Showing papers on "Cement published in 2016"
TL;DR: In this article, the authors summarized and examined the scientific advances in the preparation, properties and applications of fly ash-based geopolymer and proposed a new green cement based on fly ash.
578 citations
TL;DR: In this paper, the authors investigated the role of the structural build-up properties of concrete and cement-based materials in a layer-by-layer construction technique and proposed a theoretical framework to optimize the building rate.
Abstract: Additive manufacturing and digital fabrication bring new horizons to concrete and cement-based material construction. 3D printing inspired construction techniques that have recently been developed at laboratory scale for cement-based materials. This study aims to investigate the role of the structural build-up properties of cement-based materials in such a layer by layer construction technique. As construction progresses, the cement-based materials become harder with time. The mechanical strength of the cement-based materials must be sufficient to sustain the weight of the layers subsequently deposited. It follows that the comparison of the mechanical strength, which evolves with time (i.e. structural build-up), with the loading due to layers subsequently deposited, can be expected to provide the optimal rate of layer by layer construction. A theoretical framework has been developed to propose a method of optimization of the building rate, which is experimentally validated in a layer-wise built column.
550 citations
TL;DR: In this article, a review summarises the state of the art regarding the understanding and consequences of carbonation of cement paste and summarises recent efforts regarding active use of carbonations as a tool for manipulating certain properties of cement based materials.
387 citations
TL;DR: In this article, a summary of research progress on plant-based natural fibre reinforced cement-based composites is presented, which includes the use of natural fibres as internal curing agents and durability enhancement materials.
Abstract: The quest for sustainability in construction material usage has made the use of more renewable resources in the construction industry a necessity. Plant-based natural fibres are low cost renewable materials which can be found in abundant supply in many countries. This paper presents a summary of research progress on plant-based natural fibre reinforced cement-based composites. Fibre types, fibre characteristics and their effects on the properties of cement-based materials are reviewed. Factors affecting the fresh and hardened properties of cement-based composites reinforced with plant-based natural fibre are discussed. Measures to enhance the durability properties of cement-based composites containing plant-based natural fibres are appraised. Significant part of the paper is then focused on future trends such as the use of plant-based natural fibres as internal curing agents and durability enhancement materials in cement-based composites. Finally, applications and recommendations for future work are presented.
374 citations
TL;DR: In this paper, the authors investigated the use of coal ash in concrete to replace sand with bottom ash waste and cement with fly ash and concluded that those experimental concrete mixes can be used in several structures (foundations, subbases, pavements, etc.) which will minimize the cost, energy and environmental problems to a great extent.
324 citations
Shenyang Jianzhu University1, Chinese Academy of Sciences2, University of California, Irvine3, Centre national de la recherche scientifique4, University of Cambridge5, University of East Anglia6, Shenyang Agricultural University7, Kyonggi University8, University of Aberdeen9, Spanish National Research Council10, Shenyang Pharmaceutical University11, California Institute of Technology12, Harvard University13
TL;DR: In this paper, the authors use new and existing data on cement materials during cement service life, demolition, and secondary use of concrete waste to estimate regional and global CO_2 uptake between 1930 and 2013 using an analytical model describing carbonation chemistry.
Abstract: Calcination of carbonate rocks during the manufacture of cement produced 5% of global CO_2 emissions from all industrial process and fossil-fuel combustion in 2013. Considerable attention has been paid to quantifying these industrial process emissions from cement production, but the natural reversal of the process—carbonation—has received little attention in carbon cycle studies. Here, we use new and existing data on cement materials during cement service life, demolition, and secondary use of concrete waste to estimate regional and global CO_2 uptake between 1930 and 2013 using an analytical model describing carbonation chemistry. We find that carbonation of cement materials over their life cycle represents a large and growing net sink of CO_2, increasing from 0.10 GtC yr^(−1) in 1998 to 0.25 GtC yr^(−1) in 2013. In total, we estimate that a cumulative amount of 4.5 GtC has been sequestered in carbonating cement materials from 1930 to 2013, offsetting 43% of the CO_2 emissions from production of cement over the same period, not including emissions associated with fossil use during cement production. We conclude that carbonation of cement products represents a substantial carbon sink that is not currently considered in emissions inventories.
