Institute of Fundamental Technological Research

Considering the long-time durability of concrete in road infrastructure it is important to control the threat of expansive reaction between sodium and potassium hydroxides in the pore solution and the reactive minerals present in the aggregate. Petrographic analysis is the basis for the qualification of aggregates to appropriate classes of reactivity according to ASTM C1778 and RILEM recommendations. This paper presents the results of petrographic analyses of thin sections made from twenty different domestic aggregates. The tested crushed aggregates were obtained from bedrock and glacial deposits. The evaluation of the mineral composition of aggregates included identification of deleterious components and determination of the content of reactive forms of silica. This enabled preliminary classification of aggregate in one of the three classes of reactivity according to RILEM. Obtained results provide an initial assessment of potential reactivity of aggregates and can assist in making decisions to undertake further accelerated or long-term laboratory testing or to modify the concrete mix design.

aggregate, alkali-aggregate reaction (AAR), petrographic analysis, reactive minerals, thin sections

Przedstawiono wyniki analizy petrograficznej 20 kruszyw łamanych z rożnych regionów Polski, przeprowadzonej na cienkich szlifach analizowanych pod mikroskopem w świetle przechodzącym. Próbki kruszyw grubych frakcji do 16 mm pochodziły ze skał litych oraz ze złóż polodowcowych z zakładów produkcji kruszyw, łamanych stosowanych do betonu. Ocenę składu mineralnego kruszyw, mającą na celu rozpoznanie składników szkodliwych, przeprowadzono z uwagi na zawartość reaktywnych minerałów krzemionkowych, m.in. opalu, krystobalitu, trydymitu, chalcedonu, wielkość kryształów (skryto- i mikrokrystaliczny kwarc) oraz kwarcu w stanie naprężeń. Zastosowanie metody petrograficznej na cienkich szlifach pozwoliło na wstępną kwalifikację do kategorii potencjalnie reaktywnej lub reaktywnej. Uzyskane wyniki badań stanowią wstępną informację o przydatności kruszyw jako składników betonu bądź o skierowaniu ich do dalszych szczegółowych badań lub ich odrzucenia

analiza petrograficzna, kruszywo, minerały reaktywne, reakcja alkaliczna kruszywa (AAR)

W artykule opisano podstawowe wyniki uzyskane w trakcie realizacji projektu badawczego „Trwałość i skuteczność betonowych osłon przed promieniowaniem jonizującym w obiektach energetyki jądrowej” [1]. Przedstawiono też wytyczne techniczne i kryteria oceny betonu osłonowego. Uzyskane wyniki mogą stanowić podstawę dalszych prac przy projektowaniu obiektów elektrowni jądrowych, składowisk materiałów radioaktywnych i innych miejsc powstawania, stosowania lub przechowywania materiałów wytwarzających promieniowanie jonizujące. Artykuł obejmuje zagadnienia związane z wymaganą skutecznością betonowych konstrukcji osłonowych przez zapewnienie bezpieczeństwa personelu i otoczenia przed oddziaływaniem promieniowania jonizującego. Rozpatrzono również trwałość osłon betonowych, tzn. zachowanie właściwości mechanicznych i nieprzepuszczalności w okresie przewidzianej eksploatacji pod wpływem przewidywanych oddziaływań zewnętrznych i procesów starzenia, a także przy podwyższonej temperaturze i promieniowaniu jonizującym. Artykuł nie obejmuje zagadnień integralności osłon pod obciążeniami wyjątkowymi, spowodowanymi awarią reaktora, uderzeniem samolotu, działaniami terrorystycznymi itp.

The influence of blended cements containing calcareous fly ash (W) on the strength and permeability of air entrained concrete was studied. Moderately active calcareous fly ash of CaO content of 26% and loss on ignition of 2%, obtained from lignite fired power station in Poland, was selected. Ternary cement compositions including siliceous fly ash (V) and ground granulated blast furnace slag (S) were also studied. Air void analysis in hardened concrete was used to evaluate the effectiveness of air entraining process. Pore size distribution was characterized by mercury intrusion porosimetry (MIP). The presence of calcareous fly ash in cement resulted in a moderate increase in the compressive strength of concrete and an increase of the category of resistance to chloride ion migration. Test results revealed a linear relationship between the capillary porosity measured by MIP and the chloride migration coefficient (Dnssm). The permeability was lower for increased clinker replacement level which was due to formation of smaller diameters of the capillary pores.

