Polymer concrete, correlations between properties

Has been adopted new method for determining the fluidity concrete with polymers. In the research were used three types of polymer: epoxy resin - at a rate of 10%; polyurethane - at a rate of 10% methylcellulose - at a rate of 0.6%. The experimental results showed that the same water/cement material behaves differently depending on the polymer used. Moreover, epoxy resin gives significant improvements in workability and strength. It was found that the polymer influence positively the mechanical properties and concrete workability. Were performed mycroscopical investigations on reinforced concrete structures

Self-compacting concrete: a comparison between the workability properties, density, porosity and mechanical properties

This paper highlights some connections between the workability properties of self-compacting concrete and the density of the concrete mass and between mechanical properties of compression strength and porosity of concrete samples investigated at 28 days of free curing. Also are presented properties of raw materials used in this study

Properties of polymer modified concrete in fresh and hardened state

It was carried out a study on the properties of polymer modified concrete (PCM) in fresh and hardened state. It was used three types of polymers: epoxy resins, polyurethane and methylcellulose in different percentages and different water cement ratio. The main objectives was to improve workability and rheological behavior of these mixtures in fresh state and mechanical strength tests on hard concrete. Has been investigated the polymer influence on compression strength and flexural strength and analyzing the time evolution of these strengths and participation of polymer in the microstructure formation.This work was partly financed by the European Social Fund through the POSDRU/CPP107/DMI1.5/S/77497 Program for PhD. Studen

Special self-compacting concretes

The paper presents experimental investigations on the special self-compacting concretes, in different compositions. Also, in this paper highlights the influence of super plasticizers additives use upon the mechanical, structural and chemical properties of selfcompacting concretes improving. During these laboratory investigations were made samples of self-compacting concrete with diferente compositions, on which were performed workability and mechanical tests (compressive strength), as well as, structural attempts (microscopy, density, porosity tests)

Polymer effect on the rheological properties of the PPC blends

A study was carried out on rheological properties of PCC (polymer concrete with cement) fresh blends containing polymers soluble in water and epoxy resins. The work refers to determine yield and plastic viscosity of fresh concrete according to the polymer weight. It was used methilcellulose as polymer and an epoxy resin, in different proportions. It was also carried out physico-mechanical tests on hard concrete. The study revealed that the addition of polymer matrix to produce PCC concrete, has a pronounced effect on the rheological property of freshly mixed. Influence of polymers on these properties is due to both the content of colloidal particles, and the amount of air present in the mixture due to stirring and mixing the paste.Changes that they produce polymer emulsions are found in terms of both flow and the viscosity value, and decreasing. This allows the scientifically and technologically, as they are controlled and adapted to specific requirements.Compressive strength of epoxy resin blends were found to be higher than those of mixtures containing methylcellulose

Lower Spectral Branches of a Particle Coupled to a Bose Field

The structure of the lower part (i.e. $\epsilon$-away below the two-boson threshold) spectrum of Fr\"ohlich's polaron Hamiltonian in the weak coupling regime is obtained in spatial dimension $d\geq 3$. It contains a single polaron branch defined for total momentum $p\in G^{(0)}$, where $G^{(0)}\subset {\mathbb R}^d$ is a bounded domain, and, for any $p\in {\mathbb R}^d$, a manifold of polaron + one-boson states with boson momentum $q$ in a bounded domain depending on $p$. The polaron becomes unstable and dissolves into the one boson manifold at the boundary of $G^{(0)}$. The dispersion laws and generalized eigenfunctions are calculated

Lower Spectral Branches of a Spin-Boson Model

We study the structure of the spectrum of a two-level quantum system weakly coupled to a boson field (spin-boson model). Our analysis allows to avoid the cutoff in the number of bosons, if their spectrum is bounded below by a positive constant. We show that, for small coupling constant, the lower part of the spectrum of the spin-boson Hamiltonian contains (one or two) isolated eigenvalues and (respectively, one or two) manifolds of atom $+ 1$-boson states indexed by the boson momentum $q$. The dispersion laws and generalized eigenfunctions of the latter are calculated

Canagliflozin and renal outcomes in type 2 diabetes and nephropathy

BACKGROUND Type 2 diabetes mellitus is the leading cause of kidney failure worldwide, but few effective long-term treatments are available. In cardiovascular trials of inhibitors of sodium–glucose cotransporter 2 (SGLT2), exploratory results have suggested that such drugs may improve renal outcomes in patients with type 2 diabetes. METHODS In this double-blind, randomized trial, we assigned patients with type 2 diabetes and albuminuric chronic kidney disease to receive canagliflozin, an oral SGLT2 inhibitor, at a dose of 100 mg daily or placebo. All the patients had an estimated glomerular filtration rate (GFR) of 30 to <90 ml per minute per 1.73 m2 of body-surface area and albuminuria (ratio of albumin [mg] to creatinine [g], >300 to 5000) and were treated with renin–angiotensin system blockade. The primary outcome was a composite of end-stage kidney disease (dialysis, transplantation, or a sustained estimated GFR of <15 ml per minute per 1.73 m2), a doubling of the serum creatinine level, or death from renal or cardiovascular causes. Prespecified secondary outcomes were tested hierarchically. RESULTS The trial was stopped early after a planned interim analysis on the recommendation of the data and safety monitoring committee. At that time, 4401 patients had undergone randomization, with a median follow-up of 2.62 years. The relative risk of the primary outcome was 30% lower in the canagliflozin group than in the placebo group, with event rates of 43.2 and 61.2 per 1000 patient-years, respectively (hazard ratio, 0.70; 95% confidence interval [CI], 0.59 to 0.82; P=0.00001). The relative risk of the renal-specific composite of end-stage kidney disease, a doubling of the creatinine level, or death from renal causes was lower by 34% (hazard ratio, 0.66; 95% CI, 0.53 to 0.81; P<0.001), and the relative risk of end-stage kidney disease was lower by 32% (hazard ratio, 0.68; 95% CI, 0.54 to 0.86; P=0.002). The canagliflozin group also had a lower risk of cardiovascular death, myocardial infarction, or stroke (hazard ratio, 0.80; 95% CI, 0.67 to 0.95; P=0.01) and hospitalization for heart failure (hazard ratio, 0.61; 95% CI, 0.47 to 0.80; P<0.001). There were no significant differences in rates of amputation or fracture. CONCLUSIONS In patients with type 2 diabetes and kidney disease, the risk of kidney failure and cardiovascular events was lower in the canagliflozin group than in the placebo group at a median follow-up of 2.62 years

Study on Hydration and Strengthening of High Alumina Cements

International audienceRefractory concretes based on aluminous cements are used with great success in areas where high temperatures are required. The mineralogical composition of the high alumina cement is the main factor which gives the physical and mechanical properties at high temperatures of refractory monolithic materials. It is therefore desirable to use high alumina cements based on mineralogical compounds with high refractoriness, because in the end those beneficial properties can be found in the final product-refractory concrete. The aim of this paper is to design, realize and characterize different compositions of high alumina cements based on mineralogical compounds with the highest refractory from the CaO-Al 2 O 3 binary system (i.e. CA, CA 2 , and CA 6), and to find ways of hydraulic activation of calcium hexa aluminate, also