Moisture-retaining film-forming compounds for cement concrete pavements in arid climates

2.1. Reference curing compounds

To evaluate the effectiveness of the proposed approach, three existing formulations were analyzed:

– T1: A latex-based compound comprising styrene-butadiene (divinylstyrene) latex, solid hydrocarbons, lanolin production waste, and calcined soda. Experimental evaluation revealed its insufficient efficiency in preventing surface microcracks under extreme plastic shrinkage [10, 13].

– T2: An improved conventional compound incorporating oil dewaxing by-products and plasticizers. Despite better performance, T2 exhibits high viscosity at lower temperatures, complicating field application in spring and autumn.

– T3 (Prototype): A multi-component analogue based on latex and solid paraffin (Patent RU 2455265) [12]. While functional, its high cost and insufficient film-formation speed under arid conditions limit its practical use.

2.2. Development of the optimized GACH-3 based composition

The proposed composition was designed to eliminate the shortcomings of the prototype by utilizing secondary industrial resources. The optimized formulation, designated as Composition 2, is detailed in Table 1.

The rationale for the selected components is as follows:

– GACH-3: A petroleum refining by-product used as the primary paraffin-based hydrophobic agent. It reduces film formation time and enhances reflectivity.

– Mineral oil I-20: Acts as a solvent to ensure the complete dissolution of GACH-3 and promotes penetration into the concrete matrix. Increasing the concentration above 2.5 % is avoided due to a decrease in the solubility parameter.

– Hypan-0.7: A polymer component introduced to improve the mechanical resistance and elasticity of the protective layer.

– Silicon dioxide: Regulates viscosity and stabilizes the system; contents above 1 % may lead to agglomeration.

– Technical oleic acid: Functions as an emulsifier that promotes pore colmatation and stabilizes the system.

2.3. Physicochemical interaction mechanism

The high moisture-retention capacity of the proposed system is achieved through a synergistic “barrier and seal” effect. The GACH-3 component forms a continuous hydrophobic surface film that physically blocks the evaporation path. Simultaneously, the technical oleic acid interacts with the $C{a}^{2+}$ ions in the fresh cement concrete pore solution to form insoluble calcium soaps. These soaps, acting in tandem with silicon dioxide micro-fillers, effectively colmate (seal) the capillary pores. This multi-level barrier ensures that the internal moisture remains available for continuous cement hydration [5, 6] even under extreme thermal radiation [11].

2.4. Preparation and application procedure

The preparation process involves heating the water to 60 °C, followed by the sequential addition of GACH-3, used mineral oil I-20, technical oleic acid, and Hypan-0.7 under continuous stirring. Silicon dioxide is then introduced to adjust the viscosity and stabilize the emulsion. The resulting homogeneous emulsion is applied by spraying at a recommended rate of 300-350 g/m² [3, 4, 14]. Film formation begins within 30 minutes and is fully completed within 3 hours at (20±2) °C. The recommended application temperature range for the concrete surface is from +2°C to +45°C. All concrete specimens were cast and tested in accordance with GOST 10180-2012 [1] and GOST 12730.3-2020 [2].

3.1. Optimization of the composition

Initially, six formulations were tested to determine the optimal component ratio. The physical and mechanical properties of the treated specimens are summarized in Table 2.

Analysis of Table 2 indicates that Composition 2 (20.0 % GACH-3) achieves the highest performance metrics. To address the requirement for experimental analysis, these data were visualized to establish variable correlations.

Fig. 1Correlation analysis between GACH-3 content, compressive strength, and moisture evaporation

As shown in Fig. 1, a parabolic relationship exists between GACH-3 content and compressive strength, with a clear optimum at 20 wt. %. Beyond this point, the increase in hydrophobic components leads to a slowdown in strength gain. The inverse linear correlation between strength and evaporation rates confirms the “barrier and seal” hypothesis: by minimizing moisture loss (4.3 %), the composition ensures the necessary hydration degree for the cement matrix.

3.2. Comparative performance

Based on the optimization, Composition 2 was compared against water curing (control) and the T3 prototype [12].

As demonstrated in Table 3, the proposed composition increased compressive strength by 35.1 % and flexural tensile strength by 72.9 % compared to water-cured samples. Moisture evaporation was reduced twofold relative to the T3 prototype, which was developed based on the existing multi-component technology. This significant improvement is attributed to the physicochemical mechanism described in Section 2.3: the formation of insoluble calcium soaps, which effectively colmates the pores [10, 13].

3.3. Long-term durability and microstructure

To assess long-term reliability, specimens were analyzed 12 months after application [14].

The data in Table 4 show that the treatment leads to a significantly denser microstructure [5, 6]. Porosity was reduced to 1.5-2 %, and microcrack sizes were minimized to 1.5-2 μm. These results confirm that early-age moisture conservation promotes a more refined and dense C-S-H gel structure, significantly enhancing durability under arid climatic conditions [11].