Air entrained concrete, Air void characteristics, Calcareous fly ash, Chloride ion migration, Multicomponent cements, Pore size distribution, Strength

The objective of this paper is to examine the possible use of new blended cements containing calcareous fly ash in structural concrete, potentially adequate for structural elements of nuclear power plants. The investigation included five new cements made with different contents of non-clinker constituents: calcareous fly ash, siliceous fly ash, ground granulated blastfurnace slag, and a reference cement—ordinary Portland cement. The influence of innovative cements on the resistance of concrete to chloride and carbonation exposure was studied. Additionally, an evaluation of the microstructure was performed using optical microscopy on concrete thin sections. Test results revealed a substantial improvement of the resistance to chloride ion penetration into concrete containing blended cements. The resistance was higher for increased clinker replacement levels and increased with curing time. However, concrete made with blended cements exhibited higher depth of carbonation than the Portland cement concrete, except the Portland-fly ash cement with 14.3% of calcareous fly ash. The thin sections analysis confirmed the values of the carbonation depth obtained from the phenolphthalein test. Test results indicate the possible range of application for new cements containing calcareous fly ash.

blended cements, calcareous fly ash, chloride migration, carbonation, durability, nuclear shielding concrete, thin sections

Możliwość wystąpienia reakcji alkalicznej wodorotlenków sodu i potasu (Alkali Silica Reaction, ASR) w betonowych osłonach reaktorów wymaga szczególnej ostrożności przy doborze składników betonów do realizacji programu energii jądrowej w Polsce. Uszkodzenia osłon reaktorów w USA i w Belgii wskazują kierunki niezbędnych badań, [1-3]. W badaniach przedstawionych w artykule zastosowano kruszywa o dużej gęstości (osłabianie promieniowania gamma): magnetytowe, barytowe oraz hematytowe oraz kruszywo o wysokiej zawartości wody związanej (absorpcja promieniowania neutronowego) – kruszywo serpentynitowe. Przeprowadzono badania mikroskopowe kruszyw na cienkich szlifach w celu identyfikacji potencjalnie szkodliwych minerałów z uwagi na zagrożenie ASR, oraz przyspieszone i długotrwałe badania w celu określenia potencjalnej reaktywności alkalicznej tych kruszyw. Wyniki badań wykluczyły możliwość stosowania kruszywa hematytowego do betonów osłonowych. Wyniki badań odnośnie do wykorzystania dostępnych kruszyw specjalnych tworzą podstawy projektowania bezpiecznych osłon w warunkach krajowych

reakcja krzemionki z wodorotlenkami sodu i potasu (ASR), ekspansja, beton osłonowy, kruszywo specjalne

Przedstawiono wyniki badań podciągania kapilarnego (PK), porowatości dostępnej dla wody (E) oraz współczynnika migracji jonów chlorkowych w stanie nieustalonym (Dnssm). Zakres badań obejmował betony z kruszywem magnetytowym, barytowym, serpentynitowym oraz kruszywem referencyjnym w postaci grysu amfibolitowego, które wcześniej poddane zostały selektywnemu kruszeniu i przesiewaniu, tak by zapewnić jednakowe krzywe uziarnienia/stosy okruchowe. Prze analizowano wpływ mikrostruktury porów wyznaczonej za pomocą porozymetrii rtęciowej z odpornością na wnikanie jonów i cieczy w matrycę cementową. Z badań wynika, że betony z kruszywami specjalnymi osiągają wskaźniki przepuszczalności porównywalne lub nieco gorsze niż próbki referencyjne. Nie zaobserwowano systematycznego wpływu porowatości kapilarnej na wyniki badań przepuszczalności.

