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Article

Influence of HPMC and VAE on the Properties of Geopolymer Mortar

by
Wenjun Ji
1,
Pengfei Chen
2,
Ying Lu
1,
Zeyang Zhang
2,
Baolong Shan
1,
Sha Li
2,*,
Mengyan Chi
1 and
Haifeng Yu
2,*
1
China Construction First Group Decoration Co., Ltd., Beijing 100161, China
2
School of Civil Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China
*
Authors to whom correspondence should be addressed.
Buildings 2025, 15(19), 3621; https://doi.org/10.3390/buildings15193621
Submission received: 9 September 2025 / Revised: 1 October 2025 / Accepted: 4 October 2025 / Published: 9 October 2025
(This article belongs to the Section Building Materials, and Repair & Renovation)
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Abstract

The delamination of building facades creates a critical demand for inorganic adhesive mortars with high long-term adhesion. Geopolymer (GP) represents an eco-friendly alternative to Portland cement (PC). However, the effect of polymer additives, commonly used in cement-based adhesive mortars, on GP mortar remains insufficiently studied. This study examines the effects of hydroxypropyl methylcellulose (HPMC) and vinyl acetate-ethylene (VAE) polymer on the workability, mechanical properties, durability, and microstructure of GP mortar. Results show that an optimal HPMC content (0.4 wt%) improves the fluidity, compressive strength, and adhesive strength of GP mortar, approximately 6%, 16%, and 20%, respectively. These enhancements are attributed to the incorporation of uniformly distributed microbubbles in the mortar matrix. Beyond this optimal content, however, HPMC impairs flowability and adhesion due to its thickening effect. In contrast, VAE addition significantly enhanced adhesive strength by approximately 28%, albeit at the cost of a 17% reduction in compressive strength, resulting from the retardation of the alkali activation process. This gain in adhesion is associated with the formation of a continuous polymer film that establishes both physical interlocking and chemical bonding with the GP matrix. Furthermore, HPMC improved the durability of the GP mortar, while VAE did not contribute to this aspect. These insights offer valuable guidance for designing high-performance GP-based adhesive mortars suitable for building applications.

1. Introduction

The delamination of building facades is a common problem in construction. The insufficient adhesive strength of the mortar connecting the structural and decorative layers is one of the main causes of this problem. Most existing adhesive mortars are formulated by mixing organic glue with cement mortar. However, these materials suffer from high carbon emissions, are prone to degradation, and exhibit insufficient water and corrosion resistance. Therefore, it is important to develop inorganic adhesive mortars with low-carbon emissions, high adhesion, and high durability.
Geopolymer (GP) is inorganic material with properties comparable to those of organic polymers [1]. It offers advantages such as recyclability, high adhesive strength, and excellent resistance to acid, alkali, and high temperatures [2]. Existing studies have found that the GP matrix contains minimal high-calcium minerals such as tricalcium silicate. Instead, it undergoes alkali activation and polycondensation reactions, ultimately generating a large number of spatially reticulated C-(A)-S-H and N-A-S-H gels [3]. Compared to the substantial calcium hydroxide (CH) initially produced by cement hydration, these gels are more likely to form a dense interfacial transition zone with aggregates or existing substrates [4]. The alkali activators contained in GP mortar can also react with the Al and Si reactive components in the interfaces of old mortars to further enhance the adhesive properties of the interfacial transition zones [5,6]. Therefore, utilizing solid waste through alkali activation technology to develop environmentally friendly adhesive mortars with high durability is feasible. This approach offers a promising solution to the problem of facade delamination.
Cellulose ether (CE) and dispersible latex powder (VAE) are indispensable additives in existing adhesive mortars. CE is a class of polymeric compounds with an ether structure. Studies show that CE adsorbs onto cement particle surfaces, significantly enhancing the water retention of cement-based materials [7,8] and improving the adhesion and crack resistance of mortar [9]. The inhibitory effect of CE on C-S-H gel formation via molecular adsorption is stronger than its effect on C3S mineral dissolution. The ether bonds can form coordination bonds with Ca2+ on C-S-H surfaces. This not only alters the morphology of hydration products but also inhibits ion migration through steric hindrance, thereby delaying the hydration exotherm peak [10,11]. However, CE addition increases porosity, particularly the volume of large pores, and alters pore shape and distribution. This leads to a more significant reduction in compressive strength than in flexural strength. A comparative study of CE types indicated that hydroxypropyl methylcellulose (HPMC) most effectively improves mortar adhesion [12]. When CE molecules contain methyl groups, their surface activity is higher, but their incorporation leads to a reduction in mortar strength [8]. The porosity caused by the addition of HPMC, on the other hand, helps to reduce the weight of the material, improve its thermal performance, and reduce energy consumption in construction [13].
VAE consists of polymer particles with a core-shell structure based on an ethylene-vinyl acetate copolymer, and it exhibits excellent film-forming and adhesive properties [14]. The polymer film generated by VAE can effectively fill and seal the pores, enhance the impermeability, and reduce the drying shrinkage [15,16]. The appropriate amount of VAE can significantly improve the adhesive strength, shear strength and tensile strength of cement-based mortar [14,17], raise the flexibility and extensibility of rubber mortar [18]. The incorporation of VAE, however, introduces entrapped air bubbles into the system [19]. An inhomogeneous distribution of these bubbles can disrupt the integrity of the pore structure, resulting in reduced compressive strength [20,21] and diminished long-term durability [22]. In contrast, several studies have reported that VAE addition does not necessarily increase overall porosity. Instead, the observed strength reduction has been attributed to its inhibitory effect on the hydration process [23].
In summary, HPMC and VAE are effective in improving the bond performance of cement-based mortars. However, their effects and mechanisms on GP mortar remain unclear. To enhance the durability of GP mortar, it is essential to elucidate the modification mechanisms of HPMC and VAE. Based on this, this paper systematically investigates the modification mechanisms of HPMC and VAE on the workability, mechanical properties, and durability of GP mortar. It is of great significance to promote the high value-added utilization of solid waste, improve durability and reduce the cost and carbon emission of adhesive mortar.

