Determining the physical properties of polymer in different admixtures used for self-compacting cement paste by ESEM (original) (raw)
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Materials
The addition of Superabsorbent Polymer (SAP) decreases the effect of autogenous shrinkage present in pastes, mortars, and concretes. In this study we investigated the influence of the addition of SAP in self-compacting cement paste mixtures. Eighteen 5 × 10 cylindrical specimens were molded in all, three for each mixture (CPII base, CPII 0.15%SAP/600μm, CPII 0.15%SAP/800 μm, CPV base, CPV 0.15%SAP/600 μm, CPV 0.15%SAP/800 μm). Two types of cement were tested, CP II-Z and CP V-ARI with 0.15% of weight replaced per two diameters of SAP (600 μm and 800 μm). The samples followed the standards required. Mini slump tests were carried out in the fresh state, and uniaxial compressive strength, elastic modulus, specific mass, absorption, and air content in the hardened state after 28 days. The results obtained show the SAP is high indicated to replaced cement in small % of weight i/to fresh and hardened paste. Likewise, the group mix n° 3 composed of CPII 0.15% of SAP with 800 μm diameter pr...
2013
Four different Polycarboxylate ethers (PCE) known a s superplasticizers were tested for their rheological performance in cement paste. The struct u e varies in the side chain and charge density of the molecules and the functional group. The investigations were focused on variation of some parameters (e.g. C 3A-conten and retarding agent) in cement type CEM I 42.5 R and their influences on the activity of PCEbased plasticizers. The rheological properties were measured using a rotation viscomete r. Using a defined program, the rheological curves of the cement paste at defined p hysical condition were plotted to show the relationship between shear rate and yield. Saturati on points (maximum PCE-concentration) of each PCE were determined. The plastic viscosity and the yield value were calculated for each cement variation and PCE-combination. The results s how the differences in PCE activities. PCE2 with short side chain and low charge density r educes the viscosity and the yield value f...
Effect of MWCNT and PCE plasticizer on the properties of cement pastes
IOP Conference Series: Materials Science and Engineering, 2019
Polycarboxylate ether (PCE) plasticizer possesses by high water-reduction capability of about 30-40%. Despite the superior water reduction capability, the high dosages of PCE may cause the bleeding in cement systems, which is not suitable for high workability and self-compacting concrete. The current research is devoted to the studying of multi-walled carbon nanotubes (MWCNT) suspension prepared in combination with PCE plasticizer on the rheological properties of cement pastes. The bleeding of cement pastes modified by different dosages of MWCNT was estimated as well. The increase of yield stress in 3.7 and 3.5 times was obtained for cement paste modified by MWCNT suspension in dosage of 0.12% by weight of cement (bwoc) in 5 and 120 min after cement paste mixing, respectively. The increase of plastic viscosity in 2.95 and 1.55 times was obtained for cement paste modified by MWCNT suspension in dosage of 0.12% bwoc in 5 and 120 min after cement paste mixing, respectively. Modificatio...
The effect of terpolymer admixtures on physico-mechanical properties of cement pastes
International Journal of Basic and Applied Sciences, 2014
Three composition ratios of methyl methacrylate; (MMA), 2-ethylhexyl acrylate, (2-EHA), and methacrylic acid; (MAA) terpolymers were prepared via emulsion polymerization. The polymerizations were carried out at 80°C using potassium persulfate (KPS) as initiator. The terpolymers were characterized by FT-IR and 1 HNMR. The influence of these terpolymers on the physico-mechanical properties of Portland cement (PC) pastes was determined using various characterization methods such as rheological and consistency. The results showed that as the ratio of MMA increased in the terpolymers, the water of consistency decreased, while the initial and final setting times were elongated with the concentration of 2-EHA increases. The workability, combined water and compressive strength of the hardened cement pastes were raised, whereas the water absorption was reduced with increasing quantity of MMA in prepared terpolymers and leads to the reduction in the porosity of the cement pastes, it is due to generation polymer films between cement granules. The SEM images confirmed that the addition of the terpolymers to the cement pastes affected on shape or morphology and size of crystals of the formed hydrates.
