Sulphonated Melamine Formaldehyde Research Articles

Investigations on Improving the Compressive Strength of Sand Column with Cement Grout and Chemical Admixture

Grouting is one of the most commonly adopted technique for soil improvement and strengthening. Adding super plasticizers, accelerators, antifreezes, air entraining agent improves the performance of the cement grout. The performance of the grout while injecting in the sand column mainly depends on its fluidity property. Keeping it in mind about the water cement ratio, the strength of the sand column is studied in two sets of experiments one by sand column with cement grout only and another set by sand column with cement grout added with super plasticizers by varying the water cement ratios. Strength parameters like angle of internal friction and cohesion were obtained be direct shear test and unconfined compressive strength test on the specimens by varying the water content. An increase of 15.2kPa to 60.33 kPa was observed in the cohesion value for specimens with 10% water content and 13.8 kpa to 47.2kPa cohesion value observed in the specimens with 20% water content. The angle of internal friction was decreased from 360 to 160 for 10% water content whereas 300 to 100 for 20% water content. A series of experiments were conducted on the sand column grouted with cement and for different water cement ratios as 1.5, 2.0 and 2.5. Another set of experiments were repeated by adding 2%super plasticizer Sulphonated Melamine Formaldehyde (SMF). The experiment results revealed that at lower water cement ratio higher value of compressive strength was observed. It was also observed that the strength increases with curing period.

Effect of various liquid admixtures on cracking of plastic concrete

Plastic shrinkage cracking (PSC) is one of the earliest possible defects that can potentially ruin the performance of concrete structures with large exposed surfaces. PSC is mainly attributed to tensile stresses arising in concrete due to a combination of capillary pressure, and restraints provided by reinforcement and formwork. The adoption and use of several admixtures in modern-day concrete has been known to alter properties of both the fresh and hardened concrete. In this research, the adopted admixtures include a minimum and maximum dosage of a glucose-based retarder, calcium chloride-based accelerator, chloride free air entraining agent, lignosulphonate plasticiser, shrinkage-reducing admixture (SRA), poly carboxylate ether (PCE) based super-plasticiser, and a sulphonated melamine formaldehyde (SMF) based super-plasticiser. The experimental tests were conducted in a climate chamber with an ambient temperature of 40 °C, relative humidity of 10% and a wind speed of 20.2 km/h. By understanding the phenomenological and fundamental relationships of PSC when various admixtures are used in conventional and high-flow concretes, it was found that admixtures cause a substantial reduction in PSC severity. The respective admixtures led to a reduction in measured crack areas, capillary pressures, evaporation amount/rate, as well as settlement/shrinkage behaviours in both types of concrete. Compared to conventional concrete, high-flow mixes showed a greater reduction in the severity of PSC. The underlying working mechanism of these admixtures largely relates to the surface tension reduction ability.

Coupled effect of superplasticizer dosage and fly ash content on strength and durability of concrete

The incorporation of fly ash in concrete enhanced the durability of portland cement concrete more effectively. Fly ash is incorporated as a mineral admixture because of its advantageous properties like pozzolanic reaction and pore refinement. At the point when fly ash is added in concrete, calcium hydroxide, liberated during cement hydration, reacts with the reactive silica present in fly ash and forms calcium silicate hydrate(C-S-H) gel. This research investigates the influence of fly ash in conjunction with four different superplasticizers (SP) namely Polycarboxylate ether (PCE), Lignosulphonate (LS), Sulphonated Melamine Formaldehyde (SMF) and Sulphonated Naphthalene Formaldehyde (SNF) and on the mechanical and durability properties of concrete. Concrete was made with different levels of class F flyash replacement (0,15, 25, and 35% by mass) of cement, the w/c ratio were maintained constant as 0.37 and the superplasticizer dosage corresponding to saturation dosage. The saturation dosage of superplasticizer is measured by conducting marsh cone and minislump tests. The mechanical and durability properties tested were compressive strength, splitting tensile strength and Sorptivity. PCE based superplasticizers are found to be more effective. Modification in the mechanical by increase in later age strength and durability properties by increase of the concrete was observed with the addition of fly ash and superplasticizer in control mix

Microstructural and rate of water absorption study on fly-ash incorporated cement mortar

