The Development of Photoactive Admixtures for Concrete and Cement-Based Plaster Finishes, to Create Self-Cleaning Surfaces

This article presents research and development on innovative photoactive admixtures for concrete and cement-based plasters for the finishing of concrete surfaces finished this year. The goal of the development was to provide the resulting surfaces of these newly developed materials with a self-cleaning ability stemming from photocatalytic reaction during exposure to UV radiation. The specific function of all these products is based on the photocatalytic oxidative mineralization of all organic structures present on the surface, i.e., their gradual transformation into the final simple inorganic compounds, which are carbon dioxide, water and the corresponding mineral acids. This research and development was carried out as part of a project supported by the Czech Ministry of Industry and Trade, in the TRIO programme; and in cooperation of BETOSAN s.r.o., the Technical University of Liberec, the Institute of Inorganic Chemistry of the Czech Academy of Sciences and the J. Heyrovsky Institute of Physical Chemistry of the Czech Academy of Sciences. The first type of developed material is a photocatalytically active admixture in powder form, allowing the preparation of concrete surfaces with photocatalytic properties. The second type of developed material is a photocatalytically active cement-based plaster, intended primarily for application to a concrete substrate. Two final versions of both materials were developed. In the case of the plaster this means preparation of two colour variants, specifically white and grey. For the powder concrete admixture two types with different application procedures were developed. This means one version of admixture mixed throughout the entire volume of the concrete and second variant applied only in the surface layer of the concrete. We anticipate mainly exterior applications on the self-cleaning outer shell of buildings, as well as treatment of the surface layer of various structures such as bridges, noise barriers, traffic barriers and tunnels. The developed materials can also be used in interiors under specific conditions, with anticipated uses in the health care and food processing industries.

Development of Innovative Photoactive Admixtures for Concrete and Cement-Based Plaster Finishes, to Create Self-Cleaning Surfaces

This article presents research and development on innovative photoactive admixtures for concrete and cement-based plasters for the finishing of concrete surfaces. The goal is to provide the resulting surfaces of these newly developed materials with a self-cleaning ability stemming from photocatalytic reaction during exposure to UV radiation. This research and development is currently underway as part of a project supported by the Czech Ministry of Industry and Trade, in the TRIO programme; and in cooperation with BETOSAN s.r.o., the Technical University of Liberec, the Institute of Inorganic chemistry of the Czech Academy of Sciences and the J. Heyrovsky Institute of Physical Chemistry of the Czech Academy of Sciences. The first type of material under development is a photocatalytically active admixture in powder form, allowing the preparation of concrete surfaces with photocatalytic properties. The second type of material under development is a photocatalytically active cement-based plaster, intended primarily for application to a concrete substrate. The preparation of two or more final versions is to be expected for both types of materials. In the case of the plaster this includes the preparation of two colour variants, specifically white and grey. For the powdered cement admixture we expect the preparation of various types based on their application. This could mean different types of admixtures mixed throughout the entire volume of the concrete or only in the surface layer of the concrete. We envisage exterior applications on the self-cleaning outer shell of buildings, as well as treatment of the surface layer of various structures such as bridges, noise barriers, traffic barriers and tunnels. The materials created could also be used in interiors under specific conditions, with anticipated uses in the health care and food processing industries.

Study on the Influence of Calcined Underground Ant Nest Powder on the Durability of Concrete

Ants have strict requirements on the building materials of the nest, such as the size, weight, luster and color of soil particles. The soil of underground ant nests is composed of clay particles cemented together to form a hard brick-like material. The ant nest powder shows pozzolanic activity after calcination, which can meet the requirements for active admixture of concrete. Under the standard curing condition, the influence of calcined ant nest clay powder (CANCP) on the durability of concrete is evaluated by chloride penetration resistance, carbonization resistance and freeze–thaw resistance, and the influence of the powder content is investigated. The results show that when the content of CANCP is less than 10%, the chloride penetration resistance of concrete increases with content of CANCP. In the early stage of carbonation, the greater the content of CANCP, the higher the carbonization rate of concrete. In the middle and later stage of carbonation, the carbonation rate of CANCP concrete is significantly lower than that in the early stage, and the carbonation depth is linearly related to the carbonation time. When the content of CANCP is less than 20%, the freeze–thaw resistance of CANCP concrete is better than that of the reference concrete.

