Pei Ming Wang

Dispersion and Absorption of SBR Latex in the System of Mono-Dispersed Cement Particles in Water

This paper investigates the dispersion of cement particles in water at different mix proportions using optical microscope, and the dispersion and absorption of SBR latex in the system of mono-dispersed cement particles in water using environmental scanning electron microscope (ESEM). The results show that the mono-dispersed cement can be well obtained at the water to cement ratio (mw/mc) of 10:1. The ESEM images present that SBR latex is dispersed on the surface of the cement particles as well as the solution phase. SBR latex does not prefer to be absorbed on the cement particles in spite of their opposite electric charge but chooses to be dispersed in the system proportionally. In addition, SBR particles are single-layer absorbed on the surface of cement particles in all the SBR latex to cement ratios (mp/mc). Several SBR particles absorbed on the surface of cement particle get close enough to form groups at the mp/mc of 15% and 20%. The results of this paper provide some bases for analyzing the influence of polymer on cement hydration and the microstructure formation of polymer-modified cement-based materials in a new view.

Effects of Redispersible EVA and E/VL/VC Powders on Properties of Decorative Mortar

Redispersible polymer powders of Vinyl acetate / ethylene copolymer (EVA) and Ethylene/vinyl laurate/vinyl chloride copolymer (E/VL/VC) were applied to modify decorative mortar. Results showed that EVA and E/VL/VC both smoothed the surface of mortar, decreased the leachability of Ca2+, K+, Na+ ions and increased the leachability of SO42- in the surface leaching solution. However, with redispersible EVA and E/VL/VC being the same content, E/VL/VC-modified mortar hydrated for 1d showed lower bulk density, better surface hydrophobicity, higher alkalis leachability and more severe efflorescence. Moreover, EVA and E/VL/VC both had little influence on the components of efflorescence substances on the surface of mortar.

Waterproof Performance of Polymer-Modified Cement Mortar

This paper tested the capillary water absorption, impermeability and cracking of cement mortars modified with three polymers respectively and founded the correlation of cracking with the waterproof performance. The results show that with the polymer content increasing, especially as the polymer/cement ratio (mp/mc) increases from 0% to 5%, the reduction in the capillary water absorption and the penetration depth of water into mortar is significant. When the mp/mc is more than 15%, the increase of the mp/mc in all mortars has little effect on the capillary water absorption and the penetration depth. For the purpose of reducing the cracking weighted value, the styrene-butadiene rubber (SBR) dispersion and the styrene-acrylic copolymer (SAE) powder are superior to the SAE dispersion. Regardless what kinds of polymers, the capillary water absorption and the penetration depth of water into mortar show exponential growth with the increasing cracking weighted value.

Influence of Temperature on the Hydration Heat of Polymer Modified Mortars

The hydration heat of polymer modified mortar were measured at 5°C、10°C、20°C and 40°C using Multi-channel Isothermal calorimeter. The effects of temperature on hydration heat of polymer modified mortars with 0.1% methyl hydroxylpropyl cellulose (MHPC), 3% ethylene vinyl acetate (EVA) and 0.1%MHPC+3%EVA were investigated. The curves of hydration heat show that the polymer reduces the hydration heat of mortars and it is related to the temperature. The effects will be more and more remarkable with the increasing of temperature; Temperature also affects the exothermic rate peak of polymer modified mortars. The exothermic rate peak of polymer modified mortar at low temperature is almost equal to that of the ordinary cement mortar. However, it is obviously lower than that of ordinary cement mortar at high temperature ; The time to the exothermic rate peak of polymer modified mortar is also related to the temperature.

Recent Research on Polymer-Modified Cement Mortar in China

Polymer has been widely used in construction in China during the past few years and has become a necessary component of some building materials. The development in concrete-polymer composites (CPC) is going with the economical achievement and practical needs, which focuses on polymer-modified cement mortar (PCM). Therefore, this paper introduces the trends and advances in research on PCM during the past few years in China, especially cement hydration in the presence of polymer, the properties and application of PCM, waste utilization as well as trends of concrete-polymer composites.

