Hardened Concrete–Determination of the Modulos of Elasticity of Concrete in Compression; National Laboratory of Civil Engineering (LNEC): Lisboa, Portugal, 1993. (In Portuguese) [Google Scholar]
- E 399. Concrete. Chraracterization of Creep in Compressive Test; National Laboratory of Civil Engineering (LNEC): Lisboa, Portugal, 1993. (In Portuguese) [Google Scholar]
- E 398. Hardened Concrete. Determination of the Shrinkage and of the Swelling; National Laboratory of Civil Engineering (LNEC): Lisboa, Portugal, 1993. (In Portuguese) [Google Scholar]
- E 393. Concrete. Determination of the Absorption of Water through Capillarity; National Laboratory of Civil Engineering (LNEC): Lisboa, Portugal, 1993. (In Portuguese) [Google Scholar]
- E 394. Concrete. Determination of the Absorption of Water by Immersion; National Laboratory of Civil Engineering (LNEC): Lisboa, Portugal, 1993. (In Portuguese) [Google Scholar]
- E391. Concrete. Determination of Carbonation Resistance; National Laboratory of Civil Engineering (LNEC): Lisboa, Portugal, 1993. (In Portuguese) [Google Scholar]
- Li, L.G.; Feng, J.J.; Zhu, J.; Chu, S.H.; Kwan, A.K.H. Pervious Concrete: Effects of Porosity on Permeability and Strength. Mag. Concr. Res.
**2019**, 1–35. [Google Scholar] [CrossRef] - Sakai, Y. Relationship between Water Permeability and Pore Structure of Cementitious Materials. Mag. Concr. Res.
**2019**, 1–31. [Google Scholar] [CrossRef] - Niu, Q.; Feng, N.; Yang, J.; Zheng, X. Effect of Superfine Slag Powder on Cement Properties. Cem. Concr. Res.
**2002**, 32, 615–621. [Google Scholar] [CrossRef] - Chen, Z.X.; Chu, S.H.; Lee, Y.S.; Lee, H.S. Coupling Effect of γ-Dicalcium Silicate and Slag on Carbonation Resistance of Low Carbon Materials. J. Clean. Prod.
**2020**, 262, 121385. [Google Scholar] [CrossRef] - Camões, A. Eco-Efficient Concrete with Low Cement Content. In Metacaulino in Portugal: Production, Application and Sustainability; C-TAC, University of Minho: Aveiro, Portugal, 2011. [Google Scholar]
- Woyciechowski, P.; Woliński, P.; Adamczewski, G. Prediction of Carbonation Progress in Concrete Containing Calcareous Fly Ash Co-Binder. Materials
**2019**, 12, 2665. [Google Scholar] [CrossRef] [Green Version] - E465. Concrete. Methodology for Estimating the Concrete Performance Properties Allowing to Comply with the Design Working Life ofthe Reinforced or Prestressed Concrete Structures under the Environmental Exposures XC and XS; National Laboratory of Civil Engineering (LNEC): Lisboa, Portugal, 2007. (In Portuguese) [Google Scholar]
- Freitas, E.; Louro, A.S.; Costa, H.; Cavaco, E.S.; Júlio, E.; Pipa, M. Bond Behaviour between Steel/Stainless-Steel Reinforcing Bars and Low Binder Concrete (LBC). Eng. Struct.
**2020**, 221, 111072. [Google Scholar] [CrossRef] - Chu, S.H.; Jiang, Y.; Kwan, A.K.H. Effect of rigid fibres on aggregate packing. Constr. Build. Mater.
**2019**, 224, 326–335. [Google Scholar] [CrossRef] - Chu, S.H.; Li, L.G.; Kwan, A.K.H. Fibre factors governing the fresh and hardened properties of steel FRC. Constr. Build. Mater.
**2018**, 186, 1228–1238. [Google Scholar] [CrossRef]

**Figure 2.**Durability tests: (

**a**) water absorption through capillarity; (

**b**) water absorption by immersion; (

**c**) accelerated carbonation test.

**Figure 4.**Comparison of the evolution of shrinkage by Eurocode 2 (EC2): (

**a**) prediction curve with EC2 equations; (

**b**) adaptation of the experimental evolution to prediction curve using the β

_{shape}coefficient.

**Figure 5.**Influence of compactness on ratio of shrinkage Exp/EC2: (

**a**) ratio for each concrete; (

**b**) correlation between the ratio and compactness

^{−6}.