2. Materials and Experiments

2.1. Materials

Grade-II Class F fly ash (FA) was obtained from Hebei Kexu Building Materials Co. (Lingshou County, Shijiazhuang City, Hebei Province, China), Ltd. Granulated blast-furnace slag (GBFS), classified as high-quality and highly reactive according to GB/T 203-2008, was sourced from Jinghang Mineral Products Co., Ltd. (Lingshou County, Shijiazhuang City, Hebei Province, China). Figure 1 and Table 1 present the scanning electron microscopy (SEM) micrographs and chemical compositions of these binders, respectively.
The vinyl acetate-ethylene (VAE) copolymer was supplied by Langfang Tianya Energy-Saving Technology Co., Ltd. (Langfang City, Hebei Province, China), with glass transition temperature (Tg) less than 5 °C. Hydroxypropyl methylcellulose (HPMC) was obtained from Chuangsheng Building Materials Chemical Co., Ltd. (Shijiazhuang City, Hebei Province, China), exhibiting the carbonization and discoloration temperatures of 280–300 °C and 190–200 °C, respectively. The viscosity of HPMC provided by the manufacturer is 193,000/mpa·s (4.0% at 20 °C). As shown in Figure 2, VAE particles are spheroidal, whereas HPMC adopts a chain-like morphology. Their chemical compositions are listed in Table 2.
The fine aggregate was Zhengding River sand, with a mud content below 1%, a moisture content below 0.3%, and a fineness modulus of 2.63 after screening and grading, classifying it as medium sand with continuous grading in Zone II.
Alkali activated solution (AAS) was prepared by mixing sodium hydroxide and water glass. The sodium hydroxide (NaOH), with a purity of ≥99% and a pH greater than 14, was obtained from Longbang Chemical (Cangzhou City, Hebei Province, China). Water glass was produced from Bengbu Jingcheng Chemical Co., Ltd. (Bengbu City, Anhui Province, China), with a pH of 11.3 and a solid content of 34.8%. Both the NaOH solution (10 mol/L) and the water glass solution needed to be prepared one day before the experiment. The water glass solution was prepared by diluting industrial-grade water glass with water in a volume ratio of 1:1. Both this and the NaOH solution (10 mol/L) were prepared one day in advance. Then the two solutions were mixed in proportion according to the experimental design. The water used was tap water.

