Ina Pundienė

Investigating the hydration of deflocculated calcium aluminate cement-based binder with catalyst waste

The hydration of the binder, consisting of calcium aluminate cement (CAC) with Al2O3 >70% and with or without the additives of the FCC catalyst waste and polycarboxylate deflocculant Castament FS-20, is investigated. The methods of calorimetry, thermal analysis, XRD, electrical conductivity, SEM, as well as ultrasonic wave velocity measuring and bending strength evaluation are used. The results of the investigation show that the FCC catalyst as well as polycarboxylate deflocculant, are active additives, influencing the CAC binder’s hydration process. In the structure of the hardened binders, certain amounts of unhydrated CAC minerals, CA, and CA2, and the hydration products, such as CAH10, C2AH8 and the amorphous AH3, are found. However, in the binder with a deflocculant, there are smaller amounts of CAH10 and the amorphous AH3, though the amount of C2AH8 is higher than that in the binder without a deflocculant additive. It has been found that in the case, when the FCC catalyst and deflocculant are simultaneously used, the FCC catalyst produces a positive effect on the formation of the CAC binder’s structure, increasing its mechanical strength. The results obtained in this article allow to predict that the FCC catalyst and deflocculant simultaneously used as the additives to the CAC binder, will enable to control the hydration process of the binder.

Effect of different pozzolana on hardening process and properties of hydraulic binder based on natural anhydrite

Abstract The study deals with peculiarities of hydration and development of hardening structure as well as durability properties pertaining to composite anhydrite cement pozzolana binder (ACP) with different pozzolana (P). The properties of P have an effect on ACP hydration, structure development and durability properties. This effect is different than that in cement pastes. Investigations were performed with known P: natural opoka (O) and microsilica (MS), also with production waste of mineral wool – cupola dust (CD), which is famous for high fineness and amorphous structure of particles. It was established that the activity of P compounds contained in CD was very high making this waste suitable for ACP as a P component. In ACCD samples, one could observe the most intense hydration; and after a longer inductive period, the development of hardening microstructure was more rapid than in ACMS or ACO; furthermore, a remarkably higher strength was reached. The slowest hydration and structure compacting as wel...

Investigation of Hydration Features of the Special Concrete with Aggregates of Various Metal Particles

This study presents an analysis of various size metal particle waste (MP) influences on Portland cement (PC) paste hydration course, concrete sample structure densification during hardening and physical-mechanical properties. Investigations have shown that MP filler accelerates maximum heat release rate in PC pastes. MP intensifies structure development in the early phase, but slows it down in later PC hydration period. After 28-days of hardening the compressive strength of the concrete samples without MP filler is about 20% higher than of samples with MP. When in concrete composition microsilica and MP fillers are used together, compressive strength of concrete sample composition is up to 50% higher than of samples with MP filler only.

Portland Cement Based Lightweight Multifunctional Matrix with Different Kind of Additives Containing SiO2

Additives containing SiO2 (ACS) and having pozzolanic properties such as metakaolin (MK), microsilica (MS) and milled autoclaved aerated concrete waste (MAACW) are promising materials for partially replacement of Portlandcement (PC) in matrix of lightweight building materials. Studies have shown that SA effects on the hydration process of PC matrix. The highest wetting heat release rate values were obtained using MS additive, and the lowest a mix of MS and MK additives. In a mix with both MS and MK additives, the maximal value of heat release rate was reached after 10 h and in a mix with MS additive after 13 h. MS additive extends while MK additive accelerates the hydration process of PC. The most effective plasticizer (P) was chosen according to the study of dynamic viscosity (DV) of PC matrix. It was fixed that surfactant (SU) in amount of 0.03 % (from PC) reduces the density of matrix about 30 % compared with the density of matrix without SU. Increased quantity of MAACW (from 5 to 15 % from PC) causes in increase of compressive strength of PC matrix (after 28 days curing) from 19 to 47 MPa.