Influence of White Cement Content on the Performance of Decorative Mortar in the Presence of Microemulsion

The influence of white cement content on the compressive strength, flexural strength, tensile bond strength, water capillary absorption, anti-efflorescence and stain resistance of decorative mortar in the absence or presence of microemulsion were studied in this paper, meanwhile the effect of the microemulsion was analyzed. The results showed that the increasing white cement content increases the compressive and flexural strengths, reduces the water capillary absorption, and improves the stain resistance of the decorative mortar, but has adverse effect on the anti-efflorescence. While the tensile bond strength first increases and then decreases with the increase of the white cement content, and as the content of which is 7%, there appears a maximum value of tensile bond strength. The microemulsion improves the performance of the decorative mortar, particularly significantly enhancing the anti-efflorescence and stain resistance, except for the improvement of compressive and flexural strengths.

Damping Properties of EVA Modified Cement Pastes

Earthquakes, wind buffeting, ocean waves， noise vibration and explosion are all harmful to people’s life. For controlling the vibrations, one way is by improving the material damping capacity. Effects of improving the damping properties of cement based material by adding polymer, fiber and interfacial modification have been admitted. Whereas the relationship of the influence of the dosage of polymer to the damping functions and the changes of damping behaviors at different frequency, temperature environment have received much less attention. Furthermore, ethylene-vinyl acetate (EVA) which used as one of the mainly modified has been widely applied in various aspects such as improving ductility, impermeability and mechanical properties. However, the ability of EVA modification in cement on improving the damping capacity has received less attention. The main objective of this paper is to research the damping behavior of EVA modified cement pastes at different frequencies, temperatures and polymer contents by dynamic mechanical analyzer. Experimental results showed that damping property of EVA modification in cement was dramatically increased. For a certain EVA modified cement paste, tanδ slightly increases with the frequency increases and a sharp peak was found at the glass transition temperature. The SEM images indicated that there was a morphological difference in the plain cement paste and EVA modified cement paste.

Application of Styrene-Butadiene Rubber in Cement-Based Materials

This paper summarizes the function of styrene-butadiene rubber (SBR) in cement-based materials, focusing on the achievements of the authors in recent years. The effect of SBR on the properties of cement mortar is introduced, i.e. the workability of fresh mortar such as the water-reduction and water-retention effects of SBR, the mechanical properties of hardened mortar such as the tensile bond strength, flexural and compressive strengths, flexibility and anti-impacting capacity, the waterproofness such as the capillary water adsorption and anti-penetration capacity, the microstructure such as the matrix structure and interface structure, and the cement hydration such as the calcium silicate hydrates, calcium aluminate hydrates and polymerization of [SiO4]4- tetrahedron.

The Roles of B2O3 and P2O5 in the Formation of Cement Clinker

The roles of B2O3 and P2O5 in the formation of clinker which stand on the each side of the IV main group are discussed. The results show that the role of B2O3 and P2O5 in the formation of clinker are different: B2O3 has evident effect, which is lost at higher temperature, on the consumption of CaO at 1300°C while the effect of P2O5 is mainly reflected at higher temperature, especially at 1400°C; Suitable B2O3 makes C3S transform form R to M3, but P2O5 induces C3S change into M1. What they have in common is that more B2O3 and P2O5 will decrease the content of C3S.

Effects of Minerals on the Dissolvable Ion Concentration and pH Value of Hardened Cement

The influence of grinded blast furnace slag (GBFS), high-calcium fly ash (HF), desulfurized gypsum (DG) and Na2SO4 (NS) on dissolvable ion Moore concentration and pH value of hardened cement is researched. In liquor with hardened cement powder, the dissolvable ion Moore concentration of Mg, Si or Al is according to each ion content in raw materials of cement paste. In materials system of cement-slag-HF, NS reduces the ion Moore concentration of Al and increases that of Mg or Si. PH value of hardened cement is mostly controlled by dissolvable Ca ion Moore concentration in the material system of cement-BBFS-HF. Alkali metal ions, which is introduced with additional materials, effect pH value more remarkably than the dissolvable Ca ion Moore concentration. PH value of hardened cement decreases a little if 50% cement is replaced by same weight of GBFS and HF. HF can reduce pH value more seriously than GBFS. DG enhances S and Ca ion Moore concentration, and decreases pH value of hardened cement.