**Figure 6.**Evolution with age of creep coefficient: (

**a**) all concretes; (

**b**) concretes LC with different granulometric curves (LC-Funk and Dinger; LC_F-Faury).

**Figure 7.**Predicted evolution with age of creep coefficient (EC2): (

**a**) curves with αt = 0.30; (

**b**) curves with αt = 0.15.

**Figure 13.**Relation between W/C

_{eq}(

**a**) and compactness depending on water absorption by immersion (

**b**).

**Figure 17.**Concrete specimens C75 and LC175 with phenolphthalein after 3, 7 and 42 days of exposure to CO

_{2}.

**Figure 21.**Relationship between carbonation depth after 42 days of exposure to CO

_{2}and mechanical strength at 28 days.

**Figure 23.**Relation between the c

_{min,dur}vs. dosage of C

_{eq}and between c

_{min,dur}vs. W/C

_{eq}.:(

**a**) current structures, total powder 250 kg/m

^{3}; (

**b**) current structures, total powder 350 kg/m

^{3}; (

**c**) special structures, total powder 250 kg/m

^{3}; (

**d**) special structures, total powder 350 kg/m

^{3}; (

**e**) current structures; (

**f**) special structures.

Constituents | LC75 | LC75F | C75 | LC125 | LC125F | C125 | LC175 | LC175F | C175B | C200B | LC250A | C250 |
---|---|---|---|---|---|---|---|---|---|---|---|---|

C (kg/m^{3}) | 75 | 75 | 75 | 125 | 125 | 125 | 175 | 175 | 175 | 200 | 250 | 250 |

Lf (kg/m^{3}) | 75 | 75 | 75 | 125 | 125 | 125 | 75 | 75 | 100 | 150 | - | 100 |

FA (kg/m^{3}) | 100 | 100 | 200 | - | - | 100 | - | - | 75 | - | - | - |

SKY (kg/m^{3}) | 2.3 | 2.3 | 0.7 | 2.5 | 2.5 | 0.8 | 2.6 | 2.6 | 2.1 | 1.0 | 0.8 | 1.0 |

W (kg/m^{3}) | 118 | 118 | 169 | 118 | 118 | 169 | 118 | 118 | 128 | 144 | 179 | 169 |

S0/3 (kg/m^{3}) | 44 | 587 | 286 | 44 | 671 | 371 | 44 | 747 | 181 | 186 | 218 | 492 |

S0/4 (kg/m^{3}) | 1068 | 308 | 585 | 1080 | 244 | 520 | 1084 | 210 | 762 | 742 | 817 | 427 |

G4/8 (kg/m^{3}) | 284 | 78 | 106 | 287 | 82 | 110 | 288 | 98 | 92 | 96 | 278 | 116 |

C6/14 (kg/m^{3}) | 623 | 1050 | 798 | 631 | 1049 | 797 | 633 | 997 | 894 | 869 | 587 | 795 |

Total aggregates (kg/m^{3}) | 2018 | 2023 | 1774 | 2042 | 2047 | 1798 | 2048 | 2053 | 1929 | 1893 | 1900 | 1831 |

W/C | 1.57 | 1.57 | 2.26 | 0.94 | 0.94 | 1.35 | 0.67 | 0.67 | 0.73 | 0.72 | 0.72 | 0.68 |

Equiv.-cement, C_{eq} (kg/m^{3}) | 85 | 85 | 85 | 125 | 125 | 142 | 175 | 175 | 198 | 200 | 250 | 250 |

W/C_{eq} | 1.39 | 1.39 | 1.99 | 0.94 | 0.94 | 1.19 | 0.67 | 0.67 | 0.65 | 0.72 | 0.72 | 0.68 |

W/B | 0.47 | 0.47 | 0.48 | 0.47 | 0.47 | 0.48 | 0.47 | 0.47 | 0.37 | 0.41 | 0.72 | 0.48 |

Compactness | 0.86 | 0.86 | 0.81 | 0.86 | 0.86 | 0.81 | 0.86 | 0.86 | 0.86 | 0.84 | 0.80 | 0.81 |

LCC Mixtures | f_{cm,7} (MPa) | f_{cm,28} (MPa) | f_{cm,56} (MPa) | E_{cm} (GPa) | f_{ctm,f} (MPa) | f_{ctm,sp} (MPa) | Slump (mm) | D_Comp |
---|---|---|---|---|---|---|---|---|