Investigation of Composite Deflocculant Influence on the Properties of the Refractory Castable with Chamotte Aggregate

The influence of different types of deflocculants, PCE and sodium tripolyphosphate, on the rheological properties of the cement matrix was studied. It was established that composite deflocculant consisting of sodium tripolyphosphate and PCE Castament FS 20 provides the best rheological properties of the cement matrix and affects the composition of the hydration products. During the drying process of matrix with composite deflocculants mineral stratlingite additionally formed, which contributes to increment of strength properties. Comparative studies of refractory castable strength properties with chamotte aggregate showed that the compressive strength of concrete samples with composite deflocculants after hardening and after drying and burning is almost two times higher than the strength of samples with separate deflocculants.

A Study of Rapeseed Oil-Based Polyol Substitution with Bio-based Products to Obtain Dimensionally and Structurally Stable Rigid Polyurethane Foam

Water-blown polyurethane foams from low functionality polyols are characterized by intensive shrinkage, high density, post blowing, and longer demold time. These drawbacks can be partially, or fully, eliminated by varying chemical parameters of the main components. Therefore, an aliphatic polyester rapeseed oil-based polyol was modified with bio-based glycerin (RGL) and propylene glycol (RPG). The impact of the molecular weight and hydroxyl value of the blends were evaluated by testing obtained bio-based polyurethane foams. Compared to RGL-based foams, RPG-modified foams had the strictest standard (EN 13165) requirements regarding dimensional stability. These foams demonstrated a reduced apparent density from 12.6 to 20.8%, a faster foam curing capability by 47%, and the shortest demold time due to the open cell structure. The RGL modified foams had better cross-linking capability, slower ageing of thermal conductivity, and an increased compressive strength of 82.7% compared to the non-modified foam.

The influence of carbon nanotubes on the properties of water solutions and fresh cement pastes

It is known, that the properties of cement-based materials can be significantly improved by addition of carbon nanotubes (CNTs). The dispersion of CNTs is an important process due to an extremely high specific surface area. This aspect is very relevant and is one of the main factors for the successful use of CNTs in cement-based materials. The influence of CNTs in different amounts (from 0 to 0.5 percent) on the pH values of water solutions and fresh cement pastes, and also on rheological properties, flow characteristics, setting time and EXO reaction of the fresh cement pastes was analyzed in this work. It was found that the increment of the amount of CNTs leads to decreased pH values of water solutions and fresh cement pastes, and also increases viscosity, setting times and EXO peak times of fresh cement pastes.

Influence of Plasticizer Amount on Rheological and Hydration Properties of CEM II Type Portland Cements

The article analyzes the effect of plasticizer (based on polycarboxilates) amount (0.3 - 1.2% wt. of cement) on the rheological and hydration properties of two Portland cements pastes: CEM II/A-S 42.5N and CEM II/A-LL 42.5N. Increase of plasticizer amount reduces viscosity of CEM II/A-LL 42.5N cement paste from 3 to 12 times, where viscosity of CEM II/A-S 42.5N cement paste reduces from 5 to 20 times. The optimum plasticizer dose (0.3%) in case of CEM II/A-S 42.5N and (1.2%) in case of CEM II/A-LL 42.5N was established. Calorimetry studies have shown that plasticizer reduces the wetting heat release rate in CEM II/A-LL 42.5N cement twice and in CEM II/A-S 42.5N cement - by 25%. Plasticizer prolongs the maximum heat release rate time by 16 h in CEM II/A-LL 42.5N samples and reduces heat release rate by 19%. In CEM II/A-S 42.5N cement samples plasticizer prolongs maximum heat release rate time by 14.5 h and increases heat release rate by 15%. The goal of this study is to analyze the effect of the dosage of the most widely used plasticizer on solubility characteristics, rheological and hydration properties of two cements CEM II/A-S 42.5N and CEM II/A-LL 42.5N to establish the optimum dose of plasticizer in cements pastes.