Carbonation of concrete cover of reinforcement as a cause of loss of durability of structures

The article discusses the physical and chemical mechanisms of the carbonation phenomenon itself, as well as points out the synergistic effect of frost destruction and concrete carbonation on reinforced concrete elements. Examples of structural damage from engineering practice in the diagnosis of reinforced concrete structures are presented. Two cases of frost and carbonation damage of precast reinforced concrete elements are analyzed. It was noted that the most common cause of damage to concrete structures is the lack of frost resistance. Carbonation of concrete leads to deprivation of the protective properties of the concrete lagging against the reinforcing steel. The examples cited include precast elements that, for technical reasons, had a relatively small lagging thickness. The first one relates to the thin walled elevation elements, which are exploited during 60 years and the second relates to the energetic poles with very advanced concrete corrosion damage. The examples given of corrosion of concrete and reinforcement of elements indicate that synergistic environmental interactions can intensify the destruction of elements

Współczesne domieszki uszczelniające i wspomagające samozaleczanie betonu

Szczelność betonu jest jedną z właściwości warunkujących jego trwałość. W artykule przedstawiono możliwości zapewnienia szczelności betonu przez tzw. domieszki krystaliczne, których dodatkową funkcją może być wspomaganie samozaleczania betonu - krok w kierunku materiałów autotechnologicznych.Tightness of concrete is one of the properties affecting its durability. Possibilities of ensuring the concretes tightness by using of crystalline admixtures are presented in the paper. Their additional function can be supporting of concrete self-healing - a step toward auto-technological materials

Polymer-Cement Composites Containing Waste Perlite Powder

Polymer-cement composites (PCCs) are materials in which the polymer and mineral binder create an interpenetrating network and co-operate, significantly improving the performance of the material. On the other hand, the need for the utilization of waste materials is a demand of sustainable construction. Various mineral powders, such as fly ash or blast-furnace slag, are successfully used for the production of cement and concrete. This paper deals with the use of perlite powder, which is a burdensome waste from the process of thermal expansion of the raw perlite, as a component of PCCs. The results of the testing of the mechanical properties of the composite and some microscopic observations are presented, indicating that there is a possibility to rationally and efficiently utilize waste perlite powder as a component of the PCC. This would lead to creating a new type of building material that successfully meets the requirements of sustainable construction

Chemical corrosion of concrete tank in sewage treatment plant as the cause of failure

The organoleptic examination proves a significant degree of structural disintegration of concrete - some loosely embedded aggregate grains easily fall out when touched. The vertical range of the above changes includes a zone up to approx. 60 cm above the wastewater level, i.e. thea zone of fluctuations in the level of wastewater and a spray-gas zone. In the case of the tank 01/1 this means the full usable height of the tank, which may mean in the longer term the propagation of damage to the lower surface of the roof

Wstępna ocena możliwości zastosowania odpadowego pyłu perlitowego w budowlanych kompozytach polimerowych

The paper deals with possibility of use of waste perlite powder as a microfiller in the building polymer composites. The perlite powder influences the technological properties of the polymer mixes, while the mechanical properties of the hardened composite are not significantly affected. The obtained results confirm the possibility of rational use of the waste material, which is in agreement with the rules of the sustainable development in construction. Till now, 5 % (by mass) of conventional microfiller in the polyester composite have been successfully substituted by perlite powder, which means the utilization of  large amounts of this waste, due to its low bulk density (< 100 kg/m3). The authors will attempt to increase the degree of substitution. However, it will require resolving some technological problems involved particularly with the deterioration of the polymer mixes workability by the addition of the perlite powder.W artykule przedstawiono wyniki badań nad możliwością racjonalnego wykorzystania odpadu powstającego przy produkcji perlitu ekspandowanego, jako mikrowypełniacza w budowlanych kompozytach żywicznych. Obecność pyłu perlitowego wpływa na cechy technologiczne mieszanek żywicznych, w tym czasy żelowania i wiązania spoiwa poliestrowego. Nie stwierdzono natomiast znaczącego wpływu tego składnika na cechy wytrzymałościowe kompozytu. Uzyskane wyniki wskazują na możliwość racjonalnego zagospodarowania uciążliwego odpadu, co dobrze wpisuje się w strategię zrównoważonego rozwoju w budownictwie. Jak dotąd, osiągnięto powodzenie przy substytucji prowadzonej na poziomie do 5 % masowych mikrowypełniacza – co wszakże, ze względu na bardzo małą gęstość nasypową pyłu perlitowego (< 100 kg/m3), oznacza redukcję dużej objętości składowanego odpadu. Autorzy planują próbę wprowadzenia do mieszanek żywicznych większych ilości pyłu perlitowego, co będzie wymagało rozwiązania problemów technologicznych związanych z dużą lotnością pyłu i jego niekorzystnym wpływem na urabialność mieszanek żywicznych

