Next Article in Journal
Hybrid Machine Learning Model for Predicting the Fatigue Life of Plain Concrete Under Cyclic Compression
Next Article in Special Issue
3D Concrete Printing Review: Equipment, Materials, Mix Design, and Properties
Previous Article in Journal
The Effect of Industrial and Recycled Steel Fibers on the Behavior of Rubberized RC Columns Under Axial Loading
Previous Article in Special Issue
The Potential of Wood Ash to Be Used as a Supplementary Cementitious Material in Cement Mortars
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Buildings
Volume 15
Issue 10
10.3390/buildings15101617
buildings-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Effect of Pozzolanic Additive on Properties and Surface Finish Assessment of Concrete

by
Giedrius Girskas
*,
Dalius Kriptavičius
,
Olga Kizinievič
and
Jurgita Malaiškienė
Faculty of Civil Engineering, Vilnius Gediminas Technical University, Sauletekio av. 11, LT-10223 Vilnius, Lithuania
*
Author to whom correspondence should be addressed.
Buildings 2025, 15(10), 1617; https://doi.org/10.3390/buildings15101617
Submission received: 18 April 2025 / Revised: 5 May 2025 / Accepted: 9 May 2025 / Published: 11 May 2025
(This article belongs to the Special Issue Sustainable Concrete: Research on Waste Utilization and Performance Optimization)
Browse Figures
Versions Notes

Abstract

This research focuses on the impact of a pozzolanic additive (zeolite) on the durability properties of concrete and the evaluation of the surface finish of the final product (concrete). Durability is one of the key characteristics of concrete that ensures the performance of concrete structures, landscaping elements, and products over their lifetime and beyond. To reduce CO2 emissions, replacing part of traditional cement with pozzolanic additives is necessary. We tested concrete mixes in which up to 20% of cement was replaced with a pozzolanic additive. Concrete flow and entrained air content were measured. The following properties of hardened modified concrete were determined: density, ultrasonic pulse velocity, water absorption, freeze–thaw resistance, and mechanical properties after 7 and 28 days of curing. The compressive strength values were normalised and expressed in MPa/g to obtain a deeper insight into the effect of a pozzolanic additive on the mechanical properties of concrete. The test results showed that the pozzolanic additive selected for testing reduced the flowability, density, and ultrasonic pulse velocity; increased entrained air content; and reduced the porosity of concrete. The compressive strength results at 28 days (normalised and expressed in MPa/g) showed that all specimens modified with up to 20% zeolite had a higher compressive strength than that of the reference specimen (from 0.0138 to 0.0164). Freeze–thaw resistance results showed that 15% was the optimum content of zeolite additive that could replace cement in the mix to obtain concrete with appropriate durability properties. Concrete surface finish evaluation tests showed that 15% of the pozzolanic additive is recommended to obtain a good-quality surface finish of exposed concrete.

1. Introduction

With growing concern about environmental issues, research into mitigating the deleterious effects of the concrete industry on the environment has increased. Global PC manufacturing is responsible for about 8% of the world’s greenhouse gas emissions [1]. One of the ways to address this problem is to replace part of the binder with industrial waste or products of natural origin [2,3,4,5,6]. Research papers on the impact of supplementary cementitious materials are mainly focused on the technical characteristics of concrete, such as durability, mechanical properties, etc. In this respect, active mineral additives based on amorphous SiO2, vitreous silicates and aluminosilicates, or their mixtures have a positive impact on the overall properties of hardened concrete [7,8,9,10,11,12].
Natural and artificial pozzolanic materials are active mineral additives containing at least 50% silica and aluminium oxides. Pozzolanic activity is the ability to react with portlandite (Ca(OH)2) in the presence of free water. This reaction produces calcium silicate and calcium aluminosilicate hydrates or compounds similar to those formed in PC hydration [13,14,15]. The benefits of replacing part of PC with pozzolanic materials include improved PC concrete properties, lower production or maintenance costs, and reduced CO2 emissions [16]. There are numerous advantages of modifying concrete with pozzolanic materials, such as enhanced durability of concrete [17], lower heat of hydration [18], improved sulphate resistance [19], and also lower PC industry energy costs [18].
Zeolites (ZLs), both natural and synthetic, are recognised and applied as pozzolanic materials in the cement and concrete industry. They are silicates with an open framework structure or hydrated aluminosilicate minerals. They have exceptional physical properties due to their almost ideal crystalline structure. The pozzolanic activity of ZLs is just as good as that of mineral additives having an amorphous structure [20]. Zeolites mainly consist of silicon, aluminium, and oxygen [21,22] and differ by their framework type, Si/Al ratio, sorption capacity, ion exchange potential, and types of exchangeable cations [23,24]. ZL additives reduce segregation and bleeding and thus help to maintain the homogeneity of the mixture [25,26]. However, researchers observed a higher demand for a superplasticiser in mixtures modified with 10% ZL to maintain slump properties [27]. Fragoulis et al. found that ZL increases water demand; therefore, a higher dose of superplasticiser is required to adjust the rheological properties of the mixture [28]. Uzal and Turanli argued that the absorptivity of ZL adversely affects the consistency of the mix and accelerates the initial and final setting times [29]. Valipour et al. noted that water demand increases with a higher content of ZL replacing PC in the mix [30].
Pozzolanic materials react with CH to produce an additional amount of C-S-H. This process influences the microstructure of the PC matrix [31] because most often, it causes the densification of the PC matrix [32] and reduces the total porosity and the distribution of capillary pores [33]. However, the influence of PC matrix porosity on concrete permeability does not depend merely on the pore size and volume [34]. Neithalath and Jain found that water absorption highly depends on the pore interconnectivity [35]. Sant et al. stated that the interconnectivity of capillary pores is as important an indicator as capillary porosity [36]. Yu et al. found that the interconnectivity of capillary pores was the main factor impacting the water permeability of PC pastes [37]. The authors of another study reported the ability of pozzolanic materials to change the pore structure and morphology [38] because a certain portion of the interconnected pores can be blocked as a result of pozzolanic reactions [39].
Pavlik et al. found that ZL-modified concrete specimens had a higher open porosity than reference specimens [40]. De La Cruz et al. claimed that at 28 days, specimens modified with 5% ZL had 10.4% higher compressive strength and 4.7% lower total porosity [41]. Bilim found that all test specimens in which up to 20% PC was replaced with ZL had lower porosity and water absorption compared to reference specimens [42].
Researchers reported that test specimens modified with 8% ZL showed better strength results than reference specimens, and specimens modified with 16% ZL had compressive strength equal to that of reference specimens [23]. A group of authors who analysed ZL’s impact on the durability of PC concretes found that concrete modified with 20% ZL had better resistance to freezing and thawing and the effect of de-icing salts, as well as carbonation [31].
In monolithic systems, the quality of cast-in-place elements’ (walls, columns, slabs, etc.) surface finish can be compromised by several factors, such as poor surface quality of the formwork, dirty formwork, inaccurate concrete mix design, failure to follow concrete placement procedures, insufficient compaction of cast concrete, and incompetence of the workforce. These causes, or combinations of them, can affect the quality of concrete surface finish and cause the following defects to occur: surface voids (bug holes), irregular concrete surface colour, uneven concrete surface/poor compaction, etc. [43,44,45].
Although there are a lot of research articles on introducing pozzolanic additives to cementitious systems, little information on the evaluation of modified concrete surface finishes is available. This research work had two aims. The first was to test the effect of a pozzolanic additive on the physical and mechanical properties of concrete and find ways to extend the durability of concrete without impairing its resistance to mechanical load and stress. The second was to evaluate the porosity of the concrete surface using image processing programmes and determine the optimal amount of pozzolanic additives to obtain a high-quality surface finish on exposed concrete. Conclusions are provided based on the examination of these aspects.

