Mechanical Properties and Microstructure of Rice Husk Ash–Rubber–Fiber Concrete under Hygrothermal Environment

Abstract

In order to study the mechanical properties of rice husk ash–rubber–fiber concrete (RRFC) under hygrothermal environment, the optimal group was selected by orthogonal test. The mass loss, relative dynamic elastic modulus analysis, strength analysis, degradation degree analysis after cyclic loading and internal microstructure analysis of the optimal group of RRFC samples after dry–wet cycles under different environments and temperatures were compared and analyzed. The results show that the large specific surface area of rice husk ash optimizes the particle size distribution of RRFC specimens, reacts to form C-S-H gel, enhances the compactness of concrete, and forms a dense structure as a whole. The presence of rubber particles and PVA fibers effectively improves the mechanical properties and fatigue resistance of RRFC. The comprehensive mechanical properties of RRFC with rubber particle size of 1–3 mm, PVA fiber content of 1.2 kg·m−3 and rice husk ash content of 15% are the best. The compressive strength of the specimens after dry–wet cycles in different environments generally increased first and then decreased, reaching a peak at the seventh dry–wet cycle, and the compressive strength of the specimens under chloride salt solution decreased more than that under clear water solution. Thes provided new concrete materials for the construction of highways and tunnels in coastal areas. Under the premise of ensuring the strength and durability of concrete, it is of great practical significance to explore new roads for energy conservation and emission reduction.

Influence of Sunflower Seed Husks Ash on the Structure Formation and Properties of Cement Concrete

“…The issue of using ash from these wastes in cement concrete technology and its effectiveness has been quite well studied, which is confirmed by various studies [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. For example, in Salas Montoya et al (2023) [9] study, "the application of rice husk ash as a substitution of a part of the Portland cement" provided a fairly significant rise in strength properties, namely over 20% compared to the reference prototype.…”

“…In Rani & Jaya Krishna (2022) [15] study, the use of rice straw ash in an amount of 10% also improved "the compressive strength by 23.21% and tensile strength by 28.25% compared to the control composition". Studies [16][17][18][19][20] have confirmed the positive impact of rice husk and straw ash on the quality characteristics of composites in concrete technology.…”

“…At SSHA dosages of more than 12%, a negative effect was observed, and the drop in strength values at SSHA amounts of 14% and 16% were 4.96% and 8.51%, respectively. As is known, the complex use of organic and inorganic compounds as additives in concrete technology with rationally selected dosages can have a significant impact on the processes of formation of the structure of hardened cement paste and, as a result, lead to an improvement in physical and mechanical properties [18,57]. In general, an increase in the compressive strength of concrete modified with a complex organomineral modifier, namely: SSHA in an amount from 2% to 12% instead of part of the cement, microsilica in an amount of 4% by weight of the binder and a poly carboxylate-based plasticizer in an amount of 1.5% by weight of the binder, can be explained by the following two factors.…”

“…The concentration of CaO in the liquid phase of the concrete system becomes too high, and this already has a negative effect on the emerging structure of the concrete composite. The amount of low-basic calcium hydrosilicates of the CSH(I) type decreases, and the amount of CSH(II), on the contrary, increases [18,26,57].…”

“…The introduction of the SSHA additive to replace part of the cement in an amount from 2% to 12%, as well as microsilica and a plasticizer, helps improve the structure of the concrete composite by changing its phase composition and reducing capillary porosity. The content of oxides such as SiO2, Al2O3, CaO in the composition of SSHA and microsilica and the degree of their dispersion determine the structure quality of the concrete composite and its final physical and mechanical properties, including water absorption [18,57]. The main factor influencing capillary porosity is effectiveness in the interaction of the plasticizer with the SSHA particles.…”