Investigating the potential of trass-cement binary blend for enhancing microscopic properties, macroscopic performance, and sustainability of cement paste

Abstract

• Effects of trass on micro- and macro-level properties of cement paste were evaluated. • Blending cement with trass accelerated the C 3 S and C 3 A hydration. • Higher nonevaporable water contents were detected in blended sample compared to plain one. • The values of compressive strength activity index fluctuated between 106.7 and 124.6%. • Incorporating trass into cement can lead to a cleaner, cheaper, and less energy consumer construction. Due to some physical or chemical incompatibility issues between supplementary cementitious materials (SCMs) and cement, it is necessary to investigate the microscopic properties and macroscopic performance of cement composites containing such blends before their incorporation in construction. Hence, in this study, the hydration kinetics, degree of hydration, microstructural morphology, and pore structure of cement paste blended with trass, as well as its mechanical and transport properties, were profoundly evaluated. Moreover, the potential of trass for enhancing the sustainability of construction was also assessed. The physical properties of trass accelerated the C 3 S hydration, while its chemical composition led to the reduction of induction period, in addition to the acceleration of C 3 A hydration. Significant refinement of pore structure characteristics was found in blended sample after 90 days, when the threshold and critical pore diameters were reduced by respectively 27.7 % and 10.7 %, compared to those of the plain sample. This denser microstructure was reflected in superior electrical resistivity of the blended sample, which was 2.1 times of the plain one at 90 days. Furthermore, the inclusion of trass through refining the morphology of CH crystals in the microstructure, besides lowering the calcium hydroxide (CH) content by 12.1–63.3 % and increasing the nonevaporable water content by 2.1–8.0 %, led to 6.7–24.6 % higher compressive strengths in blended sample. Regarding the sustainability, at a similar 90-day compressive strength of 40 MPa, using trass results in an approximately 21.7 % less energy consumer, 20.3 % cleaner, and 15.8 % cheaper construction. Moreover, at equal levels of energy consumption or CO 2 emission, the blended sample has greater compressive strength and electrical resistivity than the plain one, which can be indicative of an extended service life. Accordingly, the utilization of trass is recommended since it has the potential to improve the sustainability both directly and indirectly.