2. Materials and Methods

2.1. Materials

The specimens were made using CEM I 42.5 R Portland cement (PC) according to EN 197-1:2011 [46]. A portion of the PC was replaced with an natural pozzolanic additive (NPA). NPA characteristics are provided along with ordinary PC properties in Table 1 and Table 2. NPA was obtained from a Transcarpathian mine in the west of Ukraine.
Table 1 presents the chemical compositions of PC and NPA. As evident from the data, PC consists primarily of calcium and silicon oxides, which make up more than 80% of the total, while NPA is rich in silicon and aluminium oxides, accounting for 85%.
Table 2 presents the main physical properties of the binding materials. We can see that PC has higher specific density than NPA, but NPA particles are slightly larger, and their specific surface area is much larger than that of PC particles.
Figure 1 illustrates the particle size distributions of PC and NPA. The average particle size values are given in Table 2. As shown in the table, the average PC particle size is 17.6 µm, whereas NPA particles are slightly larger, with an average size of 29.0 µm.
NPA SEM images are presented in Figure 2a at ×3000 magnification and in Figure 2b at ×10,000 magnification. As shown in the images, NPA particles have a plate shape and a size of 10 µm. Agglomerations of smaller particles are also visible.
X-ray diffraction analysis (XRD) of the NPA (Figure 3) reveals that this material is composed of three main minerals: clinoptilolite, heulandite, and cristobalite.
Aggregates were used to prepare the PC mix for test specimens at a 0/4 fraction of sand and 4/16 fraction of gravel. A 0/4 fraction of sand complies with LST EN 12620:2003+A1:2008 requirements for concrete aggregates [47]. The values of essential aggregate characteristics are presented in the following tables: sand characteristics in Table 3 and gravel characteristics in Table 4.
Concrete mixtures were prepared using tap water according to LST EN 1008 [48]. The water had a pH of 7.6 and temperature of 20 ± 3 °C. Polycarboxylate polymer-based superplasticiser (28% active substance) was added to the water. The superplasticiser is a brown liquid with the density of 1060 kg/m3, pH value of 4.4, chloride content < 0.10% wt., and alkali content < 0.40% wt.

2.2. Preparation and Moulding of Concrete Specimens and Compositions

Dry raw materials were mixed in a forced action mixer according to LST EN 196-1:2016 [49]. The total mixing time did not exceed 7 min. Then, 100 × 100 × 100 mm cubes were cast in waterproof moulds made of 18 mm-thick birch plywood coated with phenolic formaldehyde (220 g/m2). The concrete mix was placed into the moulds in two layers, and each layer was compacted on a vibrating table. The moulds with concrete were covered with a waterproof film and kept at an ambient temperature of 20 ± 2 °C for 24 h. After 24 h, the specimens were de-moulded and cured in water at the same temperature.
Table 5 presents the five compositions of the moulded concrete specimens. The reference composition PA0 was not modified with NPA. Compositions PA5, PA10, PA15, and PA20 were modified with NPA added by weight of PC at 5% increments. The maximum NPA content was 20%. A plasticising admixture was added at 0.8%. The control composition consistency corresponded to slump class S3.

2.3. Test Methods

The specific surface area of NPA was measured using the air permeability method (Blaine method) according to LST EN 196-6:2010 [50]. Particle size distribution was determined using a Cilas 1090 LD particle size analyser (U.S. Philadelphia, Horsham). Water was used as the dispersion phase, the solid content of the suspension ranged between 12% and 14%, the ultrasonic particle dispersion lasted 100 s, and particle size was measured in the range of 0.01 to 500 μm in 15 s intervals. The qualitative analysis of mineral material phase composition was performed with an X-ray diffractometer. A graphite monochromator was employed to obtain the X-ray Cu Kα spectrum (λ = 0.154184 nm). The test parameters were set as follows: anode voltage at 30 kV, anode current at 12 mA, diffraction angle (2θ) ranging from 5° to 60°, detector step size of 0.02°, and an intensity measurement time of 0.5 s per step. PDXL software (Rigaku Corporation, Japan, Tokyo) and the PDF-4+ database of crystal structures was used for XRD analysis. Pictures of concrete specimens were processed and analysed using the image processing programmes ACDSee and ImageJ according to the methodology presented in Figure 4.
Entrained air content in concrete was determined according to LST EN 12350-2009 requirements [51]. The consistency of concrete was determined according to LST EN 12350-2009 requirements [52]. The compressive strength was tested according to LST EN 12390-3:2019—compressive strength of test specimens [53]. The specimens were loaded to failure in a compression-testing machine (hydraulic press) complying with LST EN 12390-4:2019—compressive strength technical requirement for testing machines [54]. A hydraulic press loading rate of 0.6 MPa/s was applied. The load on the specimens in the press was applied perpendicular to the casting direction. The load on the specimen was applied without shock and was increased continuously at the selected constant rate ± 10% until no greater load could be sustained. Open porosity tests were conducted according to the modified EN 1015-10:2002 method [55].
After 28 days of curing, the specimens were weighed in air and water. After recording the weight values, the specimens were dried in an oven at 100 ± 5 °C until constant mass was achieved. The water absorption rate was determined using the methodology given in EN 13369:2018 [56]. Freeze–thaw resistance was quantitatively assessed using the frost resistance coefficient. Knowing the value of frost resistance coefficient, the freeze–thaw resistance of hardened concrete can be predicted according to the function of the concrete’s freeze–thaw resistance and frost resistance coefficient [57].

3. Results and Discussion

3.1. Fresh Concrete Properties

We measured entrained air content in the concrete mixture (Figure 5). Reference specimen PA0 had an entrained air content of 3.8%. Entrained air content increased with the replacement of PC with NPA. In specimens modified with 5% NPA, the entrained air content increased slightly to 4.0%. The value of entrained air increased to 4.4% in specimens modified with 10% NPA. The highest entrained air value of 4.6% was reached in the samples containing 15% NPA. With a further increase in NPA content to 20%, the entrained air content dropped to 4.1%.
The slump test of fresh concrete is the easiest and the most often used method to determine concrete consistency. The slump value is measured in mm of the vertical subsidence of concrete after the Abrams cone is lifted. Concrete mixtures are classified by slump classes (S1–S5) which indicate the subsidence of concrete.
We aimed to produce a control composition of slump class S3. The results of the tests are presented in Figure 6. The control composition met the requirements of slump class S3 with a slump of 150 mm. When NPA was added at 5%, the slump increased to 180 mm. The specimens modified with 10% NPA had a slump of 150 mm—identical to the reference composition. The slump decreased with a higher NPA content: with 15% NPA, the slump dropped to 105 mm, and with 20% NPA, the slump decreased to 30 mm.
Xu et al. analysed the effect of NPA on mortar flowability. They reported that mortar flowability increased when 5% or 10% PC was replaced with NPA. The authors explained this effect by a higher degree of cohesiveness in the mix depending on NPA particle size and amount. With the packing density of composite structure thus improved, there is more excess water in the system, and the flowability of the mixture improves [58].