International Journal of Basic and Applied Sciences, 2015
Physico-mechanical properties of cement pastes were studied by setting time, combined water, compressive strength, SEM as well as porosity in presence of blend polymers. Blend polymers were used based on polyvinyl alcohol and carbamide with blend ratios 20/80, 40/60 and 80/20 respectively. The addition of blend polymers to cement pastes affected the physico-mechanical properties of cement pastes. As the content of carbamide in the polymer blends decreased, the water of consistency decreased, whereas the setting times (initial & final) were elongated. The combined water content and compressive strength of the hardened cement pastes were increased at all ages of hydration. The SEM images showed that the addition of these polymers to cement material improves the dispensability and workability of cement pastes.
International Review of Applied Sciences and Engineering
For the past few decades innovation in construction material has grown a lot. This leads to special concrete such as self-compacting concrete, geopolymer concrete, self-healing concrete, etc. To prepare a special concrete apart from regular concreting material some sort of special materials was also needed, like mineral and chemical admixtures. Hence it is necessary to study the effect of these admixtures in cement paste and mortar before studying the same in concrete. Hence an attempt is made to study the effect of mineral and chemical admixtures in the fresh and hardened properties of cement paste and mortar. For this study ultrafine natural steatite powder is taken as mineral admixture and polycarboxylic based superplasticizer and glenium stream 2 were taken as chemical admixtures. Ultrafine natural steatite powder was used as additive to cement in various percentages like 0%, 5%, 10%, 15%, 20% and 25%. Superplasticizer and viscosity modifying admixture were taken as 1.5% and 0.5...
Hydro-mechanical properties of fresh cement pastes containing polycarboxylate superplasticizer
Cement and Concrete Research, 2013
A novel oedometric cell has been used to study the permeability and compressibility of freshly made cement-based pastes. This cell allows rapid tests providing an accurate estimation of compressibility, permeability and thus consolidation coefficient with no cement hydration effect. The influence of the test-induced flow on the results obtained is discussed in order to find an optimized procedure. The effects of common mix-design parameters such as W/C ratio and polycarboxylate amount, is discussed. Especially, it is shown that polycarboxylate high range water reducing admixture reduces the cement paste permeability and does not influence the compressibility of the cement grains network. The effect of W/C and admixture amount on paste bleeding is also discussed.
Physicochemical characteristics of some polymer cement composites
Materials Chemistry and Physics, 2001
The electrical conductivity of cement pastes can give an indication of the initial hydration of the cement pastes and early formation of products. In this study, sulphate-resisting cement (SRC) pastes were prepared with different doses of two synthesised admixtures, namely phenol formaldehyde sulphonate (PhFS) and melamine formaldehyde sulphonate (MFS). This work is aimed to evaluate the effect of PhFS and MFS on the hydration reaction of cement pastes during the first 24 h by determining the initial, final setting times and the electrical conductivity changes, as well as the effect of these polymers on the hydration progressing up to 90 days by determining the chemically combined water content and gel/space ratio of each paste at different intervals of time (1, 3, 7, 28 and 90 days).
Scientific Research and Essays, 2014
The effect of individual and combined addition of both nanosilica (NS) and polycarboxylate ether plasticizer (PCE) admixtures on cements pastes was studied. The sole incorporation of NS increased the water demand, as proved by the mini-spread flow test. An interaction between NS and hydrated cement particles was observed in fresh mixtures by means of particle size distribution studies, zeta potential measurements and optical microscopy, giving rise to agglomerates. On the other hand, the addition of PCE to a cement paste increased the flowability and accelerated the setting process. PCE was shown to act in cement media as a deflocculating agent, reducing the particle size of the agglomerates through a steric hindrance mechanism. Mechanical strengths were improved in the presence of either NS or PCE, the optimum being attained in the combined presence of both admixtures that involved relevant microstructural modifications, as proved by pore size distributions and SEM observations. The results indicate also the effectiveness of NS and polycarboxylate superplasticizer in producing high packing density and in accelerating the pozzolanic activity to produce more C-S-H gel by consuming calcium hydroxide Ca(OH)2 in order to improve the mechanical properties of cement pastes.