Properties Of Cement-based Materials Research Articles

Effect of ground steel slag powder on cement properties

The work aims to evaluate the influences of steel slag's fineness and particle-size distribution on the properties of cement-based materials. The materials used for this study included Portland cement and steel slag powder with seven different specific surface areas. The properties of cement pastes and mortars with steel slag powder were tested including water requirement of normal consistency, setting time, fluidity, soundness, compressive and flexural strength. The experimental results show that the influence of steel slag powder on water requirement of normal consistency of cement is in relation to its specific surface area, and the value of decreases for steel slag powder with a lower-specific surface area while increases with a higher-specific surface area. The partial replacement of cement by steel slag powder decreases the strength of cement, but increases the ratio of flexural to compressive strength and thus improves the ductility of cement-based materials.

Effect of superfine blast furnace slag powder on properties of cement-based materials

Industrial waste-like slag has caused serious problems all over the world. In this paper, blast furnace slag was ground to be superfine powder and partial replacement of cement. Multiple contents of slag powder used in cement were studied by cement paste, cement mortar and cement concrete experiment. Water requirement of normal consistency, setting time, soundness, fluidity, compressive and flexural strength were chosen to evaluate the performance of cement-based with different contents of slag powder. The results show that superfine blast furnace slag powder can be effectively used in cement with high contents. The strength of cement mortar with 70% superfine blast furnace slag powder still can meet the requirements of Portland cement P•O 32·5. Meanwhile, superfine blast furnace slag powder can improve fluidity of cement-based materials.

Influences of nano-TiO2 on the properties of cement-based materials: Hydration and drying shrinkage

To better understand the influences of nano-TiO2 on the properties of cement-based materials, the hydration process, the compressive strength development, and the drying shrinkage of cement-based materials with the addition of nano-TiO2 of 25nm were investigated. Results showed that nano-TiO2 increased the compressive strength of cement mortar through its acceleration on cement hydration and the pore-refining effect: 5wt.% nano-TiO2 accelerated cement hydration process for 2h and reduced the most probable pore size by 19.4%, 48.5%, and 54.4%, respectively. In addition, the influences of the hydrophilicity of nano-TiO2 on the water loss and volume stability of hardened cement pastes were primarily investigated and discussed in this work. For a comparison study, nano-SiO2 of 30nm size was also used. Results showed that the decline of the contact angle and the refining of pore structure with the addition of nano-TiO2 slowed down the water loss of hardened cement paste, which resulted in a comparable drying shrinkage to that of the control sample at 1month age.

Effect of mixing uniformity of sand–cement mixture on dielectric properties

The dielectric properties of cement-based material are closely related to the mixture proportion, and thus can be used for evaluation of its quality and integrity. For the same mixture proportions, however, the mixed states are always different. It is thus important to determine whether the mixing uniformity of a sand–cement mixture has an effect on the dielectric properties. In this study, the dielectric properties of a sand–cement mixture were measured using the neural network inversion method. The results indicate that the mixing uniformity of a sand–cement mixture has no obvious effect on its dielectric properties and the measured results were approximately in agreement with values calculated using the Maxwell–Garnett formula. Therefore, when measuring the dielectric properties of a sand–cement mixture, the volume ratio is important but mixing uniformity is not.

Effects of an AMPS-modified polyacrylic acid superplasticizer on the performance of cement-based materials

A self-made AMPS-modified polyacrylic acid superplasticizer and two others of the same type but with different molecular structures, which are commercially available, are used in this study to investigate the effect of a 2-acrylamide-2-methyl propylene sulfonic (AMPS)-modified polyacrylic acid superplasticizer on the properties of cement-based materials. In the experiments, initial fluidity, 1 and 2 h fluidity over time after admixtion, bleeding rate of the net cement mortar, and adsorption capacity and rate of cement particles are determined by adding different dosages of the three superplasticizers into the cement paste to characterize the dispersivity and the dispersion retention capability of each superplasticizer. Water-reducing rates of three kinds of mortars are simultaneously determined to characterize the water-reducing capacity of each superplasticizer, as well as the 3 and 28 d compressive strengths to characterize the compression resistance. Results show that water-reducing effect and fluidity better maintain the capability of the AMPS-modified polyacrylic acid superplasticizer than the two commercially available polyacrylic acid superplasticizers, and the compressive strengths after 3 and 28 d show significant growth. In conclusion, the effects of water reduction and strengthening of the AMPS-modified polyacrylic acid superplasticizer are evidently better than those of the two commercially available polyacrylic acid superplasticizers.