podciąganie kapilarne, migracja jonów chlorkowych, kruszywo magnetytowe, kruszywo barytowe, kruszywo serpentynitowe, porowatość

The aim of the study was to generate rules for the prediction of the chloride resistance of concrete modified with high calcium fly ash using machine learning methods. The rapid chloride permeability test, according to the Nordtest Method Build 492, was used for determining the chloride ions’ penetration in concrete containing high calcium fly ash (HCFA) for partial replacement of Portland cement. The results of the performed tests were used as the training set to generate rules describing the relation between material composition and the chloride resistance. Multiple methods for rule generation were applied and compared. The rules generated by algorithm J48 from the Weka workbench provided the means for adequate classification of plain concretes and concretes modified with high calcium fly ash as materials of good, acceptable or unacceptable resistance to chloride penetration.

chloride penetration, concrete, durability, high calcium fly ash, machine learning

Concretes for the shields against ionizing radiation should be executed with particular care to satisfy all requirements, not only effective attenuation of different radiation but also sufficient durability. In the paper fundamental problems are presented that are related with designing of such protective concretes in order to avoid alkali-aggregate reaction. The results of preliminary investigations are presented that indicate how to select barite aggregate and to define composition of concrete mix. Present knowledge in that area of materials engineering should be completed before initiation of construction of nuclear power stations at industrial scale in Poland.

Alkali Aggregate Reaction (AAR), heavy aggregate, ionizing radiation

The paper presents the investigation of concrete resistance to penetration by liquid and gaseous environmental media. Calcareous fly ash obtained from Bełchatów Power Station was used as concrete additive. In the mix design a certain portion of binder (15% and 30%) was substituted with calcareous fly ash assuming the efficiency factors of 0.7 or 1.0. The tested parameters included the air permeability coefficient measured with Torrent method, the depth of water penetration under pressure and the coefficient of chloride ions migration measured with the rapid chloride migration test. It was established that the addition of calcareous fly ash resulted in the desired reduction of the value of a chloride migration coefficient while the effect on the permeability of water and air was similar to the effect it had on the compressive strength of concrete.

air permeability, calcareous fly ash, chloride migration, compressive strength, fly ash processing, Torrent method, water permeability

The purpose of this research was to determine the carbonation depths in concrete containing calcareous fly ash. Eleven concrete mixes with the same water-binder ratio w/b and with different amounts of calcareous fly ash have been prepared in laboratory. In the test series I the mixes were produced with five blended cements containing different amounts of the following supplementary cementitious materials: calcareous fly ash, siliceous fly ash and granulated blast furnace slag. The second test series was produced with calcareous fly ash replacing 30% of the cement by weight. The maximum depth of carbonation in concrete was determined using the phenolphthalein method. The progress of the carbonation front was established by analysing polished thin sections of concrete under a polarizing microscope in transmitted light. The most resistant to carbonation was the concrete containing, beside clinker, 14.3% of calcareous fly ash as a cementitious material. The specimens of concrete containing different amounts of calcareous fly ash were compared and no significant variations were found both in the rate and depth of carbonation. On the other hand, the rate of advancement of carbonation front was higher in concrete containing calcareous fly ash as compared to the reference concrete without admixtures.

blended cements, calcareous fly ash, carbonation, particle size separation of fly ash

Przedstawiono wyniki badań wytrzymałości na ściskanie, odporności na wnikanie chlorków oraz odporności na powierzchniowe łuszczenie w obecności soli odladzających betonów napowietrzonych z popiołem lotnym wapiennym (W). Próbki betonu dojrzewały w odmiennych warunkach wilgotnościowych. Zakres badań obejmował betony napowietrzone o współczynniku w/c=0,45 wykonane z cementów portlandzkich wieloskładnikowych z dodatkiem popiołu W oraz z dodatkami popiołu lotnego krzemionkowego V i mielonego granulowanego żużla wielkopiecowego S. Próbki dojrzewały przez 28 i 90 dni, z czego połowa w wodzie, natomiast druga połowa po 3 dniowej pielęgnacji w powietrzu w wilgotności RH=40%. Charakterystyka porów powietrznych w stwardniałym betonie została oznaczona metodą mikroskopowej analizy obrazu. Z badań wynika, że przy zbliżonych parametrach charakterystyki porów powietrznych zmiana warunków pielęgnacji próbek obniża w znaczący sposób trwałość betonu. Największy wpływ zmiennych warunków i czasów dojrzewania zaobserwowano w odniesieniu do odporności betonu na agresję mrozu i środków odladzających.

