Durability performance of cement mortar incorporating water-repellent admixtures

초록

Cement-based concrete and mortar materials, characterized by their hydrophilic and porous structure, are prone to water and hostile ion penetration, which significantly undermines their durability. The incorporation of waterrepellent admixtures can enhance the overall performance of these materials in terms of water repellency. This study focuses on improving the water-repellent properties of mortars and concretes manufactured with various hydrophobic chemical admixtures. To ordinary Portland cement (OPC) mortars, the following additives were introduced: triethoxysiloxane or amorphous silica (Sitren (R) P 750), along with calcium, zinc, aluminum, and barium stearate products in powder form. The objective was to develop bulk water-repellent mortars suitable for building protection, resistant to the deteriorating effects of water, and adaptable for various construction applications. The influence of these admixtures on the hydration and structure of the mortars was evaluated using X-ray diffraction and Fourier-transform infrared spectroscopy. Various techniques and methodologies, such as mercury intrusion porosimetry, water absorption tests (both capillary and boiling water absorption tests, and rapid chloride permeability tests were employed to establish the effectiveness of these compounds against water. Furthermore, the resistance of water-repellent mortars to salt crystallization was assessed. The study found that all water-repellent admixtures provided adequate protection, though the specific compounds and their dosages altered some physical properties and hydration kinetics. Compared to OPC, these admixtures increased capillary water absorption capacity such as the water absorption coefficient of calcium stearate 1 % is 0.0003 and 0.0002 at 28 and 56 days respectively water absorption (boiling) test results of sitren 1 %,1.5 %, and aluminum 1.5 % are 7.32 7.096, 4.83 % respectively. Moreover, microstructure test results indicate the presence of C-S-H, portlandite and so on. The primary indicator of effectiveness was the durability performance of the water-repellent admixtures when combined with OPC. Additionally, the study elucidates the interfacial precipitation of hydration products. A crucial aspect is determining the optimal mixture ratio that offers repellence properties for both building technology and cost-effectiveness.

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