Microstructure, characterizations, functionality and compressive strength of cement-based materials using zinc oxide nanoparticles as an additive

Zinc oxide nanoparticles as a nanophotocatalyst has great potential for self-cleaning applications in concrete structures, its effects on the cement hydration, setting time and compressive strength are also important when using it in practice. This paper reports the effects of zinc oxide nanoparticles, as an additive material, on properties of cement-based materials. Setting time, compressive strength and porosity of mortars were investigated. Microstructure and morphology of pastes were characterized using scanning electron microscope and X-ray diffraction (XRD), respectively. Moreover, thermal gravimetric analysis (TGA) and Fourier-transform infrared spectrometer (FTIR) were also used to determine the hydration reaction. The results show that Portland cement paste with additional ZnO was found to slightly increase the water requirement while the setting time presented prolongation period than the control mix. However, compressive strength of ZnO mixes was found to be higher than that of PC mix up to 15% (at 28days) via filler effect. Microstructure, XRD and TGA results of ZnO pastes show less hydration products before 28days but similar at 28days. In addition, FTIR results confirmed the retardation when ZnO was partially added in Portland cement pastes.

Effects of the pozzolanic reactivity of nanoSiO2 on cement-based materials

The aim of this work is to understand the characteristics of the pozzolanic reactivity of nanoSiO2 from studies of its pozzolanic reaction kinetics, morphology and structure of the hydrates and the influences of these features on the properties of cement-based materials, so as to explore a more targeted way of using nanoSiO2 in cement or concrete. It revealed that the pozzolanic reaction of nanoSiO2 is of the first-order and the apparent reaction rate constant of nanoSiO2-4nm is about one order of magnitude bigger than that of silica fume, but the specific reaction rate constant is about one half to that of silica fume. A compacter gel structure and poorer crystallinity of the hydrates of nanoSiO2 to those of silica fume are found, as well. The rate of hydration of cement at very early ages is enhanced by nanoSiO2, but the rate slows down with aging due to the compact gel structure. To make the use of the high pozzolanic reactivity and ultrafine particle size of nanoSiO2, as well as its resulting compact gel structure, colloidal nanoSiO2 was applied onto the hardened cement mortar by brushing technique and a less permeable surface was resulted, which shows the potential of using nanoSiO2 as a surface treatment material for cement-based materials.

Effect of Different Forms of CaO on the Properties of Cement-Based Materials Containing High Content of GGBFS

The effects of different forms of CaO on performances of cementitious binders containing 50 wt. % GGBFS powder are studied using compressive strength testing, hydration heat and X-ray diffraction measuring, microstructure measuring, and deformation testing. Results show that, the use of analytical-grade CaO or calcined CaO expansive clinker produces a higher mechanical strength than analytical-grade Ca (OH)2for mortar samples. The mortar containing analytical-grade CaO or calcined CaO expansive clinker shows a strength increase higher than the reference before 14 days of curing, but a litter lower than the reference after 28 days. With the increase of curing age, the diffraction peaks of Ca (OH)2gradually weaken, while those of C-S-H and hydrotalcite gradually increase, contributing to a gradual increase in strength of GGBFS pastes. Compared to analytical-grade CaO, the expansive process of calcined CaO expansive clinker matches better to the deformation history of mortar containing large content of GGBFS. This work is of great significance to explore the potential use of different forms of CaO as an alternative activator for GGBFS.