Today durability is the most concerning factor in the construction field. Durability and strength are mainly controlled by microstructure of the concrete. Dense microstructure with less interconnected pores results in good strength and durable concrete. A dense microstructure can be obtained by providing good compaction, curing and by the use of mineral admixtures. This paper deals with the study on the effect of fly ash addition and superplasticizer dosage and its family in improving the strength, microstructure and durability of mortar. For this purpose mortar is prepared at a water to cement ratio of 0.37 with ordinary portland cement, class F fly ash at different percentage replacement to cement such as 0%, 15%, 25%, and 35% and superplasticizer. The superplasticzer from four different family such as Polycarboxylate ether (PCE), Lignosulphonate (LS), Sulphonated Naphthalene Formaldehyde (SNF) and Sulphonated Melamine Formaldehyde (SMF) is also used in this study. Durability of the mortar is determined by checking the 28th day rate of water absorption in mortar specimen and also by checking the size and connectivity of the pores by means of microscopic study in hardened concrete. There is decrease in 28th day compressive strength for mortar specimen with all levels of fly-ash replacement was observed in this study. Improvement in the compressive strength of the mortar compared to control specimen were observed with the addition of superplasticizer in all levels of addition of fly-ash. A good correlation between the pore size and compressive strength were also observed in this study

Characterising cement–superplasticiser interaction using zeta potential measurements

The zeta potential generated at the interface between cement particle surfaces adsorbed with superplasticisers have been studied using electroacoustic technique, which is capable of measuring zeta potential at high concentrated suspensions. The study has been undertaken to examine the differences in the magnitude of the zeta potential for ordinary Portland cement (OPC) and Portland pozzolanic (fly ash) cement (PPC) pastes along with the differential impacts of different types of superplasticisers on both the varieties of cement pastes. In the latter context, the effects of three different types of superplasticisers namely Ligno Sulphonate (LS), Sulphonated Melamine Formaldehyde (SMF) and Sulphonated Naphthalene Formaldehyde (SNF) have been specifically studied. The results show that the cement pastes with PPC shows better dispersion when compared with the OPC. The paper also endeavors to unfold the relationship and significance of cement interaction with three different superplasticisers.

Influence of solfonated melamine formaldehyde condensate on the quality of building blocks production by extrusion of cement–clay pastes

The extrusion of cement–clay pastes to manufacture building blocks by cold stabilization of clays by cement is investigated. Based on the pressure and the torque values measured during paste preparation and extrusion, an operative window of concentration of water and sulphonated melamine formaldehyde (SMF) fluidizer suitable to obtain simple and complex building blocks is identified: for pastes with clay/cement ratio 2.6:1 the water content ranges between 24% and 29% w/w for 6% w/w SMF and between 29% and 33% for 0% w/w SMF. Extruded items have been submitted to bending stress resistance tests to evaluate the mechanical properties of clay stabilized by cement and to identify the paste formulations with the highest resistances. To the best a 25% increase in mechanical properties is achieved by applying a curing treatment at 35 °C and 90% humidity for 96 h. However based on the results of tests of frost resistance and resistance to water contact, the clay–cement blocks do not offer so far an alternative to conventional bricks.

Physico-chemical characteristics of chemically activated cement containing boron

The use of colemanite ore waste (CW) containing boron as a cement replacement material increases the long-term strength of the concrete. Despite this benefit, the use of CW is limited due to the low-early strength of the CW concrete. The study reported below intended to eliminate this problem. The experimental part comprises two stages: in the first stage the possibility of using CW instead of natural gypsum has been investigated through several tests. In the second stage, a number of chemical activators, namely, sulphonated melamine formaldehyde (SMF) condensates, sulphonated naphthalene formaldehyde (SNF) condensates, Na 2 SO 4 , and calcium chloride were used. The results showed that replacement of natural gypsum by CW results in an acceptable initial and final setting time of cement and increases the compressive strength of the mortar at long term. The addition of chemical activators into the system accelerated pozzolanic reaction and considerably increased early strength of the mortars. The results also indicate that chemical activators not only alter the rate of cement paste hydration, but the microstructure of mortar as well.

Effect of superplasticizers on the rheological properties of fly ash suspensions containing activators of the pozzolanic reaction

Rheological studies have been carried out on the effect of a superplasticizer from the sulphonated melamine formaldehyde (SMF) group upon the properties of fly ash suspensions containing a small quantity of mineral admixtures such as cement, lime and gypsum. The superplasticizers' efficiency has appeared to depend greatly on the admixture used. The highest liquefaction degree was found in fly ash suspensions containing both cement and gypsum together and the next it was, when only cement was added. These suspensions exhibit features of a newtonian fluid of low plastic viscosity, when the water to solid ratio (w/s) is 0.3 and a superplasticizer has been used. However, fly ash suspensions with lime, under analogous conditions, produce a considerable increase of the rheological parameters. This may be explained by the effect of the very high specific surface area of hydrated lime upon the consistency of fly ash suspensions.