LC75 | 11.6 | 20.6 | 26.5 | 37.4 | 3.2 | 1.5 | - | 1.21 |

LC75F | 15.7 | 22.1 | - | 28.7 | - | - | 50 | - |

C75 | 7.6 | 15.2 | 20.5 | - | 2.1 | 0.7 | 90 | - |

LC125 | 25.2 | 28.9 | 33.9 | 40.6 | 4.5 | 2.3 | - | 1.23 |

LC125F | 26.4 | 29.4 | - | 34.5 | - | - | 45 | - |

C125 | 14.3 | 20.3 | 26.5 | - | 3.6 | 1.5 | 120 | - |

LC175 | 35.0 | 44.7 | 50.2 | 42.4 | 6.9 | 3.4 | - | 1.25 |

LC175F | 36.8 | 45.9 | - | 38.2 | - | - | 65 | - |

C175B | 36.2 | 50.1 | 52.9 | 47.9 | 5.7 | 3.2 | 107 | - |

C200B | 32.9 | 38.2 | 39.1 | 41.3 | 5.8 | 3.0 | 110 | - |

LC250A | 25.8 | 30.5 | 34.3 | 38.1 | 5.1 | 2.2 | - | 1.16 |

C250 | 34.9 | 39.1 | 41.5 | 36.5 | 5.4 | 2.9 | 80 | - |

C_{d} (mm) | |||||
---|---|---|---|---|---|

LCC Mixtures | Days | ||||

3 | 7 | 14 | 28 | 42 | |

LC75 | 10.0 | 15.0 | 23.3 | 36.5 | 43.3 |

C75 | 17.5 | 22.5 | 39.0 | 49.9 | - |

LC125 | 5.5 | 11.0 | 15.3 | 21.8 | 26.4 |

C125 | 10.0 | 15.5 | 20.0 | 27.8 | 33.5 |

LC175 | 2.0 | 3.5 | 5.8 | 9.0 | 10.0 |

C175B | - | 4.8 | - | 10.3 | 12.9 |

C200B | - | 5.3 | - | 12.3 | 14.7 |

LC250A | 4.5 | 6.5 | 10.3 | 15.8 | 18.1 |

C250 | 3.5 | 5.0 | 8.3 | 10.0 | 11.0 |

R_{C65} (kg·year/m^{5}) | ||||||
---|---|---|---|---|---|---|

LCC Mixtures | - | - | Days | - | - | Average |

3 | 7 | 14 | 28 | 42 | ||

LC75 | 15 | 15 | 13 | 10 | 11 | 13 |

C75 | 5 | 7 | 5 | 6 | - | 5 |

LC125 | 49 | 29 | 30 | 29 | 30 | 33 |

C125 | 15 | 14 | 17 | 18 | 18 | 17 |

LC175 | 370 | 282 | 209 | 170 | 207 | 248 |

C175B | - | 153 | - | 129 | 125 | 125 |

LC250A | 73 | 82 | 66 | 56 | 63 | 68 |

C200B | - | 123 | - | 91 | 15 | 80 |

C250 | 121 | 138 | 101 | 138 | 171 | 134 |

Intended Service Lifetime | Propagation Time and Period of Initiation | XC2 (Wet, Rarely Dry) | XC3 (Moderate Humidity) | XC4 (Dry Regime) | XC4 (Wet Regime) |
---|---|---|---|---|---|

t_{g} = 50 years(RC2) | t_{p} (years) | 10 | 45 | 15 | 5 |

t_{ic} (years) | 92 | 12 | 80 | 105 | |

t_{g} = 100 years(RC3) | t_{p} (years) | 20 | 90 | 20 | 10 |

t_{ic} (years) | 224 | 28 | 224 | 252 |

Minimum Cover c_{min,dur} (mm) | ||||||||
---|---|---|---|---|---|---|---|---|

Structural Class | Current Structures (Class S4) | Special Structures (Class S5) | ||||||

Exposure Classes | XC2 | XC3 | XC4 (Dry Reg.) | XC4(Wet Reg.) | XC2 | XC3 | XC4 (Dry Reg.) | XC4 (Wet Reg.) |