charakterystyka porów, napowietrzenie, penetracja chlorków, popiól lotny wapienny, powierzchniowe złuszczenie

Celem przeprowadzonych badań była ocena przepuszczalności betonu zawierającego popiół lotny wapienny pochodzący ze spalania węgla brunatnego, w stanie surowym i po dodatkowym domieleniu. W badaniach skoncentrowano się na określeniu wpływu ilości popiołu jako dodatku do betonu na wnikanie mediów agresywnych. Określono podstawowe właściwości mieszanki betonowej oraz wytrzymałość na ściskanie. Oznaczono współczynnik migracji jonów chlorkowych przy nieustalonym ich przepływie, głębokość penetracji wody pod ciśnieniem oraz współczynnik gazoprzepuszczalności betonu. Mikrostrukturę badanych betonów przeanalizowano na cienkich płytkach w mikroskopie polaryzacyjnym do światła przechodzącego. Stwierdzono, że zastąpienie cementu przez dodatek popiołów lotnych wapiennych do betonu w ilości 15% lub 30% przy w / s =0,55 powoduje poprawę ich wodo- i gazoszczelności, z tą jednak różnicą, że do zmniejszenia gazoprzepuszczalności betonu odpowiedniejsze jest stosowanie popiołów domielonych. Niższe wartości współczynnika migracji jonów chlorkowych otrzymano w betonach zawierających popiół lotny wapienny, wzrost w / s zwiększył przenikalność jonów chlorkowych. Analiza obrazów na cienkich szlifach betonowych wykazała, że w miarę wzrostu zawartości popiołu w betonie wzrasta również ilość niespalonych cząstek węgla w matrycy, których wielkość jest zależna od czasu mielenia popiołu

gazoprzepuszczalność, migracja chlorków, mikrostruktura, popiół lotny wapienny, wodoprzepuszczalność

Salt solutions are used to ensure safe driving conditions during winter. NaCl deicer is the most often used brine in Polish climatic zone. The chemical effects of this type of chloride-based deicer in wetting and drying (WD) and temperature cycles on concrete need to be better understood. This research was focus to study the microstructure of air-entrained pavement concrete after combined chemical (10% of NaCl) and physical (WD and 60°C) exposure conditions. The adopted WD and temperature regime was designed to verify the hypothesis that regularly alternating wetting and drying cycles with external alkali supply from deicer salt will provoke the Alkali-Silica Reaction (ASR). The aggregates varied their origin and mineralogical composition. The microscopic examination was carried out on concrete specimens using SEM with EDX. The microscopic analysis has shown that main reason for concrete deterioration during cyclic chemical and physical exposure conditions was both physical influence - WD cycles and the chemical influence – ASR (primarily, the fine aggregate which lead to form of alkali-silica gel). The expansive gel was shown to be capable of destroying the test specimens. Also differences in mineralogical composition of coarse aggregates influenced on the concrete prism expansion due to ASR.

