Abstract: The present paper deals with the principles of process technology for concrete-polymer composites, the research and development history of the concrete-polymer composites, the recent trends in the research and development of the concrete-polymer composites and the present status of major standardization work for the concrete-polymer composites, on the basis of comprehensive literature survey. The future trends in the research and development of the concrete-polymer composites are predicted, and sustainable concrete-polymer composites are proposed for the 21st century.
Abstract: Construction chemistry is underdeveloped compared to other chemical branches. Innovation is realized by new products, improved pro¬cesses or / and more efficient organization. Innovation becomes evident when a noticeable progress is achieved by implementing changes. There are seven fundamental hindrances or flaws possible which are briefly considered. The state-of-the-art must be known. Innovation is measured in comparison to this state-of-the-art. If this level is not yet attained, progress is easily realized by introducing the actual knowledge. The realization is measured according to qualitative or preferably quantitative bench¬marks. Unfortunately, this is not currently done in the field of construction chemistry. Before benchmarking starts, communication based on truth and trust must be effective. The available scientific me¬tho¬dology must be known. Benchmarking will possibly show deficiencies in education and training. This will stress the need for adequate trans¬parency to improve efficiency. Hope¬ful¬ly, a self-regulating process improving pro-ducts and processes will be created in this way.
Abstract: The presence of water-soluble polymers affects the microstructure of polymermodified cement mortar. Such effects are studied by means of SEM investigation. Polyvinyl alcohol-acetate (PVAA), Methylcellulose (MC) and Hydroxyethylcellulose (HEC) are applied in a 1 % polymer-cement ratio. The polymers provide an improved dispersion of the cement particles in the mixing water. The tendency of certain water-soluble polymers to retard the flocculation of the cement particles minimizes the formation of a water-rich layer around the aggregate surfaces. They also provide a more uniform distribution of unhydrated cement particles in the matrix, without significant depletion near aggregate surfaces. Both effects enable to reduce the interfacial transition zone (ITZ). The polymers also provide a more cohesive microstructure, with a reduced amount of microcracks.
Abstract: The main difference between normal mortar and polymer modified mortar is the microstructure. Whereas cement is the only binder in normal concrete, the binder of PCM contains cement and polymer. It is known, that these polymer modified cementious matrixes show a higher shrinkage than the non-modified ones. But it is also known, that the PCMs show fewer cracks due to shrinkage. A lot of different investigations have been carried out to find the reason for this con-tradiction. The measurement of shrinkage of PCMs and polymer modified cement stones will be presented in this paper. The prisms were stored under various climate conditions and show a varying shrinkage accordingly. Taking these results into account it becomes obvious that the shrinkage of PCMs depends considerably on the hydration shrinkage, to a lesser extent on the drying shrinkage. Furthermore, a model experiment as to the adhesive bond of cement stones compared to natural stones was introduced.
Abstract: this paper presents the results of a study in which the combination of two polymeric additives in concrete with the intention of improving its mechanical and durability performance is analysed. The additives are a synthetic latex and a biopolymer – chitosan. An evaluation of the mechanical properties as well as the phases formed based on scanning electron microscopy (SEM) and X-ray diffraction (XRD) was performed. The concretes were prepared with each of the polymers separately, and the results were ordinary. However, when combined, the results show an interesting interaction improving the mechanical strengths of the concrete. Several concrete samples were prepared with 0 – 4 % of each polymer with 1 % increments. The mechanical properties were shown to be sensitive to the incorporation of polymers. The desired effect of the interaction between the biopolymer and the latex was observed, because the strengths increased when both additives were present, namely for the combination of 2 % of each polymer. SEM images revealed a heterogeneous distribution in the polymer cementitious matrix, mainly with regards to latex. The presence of well defined polymer fibers on a fracture surface of composites prepared with biopolymer (4 %) was observed, indicating that the fibre pullout and not fracture was the cause of failure, resulting from the poor adherence of the fibers in matrix. Composites prepared with both polymers revealed abundant formation of C-S-H and the absence of ettringite, explaining the improvement of mechanical properties. The presence of reticulated structures of C-S-H dispersed in the microstructure and involving the calcium hydroxide corroborates the results of mechanical properties, mainly for the percentages of 3 % of biopolymer and 1 % of latex.
Abstract: Polyvinylalcohol (PVA) is a polymer soluble in hot water, it has the property of film formation and it can improve the concrete performance. The effects of PVA modified with nano clay on the cement hydration reaction have been investigated by means of semiadiabatic calorimeter, FTIR spectroscopy and SEM. FTIR spectroscopy was employed to monitor chemical transformation of cement. The morphology of the different samples was compared by means of SEM micrographs. With the semiadiabatic calorimeter the hydration kinetic was measured to compare the heat rate of the admixtures materials. Fixing the water–cement ratio, w/c, in 0,45, the ratio of polymer to cement (p/c) was 2 wt% and the ratio of clay to polymer was 4 wt% (0.8wt.% related to cement). The polymer and modified polymer admixtures produced a retardation effect on the kinetic of cement hydration, but the clay acts as nucleating agent. The increase of the temperature with time was measured and a new model with four parameters was employed and the kinetic parameters were determined for each sample.
Abstract: Hydration of cement in the presence of SBR dispersion and powder respectively was investigated using the methods of ITC, XRD and ESEM. The results show that both the dispersion and powder of SBR facilitate the formation, enhance the stability of AFt and inhibit the formation of C4AH13 in cement paste; the effect of the powder is more evident than the dispersion. Both the dispersion and powder of SBR delay the formation of C-S-H and Ca(OH)2 in cement paste, and the effect of the dispersion is more evident. Up to 3 days, the structure of the SBR dispersion – or powder – modified cement pastes has no significant difference with that of control paste except due to a thin polymer film on the surface. The two polymers delay the early cement hydration, but have no significant effect after 3 days.
Abstract: Macro-defect-free (MDF) cements are cement-polymer composites and were developed by Birchall et al. three decades ago. The composites are produced by mixing small amounts of polymer and water with cement. However, they have a different production method than that of cement pastes, which was inspired by rubber production. Mixtures of cement, polymer and water are processed by using a two-roll mill. The composites are known with their high flexural strengths. Unfortunately, there are not any known commercial products using MDF cements because of their poor durability under moisture. In this study, MDF cements were prepared by using poly(vinyl alcohol--vinyl acetate) PVA, calcium aluminate cements and two different types of epoxy resins. Epoxy resins were a diglycidyl ether of bisphenol A and a mixture of a diglycidyl ethers of bisphenol A and F. Durability performance was compared with respect to biaxial flexural strengths, contact angle and atomic force microscopy (AFM) for the specimens stored in water.
Abstract: This study focuses on the development of a lightweight, high-performance cementitious composite material reinforced with Poly(vinyl alcohol) (PVA) fiber. The material which contains Poly(vinyl butyral) (PVB) as the sole aggregate has a low average density of 1548 kg/m3 and a compressive strength of about 40 MPa. The flexural strength, impact resistance, and fracture toughness are also evaluated and are found to be improved in comparison to those of lightweight concrete. The addition of PVA fiber further improves ductility, fracture toughness and impact resistance. The increase in fracture toughness was found to be linear with increasing fiber volume fraction. Comparisons are made with a lightweight concrete of equal density, and a normal-weight concrete. A model based on fiber bridging mechanics and the rule of mixtures is developed to characterize the fracture toughness, and a good correlation is obtained for the materials tested when experimental results are compared to those predicted by the model.