3.2. Physical and Mechanical Properties of Concrete

A pozzolan typically consists of significant amounts of SiO2 and Al2O3, which can react with calcium hydroxide (CH) in the presence of water to form cementitious compounds such as 3CaO·2SiO2·3H2O and 3CaO·Al2O3·6H2O. These compounds contribute to the development of a dense microstructure in the hardened PC paste and concrete [59].
Figure 7 illustrates the relationship between the cast concrete density and NPA content. The density of the reference composition shown in the figure is 2393 kg/m3. When the binder is replaced with 5% NPA, the density drops to 2354 kg/m3. The same downward trend is observed with an increase in NPA content.
The observed decrease in density values is natural considering that NPA has a lower specific density than PC. The dependence of UPV on the content of NPA added to concrete mixtures correlates with density values. Figure 8 illustrates the results of UPV tests. The UPV value in reference specimens is 4911 m/s. A higher NPA content causes UPV values to decrease to 4727 m/s in specimens modified with 20% NPA.
Figure 9 illustrates the dependence of compressive strength on NPA content after 7 days of curing. The reference specimen has a compressive strength of 48.4 MPa. When 5% of the binder is replaced with NPA, the compressive strength of concrete drops by 9.5%. Bigger amounts of NPA decrease the compressive strength values even more: concrete modified with 10% NPA has a compressive strength of 41.6 MPa, 38.1 MPa with 15% NPA, and 34.3 MPa with 20% NPA.
To better understand the effect of the NPA on the properties analysed, the test data were adjusted, i.e., recalculated to express the compressive strength achieved per unit weight of PC. This recalculation method helps to eliminate the effect of PC “dilution” and reveal the relative effectiveness of NPA on mechanical properties.
Figure 10 shows that the reference specimens had the highest compressive strength value after 7 days of curing. The specimens modified with 10% NPA had a slightly higher compressive strength, whereas other compositions had lower strength than the reference composition.
The test results and the findings of other authors suggest that pozzolanic reactions of NPA often occur in late stages of hydration, i.e., after 14 or more days [60,61].
In a study where 0%, 5%, and 10% of the PC was replaced with NPA, it was found that after 28 days, the NPA-modified specimens exhibited compressive strength values 10.4% and 12.6% higher, respectively, than those of the reference [41]. Another study analysed the effect of varying NPA content (0%, 10%, 15%, 20%) and curing times (1, 7, and 28 days) on compressive strength. The results showed that all NPA-modified specimens outperformed the reference specimens at all curing times, with the highest compressive strength observed in the specimens modified with 20% NPA at 28 days [62].
At 28 days, the compressive strength trends were different from those at 7 days. Figure 11 shows that reference specimens have a strength of 54.2 MPa. In specimens modified with 5% NPA, the compressive strength increases 5% to 55.7 MPa. When PC is replaced with 10% NPA, the compressive strength slightly decreases to 55.5 MPa. Higher NPA content causes a decrease in compressive strength compared to that of the reference specimen: at 15%, the strength is 52.7 MPa, and at 20%, it decreases to 51.2 MPa.
However, after the adjustment, i.e., the recalculation of strength results per unit weight of PC, the compressive strength of the specimens modified with up to 20% NPA was higher than the strength of reference specimens. These results are presented in Figure 12.
Researchers who conducted long-term tests with NPA reported that after 28, 90, and 18 days of curing, the specimens modified with NPA showed better compressive strength results [63]. Perraki et al. performed similar tests with cements of different strength classes (CEM I 42.5 N and CEM I 52.5 N) and found that the specimens where 10% PC (CEM I 42.5 N) was replaced with NPA had slightly higher compressive strength values at 28 and 90 days. The specimens with 10% and 20% PC (CEM I 52.5 N) replaced with NPA had slightly higher compressive strength values than reference specimens at 90, 180, and 360 days [64].
The researchers explain that higher compressive strength values for pozzolanic reactions of ZL produce higher amounts of C-S-H, and therefore, higher compressive strength values are achieved. These findings are supported by Nai-qian et al., who claim that ZL affects the mechanical properties of concrete due to reduced total porosity and improved interfacial area between the PC matrix and aggregates [65]. This information encouraged us to further analyse the effect of ZL on concrete porosity indicators.
Researchers claim that ZL used as an additive in concrete may decrease compressive strength due to the high mixing water demand because of the high surface area of ZL particles and its porous structure [66,67]. Moreover, the decline in initial compressive strength is explained by the water/binder ratio. In any case, if a suitable amount of NPA is chosen for concrete production, the benefits of applying it can outweigh the drawbacks.

3.3. Concrete Water Absorption

Given the wide use of cement-based materials in various buildings and structures, durability, which mainly refers to the resistance to temperature fluctuations (cyclic freeze–thaw) and various types of corrosion, is a very important characteristic of concrete. The durability of cement-based materials is influenced by different factors, among which water absorption of PC systems, porosity, and pore properties are the most important.
Figure 13 illustrates the relationship between NPA content and water absorption in concrete. The tests showed that water absorption increases with the NPA content in concrete. These findings corroborate density test results, which showed that density decreases with a higher NPA content. Concrete containing 5% NPA had 6.4% higher water absorption. Water absorption increases with a higher NPA content. Concrete modified with 20% NPA has a water absorption value of 5.66%, which is 24.94% higher than that of the reference composition.
An increase in water absorption is anticipated because natural zeolite absorbs water faster than cement [68]. With the addition of natural zeolite, the depth of water penetration in concrete specimens decreased. The results after 28 days of curing showed that the depth of water penetration decreased between 13% and 40% compared to that of the reference. The performance further improved at the age of 90 days. According to water absorption tests, the specimens modified with natural zeolite absorbed more water than the reference specimen.
Concrete specimens containing natural zeolite produced fewer pores because of the zeolite’s pozzolanic activity and Ca(OH)2 consumption. On the other hand, the water uptake of the mixtures, particularly in the top surface of the concrete, impacted the total water absorption. Jana and Feng et al. reported that this phenomenon can be explained by the considerable pozzolanic reactivity of the natural zeolites examined [69,70].
Zeolite particles, having a high absorption capacity, act as water reservoirs distributed throughout the concrete and facilitate internal curing. Capillary pores are formed at the start of the concrete mixing process, and water is absorbed onto these particles [71,72].

3.4. Porosity

Concrete porosity is an important characteristic for all types of concrete products. This characteristic determines not only how the product will look but also how long the cast product will last and whether it will lose its aesthetic appearance and mechanical properties.
Concrete porosity test results are presented in Figure 14. The total porosity of concretes of different compositions modified with up to 20% NPA added at 5% increments was analysed. Reference specimens had a total porosity of 11.04%, open porosity of 10.86%, and closed porosity of 0.18%. The air-entraining admixture was intentionally not used to see the direct effect of NPA on concrete porosity. With the replacement of PC with 5% NPA, the total porosity increased by 13.13% up to 12.49%. It should be noted that open porosity also increased to 11.35% and closed porosity increased significantly to 1.14%. Closed porosity is a very strong indicator of the durability properties of concrete products. Similar trends were observed in the specimens modified with 10–15% NPA, as open and closed porosity values increased along with total porosity. The closed porosity decreased in the specimens with a higher NPA content of 20%, although the total porosity increased. The porosity tests suggest that 15% is the optimum/maximum amount of NPA that can be added by weight of PC to produce durable concrete.
There is sufficient evidence that the durability of cementitious composites is directly related to their porosity, which determines how much water with dissolved degrading agents (chlorides, sulphates) can enter the PC matrix.
The replacement of PC with 20% ZL decreased the PC system’s porosity and water absorption. Bilim explained this effect by the pozzolanic reactions of ZL, which produce more C-S-H and C-A-S-H and thus improve the concrete microstructure [42]. Uzal and Turanli support this idea based on the experimental results of hardened PC paste modified with ZL. The modified specimen had fewer pores of the size > 50 nm and thus better mechanical and permeability properties [29]. Researchers who studied water absorption and the depth of water penetration under pressure reported an inverse relationship, i.e., the specimens modified with ZL showed higher water absorption and lower penetration depth values than reference specimens [73]. Similar results were obtained by other authors who analysed the same properties of concrete. Test results showed that at 28 and 90 days, water penetration depth decreased in the specimens where 15% and 30% PC was replaced with ZL. Researchers also found that these specimens had higher water absorption values [74].
The analysis of test results revealed that the addition of NPA can reduce the total porosity, altering pore size and distribution; therefore, the influence of this mineral on the durability properties of cementitious composites should be analysed.