2.2. Experimental Design

Based on previous research and practical application requirements [24], seven mixture proportions were designed, as detailed in Table 3. This study systematically investigated the effects of HPMC and VAE dosage on the workability, mechanical properties (compressive, flexural, split tensile, and adhesive strength), and durability of geopolymer (GP) mortar.
Considering the significant influence of environmental conditions on the service life of adhesive mortars, three curing regimes were designed: standard curing (E1, T ≈ 20 °C, RH ≥ 90%), natural curing (E2, T = 15–25 °C, RH = 30–55%), and sealed natural curing (E3, T and RH were same to E2, double layer sealing of cling film). These regimes were used to investigate the effect of the curing environment on the mechanical properties of the GP mortar. Furthermore, the durability of the GP adhesive mortars was evaluated under three aggressive environments: water immersion, sulfate attack, and high temperature.

2.3. Experimental Method and Process

The preparation process for the GP adhesive mortar is illustrated in Figure 3. Specimens were demolded after 24 h and subsequently cured under the designated conditions until the testing age.
After 28 days of standard curing, cement mortar blocks (4 cm × 4 cm × 16 cm) were cut into 4 cm × 4 cm × 2 cm substrates using a cutting machine. To reduce errors in the tensile adhesive strength tests, 2-mm-deep grooves were made on the bonding surface of the cement substrates. A custom-fabricated apparatus (Figure 4) was used for this purpose. After casting the fresh GP mortar, the grooved cement substrates were placed on its surface to form the adhesive strength specimens (According to JC/T 547-2017 [25], with the size of the substrate changed from 50 mm to 40 mm). These specimens were then stored in different curing environments until the designated testing ages.
The setting time and fluidity of the GP mortars were determined by following the standard test methods specified in GB/T 1346-2024 [26] and GB/T 2419-2005 [27], respectively. Flexural and compressive strengths were referred to GB/T 17671-2021 [28]. The split tensile strength was determined following GB/T 29417-2012 [29]. The Adhesive strength was tested with reference to JGJ/T 70-2009 [30] and JC/T 547-2017 [25]. The adhesive strength tests on the GP mortar–cement matrix specimens were conducted at different ages using the apparatus shown in Figure 5.
The resistance to water, acid, and high temperature of the GP mortars was evaluated after 28 days of curing. For the water resistance test, specimens were immersed in a water tank located in the standard curing room. The water level was maintained at least 2 cm above the top of the specimens throughout the 14-day soaking period. Subsequently, the specimens were removed, surface water was wiped off, and they were left at room temperature for one hour before strength testing.
The sulfate corrosion experiment was conducted according to GB/T50082-2024 [31], as shown in Figure 6. Thermal aging experiment was carried out according to JC/T 547-2017 [25]. Based on existing results indicating that exterior wall temperatures can reach 88.6 °C in summer [32], the thermal cycle was set between 20 °C and 80 °C. After 14 days of thermal cycling, the mechanical properties of the GP mortar were measured.
In order to clearly characterize the effects of water immersion, sulfate attack, and high temperature on the mechanical properties of GP mortars, the corrosion resistance coefficient Kij was introduced to characterize the resistance of GP mortars to the environments, as shown below:
K i j = f j n f j 0
where: Ki—corrosion resistance coefficient (%); fj0—the strength before erosion, MPa; fjn—the strength after erosion, MPa; “i = w”—immersion in water; “i = s”—sulfate attack; “i = T”—high temperature; fc (j = c)—compressive strength; fcf (j = cf)—flexural strength; ft (j = t)—tensile strength; fa (j = a)—adhesive strength.
X-ray diffraction (XRD) analysis was carried out using a SmartLab 9KW X-ray diffractometer manufactured by Rigaku Corporation of Japan, with a scanning speed of 5°/min, a step size of 0.02°, and a scanning range of 5° to 100°. Scanning electron microscope (SEM) test was conducted by HITACHI, Tokyo, Japan, focusing on the analysis of the microstructure at the interface between the adhesive mortar and the substrate.

