Effects of metallic monomer powders on the mechanical properties of hardened polyester and acrylic polymer concrete

To investigate the effects of three metallic monomer powders on polyester‐ and acrylic‐hardened polymer concretes, polymer concretes incorporating different levels of these materials were investigated for the properties of hardened polymer concrete. The mix design was made and optimized for workability and strength, depending on the resin viscosity, the intended use, and the additional quantities of these polymeric materials. The investigated properties included the compressive strength, flexural strength, and bond strength of hardened polymer concrete. It was concluded that these polymeric materials offer the possibility of improving the properties of polyester‐ and acrylic‐hardened polymer concretes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3106–3113, 2006     

Influences of metallic polymeric materials on the properties of fresh polyester and acrylic polymer concrete

To investigate the influences of three metallic polymeric materials in polyester and acrylic fresh polymer concretes (PCs), PC‐incorporated different levels of these materials have been investigated for their properties of fresh PC. The mix design was made and optimized for workability, strength, and economy, depending on the resin viscosity, the intended use, and the additional quantities of these polymeric materials. The properties investigated include workability, working time, and curing time of fresh PC. It is concluded that these polymeric materials offer the possibility of improving properties of polyester and acrylic fresh polymer concretes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Study of the behavior of polyester concretes containing ionomers as curing agents

Polyester concretes have been used in constructions for more than 20 years. This type of polymer concrete can advantageously replace traditional Portland concrete in situations that require fast consolidation of the material. Otherwise, polyester concretes are usually more expensive than Portland concretes. Part of the high cost of the polyester concretes is due to the fact that the aggregates used in the formulation of the concretes need to be dried prior to their incorporation into the polymer matrix. In this work, the use of different curing systems (methacrylic acid and maleic anhydride) was investigated to test the hypothesis that the introduction of acid functionalities into unsaturated polyesters based on isophthalic acid could both restrict the detrimental effect of moisture in the curing process and also improve interfacial interactions even in polyester concretes containing wet aggregates. In this work, as there was no search for ways to reduce cost of polyester concretes and also to contribute to the environmental preservation, unsaturated polyesters were synthesized from PET bottles and tested in the fabrication of concretes by reacting them with a conventional curing agent (styrene). Gel permeation chromatography, infrared spectroscopy, and electron microscopy were used to monitor and analyze the production of unsaturated polyester resins and concretes. Mechanical properties were also evaluated by compression tests. Results showed that methacrylic acid and maleic anhydride, when used as curing agents, led to the production of polyester concretes having higher mechanical properties in both dry and wet states than conventional polyester (based on isophthalic acid) concretes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Interfacial adhesion in polyester resin concrete

Silane coupling agents are widely used to improve the interfacial adhesion between the inorganic filler and the organic polymer matrix of polymer concretes. The mechanical properties of the concretes are also found to improve on the addition of silane coupling agents. This paper compares two methods of silane application; pretreatment of aggregates with silane and direct addition of silane to the resin, on the interfacial adhesion in polyester resin concrete for three different silanes. The effects of other parameters, such as the silane loading, predrying of aggregates before silane treatment, addition of CaCO₃ microfiller and pH of the silane treatment medium, are also investigated.     

Studies on Furan Polymer Concrete

Good mechanical properties and excellent chemical resistance of polymer concretes make them cost effective material of construction for civil engineering applications. These properties of polymer concretes are dependant upon the type of polymeric binder and the filler materials used. In the present investigation, a series of polymer concretes based on furan resin have been prepared using an aggregate mix proportion having minimum void content. Density, water absorption and microstructure were studied for different combinations designed on the basis of mixture design concept of design of experiments. The effects of variables on the properties were discussed.     

Effect of metakaolin dispersion on the fresh and hardened state properties of concrete

The use of pozzolanic materials such as metakaolin in mortars and concretes is growing. Their use is usually related to the promotion of hydraulic binder reactions or to the mitigation of expansive reactions that can occur in concrete. Introduction of fine particles such as metakaolins, can have a strong effect on fresh and hardened state properties. This paper aims to study the effect of metakaolin in concrete formulations with a preset workability and to assess the system rheology but also its hardened state properties such as mechanical strength. The effect that the dispersion of metakaolin particles induces on concrete microstructure, particularly in porosity, is discussed. Formulations were prepared with several metakaolin amounts and workability was controlled either with water or a high range water reducer admixture (HRWRA). The use of HRWRA can cause deflocculation of metakaolin particles, allowing workability control in concrete and leading to better efficiency and improved performance.     