3.5. Frost Resistance

Concrete’s resistance to aggressive environments depends on two things: the microstructure and mineral composition of the cementitious matrix. Microstructural elements, such as the type, number, volume, shape, and distribution of pores, determine the extent to which concrete can be penetrated by degrading agents, i.e., water, which crystallises into ice at low temperatures, increases in volume, and erodes concrete from the inside, and substances dissolved in water, which, together with water, enter the concrete microstructure and form new compounds with the minerals of the PC matrix.
Figure 15 shows that reference specimens were very weak and sustained only 22 freeze–thaw cycles. Specimens of composition PA5 sustained 144 freeze–thaw cycles. These improved results are related to higher closed porosity. Specimens of composition PA10 sustained 178 freeze–thaw cycles. The highest freeze–thaw resistance value of 260 freeze–thaw cycles was obtained in the specimens modified with 15% NPA. Resistance to freeze–thaw cycles correlated directly with concrete porosity test results—concrete with more closed pores was more durable and, therefore, could withstand more freeze–thaw cycles.
High levels of reactive SiO2 and Al2O3 in ZLs facilitate their reactions with Ca(OH)2 generated during PC hydration to form additional C-S-H gel and hydrated aluminates, which improve the microstructure of the hardened PC paste. Improved mechanical properties, decreased permeability, reduced ASR-induced expansion, and increased resistance to sulphate attack result from replacing PC with ZL in PC and concrete composites. In addition, some research studies point out that ZL effectively improves concrete’s durability [75].
Researchers who studied in detail the effect of ZL and its content on the durability of concrete focused on total porosity and pore size distribution. They reported that total porosity increased in all cases when part of PC was replaced with ZL and that the pore volume in the specimens modified with 10% and 20% ZL increased mainly due to the fine pores with diameters ranging from 0.01 to 0.1 µm. This increase might be related to a delayed reaction of ZL. They also found that concrete modified with 20% ZL had better resistance to freeze–thaw cycles in de-icing salt solution [31].
NPAs were studied regarding their potential to enhance the frost resistance of concrete. The replacement of 10% PC with ZL reduced the strength loss after 150 cycles by more than 30% in comparison to the reference value [76]. Additionally, the study indicated the enhanced freeze–thaw resistance of both ZL-modified and reference mixes with the addition of an air-entraining agent, proving the positive effect of NPA.
One study reported that only 5% PC replacement produced better values in modified specimens than in the reference [42], while another study found that 10% ZL increased freeze–thaw resistance [77]. The findings of both studies confirm that a higher ZL content will deteriorate the freeze–thaw resistance of mortars. Researchers explain these findings by the pozzolanic activity of ZL, which causes the densification of the microstructure, thus prohibiting the expansion of ice crystals and subsequent damage.

3.6. Assessment of Concrete Surface

It is not easy to obtain a perfect surface appearance of cast concrete without any changes in colour and with a faultless texture. Concrete surface repairs with various mixes are often impractical and rarely work; therefore, quality requirements must be introduced and strictly followed to assess concrete casting work [78].
In most cases, freshly placed concrete contains many entrapped air voids [79]. For the hardened concrete to reach its design requirements, the mix must be compacted. This is a process that brings the solid-phase particles closer, thereby reducing the amount of entrapped air voids in the concrete mix [80,81]. Stiffer and drier concrete mixtures require more intensive compaction and longer compaction times. Certain admixtures improve the workability of the mix and make it easier to compact without increasing the water-to-cement ratio. It is well known that properly compacted concrete with a lower water content has better physical and mechanical properties [82]. PC content can be reduced and the cost of concrete mix lowered without compromising the quality of concrete. Stiffer concrete mixes need good compaction to achieve a good-quality surface finish [83].
A technological process must be established to achieve the perfect quality of concrete surface finish: the selection of a mix composition, concrete placing and compacting method, formwork system, form-release agents, workforce, and other factors.
We aimed to assess the surface finish of NPA-modified concrete by quantifying air voids, determining the biggest effective air void diameter, and calculating the air void area and the ratio between the air void area and the surface area assessed. Uniform birch plywood moulds coated with phenolic formaldehyde were used to create identical casting conditions for all test specimens. The moulds were covered with the same type of form-release agent and polished. The concrete was placed in two layers, and each layer was compacted on a vibration table at the same frequency and for an identical duration.
There are different methods to assess concrete surface finish. We assessed the surface quality according to four indicators: the quantity of surface air voids, the effective diameter of the largest air voids, the square area of air voids on the surface assessed, and the ratio of the air void square area to the assessed surface area. The results are provided in Table 6, and Figure 16 presents natural concrete surface images and processed images to better visualise the surface defects/surface air voids.
Six specimens of each composition were formed. Out of the six surfaces of each specimen, four surfaces were analysed (only side surfaces, excluding the top and the bottom surfaces). Each surface was cut to the dimensions of 95 × 95 mm using a programme. The average composition was derived from 24 (6 × 4) surfaces, each having an area of 95 × 95 mm.
Nine air voids with the largest effective diameter of 4.77 mm and a square area of 69 mm2 were identified in the specimen of composition PA0. When PC was replaced with 5% NPA, the number of air voids dropped to seven, the effective diameter was reduced to 4.71 mm, and the square area of assessed air voids decreased to 58 mm2. These results show that NPA, added even in small amounts, affects the concrete’s surface positively. With the increase in NPA content to 10–15%, the number of air voids assessed increased to 12 and 11, but the largest effective diameter of air voids decreased to 4.34 mm and 4.45 mm, respectively. However, the square area of the assessed air voids increased to 74 mm2. Although the number and square area of air voids in specimens PA10 and PA15 increased, the largest effective air void diameter decreased. The specimens with the highest NPA content (20%) produced the worst results. Compared to the reference composition, specimen PA20 had three times more assessed pores, and the largest effective air void diameter was 6.17 mm or 29% larger. The square area of assessed air voids increased to 212 mm2 or three times more than the reference specimen. A 15% NPA content could be used to achieve an excellent concrete surface finish, but the compaction time must be extended because the NPA-modified concrete mixture is less flowable. However, NPA reduces the likelihood of bleeding, the mixture is more stable and homogeneous; thus, the extended compaction time should not have any negative outcome. It should be also noted that concrete specimens containing 15% NPA had a warmer beige hue, different from the dark grey colour of reference specimens.

