Biomineralization in cement-based materials has become a point of interest in recent years due to the possibility that such an approach could be used to develop a self-healing cement-based system. ...The objective of this study was to investigate the impact of vegetative cells of Sporosarcina pasteurii on the hydration kinetics and compressive strength of cement-based materials. The hydration kinetics were greatly influenced when a bacterial solution consisting of urea-yeast extract nutrient medium and vegetative cells was used to prepare bacterial cement pastes; specifically, severe retardation was observed. In addition, an increase in calcium carbonate precipitation, particularly calcite, occurred within the bacterial pastes. Furthermore, after the first day of hydration, the bacterial mortar displayed compressive strength that was similar to or greater than the compressive strength of the neat mortar.
•Characterized Sugar Cane Bagasse Ash (SCBA) material.•SCBA blended concretes exhibited higher Modulus of Rupture (MOR) than control.•P-SCBA concrete has higher Modulus of Elasticity (MOE) than ...control concrete.•Empirical equation is proposed to predict the MOR and MOE of SCBA blended concrete.•Established a relationship between MOR and MOE.
Sugar Cane Bagasse Ash (SCBA) is an advanced cementitious material contains significant amount of pozzolanic minerals like silica, alumina, etc. In view of this, in the present study it is proposed to partial replacement of Ordinary Portland Cement (OPC) by SCBA up-to 30%. OPC was replaced in two forms, namely, Original SCBA (O-SCBA) and Processed SCBA (P-SCBA). The mechanical properties such as cylinder compressive strength, Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) were evaluated for SCBA blended concrete and compared with conventional concrete. Further the relationships between cylinder compressive strength, MOR and MOE were established as per AS3600 (Australian Standards 3600), ACI318 (American Concrete Institute 318) and NZS3101 (New Zealand Standard 3101).
The low hydration and carbonation of reactive MgO cement (RMC) under ambient conditions causes prolonged setting and low compressive strengths (~4 MPa). This study proposed a unique technique which ...led to the enhancement of the hydration and carbonation processes via the synergistic combination of microbial carbonation process (MCP) with a hydration agent (HA) that enabled the self‑carbonation of RMC-based mixes without using of any special curing environments. Through hydrolysing urea (CO(NH2)2) using ureolytic bacteria, CO32− ions were produced to facilitate the carbonation of dissolved Mg2+ ions to form hydrated magnesium hydroxy carbonates (HMHCs). The self‑carbonation of RMC enabled by the MCP resulted in formation of brucite with a poor crystallinity and its rapid conversion into HMHCs, which improved the setting time and compressive strength of RMC-based samples. The simultaneous use of MCP with 2 M urea and HA revealed HMHCs with improved morphologies, resulting in the highest compressive strength (~15 MPa).
This research presents a new model for finding optimal conditions in the concrete technology area. To do that, results of a series of laboratory investigations on concrete samples were considered and ...used to design several artificial intelligence (AI) models. The data samples include 8 parameters i.e., silica fume replacement ratio, fly ash replacement ratio, fine aggregate, water content, high rate water reducing agent, coarse aggregate, total cementitious material, and age of samples, were used to predict and optimize the compressive strength of concrete samples. For optimization purposes, this study used a human learning optimization (HLO) algorithm to find the optimal results as well as optimizing the kernel coefficients of the support vector regression (SVR) models. Initially, to form the core of this research, various models were constructed and proposed to design the required relationship between the data using SVR. Since different SVR kernels have their own coefficients, using optimization theory, the probability of error in the models was reduced and the models were identified and executed with the highest accuracy. Finally, the polynomial model was selected as the model with the lowest computational error and the highest accuracy for evaluating the compressive strength of the concrete samples. The accuracy of the proposed SVR model for training and testing data was obtained as the coefficient of determination (
R
2
) = 0.9694 and
R
2
= 0.9470, respectively. This function was considered as a relation, to be developed by the HLO algorithm to find optimal options under different conditions. The results for 14 samples, which are the most important examples of this research, showed that the optimal states are obtained with a high level of accuracy. This confirms the proper use/develop of the SVR-HLO algorithm in designing the predictive model as well as finding optimal conditions in the concrete technology area.
A series of highly thermostable epoxy foams with diglycidyl ether of bisphenol-A and bisphenol-S epoxy resin (DGEBA/DGEBS), 4,4'-diaminodiphenyl sulfone (DDS) as curing agent have been successfully ...prepared through a two-step process. Dynamic and steady shear rheological measurements of the DGEBA/DGEBS/DDS reacting mixture are performed. The results indicate all samples present an extremely rapid increase in viscosities after a critical time. The gel time measured by the crossover of tan delta is independent of frequency. The influence of SiO sub(2) content on morphology, thermal, and mechanical properties of epoxy foams has also been investigated. Due to the heterogeneous nucleation of SiO sub(2), the pore morphology with a bimodal size distribution is observed when the content of SiO sub(2) is above 5 wt %. Dynamic mechanical analysis (DMA) reveals that pure epoxy foam possesses a high glass transition temperature (206 degree C). The maximum of specific compressive strength can be up to 0.0253 MPa m super(3) kg super(-1) at around 1.0 wt % SiO sub(2). copyright 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40068.