The addition of natural fibers residue in cement based materials can be a sustainable technological alternative for traditional dispersed reinforcement, and can improve the performance of brittle matrix materials. The presence of a wool reinforcement can increase the fracture toughness and, at the same time, can reduce the environmental impact of cementitious mortars. The beneficial effects are similarly to those observed in presence of vegetal fibers (e.g., hemp), which have been largely investigated in the literature. However, there are some limits in the use of wool fibers due to their chemical compatibility with the cement matrix, as they can dissolve in alkaline environments. In the present paper, to investigate the compatibility between wool fibers and cementitious mortars, laboratory prototypes have been taken into consideration. Three series of wool-reinforced mortar beams have been cast and cured in water (20°C) or in dry conditions (temp. 20 °C, 50% R.H.) for some days. Portland-limestone cement CEM II has been used, whereas the content of fibers has been limited to about 1% in volume to maintain the workability of the mortars. To investigate the chemical compatibility, and the subsequent effects on the mechanical performances, prototypes have been tested in three point bending. After the mechanical test, the mortars microstructure was evaluated through SEM images and by thin section in transmitted light, in order to individuate a possible relationship between the dissolution of wool and curing conditions. The microstructure observation revealed the capability of wool fibers to bridge the cracks, and to reduce the brittleness of plain mortars. The differences in the mortars microstructure due to alternative curing conditions were also observed and described in the paper. Accordingly, wool could be effectively used to reduce the plastic shrinkage of cementbased composites, like the industrially manufactured polypropylene fibers.

Wool fibers, Plain cement-based mortar, Fiber-reinforced mortar, Polypropylene fibers, Three point bending tests, SEM analyses

In the present study, the potential for the alkali–silica reaction (ASR) in radiation shielding concrete containing special aggregates is presented. The tests were performed on two kinds of aggregate: (1) high-density aggregate to absorb the gamma radiation (barite, magnetite, and hematite) and (2) mineral with high bound water content to attenuate the neutron flux (serpentinite). The optical microscopy in transparent light on thin sections, XRD and XRF method, was used to assess the mineral composition of aggregates. ASTM C1260 test method for potential alkali reactivity of aggregates was applied also to investigate the effect of different content and crystal size of silica on the expansion due to ASR. The tests revealed that all tested aggregates, such as barite, magnetite, hematite, and serpentinite, were characterized by low solubility at high pH. The XRD and XRF results have shown presence of silica in all tested aggregates, but the microscopic observations enhanced size and composition of SiO2 crystals. The aggregates were not deleterious themselves, but the different content and size of SiO2 crystals in the aggregate influenced their potential for alkali–silica reaction. The quartz in heavy kinds of rocks and in the serpentinite used for radiation shielding was just as much potentially susceptible to deleterious ASR as quartz in common rocks used in concrete technology. In the hematite, silica crystals were classified as microcrystalline, so it should be considered as potentially reactive. The expansion tests confirmed that hematite was highly reactive. Other aggregates after 14 days of testing did not exceed 0.1% elongation limit. The microstructural analysis of thin sections prepared from mortars after ASTM C1260 test confirmed expansion of aggregate grains due to ASR.

Alkali-Silica Reaction (ASR), ionizing radiation, high density aggregate

The use of exposed aggregate concrete (EAC) in the upper layer of two-lift pavements is spread over many European countries including Poland. However, the EAC technology is considered difficult to apply because of inevitable dependence on operator's experience to control the whole process properly. The proper timing of technological operations is critical. The investigation on the performance of EAC was performed to gain a better understanding of material and environmental factors involved. EAC slabs were manufactured in the laboratory following the procedure applied at the construction site. Air entrained concrete mix design included a variable water to cement ratio and cement type while the type and the content of aggregate was constant. The effects of curing intensity were studied. The strength properties, air void characteristics of hardened concrete, the freeze-thaw resistance and the salt-scaling resistance were tested of specimens cored from the slabs, using the European standard methods. EAC permeability was also evaluated using the methods covered by ASTM C1585 and NT Build 492. Such permeability indicators and frost durability were applied to evaluate the differences in EAC layers performance. The environmental vulnerability of EAC mixes used in the upper layer of two-lift pavements is discussed.

air entrainment, blended cement, concrete durability, curing technology, highway pavement, mix design, permeability

