Time filter

Source Type

Östermalm, Sweden

Ekblad J.,NCC Roads AB | Lundstrom R.,NCC Roads AB | Simonsen E.,Cementa AB
Materials and Structures/Materiaux et Constructions | Year: 2015

Water affects asphalt pavements in a detrimental way and it is common knowledge that certain combinations of binder and aggregate can trigger premature failures. Asphalt manufacturing relies mainly on experience and continuous empirical testing. To reduce water sensitivity, adhesion promoters are frequently used. In this investigation, focus was on using portland cement and a by-product from cement manufacturing, cement kiln dust (CKD). The hypothesis was that water susceptibility is influenced by the grading of the hydraulically active fillers: a finer grading will give a stronger improvement. The experimental plan comprised, besides a reference material, 3 different cements and 2 CKDs. Water susceptibility was assessed with the tumbler abrasion test using mastic specimens. Potentially negative effects: decreased workability and degraded low temperature properties were investigated by measuring viscosity of filler/bitumen mixes and low temperature cracking properties, respectively. Admixing of hydraulic filler was made by partly replacing the base material filler with hydraulic filler, thus keeping the overall filler content unchanged. Results show that resistance to moisture damage is improved by adding hydraulically active fillers. However, the hypothesis of finer gradings giving stronger response was not supported; all three portland cements gave very similar results. Furthermore, it seems that fractions of added hydraulic filler above 1–1.5 % (mass of total aggregate) do not further increase abrasion resistance. Essentially, no potential drawbacks, decreased workability or increased low temperature cracking, were noted. © 2013, RILEM. Source

Folli A.,Danish Technological Institute DTI | Folli A.,University of Aberdeen | Strom M.,Danish Technological Institute DTI | Madsen T.P.,Danish Technological Institute DTI | And 5 more authors.
Atmospheric Environment | Year: 2015

This paper reports the results of a field test study concerning the use of photocatalytic paving elements in Denmark to mitigate nitrogen oxides pollution. Prior to the installation, the photocatalytic concrete elements were tested in the lab, where conversions of NO reached values as high as 78% with low amount of NO2 formed. Once installed, nitrogen oxides concentration, temperature and relative humidity were monitored every minute for more than a year. The results of the field tests showed that under ideal weather and irradiation conditions, i.e. summer months, the monthly average NO concentration (based on day and night values) in proximity of the photocatalytic area was around 22% lower than the reference area. The close correlation between performance data and solar UV irradiance revealed that at such a latitude (55.68° N) adequate NO (hence NOx) conversions (monthly average) are achieved for total UV irradiance exceeding 600kJm-2day-1. Within this period, data relative to the solar noon showed instantaneous NO abatement in some cases higher than 45%, corresponding to a total NOx abatement higher than 30%. © 2015 . Source

Hokfors B.,Umea University | Hokfors B.,Cementa AB | Bostrom D.,Thermal Energy Conversion Laboratory | Viggh E.,Cementa AB | Backman R.,Thermal Energy Conversion Laboratory
Advances in Cement Research | Year: 2015

This paper describes the formation of a phosphorous belite solid solution and its impact on alite formation. A subsolidus phase relation for the ternary system silicon dioxide-calcium oxide-phosphorus pentoxide (SiO2-CaO-P2O5) is reported. The ternary system is based on Rietveld refinements of X-ray diffraction patterns from experimental tests. The overall picture is based on known phase diagrams, relevant Rietveld refinements models, stoichiometric relationships as a function of increasing phosphorus pentoxide concentration and vacancy theories for solid solutions of phosphate belites. A tool is developed for predicting the chemistry of the product as well as the chemistry during heating when producing Portland cement clinker. A thermodynamic database for phase chemistry calculations of clinkering reactions has been created and evaluated. Suitable compounds and solution species have been selected from the thermochemical database included in FactSage software. Some solution compositions have been uniquely designed to allow for the proper prediction of the cement clinker chemistry. The calculated results from the developed database for heating raw materials in cement clinker production and cooling of the product are presented in this paper. The calculated results provide a good prediction of the phases and quantities formed during heating and non-equilibrium cooling. The prediction of the amounts of alite, belite and aluminoferrite phases in the product according to the Scheil method is good. The temperature interval for the existence of all of the major phases is relevant. The thermodynamic data for a solution phase of alite with substituting ions of primarily magnesium oxide and phosphorus pentoxide would improve the predictability of the developed database. © 2015, Thomas Telford Services Ltd. All rights reserved. Source

Hokfors B.,Cementa AB | Hokfors B.,Umea University | Eriksson M.,NorFraKalk | Viggh E.,Cementa AB | Viggh E.,Umea University
Advances in Cement Research | Year: 2014

This paper presents a recently developed simulation model that can be used as a tool for evaluating sustainable development measures for cement and lime production processes. Examples of such measures are introducing new combustion technologies such as oxy-fuel combustion, using biomass fuel and using alternative materials in the raw material feed. One major issue when introducing process changes is the need to maintain product quality. In some ways, oxygen-enriched air combustion resembles oxy-fuel combustion. The model results were validated and found to be consistent with full-scale operational data for normal running conditions and for a full-scale test with oxygenenriched air. The model shows, for example, that with an additional 1500 m3/h of oxygen, fuel addition at the calciners can increase up to 108% and the raw material feed rate can increase up to 116% for a process with a raw meal feed of 335.5 t/h. Source

Lagerblad B.,Swedish Cement and Concrete Research Institute | Gram H.-E.,Cementa AB | Westerholm M.,Cementa AB
Construction and Building Materials | Year: 2014

Crushed rocks are, in general, more flaky and irregular in shape than natural aggregates. Especially granitic rocks display variable amounts or flaky free micas in the finer fractions when crushed. Moreover, the crushed rocks result in more fine material. Fillers can, in combination with superplasticizers and if the quality is appropriate be used to expand the paste phase of the concrete and thus be used to lower the cement consumption. To utilize the filler optimally one needs to evaluate the filler quality. There are several methods to evaluate the filler. In this article different methods both in regards to the material properties and the behavior in mortar and micro mortar tests are compared and evaluated. The analysis shows the importance of understanding the effect of both the particle shape and flakiness in the fine fractions and the properties of the material in the finest fraction i.e. <10 μm. This is very much related to the mineralogy of the rock. © 2013 Elsevier Ltd. All rights reserved. Source

Discover hidden collaborations