Influence of superplasticizer on aqueous phase composition in the CaO-Al2O3-SO3-H2O system

The effect of three different superplasticizers on the formation of ettringite during the reaction of Al2(SO4)3·16H2O with Ca(OH)2 and on the hydration of C3A with CaSO4·2H2O was investigated in relation to aqueous phase compositions. The superplasticizers comprised a sulphonated melamine formaldehyde condensate (SMF) and two sulphonated naphthalene formaldehyde condensates (SNF) , with different counter-ions (Na and Ca). The addition of superplasticizer altered to varying extents the aqueous compositions, and this was dependent on the reaction system, the degree of reaction and the type of superplasticizer used. The SNF superplasticizer as the Na salt produced solution characteristics different to those produced by either the Ca salt or the SMF superplasticizer. Compositional variations occurring in the aqueous phases as a function of time, both with and without super plasticizer, have in part been explained in relation to that of the solid phase composition.

Early hydration of tricalcium aluminate-gypsum mixtures in the presence of sulphonated melamine formaldehyde superplasticizer

Synthetic tricalcium aluminate and gypsum mixtures containing o, 0.10 and 0.25 wt. % sulphonated melamine formaldehyde (SMF) have been prepared to a constant water:solid ratio of 2.0 and hydrated at 20°C. The hydration processes have been studied by calorimetry, differential thermal analysis, X-ray diffraction and electron microscopy. By 72 hr all mixtures had reached essentially the same phase distribution but the SMF content strongly influenced reaction pathways. Absorption of SMF is largely responsible; it bulks out and helps stabilize ettringite precursor. The SMF content and reaction sequence markedly affect the microstructure of the set pastes.

Crystallization of calcium hydroxide in the presence of sulphonated melamine formaldehyde superplasticizer

Calcium hydroxide (portlandite) is one of the main solid constituents of hydrated Portland cement. It is not present in dry Portland cement clinker, but develops during the course of setting and strength gain, mainly as the tricalcium silicate and dicalcium silicate phases of clinker react with water. The mechanism of its formation is clear. Within a few seconds of mixing cement with water, the aqueous phase becomes supersaturated with respect to Ca(OH)2. Nucleation soon occurs, and thereafter free Ca(OH)2 is present; continuing hydration of solid phases maintains the aqueous phase at saturation. Thus, Ca(OH)2 forms by a solution-precipitation mechanism [1]. A completely hydrated cement paste contains 20-25% Ca(OH)2. Although this is intimately mixed with other phases [2], notably a gel-like calcium silicate hydrate designated in shorthand nomenclature C-S-H, the crystalline Ca(OH)2 may be readily observed by scanning electron microscopy (SEM) and quantitatively measured by selective dissolution, by X-ray diffraction or by thermogravimetric analysis (TGA). The high Ca content of modern Portland cements leads to high Ca(OH)2 contents which, in turn, has led to speculation concerning the contribution that it makes to the strength of pastes, mortars and concretes. The crystal structure of Ca(OH)2 is well known; it is a layer lattice structure in which individual symmetrical layers are electrically neutral, each having the net composition Ca(OH)2. Thus, layers are bonded together only by van der Waals or hydrogen bonds, with the result that the pseudo-hexagonal crystals have perfect basal cleavage. Of course, the gel matrix is itself hydrogen bonded, but in an irregular manner, so it does not readily propagate fracture. Thus, it would appear that Ca(OH)2 crystals may be a potential strength-limiting factor of cement paste. A wide range of organic and inorganic admixtures are added to cements for a variety of purposes: to increase fluidity, to accelerate or retard setting, as waterproofers, etc. [3]. The colloidal nature of the gel phase is very sensitive to the presence and amount of these additives. However, it is less well known that the presence of these agents also influences the crystal size and morphology, and hence other properties, of the more crystalline components. This was suspected on the basis of previous studies, suggesting that the presence of sulphonated melamine formaldehyde (SMF; widely used as a superplasticizer) altered the morphology 712 and size of Ca(OH)~ crystals [4]. This letter reports the effect of SMF superplasticizer on the morphology and crystallization of Ca(OH)2 from simulant cement pore fluids. 5 ml 0.024 ~ CaCI2 was mixed with 1 ml 0.24 NaOH in a plastic centrifuge tube and sealed to avoid carbonation. To the solutions was added 0, 0.5, 1.0 and 2.0 wt % SMF. This produced about 6 ml of a solution, which was found on analysis to be about 20 mM Ca 2÷ and 40 mM OH-, roughly equivalent to the saturation solubility of Ca(OH)2 in water at 18-20 °C. After 3 days the solutions were centrifuged to separate the solid, and excess water was removed. The Ca(OH)2 crystals were washed with isopropanol twice and kept under isopropanol until they were dried before examination by SEM. In another experiment, after centrifuging and removing excess water, Ca(OH)2 crystals from the same compositions were washed twice with a very small amount of deionized water and kept in isopropanol to be used for infrared analysis. Fig. 1 shows the SEM micrographs of the Ca(OH)z crystals obtained from the control solution: the SEM micrographs of the Ca(OH)2 crystals from the solution with 1 and 2% SMF are shown in Figs 2 and 3, respectively. The micrographs clearly indicate how SMF modifies the crystal morphology of the Ca(OH)> The crystals from the control solution develop a pseudo-hexagonal, prismatic morphology. However, in the presence of 1% SMF, well-shaped flattened pseudo-hexagonal plates form; occasional growth spirals are visible on sur