3. Results and Analysis

3.1. Workability

The effects of HPMC and VAE dosage on the workability of GP mortar are shown in Figure 7. As shown in Figure 7a, the initial and final setting times of the GP mortar initially increased and then decreased as the HPMC dosage increased. When 0.4% of HPMC was added, the initial and final setting times were extended by 28.6% and 22.5%, respectively. This indicates that the addition of appropriate HPMC can prolong the initial and final setting time of GP mortar. The effect of VAE on the setting times showed an opposite trend, first shortening and then slightly increasing. At low dosages, the thickening effect of VAE was more pronounced, leading to shorter setting times. However, at higher dosages, VAE’s moisture-retaining ability increased, which prolonged the hydration reaction and consequently increased the setting time [33].
The fluidity of the GP mortar first increased and then decreased with higher HPMC dosage, peaking at a dosage of 0.2% (a 4.1% increase over the baseline group). This is mainly due to the high water retention of cellulose ether, which helps water to form a water film between mortar particles, reduces the frictional resistance between solid particles, and increases the inter-slurry fluidity. However, too much HPMC will adsorb free water through hydrogen bonding, increasing the viscosity of the slurry and leading to a decrease in flowability. The influence of VAE on fluidity followed a pattern similar to its effect on setting time. At a 2% dosage, VAE absorbed water, causing a significant decrease in fluidity. However, at higher dosages, the film-forming and lubricating properties of VAE became dominant [34], leading to an improvement in fluidity.

3.2. Mechanical Strength

By comparing the mechanical properties of GP mortars with different dosages of HPMC and VAE, as shown in Figure 8, it was found that with the increase of HPMC dosage, the flexural strength of GP mortar showed a slight upward trend overall, the compressive strength value first increased and then slightly decreased, and the 28 day tensile strength gradually decreased. However, the 7-day tensile strength of GP mortar mixed with HPMC was higher than that of the reference group. The adhesive strength showed a trend of first increasing and then decreasing. However, excessive HPMC dosage led to the formation of air bubbles due to its air-entraining effect, which reduced the compactness and homogeneity of the mortar, thereby weakening its strength [35].
The addition of VAE was detrimental to the flexural and compressive strength of GP mortar. With the increase of VAE content, the flexural and compressive strength decreased. However, it slightly improved the tensile strength and significantly enhanced the adhesive strength. At a VAE content of 6%, the 28-day adhesive strength reached 1.79 MPa, which exceeds the minimum requirement of 0.6 MPa specified in the JG/T 287-2013 standard [36]. The mechanism involves the synchronization of the VAE film-forming process with the GP mortar hydration [37]. The amount of polymer film formed increases with VAE content, thereby enhancing the adhesive and tensile strengths. However, the water absorption of VAE may delay the hydration reaction process, leading to incomplete reaction of the cementitious material and resulting in a decrease in the flexural and compressive strength of GP mortar [20,38]. The effect of VAE on the strength of GP mortar is similar to that of VAE on the strength of cement-based mortar. The optimal dosage of VAE can enhance interfacial bonding and flexural strength, while excessive use can increase porosity and delay the hydration reaction process [23].

3.3. Durability

The Chinese regulations clearly stipulate the adhesive strength limits of adhesive mortar before and after immersion in water. Therefore, the changes in the mechanical properties of seven GP mortar mixes before and after water immersion were compared. Additionally, the high-temperature aging resistance and sulfate corrosion resistance of the GP adhesive mortar were investigated.

3.3.1. Water Immersion

Figure 9 shows that after immersion, most mechanical properties of the GP mortars decreased, except for a slight increase in the tensile strength of the reference and HPMC groups. A comparison of the corrosion resistance coefficients before and after immersion revealed that the GP mortar with HPMC exhibited slightly higher coefficients than the reference group in flexural, compressive, and tensile strength. HPMC had a significant effect on improving the corrosion resistance coefficient for adhesive strength, which increased by over 25%. With the increase of VAE content, the adhesion strength-corrosion resistance coefficient of GP mortar showed a trend of first increasing and then decreasing. At a content of 4%, it increased by approximately 8%. However, the addition of VAE was detrimental to the flexural, compressive, and tensile strength of GP mortar after immersion. The decrease in the corrosion resistance coefficient for tensile strength was particularly significant. The microstructure changes of GP mortar shown in SEM images can precisely explain the above phenomenon.

