Advances in Cement Research
ISSN / EISSN : 0951-7197 / 1751-7605
Published by: Thomas Telford Ltd. (10.1680)
Total articles ≅ 1,251
Latest articles in this journal
Advances in Cement Research pp 1-35; https://doi.org/10.1680/jadcr.21.00040
The evolution of internal temperature and relative humidity distributions in initially saturated normal concrete and mortar cubes of 0.4, 0.5 and 0.6 w/c ratios stored in an indoor residential environment were recorded for over a year. Measurements at regular intervals were taken at six different depths from the exposed drying surface in each specimen. Results reveal that, the internal temperature at all depths in mortar and concrete samples followed the transitions of ambient temperature closely irrespective of the w/c ratio. While the effect of w/c ratio on the mean internal relative humidity in mortar was statistically negligible, it became discernible in concrete at points where the medium had relatively lower saturation levels and when the effect of evaporation was low due to a low ambient temperature. Higher dosages of Polycarboxylic ether based superplasticizer was observed to delay the drop of internal relative humidity. The recorded values of internal relative humidity over the period of study were found to be conducive for the onset and propagation of carbonation induced corrosion. A two parameter linear model for the prediction of critical drying time with respect to spatial distance from drying surface is also proposed.
Advances in Cement Research pp 1-24; https://doi.org/10.1680/jadcr.21.00112
A theoretical model is presented to predict the water permeability of nano-reinforced cement pastes from its pore structure, including the pore size distribution, pore interconnection, porosity and microcracks. The model is based on the General Effective Media (GEM) theory and multifractals, which considers both the bridging roles in microcracks and capillary pores and the filling roles in the nano gel pore of nano-admixtures reinforcing cement pastes. For comparison, a hybrid graphene oxide, multi-walled carbon nanotube was selected as a nano-reinforced material mixed into cementitious composites, for the water permeability experiments. The calculated results show good agreement with the experimental measurements, decreasing the maximum error from 67.8% to 9.7%, compared with the previously proposed GEM theory. Moreover, the theoretical calculation results suggest that the reinforcing roles of nano-admixtures in cement paste to strengthen the permeability-related properties may be mainly due to the bridging effects in microcracks and capillary pores, rather than filling the nano gel pores. The findings of this study enrich our understanding of the mechanism of nano-admixture reinforcing cement-based materials and can measure the permeability of cementitious composites directly, instead of using time-consuming methods.
Advances in Cement Research pp 1-35; https://doi.org/10.1680/jadcr.21.00106
As the primary material for the structure of infrastructures, the steel bar reinforced cement-based composite's durability in the service environment is a crucial topic. The application of bio-mineralization technology shows great prospects in improving the properties of the cement-based materials. Therefore, in this study, we excavate the underlying mechanism by investigating the effects of factors on the gradient mineralization at the surface layer of cement-based materials. The following four parts were studied to conform with the process of bacterial action: the absorption of CO2 from air, transformation of CO2 to HCO3-, adsorption of Ca- from the pore solution of cement-based materials and formation of CaCO3 in pores, which results in the decrease of porosity. The content of CaCO3 and porosity indicated that bacteria could regulate the gradient mineralization at the surface of cement-based materials. For further prediction, numerical calculations and experimental measurements were conducted.
Advances in Cement Research pp 1-37; https://doi.org/10.1680/jadcr.20.00038
This research aims to develop 3D printed high-performance cementitious composite reinforced with polyvinyl alcohol (PVA) and polypropylene (PP) fibres. Characteristics of fresh mortar are identified by conducting the rheological behaviour, flow factor, and green strength tests. Mechanical properties of 3D printed specimens under different curing conditions are also investigated in different printing directions, which are compared with those of cast specimens. The presence of fibre with relatively small volume fraction (0.2%) leads to a noticeable increase in yield stress, flow loss and green strength. For hardened cementious composite (CC), the influence of a small amount of PVA and PP fibre is not significant for both compressive and flexural strengths of printed samples. The results of the mechanical properties of cast and printed specimens at the hardened state could be further explained through the pore content measured by using X-ray micro-computed tomography.
Advances in Cement Research pp 1-44; https://doi.org/10.1680/jadcr.21.00127
To study effects of limestone powder with different fineness on packing density, strength and hydration behaviors of cement blending high-volume limestone powder, Vicat setting time test, strength test, isothermal calorimetry and scanning electron microscopy were employed. Results showed that cement replacement by limestone powder with smallest median particle size had the largest packing densities in three different fineness of limestone powder replacement. The compressive strength of blended cement mortar increased with the increasing of limestone powder fineness. Furthermore, packing densities of blended cement could be used to infer the evolution of mechanical strength of the blended cement mortar. The addition of limestone powder with smaller median particle size than that of cement accelerated the hydration of cement in acceleration period. Compared to limestone powder with smaller median particle size than that of cement, the producing rate of nuclei of cement blending limestone powder with larger median particle size than that of cement decreased with increasing amount of limestone powder replacement, while growth rate of nuclei increased with increasing amount of limestone powder replacement.
