Ana H. Delgado

Comparison of IR Techniques for the Characterization of Construction Cement Minerals and Hydrated Products

The influence of FT-IR sampling techniques on the characterization of cement systems was investigated. Three FT-IR techniques were used to study tricalcium silicate (C3S), hydrated C3S, calcium hydroxide, and calcium silicate hydrate (C–S–H). They include transmission spectroscopy (TS), photoacoustic spectroscopy (PAS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The TS technique (using KBr pellets) was the most labor-intensive but was found to give the simplest spectra with well-defined bands. The PAS technique was found to be the simplest technique but yielded bands at lower wavenumber than TS. DRIFTS was determined to be a good alternative for cement powders since it provided spectra similar to those for the TS technique. DRIFTS required more sample preparation than PAS but less sample preparation than the KBr pellet technique.

Sealants and Adhesives

Many sealants used in the construction industry are required to maintain functional performance characteristics over many years. While in service, sealants are exposed to environmental factors such as UV radiation, water, oxygen, and thermal cycling. Depending on which face of the building sealants are placed, type of substrate, and geographic region, they may be exposed to extreme environmental conditions, stress, and strain gradients. Hence, sealants are susceptible to weather-induced degradation. In general, degradation involves both chemical and physical processes with the chemical reactions usually preceding the physical process. It also discusses that testing of adhesives is necessary in order to determine the level of performance and/or predicted durability. Some of the tests provide information on the working properties of the adhesive, such as viscosity, which affects mixing, application, and spreadability as well as wetting and penetration of the substrate. Other test methods measure the amount of resin present. This not only influences the viscosity of the adhesive, but also the performance of the bonded assembly.

An FT-Raman study of solid-state ion exchange in zeolites

Abstract This work describes the first application of FT-Raman spectroscopy to the investigation of solid-state ion exchange. The contact-induced ion exchange between the following zeolites was examined: Li-exchanged zeolite A (Li-A) and zeolite Y (Na-Y), Li-A and zeolite X (Na-X), Li-A and Ca-exchanged zeolite A (Ca-A). The solid-state ion exchange between zeolite Y (Na-Y, NH4-exchanged Y) and metal salts (LiCl and CaCl2) was also studied. The results were verified by powder X-ray diffraction. They are also in good agreement with those obtained from other techniques. The study demonstrates that FT-Raman spectroscopy is a useful tool for the study of ion exchange of zeolites in the solid-state.

Retarding and Water Reducing Admixtures

This chapter explains how several techniques have been used to obtain an understanding of the action of retarders/water reducers, such as the mechanism of their action, rate of hydration, setting times, microstructure, etc. The techniques that have yielded important results, include differential thermal analysis (DTA), thermogravimetry (TG), differential scanning calorimetry (DSC), scanning electron microscopy, chemical shrinkage measurements, isotherms, and loss on ignition. These techniques are generally applied on samples that are hydrated for certain periods of time. The conduction calorimetry, however, follows the instantaneous evolution of heat as a function of time. It provides a method of quickly assessing the relative rates of hydration in the presence of different amounts/types of admixtures. The time of termination of the induction period gives information on the relative retarding action of various types of retarders.

Investigation of the Effect of Heat on Specially Formulated Thermoplastic Polyolefin (TPO) Films by Thermogravimetry, Dynamic Mechanical Analysis, and Fourier Transform Infrared Spectroscopy

To explore the use of chemical methods of analysis in investigating the performance of thermoplastic polyolefins (TPO), the ASTM D08.18 Subcommittee undertook a study to evaluate TPO films of known composition. These specially formulated films with varying amounts of stabilizers were heat-aged for up to 56 days according to ASTM D 6878-03 and then analyzed using dynamic mechanical analysis (DMA), thermogravimetry (TG), and Fourier transform infrared (FTIR) spectroscopy. These techniques were found to be useful in characterizing the effect of heat on the TPO films under study and it is believed that they could be used to evaluate actual TPO membranes. Please note that these are films and not roof membranes. The formulations used for the films could be modified for use in actual membranes.

