Spectroscopic Studies on Indian Portland Cement Hydrated with Distilled Water and Sea Water

Strength characterization and sustainability assessment of coal bottom ash concrete

Coal bottom ash (CBA) which is waste and environment contaminant has been used in grinded and raw form as replacement of Portland cement (PC) and natural fine aggregates (NFA) in concrete. The combined effect of grinding period (GP) (2-10 h), grinded CBA (GCBA) (10-30%), and raw CBA (0-50%) on strength and microstructural characteristics was investigated and optimized along with its sustainability assessment. An enhancement in strength parameters with an increase in GP and replacement of PC and NFA with GCBA and CBA respectively was observed. The microstructural techniques like XRD, SEM, EDS, and FTIR also correlate with the aforementioned behavior. Mathematical models for strength parameters are well fitted and in good agreement with experimental and predicted values. Multi-objective optimization suggested 6.38 h grinding, 24.21% GCBA, and 32.96% CBA as the optimum values. CBA-based optimized mix resulted in 19.79% and 22.6% lower carbon footprints and eco-cost than the control mix.

Durability, thermo-physical characteristics, and mechanical strength prediction of green Portland cement matrix incorporating recycled soda-lime glass and lead glass

The current study is concerned with acid and calcination durability, thermal and thermo-physical properties, and mechanical strength prediction of mortars containing soda-lime glass (PVS) and lead glass (PVP). It demonstrates that up to 30% of PVP (PVP30) and PVS (PVS30) enhancements lessen the consequences of acid attack. In both cases, 20% additions show the best acid resistance at 2 days, but mortars with 10% addition resist better at 28 days. Furthermore, sulfuric acid damages the formed mortars more aggressively than hydrochloric acid. According to the thermal study, the loss of mass owing to calcination is reduced with increasing glass addition. It falls from 22% to -19.5% for PVS30 and -18% for PVP30. The flexural strengths of the calcined mortars significantly drop after firing, although the compressive strengths are higher at 400 °C than at ambient temperature. However, at 600 °C, a 20% glass addition retains the mortar's fire resistance. However, around 800 °C, all formulations mechanically deteriorate. PVP20 has the best fire behavior with relative variations of 48.6% at 400 °C, 18.5% at 600 °C, and -45.8% at 800 °C, while PVS20 has 45.4% at 400 °C, 24.8% at 600 °C, and -33.1% at 800 °C. The hydrates found in the calcined mortars emphasize autoclave reactions that improve mechanical characteristics between 400 and 600 °C, whereas at 800 °C, advanced dehydration of the matrix results in a generalized decrease in resistance. Furthermore, the gradual inclusion of glass reduces the thermal conductivity of mortars correspondingly. The inclusion of 30% PVS results in a reduction of -38.99%, while 30% PVP results in a reduction of -49.95%. The other thermophysical parameters are calculated as a function of these values. The models developed in the area of mechanical strength prediction using the Multilayer Perceptron (MLP) method of Artificial Neural Network (ANN) allow for R2 correlation coefficients of 0.86-0.92 during training with the database and 0.77 to 0.90 during validation, with values of MAE ≤ 2.12 and RMSE ≤ 2.67 in all situations.

Suitability of remediated heat-treated soil in concrete applications

Significant quantities of soil are adversely impacted by organic contaminants, including per- and poly-fluoroalkyl substances (PFAS). One proven technology for remediating PFAS affected soils is excavation and heat-treatment which destroys the PFAS, but renders the soil as an industrial waste that is normally diverted to landfill. This study investigated alternative uses for heat-treated industrial waste (HIW) soils as components in concrete, as aggregate replacement and as partial substitution of cement binder. At a replacement rate of 100% fine aggregate and ≈15% coarse aggregate, concretes made with HIW soil exhibited a strength of 47.2-48.3 MPa after 28 days' curing, compared with a reference concrete of 49.7-53.1 MPa, making the HIW ideal for aggregate replacement. Overall, the study demonstrated a novel, holistic approach to (1) remediating PFAS-affected soils, (2) diverting contaminated soil away from landfill, (3) reducing the use of high quality quarried concrete aggregates and (4) producing normal-strength concretes with a lower embodied carbon footprint than existing approaches. This study reveals that in Australia, up to 93% of all contaminated soil currently sent to landfill annually could instead be used a resource for mid-strength concretes, suitable for many applications.

Dielectric and Mechanical Properties of CTAB-Modified Natural Rubber Latex-Cement Composites

Cetyl trimethyl ammonium bromide (CTAB)-modified natural rubber latex/Portland cement paste (CTAB + NL/PC) composites were fabricated by varying the NL/cement and CTAB/cement ratios to improve the elastic property of PC. The stability and workability of the CTAB-modified NL particles in the PC matrix were significantly improved. The microstructure and dielectric property analyses of PC, CTAB/PC, NL/PC, and (CTAB + NL)/PC composites were performed to describe the interaction mechanism between the CTAB-modified NL and PC. The portlandite phase in PC was reduced by incorporating CTAB + NL. Although the tensile strength of NL/PC was significantly increased, its compressive strength also greatly decreased by ~40.3%. The tensile and compressive strengths of CTAB/PC were not significantly improved. Notably, the tensile strength of (CTAB + NL)/PC was significantly increased compared to those of PC, CTAB/PC, and NL/PC, while the depreciated compressive strength was only 18.7%. The optimized compressive–tensile performance of (CTAB + NL)/PC was equal to that of PC. The dielectric constants of NL/PC, CTAB/PC, and (CTAB + NL)/PC were reduced due to the low dielectric constant of NL and the ability of CTAB to capture negative charges in the PC matrix, leading to a reduction in the negative surface charges and hence the interfacial polarization. This result was confirmed by the decreased loss tangent in a low-frequency range, which is usually reduced by decreasing the free charges. This work provides a comprehensive guideline for significantly improving the elastic property of PC while retaining a high compressive strength.