313 citations
TL;DR: In this article, the authors summarized the existing knowledge regarding the carbonation of cement-based materials and identified the areas which require further investigations, including the potential of CO 2 storage in concrete and the newly developed carbonate binders.
311 citations
TL;DR: In this article, the impact of supplementary cementitious materials (SCMs) on the pore solution composition of blended cements is reviewed, leading to a set of practical guidelines and recommendations.
Abstract: This paper is the work of working group 3 of the RILEM Technical Committee on Hydration and Microstructure of Concrete with SCM (TC 238-SCM). The pore solution is an essential but often overlooked part of hydrated cements. The composition of the cement pore solution reflects the ongoing hydration processes and determines which solid phases are stable and may precipitate, and which phases are unstable and may dissolve. The study of the cement pore solution therefore contributes to the understanding of the mechanisms as well as of the kinetics of cement hydration. This paper reviews the impact of supplementary cementitious materials (SCMs) on the pore solution composition of blended cements. In a first part, the extraction and analysis methods of cement pore solutions are reviewed, leading to a set of practical guidelines and recommendations. In a second part, an extensive literature survey is used to document the effect of the addition of SCMs (blast furnace slag, fly ash and silica fume) on the pore solution. Finally, in a third part the collected literature data are compared to thermodynamic simulations. The performance and current limitations of thermodynamic modelling of blended cement hydration are demonstrated and discussed in view of future progress.
300 citations
TL;DR: In this article, the use of waste glass powder obtained from grinding of crushed containers and building demolition to produce glass powder blended cement as concrete additives was evaluated in terms of physical and mechanical properties.
292 citations
TL;DR: In this paper, the effects of different factors on the strength, reaction rate, hydration products and microstructure were examined; these factors include the activator dosage, FA/slag ratio, and curing regime.
241 citations
TL;DR: In this article, the authors present a concise review of various studies that have indicated the utilization of various industrial waste products in the synthesis of geopolymers, which can be used effectively as source material for geopolymerization.
TL;DR: In this article, Na 2 CO 3 -activated slag cements were produced from four different blast furnace slags, each blended with a calcined layered double hydroxide (CLDH) derived from thermally treated hydrotalcite.
TL;DR: In this paper, the effects of RCA on the measured mechanical and durability properties of geopolymer concrete containing recycled coarse aggregate (RCA) are presented. But the correlation between the compressive strength and the sorptivity is not that strong.
Abstract: This paper presents mechanical and durability properties of geopolymer concrete containing recycled coarse aggregate (RCA). The RCA is sourced from local construction and demolition (C&D) waste in Perth, Australia. The RCA is used as a partial replacement of natural coarse aggregate (NCA) in geopolymer concrete at 15%, 30% and 50% by wt. which corresponds to series two, three and four, respectively, while the geopolymer concrete containing 100% NCA is control and is considered as the first series. Class F fly ash is used as the source material for the geopolymer and 8 M sodium hydroxide and sodium silicate alkali activators are used to synthesise the fly ash geopolymer in this study. In all four series a constant alkali activator to fly ash ratio is used. Compressive strength, indirect tensile strength and elastic modulus of above geopolymer concrete are measured at 7 and 28 days, while sorptivity, immersed water absorption and volume of permeable voids of above geopolymer concrete are measured at 28 days. Relevant Australian standards are used to measure all the above properties except the sorptivity which is measured according to ASTM standard. Results show that the compressive strength, indirect tensile strength and elastic modulus of geopolymer concrete decrease with an increase in RCA contents, which is also true for both 7 and 28 days. Excellent correlations of compressive strength with indirect tensile strength and elastic modulus are also observed in geopolymer concrete containing RCA. Existing empirical models for cement concrete and geopolymer concrete containing NCA underestimate and overestimate the indirect tensile strength and elastic modulus, respectively of geopolymer concrete containing RCA. The measured durability properties such as sorptivity, water absorption and volume of permeable voids of geopolymer concrete were also adversely affected by the incorporation of RCA and these properties increase with an increase in RCA contents. The effects of RCA on the measured mechanical and durability properties of geopolymer concrete follow similar trend in cement concrete. Very good correlations of compressive strength with volume of permeable voids and water absorption of geopolymer concrete containing RCA are also observed, while the correlation between the compressive strength and the sorptivity is not that strong.