Introduction to Concrete Admixtures

This chapter explores that concrete admixtures are materials other than hydraulic cement, water, or aggregates that are added immediately before or during mixing. Additives or additions such as grinding aids are added to cement during manufacture. An addition is a material that is interground or blended during the manufacture of cement. Most concrete used in North America contains at least one admixture. The admixtures are added to improve the quality of concrete in the fresh and hardened state. Publications and patents on admixtures are voluminous. Interest in the development of admixtures is evident from the number of patents taken every year. Categorization of admixtures into distinct groups is not easy as one material may belong to more than one category. Broadly, however, they could be divided into some categories: chemical admixtures, air-entraining agents, mineral admixtures, and miscellaneous admixtures. The aim of the chapter is to introduce the role of different types of admixtures on cement and concrete properties.

Gypsum and Gypsum Products

This chapter discusses that the use of gypsum to control setting in Portland cement accounts for considerable quantities of the use of this material. Control of the reaction rate of tricalcium aluminate, the constituent of cement that reacts most rapidly with water, is most commonly achieved through the addition of gypsum to commercial portland cement. This material is normally added to the cement clinker before grinding. The cement manufacturers usually specify a sulfur trioxide content of about 36%. Excess sulfate in the form of hemihydrate can cause flash set in portland cement. Gypsum wallboard is widely used in the North American housing industry. Dehydration of the gypsum often results in the formation of a mixture of hemihydrate and anhydrite. All plasters eventually revert to gypsum on setting, the rate of transformation being dependent on the conditions of calcination. Gypsum has useful fire-resistant properties due to its water of crystallization. Gypsum plaster is widely used as an insulating material for protecting columns and beams of wooden materials from the high temperatures during a fire.

Supplementary Cementing Materials and Other Additions

This chapter explores that chemical admixtures, such as accelerators, retarders, water reducers, and superplasticizers are generally water soluble and are added in small amounts. They significantly affect the properties of concrete in the fresh and hardened states through physico-chemical and surface interactions. In contrast to chemical admixtures, materials such as fly ash, silica fume, blast furnace slag, natural pozzolans, and others are added in substantial amounts to concrete. Most of them react significantly with the components of the cement paste yielding higher strengths and better durability characteristics. They are used as cement replacement materials. These materials are known by various names. The European concrete standards refer to them as additions. The American society for testing and materials (ASTM) classifies them as mineral admixtures. In this chapter, these materials are referred to as supplementary cementing materials.

Introduction to Portland Cement Concrete

The performance of concrete depends on the quality of the ingredients, their proportions, placement, and exposure conditions. The cement type, nature of fine and coarse aggregates, water, temperature of mixing, admixture, and the environment determines the physical, chemical, and durability aspects of concrete. According to ASTM C-150, portland cement is a hydraulic cement produced by pulverizing clinker consisting essentially of hydraulic calcium silicates, usually containing one or more types of calcium sulfate as an inter-ground addition. The raw materials for the manufacture of portland cement contain, in suitable proportions, silica, aluminum oxide, calcium oxide, and ferric oxide. The raw materials also contain small amounts of other compounds such as magnesia, alkalis, phosphates, fluorine compounds, zinc oxide, and sulfides. The cement clinker is produced by feeding the crushed, ground, and screened raw mix into a rotary kiln and heated at a temperature of about 1300.1450°C. The chapter also focuses on major phases of portland cement: tricalcium silicate, dicalcium silicate, tricalcium aluminate, and ferrite phase of an average composition.

1 – Thermoanalytical Techniques

Publisher Summary This chapter provides an overview on thermoanalytical technique. Thermal analysis covers a variety of techniques that record the physical and chemical changes occurring in a substance as a function of temperature. Therefore, it encompasses many classical techniques such as thermogravimetry (TG), evolved gas analysis (EGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC), and the modern techniques, such as thermomechanical analysis (TMA) as well as dynamic mechanical analysis (DMA), and dilatometry. The application of thermal analysis to the study of construction materials stems from the fact that they undergo physicochemical changes on heating.