In order to improve the mechanical properties of HA/PEEK composite, the surface modification of nanosized hydroxyapatite (n-HA) was carried out with silane coupling agent (SCA).The modified particles were produced using different contents of SCA (KH560) and characterized by virtue of Fourier Transform Infrared (FT-IR) spectroscopy. The polyetheretherketone (PEEK) nanocomposite materials reinforced by surface-modified n-HA were successfully prepared and their microstructure and mechanical properties were examined by scanning electron microscopy (SEM), Instron IX Material Testing System and Vickers micro-hardness tester. The result of FT-IR indicated that the nanosized HA was coupled with the SCA by a chemical bonding. SEM observation showed that SCA-HA was well-dispersed in PEEK matrix. The results incicated that mechanical strength of SCA-HA/PEEK composite was improved and best at 5 vol.% HA, 3wt.% SCA.Keywords: nanosized hydroxyapatite; Silane couping agent; Polyetheretherketone; Biocomposite; Mechanical propertity

Less than half a century ago just an idea of presence of free alkalis in a ceramic matrix was considered by ordinary Portland cement people as an absurd one and this was a basic postulate accepted in chemistry of cements. In 1957 a scientist from Ukraine (USSR) Viktor Glukhovsky put forward an assumption which was taken as a base for development and bringing into practice of construction a principally new class of cementitious materials which first appeared in the field under a name of alkaline (now also known under a general name of alkali-activated) cementitious materials. A validity of these ideas was confirmed by more than 50 years of evolutional development and vast experience collected on practical use of new materials in different applications. The paper covers theoretical views on role played by alkali in the formation of an alkali-activated cement matrix with high durability. Examples of compositional build-up of the alkali-activated cementitious materials vs. quantity of added alkali and type of aluminosilicate component are reported together with results of 50-year experience obtained from observation of concrete structures made from these cements.

The contribution covers results of studies on the alkali-activated cement concretes intended for marine engineering applications. Such properties as strength, wear, corrosion, freeze-thaw, weather resistance and many others have been studied, and the results are reported and discussed in detail. The obtained results suggested to draw a conclusion on high potential of the alkali-activated cement concretes for marine engineering applications, since in their performance properties these concretes are highly advantageous over other concretes used as marine concretes and big savings can be expected in the future due to the longer span of service life. The results are supported by long-term observations in real conditions. The above advantages are attributed to more perfect micro-and macrostructure of the alkali-activated cement stone. The authors have summarized their own experience and results collected by PhD and DSc students under their supervision dedicated to assessment of durability of these concretes, in particular, for marine engineering applications. In order to bring these advanced materials into practice of construction worldwide, two rilem (International Union of Laboratories and Experts in Construction Materials, Systems and Structures) committees have been founded: "Alkali-activated Materials" (2010-2013) and "Durability Testing of Alkali Activated Materials" (2013-ongoing).

There are shown studies on development of the alkali-activated slag cements and concretes using Chinese raw materials. Such cements and concretes are able to provide high performance characteristics of materials and constructions under exposure of sea climate. The tests had been done for compliance with the requirements set in the national standards of P.R.China and were determined characteristics of strength, wet conditions shrinkage, freeze-thaw resistance, corrosion and weather resistance, biodegradability, water permeability, bond strength between concrete and reinforcement. The obtained positive results of tests allowed to recommend them for a pilot-scale production of the developed materials in sea construction for protection of the sea coastal line in the P.R.China.

The paper covers the results of studies of the alkali activated slag cement concretes from the cements prepared under all-in-one technology to meet the requirements for concretes for marine engineering application. The compressive strength, weather resistance, biodegradability, bonding strength with steel reinforcement bar, steel reinforcement bar protection, chlorine ions diffusion parameters and resistance to corrosive exposure of 5% Na2SO4 solution were tested, which exhibit that alkali activated slag cement and concretes are very suitable for marine engineering applications.