Effect of partially replacing ordinary Portland cement with municipal solid waste incinerator ashes and rice husk ashes on pervious concrete quality

Pervious concrete (PC) provides multiple benefits, including reducing stormwater runoff, purifying water, recharging groundwater, and reducing the heat island effect. This study aims to determine an effective way to reuse municipal solid waste incinerator (MSWI) fly ash (FA), MSWI bottom ash (BA), and rice husk ash (RHA) as single or binary partial replacements for ordinary Portland cement (OPC) in PC. The ashes and PC specimens were characterized via X-ray fluorescence spectroscopy, X-ray powder diffraction, field emission-scanning electron microscopy, and Fourier transform infrared spectroscopy. The compressive strength, water permeability, and toxicity characteristic leaching procedure (TCLP)-released metals were investigated to evaluate the PC quality. The main components of the ashes were similar to those of OPC, suggesting that the ashes could be reused as cement materials; however, the cementitious activity of the ashes, especially MSWI FA, was relatively low. All ashes except 1100 °C MSWI FA met the standard requirements and can be applied as pozzolanic materials. The three PC specimens with binary replacements containing RHA (550, 700, and 900 °C) and MSWI BA (1100 °C) showed a synergistic effect and exhibited a higher 90-day compressive strength than the other specimens with single and binary ash replacements containing RHA (550 and 900 °C). The water permeability ranged between 0.106 and 0.391 cm/s, and the TCLP-released metal concentrations from all specimens met the regulatory standards of Taiwan. The results indicated that replacement with MSWI BA and RHA in cement materials provides an acceptable compressive strength and water permeability.

The effects of seawater and nanosilica on the performance of blended cements and composites

This study investigates the effects of seawater and nanosilica (3% by weight of cement), on the fresh and hardened properties of cement pastes and mortars produced with two types of low heat cements: Portland pozzolana cement (CEM II) and blast furnace cement (CEM III). The heat of hydration, initial and final setting times, rheological properties, strength development, sorptivity and water accessible porosity of the cement pastes and mortars were determined. The data reveal that cement type has a significant effect on the reaction rate of cement with seawater and nanosilica (NS). Specimens produced with slag-blended cement exhibited a higher cement reaction rate and the composite produced exhibited better mechanical performance, as a result of the additional reaction of alumina rich phases in slag, with seawater. Replacement of freshwater with seawater contributes mostly to a significant improvement of early strength. However, in the case of slag-blended cement, 28 day strength also improved. The incorporation of NS results in additional acceleration of hydration processes, as well as to a decrease in cement setting time. In contrast, the addition of NS results in a noticeable increment in the yield-stress of pastes, with this effect being pronounced when NS is mixed along with seawater. Moreover, the use of seawater and NS has a beneficial effect on microstructure refinement, thus improving the transport properties of cement mortars. Overall, the study has showed that both seawater and NS can be successfully used to accelerate the hydration process of low heat blended cements and to improve the mechanical and transport properties of cement-based composites.

Novel calcium phosphate coated calcium silicate-based cement: in vitro evaluation

Calcium silicate-based cements are known for their wide applications in dentistry and orthopedics. The alkaline pH (up to 12) of these cements limits their application in other orthopedic areas. In this study, the effect of dicalcium phosphate dihydrate (DCPD) coating on set cement on pH reduction and biocompatibility improvement was examined. Samples with 0 and 10 weight ratio DCPD were prepared and characterized by XRD, FTIR, and SEM. The DCPD coating on the set cement was performed by a 7 d immersion in 1% monocalcium phosphate (MCP) solution and characterized by XRD, FTIR, SEM, and EDX. Also, the compressive strength and cytotoxicity of the samples were tested. The results showed that DCPD coating did not significantly change the compressive strength of the cement, but by decreasing the pH of the culture medium to the physiological range, it led to enhance adhesion, spreading and proliferation of human osteosarcoma cell line (Saos-2). The novel DCPD coated calcium silicate-based cement could be served as a bulk or porous bone substitute and scaffold.

The effects of seawater on the hydration, microstructure and strength development of Portland cement pastes incorporating colloidal silica

This contribution investigates the effects of seawater and colloidal silica (NS) in the amounts of 1, 3 and 5 wt%, respectively, on the hydration, strength development and microstructural properties of Portland cement pastes. The data reveal that seawater has an accelerating effect on cement hydration and thus a significant contribution to early strength development was observed. The beneficial effect of seawater was reflected in an improvement in compressive strength for up to 14 days of hydration, while in the 28 days compressive strength values were comparable to that of cement pastes produced with demineralized water. The combination of seawater and NS significantly promotes cement hydration kinetics due to a synergistic effect, resulting in higher calcium hydroxide (CH) production. NS can thus react with the available CH through the pozzolanic reaction and produce more calcium silicate hydrate (C-S-H) gel. A noticeable improvement of strength development, as the result of the synergistic effect of NS and seawater, was therefore observed. In addition, mercury intrusion porosimetry (MIP) tests confirmed significant improvements in microstructure when NS and seawater were combined, resulting in the production of a more compact and dense hardened paste structure. The optimal amount of NS to be mixed with seawater, was found to be 3 wt% of cement.