TL;DR: In this article, the carbonation behaviors of hydraulic and non-hydraulic calcium silicate phases, including tricalcium silicate (3CaO·SiO2 or C3S), γ-dical calcium silicates (γ-2C2S, β-C 2S, and β-c2S), rankinite (3CO·2SiO 2 or c3S2), and wollastonite (CaO•SiO•O 2 ) were investigated.
Abstract: This paper presents a study on the carbonation behaviors of hydraulic and non-hydraulic calcium silicate phases, including tricalcium silicate (3CaO·SiO2 or C3S), γ-dicalcium silicate (γ-2CaO·SiO2 or γ-C2S), β-dicalcium silicate (β-2CaO·SiO2 or β-C2S), rankinite (3CaO·2SiO2 or C3S2), and wollastonite (CaO·SiO2 or CS). These calcium silicate phases were subjected to carbonation reaction at different CO2 concentration and temperatures. Thermogravimetric analysis (TGA) tests were performed to quantify the amounts of carbonates formed during the carbonation reactions, which were eventually used to monitor the degree of reactions of the calcium silicate phases. Both hydraulic and non-hydraulic calcium silicates demonstrated higher reaction rate in case of carbonation reaction than that of the hydration reaction. Under specific carbonation scenario, non-hydraulic low-lime calcium silicates such as γ-C2S, C3S2 and CS were found to achieve a reaction rate close to that of C3S. Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscope (SEM) tests were performed to characterize the carbonation reaction products of the calcium silicate phases. The FTIR spectra during the early stage of carbonation reaction showed formation of calcium silicate hydrate (C–S–H) from C3S, γ-C2S, β-C2S, and C3S2 phases with a similar degree of polymerization as that of the C–S–H that forms during the hydration reaction of C3S. However, upon further exposure to CO2, these C–S–H phases decompose and eventually converted to calcium-modified (Ca-modified) silica gel phase with higher degree of silicate polymerization. Contradictorily, CS phase started forming Ca-modified silica gel phase even at the early stage of carbonation reaction. This paper also revealed the stoichiometry of the Ca-modified silica gel that formed during the carbonation reaction of the calcium silicate phases using the SEM/energy dispersive spectroscopy (EDS) and TGA results.
TL;DR: In this article, three methods to improve and then assess the mechanical performance of CRC have been examined namely, rubber pre-treatment using sodium hydroxide (NaOH) solution, using silica fume additives, and increasing concrete cement content.
TL;DR: In this article, the performance of several non-proprietary blends are investigated by assessing the materials' resistance to freeze-thaw cycles, ingress of chlorides as well as the presence and distribution of air voids.
Abstract: Ultra-high performance concrete (UHPC) achieves extraordinary strength characteristics through optimization of the particle packing density of the cementitious matrix. The dense matrix also promotes exceptional durability properties and is arguably the biggest benefit of the material. A durable concrete enables structures to last longer, reduces the cost of maintenance and helps achieve a significantly more sustainable infrastructure. To assess the durability of UHPC, the performance of several non-proprietary blends are investigated by assessing the materials' resistance to freeze-thaw cycles, ingress of chlorides as well as the presence and distribution of air voids. The main experimental variables are cement type and the quantity of silica powder, which varies from 0% to 25% of the cement weight. All mixes displayed negligible chloride ion penetration and high resistance to freeze-thaw with mass loss well below the limit in over 60 cycles of freeze-thaw. Analysis of the test data indicates that the silica powder content has little influence on performance.
TL;DR: A green ultra-high-performance glass concrete (UHPGC) with a compressive strength of up to 220 MPa was prepared and its fresh, mechanical, and microstructural properties were investigated as discussed by the authors.
TL;DR: In this article, the effects of limestone filler (LF) and slag (GGBS) on chloride migration and water absorption of concretes with systematically varied aggregate properties were evaluated from the view point of ITZ by using BSE image, EDS, and MIP analysis.