The relationship between the internal pore characteristic and the non-steady state chloride migration coefficient (Dnssm) was investigated for concrete mixes made with blended cement containing high calcium fly ash (HCFA). Air entrained concrete mixes were made usinggranodiorite and crushed limestone as coarse aggregate. Designed surface scaling resistance was confirmed with standard test. The pore structure was determined using mercury intrusion porosimetry (MIP) and digital image analysis techniques. Phase composition of hydration products was examined using the XRD analysis. Chloride ion transportvelocity was measured using a rapid chloride migration test.The test has shown a relationship between the chloride migration coefficient and poresizecharacteristic derived from MIP tests. Effect of aggregate type on the course of relationship as shown differences curve for both type of aggregates. Increase amount of additives in blended cements caused decrease of critical and average pore size obtained by MIP method.

HCFA, blended cement, chloride ions migration, MIP, scaling resistance

In the present study the potential appearance of the alkali-silica reaction (ASR) in heavy aggregates was studied. ASTM C1260 Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method) was applied. In order to investigate the effect of the content of alkalies in cement on the expansions due to ASR, three levels of total and soluble alkali content of cement were studied. Three portland cements Type I with different alkali content were selected. Two ordinary portland cements, which are commonly available in the market and one special cement were tested. That cement was specially made for the purpose of the nuclear shielding concrete CEM I NA-SR-LH of low-alkali, increased sulphate resistance and low heat of hydration. For the tests according to ASTM C 1260 the high-density aggregates, known as absorbing gamma radiation were selected: barite, magnetite and hematite. The expansion test revealed that hematite was highly reactive, regardless of the type of cement. Already after four days of storage in 1 N NaOH and 80°C the mortar bar expansion exceeded the limit of 0.1%, and after next four days was more than 0.2%., which qualifies it extremely reactive aggregate. Other aggregates after 14 days of testing did not exceed 0.1% elongation limit, but the influence of the type of cement was noticed. There was a noticeable tendency for increasing the total expansion with increasing the alkali content of cement.

Alkali-Silica Reaction (ASR), high density aggregate, cement composition

The results of microscopic analysis on thin sections of aggregates intended for nuclear shielding concrete are presented. The petrographic analysis was performed on different barite, magnetite and hematite aggregates used as the high-density aggregate to absorb gamma radiation. Both optical microscopy and accelerated expansion tests were used to recognise the potential for alkali-reactivity of the aggregates. The mineral composition of the tested aggregates was analysed on thin sections in transmitted cross-polarized light and XRD tests were additionally performed. Expansion tests of mortar bars exposed to 1 N NaOH solution at the temperature of 80°C were also performed following ASTM C1260. The high-density aggregates contained ore deposits - metallic opaque phases providing the required shielding properties. These aggregates also contained various amounts of non-metallic phases, with both innocuous non-ore minerals and deleterious, potentially reactive materials. Barite aggregates contained siderite, fluorite and hawleyite in varying amounts, apart from the barium sulphate being the principal component. Moreover, particularly reactive cristobalite and muscovite were identified in barite aggregates from certain quarries. Tests according to ASTM C1260 performed on mortars showed the expansion above the accepted criterion for non-reactive aggregate and confirmed the threat due to the presence of cristobalite in barite aggregates.

high-density aggregate, heavy concrete, alkali-silica reaction, thin section, XRD

The construction of Żarnowiec Nuclear Power Plant (NPP) facilities was discontinued in 1989, despite the high level of work advancement. Already a large part of the concrete structures was built, now submerged in water from Żarnowieckie Lake. These structures were exposed over 30 years to the environmental conditions (rain, and varying high and low temperatures) without any special maintenance treatment. The technological documentation archives are not available. Experimental testing of specimens drilled out from different concrete structure elements was performed in September 2014.
The goal of the research was the identification of the composition of concrete and its present properties, especially the recognition of the effects of long-term environmental impact. The scope of the research covered macroscopic and microscopic analysis of concrete, compressive strength test, permeability test defined as the rate of chloride ions migration and water absorption. Unfortunately, the most important parts of the concrete structure are not available for testing because they are under water level. The obtained results allowed to classify the concrete structural elements in nuclear power plants buildings as of a quite good quality.

