Study on the effect of plant extracts as low carbon green admixtures on the performance of cement mortar

Abstract

The pollution of the environment by chemical admixtures for cement and concrete and the carbon emission in the production of cement and other concrete raw materials have attracted increasing attention from scholars. In order to improve the physical and mechanical properties of cement, eliminate pollution and reduce carbon emission, this paper uses natural plant extracts (cactus sativus extract and mulberry leaf extract) as admixtures to make cement mortar. The consistency, water absorption, compressive strength, flexural strength, chloride ion penetration resistance and microstructure of the mortar were tested and analyzed, the effects of different admixtures of natural plant extracts on the physical and mechanical properties of cement mortar were investigated. The results show that the consistency of the cement mortar was increasing with the increase of the admixture of cactus sativus extract and mulberry leaf extract; the admixture of cactus sativus extract and mulberry leaf extract did not change the hydration reaction and hydration products. When the admixture amount was lower, the extracts could promote the hydration reaction, improve the internal crystal morphology and generate more C-S-H, thus improving the physical and mechanical properties of cement mortar. The physical and mechanical properties of the cement mortar were optimized when the amount of mulberry leaf extract was 0.15% of the cement mass, and the overall performance was improved more compared with that of cactus extract. With the increase of amount of admixture, the viscosity of the system increases due to plant extracts, and the air bubbles formed during mortar mixing cannot be discharged and form micro-pores inside, resulting in the reduction of physical and mechanical properties. As a low carbon green admixture, plant extract is worthy of further research and promotion.