Influence of cement substitution by calcareous fly ash on the mechanical properties of polymer-cement composites

The aim of the presented research was to determine the influence of cement substitution with calcareous fly ash on the mechanical properties of polymer-cement composites. Coal combustion products such as calcareous fly ash have been already used in traditional cement composites as a part of cement and considered potential additions for concrete but its introduction into polymer-cement composites is still under preliminary investigation. The morphology of fly ash causes problems with its compatibility with polymer-cement binders but its insertion into those building materials is another way to utilize mineral combustion products that are cumbersome in storage and recycling. The influence of the mineral addition on polymer-cement composites containing 20% of polymer was especially taken into consideration. Mechanical properties of polymercement mortars modified with calcareous fly ash were tested after 28 and 90 days of curing. As a part of preliminary study, activity index of mineral addition was determined. Polymer-cement composites containing calcareous fly ash were characterized by higher flexural and tensile strength comparing to standardized mortar, even for the mortars containing 40% of mineral addition. The negative effect of the polymer-cement composites modification with calcareous fly ash was especially observed on the compressive strength of this composites

Frost resistance of concretes containing ground granulated blast-furnace slag

The paper deals with the influence of addition of ground granulated blast-furnace slag (GGBS) on the frost resistance of concrete. GGBS is a valuable modifier of concrete, having the latent hydraulic properties and particularly improving the chemical resistance of concrete. However, the performance of concretes with blast-furnace slag under freezing and thawing action is still not explained fully and remains a subject to discussion. The authors have investigated the concretes containing various amounts of GGBS and the portland cement CEM I, with various values of water to binder ratio, with and without the use of air-entraining admixture. The results of research show that the addition of blast-furnace slag causes some worsening of the frost resistance of concrete. The extent of this worsening depends on the water to binder ratio and the aeration of the concrete. However, even under the least favourable conditions, the concretes with GGBS addition have met the requirements of frost resistance after 200 cycles of freezing and thawing, given in the Standard PN-B-06265

Mortars with Polypropylene Fibers Modified with Tannic Acid to Increase Their Adhesion to Cement Matrices

The presented research’s main objective was to evaluate the possibility of improving the adhesion between polypropylene fibers and mineral matrices in cementitious composites by modifying the fibers’ surface with tannic acid (TA). This modifier was previously used for polyethylene fibers only. Cement mortar containing modified polypropylene fibers and mortar containing unmodified fibers were tested. The physical and mechanical properties (apparent density, compressive strength, flexural strength and modulus of elasticity) were determined, and the fibers’ morphology after the specimens’ destruction was observed. No adverse effect of the modification was found. The elastic modulus was 6% lower after 28 days, enabling the formation of a less stiff composite material. The integrity of the specimens after mechanical damage was improved, confirming the increased adhesion between the polypropylene fibers and the hardened cement paste. The results of the introductory tests are promising; however, further research is needed in the field

Korelacje pomiędzy wytrzymałościami na ściskanie i rozciąganie dla betonów do nawierzchni dwuwarstwowych z eksponowanym kruszywem

In the paper the results of experiments on concrete pavement with exposed aggregate technology placed in two technological layers were presented. The following properties were measured: compressive strength, flexural strength by two methods: two-point loading and centre-point loading, tensile splitting strength of cubic and cylindrical samples. The study was performed for two type of concrete with a maximum aggregate size Dmax 8 mm (concrete applied to the upper layer of concrete pavement - GWB) and Dmax 22 mm (concrete used for the bottom layer - DWB). After the analysis of the tests, the correlations between compressive strength and tensile strength, measured by flexural strength and tensile splitting strength, were determined for the used two-layers concrete pavement with exposed aggregate depending on applied Dmax.W referacie przedstawiono wyniki badań betonów stosowanych do nawierzchni dwuwarstwowych z eksponowanym kruszywem. Przeprowadzono badania wytrzymałościowe: wytrzymałość na ściskanie, wytrzymałość na zginanie metodą obciążenia dwupunktowego oraz metodą obciążenia centrycznego (jednopunktowego), wytrzymałość na rozciąganie przy rozłupywaniu na próbkach sześciennych oraz próbkach cylindrycznych. Badania wykonano dla dwóch betonów o maksymalnym nominalnym górnym wymiarze ziarn kruszywa Dmax 8 mm (beton stosowany do górnej warstwy nawierzchni betonowej - GWB) oraz Dmax 22 mm (beton używany do dolnej warstwy - DWB). Po analizie wykonanych badań ustalono korelacje pomiędzy wytrzymałością na ściskanie a wytrzymałością na rozciąganie określoną metodą wytrzymałości na zginanie oraz wytrzymałości na rozciąganie przy rozłupywaniu dla badanych betonów stosowanych do nawierzchni betonowych dwuwarstwowych nawierzchni z eksponowanym kruszywem w zależności od zastosowanego Dmax