Properties of lightweight expanded polystyrene aggregate concretes containing fly ash

Lightweight concretes can be produced by replacing the normal aggregates in concrete or mortar either partially or fully, depending upon the requirements of density and strength levels. The present study covers the use of expanded polystyrene (EPS) beads as lightweight aggregate, both in concrete and mortar. The main aim of this programme is to study the mechanical properties of EPS concretes containing fly ash and compare the results with these in literature on concretes containing OPC alone as the binder. The effects of EPS aggregate on the green and hardened state characteristics of concretes containing fly ash were evaluated. The compressive strength of the EPS concretes containing fly ash show a continuous gain even up to 90 days, unlike that reported for OPC in literature. It was also found that the failure of these concretes both in compression and split tension was gradual as was observed earlier for the concretes containing plastic shredded aggregates. The stress-strain relations and the corresponding elastic modulus were also investigated.     

Eco-friendly concretes with reduced water and cement contents — Mix design principles and laboratory tests

The major environmental impact of concrete is caused by CO₂-emissions during cement production. Great potential for reducing the impact is seen especially for concretes with normal strength. The use of superplasticizers and highly reactive cements as well as optimization of particle-size distribution and reduction in water content allows a significant reduction in Portland cement clinker in the concrete. Essential is the addition of mineral fillers (e.g. limestone powder) to provide an optimal paste volume. In addition, the already practicable substitution of secondary raw materials like fly-ash or furnace-slag for cement clinker is an appropriate option which is however limited by the availability of these resources.In several test series the fresh and hardened concrete properties of concretes with reduced water and cement contents were investigated, especially their workability, strength development, design-relevant mechanical properties as well as durability aspects such as carbonation. It was shown that concretes with cement clinker and slag contents as low as 150 kg/m³ were able to meet the usual requirements of workability, compressive strength (approx. 40 N/mm²) and mechanical properties. The carbonation depth of concretes with 150-175 kg/m³ clinker and slag was equal or lower than the depth of conventional reference concretes for exterior structures. The ecological advantages were identified, using environmental performance evaluation. A reduction of up to 35% in environmental impact was calculated compared with conventional concrete and of more than 60% with granulated blast-furnace slag. Practical application was verified by means of full-scale tests in a precast and ready-mix concrete plant.     

Influence of polymer type on adhesion performance of a blended cement mortar

The purpose of this study was to examine the influence of various polymeric materials on the adhesion characteristics of a rapid setting, minimum defect mortar based upon a blend of calcium sulfoaluminate (CSA) cement and ordinary Portland cement (OPC). Four different polymer powders were added to the base mortar at a polymer/cement ratio (p/c) of 0.15. The water/cement (w/c) ratio remained constant for all mortars at 0.42. The polymeric materials consisted of an acrylic polymer powder with T_g=−10 °C, a styrene butadiene rubber (SBR) polymer powder with T_g=15 °C and two vinyl acetate/ethylene (VAE) polymer powders, one with T_g=−7 °C and the other with T_g=20 °C. Mortars were tested for direct tensile strength following ASTM C307 and pull-off strength following a variant of ASTM C1583 after curing for either 24 h or 13 days at ambient laboratory temperature of 23 °C. Mortars were cast over concrete, wood, metal and glass substrates. Pull-off tests over concrete substrate resulted in substrate failure for all polymer modified mortars. Pull-off tests cast over wood, glass and metal substrate materials highlighted the SBR polymer for demonstrating the poorest adhesion performance. Statistical analysis was performed with Minitab software.     

Influence of hydration on the mechanical,structural, thermal,and morphological properties of cement filled epoxy composites

Different loading of Portland cement (PC) (10, 20, 30, and 40 wt%) was used to produce epoxy-based polymer concrete. The optimum loading was used to prepare another sample using hydration in presence of air circulation. The polymer concretes were characterized in terms of mechanical, thermal, structural and morphological properties. The properties showed increasing trends after cement addition. Results showed that the tensile strength of the polymer concretes were improved by 37.2%, 115.5%, 165.9%, and 40.6% for loading of 10, 20, 30, and 40 wt% cement, respectively. In addition, the flexural strength of the polymer concretes was also enhanced and found maximum (175.3% higher) in 30 wt% concrete compared to neat epoxy. Other mechanical properties of the polymer concrete were also found increasing. Moreover, decomposition temperature was raised nearly 15°C for adding 30 wt% cement which was the maximum among the other polymer concretes. For the case of hydration in presence of air circulation, the prepared composite showed the highest tensile mechanical performance with improved surface topography. From the results, it was concluded that the addition of cement into the epoxy was very effective to produce polymer concretes.     

