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► Calcium carbonate biodeposition method contributed to decrease in water absorption of recycled concrete aggregate. ► Better efficiency was obtained for finer aggregate fraction and ...in the case of aggregate of lower quality. ► Efficiency of calcium chloride and whey as culture media was confirmed. ► Observations under SEM showed covering aggregate grains with calcium carbonate.
A growing demand for raw materials leads to danger of premature depletion of the natural sources. An alternative is to use by-products, provided their quality is improved. The paper presents surface modification of recycled aggregate concrete using biodeposition involving a method employing Sporosarcina pasteurii (Bacillus pasteurii) bacteria. It was possible to obtain reduction in water absorption of aggregate, the effect was more visible in case of finer fractions and for aggregates originating from inferior quality concrete. Calcium chloride was used for precipitation of calcium carbonate, while culture medium consisting of beef extract, peptone and urea was used for cultivation of microorganisms. In addition, whey, ecologically dangerous by-product from dairy industry was found to be effective as a culture medium. Presence of calcium carbonate crystals covering aggregate grains was confirmed by observations under scanning electron microscope. In the perspective, the proposed method, upon appropriate improvements, seems worthwhile due to ecological and technological reasons.
The paper is focused on the eco-efficiency calculations of recycled aggregate concrete (RAC) consisted of ordinary Portland and blast-furnace slag cements with three fine-grained wastes: quartz ...powder (Q), limestone powder (L) and fly ash (F). The characteristics of concrete mixes (slump and air content) and hardened concrete properties: 28- and 90-day compressive strength, water absorption as well as the depth of the carbonation (after the accelerated carbonation in the chamber) were examined. In order to parameterize the third feature of contemporary concrete, which is (next to the strength and durability) its sustainability potential, the binder intensity (bi) and carbon intensity (ci) indexes were calculated, taking into account CO2 emissions from cement production and technological processes related to preparation for use of other ingredients. The comparison of the effect of limestone powder and fly ash showed some advantages of the fly ash (taking into account the results of strength tests). However, limestone powder turned out to be more favorable in influencing other properties (especially resistance to carbonation). Nevertheless, the use of fly ash proved to be the most effective in terms of eco-efficiency factors. The pozzolanic properties of F increased the strength of the concrete, reducing both bi and ci values. Furthermore, the presence of F canceled out the negative effect of quartz powder. The use of F together with cement containing ground-granulated blast-furnace slag (GGBS) was most beneficial. Although quartz powder due to technological reasons occurred to be the worst option, its use may be beneficial when CO2 sequestration by concrete carbonation is taken into account. Lower strength and resistance to carbonation of concrete with Q allow CO2 to penetrate deeper into the structure, especially in concrete made of GGBS cement. In this way, the later uptake of CO2 from the atmosphere allows for a partial reduction of the ci value, making RAC more eco-efficient.
•The effects of quartz powder (Q), limestone (L) and fly ash (F) on RAC were tested•F increased compressive strength, L gave better slump and lower permeability•Q achieved the worst results, but in combination with L or F situation is improved•F considerably improved eco-efficiency, especially for RAC with GGBS cement•Use of Q may be beneficial if CO2 sequestration via carbonation is a priority
The paper presents the influence of different curing conditions—wet, dry, and protection against water evaporation (PEV)—on selected properties of concretes with different amounts of recycled ...concrete aggregate (RCA) previously subjected to atmospheric CO2 sequestration. Two types of cement were used, Portland cement and blast-furnace slag cement. The study was performed in laboratory conditions (at the temperature of 20 ± 1 °C and relative humidity of about 60%), according to currently applicable test procedures for most of the measured characteristics of concrete. Additionally, the eco-efficiency indexes (bi and ci) as well as the eco-durability S-CO2 index were calculated. It was found that dry conditions cause the properties of concrete to deteriorate, especially concrete made of blast-furnace slag cement, while PEV allows the achievement of results comparable to wet conditions. Moreover, for series with the highest amounts of coarse recycled aggregate and after longer periods of curing, the difference between the effects of wet curing and protection against water evaporation disappears. The eco-efficiency and eco-durability indexes approach confirms the beneficial effect of blast-furnace slag cement used as a binder, but on the condition of using a proper way of curing.
