Functionalized Siloxane Coating as Protection of the Surface of Cement Composites Against Phototropic Colonization

Abstract

This article presents the concept of using a functionalised siloxane compound HOL9 with amphiphilic properties as a coating for cement composites to enhance their antifouling properties against algae. The biological properties of the compound were assessed based on its ability to inhibit chlorophyll fluorescence intensity, which is used as an indicator of photosynthetic activity and biofilm development. The greatest decrease in algal photosynthetic activity was observed for a 10% aqueous solution of HOL9 applied by painting. In these conditions, the maximum ^chlFI value decreased by 97.6%. In addition, the impact of the protective coating containing HOL9 on the fundamental physical and mechanical characteristics of the cement composite, along with its resilience to frost cycling, was thoroughly investigated. The coating applied by immersion demonstrated a 50.7% strength loss after 150 freeze-thaw cycles, while the coating applied by painting exhibited a 43.8% loss. In comparison, the control samples experienced a 42.8% strength reduction. It has been demonstrated that the method of application, the modifier concentration, and the type of solvent can have a substantial impact on the protective properties of concrete. The most marked inhibition of algae photosynthetic activity was observed with a 10% aqueous solution applied by painting.

Keywords: biofouling of concrete; protective coating for concrete; siloxane-based coating.

Scheme 1

Hydrosilylation of allyl ether BIKANOL9 with 1,1,1,3,5,5,5-heptamethyltrisiloxane.

Figure 1

GPC results of HOL9 product.

Figure 2

TGA results of HOL9 product.

Figure 3

Changes in ^chlFI in microalgal cells growing for 21 days on cement composite coated by painting or dipping, in two concentrations of HOL9 compound, i.e., 5% and 10% in alcohol or water solutions. *** p < 0.001.

Figure 4

Changes in ^chlFI in microalgal cells growing for 21 days on cement composite between control (A) and samples covered by the tested compound HOL9 in 5% concentration. (B,C) HOL9 in alcohol solution by dipping (B) and painting (C). (D,E) HOL9 in water solution by dipping (D) and painting (E).

Figure 5

Changes in ^chlFI in microalgal cells growing for 21 days on cement composite between control (A) and samples covered by the tested compound HOL9 in 10% concentration. (B,C) HOL9 in alcohol solution by dipping (B) and painting (C). (D,E) HOL9 in water solution by dipping (D) and painting (E).

Figure 6

SEM images of cement composites samples with HOL9 modification: from 5% alcohol solution deposited by painting (A) and dipping (C), and from 5% water solution deposited by painting (B) and dipping (D), and from 10% alcohol solution deposited by painting (E) and dipping (G), and from 10% water solution deposited by painting (F) and dipping (H). Scale bars are 200 µm.

Figure 7

SEM images of cement composite samples with HOL9 modification: from 5% alcohol solution deposited by painting (A) and dipping (C), and from 5% water solution deposited by painting (B) and dipping (D), and from 10% alcohol solution deposited by painting (E) and dipping (G), and from 10% water solution deposited by painting (F) and dipping (H). Scale bars are 10 µm.

Figure 8

The effect of ageing on substrates modified by painting with either a 10% alcohol solution (A,B) or an water solution (C,D) is shown. The scale bar is 50 µm for (A,B), and 10 µm for (A1–D1).