Advances in Cement Research pp 1-36; https://doi.org/10.1680/jadcr.21.00134
In this study, waste glass was alkali-activated by activators with different amounts of sodium hydroxide and subjected to aging. The chemical reactions and resulting microstructures and properties of the alkali-activated glass inorganic binders (AAGIBs) were affected by aging temperature and duration. An activation energy approach was employed to evaluate the effects of aging temperature and duration on the 4-day compressive strengths of the AAGIB specimens. When the amount of sodium hydroxide in the activators was low, the activation energies for the dissolution and polycondensation reactions of the AAGIBs were 83.3 and 44.6 kJ/mol, respectively. As AE% in the activators increased, the microstructure of the hardened binder became destroyed because of vigorous stirring during aging. Consequently, the activation energy of the AAGIB polycondensation reaction increased to 76.2 kJ/mol when AE% greater than 5%.
Advances in Cement Research pp 1-11; https://doi.org/10.1680/jadcr.18.00149
In this study, a new type of soap-free inorganic/organic composite latex(SBML-II) was prepared by soap-free emulsion polymerization method using sodium p-styrenesulfonate(SSS) and modified SiO2 as copolymer emulsifiers, which were characterized by fourier transform infrared spectrometer(FT-IR), transmission electron microscope(TEM), thermo gravimetric analysis(TGA) and other means. Then the latex were employed to prepare polymer latex modified oil well cement and evaluate the influence of the latex on the basic properties of cement slurry,mechanical properties and microstructure of cement matrix. The characterization of SBML-II showed that the synthesized latex present typical core-shell structure and possess better dispersibility, stability and excellent thermal stability than the conventional latex(SBML-I). At same time, the SBML-II latex is easier to form membranous morphology than SBML-I at the same temperature and has better compatibility with additives and resistance to ions. Performance evaluation in cement slurry and cement matrix evidenced that the SBML-II has good dilution effect on cement slurry and excellent potential to improve the mechanical properties of cement matrix. Meanwhile, the addition of SBML-II is helpful to improve microstructure due to the film formation in cement matrix.
Advances in Cement Research pp 1-27; https://doi.org/10.1680/jadcr.20.00064
The combination of glass powder with pozzolanic additions to replace clinker can develop new types of binders (ternary cement) with improved physical and mechanical properties, and enabling the reduction of clinker and natural resources consumption, and the minimisation of the CO2 emissions. In this context, the present work is an attempt to study the influence of glass powder (GP), with two different specific surface area (Blaine) GP30 = 300 m²/kg and GP45 = 450 m²/kg, combined with slag (S), on the mechanical behavior and durability of mortars. The mechanical properties were investigated using the compressive and flexural strength tests. In addition, aspects related to durability were examined as well by the water-accessible porosity, capillary absorption and sorptivity tests. The replacement rate of cement by glass powder varied from 10% to 20% and the proportion of slag was fixed at 10%. The results obtained showed that a binary mortar made with (20% GP45) replacement showed increases in 90-days compressive strength, while the ternary mortar with (20% GP45 +10% S) replacement gave the best result. The same trend is also valid for durability properties examined in this study. As well as, the combined use of GP and slag at 30% replacement levels seemed to give better instead of using GP alone.
Advances in Cement Research, Volume 33, pp 342-356; https://doi.org/10.1680/jadcr.19.00118
Among the several schemes that have been reported to be a satisfactory alternative to Portland cement is Alkali Activated Cement (AAC), which has recently started to gain greater consideration in construction sectors. Conventional two-part alkali activation has many drawbacks, including the activating solution being viscous, problematic and non-user friendly to handle. Thus, this research aims to produce a one-part alkali activated metakaolin/natural pozzolan, by using an earth alkaline source (rich in CaO) from waste material (lime kiln dust), as an activating precursor to break the alumina-silicate crystalline phases. Thermal treatment of materials at two levels of treatment (450°C and 950°C), was used as an assisted activation approach. Analytical techniques including X-Ray powder diffraction XRD, Thermogravimetric Analysis TG-DTA, Fourier Transform Infrared Spectroscopy FTIR and Scanning Electron Microscope SEM, were utilised to investigate the performance of the developed materials at a molecular level. Reduction of crystalline peaks as well as the appearance of new wollastonite minerals within the calcined lime kiln dust, contributed to the development of 27 MPa compressive strength after 28 days. The dissolution made through the pozzolanic reaction as well as thermal treatment evidently contributed to transform crystalline to amorphous phases.
Advances in Cement Research, Volume 33, pp 367-376; https://doi.org/10.1680/jadcr.19.00135
Different liquid accelerators including Sodium Aluminate liquid accelerator (SAa), Fluoaluminate liquid accelerator (Fa) and Aluminum Sulfate liquid accelerator (ASa) were selected to investigate their influences on the carbonation properties and morphology of C3A and C3S hydration products. After accelerated carbonation test, the relative contents of ettringite (AFt), calcium hydroxide (CH) and calcium carbonate (CaCO3) in the hydration products of C3A and C3S samples were analyzed by thermogravimetric analysis (TG). The results indicated that the hydration products of C3A and C3S with liquid accelerators were easier to be carbonated, and the promotion effect of SAa was the most obvious. The morphology of hydrated products of C3A and C3S was observed by scanning electron microscopy analysis (SEM). It was observed that different liquid accelerators had different influence on the morphology of C3A and C3S hydration products. Among them, ASa had the greatest influence on the morphology of C3A and C3S hydration products, and experiments proved that ASa could promote the transformation of AFt into AFm and make the CH crystal structure become thicker and larger.