Contemporary solutions in concrete technology are varied, and consist in e.g. the use of new generation concretes, including the most spectacular achievement of the 1990s – self-compacting concrete ...(SCC) being the subject of continuous research, as well as protection of the environment against excessive anthropogenic pressures, such as carbon dioxide which is a major emission substance from the cement industry. The studies analysed the possibilities for replacing part of the clinker binder (cement CEM I 42.5 R) in self-compacting concrete with three types of waste mineral additives: fly ash, limestone powder, and granite powder. Focus was placed on key technological characteristics of concrete mixes: air content and rheological properties, maximal diameter of slump-flow and changes thereof over time, as well as the mix’s flow time into the 500 mm diameter, determining the flow dynamics. 28-day compressive strength of the concrete was recognised as a secondary property which in self-compacting concretes results from achieving the right range of the mix’s rheological properties. Concretes were produced using gravel-sand aggregate in 3-fraction composition and a high-efficiency superplasticiser. The studies were conducted as a planned experiment in the 3-ingredient mixes plan.
•Influence of type and size of aggregate and pozzolana cement on HSC was determined.•0/8mm aggregate with cement at 700 instead of 600kg/m3 improved strength by 8.5%.•In case of 0/16mm aggregate ...there was no need to increase cement amount to 700kg/m3.•Basalt or granite of 0/16mm size and 600kg/m3 of cement curbed HSC carbon footprint.
In compliance with up-to-date concrete technology requirements combining technological and ecological aspects, the paper describes the effect of the type and maximum aggregate size and cement content on some properties of high strength concrete. The following kinds of coarse aggregate were used to produce concrete: natural mineral (gravel) and crushed (granite and basalt) aggregates and pozzolana cement – ingredient classified as ecological binder. The concretes contained a highly effective superplasticiser and microsilica. Air content in concrete mixes, water absorption and concrete compressive strength after various periods of hardening were examined. Certain calculations (based on compressive strength results) on values of intensity indexes of cement used and carbon dioxide, treating them as a key for evaluation of eco-efficiency of concrete, were performed. Using pozzolana cement with simultaneous use of a highly effective superplasticiser and microsilica made it possible to obtain high strength concrete, made of mineral natural and crushed aggregates. More encouraging strength tests results were achieved for concrete of crushed aggregates, particularly granite. It was discovered that using aggregate with a maximum particle size less than 8mm instead of aggregate with particles measuring up to 16mm with a simultaneous increase in the cement content led to a greater rise in concrete strength. The smallest indexes of binder and carbon dioxide intensity were obtained as a result of use of granite and basalt aggregate, with a maximum particle size up to 16mm.
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•Sporosarcina pasteurii strain ensures lithification and increase of soil rigidity.•Biodeposition highly improves shear strength of silty soil at small deformations.•Sporosarcina ...pasteurii strain is resistant to dynamic impact typical for earthworks.•Observed strengthening effect may be applicable in building earth structures.
Contemporary challenges and results of the research to date show that the search for environmentally-friendly ways of soil improvement is the right direction. The paper presents biogrouting of silty soil compacted using standard energies in the laboratory soil compactor. An improvement of transition soils by biodeposition using Sporosarcina pasteurii has been undertaken. Biodeposition has increased shear strength in the triaxial compression test. It has been concluded that application of bacteria solution on the soil ensures lithification and a significant increase of soil rigidity. Resistance of Sporosarcina pasteurii strain to dynamic impact during soil compaction allows a possible application of these microorganisms in geoengineering.
The paper presents the influence of different curing conditions--wet, dry, and protection against water evaporation (PEV)--on selected properties of concretes with different amounts of recycled ...concrete aggregate (RCA) previously subjected to atmospheric CO.sub.2 sequestration. Two types of cement were used, Portland cement and blast-furnace slag cement. The study was performed in laboratory conditions (at the temperature of 20 + or - 1degreesC and relative humidity of about 60%), according to currently applicable test procedures for most of the measured characteristics of concrete. Additionally, the eco-efficiency indexes (b.sub.i and c.sub.i) as well as the eco-durability S-CO.sub.2 index were calculated. It was found that dry conditions cause the properties of concrete to deteriorate, especially concrete made of blast-furnace slag cement, while PEV allows the achievement of results comparable to wet conditions. Moreover, for series with the highest amounts of coarse recycled aggregate and after longer periods of curing, the difference between the effects of wet curing and protection against water evaporation disappears. The eco-efficiency and eco-durability indexes approach confirms the beneficial effect of blast-furnace slag cement used as a binder, but on the condition of using a proper way of curing. Keywords: curing conditions; carbonated recycled concrete aggregate; eco-efficiency indexes; eco-efficient index
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