Roman Jaskulski

Ecological Concrete Based on Blast-Furnace Cement with Incorporated Coarse Recycled Concrete Aggregate and Fly Ash Addition

This article deals with an experimental study concerning the development of concrete mixtures with significant ecological benefits. The studied concrete mixtures were based on blast-furnace cement, with an additional application of supplementary cementitious materials—fly ash, metakaolin, and silica fume and fluidized fly ash. Coarse aggregate in the form of crushed concrete was applied for all studied concrete mixtures. The experimental program was primarily focused on the assessment of the durability properties of the studied mixtures in terms of mechanical tests, absorption tests, chloride migration coefficient tests, water penetration tests, and accelerated carbonation depth tests. The results obtained showed good potential for waste materials in durable concrete production. The studied mixtures, with incorporated supplementary cementitious materials, exceeded the level of high performance concrete (HPC) in terms of mechanical properties. Such modification of the binding system also significantly contributed to an increase in durability properties; however, mixtures with the fluidized fly ash application exhibited reduced resistance to carbonation.

High Performance Concrete with SCM and Recycled Aggregate

In the article the possibility of utilization of two waste materials: Recycled Concrete Aggregate (RCA) fraction 4-16 mm and Class F fly ash (from coal burning power plant) in high perfor-mance concrete (HPC) was presented. Concrete with RCA were made with varying amount of cement and Suplementary Cementing Materials (SCM). The specimens of concrete were tested to compare mechanical properties as well as some properties related to the durability of concrete. Compression strength values up to 71.40 MPa were achieved and good values of properties determinig durability of reinforced concrete structures.

Monte Carlo Simulation of the Torsional Strength due to Concrete Compression of Reinforced Concrete Element

The aim of the work was to assess the safety margin of reinforced concrete element of rectangular cross-sections subjected to torsion. In the performed analyses two models of torsional resistance based on concrete compressive strength was taken into account. Assessment was performed with use of Monte Carlo method. Utilized models of shear resistance were taken from formerly used Polish standards: PN-84/B-03264, PN-B-03264:2002 and the actual Polish standard EN-1992-1-1:2004. From the same standards necessary assumptions related with the models were taken. The safety margin and influence of the differences in assumptions on the obtained results were analyzed. The selected models was also evaluated in terms of their “sensitivity” to changes of basic parameters of distribution functions of selected random variables. Results showed that average torsional resistance differs of about 50% times depending of assumed model. The reliability level, measured with the partial reliability exponent ΔR, differs of 10% if different models are concerned but the differences are much higher (up to 5 times, when the standard deviation of concrete compressive strength distribution changes).

Application of Granulated Cable Plastic Waste for Soil Stabilization

Paper deals with the assessment of practical utilization of granulated cable plastic waste (GCPW) for the production of stabilized soil layers in transport engineering. The main goal of the experimental work was the evaluation of the influence of GCPW on mechanical properties of soil stabilization based on the fluidized fly ash. Mechanical properties were investigated using standard procedures in soil mechanics. GCPW was dosed as a partial replacement of fluidized fly ash up to 30 %. It was concluded, that the studied level of replacement performs critical level, additional increasing of GCPW would lead to a decline of required mechanical properties. Besides, replacement by studied waste material caused lower values of the bulk density.

Influence of Mix Proportions on Water Absorption of RCA Concretes

The subject of the work is to develop probabilistic models defining the water absorption of concretes made with the use of recycled aggregate (RCA). For the study 16 series of concrete mixtures were made with a 50 mass% share of recycled aggregate in the whole amount of coarse aggregate. The analysis of test results aimed at formulating a relationship between water absorption value and selected parameters of the composition of concretes. The objective was to find a model giving the best fit between calculated values and test results. Formulated models were then used in probabilistic modeling absorption using a Monte Carlo simulation. The results indicate a good agreement of the mean values of water absorption and possibility of good fitting of the standard deviation if an additional summand is introduced into the model.

Probabilistic Modelling of Strength of Concretes with RCA

The subject of the work is research and probabilistic modelling of compressive and tensile strength of concrete with recycled concrete aggregate (RCA). Sixteen series of concrete containing natural aggregate and RCA of 50% by mass of coarse aggregate (fraction 4 – 16 mm). Concrete specimens were tested for compressive and tensile splitting strength. In the study also the absorptivity of recycled and natural aggregate was tested, which is the amount of water that both types of aggregates can absorb during concrete mix. Based on the results models were formulated describing the compressive and tensile strength of concrete with RCA. These models are based on the design parameters of the concrete mix. In order to determine the coefficients of the models an estimating of a function of several variables by linear regression was performed. Compliance of the values calculated using the models with the values obtained from the tests was determined by Monte Carlo simulation. The results indicated a possibility of obtaining a high compliance of the test results with results obtained from simulations based on formulated models.

Influence of Microwave Treatment on Properties of Concrete with Non-cyclic Alkanes

Influence of exposure to microwave (MW) radiation of concrete with paraffin addition was presented. Specimens were exposed to MW after 7 and 28 days from casting. The exposure times were: 20 minutes and 40 minutes. Concretes were made with 1 and 3% addition of paraffin of the volume of concrete mixture. As a reference served concrete with no paraffin addition and concrete containing paraffin but not treated with MW. Paraffin was added in two forms: as a powder (fine paraffin) and as a granules (coarse paraffin). Influence of radiation on compressive and tensile splitting strength was tested as well as its impact on sorptivity and free water absorption. Exposure to MW radiation lowered the mean values of concrete compressive and tensile splitting strength maximum of about 24%. Sorptivity test results showed no general tendency and free water absorption has decreased maximum about 20%.

Probabilistic Analysis of Shear Resistance Due to Concrete Tension

The aim of the work was to assess the safety margin of reinforced rectangular concrete cross-sections subjected to shear. In the performed analyses models of shear resistance based on concrete tension strength was taken into account. Assessment was performed with use of Monte Carlo method. Utilized models of shear resistance were taken from formerly used Polish standards: PN-84/B-03264, PN-B-03264:2002 and the European standard EN-1992-1-1:2004. From the same standard necessary assumptions related with the models were taken. The safety margin and influence of the differences in assumptions on the obtained results were analyzed. The selected models was also evaluated in terms of their “sensitivity” to changes of basic parameters of distribution functions of selected random variables. Results showed that average shear resistance differs about 3 times depending of assumed model of the shear resistance and the reliability level, measured with the partial reliability exponent ΔR, differs 4-7 times.