On the Fresh/Hardened Properties of Cement Composites Incorporating Rubber Particles from Recycled Tires

This study investigates the ameliorative effects on some properties of cement-based materials which can be obtained by incorporating rubber particles as part of the fine aggregates. The aim is to find out optimal cement composite/mortar mixtures, containing recycled-tyre rubber particles, suitable for specific engineering applications. Different percentages of rubber particles, from 0% to 75%, were used and, for each percentage, the suitable amount of sand was investigated in order to achieve the best fresh/hardened performances. In particular the following characteristics were examined: density, compressive strength, modulus of elasticity, shrinkage, weight loss, flexural behaviour, thermal conductivity, rapid freezing and thawing durability, and chloride permeability. The experimental results were compared with the ones of cement composite specimens without rubber aggregates. Test results show that the proposed rubberized mortar mixes are particularly suitable for some industrial and architectural applications, such as under-rail bearings, road constructions, paving slabs, false facades, and stone backing.

Influence of Silica Fume on the Reflectivity and Transmission Efficiency of Cement-Based Materials

As a kind of mineral admixture, silica fume has low permittivity, which will affect the electromagnetic properties of cement-based materials. To study the effect of silica fume on the properties of cement-based materials, the reflectivity, transmission efficiency and pore structure were analyzed by using the vector network analyzer and mercury injection apparatus. Results show that silica fume can make the mortar more compact and the porosity of sample with 9% silica fume is only 17.8%, which is far lower than the control sample; With the increase of the silica fume content, the peak of reflectivity curve increases from -23.2 dB to -16.0 dB, and then decreases from -16.04 dB to -28.7 dB in the frequency range of 6 – 18 GHz. Reflectivity of sample with 3% content of silica fume is lower than other samples within 26.5 - 40 GHz; Transmission efficiency of samples shows the trend of increase with silica fume content increases from 0% to 6% within 8.2 - 12.4 GHz, 12 - 18 GHz and 26.5 - 40 GHz, but when the content increases from 6% to 9%, the transmission efficiency of samples reduces.

Effects of surface-activated coal gangue aggregates on properties of cement-based materials

Effects of calcined coal gangue (CG) aggregates treated by the surface thermal activation on the flowability and strength, and paste-CG aggregate interfaces of the cement-based material were investigated. The experimental results show that the compressive and flexural strength of the cement-based material with the calcined CG aggregates is much higher than that of the material with the natural CG aggregates, but the flowability of the material with calcined CG is significantly reduced with the calcined time. The strength of the material with the calcined CG aggregates only increases little with the calcined time at the same w/c ratio, but is reduced with the calcined time at the same flowability. The CG aggregates calcined by the surface thermal activation obviously overcomes the disadvantages of fully calcined CG.

Research on Absorbing Property of Three Kinds of Cement-Based Material Blending Compositions

The absorbing performance have been tested and analyzed by taking cement as matrix, blending material silica fume and culver zed fuel ash, graphite and carbon fibers, nanoTiO2 and steel fibers for absorbing agent trial Sample, in the 8 ~ 18 GHz frequency band, the results indicate that silica fume and culver zed fly ash, nanoTiO2 and steel fiber and composite cement which made of Absorbing material has good absorbing property. Graphite and carbon fiber and cement composite made of the effectiveness of absorbing materials. Blending material absorbing properties of cement-based materials, the impact must be considered together, not the more the better, when blending material exceeding a certain threshold, its ability of wave-transparent enhance while absorbing property will be reduced finally.

Experimental and Numerical Simulation of Absorbing Property of Cement-Based Material Blending with Silica Fume and Culver Zed Fuel Ash

The absorbing performance have been tested and analyzed by taking cement as matrix, blending material silica fume and culver zed fuel ash for absorbing agent trial Sample, in the 8 ~ 18 GHz frequency band, the results indicate that silica fume and culver zed fly ash and composite cement which made of Absorbing material has good absorbing property. Blending material absorbing properties of cement-based materials, the impact must be considered together, not the more the better, when blending material exceeding a certain threshold, its ability of wave-transparent enhance while absorbing property will be reduced Finally. By using ANSYS software for computer simulation of the specimen to test experimental data and found the computer simulation algorithm not only can verify the correctness of the conclusion but also auxiliary correction deviation appeared in the course of the real data and the error value.