4. Conclusions

  • The incorporation of NPA causes air entrainment in the PC mixture (3.8% in the reference composition, 4.6% in the composition with 15% NPA). A low amount of NPA added increases the slump of the mixture. The addition of NPA reduces the density of hardened concrete and increases water absorption due to the lower specific density of NPA compared to the PC density.
  • The early compressive strength test results (at 7 days) showed that NPA deteriorates mechanical properties. The compressive strength gradually decreased, reaching a 29% drop in the specimens with the highest NPA content of 20%. Similar trends were observed in adjusted early compressive strength test results. Consistent with the findings of other authors, the test results suggest that pozzolanic reactions of NPA often occur in late stages of hydration, i.e., after 14 or more days.
  • In the specimens modified with 5% NPA (after 28 days), the compressive strength increased by 2.7%. When PC was replaced with 10% NPA, the compressive strength decreased slightly to 55.5 MPa. After the adjustment (recalculation) of strength results per unit weight of PC, the compressive strength of all specimens modified with up to 20% NPA was higher than the strength of the reference specimen.
  • The replacement of 5% PC with NPA caused a 13.13% increase in the total porosity. The open porosity also increased to 11.35%, and the closed porosity increased significantly to 1.14%. Similar trends were observed in the specimens modified with 10–15% NPA, where open and closed porosity values increased along with the total porosity. The closed porosity decreased in the specimens with a higher NPA content of 20%, although the total porosity increased. Freeze–thaw test results correlated with porosity test results—concrete with more closed pores was more durable and, thus, could sustain more freeze–thaw cycles. The porosity tests suggest that 15% is the optimum/maximum amount of NPA that can be added by weight to PC to produce durable concrete.
  • The surface finish of NPA-modified concrete was evaluated by quantifying air voids, determining the largest effective air void diameter, and calculating the air void square area and the ratio between the air void square area and the surface area assessed. A proportion of 15% NPA can be added to obtain an excellent surface finish in the exposed concrete. Concrete specimens containing 15% NPA had a warmer beige hue, different from the dark grey colour of reference specimens.
This research work is beneficial for materials science and construction engineering, showing that pozzolanic materials can be used to obtain better surface finishes in exposed concrete. In the near future, the authors will focus more on the use of waste materials such as fly ash, metakaolin, and water treatment sludge in cement systems in order to develop durable concrete products. These materials will also be used to develop concrete compositions and obtain exposed concrete surfaces that can be cast as structural elements (columns, walls, etc.).
The results of this study contribute to materials science and construction engineering by demonstrating that pozzolanic additives can significantly improve the surface finish of exposed concrete. The authors will continue exploring the incorporation of industrial by-products such as fly ash, metakaolin, and water treatment sludge into cementitious systems and propose formulations for the engineering of durable concrete elements. These formulations will be evaluated for both the performance and the quality of the surface finish of exposed concrete products.

