Eco-efficient concrete, optimized by Alfred’s particle packing model, with partial replacement of Portland cement by stone powder

The partial replacement of clinker by complementary cementitious materials can significantly contribute to the reduction of carbon emissions in the production of concrete. Another alternative to reduce these emissions is to increase the efficiency of the concrete, achieving higher compressive strength with lower consumption of cement. Particle packing models are efficient tools to optimize the composition of the matrix and contribute to the production of more eco-efficient concretes. In this context, the objective of the present study is evaluating the production of concretes with partial replacement of cement by stone powder, optimized by Alfred’s particle packing model, seeking to reduce cement consumption and CO2 emissions per MPa of compressive strength. The replacement content of cement by stone powder was 20% by mass (equivalent to 22.4% by volume). Concretes were produced with different distribution factor (q) - 0.37; 0.21; 0.45 - to verify the influence of fines on the flow between particles and on the efficiency of the produced concrete. The analyses were carried out in terms of properties in the fresh state, hardened state, and sustainability parameters (cement consumptions and CO2 emissions). The application of the proposed method resulted in a higher compressive strength than the expected for the water/cement ratio used (0.5). The most efficient concrete reached the compressive strength of 68 MPa with 240 kg/m3 of cement, which represents 3.5 kg of cement/m3/MPa and 3.1 kg of CO2/m3/MPa, a value below the references found in the literature for conventional concretes. Therefore, the proposed method allows to produce more eco-efficient concrete, contributing to the use of waste and reducing CO2 emissions.

Triazine Polymers for Improving Elastic Properties in Oil Well Cements

The oil well cement placed in the annulus between casings and the formations experience high stresses under downhole conditions. These frequent stresses deteriorate the mechanical properties of cement and lead to the formation of micro-cracks and fractures, which affect production and increases the cost of operation. Although several polymeric materials have been employed to improve tensile properties of the cement, these additives have also adversely affected the compressive strength of the cement. A highly stable polymeric additive, triazine-based polymers, is designed, synthesized, and compounded with the cement to improve the tensile properties of the well-cement. Triazine polymer was characterized by fourier transform infrared spectroscopy and thermogravimetric analysis. The triazine polymer was mixed with cement and the cement slurries were cured at 180 °F under 3000 psi for 3 days. The set-cement samples were subjected to mechanical testing under high temperature and high pressure to study the elastic properties of the cement. The introduction of this polymer into the cement has improved the elastic properties of the cement with minimum reduction in compressive strength. The thickening time, dynamic compressive strength development, rheology, fluid loss properties, and brazilian tensile strength of the control and cement with triazine polymers were studied to understand the effect of this newly developed polymeric additive. The molecular interaction of the triazine polymer with cement particles has shown formation of covalent linkage between the polymer and cement particle. We have observed a 15 % decrease in Young's modulus for cement compounded with 2%wt. of triazine polymer, indicating the introduction of elastic properties in wellbore cement.