3.3.2. Sulphate Attack

To compare the effects of HPMC and VAE on sulfate and high-temperature resistance, the X0.4 and V6 series, which exhibited good adhesion in previous tests, were selected. These were compared with the reference group to evaluate the durability improvement offered by HPMC and VAE.
Figure 10 compares the changes in mechanical properties before and after sulfate attack for the X0.4, V6, and reference groups. It can be clearly seen that HPMC helps to improve the ability of GP mortar to resist sulfate attack, and the coefficients of various mechanical properties against sulfate attack are larger than those of the reference group, especially the enhancement effect on tensile strength. In contrast, the improvement effect of VAE was not ideal. The addition of VAE adversely affected the sulfate resistance for all mechanical properties except adhesive strength. This is related to its loose microstructure, which allows sulfate ions to penetrate the GP matrix more easily, leading to reduced resistance.

3.3.3. High Temperature

The changes in the mechanical properties of X0.4, V6 and the reference group before and after high temperature cycling at 80–20 °C are shown in Figure 11. The addition of 0.4% HPMC did not significantly reduce the mechanical properties after high temperature exposure; instead, it increased the corrosion resistance coefficients for flexural and tensile strength by approximately 6%. These findings are consistent with the study by Batista et al., which reported that HPMC improves water retention and thermal insulation in rendering mortars, while also reducing bulk density due to increased porosity [13].
The addition of VAE significantly reduced the high-temperature resistance of GP mortar, especially for its flexural and adhesive strength. After high temperature, the corrosion resistance coefficient of flexural and adhesive strength decreased by about 24% and 13%, respectively. It is speculated that the above results are related to the structural damage of VAE polymer film. Existing research has confirmed that the polymer film formed by VAE in cement mortar undergoes structural damage after a 70 °C heat aging test [39].

3.3.4. Effect of Curing Conditions

Figure 12 shows the effects of three curing environments, E1 (standard curing), E2 (natural curing), and E3 (natural sealing curing), on the flexural, compressive, tensile, and adhesive strengths of the reference, X0.4, and V6 series at 3, 7, and 28 days. The results reveal that standard curing and natural sealing curing are more favorable for the development of mechanical properties in GP mortar. With increasing age, the natural sealing curing can equal or even exceed the standard curing. This is consistent with the results of the previous study [40]. It is impossible to achieve a standard curing environment during on-site construction. Therefore, the mechanical properties of GP mortar can be guaranteed by sealing during construction.

3.4. SEM Analysis

A comparison of the SEM micrographs for sample X0.4 (with 0.4% HPMC), sample V6 (with 6% VAE), and the reference group (Figure 13) reveals distinct microstructural features. The micrograph of the reference group, shown in Figure 13a, displays a relatively dense matrix structure. However, prominent cracks are observable at the adhesive interface with the cement mortar substrate. This observation is consistent with the mechanical property results for the reference group, which exhibited higher compressive strength but lower tensile and adhesive strengths. In contrast, the inter-facial transition zones between X0.4/V6 series and the cement-based substrate exhibited a more continuous and compact structure compared to the reference group, with no obvious cracks observed. This explains why the adhesive strengths of X0.4 and V6 were higher than that of the reference group.
Further examination of the V6 sample via high-magnification SEM (Figure 13d) indicated that its interfacial surface was covered by continuous film-like material. This polymer film, derived from the VAE emulsion, enhances interfacial adhesion through two primary mechanisms: first, by forming a physical bridge across microcracks in the matrix, and second, through chemical bonding between hydroxyl (-OH) groups in the polymer and hydration products of the cementitious substrate [41,42].
However, while the polymer film improves adhesion, it also introduces a “soft interlayer effect,” which restricts the extent to which compressive strength can be improved in the GP mortar [34,43]. As revealed in Figure 13c, the V6 mortar exhibits a looser and more porous microstructure compared to the X0.4 and reference samples. The structure contains multiple irregular cracks and a greater proportion of unreacted material, which can be attributed to the retardation of geopolymerization and hydration reactions by VAE. The delayed reaction kinetics result in incomplete reaction progression and a higher content of unreacted precursors in the hardened matrix.
According to the mapping diagrams of the three samples (Figure 14), more Na, Al, Si and O substances (presumably N-A-S-H gel) were generated in X0.4 sample (with 0.4% HPMC), while the signal of calcium containing substances was weak and could not be clearly shown in the spectrum. The enhanced formation of N-A-S-H with HPMC addition is linked to its high sodium sulfate content. The XRD results confirm this enhancement, which is consistent with established findings that sodium sulfate promotes N-A-S-H gel formation, by providing additional sodium ions [44].