The Adsorption of Cement Superplasticizers on to Mineral Dispersions

The adsorption of polymeric sulphonated naphthalene formaldehyde (SNF) and sulphonated melamine formaldehyde (SMF) on to titanium dioxide and calcium carbonate has been measured in aqueous media. The magnitude of these adsorptions is strongly dependent on electrostatic interaction irrespective of the pH value. This result has been established by studying the adsorption of the polyelectrolytes from solutions of different composition. The calcium ion plays a prominent role in the process of adsorption, especially at high pH where electrical interactions do not favour the reaction. The polymeric nature of the fluidizing agents is demonstrated by an increase in adsorption with molecular weight and by adsorption/desorption experiments where the reaction has been shown to be irreversible. The amount adsorbed at maximum coverage does not depend on the nature of the mineral, but mainly on electrical interactions between the monomer units.

Adsorption characteristics of sulphonated melamine formaldehyde condensates by high performance size exclusion chromatography

High performance size exclusion chromatography has been used to measure the average molecular weight and molecular weight distribution of sulphonated melamine formaldehyde condensate admixtures. The method was then used to study the adsorption of these molecules on to the surfaces of cement particles. It was found that the molecules in the higher molecular weight fractions preferentially adsorbed on to the cement particles.

Quantitative analysis of sulphonated melamine formaldehyde superplasticizer in cement

Qualitative identification and quantitative analyses of superplasticizers are conventionally carried out by ultraviolet spectroscopy. This method is satisfactory for solutions of near-neutral pH, but for sulphonated melamine formaldehyde (SMF) materials it is unsatisfactory at higher pH values. In particular, the alkaline nature of cement gives rise to a high concentration of hydroxyl ions and this results in interference. The sample may be neutralized with acid, but this also results in ion interference. Spectrofluorimetry is shown to be a more satisfactory method: it can be used for SMF in solution in either fresh or set cement mixes with only minor pH adjustment. The procedures involved are described and as an example of the application of the method the sorption of SMF on freshly-mixed Portland cement and its hydration products is discussed.

Influence of sulphonated melamine formaldehyde superplasticizer on cement hydration and microstructure

This Paper assesses the role of sulphonated melamine formaldehyde (SMF) in cement. It is shown that the data given in the literature are frequently in error due to inappropriate analytical procedures. Initial rapid sorption of SMF occurs, probably on an ettringite precursor. This is followed by partial desorption of SMF, but eventually the alkaline nature of the cement pore fluid precipitates a chemically altered derivative for which some analytical data are given. The retarding effect of SMF is pronounced at 20°C but diminishes or disappears with increasing temperature up to 55°C. In comparable paste specimens SMF reduces the mean size of Ca(OH)2 crystallites and alters their morphology, but promotes the growth of larger ettringite crystals.

Control of slump loss in superplasticized concrete

The slump loss characteristics of concrete containing different amounts of sulphonated melamine formaldehyde (SMF) admixed with two types of polymers were investigated. The addition of 2% polymer to SMF retarded the slump loss. The setting times although retarded were found to satisfy the requirements of the ASTM standards.

Air entrainment in mortars and concrete: The effect of superplasticizer/salt combinations

The use of salt-saturated solutions in mixing super plasticized mortars and concretes will sometimes lead to the entrainment of large quantities of air (in excess of 20 per cent, often as high as 50 per cent). The author describes a test to quantify the potential of various superplasticizers to entrain air when used in salt-containing mortars and concrete. A solid form of a sulphonated naphthalene formaldehyde condensate (SNFC) was mixed with saturated brine solution, with and without defoaming agents, and the level of foaming was measured. The test was repeated using 20 per cent active liquid sulphonated melamine formaldehyde condensate (SMFC) in place of SNFC. In the case of SNFC, reaction with the salt produced a large amount of relatively stable foam, only partially controlled by defoamers. In the case of SMFC there is less foaming and it can be effectively controlled with a defoamer. The test described is a simple one which allows quick determination of the potential for foaming. (TRRL)