Effect of C-S-H-PCE and TEA on performances of lithium slag-cement binder

Limestone is commonly used in cement concrete due to its unique nature and type. It has physical effects (nucleation effect and dilution effect) and chemical effects on the hydration process of cement. This paper reviews the effects of three representative limestone materials on the hydration process, hydration products, and hydration kinetics. In the hydration process, the reaction was delayed by limestone powder with a particle size larger than 20 μm and calcium carbonate whiskers due to their dilutive effect. On the other hand, limestone powder with a particle size smaller than 20 m and calcium carbonate nanoparticles facilitated the reaction through nucleation and chemical effects. Limestone has a similar effect on hydration products, promoting the production of C-S-H through nucleation. The mechanism of action for this nucleation effect depends on the differences in crystalline form and particle size of the three types of micro- and nano-calcium. Chemical effects impact the amount of AFt produced, with the generation of new products being the main reaction influenced by the limestone admixture.

In order to enhance the early hydration evolution as well as improve the fluidity property of cement paste, calcium silicate hydrates (C-S-Hs)/polycarboxylate (PCE) was self-synthesised by way of the co-precipitation method, and was added into cement paste. The rheological performance and hydration process of the cement paste were analysed. Results showed that adding C-S-Hs–PCE could improve the rheological performance of cement paste. With a low amount of C-S-Hs–PCE adopted, the viscosity and shear stress reduced slightly, while a high amount of C-S-Hs–PCE led to sharply decreased viscosity and shear stress. Adding C-S-Hs–PCE could shorten the cement hydration induction period and improve the hydration heat release rate significantly. The crystalline nuclei provided by C-S-Hs–PCE promoted the nucleation growth of hydration products. When C-S-Hs–PCE content increased, the hydration reaction products in the hardened cement slurry increased remarkably, and a large number of hydration products effectively filled into the micro-pores, leading to reduced large pores and increased nanopores. Adding 1.0% C-S-Hs–PCE increased compressive strength at 1 day by 12.9%, the 3 day compressive strength by 18.2%, 7 day compressive strength by 20.5% and 28 day compressive strength by 12.6%. The findings could provide a theoretical reference for the performance regulation of cementitious materials.

Cement-emulsified asphalt (CEA) has been widely used in slab ballastless track and asphalt pavement cold recycling projects because of its high stiffness and toughness. In CEA material, emulsifiers and asphalt affect the cement's hydration process and microstructure. Thus, to further investigate the effects of anionic emulsifiers (AEs) and anionic emulsified asphalt (AEA) with different demulsification rates on the hydration process and microstructure of cement, two types of AE (rapid-setting and slow-setting) and their corresponding AEA were used to prepare modified cement pastes. First, it was confirmed that the AEs and AEA delayed cement hydration by measuring the setting time, X-ray diffraction (XRD) patterns, and electrical resistivity of the cement paste. Then, the microstructure of the cement paste was determined with mercury intrusion porosimetry (MIP) and a scanning electron microscope (SEM), and it was found that AEs and AEA have varying degrees of inhibitory effects on the formation of the cement paste microstructure. Finally, based on the energy dispersive spectrometer (EDS) element content of the cement paste and Fourier transform infrared spectroscopy (FTIR) on the two AEs, the inhibition mechanism of AE and AEA with different demulsifier rates on the cement hydration process was analyzed. The experimental results showed that both AEs and AEA delayed the hydration process of cement to varying degrees and altered the microstructure of cement, and slow setting anionic emulsified asphalt (SAEA) had the greatest impact on the hydration process and microstructure of cement. Compared to pure cement paste, the initial setting time of cement paste mixed with SAEA was delayed by 73.9%, and the final setting time was delayed by 66.7%. After adding SAEA, the most probable aperture of the cement paste increased from 62.50 nm to 71.19 nm after one day of hydration. Due to the fact that there were more carboxyl groups with negative charges, more -COO- was adsorbed onto the surface of cement particles in the slow-cracking anionic emulsifier (SAE); compared with the rapid-setting anionic emulsifier (RAE) and the rapid-setting anionic emulsified asphalt (RAEA), the SAE and the SAEA had a stronger delaying effect on the hydration reaction of cement.

Formation of synthetic C-S-H in the presence of triethanolamine and/or polycarboxylate polymers

Mechanism of triethanolamine on Portland cement hydration process and microstructure characteristics

Glutinous rice porridge is widely used to mortar formulations in ancient China, and it is significant to understand the interaction between amylopectin and cement pastes. X-ray diffraction analysis, field emission scanning electron microscope (FESEM) analysis and atomic force microscopy (AFM) analysis are used to investigate hydration products in the cement pastes modified by amylopectin in this article. The results show that the hydration products in modified cement pastes were same with those in the unmodified cement paste. However, the growth of hydration products, such as calcium hydroxide (CH), calcium silicate hydrate (C-S-H) and entringite (AFt), are strongly influenced by amylopectin in glutinous rice. And the heavily branched structure of amylopectin is the crucial parameter for the specific control of the size and morphology of hydration products.