3.5. XRD Analysis

The XRD patterns of X0.4, V6, and reference group samples after 28 days of curing are shown in Figure 15. The results indicate that, compared to the reference group without additives, the diffraction peaks of amorphous silica and C-S-H gel in X0.4 and V6 samples were significantly weakened. The increase in sodium aluminium silica is more pronounced in the X0.4 samples’ XRD pattern. Combined with the mapping results, it is speculated that the sodium aluminium silica is N-A-S-H gel [45]. These microstructural changes explain why the durability of the X0.4 specimen is higher compared to the reference group and V6. Additionally, mullite and unreacted calcium silicate (C-S) phases were observed in the XRD spectra of the X0.4 and V6 samples. The presence of unreacted phases confirms the delayed hydration process of geopolymers due to the addition of HPMC and VAE, consistent with mechanical, durability, and SEM observations.
The action mechanisms of VAE and HPMC diverge fundamentally, with the former exerting chemical inhibition and the latter providing physical and physicochemical enhancement. For VAE, the mechanism involves the alkaline hydrolysis of acetate ester groups, releasing CH3COO- ions that sequester Ca2+ to form calcium acetate [46]. This consumption of calcium ions disrupts the ionic equilibrium, ultimately suppressing the nucleation and growth of C-S-H gel [46]. In contrast, HPMC enhances the system through multiple complementary pathways. It acts as a physical barrier by adsorbing onto particle surfaces, delaying the dissolution reaction. Its excellent water-retaining property enables internal curing, promoting prolonged hydration and later-age strength gain [47]. Additionally, the incorporated air bubbles improve workability and facilitate the formation of a denser microstructure, which collectively boosts mechanical performance and durability.

4. Conclusions

This study systematically investigates the effects of HPMC and VAE polymers on the properties of geopolymer (GP) mortar based on industrial solid waste. The results indicate that both polymers enhance the adhesive strength of the mortar, though their overall influences are contrasting. An optimal HPMC content (0.4%) improves compressive strength and refines the microstructure by virtue of its water-retaining capacity, whereas excessive incorporation leads to air entrainment and reduced matrix density, thereby diminishing flexural and splitting tensile strengths. In contrast, the addition of VAE markedly increases splitting tensile and adhesive strength—reaching a peak adhesion of 1.79 MPa at 6% dosage, despite progressively reducing compressive and flexural properties. Microstructural analysis reveals that VAE consumption of OH− and Ca2+ inhibits geopolymerization and C-S-H gel formation, resulting in higher porosity. Nevertheless, the in situ-formed polymer films act as effective bridges between reaction products and enhance interfacial bonding, which explains the improved adhesion. In terms of durability, HPMC significantly strengthens resistance to water, acid, and high-temperature exposure, while VAE exerts a negative impact. Furthermore, sealed curing is demonstrated to be a viable alternative to standard curing, offering equivalent performance.
In light of these complementary characteristics, future research should aim to develop an integrated HPMC-VAE system to synergistically enhance the overall performance of geopolymer mortar.

Author Contributions

Conceptualization, W.J. and S.L.; validation, B.S. and M.C.; formal analysis, S.L. and P.C.; investigation, P.C. and Z.Z.; resources, H.Y. and S.L.; data curation, P.C. and Z.Z.; writing—original draft preparation, P.C. and Z.Z.; writing—review and editing, S.L.; supervision, Y.L. and H.Y.; project administration, M.C. and S.L.; funding acquisition, W.J. and Y.L. All authors have read and agreed to the published version of the manuscript.

Funding

This work was financially supported by Hebei Province Department of Education Fund (QN2025425), Hebei Province Foundation for Returned Scholars (C20220320), Dr. startup funds (1181389), and Sub project of China Construction Engineering Corporation’s Technology Research and Development Project (CSCEC-PT-015-203).

