Hardened properties of high-performance printing concrete

This paper presents the results of experimental work on short- and long-term mechanical properties of high-strength concrete containing different levels of silica fume. The aim of the study was to investigate the effects of binder systems containing different levels of silica fume on fresh and mechanical properties of concrete. The work focused on concrete mixes having a fixed water/binder ratio of 0.35 and a constant total binder content of 500 kg/m3. The percentages of silica fume that replaced cement in this research were: 0%, 6%, 10% and 15%. Apart from measuring the workability of fresh concrete, the mechanical properties evaluated were: development of compressive strength; secant modulus of elasticity; strain due to creep, shrinkage, swelling and moisture movement. The results of this research indicate that as the proportion of silica fume increased, the workability of concrete decreased but its short-term mechanical properties such as 28-day compressive strength and secant modulus improved. Also the percentages of silica fume replacement did not have a significant influence on total shrinkage; however, the autogenous shrinkage of concrete increased as the amount of silica fume increased. Moreover, the basic creep of concrete decreased at higher silica fume replacement levels. Drying creep (total creep − basic creep) of specimens was negligible in this investigation. The results of swelling tests after shrinkage and creep indicate that increasing the proportion of silica fume lowered the amount of expansion. Because the existing models for predicting creep and shrinkage were inaccurate for high-strength concrete containing silica fume, alternative prediction models are presented here.

Effect of silica fume on mechanical properties of high-strength concrete

This paper presents the results of an investigation on the use of metakaolin (MK) as a supplementary cementing material to improve the performance of concrete. Two MK replacement levels were employed in the study: 10% and 20% by weight of the Portland cement used. Plain and PC-MK concretes were designed at two water–cementitious materials (w/cm) ratios of 0.35 and 0.55. The performance characteristics of the concretes were evaluated by measuring compressive and splitting tensile strengths, water absorption, drying shrinkage, and weight loss due to the corresponding drying. The porosity and pore size distribution of the concretes were also examined by using mercury intrusion porosimetry (MIP). Tests were conducted at different ages up to 120 days. The results revealed that the inclusion of MK remarkably reduced the drying shrinkage strain, but increased the strengths of the concretes in varying magnitudes, depending mainly on the replacement level of MK, w/cm ratio, and age of testing. It was also found that the ultrafine MK enhanced substantially the pore structure of the concretes and reduced the content of the harmful large pores, hence made concrete more impervious, especially at a replacement level of 20%.

Improving strength, drying shrinkage, and pore structure of concrete using metakaolin

Mechanical properties and durability performance of concretes with Limestone Calcined Clay Cement (LC3)

Drying shrinkage in alkali-activated binders – A critical review

Influence of key parameters on drying shrinkage of cementitious materials

Base granular materials are generally considered non-frost susceptible, which is an adequate assumption based on widely recognised frost criterions. However, their frost susceptibility is influenced by the presence of water that can unavoidably penetrate pavement structures. Even if unsaturated, freezing of unbound granular materials causes a net volume gain and an increase in water content which affect pavement performance during the spring period. This paper presents the results of a laboratory investigation on the effect of gradation on frost susceptibility, quantified with the segregation potential (SP), of three aggregate sources. The results suggest that SP values for all sources are strongly related to a fine particles state parameter. Moreover, the source influence was found to be described adequately with a parameter describing fine particles grain size distribution uniformity and fines specific surface. A model is proposed which combines gradation and mineralogical source effects on frost suscep...

Gradation influence on frost susceptibility of base granular materials

Turbulent flows, such as wind and runoff water, affect the integrity of base granular materials in paved roads shoulders and unpaved roads. This paper presents the results of a laboratory investigation on the effect of base granular gradations on their erosion resistance under turbulent flows. The tests were performed with the turbulent flow test designed to be used with conventional geotechnical laboratories equipment. Several gradations curves, within and outside the Quebec Ministry of Transportation grading envelope, were tested in order to examine the influence of the variation of base granular materials gradation characteristics on the erosion susceptibility. For unbound materials, it was found that properties related to material voids and the permeability of the material (uniformity coefficient, fine fraction porosity and estimated permeability) and property related to the fine particles content are strongly related to the erosion rates (ER) measured with the turbulent flow test. It was demonstrated...

Erosion susceptibility of granular pavement materials

Les materiaux granulaires de fondations de chaussees jouent un role structural important mais sont aussi affectes par l’environnement. La granulometrie et la source de granulats vont changer la facon dont ces materiaux reagissent a ces sollicitations. Cette etude cherche donc a evaluer la performance globale des materiaux granulaires face aux contraintes mecanique et environnementale. Le module reversible, la deformation permanente, la gelivite et la conductivite hydraulique ont ete mesures pour six granulometries et trois sources. Les resultats montrent l’effet significatif de la granulometrie et de la source dans le contexte d’un fuseau granulaire et permettent de suggerer des fenetres de performance granulometrique adaptees a des contextes de performance typiques. Ces effets de la granulometrie et de la source peuvent atteindre des facteurs 14 et 7 d’un point de sensibilite aux contraintes environnementales et des facteurs 3 et 2,5 d’un point de vue de la sensibilite aux contraintes mecaniques.

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Optimisation de la granulométrie des matériaux granulaires de fondation des chaussées

Unpaved roads in Canada are subjected to high wheel loads and environmental factors that significantly affect their performance. As part of a larger research project, the objective of this laboratory study was to compare the relative performance of various stabilization and dust lifting resistance agents to an untreated granular material commonly used as a base and wear course on unpaved roads. The performance is compared using California bearing ratio (CBR), resilient modulus, and unconfined compression strength tests. In addition, the surface sealing potential was measured on each specimen. The effects of compaction water content, product concentration, and the environment were investigated in this study. The results show that these variables have a significant impact on the performance measured, and it was possible to identify peak performance concentrations and performing products for the conditions tested.

Pascale Pierre

Papers

Influence of key parameters on drying shrinkage of cementitious materials

Gradation influence on frost susceptibility of base granular materials

Erosion susceptibility of granular pavement materials

Optimisation de la granulométrie des matériaux granulaires de fondation des chaussées

Laboratory study on the relative performance of treated granular materials used for unpaved roads