Properties of concretes produced with waste concrete aggregate

An environmentally friendly approach to the disposal of waste materials, a difficult issue to cope with in today's world, would only be possible through a useful recycling process. For this reason, we suggest that clearing the debris from destroyed buildings in such a way as to obtain waste concrete aggregates (WCA) to be reused in concrete production could well be a partial solution to environmental pollution. For this study, the physical and mechanical properties along with their freeze-thaw durability of concrete produced with WCAs were investigated and test results presented. While experimenting with fresh and hardened concrete, mixtures containing recycled concrete aggregates in amounts of 30%, 50%, 70%, and 100% were prepared. Afterward, these mixtures underwent freeze-thaw cycles. As a result, we found out that C16-quality concrete could be produced using less then 30% C14-quality WCA. Moreover, it was observed that the unit weight, workability, and durability of the concretes produced through WCA decreased in inverse proportion to their endurance for freeze-thaw cycle.     

Thermal and Phase Change Material Properties of Comb-Like Polyacrylic Acid-Grafted-Fatty Alcohols

Poly(acrylic acid)-graft-fatty alcohol are synthesized from the esterification of polyacrylic acid with octadecanol and docosanol. The characterization of poly(acrylic acid)-graft-fatty alcohol was performed by attenuated total reflection–Fourier transform infrared spectroscopy. The thermal stability performances and phase change behaviors of poly(acrylic acid)-graft-fatty alcohol were examined by using thermogravimetric analysis system and differential scanning calorimetry. The results indicate that the poly(acrylic acid)-graft-fatty alcohol polymeric phase change materials possess good phase change properties and provide a suitable working temperature range. The heating process phase change enthalpy is measured between 112 and 122?J g^?1, and the freezing process phase change enthalpy is found between 118 and 126?J g^?1. The decomposition of poly(acrylic acid)-graft-fatty alcohol polymeric phase change materials started at 177°C and reached a maximum of 380°C. All of the obtained poly(acrylic acid)-graft-fatty alcohol polymeric phase change materials improved latent heat storage capacity in comparison with the pristine poly(acrylic acid) polymer. With the obtained results we conclude that, these materials promise a great potential in thermal energy storage applications.     

A model law for the notch sensitivity of brittle materials

In this paper a model law for the notch sensitivity of brittle materials, for instance hardened cement paste, mortar or concrete is presented. This model law shows that notch sensitivity is a necessary however not a sufficient condition for the applicability of linear elastic fracture mechanics. The model law indicates that notch sensitivity of a brittle material decreases with increasing fracture toughness, decreasing tensile strength and decreasing specimen size. The model law explains the increase of the net failure stress of notched specimens with increasing notch depth after passing through a minimum. Such behavior frequently has been observed in experiments on hardened cement paste, mortar and concrete specimens. Results of flexure tests on notched and unnotched hardened cement paste specimens and concretes of various sizes are in accord with the model law.     

新型弹性丙烯酸聚氨酯玻璃钢底漆的研制

以弹性丙烯酸树脂和HDI聚合物为成膜物制得双组分玻璃钢专用底漆,经测试其各项性能达到设计要求.研究发现:不同官能度的HDI聚合物固化剂对涂料的力学性能和施工性能有影响,但对耐化学品和耐久性影响不大;带亲颜料基团的高分子嵌段共聚物分散剂对漆料的研磨效率和贮存稳定性贡献要大于氨基聚酯型分散剂;有机改性膨润土和气相二氧化硅比聚乙烯蜡浆对涂料喷涂施工厚度提高效果要明显.     

Characteristics of a thermally activated alumino-silicate pozzolanic material and its use in concrete

This paper presents the results of the physical and chemical properties of a thermally activated alumino-silicate material (MK), and deals with the properties of fresh and hardened concrete incorporating this material. The properties of fresh concrete investigated included workability, bleeding, setting time, and autogenous temperature rise. The properties of the hardened concrete investigated included compressive, splitting-tensile and flexural strengths, Young's modulus of elasticity, drying shrinkage, resistance to chloride-ion penetration, freezing and thawing, and saltscaling resistance. The properties of the MK concrete were also compared with those of the control portland cement concrete and the silica fume concrete.

The test results indicate that the MK material is highly pozzolanic and can be used as a supplementary cementing material to produce high-performance concrete. Although it requires a higher dosage of the superplasticizer and air-entraining admixture compared with that of the control concrete, the MK concrete can be produced with satisfactory slump, air content, and setting time. The concrete incorporating 10% MK had higher strength at all ages up to 180 days compared with the control concrete; in comparison with the silica fume concrete the MK concrete showed a faster strength development at early ages, but had lower strength after 28 days. At 28 days, the MK concrete had somewhat higher splitting-tensile and flexural strengths, Young's modulus of elasticity, and lower drying shrinkage compared with that of the control and the silica fume concretes. The resistance of the MK concrete to the chloride-ion penetration was significantly higher than that of the control concrete, but similar to that of the silica fume concrete. The MK concrete showed excellent performance in the freezing and thawing test. The performance of the MK concrete subjected to the de-icing salt scaling test was similar to that of the silica fume concrete, but marginally inferior to the control concrete.     