TL;DR: In this paper, the authors investigated the effect of nano-TiO2 (NT) and rice husk ash (RHA) on the strength and durability of mortars and found that 15% RHA and 5% NT can be considered as a suitable replacement regarding to the economic efficiency and hardened properties.
TL;DR: In this article, the authors investigated the effects of the belite content and carbonation curing on the physicochemical properties of cement mortar and showed that a higher alite content in cement increases CO2 uptake during the carbonation-cured process and thus promotes microstructural densification.
TL;DR: In this article, the authors studied the environmental benefits of incorporating different percentages of two types of fly ashes that can be used in concrete as cement replacement, and they showed that both ashes provide a benefit for the concrete production both in terms of environmental impact minimization and a better environmental performance through an increase in cement replacement.
TL;DR: In this article, a method was developed to assess the details of the economic and environmental potential of the specific Limestone Calcined Clays Cement LC3 technology in the Cuban context.
TL;DR: In this article, the current state of knowledge on durability of concrete and mortar made up of pozzolans as a partial replacement of Portland Cement is reviewed based on published documents and several potential studies have been suggested for the future research.
TL;DR: In this paper, the effect of GO on the hydration of cement was evaluated by XRD and FTIR, and it was found that GO can remarkably accelerate hydration rate of cement due to its catalytic behavior.
TL;DR: In this article, carbon fibers with hydrophilic surface modification were added into cement mortar through ultrasonic treatment to examine the reinforcing effect of carbon fiber, and the results showed that the enhancing mechanism of carbon fibers on the properties of cement mortar analyzed by the calculated fiber numbers per unit volume, average center distance between two carbon fibers and the critical pullout length well matches the experimental results.
TL;DR: In this paper, the effect of addition of rice husk ash, pond ash, cement and fiber on the compaction and strength behavior of clay has been studied, and the results show that the inclusion of fiber reinforcement within un-cemented and cemented soil caused an increase in the axial strain at failure, decreased the stiffness and the loss of post-peak strength, and changed the cementing soil brittle behavior to a more ductile one.
TL;DR: In this paper, a review of agro-waste materials used as a partial replacement of fine aggregate in concrete is presented, where different properties of fresh and hardened concrete, their durability and thermal conductivity when admixed with agrowastes are reviewed.
Abstract: High demand of natural resources due to rapid urbanization and the disposal problem of agricultural wastes in developed countries have created opportunities for use of agro-waste in the construction industry. Many agricultural waste materials are already used in concrete as replacement alternatives for cement, fine aggregate, coarse aggregate and reinforcing materials. This paper reviews some of the agro-waste materials, which are used as a partial replacement of fine aggregate in concrete. Different properties of fresh and hardened concrete, their durability and thermal conductivity when admixed with agro-wastes are reviewed. Agro-waste used in self-compacting concrete and mortar are also reviewed and their properties are compared. It has been seen that the agro-waste concrete containing groundnut shell, oyster shell, cork, rice husk ash and tobacco waste showed better workability than their counterparts did. Agro-waste concrete containing bagasse ash, sawdust ash and oyster shell achieved their required strength by 20% of replacement as fine aggregate, which were maximum among all agro-waste type concrete. Close relations were predicted among compressive strength, flexural strength, tensile strength, ultrasonic pulse velocity and elastic modulus of agro-waste concrete. Addition of bagasse ash as fine aggregate in mortar increased the resistance of chloride penetration whereas inclusion of cork in mortar showed better thermal resistance and improved cyclic performance. After the review, it is of considerable finding that more research is deserved on all fine aggregates replacing agro-waste materials, which can give more certainty on their utilization in concrete.
TL;DR: In this article, the early age hydration mechanisms of accelerated CEM I pastes were evaluated using liquid phase analysis, conductimetry, isothermal calorimetry and in situ XRD and SEM.
TL;DR: In this paper, a liquid alkaline activator comprising sodium silicate solution (Na 2 SiO 3 ) and sodium hydroxide (NaOH) was used for the alkali activation of the CCR-based geopolymers.
TL;DR: In this paper, the in situ performance of concrete containing glass powder (GP) used as a partial replacement of cement at various construction sites (in Quebec-Canada between 2006 and 2012), including interior and exterior slabs and structural wall elements.