International Concrete Abstracts Portal

The materials used for the investigation were fly ash and granulated slag from the Yurga thermal power plant used up molding sand from the Yurga machine building plant and the high alumina product (HAP) from the Yurga abrasion works. The bulk density, the absolute density and the surface area of the fly ash were 1150 to 1200, 2800 to 2850 kg/m3 and 300 to 310 m2/kg, respectively. To enhance its binding properties, it had to be ground. According to its chemical analysis (31.73% free CaO, 1.87% S03,1-06% LOI), the ash was high-calcium. It had a good binding properties with the more than 1: Cq=CaO+MgO+Al2O3/S'02. Slag sand of 0.14 to 5 mm particle size from its chemical analysis met the State Standard requirements for use as an aggregate. There was very little loss on ignition. The burnt sand was composed 92% quartz sand, 6% bentonite clay and 2% liquid glass. After being used in foundry and removing of gritty scale, it had the form of black sand with the fineness modulus, bulk density and absolute density being 1.91, 1450 and 2380 kg1m3, respectively. The burnt sand had a high content of SiO2 in the amorphous state. Very little loss on ignition was observed which increased the feasibility of chemical binding free CaO into calcium silicates. The high alumina product was a powder containing above 88% Al2O3. The radionuclides contents of all the materials used was 3 to 5 times lower than the standards. By grinding the three components (fly ash, burnt sand and HAP) in a planetary mill a new binder not containing portland cement was obtained. In the process of grinding, the mechanochemical activation of the components as well as the interaction of the amorphous silica and HAP with free CaO took place. The compressive strength of the binder was 50 to 60 MPa. The study of the secondary resources permits the developing on their basis of a high-performance heat-insulating not containing portland cement concrete using the air-entraining admixture and the slag sand as an aggregate.

The purpose of this study is to investigate the characteristics of strength development and carbonation rate due to the replacement ratio of blast-furnace slag and the curing conditions. Cementing efficiency factor k is introduced to evaluate the ability of blast-furnace slag. The water-binder ratios were 0.40, 0.50 and 0.65 containing blast-furnace slag with replacement ratio of 50%, and the specimens were cured in water for 5, 10, 28 days. After the designated curing duration, the compression tests were con-ducted and the concrete prisms were stored in accelerated carbonation test chamber. Test results show that the equivalence factor kc on strength development is larger than the factor kn on carbonation rate in every curing condition. Furthermore, the pore structure and the variation of calcium hydroxide and calcium carbonate were measured to evaluate the influence of replacement ratio of blast-furnace slag and curing condition.

In this study, environmental performance indicator is proposed for comprehensively evaluating the environmental burdens of concrete. Also an environmental life cycle assessment (LCA) is done to comprehensively estimate and to quantitatively compare the environmental burden of concrete containing fly ash over plain concrete, associated with the stages from resource acquisition to concrete's production process. The considered environmental impacts include COY SOx, NO., emissions, energy consumption, waste discharge and land use. The LCA results show quantitatively a fact that concrete containing fly ash is a kind of environment-friendly material relative to plain concrete, whether cement or fine aggregate is replaced. Replacing portland cement than using for fine aggregate will bring a greater reduction in environmental burden of concrete. The evaluation, only relying on the reductions in energy consumption and CO2 emission, will underestimate the eco-balance performance of fly ash concrete. When cement is replaced, all the land use area, air emissions and energy consumption decrease obviously. However, only is the land use area clearly reduced in case of replacing fine aggregate. Moreover, the eco-efficiency of fly ash concrete is greater than that of plain concrete.

This paper describes briefly the construction and performance of two high-volume fly ash (HVFA) concrete road pavements in India. In addition to data on the materials and mixture proportions used in these projects, test results are given on compression and flexural strengths together with chloride-ion penetrability of drilled concrete cores. The roads have been in service for more than one year. Based on the performance under a traffic load of more than 500 commercial vehicles per day, it can be concluded that compared to asphalt roads, HVFA concrete is more suitable for the construction of rural, regional, and the national network of roads in India.

This paper reports the properties of two series of flowable self-compacting slurry. In Series 1, five mixtures of flowable slurry were made using ponded coal-combustion fly ash and quarry screenings (fine crushed sand). In Series 2, six mixtures of flowable slurry were made, the first five mixtures using the ponded coal-ash and natural sand, and the final one mixture using Class C fly ash and natural sand. Ash and quarry-screenings contents of the mixtures are expressed as percentages of the sum of the quantities of the ash and aggregate. For Series 1 flowable-slurry mixtures, ponded-ash content was 100, 67, 53, 35, and 0 percent, and quarry-screenings content was 0, 33, 47, 65, and 100 per-cent, respectively. In Series 2 flowable-slurry mixtures, ash content was 100, 81, 60, 40, 20, and 4 percent, and sand content was 0, 19, 40, 60, 80, and 96 percent, respectively. For both series of flowable-slurry mixtures, tests were performed for flow, density, settlement, compressive strength, and permeability. Ambient air and slurry temperatures were also recorded. Compressive strength of both Series 1 and Series 2 mixtures increased with age. Compressive strength of Series I mixture was higher than Series 2 mixtures. It was also observed that the permeability of flowable-slurry mixtures decreased with increase in age due to improvement in microstructure and increase in strength of the flowable-slurry mixtures. Mixtures containing quarry screenings were also less permeable.