EC2 | 25 | 25 | 30 | 30 | 30 | 35 | ||

LC75 | 34 | 51 | 69 | 77 | 45 | 78 | 106 | 111 |

C75 | 50 | 75 | 102 | 114 | 67 | 115 | 156 | 163 |

LC125 | 21 | 32 | 43 | 48 | 29 | 49 | 66 | 70 |

C125 | 30 | 45 | 61 | 67 | 40 | 68 | 93 | 97 |

LC175 | 8 | 12 | 16 | 18 | 10 | 18 | 24 | 25 |

C175B | 11 | 16 | 22 | 25 | 15 | 25 | 34 | 36 |

LC250A | 15 | 22 | 30 | 34 | 20 | 34 | 46 | 49 |

C200B | 13 | 19 | 25 | 28 | 17 | 29 | 39 | 41 |

C250 | 11 | 16 | 22 | 24 | 14 | 24 | 33 | 35 |

**Table 7.**Minimum dosage of cement according to standards and equivalent dosages used in the concretes studied.

Structural Class | Current and Special Structures (Classes S4 and S5) | ||||
---|---|---|---|---|---|

Type of Cement | CEM I; CEM II/A (1) | ||||

Exposure Class | XC2 | XC3 | XC4 (Wet and Dry Reg.) | ||

EN 206 | Minimum dosage of C (kg/m^{3}) | 280 | 280 | 300 | |

Maximum W/C ratio | 0.60 | 0.55 | 0.50 | ||

- | - | Total powder (kg/m^{3}) | Equivalent dosage of cement, C_{eq}(kg/m ^{3}) | W/C_{eq} | |

- | Concretes | LC75 | 250 | 85 | 1.39 |

LC125 | 125 | 0.94 | |||

LC175 | 175 | 0.67 | |||

LC250A | 250 | 0.47 | |||

C75 | 350 | 85 | 2.25 | ||

C125 | 142 | 0.97 | |||

C175B | 198 | 0.73 | |||

C200B | 200 | 0.72 | |||

C250 | 250 | 0.68 |

**Table 8.**Service lifetime (years) for current and special structures produced with the studied concrete under environmental conditions XC.

Structural Class | Current Structures (Class S4, RC2, 50 Years) | Special Structures (Class S5, RC3, 100 Years) | |||||||
---|---|---|---|---|---|---|---|---|---|

Exposure Class | XC2 | XC3 | XC4 (Dry Reg.) | XC4 (Wet Reg.) | XC2 | XC3 | XC4 (Dry Reg.) | XC4 (Wet Reg.) | |

Concretes | c_{min,dur} (mm) | 25 | 30 | 30 | 35 | ||||

LC75 | t_{g} (years) | 25 | 46 | 19 | 9 | 42 | 91 | 25 | 15 |

C75 | 15 | 46 | 17 | 7 | 27 | 91 | 22 | 12 | |

LC125 | 75 | 48 | 29 | 19 | 114 | 94 | 37 | 27 | |

C125 | 33 | 47 | 21 | 11 | 53 | 92 | 27 | 17 | |

LC175 | >>>> 200 | 69 | 179 | 169 | >> 200 | 119 | 216 | 206 | |

C175B | >> 200 | 57 | 86 | 76 | >> 200 | 104 | 105 | 95 | |

LC250A | >> 200 | 51 | 49 | 39 | >> 200 | 98 | 60 | 50 | |

C200B | >> 200 | 54 | 67 | 57 | >> 200 | 101 | 82 | 72 | |

C250 | >> 200 | 58 | 92 | 82 | >> 200 | 105 | 113 | 103 |

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Robalo, K.; Soldado, E.; Costa, H.; Carvalho, L.; do Carmo, R.; Júlio, E.
Durability and Time-Dependent Properties of Low-Cement Concrete. *Materials* **2020**, *13*, 3583.
https://doi.org/10.3390/ma13163583

**AMA Style**

Robalo K, Soldado E, Costa H, Carvalho L, do Carmo R, Júlio E.
Durability and Time-Dependent Properties of Low-Cement Concrete. *Materials*. 2020; 13(16):3583.
https://doi.org/10.3390/ma13163583

**Chicago/Turabian Style**

Robalo, Keila, Eliana Soldado, Hugo Costa, Luís Carvalho, Ricardo do Carmo, and Eduardo Júlio.
2020. "Durability and Time-Dependent Properties of Low-Cement Concrete" *Materials* 13, no. 16: 3583.
https://doi.org/10.3390/ma13163583