Author Contributions

Conceptualisation, G.G. and D.K.; methodology, D.K. and G.G.; validation, G.G., D.K. and O.K.; formal analysis, G.G., D.K. and J.M.; investigation, G.G and D.K.; resources, O.K. and J.M.; data curation, J.M.; writing—original draft preparation, G.G and D.K.; writing—review and editing, G.G., D.K. and J.M.; visualisation, G.G. and D.K.; supervision, G.G. and O.K.; project administration, G.G. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Al-Kheetan, M.J.; Al-Tarawneh, M.; Ghaffar, H.S.; Chougan, M.; Jweihan, Y.S.; Rahman, M.M. Resistance of hydrophobic concrete with different moisturecontents to advanced freeze–thaw cycles. Struct. Concr. 2020, 22, E1050–E1061. [Google Scholar]
  2. Pereira, C.L.; Savastano, H.J.; Paya Bernabeu, J.J.; Santos, S.F.; Borrachero Rosado, M.V.; Monzó Balbuena, J.M.; Soriano Martinez, L. Use of highly reactive rice husk ash in the production of cement matrixreinforced with green coconut fiber. Ind. Crops Prod. 2013, 49, 88–96. [Google Scholar] [CrossRef]
  3. İpek, S. Macro and micro characteristics of eco-friendly fly ash-based geopolymer composites made ofdifferent types of recycled sand. J. Build. Eng. 2022, 52, 104431. [Google Scholar] [CrossRef]
  4. Öz, H.Ö.; Yücel, H.E.; Güneş, M.; Köker, T.Ş. Fly-ash-based geopolymer composites incorporating cold-bonded lightweight fly ash aggregates. Constr. Build. Mater. 2021, 272, 121963. [Google Scholar] [CrossRef]
  5. Niş, A.; Eren, N.A.; Çevik, A. Effects of recycled tyre rubber and steel fibre on the impact resistance of slag-based self-compacting alkali-activated concrete. Eur. J. Environ. Civ. Eng. 2023, 27, 519–537. [Google Scholar] [CrossRef]
  6. de Brito, J.; Kurda, R. The past and future of sustainable concrete: A critical review and new strategies on cement-based materials. J. Clean. Prod. 2021, 281, 123558. [Google Scholar]
  7. Singh, N.; Mithulraj, M.; Arya, S. Utilization of coal bottom ash in recycled concrete aggregates based self-compacting concrete blended with metakaolin. Resour. Conserv. Recycl. 2019, 144, 240–251. [Google Scholar] [CrossRef]
  8. Mangi, S.A.; Wan Ibrahim, M.H.; Jamaluddin, N.; Arshad, M.F.; Putra Jaya, R. Short-term effects of sulphate and chloride on the concrete containing coal bottom ash as supplementary cementitious material. Eng. Sci. Technol. Int. J. 2019, 22, 515–522. [Google Scholar] [CrossRef]
  9. Al-Yousuf, A.; Pokharel, T.; Lee, J.; Gad, E.; Abdouka, K.; Sanjayan, J. Effect of fly ash and slag on properties of normal and high strength concrete including fracture energy by wedge splitting test: Experimental and numerical investigations. Constr. Build. Mater. 2021, 271, 121553. [Google Scholar] [CrossRef]
  10. Zhang, J.; Ding, X.; Wang, Q.; Zheng, X. Effective solution for low shrinkage and low permeability of normal strength concrete using calcined zeolite particles. Constr. Build. Mater. 2018, 160, 57–65. [Google Scholar] [CrossRef]
  11. Khan, M.N.N.; Saha, A.K.; Sarker, P.K. Reuse of waste glass as a supplementary binder and aggregate for sustainable cement-based construction materials: A review. J. Build. Eng. 2020, 28, 101052. [Google Scholar] [CrossRef]
  12. El-Gamal, S.M.A.; Amin, M.S.; Ramadan, M. Hydration characteristics and compressive strength of hardened cement pastes containing nano-metakaolin. HBRC J. 2017, 13, 114–121. [Google Scholar] [CrossRef]
  13. Cook, D.J. Natural pozzolanas. In Cement Replacement Materials; Swamy, R.N., Ed.; Surrey University Press: Surrey, UK, 1986; p. 259. [Google Scholar]
  14. Martinez-Ramirez, S.; Blanco-Varela, M.T.; Erena, I.; Gener, M. Pozzolanic reactivity of zeolitic rocks from different Cuban deposits: Characterisation of reaction products. Appl. Clay Sci. 2006, 32, 40–52. [Google Scholar] [CrossRef]
  15. Martens, G.; Snellings, R.; van Balen, K.; Bicer-Simsir, B.; Verlooy, P.; Elsen, J. Pozzolanic reactions of common natural zeolites with lime and parameters affecting their reactivity. Cem. Concr. Res. 2009, 39, 233–240. [Google Scholar] [CrossRef]
  16. Chandra Paul, S.; Šavija, B.; Babafemi, A.J. A comprehensive review on mechanical and durability properties of cement-based materials containing waste recycled glass. J. Clean. Prod. 2018, 198, 891–906. [Google Scholar] [CrossRef]
  17. Rojas, M.F.; Cabrera, J. The effect of temperature on the hydration rate and stability of the hydration phases of metakaolin-lime-water systems. Cem. Concr. Res. 2002, 32, 133–138. [Google Scholar] [CrossRef]
  18. Shi, C. Pozzolanic reaction and microstructure of chemical activated lime-fly ash pastes. ACI Mater. J. 1998, 95, 537–545. [Google Scholar]
  19. Janotka, I.; Krajci, L. Utilization of natural zeolite in Portland cement of increased sulphate resistance. ACI Spec. Publ. 2003, 22, 223–229. [Google Scholar]
  20. Ahmadi, B.; Shekarchi, M. Use of natural zeolite as a supplementary cementitious material. Cem. Concr. Compos. 2010, 32, 134–141. [Google Scholar] [CrossRef]
  21. Payra, P.; Dutta, P.K. Zeolites: A primer. In Handbook of Zeolite Science and Technology; CRC Press: Boca Raton, FL, USA, 2003; pp. 1–24. [Google Scholar]
  22. Muraoka, K.; Chaikittisilp, W.; Okubo, T. Energy analysis of aluminosilicate zeolites with comprehensive ranges of framework topologies. Chemical Compositions, and Aluminum Distributions. J. Am. Chem. Soc. 2016, 138, 6184–6193. [Google Scholar] [CrossRef]
  23. Rahhal, V.F.; Pavlík, Z.; Tironi, A.; Castellano, C.C.; Trezza, M.A.; Černý, R.; Irassar, E.F. Effect of cement composition on the early hydration of blended cements with natural zeolite. J. Therm. Anal. Calorim. 2017, 128, 721–733. [Google Scholar] [CrossRef]
  24. Stanislao, C.; Rispoli, C.; Vola, G.; Cappelletti, P.; Morra, V.; Gennaro, M. Contribution to the knowledge of ancient Roman seawater concretes: Phlegrean pozzolan adopted in the construction of the harbour at Soli-Pompeiopolis (Mersin. Turkey). Period Miner. 2011, 80, 471–488. [Google Scholar]
  25. Mumpton, F.A. Natural zeolites. In Mineralogy and Geology of Natural Zeolites; Mumpton, F.A., Ed.; Mineralogical Society of America: Chantilly, VA, USA, 1981; pp. 1–18. [Google Scholar]
  26. Ulmanu, M. Mineralogy of natural zeolites. In Handbook of Natural Zeolites; Inglezakis, V.J., Zorpas, A.A., Eds.; Bentham Science Publishers: Sharjah, The United Arab Emirates, 2012; pp. 52–69. [Google Scholar]
  27. Feng, N.Q.; Li, G.Z.; Zang, X.W. High-strength and flowing concrete with a zeolitic mineral admixture. Cem. Concr. Aggreg. 1990, 12, 61–69. [Google Scholar] [CrossRef]
  28. Fragoulis, D.; Chaniotakis, E.; Stamatakis, M.G. Zeolitic tuffs of Kimolos Island, Aegean Sea, Greece and their industrial potential. Cem. Concr. Res. 1997, 27, 889–905. [Google Scholar] [CrossRef]
  29. Uzal, B.; Turanli, L. Blended cements containing high volume of natural zeolites: Properties, hydration and paste microstructure. Cem. Concr. Compos. 2012, 34, 101–109. [Google Scholar] [CrossRef]
  30. Valipour, M.; Pargar, F.; Shekarchi, M.; Khani, S. Comparing a natural pozzolan, zeolite, to metakaolin and silica fume in terms of their effect on the durability characteristics of concrete: A laboratory study. Constr. Build. Mater. 2013, 41, 879–888. [Google Scholar] [CrossRef]
  31. Vejmelková, E.; Koňáková, D.; Kulovaná, T.; Keppert, M.; Žumár, J.; Rovnaníková, P.; Keršner, Z.; Sedlmajer, M.; Černý, R. Engineering properties of concrete containing natural zeolite as supplementary cementitious material: Strength, toughness, durability, and hygrothermal performance. Cem. Concr. Compos. 2015, 55, 259–267. [Google Scholar] [CrossRef]
  32. Tran, Y.T.; Lee, J.; Kumar, P.; Kim, K.H.; Lee, S.S. Natural zeolite and its application in concrete composite production. Compos. Part B Eng. 2019, 165, 354–364. [Google Scholar] [CrossRef]
