Mechanical and durability assessment of cement-based and alkali-activated coating mortars in an aggressive marine environment

Abstract

Coatings are used as practical solutions against the intrusion of corrosive ions into concrete structures, particularly, in the harsh marine environment. In the present study, the effectiveness of using cement-based and geopolymer-based coatings produced using by-product materials has been evaluated. Silica fume and GGBFS at their optimum dosages were incorporated into mortar mixtures as a cement replacement, and mixtures of NaOH or KOH and sodium silicate solutions were used in the alkali-activated mortars. Shrinkage test, RCMT, and capillary absorption test as common experiments for durability analysis, as well as tests related to the mechanical and bonding properties including compressive strength test, pull-off test, and shear bonding strength test were carried out on the specimens. According to the results, both geopolymer and cement-based mortars improved the compressive and bonding strengths, and chloride diffusion resistance of coatings compared to the OPC mortar. Silica fume was found to be more effective in the strength development of mortars at young ages, while GGBFS was more responsible for acting as a filler and producing further gel in the older ages. The major drawback with geopolymer mortars is the high rate of water absorption and shrinkage coefficient in the early hours, which shows the importance of curing of these mortars at young ages. Overall, the mix design produced with 30% GGBFS and 7.5% silica fume showed the highest durability and mechanical properties and proved to be more compatible with the harsh environment of the Persian Gulf.

Geopolymers as Sustainable Material for Strengthening and Restoring Unreinforced Masonry Structures: A Review

“…The bond strength between the substrate concrete and the geopolymer matrix is also important if it is to be used as a strengthening or repair material [100]. Lashkari et al [101] presented the investigation of geopolymer-based coating exposed to harsh environments along the Persian Gulf. It is reported that slag in geopolymer exposed to such environments has better ability to fill voids, which influences the lower effect of chloride ions.…”

“…Reinforcing with fibers helps in controlling the drying shrinkage of geopolymers [101]. Guo et al [113] mentioned that the incorporation of fibers in geopolymers could also reduce cracks.…”

A Study of Alkali-Activated Coatings Durability Assessment in Different Environments

“…In concrete structures, to prevent the concrete from the intrusion of corrosive ion coatings was used as a practical solution. Lashkari et al [21] have evaluated the effectiveness of utilizing geopolymer and cementbased coatings created using materials from the waste by-products. In alkali-activated mortars, the mixtures of sodium silicate, and potassium hydroxide (KOH) and sodium hydroxide (NaOH) were utilized.…”

A Superhydrophobic Alkali Activated Materials Coating by Facile Preparation

“…Nicoleta [24] prepared and tested fireproof inorganic coatings based on sodium silicate solution with intumescent additions, which sensibly reduced the rate of temperature increase (up to 75%) in the steel substrate. Salar Lashkari [25] found AAMs have shown better performance compared to cement-based mortars by evaluating the durability characteristics and mechanical properties of AAMs and cement-based coating mortars in the harsh environment of the Persian Gulf. Thus, the utilize of alkali activated materials coatings would minimize the accumulation of solid waste, those were defined as a sustainable material depend on economical and environmentally friendly [20][21][22].…”