Management strategies for the safe disposal of contaminated dredged marine sediment constitute a global-scale environmental issue. The stabilization/solidification method was investigated as a ...sustainable approach to the recycling of the sediment as a construction material. A systematic study of the factors affecting the mechanical performance and contaminant release was performed. The physico-chemical variables selected to assess the potential re-use of the sediment treated with Ordinary Portland cement (OPC) and Ground Granulated Blast Furnace Slag (GGBS) in an aquatic environment were: curing duration (7, 28, 56 and 98 days), curing temperature (5, 20 and 40 °C) and ambient (leachate) pH (1, 4, 7 and 10). Unconfined compressive strength (UCS) tests were conducted and extended-duration tank leaching tests were used to characterize the long-term leaching of Al, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Ba, Pb. The results showed that S/S methods provide excellent immobilization of metals in marine sediment at a pH range of 4 to 10. Immobilization efficiencies of >99.9% for Mn, Fe, Zn, As, Ba, Pb and >97.8% for Al, Cu and Zn are reported over 100 days. GGBS replacement is an effective way to further improve sediment properties by enhancing strength, mitigating sediment alkalization and offering a better immobilization capacity for Fe, Ni and Zn. The release of metals (Al, Mn, Cu, As, Ba and Pb) was strongly associated with a coupling effect of the physico-chemical factors, with metal-specific responses to curing temperature, curing duration and pH. Mn mobility showed a dramatic sensitivity to ambient pH while Ba was less pH-dependent. Al release is related to strength and leached out by dissolution in all situations considered. Considering that dredged marine sediments may contain multiple metal contaminants which exhibit individual responses to remediation, treatment with GGBS may be considered a potentially suitable management option.
Display omitted
•Several factors influencing mechanical and leaching behavior of S/S sediments were studied.•GGBS replacement offers better fixation than OPC for Fe, Ni and Zn under any conditions.•Al release is related to strength and leached out by the way of dissolution.•Optimal temperature for GGBS mixes is effective for immobilizing Al, As, Ba, Pb.
This paper presents the hardened properties of a high-performance fibre-reinforced fine-aggregate concrete extruded through a 9mm diameter nozzle to build layer-by-layer structural components in a ...printing process. The printing process is a digitally controlled additive method capable of manufacturing architectural and structural components without formwork, unlike conventional concrete construction methods. The effects of the layering process on density, compressive strength, flexural strength, tensile bond strength and drying shrinkage are presented together with the implication for mix proportions. A control concrete (mould-cast specimens) had a density of approximately 2250kg/m3, high strength (107MPa in compression, 11MPa in flexure) and 3MPa in direct tension, together with a relatively low drying shrinkage of 175μm (cured in water) and 855μm (cured in a chamber at 20°C and 60% relative humidity) at 184days. In contrast well printed concrete had a density of 2350kg/m3, compressive strength of 75–102MPa, flexural strength of 6–17MPa depending on testing direction, and tensile bond strength between layers varying from 2.3 to 0.7MPa, reducing as the printing time gap between layers increased. The well printed concrete had significantly fewer voids greater than 0.2mm diameter (1.0%) when compared with the mould-cast control (3.8%), whilst samples of poorly printed material had more voids (4.8%) mainly formed in the interstices between filaments. The additive extrusion process was thus shown to retain the intrinsic high performance of the material.
Aims: To investigate the effect of adding nanoparticles on the compressive strength of alginate impression material. Materials and Methods: In this study, two types of nanoparticles were added to ...alginate impression materials: silver and zirconium oxide at four concentrations: 0.5 %, 1%, 2%, and 5% by weight. Compressive strength was tested for 45 samples made according to American Dental specification no.18 for the alginate impression material. Results: The addition of silver nanoparticles did not alter the compressive strength of alginate impression material, whereas the addition of zirconium oxide significantly decreased its compressive strength. Conclusions: The incorporation of silver nanoparticles into alginate impression materials as antimicrobial agents had no negative effect on its compressive strength, whereas adding antimicrobial zirconium oxide nanoparticles significantly reduced the compressive strength of alginate impression material
•An environmental friendly method for improving properties of RAC was suggested.•The proposed method significantly improved the mechanical properties of RAC.•The direct tensile strength of treated ...RAC at early age was higher than the splitting tensile strength.•The compressive strength of treated RAC was estimated at any age.•The relationships between mechanical properties of treated RAC were presented.
An environmental friendly method for enhancing mechanical properties of recycled aggregate concrete (RAC) is proposed by using sodium silicate and silica fume. The proposed method, applied to 100% coarse recycled concrete aggregate compared to untreated RAC, can improve compressive strength up to 33–50%, splitting tensile strength 33–41%, and elastic modulus 15.5–42.5%. Tests revealed that the direct tensile strength of RAC and natural aggregate concrete (NAC) were notably lower than the splitting tensile strength, but at 7 days, these values of treated RAC were higher than the splitting tensile strength. From the experimental data, the compressive strength of the treated RAC can be estimated at any age. Besides, the relationships between mechanical properties of treated RAC which were established were significantly different from those of NAC and untreated RAC in previous studies.
We investigate the dynamics of bright matter wave solitons in spin-1 BoseaEinstein condensates with time modulated nonlinearities. We obtain soliton solutions of an integrable autonomous ...three-coupled GrossaPitaevskii (3-GP) equations using HirotaE14s method involving a non-standard bilinearization. The similarity transformations are developed to construct the soliton solutions of non-autonomous 3-GP system. The non-autonomous solitons admit different density profiles. An interesting phenomenon of soliton compression is identified for kink-like nonlinearity coefficient with HermiteaGaussian-like potential strength. Our study shows that these non-autonomous solitons undergo non-trivial collisions involving condensate switching.
PDF
