Characteristics of Portland cement pastes with high replacement of slag
The influence of substitution of Ordinary Portland cement by ground granulated blast-furnace slag up to 70% on the properties of humo de sílice-Portland cement composite pastes up to 12 months was studied. After one year, the composite cements pastes containing 50-70 % slag exhibit higher strength values compared to without slag sample. Also, The XRD results show that the C-S-H are intensifi ed with available increase indicating more dense structures and large amount of additional C-S-H in the presence slag content.
Evaluation of Egyptian oil shale ashes as admixture to ordinary Portland cement. Part I: Preparation and characterization of the shale ashes and blended cements
Ashes have been prepared from Egyptian oil shales from two different mines (shale ash I and shale ash II) by burning them in a laboratory muffl e kilns at 700 & 800 °C for 2 hours. The prepared shales have been characterized through determined their chemical composition, specific surface area, x-ray analysis and scanning electron microscopy. Blended cement mixes were prepared by dry mixing of the oil shale ash with ordinary Portland cement in weight ratios ranging from 0–30% ash. Blended cements and their pastes have been characterized through determining their surface area, bulk density and apparent porosity and compressive strength.
It was found that the firing temperature of the shale to produce ash has slight effect on the ash properties as well as the physico-mechanical properties of the of the prepared blended cement pastes. It has been found that shale ash II has better pozzolanic properties than shale ash I referring to its higher values of the sum SiO2 + Al2O3 + Fe2O3. With addition of both types of ash to OPC its specific surface area, water of consistency, initial and final setting times increase due to the extensive larger specific surface area of the ash. Ultimate strength of the hydrated blended cement pastes showed reasonable accepted values up to 10% shale ash I and 30% shale II.
Study of enriched oxygen combustion in rotary kilns for cement production
This work analyses the benefi ts and effects of oxygen-enriched combustion in the rotary kilns of cement-production plants. The scientific literature generally reported that the oxygen enrichment has several positive effects: it improves clinker production (between 3.5 – 4.7 t clinker/tO2) and it increases flame stability without severely aff ecting the refractory lining of the kiln walls. On the other hand, among its deleterious effects, it increases NOx emissions. The main drawback of this process is its economic profitability. The increase in clinker production does not off set the high costs of O2 generation. For this reason, the use of O2 in cement production plants has been limited only to experimental trials.
A study of the use of unbonded caps in the determination of compressive strenght of hardened concrete cylinders
This study includes different aspects of the compressive strength test evaluating in a specific way the use of elastomeric pads and their differences in relation with the use of sulfur. In this sense the environmental factors stand out because of the use of sulfur as well as the safety and health practices during accomplishment the capping.
The investigation has shown that the use of unbonded caps could lead to an agile, optimized and reliable form of evaluation of the compressive strength which is one of the basic characteristics of the hardened concrete. The analysis indicated a good correlation between the two methods.
Medium-time response of restoration actions: Results of EcoQuarry project in Catalonia
Quarry exploitation determines significant environmental impacts and quarry companies must restore the derelict areas according to environmental regulations. The present work evaluates the restoration actions implemented in the project EcoQuarry, funded by Environmental-LIFE program and quarry companies, by monitoring the evolution of vegetation over time after application. The experimental plots are distributed in seven quarries of Catalonia. The project includes experiments with different plant species (herbaceous and woody species) and compost application on substrates (mine spoils and topsoil substrates).
The different substrates were the main driver in discriminating herbaceous vegetation types developed. Spoil mine substrates, free of seed bank, were dominated by the seeded mixtures of plants while the topsoil substrates were dominated by spontaneous annuals plants. The compost application increased the plant cover only on spoil substrates but reduced the survival of woody plantation. Different mixtures of herbaceous species were assayed including native versus fastgrowing species. The native species grew slowly and, thus, the survival of plantation was higher than that of fast-growing mixtures, that can consume quickly the soil water.
Recycling and waste recovery in the spanish cement industry (update period 2007-2009)
The Cement and Environment Labour Foundation (CEMA Foundation) published in 2009 the study 'Recycling and waste recovery in the Spanish cement industry', developed by the 'Instituto Cerdá' for the period 2004-2006. This study update has the objective to become a permanent observatory regarding the situation of the cement plants that have environmental authorizations for waste valorization and, at the same time, to carry out the recycling and waste recovery inventory in the Spanish cement plants.
Dock extension of the Vigo Port
The extension of the Trasantlantic Dock of the Vigo Port, in northwest Spain, was carried out by means of three dolphins, each of them founded on 7 piles with a diameter of 1500 mm. The pile driving execution system from pontoon and all execution resources are described in the article.
'Pedro Gómez Bosque' footbridge over the Pisuerga river in Valladolid (Spain). A new length record in stressed-ribbon footbridges
A new footbridge has been constructed over the Pisuerga river in the city of Valladolid (Spain). Its length has set a new record for stressed-ribbon footbridges. The work was designed in this way due to the diff erence of 2 m between the heights of the banks of the river. The main features of the design and building process of the footbridge are described in the article.