Correlation between water permeability of latex-modified concrete (LMC) and water diffusion coefficient of latex film

Cement-based materials are generally known as weak materials in flexure and tension in comparison with compression. Polymers are used in cement-based materials to improve their flexural and tensile behaviors. The composite is called as polymer-modified concrete/mortar. Furthermore, polymers decrease permeability of water into cementitious matrices. Polymers are usually used as admixtures in concretes in form of latexes. Latexes are water-based polymers, which are consistent with water-based concrete matrices. On this basis, these kinds of products are called latex-modified concretes (LMCs). However, it has been found that chemical composition, particle size distribution, molecular weight, physical/mechanical properties of latexes affect performance of modified concretes. In this investigation, six latexes in three categories (acrylic, SBR and polyvinyl acetate) were used as concrete admixtures. They were characterized for chemical composition (by FTIR analysis), minimum film formation temperature, pH, glass transition temperature (T _g), particle size and particle size distribution to evaluate the effect of each property on LMC performance. Due to the formation of latex film in the microcracks and pores of concrete microstructure, it was suggested that diffusion of water into films controls permeability of whole concrete structures. On this basis, the diffusion coefficient of the latex films subjected to water was measured using a new method (continuous FTIR analysis). Capillary water absorption test was performed on concrete specimens to verify validity of the suggestion. It was found that there is a correlation between capillary water absorption of LMCs and water diffusion coefficient of latex films.     

碱–磷渣–粉煤灰混凝土力学性能和耐久性(英文)

研究了用碱激发磷渣_粉煤灰胶凝材料(atkali activated phosphor slag fly ash cement,AAPFC)制各的混凝土的力学性能和耐久性,并用扫描电子显微镜观察了形成的水泥石与骨料的界面结构.结果表明:相对于硅酸盐水泥混凝土,AAPFC混凝土具有强度高,弹性模量较低的特点;其抗冻性和抗氯离子渗透性显著优于硅酸盐水泥混凝土,但抗碳化性不及后者.硅酸盐水泥混凝土中水泥石与骨料界面上存在大量定向排列的Ca(OH)2,造成弱结合,而AAPFC混凝土中水泥石与骨料问结合紧密.     

Effects of diacrylate monomers on the bond strength of polymer concrete to wet substrates

The bond strengths of polymer concretes containing up to 15% (based on polymer resin) of diacrylate (DA) monomers were examined and compared with those without DA. A change occurring with the addition of DA monomers was an increase in the bond strength of polymer concrete to wet substrates. Zinc diacrylate (ZDA) and calcium diacrylate (CDA) were each used as an additive to monomers and resins [methyl methacrylate (MMA), polyester, and two kinds of epoxies]. The variables were amount of the DA monomers and surface conditions (wet or dry and smooth or rough). Bond strengths were measured by tension bond. ZDA was found to improve the bond strength of MMA and polyester, whereas CDA improved the bond strength of epoxies. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 991–1000, 2003     

萜烯基聚酯丙烯酸酯的合成及性能研究

以萜烯马来酸酐(TMA)、DCPD、顺酐(MA)、乙二醇(EG)、丙二醇(PG)、丙烯酸(AA)为主要原料,通过三步法合成了聚酯丙烯酸酯。通过红外光谱分析仪、动态机械分析仪和TG研究了不同原料配比、缩聚反应时间、阻聚剂用量对涂膜性能的影响。结果表明,该光固化涂膜具有良好的力学性能、耐化学性能和耐热性,且固化速度快,可单独作为UV固化的预聚物使用。     

Effects of marble powder as a partial replacement of cement on some engineering properties of self-compacting concrete

Self-compacting concretes (SCC) are highly fluid concretes that can flow and be placed in formwork under their own weight without the requirement of internal or external energy. This fluidity is obtained with the use of high paste volume and superplasticizer. The paste of SCC is made principally of cement, which is the most expensive component of concrete. As a result, the production cost of SCC is higher than conventional concrete. However, to make the manufacture of SCC more practical and economical, the binder is often a binary, ternary even quaternary compound: Portland cement mixed with mineral additions. The primary aim of this work is to study the effect of incorporating the marble powder as a supplementary cementations material on the rheological and mechanical properties of SCC. The fresh properties were measured using the slump flow, J-Ring, V-funnel, and modified slump flow. The properties of hardened SCC such as strengths and ultrasonic pulse velocity (UPV) were determined at age of 3, 28, and 90 days. The results have shown that using of marble powder in SCC enhances their fresh properties. At hardened state, the incorporation of marble powder decreases the mechanical strengths and UPV. It can be noted that it is possible to produce an economical SCC when the cement is partially substituted by the marble powder.