Making the New Zealand House 1792 – 1982

<p>A systematic investigation was undertaken of the techniques (materials and technologies) used to construct the shell of the New Zealand house (envelope and interior linings) between 1792 and 1982. Using census, manufacturing and import statistics with analysis of local and international archives and publications, principal techniques were selected and documented. A review of local construction and building publications provide a background to the development of construction education and training, as well as the speed of change. Analysis of census data showed that from 1858 to 1981 the majority of dwelling walls in terms of construction (appearance) were timber, brick, board or concrete, while the structure was timber frame. Analysis of import data for seven materials (galvanised iron, asbestos cement, cement, window glass, wood nails, gypsum and roofing slate) from 1870 to 1965 found the UK was a majority supplier until 1925, except for USA gypsum. For the rest of the period, the UK continued to play a preeminent role with increasing Australian imports and local manufacture. Examination of archival and published information on techniques used for the sub-floor, floor, wall (construction and structure), fenestration, roof and thermal insulation provide an overview of country of orign, decade of arrival, spread of use and, if relevant, reasons for failure. Forty materials (including earth and brick, stone, cement and concrete, timber and ferrous metals) and twenty-four technologies are documented. Revised dates of first NZ use are provided for eight of these e.g. the shift from balloon to platform framing occurred in the early 1880s rather than 1890s. Three case studies examine different aspects of the techniques (nails 1860 to 1965, hollow concrete blocks 1904 to 1910 and camerated concrete 1908 to 1920). The research shows that timber was the predominant structural (framing) material from 1792 to 1982. From the 1930s there was a shift away from timber construction (external appearance) to a wider range of products, including brick, board (asbestos- and more recently fibre-cement) and concrete. A new chronological classification of house development is proposed. These techniques travelled in a variety of ways and at speeds which indicate over this time New Zealand was technologically well connected and supported an innovative construction sector. The techniques covered are: Boards: asbestos, and cellulose fibre-cement, particle, plywood, pumice, softboard, and hardboard; Bricks: double and veneer; Building paper; Cement and lime: local and imported; Concrete: hollow block, monolithic, reinforced, Camerated, Oratonu and Pearse patents; Fired earth: bricks and terracotta roof tiles; Floors: concrete slab, suspended, and terrazzo; Framing: balloon, braced, light steel, and platform; Insulation: cork, fibreglass, macerated paper, perlite, pumice, foil, and mineral wool; Iron and Steel: cast and wrought iron, steel; Linings: fibrous plaster, plasterboard and wet; metal tile, shingles and slates; Nails: cut, hand-made, wire and plates; Piles: concrete, native timber and stone; Roof: strutted and truss rafter; Roofing: aluminium, corrugated iron, ; Sub-floor: vapour barrier, walls and ventilation; Timber: air and kiln drying, glulam, native, pit-saw and preservative treatments; Wall constructions: earth, log, slab, solid timber, raupo and stone; Weatherboards; and Windows: glass, aluminium, steel and timber frames.</p>

Making the New Zealand House 1792 – 1982

<p>A systematic investigation was undertaken of the techniques (materials and technologies) used to construct the shell of the New Zealand house (envelope and interior linings) between 1792 and 1982. Using census, manufacturing and import statistics with analysis of local and international archives and publications, principal techniques were selected and documented. A review of local construction and building publications provide a background to the development of construction education and training, as well as the speed of change. Analysis of census data showed that from 1858 to 1981 the majority of dwelling walls in terms of construction (appearance) were timber, brick, board or concrete, while the structure was timber frame. Analysis of import data for seven materials (galvanised iron, asbestos cement, cement, window glass, wood nails, gypsum and roofing slate) from 1870 to 1965 found the UK was a majority supplier until 1925, except for USA gypsum. For the rest of the period, the UK continued to play a preeminent role with increasing Australian imports and local manufacture. Examination of archival and published information on techniques used for the sub-floor, floor, wall (construction and structure), fenestration, roof and thermal insulation provide an overview of country of orign, decade of arrival, spread of use and, if relevant, reasons for failure. Forty materials (including earth and brick, stone, cement and concrete, timber and ferrous metals) and twenty-four technologies are documented. Revised dates of first NZ use are provided for eight of these e.g. the shift from balloon to platform framing occurred in the early 1880s rather than 1890s. Three case studies examine different aspects of the techniques (nails 1860 to 1965, hollow concrete blocks 1904 to 1910 and camerated concrete 1908 to 1920). The research shows that timber was the predominant structural (framing) material from 1792 to 1982. From the 1930s there was a shift away from timber construction (external appearance) to a wider range of products, including brick, board (asbestos- and more recently fibre-cement) and concrete. A new chronological classification of house development is proposed. These techniques travelled in a variety of ways and at speeds which indicate over this time New Zealand was technologically well connected and supported an innovative construction sector. The techniques covered are: Boards: asbestos, and cellulose fibre-cement, particle, plywood, pumice, softboard, and hardboard; Bricks: double and veneer; Building paper; Cement and lime: local and imported; Concrete: hollow block, monolithic, reinforced, Camerated, Oratonu and Pearse patents; Fired earth: bricks and terracotta roof tiles; Floors: concrete slab, suspended, and terrazzo; Framing: balloon, braced, light steel, and platform; Insulation: cork, fibreglass, macerated paper, perlite, pumice, foil, and mineral wool; Iron and Steel: cast and wrought iron, steel; Linings: fibrous plaster, plasterboard and wet; metal tile, shingles and slates; Nails: cut, hand-made, wire and plates; Piles: concrete, native timber and stone; Roof: strutted and truss rafter; Roofing: aluminium, corrugated iron, ; Sub-floor: vapour barrier, walls and ventilation; Timber: air and kiln drying, glulam, native, pit-saw and preservative treatments; Wall constructions: earth, log, slab, solid timber, raupo and stone; Weatherboards; and Windows: glass, aluminium, steel and timber frames.</p>