Development of the HVFAC Modulus of Elasticity

Concretes with high fly ash content are within a unified world nomenclature often referred to as HVFAC, resp. high volume fly ash concrete. These concretes are characterized by the percentage of fly ash as an active admixture relative to a cement dose of at least in a ratio of 1:1. The use of these concretes falls into the field of construction with the necessary reduction in the development of hydration heat. In the experiment, long-term monitoring of the development of important mechanical parameters, namely the static modulus of compressive elasticity and compressive strength, was performed. Both monitored parameters play a very important role in the design of buildings, for which construction is HVFAC often used. These parameters were monitored within the carried out research until the time of 360 days. The results of the experiment give an overview of the pozzolanic reaction progress over the in the long-term time horizon and its impact on the concrete parameters monitored. The results clearly show that even after 360 days the development of the strength parameters of these concretes is not stopped.

Influence of Wood-Based Biomass Ash Admixing on the Structural, Mechanical, Hygric, and Thermal Properties of Air Lime Mortars

Mechanically-activated wood-based biomass ash (WBA) was studied as a potential active admixture for design of a novel lime-pozzolan-based mortar for renovation purposes. The replacement ratio of lime hydrate in a mortar mix composition was 5%, 10%, and 15% by mass. The water/binder ratio and the sand/binder ratio were kept constant for all examined mortar mixes. Both binder constituents were characterized by their powder density, specific density, BET (Brunauer–Emmett–Teller), and Blaine specific surfaces. Their chemical composition was measured by X-ray fluorescence analysis (XRF) and mineralogical analysis was performed using X-ray diffraction (XRD). Morphology of WBA was investigated by scanning electron microscopy (SEM) and element mapping was performed using an energy dispersive spectroscopy (EDS) analyzer. The pozzolanic activity of WBA was tested by the Chapelle test and assessment of the Portlandite content used simultaneous thermal analysis (STA). For the hardened mortar samples, a complete set of structural, mechanical, hygric, and thermal parameters was experimentally determined. The mortars with WBA admixing yielded similar or better functional properties than those obtained for traditional pure lime-based plaster, pointing to their presumed application as rendering and walling renovation mortars. As the Chapelle test, STA, and mechanical test proved high pozzolanity of WBA, it was classified as an alternative eco-efficient low-cost pozzolan for use in lime blend-based building materials. The savings in CO2 emissions and energy by the use of WBA as a partial lime hydrate substitute in mortar composition were also highly appreciated with respect to the sustainability of the construction industry.

The Properties of Polymer-Modified Mortars Using Pozzolana Active Admixtures

The paper focuses on the changes in properties of cement and polymer-modified cement mortars when pozzolana-active admixture are added into the mixture. Natural and artificial pozzolans based on amorphous and mineral silicon dioxide were used. In order to explain the results obtained from the experiment and to gain new insights about the microstructure of the mixtures, equipment such as SEM sampling, RDA analysis, DTA and high-pressure mercury intrusion porosimetry were used.

Experimental Study on Anti-Permeability of Active Admixture Recycled-Concrete

Active admixture recycled-concrete (AARC) is one of green high performance concretes, which took active admixture and fly ash into recycled concrete to replace part of cement. This paper researches the relationship of seepage resistance grade and chloride diffusion coefficient of recycled concrete by the regressive analysis of experimental data from NEL and gradually pressure method. The mufti-factor (slag powder, fly ash, air-entraining agent, polypropylene fiber, recycled coarse aggregate) and multi-level experiments of anti-permeability of concrete were carried out by orthogonal experiment method, and the optimum proportion of concrete is determined. The results show that seepage resistance grade of 16 groups AARC all reached W13, and chloride diffusion coefficient was between 0.5~1×10-8cm2/s, the permeability grade is IV. The impermeability of the AARC is excellent. The rate of recycled coarse aggregate and slag powder were the most important factors for the impermeability properties of concrete, the optimum proportion of concrete was 10% slag powder, 20% fly ash, 1/10000 air-entraining agent, 1.0 kg/m3 polypropylene fiber and 40% recycled coarse aggregate.

Microstructure and Properties of High Performance Concrete with Steel Slag Powder

As an active admixture, super fine steel slag powder can be mixed into concrete to produce high performance concrete. The microstructures between cement paste mixed with steel slag powder and plain cement paste are experimentally studied. The SEM of the microstructures shows that microstructure of cement paste are changed by active mineral admixture, the internal structure of the cement paste are improved. Drying shrinkage of cement mortar with different steel slag kinds and different dosage of admixtures are measured. Experiments results show the effect of steel slag powder on drying shrinkage of cement mortar.