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

Author Wenjun Ji, Ying Lu, Baolong Shan, Mengyan Chi was employed by the company China Construction First Group Decoration Corporation Limited. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Buildings 15 03621 g001
Figure 1. SEM micrographs for raw binder materials.
Figure 1. SEM micrographs for raw binder materials.
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Figure 2. SEM micrographs for VAE and HPMC.
Figure 2. SEM micrographs for VAE and HPMC.
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Figure 3. Preparation process of GP adhesive mortar.
Figure 3. Preparation process of GP adhesive mortar.
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Figure 4. Preparation of the adhesive strength specimens.
Figure 4. Preparation of the adhesive strength specimens.
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Figure 5. Adhesive strength apparatus.
Figure 5. Adhesive strength apparatus.
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Figure 6. Sulfate corrosion experiment process.
Figure 6. Sulfate corrosion experiment process.
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Figure 7. Workability of GP mortars.
Figure 7. Workability of GP mortars.
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Figure 8. Mechanical properties of GP mortar specimens at different curing ages.
Figure 8. Mechanical properties of GP mortar specimens at different curing ages.
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Figure 9. Mechanical properties of GP mortar specimens before and after water immersion.
Figure 9. Mechanical properties of GP mortar specimens before and after water immersion.
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Figure 10. Mechanical properties of GP mortar specimens before and after sulphate attack.
Figure 10. Mechanical properties of GP mortar specimens before and after sulphate attack.
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Figure 11. Mechanical properties of GP mortar specimens before and after high temperature.
Figure 11. Mechanical properties of GP mortar specimens before and after high temperature.
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Figure 12. Mechanical properties of GP mortar specimens in different curing conditions.
Figure 12. Mechanical properties of GP mortar specimens in different curing conditions.
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Figure 13. SEM micrographs for reference (0), X0.4 and V6 samples.
Figure 13. SEM micrographs for reference (0), X0.4 and V6 samples.
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Figure 14. EDS mapping images of reference (0), X0.4 and V6 samples.
Figure 14. EDS mapping images of reference (0), X0.4 and V6 samples.
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Figure 15. XRD patterns for reference (0), X0.4 and V6 samples.
Figure 15. XRD patterns for reference (0), X0.4 and V6 samples.
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Table 1. Chemical compositions of the binder materials.
Table 1. Chemical compositions of the binder materials.
Oxide (wt.%)SiO2Al2O3CaOFe2O3TiO2SO3K2OMgOOthers
FA50.5637.232.405.211.541.051.000.210.8
BFS31.1015.6841.750.461.423.240.285.180.89
Table 2. Chemical compositions of VAE and HPMC.
Table 2. Chemical compositions of VAE and HPMC.
Oxide (wt.%)SiO2CaOMgONa2OAl2O3Fe2O3SO3ClOthers
VAE44.4233.1816.292.67-1.150.610.421.26
HPMC2.384.24-15.961.340.6920.9054.360.13
Table 3. Mixture proportions of GP mortar samples (Weight ratio to binders (BFS + FA)).
Table 3. Mixture proportions of GP mortar samples (Weight ratio to binders (BFS + FA)).
FactorsSeriesBindersRiver SandWG: NHAAS/BindersAdmixtures (wt.,%)
FABFSHPMCVAE
Reference00.50.523:10.500
HPMCX0.20.50.523:10.50.2%0
X0.40.50.523:10.50.4%0
X0.60.50.523:10.50.6%0
VAEV20.50.523:10.502%
V40.50.523:10.504%
V60.50.523:10.506%
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MDPI and ACS Style

Ji, W.; Chen, P.; Lu, Y.; Zhang, Z.; Shan, B.; Li, S.; Chi, M.; Yu, H. Influence of HPMC and VAE on the Properties of Geopolymer Mortar. Buildings 2025, 15, 3621. https://doi.org/10.3390/buildings15193621

AMA Style

Ji W, Chen P, Lu Y, Zhang Z, Shan B, Li S, Chi M, Yu H. Influence of HPMC and VAE on the Properties of Geopolymer Mortar. Buildings. 2025; 15(19):3621. https://doi.org/10.3390/buildings15193621

Chicago/Turabian Style

Ji, Wenjun, Pengfei Chen, Ying Lu, Zeyang Zhang, Baolong Shan, Sha Li, Mengyan Chi, and Haifeng Yu. 2025. "Influence of HPMC and VAE on the Properties of Geopolymer Mortar" Buildings 15, no. 19: 3621. https://doi.org/10.3390/buildings15193621

APA Style

Ji, W., Chen, P., Lu, Y., Zhang, Z., Shan, B., Li, S., Chi, M., & Yu, H. (2025). Influence of HPMC and VAE on the Properties of Geopolymer Mortar. Buildings, 15(19), 3621. https://doi.org/10.3390/buildings15193621

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