durability, old concrete, strength, microstructure, permeability

In the paper the barite aggregate has been analyzed as a potential source of ASR in heavy concrete. Special attention was paid to BaSO4 and minor mineral components in aggregates and their influence on ASR development in tested mortars

heavy aggregate, Alkali Silica Reaction (ASR), ionizing radiation

In this paper the resistance to chloride penetration into concrete containing various high-calcium fly ashes (HCFA) from brown coal combustion in power industry is examined. HCFA from Belchatow Power Plant was used as nonstandard concrete additive for partial replacement of cement in the mix. To evaluate the concrete resistance to chloride ion penetration the standard method of determination of chloride migration coefficient from non-steady-state migration test according to NT Build 492 was used. The range of investigation included fly ash grinded to specified specific surface as well unprocessed fly ash. Test results revaled a substantial improvement of the resistance to chloride penetration into concrete containing HCFA as partial replacement of Portland cement. The resistance was higher for increased replacement level and decreased water-to-cement ratio. Favourable effects of high-calcium fly ash are discussed in relation to k-factor concept

chloride penetration, high calcium fly ash, cement replacement

The investigation of the influence of solid residue from hard coal combustion in circulating fluidized bed boilers on the strength of concrete was performed. The ash samples from power plant were collected regularly during 12 months to allow evaluation of variability of ash properties. Cementitious mixes were designed at the constant workability and batched using fluidized bed ash for partial replacement of Portland cement CEM I. The compressive strength of concrete at the age beyond 28 days was found to increase due to FBC ash addition for replacement of 20% of cement. The efficiency of fluidizied bed ash as potential type II concrete additive was evaluated using Bolomey's and Feret's formulas for the compressive strength of concrete. The efficiency factors were established at the age of concrete up to 1 year

cement replacement, efficiency factor, fluidized bed fly ash, strength of concrete, type II additive

Przeprowadzono badania doświadczalne przepuszczalności powietrza przez beton przy zastosowaniu nieniszczącej metody Torrenta. Zaprojektowano i wykonano płyty betonowe z mieszanek o jednakowym stosie okruchowym i zróżnicowanym spoiwie poprzez zastosowanie dodatków popiołowych. Wykonane elementy próbne pielęgnowano w warunkach normowych wysokiej wilgotności, a później poddano suszeniu w warunkach laboratoryjnych. Przeprowadzono pomiary współczynnika gazoprzepuszczalności kT oraz oporu elektrycznego sondą Wennera. Ponadto, przeprowadzono normowe określenie wytrzymałości betonu na ściskanie. Jak stwierdzono, współczynnik gazoprzepuszczalności kT betonu zwiększał się o dwa rzędy wielkości wskutek wysychania elementów próbnych. Przydatność sondy Wennera do pośredniego określenia wilgotności betonu była ograniczona. Stwierdzono istotny wpływ modyfikacji popiołowych na współczynnik przepuszczalności powietrza przez beton.

beton, gazoprzepuszczalność, popiół lotny, wilgotność, wytrzymałość na ściskanie

Celem rozpoczętych badań jest ocena przepuszczalności betonu zawierającego popiół lotny wapienny pochodzący ze spalania węgla brunatnego w energetyce zawodowej, w szczególności jakościowe rozpoznanie i określenie ilościowe wpływu składnika popiołowego w cemencie lub dodatku popiołu do betonu na wnikanie mediów agresywnych. W referacie przedstawiono podstawowe koncepcje badawcze oraz wyniki określania szczelności betonu na podstawie literatury. Stwierdzono, że można oczekiwać korzystnych efektów stosowania popiołu lotnego wapiennego, ujawniających się znaczącą redukcją współczynnika dyfuzji i współczynnika migracji chlorków, a także efektów niekorzystnych polegających na zwiększeniu przepuszczalności powietrza i ewentualnie podwyższeniu szybkości karbonatyzacji.

popiół lotny wapienny, trwałość, beton

kruszywa łamane, reakcja AAR, analiza petrograficzna