Experimental and Numerical Simulation of Absorbing Property of Cement-Based Material Blending with Graphite and Carbon Fibers

The absorbing performance have been tested and analyzed by taking cement as matrix, blending material graphite and carbon fibers for absorbing agent trial Sample, in the 8 ~ 18 GHz frequency band, the results indicate that graphite and carbon fibers and composite cement which made of absorbing material has good absorbing property. Blending material absorbing properties of cement-based materials, the impact must be considered together, not the more the better, when blending material exceeding a certain threshold, enhance its ability of wave-transparent enhance while absorbing property will be reduced finally. By using ANSYS software for computer simulation of the specimen to test experimental data and found the computer simulation algorithm not only can verify the correctness of the conclusion but also auxiliary correction deviation appeared in the course of the real data and the error value.

Experimental and Numerical Simulation of Absorbing Property of Cement-Based Material Blending with Nano-TiO<sub>2</sub> and Steel Fibers

The absorbing performance have been tested and analyzed by taking cement as matrix, blending material nanoTiO2 and steel fibers for absorbing agent trial Sample, in the 8 ~ 18 GHz frequency band, the results indicate that nanoTiO2 and steel fibers and composite cement which made of absorbing material has good absorbing property. Blending material absorbing properties of cement-based materials, the impact must be considered together, not the more the better, when blending material exceeding 6wt%, its ability of wave-transparent enhance while absorbing property will be reduced finally. By using ANSYS software for computer simulation of the specimen to test experimental data and found the computer simulation algorithm not only can verify the correctness of the conclusion but also auxiliary correction deviation appeared in the course of the real data and the error value.

Prediction of Elastic Modulus of Cement-Based Materials Based on Power’s Volume Model

The hydrated products, unhydrated cement and water (capillary pores) in the cement paste are seen as matrix, inclusion, Equivalent medium respectively, We used the micromechanics theories and Power’s Volume model to develop a multi-phase micromechanics model capable of simulating the elastic properties of cement-based materials, and the evolution of elastic properties in the hydration process was calculated at different water-cement ratio. The final experimental results show that this model can be used to predict the elastic properties of cement-based materials.

Effects of colloidal nanosilica on rheological and mechanical properties of fly ash–cement mortar

The present study is aimed at investigating the combined effects of colloidal nanosilica (CNS) and fly ash on the properties of cement-based materials. The fresh and hardened properties of mixtures with CNS of 10 nm size and two Class F fly ashes were evaluated. Results revealed that CNS accelerates the setting of fly ash–cement systems by accelerating cement hydration, while fly ash can offset the reduction in fluidity caused by CNS. The early-age strength gain (before 7 d) of fly ash–cement systems was improved by CNS. However, the strength gain of mixtures with CNS diminished at later ages (after 28 d), where strength was eventually comparable to or exceeded by mixtures without CNS. Results showed that lack of Ca(OH)2, which results from the high pozzolanic reactivity of CNS at early ages, and the hydration hindrance effect of CNS on cement at later ages can be the critical reasons.

Research Advances on Multi-Scale Modeling of Properties of Cement-Based Materials

Cement-based material is a complex multi-scale material which is difficult to comprehend. With the simulation model, the methods and examples of multi-scale modeling of structure and performance of cement-based materials are presented based on coupled cementitious composites and structural mechanics. This paper discuss on the properties of cement-based materials as shrinkage, elasticity, durability which are carried out by numerical methods such as Finite Element Method (FEM) and eXtended FEM(XFEM).

Investigations of Calcined Bagasse Ash on Mechanical Properties of Cement-Based Materials

Investigations of Calcined Bagasse Ash on Mechanical Properties of Cement-Based Materials

Attenuation Ratios of Cement-Based Materials Containing B<sub>4</sub>C to 14.8MeV Neutron

Cement-based material samples having 0%, 5%, 10% and 20% B4C concentrations have been prepared for this reserach. Neutron attenuation measurement has been done by using 14.8MeV neutrons from the 5SDH-2 accelerator, and some mechanics properties of the same proportion also have been tested. It has been shown that when the B4C precentage and thickness of the samples increase, neutron attenuation values of the samples increase. Both the flexural and compressive strength firstly increased with B4C addition up to 10% approximately, and then decreased sharply with an addition up to 20%. It is thus possible to enhance the neutron shielding property of cement-based materials by adding B4C.