Crystal-Chemical and Thermal Properties of Decorative Cement Composites

The advanced tendencies in building materials development are related to the design of cement composites with a reduced amount of Portland cement, contributing to reduced CO2 emissions, sustainable development of used non-renewal raw materials, and decreased energy consumption. This work deals with water cured for 28 and 120 days cement composites: Sample A—reference (white Portland cement + sand + water); Sample B—white Portland cement + marble powder + water; and Sample C white Portland cement + marble powder + polycarboxylate-based water reducer + water. By powder X-ray diffraction and FTIR spectroscopy, the redistribution of CO32−, SO42−, SiO44−, AlO45−, and OH− (as O-H bond in structural OH− anions and O-H bond belonging to crystal bonded water molecules) from raw minerals to newly formed minerals have been studied, and the scheme of samples hydration has been defined. By thermal analysis, the ranges of the sample’s decomposition mechanisms were distinct: dehydration, dehydroxylation, decarbonation, and desulphuration. Using mass spectroscopic analysis of evolving gases during thermal analysis, the reaction mechanism of samples thermal decomposition has been determined. These results have both practical (architecture and construction) and fundamental (study of archaeological artifacts as ancient mortars) applications.

The Influence of Water/Binder Ratio on the Mechanical Properties of Lime-Based Mortars with White Portland Cement

Protecting the built cultural heritage is one of the most important tasks in architectural practice. The process of repair is time-consuming, weather-dependent, and sensitive to materials applied. Introducing new materials in historic building repair in order to decrease the time needed for repair, brings some risk in the preservation process. The most common material for masonry repair is lime mortar. Adding cement to lime mortar can improve the mechanical properties of mortar and speed up the repair process. The high amount of cement may increase the strength, but decrease ductility and permeability of mortar, causing damages to protected buildings. An increase in strength with the smallest amounts of cement demands optimization of water content in the mixture. Tests were performed to investigate the influence of the water/binder (w/b = water/(lime + cement) ratio on mortar strength and water permeability. An air-entraining agent (AEG) was introduced to improve permeability. Results confirmed that adding small amounts of cement to lime (20% by weight) and decreasing of w/b ratio, improves the strength, with almost negligible influence on water permeability. The addition of very small amounts of AEG did not decrease the strength, nor the permeability.

Properties of Cement with Photocatalytic Composite Material

The paper presents the results of the determination of the effect of a photocatalytic composite material (PCM) with the composition SiO2‒TiO2 on the main properties of white Portland cement: heat release during hydration, phase composition and microstructural features of cement stone, pressure strength and self-cleaning ability. PCM was synthesized by a sol-gel method based on tetrabutoxytitanium and finely dispersed diatomite powder and 15% cement was added instead. The presence of PCM in the cement system provided the reduction of the induction period of cement hydration, consolidation of the microstructure of the cement stone with the products of the pozzolanic reaction, the ability to photocatalytic self-cleaning of the cement stone surface.

Effect of Grey and White Portland Cement Fillers on Flexural and Shear Strength of GFRP Composite Material

The mechanical behaviour of glass fiber reinforced polymer (GFRP) composite depends on the type of matrix, filler, and fiber architecture. In order to develop high-strength polymer matrix composites, the composites containing 5%, 10%, and 15% each of Portland grey and white cement filler are prepared by uniformly mixing the epoxy and filler materials, followed by casting by hand layup technique. The flexural and shear test is performed in accordance with ASTM 790 and ASTM D5379, respectively. It has been found that the values of shear strength, flexural strength, and modulus of elasticity vary with the increasing amount of cement component in the polymer. In addition, for a given percentage of the components of the cementitious filler, the values of the mechanical strength of the composites that contain white cement are higher than those of the composites that contain grey cement filler. Damage to composites has been found to involve fiber breakage and delamination primarily.

DEPENDENCE OF WHITENESS OF DECORATIVE SLAG-ALKALINE CEMENT FROM THE CHEMICAL COMPOSITION OF BLAST-FURNACE SLAGS

The construction industry is demanding more and more quality decorative cements. The demand for them and the requirements for their performance are constantly growing. But since decorative cements are based on white Portland cement, their production is associated with the disadvantages of the production of all clinker cements  low environmental friendliness, high energy consumption and high prices. They are not always able to provide decorative ecological and comfortable coatings with increased performance. In addition, many countries do not produce it and have to import it. An effective alternative to decorative clinker cements can be decorative slag-alkaline cement obtained from industrial waste. It also provides a number of special properties  a wide range of colors, color fastness, high strength, high adhesion, durability and many others. But the problem associated with the use of slag-alkaline cements as decorative cements with high linen ( 70%) is the unstable chemical composition of the slag and, first of all, the different presence of iron oxides in it. It is shown that the presence of iron oxides can reduce the whiteness of decorative slag-alkaline cements due to the synthesis of compounds in them, which give the samples of blue-green color and due to the presence of iron oxides proper, which are inherent in color from brown to dark brown. The paper shows the regularities of the influence of the chemical composition of blast-furnace slags on the whiteness of an artificial slag-alkaline stone. Possibilities of obtaining decorative alkali-activated cements with a wide range of whiteness  from 70 to 97% are shown. Methods of reducing the cost of slag-alkaline decorative cements by using a complex bleaching additive, where part of the expensive TiO2 can be replaced by kaolin or CaCO3, are shown. A new method for determining the whiteness of hardened materials is proposed.