  33. Takemoto, K.; Uchikawa, H. Hydration of pozzolanic cement. In 7th International Congress on the Chemistry of Cement; Éditions Septima: Paris, France, 1980; Volume 1, pp. IV-2/1–IV-2/29. [Google Scholar]
  34. Nguyen, Q.H.; Lorente, S.; Duhard-Barone, A. Effect of the pore size of cement based materials on ionic transport. Constr. Build. Mater. 2017, 147, 160–167. [Google Scholar] [CrossRef]
  35. Neithalath, N.; Jain, J. Relating rapid chloride transport parameters of concretes to microstructural features extracted from electrical impedance. Cem. Concr. Res. 2010, 40, 1041–1051. [Google Scholar] [CrossRef]
  36. Sant, G.; Bentz, D.; Weiss, J. Capillary porosity depercolation in cement-based materials: Measurement techniques and factors which influence their interpretation. Cem. Concr. Res. 2011, 41, 854–864. [Google Scholar] [CrossRef]
  37. Yu, Z.; Ni, C.; Tang, M.; Shen, X. Relationship between water permeability and pore structure of Portland cement paste blended with fly ash. Constr. Build. Mater. 2018, 175, 458–466. [Google Scholar] [CrossRef]
  38. Zhang, J.; Bian, F.; Zhang, Y.; Fang, Z.; Fu, C.; Guo, J. Effect of pore structures on gas permeability and chloride diffusivity of concrete. Constr. Build. Mater. 2018, 163, 402–413. [Google Scholar] [CrossRef]
  39. Bernal Camacho, J.; Mahmoud Abdelkader, S.; Reyes Pozo, E.; Moragues Terrades, A. The influence of ion chloride on concretes made with sulfate-resistant cements and mineral admixtures. Constr. Build. Mater. 2014, 70, 483–493. [Google Scholar] [CrossRef]
  40. Pavlík, Z.; Fořt, J.; Pavlíková, M.; Kulovaná, T.; Černý, R. Characterization of Cement Pastes Containing Natural Zeolite as a Pozzolanic Admixture. Appl. Mech. Mater. 2015, 719, 206–209. [Google Scholar] [CrossRef]
  41. de La Cruz, J.C.; del Campo, J.M.; Colorado, D. Comparative study on porosity and permeability of conventional concrete and concrete with variable proportions of natural zeolite additions. Rev. Constr. 2015, 14, 72–78. [Google Scholar] [CrossRef]
  42. Bilim, C. Properties of cement mortars containing clinoptilolite as a supplementary cementitious material. Constr. Build. Mater. 2011, 25, 3175–3180. [Google Scholar] [CrossRef]
  43. Miller, S.A.; Horvath, A.; Ostertag, C.P. Greenhouse gas emissionsfrom concrete can be reducedbyusing mix proportions, geometricaspects, and age as designfactors. Environ. Res. Lett. 2015, 10, 114017–114028. [Google Scholar] [CrossRef]
  44. Minano, I.; Benito, F.; Parra, C.; Hidalgo, P. Concrete Sustainable Light and of High Performance Sustainable. Dev. Renov. Archit. 2017, 263–273. [Google Scholar] [CrossRef]
  45. Liu, B.; Yang, T. Image analysis for detection of bugholeson concrete surface. Constr. Build. Mater. 2017, 137, 432–440. [Google Scholar] [CrossRef]
  46. LST EN 197-1:2011; Cement—Part 1: Composition, Specifications and Conformity Criteria for Common Cements. Lithuanian Standards Board: Vilnius, Lithuania, 2011.
  47. LST EN 12620:2003+A1:2008; Aggregates for Concrete. Lithuanian Standards Board: Vilnius, Lithuania, 2003.
  48. LST EN 1008:2003; Mixing Water for Concrete—Specification for Sampling, Testing and Assessing the Suitability of Water, Including Water Recovered from Processes in the Concrete Industry, as Mixing Water for Concrete. Lithuanian Standards Board: Vilnius, Lithuania, 2003.
  49. LST EN 196-1:2016; Methods of Testing Cement—Part 1: Determination of Strength. Lithuanian Standards Board: Vilnius, Lithuania, 2016.
  50. LST EN 196-6:2010; Methods of Testing Cement—Part 6: Determination of Fineness. Lithuanian Standards Board: Vilnius, Lithuania, 2010.
  51. LST EN 12350-7:2009; Testing Fresh Concrete—Part 7: Air Content—Pressure Methods. Lithuanian Standards Board: Vilnius, Lithuania, 2009.
  52. LST EN 12350-2:2009; Testing Fresh Concrete—Part 2: Slump-Test. Lithuanian Standards Board: Vilnius, Lithuania, 2009.
  53. LST EN 12390-3:2019; Testing Hardened Concrete—Part 3: Compressive Strength of Test Specimens. Lithuanian Standards Board: Vilnius, Lithuania, 2019.
  54. LST EN 12390-3:2019; Testing Hardened Concrete—Part 4: Compressive Strength—Specification for Testing Machines. Lithuanian Standards Board: Vilnius, Lithuania, 2019.
  55. LST EN 1015-10:2002; Methods of Test for Mortar for Masonry. Part 10: Determination of Dry Bulk Density of Hardened Mortar. Lithuanian Standards Board: Vilnius, Lithuania, 2002.
  56. LST EN 13369:2018; Common Rules for Precast Concrete Products. Lithuanian Standards Board: Vilnius, Lithuania, 2018.
  57. Nagrockiene, D.; Daugela, A. Investigation into the properties of concrete modified with biomass combustion fly ash. Constr. Build. Mater. 2018, 174, 369–375. [Google Scholar] [CrossRef]
  58. Xu, W.; Chen, J.J.; Wei, J.; Zhang, B.; Yuan, X.; Xu, P.; Yu, Q.; Ren, J. Evaluation of inherent factors on flowability, cohesiveness and strength of cementitious mortar in presence of zeolite powder. Constr. Build. Mater. 2019, 214, 61–73. [Google Scholar] [CrossRef]
  59. Mehta, P.K. Natural Pozzolans: Supplementary Cementing Materials in Concrete; CANMET Special Publication: Athens, Greece, 1987; pp. 1–33. [Google Scholar]
  60. Tokushige, H.; Kamehima, H.; Kawakami, M.; Bier, T.A. Effect of use of natural zeolite as a mineral admixture and an aggregate on physical properties of cement mortar and porous concrete. In Proceedings of the 4th International Conference on Construction Materials: Performance, Innovations and Structural Implications, Nagoya, Japan, 24–26 August 2009; pp. 1231–1236. [Google Scholar]
  61. Ramezanianpour, A.A.; Mousavi, R.; Kalhori, M.; Sobhani, J.; Najimi, M. Micro and macro level properties of natural zeolite contained concretes. Constr. Build. Mater. 2015, 101, 347–358. [Google Scholar] [CrossRef]
  62. Poon, C.S.; Lam, L.; Kou, S.C.; Lin, Z.S. A study on the hydration rate of natural zeolite blended cement pastes. Constr. Build. Mater. 1999, 13, 427–432. [Google Scholar] [CrossRef]
  63. Koťátková, J.; Reiterman, P. Long-term properties of special concrete with natural additive. Sustain. Constr. Mater. Technol. 2016, 1, 317–324. [Google Scholar]
  64. Perraki, T.; Kontori, E.; Tsivilis, S.; Kakali, G. The effect of zeolite on the properties and hydration of blended cements. Cem. Concr. Compos. 2010, 32, 128–133. [Google Scholar] [CrossRef]
  65. Feng, N.; Yang, H.; Zu, L.-H. The strength effect of mineral admixture on cement concrete. Cem. Concr. Res. 1988, 18, 464–472. [Google Scholar]
  66. Shekarchi, M.; Libre, N.A.; Ahmadi, B.; Sabet, F.S. An Investigation on the effect of natural zeolite on rheology and stability of self-consolidating mortar. In Proceedings of the 6th International RILEM Symposium Self-Compacting Concrete, Montreal, QC, Canada, 26–29 September 2010; pp. 503–513. [Google Scholar]
  67. Samimi, K.; Kamali-Bernard, S.; Maghsoudi, A.A.; Lgcgm, S.K.B.; Civil, E. Resistance to chloride penetration of high strength self-compacting concretes: Pumice and zeolite effect. Int. J. Civ. Environ. Eng. 2018, 3, 250–259. [Google Scholar]
  68. Chan, S.Y.; Ji, X. Comparative study of the initial surface absorption and chloride diffusion of high performance zeolite, silica fume and PFA concretes. Cem. Concr. Compos. 1999, 21, 293–300. [Google Scholar] [CrossRef]
  69. Jana, D. A new look to an old pozzolan, clinoptilolite–a promising pozzolan in concrete. In Proceedings of the Twenty-ninth Conference on Cement Microscopy, Quebec City, PQ, Canada, 20–24 May 2007; pp. 168–206. [Google Scholar]
  70. Feng, N.; Feng, X.; Hao, T.; Xing, F. Effect of ultrafine mineral powder on the charge passed of the concrete. Cem. Concr. Res. 2002, 32, 623–627. [Google Scholar] [CrossRef]