Investigation on the early proceeding of cement hydration containing dispersed nano Calcium Silicate Hydrated (CSH) seeds

Rheological behaviour, mechanical performance, and anti-fungal activity of OPC-granite waste composite modified with zinc oxide dust

Magnesium oxysulfate (MOS) cement is often seen as a ‘green engineering material in the twenty-first century’. However, low mechanical strength is one of the major drawbacks for large-scale applications of MOS cement. In this paper, MOS cement with desirable strength was prepared by adding phosphoric acid. The effects of phosphoric acid on the hydration process, hydration products and microstructure of MOS cement were studied in detail using isothermal calorimetry, X-ray diffraction, Fourier transform infrared spectrometry, mercury intrusion porosimetry and scanning electron microscopy. It was found that the incorporation of phosphoric acid could retard the hydration process and increase the setting time of MOS cement. Furthermore, the incorporation of phosphoric acid was shown to increase the compressive strength through its effect in promoting the formation of 5Mg(OH)2·MgSO4·7H2O. The space-filling properties and directional growth characteristics of 5Mg(OH)2·MgSO4·7H2O contributed to a more compact and uniform microstructure of the MOS cement formed.

The compressive strength development always go along with the microstructure development in concrete through the process of cement hydration. In the hydrated products of cement, calcium silicate hydrate (C-S-H) forms a network of nanoparticles so C-S-H gel is the main compound giving compressive strength of concrete. As we know that C-S-H gel produced by the reactions with water of two main minerals in cement such as Tricalcium Silicate () and Dicalcium Silicate (). In addition, the increase of C-S-H content in concrete due to the pozzolanic reaction of the pozzolan with calcium hydroxide (CH). With the aim of this research is quantitative study of hydration of and in the Reactive Powder Concrete (RPC) together with its compressive strength development, three concrete formulas were estimated in this study which made from three different types of cement ownership different mineral compositions content were tested on compressive strength and on heat flux emitted from hydration process by isothermal calorimetry. The purpose of measuring heat flux emitted from chemical reaction process in concrete is to verify the hydration kinetic model for portland cement containing the silica fume. Basing on this simulation program, the amount of C-S-H gel in concrete is calculated. The research results showed that the the C-S-H content formed in binder paste of RPC is proportional to compressive strength development. The (Ordinary Portland Cement) OPC with higher content have compressive strength development earlier.

Influence of triethanolamine on reactivity of hydrated matrix in sodium silicate self-healing system and the mechanism

Effects of nano-silica modification on early age hydration process in winter construction of tunnel engineering

This study investigated the influence of adding nano silica (SiO2) on the cement hydration process, particularly on the formation of calcium silicate hydrate (C-S-H) at different stages of hydration. The study investigated the effect of adding nano-silica on the mechanical properties of the hardened cement corresponding to the formation of C-S-H during the hydration process of a cement paste. Specimens made up of four different percentage of nano silica (0%, 1%, 3% and 5%) were tested at different stages of hydration ranging from 3 to 56 days. The effect of nano-silica on the compressive strength, stressstrain, and elastic modulus of nano-cement was examined using MTS and Forney testing machines. The signature phase and formation of C-S-H and calcium hydroxide (CH) were monitored using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The study also investigated the effect of curing method (vacuum and water curing) on the strength development. The experimental results show that the formation of calcium silicate hydrate (C-S-H) increases significantly during the early stages of hydration which correspond to the drastic increase in compressive strength. The formation of C-S-H continues to increase throughout the 56 days but at a moderate rate. The results reveal that 1% of nano silica by volume of cement is the optimum ratio that yields the maximum strength. The results also indicated that the strength of the traditional water cured specimens were higher than that of vacuum cured specimens.

Carbon Nanotubes (CNTs) were discovered by Ijima in 1991. They have remarkable properties such as high surface area and flexural strength, which is twenty times higher than steel. Additives with such qualities are required in concrete, mortar and other construction materials to improve the performance of the binder system. For future applications, the knowledge of interactions between hydrating tricalcium silicate (C3S) as a main component of cement and CNTs is very important. Therefore, a better understanding of the hydration mechanism and the nucleation in presence of CNTs is needed. The influence of multiwalled carbon nanotubes (MWCNTs) on the crystallinity of portlandite (calcium hydroxide) during C3S hydration has been observed in previous experiments as well as an influence on the mechanical properties. Flexural strength increases up to 45% with samples including MWCNTs and C3S. This observation has led to the assumption that the carbon nanotubes are incorporated into the micro- and nanostructure of the hydrated clinker phase. The growth of hydration products on MWCNTs is shown by AFM-images. Previous research activities focused on the influence of CNTs on portlandite which is one of the main reaction products in cement hydration. The calcium silicate hydrates (CSH) phases are important for strength development in cementitious binder systems.In this work, we investigated the influence of the CNTs on the CSH by combined spectroscopic methods. Recent 29Si MAS NMR experiments indicate an incorporation of MWCNTs into the CSH-phases by a change of the silica tetrahedra Q n distribution and line broadening as a result of a paramagnetic interaction of CNTs. This shows that the CNTs are homogeneous embedded in the CSH phases. IR measurements support these results. Measurements of the hydration kinetics by calorimetric methods have proved acceleration. The ability of the CNTs to function as nucleation sites is as well a reason for this change in the hydration rate.

Hydration and microstructure of ternary high-ferrite Portland cement blends incorporating a large amount of limestone powder and fly ash