Modelling the minislump spread of superplasticized PPC paste using Random forest, Decision tree and Multiple linear regression

Workability is one of the key property of concrete which is governed by water cement ratio. In order to improve the workability of concrete without any variations in water cement ratio Superplasticizers(SPs) are added. Cement paste helps us to analyze the property of fresh concrete where the dispersion of cement particle is taken into account. SP’s Cement dispersive properties are governed by dosage and the family. Various dosages and families of SP are considered for estimating workability feature of cement paste which is picked for investigating on rheological properties through Mini slump spread diameter. The prime motive of this analysis includes measuring the workability of different superplasticizers by conducting a minislump test and hence modelling the flow rate of the superplasticized Portland Pozzolona Cement (PPC)paste using the application of random forest(RF), decision tree(DT) and multiple regression algorithms. Testing and training data for a model were 287 unique mixture compositions at a water by cement ratio was 0.37. This mixture was tested experimentally in a laboratory using four types of locally available PPC’s and of SP which can be broadly categorised in to four families. Amount of seven types of SP brands, water content, cement weight were the input parameters for the model and flow rate was the output parameter. The model’s predicted and experimentally measured values of flow speed were compared and the amount of deviation was recorded.

Exploring the Influence Factors of Early Hydration of Ultrafine Cement

This work intends to contribute to the understanding of the influence factors of early hydration of ultrafine cement by focusing on the different fineness, different kinds of hardening accelerators, and different curing temperatures. Isothermal calorimetry, thermogravimetry, and X-ray diffraction (XRD) were performed to compare the hydration and chemical evolution of pastes containing accelerators with different fineness and curing temperatures; meanwhile, mechanical properties and water absorption were tested. The results showed that the cement fineness had a significant effect on the early hydration process; the smaller the cement particle size, the higher the early compressive strength. The 24 h compressive strength of ultrafine cement with a particle diameter of 6.8μm could reach 55.94 MPa, which was 118% higher than the reference cement. Water absorption test results indicated that adding 1% Ca(HCOO)2 to ultrafine cement can effectively reduce the water absorption, and it was only 1.93% at 28 d, which was 46% lower than the reference cement. An increase in curing temperature accelerated the activation of ultrafine cement in terms of the strength development rate, and the content of Ca(OH)2 in the ultrafine cement paste could reach 13.09% after being mixed with water for 24 h, which was 22% higher than that of the reference cement.

Simulation of Permeation of Saturated Cement Paste Based on a New Meso-scale Pore Network Model

This paper presents the simulation of the permeation of saturated cement paste based on a novel pore network model. First, a 2D hydration model of cement particles was developed by extending the work of Zheng et al. 2005 to provide the background for the network construction. Secondly, the establishment of the pore network model and simulation of permeation of saturated cement paste were carried out. The irregular pores between any two hydrated cement particles were linearized with clear distances as the diameters of pores. The straight tubular pores were interconnected with one another to form the network model. During this process, the weighted Voronoi diagram was employed to operate on the graphical expression of the hydrated cement particles. Water permeation in saturated cement paste was simulated to verify the pore network model. Finally, the factors including water–cement ratio, reaction temperature, reaction time and cement particle size that would influence water permeation were numerically investigated.

EMPLOYMENT OF MAGNETIC WATER TREATMENT IN CONSTRUCTION

Magnetic treatment (MT) is one of the interested techniques that have been widely used in various aspects of life due to its positive effectiveness on the properties of water when utilized. Construction sector received great attention by researchers in order to employ magnetic water (MW) in the production of various building materials especially cement-based materials. This is due to the role of water is involved directly in the hydration process of the cement as well as curing process. The effectiveness of using MW came from the influence of magnetic field (MF) on physical properties of water molecular such as surface tension. Break down in the size of water clusters, therefore, is occurred which increases the activity of water molecular to penetrate the cement particle easily to involve in the hydration process. Various parameters may affect the magnetization process such as time, strength of MF and speed of water through the MF. In the current paper, the impact of using MW in the production of various construction and building materials that based on cement is addressed to clarify the actual need in adopting such an attractive technology to magnetize the water to be used in mixing and curing cement-based materials to construct sustainable concrete structures in construction sites.