  71. Bentz, D.P.; Jensen, O.M. Mitigation strategies for autogenous shrinkage cracking. Cem. Concr. Compos. 2004, 26, 677–685. [Google Scholar] [CrossRef]
  72. Lura, P.; Jensen, O.M.; Igarashi, S.I. Experimental observation of internal water curing of concrete. Mater. Struct. 2007, 40, 211–220. [Google Scholar] [CrossRef]
  73. Lee, H.; Hanif, A.; Usman, M.; Sim, J.; Oh, H. Performance evaluation of concrete incorporating glass powder and glass sludge wastes as supplementary cementing material. J. Clean. Prod. 2018, 170, 683–693. [Google Scholar] [CrossRef]
  74. Najimi, M.; Sobhani, J.; Ahmadi, B.; Shekarchi, M. An experimental study on durability properties of concrete containing zeolite as a highly reactive natural pozzolan. Constr. Build. Mater. 2012, 35, 1023–1033. [Google Scholar] [CrossRef]
  75. Ackley, M. Application of natural zeolites in the purification and separation of gases. Microporous Mesoporous Mater. 2003, 61, 25–42. [Google Scholar] [CrossRef]
  76. Markiv, T.; Sobol, K.; Franus, M.; Franus, W. Mechanical and durability properties of concretes incorporating natural zeolite. Arch. Civ. Mech. Eng. 2016, 16, 554–562. [Google Scholar] [CrossRef]
  77. Milovic, T.; Šupic, S.; Malešev, M.; Radonjanin, V. The Effects of Natural Zeolite as Fly Ash Alternative on Frost Resistance and Shrinkage of Blended Cement Mortars. Sustainability 2022, 14, 2736. [Google Scholar] [CrossRef]
  78. Kwasny, J.; Sonebi, M.; Amziane, S.; Plasse, J. Effect of mix composition on rheology and surface finish of cementbased mortars. Constr. Build. Mater. 2015, 89, 102–109. [Google Scholar] [CrossRef]
  79. Hilal, A.A.; Thom, N.H.; Dawson, A.R. On entrained pore size distribution of foamed concrete. Constr. Build. Mater. 2015, 75, 227–233. [Google Scholar] [CrossRef]
  80. Harding, M.A. Vibrating Concrete in Wall Forms. Concr. Constr. 1995, 40, 180–184. [Google Scholar]
  81. Samuelsson, P. Voids in Concrete Surfaces. ACI J. 1970, 67, 868–874. [Google Scholar]
  82. Han, L.H.; Yao, G.H. Influence of concrete compaction on the strength of concrete-filled steel RHS columns. J. Constr. Steel Res. 2003, 59, 751–767. [Google Scholar] [CrossRef]
  83. Tastani, S.P.; Balafas, I.; Dervisis, A.; Pantazopoulou, S.J. Effect of core compaction on deformation capacity of FRP-jacketed concrete columns. Constr. Build. Mater. 2013, 47, 1078–1092. [Google Scholar] [CrossRef]
Buildings 15 01617 g001
Figure 1. Particle size distribution of the reference: (a) PC; (b) NPA.
Figure 1. Particle size distribution of the reference: (a) PC; (b) NPA.
Buildings 15 01617 g001
Buildings 15 01617 g002
Figure 2. Images of NPA particles obtained by SEM: (a) magnified × 3000 (b) magnified × 10,000.
Figure 2. Images of NPA particles obtained by SEM: (a) magnified × 3000 (b) magnified × 10,000.
Buildings 15 01617 g002
Buildings 15 01617 g003
Figure 3. X-ray diffractogram of NPA.
Figure 3. X-ray diffractogram of NPA.
Buildings 15 01617 g003
Buildings 15 01617 g004
Figure 4. Image processing algorithm.
Figure 4. Image processing algorithm.
Buildings 15 01617 g004
Buildings 15 01617 g005
Figure 5. Air content results of fresh concrete.
Figure 5. Air content results of fresh concrete.
Buildings 15 01617 g005
Buildings 15 01617 g006
Figure 6. Results of fresh concrete flowability.
Figure 6. Results of fresh concrete flowability.
Buildings 15 01617 g006
Buildings 15 01617 g007
Figure 7. Density results of concrete.
Figure 7. Density results of concrete.
Buildings 15 01617 g007
Buildings 15 01617 g008
Figure 8. UPV results of concrete.
Figure 8. UPV results of concrete.
Buildings 15 01617 g008
Buildings 15 01617 g009
Figure 9. Compressive strength of concrete after 7 days of curing.
Figure 9. Compressive strength of concrete after 7 days of curing.
Buildings 15 01617 g009
Buildings 15 01617 g010
Figure 10. Normalised compressive strength after 7 days of curing.
Figure 10. Normalised compressive strength after 7 days of curing.
Buildings 15 01617 g010
Buildings 15 01617 g011
Figure 11. Compressive strength of concrete after 28 days of curing.
Figure 11. Compressive strength of concrete after 28 days of curing.
Buildings 15 01617 g011
Buildings 15 01617 g012
Figure 12. Normalised compressive strength after 28 days of curing.
Figure 12. Normalised compressive strength after 28 days of curing.
Buildings 15 01617 g012
Buildings 15 01617 g013
Figure 13. Water absorption results of modified concrete.
Figure 13. Water absorption results of modified concrete.
Buildings 15 01617 g013
Buildings 15 01617 g014
Figure 14. Results of concrete porosity (total, open, closed).
Figure 14. Results of concrete porosity (total, open, closed).
Buildings 15 01617 g014
Buildings 15 01617 g015
Figure 15. Results of predicted frost resistance (cycles).
Figure 15. Results of predicted frost resistance (cycles).
Buildings 15 01617 g015
Buildings 15 01617 g016
Figure 16. Photo documentation of NPA-modified concrete surfaces.
Figure 16. Photo documentation of NPA-modified concrete surfaces.
Buildings 15 01617 g016
Table 1. Chemical compositions of PC and NPA.
Table 1. Chemical compositions of PC and NPA.
BindersOxide Content, %
CaOSiO2Al2O3Fe2O3MgOSO3K2ONa2OLOI
PC61.419.55.03.13.92.51.10.13.4
NPA3.372.512.51.70.6-3.60.25.6
Table 2. Main physical properties of PC and NPA.
Table 2. Main physical properties of PC and NPA.
PropertiesPCNPA
Specific density, kg/m331502350
Average particle size, μm17.629.0
Specific surface area, m2/kg440760
Table 3. Sand 0/4 fr. characteristics.
Table 3. Sand 0/4 fr. characteristics.
Essential CharacteristicsDeclared/Limit Value
Grain size (fraction)0/4
Particle density2650 kg/m3
Fineness modulus4.0
Fines contentf3
Organic impurities (humus)none
Table 4. Gravel 4/16 fr. characteristics.
Table 4. Gravel 4/16 fr. characteristics.
Essential CharacteristicsDeclared/Limit Value
Grain size (fraction)4/16
Particle density2600 kg/m3
Fines contentf1.5
Freeze–thaw resistanceF1
Organic impurities (humus)none
Table 5. Compositions of concrete mixes, kg/m3.
Table 5. Compositions of concrete mixes, kg/m3.
CompositionsPA0PA5PA10PA15PA20
PC355.00337.27319.55301.82284.00
NPA-17.7535.5053.2571.00
NPA, %05101520
Sand890890890890890
Gravel10251025102510251025
Plasticiser2.842.842.842.842.84
Water174.64174.64174.64174.64174.64
W/C0.490.520.550.580.61
Table 6. Results of concrete surface finish assessment indicators.
Table 6. Results of concrete surface finish assessment indicators.
CompositionAir Void QuantityLargest Effective Air Void Diameter, mmAir Void Sq. Area (mm2):Ratio of Air Void Sq. Area to Assessed Surface Area
PA094.77690.19
PA574.71580.16
PA10124.34740.21
PA15114.45740.21
PA20276.172120.60
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Girskas, G.; Kriptavičius, D.; Kizinievič, O.; Malaiškienė, J. Effect of Pozzolanic Additive on Properties and Surface Finish Assessment of Concrete. Buildings 2025, 15, 1617. https://doi.org/10.3390/buildings15101617

AMA Style

Girskas G, Kriptavičius D, Kizinievič O, Malaiškienė J. Effect of Pozzolanic Additive on Properties and Surface Finish Assessment of Concrete. Buildings. 2025; 15(10):1617. https://doi.org/10.3390/buildings15101617

Chicago/Turabian Style

Girskas, Giedrius, Dalius Kriptavičius, Olga Kizinievič, and Jurgita Malaiškienė. 2025. "Effect of Pozzolanic Additive on Properties and Surface Finish Assessment of Concrete" Buildings 15, no. 10: 1617. https://doi.org/10.3390/buildings15101617

APA Style

Girskas, G., Kriptavičius, D., Kizinievič, O., & Malaiškienė, J. (2025). Effect of Pozzolanic Additive on Properties and Surface Finish Assessment of Concrete. Buildings, 15(10), 1617. https://doi.org/10.3390/buildings15101617

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop