On Ordinary Portland Cement Research Articles

Non-conventional mineral binder-bonded lignocellulosic composite materials: A review

The construction industry suffers from unsustainability and contributes more than any other industrial sector to carbon emissions that lead to global warming. Increasing economic and environmental concerns related to conventional energy- and CO2-intensive building materials have propelled the rapid and sustained expansion of research in the area of plant-based inorganic mineral binder-bonded materials for the construction industry. The resulting composites can be qualified as eco-responsible, sustainable, and efficient multifunctional building materials. So far, most of these research efforts have not received as much attention as materials based on ordinary Portland cement (OPC). To address this gap, this review focuses on mineral binder-based lignocellulosic composites made from non-conventional inorganic mineral binders/ cements with low embodied energy and low carbon footprint, namely hydrated lime-based binders, magnesium-based cement, alkali-activated cement, and geopolymers, as sustainable alternatives to OPC-bonded lignocellulosic composites (state-of-the-art). The emphasis here is on the application potentials, the influence of production parameters on the material properties/ performance, and recent advancement in this field. Finally, a prediction is provided of future trends for these non-conventional mineral binder-bonded lignocellulosic composites.

A Review of the Mechanical Properties and Durability of Ecological Concretes in a Cold Climate in Comparison to Standard Ordinary Portland Cement-Based Concrete.

Most of the currently used concretes are based on ordinary Portland cement (OPC) which results in a high carbon dioxide footprint and thus has a negative environmental impact. Replacing OPCs, partially or fully by ecological binders, i.e., supplementary cementitious materials (SCMs) or alternative binders, aims to decrease the carbon dioxide footprint. Both solutions introduced a number of technological problems, including their performance, when exposed to low, subfreezing temperatures during casting operations and the hardening stage. This review indicates that the present knowledge enables the production of OPC-based concretes at temperatures as low as −10 °C, without the need of any additional measures such as, e.g., heating. Conversely, composite cements containing SCMs or alkali-activated binders (AACs) showed mixed performances, ranging from inferior to superior in comparison with OPC. Most concretes based on composite cements require pre/post heat curing or only a short exposure to sub-zero temperatures. At the same time, certain alkali-activated systems performed very well even at −20 °C without the need for additional curing. Chemical admixtures developed for OPC do not always perform well in other binder systems. This review showed that there is only a limited knowledge on how chemical admixtures work in ecological concretes at low temperatures and how to accelerate the hydration rate of composite cements containing high amounts of SCMs or AACs, when these are cured at subfreezing temperatures.

One-part eco-cellular concrete for the precast industry: Functional features and life cycle assessment

This paper focuses on investigating greener alternatives of cellular concrete technology to fulfil current searches for a shift to circular economy. A novel one-part eco-cellular concrete (ECC-OP) was developed and studied. The one-part alkali activated materials (AAM-OP) and new alkali-activated cellular concrete (AACC) technologies were combined to develop greener alternative of cellular concrete production. The progressive steps from traditional cellular concrete (TCC) based on ordinary Portland cement (OPC) and commercial aluminium powder (A) to a 100% waste-based cellular concrete are presented. Blast furnace slag (BFS) was the precursor, RHA was employed as the silica source, olive stone biomass ash (OBA) was the alkali source and recycled aluminium foil (AR) was employed as an aerating agent. The functional features of the materials were studied and compared to those established by the European standard and the American Concrete Institute (ACI) Committee 523 guides. The new ECC-OP with a bulk density, compressive strength and thermal conductivity that respectively equal 660 kg/m3, 6.3 MPa and 0.20 W/mK was obtained. Finally, a cradle-to-gate life cycle assessment (LCA) was made, where the industrial process of a masonry unit manufacture was raised by using each studied material. A 96% reduction in the kgCO2eq per m3 of material was reached with the new proposed ECC-OP compared to TCC manufacturing.

Bonding Strength Characteristics of FA-Based Geopolymer Paste as a Repair Material When Applied on OPC Substrate

This investigative study aims to study the mechanical and morphological properties of fly ash (FA)-based geopolymer paste as a repair material when applied on ordinary Portland cement (OPC) overlay concrete. The first part of this study investigates the optimal mix design of FA-based geopolymer paste with various NaOH concentrations of 8, 10, 12, and 14 M, which were used later as a repair material. The second part studies the bonding strength using a slant shear test between the geopolymer repair material and OPC substrate concrete. The results showed that a shorter setting time corresponds to the higher NaOH molarity, within the range of 53 and 30 min at 8 and 14 M, respectively. The compressive strength of FA-based geopolymer paste was found to reach 92.5 MPa at 60 days. Also, from the slant shear test results, prism specimens with 125 mm length and 50 mm wide have a large bond strength of 11 MPa at 12 M. The scanning electron microscopy/energy-dispersive X-ray (SEM/EDX) analysis showed that the OPC substrate has a significant effect on slant shear bond strength, where the presence of free cations of Ca2+ on the OPC substrate surface contributed to the formation of calcium alumina-silicate hydrate gel (C-A-S-H) by building various cross-links of Ca-O-Si.

Influence of Chloroprene Rubber Latex on Set Times and Early Hydration of Cement

This study was carried out in order to investigate retardation time of chloroprene rubber (CR) latex on the cementitious system in relation to its effect on the heat of hydration of cementitious system. Set times, consistency and heat evolution tests were carried out on ordinary Portland cement (OPC). Three different curing environments were selected with different CR to cement ratio i.e., 0%, 5%, 10%, 15% and 20%. The data revealed that consistency was increased under high temperature and low relative humidity for cement pastes. While achieving standard consistency, water required by the controlled specimen was reduced by 43% with the addition of 20% CR latex. Regarding heat of hydration, it was found that heat of hydration of latex-modified cement pastes was higher than the controlled cement paste after 48 h.

Severe Sulfuric Acid Attack on Self-Compacting Concrete with Granulometrically Optimized Blast-Furnace Slag-Comparison of Different Test Methods.

The corrosion by severe sulfuric acid attack at pH 2 of two self-compacting concrete (SCC) types that are based on ordinary Portland cement (OPC) and granulometrically optimized blast-furnace slag cement was evaluated by three complementary tests that were performed in different research institutes. The use of SCC is a smart and promising solution to improve the performance of concrete in an aggressive environment, especially regarding ready-mixed concrete applications, since good compaction is less dependent on workmanship. The relevance and practical advantages of the different test protocols and the influence of the experimental parameters are discussed. It appears that the frequency of renewing the acid solution during the exposure period is the main parameter that influences the mass loss and the rate of degradation, while the sample geometry and the ratio between the volume of solution and concrete surface area had no clear influence. Nevertheless, there was reasonable agreement between the methods regarding the magnitude of the concrete degradation (resulting in a mass loss of about 2.5 kg/m² in six months time). The use of granulometrically optimized slag cement provided a moderate increase of the concrete resistance against acid attack, and this practice might be recommended in order to increase the durability of structures exposed to sulfuric acid media. The fact that the difference in comparison with SCC-OPC was rather limited shows that the influence of the cement type becomes less relevant in the case of concrete with low w/c ratio and optimized concrete technology.

Evaluation of the combination of desert sand and calcium sulfoaluminate cement for the production of concrete

The production of concrete requires large quantities of sand. At first sight, sand seems to be a cheap, widely available and abundant resource, however, in some regions of the earth sand is getting rare because of the high demand. An alternative might be desert sand, which is available from many sources around the world, but is not yet widely used in concrete due to its narrow particle size distribution.In this study, a new concept of combining desert sands with a binder based on calcium sulfoaluminate cements (CSA) and gypsum is tested to obtain a suitable workability and packing density and hence allows for a high sand replacement level in standard concrete. Unlike typical CSA applications, a high gypsum content is used in order to produce a large amount of ettringite, which is able to bind large quantities of mixing water.The concept is applied on a series of pastes and concretes with different standard sand replacement levels. A very fine quartz sand is used as a model desert sand. Mechanical properties (compressive and bending strength) are determined and compared to reference systems based on ordinary Portland cement (OPC). It is shown that the formation of ettringite is capable to fill the voids between the small and narrow-sized desert sand particles leading to a very dense microstructure. Drying shrinkage data show volumetric stability and reduced shrinkage. Owing to the low CSA dosage and the low carbon dioxide emissions related to CSA production, the proposed concrete mixtures can be regarded as eco-friendly.

The Effect of Sodium Gluconate on Pastes’ Performance and Hydration Behavior of Ordinary Portland Cement

The goal of this paper provides better understanding of the effect of sodium gluconate (SG) on ordinary Portland cement (OPC) hydration behavior. Pastes’ performances of ordinary Portland cement, including setting time at 20°C and 35°C curing temperature, mechanical strength, fluidity, and zeta potential are studied. Furthermore, the effects of SG on cement hydration behaviors are investigated by the means of isothermal calorimetry measurements, X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). The results show that SG is difficult to maintain significant retarding effect at the temperature of 35°C compared to that at the temperature of 20°C. SG is able to reduce the cement cumulative hydration heat and delay the occurrence time of heat evolution peak in a certain extent, but it has little impact on reducing the cement evolution rate peak. The effects of SG on mechanical properties and dispersion properties of cement depend on its dosages. Specifically, the positive effect occurs when the addition dosage is less than 0.15% (i.e., by cement weight), but the negative effect emerges if the addition dosages exceed this limitation. Similarly, SG plays different roles on cement hydration at different hydration periods. It inhibits the hydration of C3S and the formation of portlandite (CH) at the early hydration period. On the contrary, it promotes the C3S hydration when hydration time is beyond 1 d. Meanwhile, SG also plays different roles on cement hydration at different dosage additions. Specifically, SG promotes ettringite (AFt) formation at the dosage less than 0.06%, but it inhibits AFt formation at the dosage more than 0.06%.

Influence of Lysinibacillus sphaericus on compressive strength and water sorptivity in microbial cement mortar

Cement structures are subject to degradation either by aggressive media or development of micro/macro cracks which create external substance ingress pathways. Microbiocementation can be employed as a self-intelligent solution to this deterioration process. This paper presents study results on the effects of Lysinibacillus sphaericus microbiocementation on Ordinary Portland cement (OPC), normal consistency, setting time, soundness, compressive strength and water sorptivity. Microbial solutions with a concentration of 1.0 × 107 cells/ml were mixed with OPC to make prisms at a water/cement ratio of 0.5. Mortar prisms of 160 mm × 40 mm x 40mm were used in this study. A maximum compressive strength gain of 17% and 19.8% was observed on the microbial prism at the 28th and 56th day of curing respectively. A minimum of 0.0190 and a maximum of 0.0355 water sorptivity coefficient was observed on the OPC microbial prism and OPC control prism, after 28th day of curing respectively. Scanning electron microscope images taken after the 28th day of curing showed formation of vast calcium silicate hydrates and more calcite deposits on microbial mortars. Statistical findings of this study indicate that Lysinibacillus sphaericus significantly retarded both the setting time and normal consistency, but has no influence on the mortar soundness.

Influence of dolomite on the properties and microstructure of alkali-activated slag with and without pulverized fly ash

In this work, dolomite or a combination of dolomite and pulverized fly ash is to substitute up to 40% of blast-furnace slag in sodium hydroxide and sodium carbonate-activated slag systems. The influence of dolomite incorporation on the strength development, flowability, setting time, pore structure, hydrated phase assemblage, and microstructure of alkali-activated slag (AAS) are studied. The results show that dolomite incorporation up to 20% or up to 40% when fly ash is present, has little detrimental effects on the compressive strength of AAS pastes. Dolomite works mainly as an inert filler in AAS systems, leading to an increased reaction of slag at early stages due to filler effect. Different from its chemical role on ordinary portland cement (OPC) systems with enhanced hydrotalcite formation, the dolomite does not substantially affect the chemistry of reacted products in AAS systems at room temperature.

Mechanism for rapid hardening of cement pastes under coupled CO2-water curing regime

A coupled CO2-water curing regime was employed on Ordinary Portland cement (OPC) paste samples immediately after casting, which allowed carbonation and hydration of OPC to proceed simultaneously. The strength development and microstructural evolution was evaluated by using multiple-techniques. The results indicated that, compared to the normal hydrated counterpart, a lower porosity, higher amorphous phase content and overall reaction degree can be achieved in the coupled CO2-water cured OPC sample. By combining with the morphological observations, a new mechanism was proposed for the rapid hardening of OPC. It is shown that the carbonation reactions led to the formation of calcite particles, which provided more nucleating sites for CSH gel growth; and thus, an increase in the overall reaction degree of the cement paste can be achieved within the first 24 h compared to the conventional water curing process.

Effect of temperature on bond characteristics of geopolymer concrete

This paper presents experimental results on the bond behavior between geopolymer concrete and rebar. Pull-out tests on geopolymer concrete specimens embedded with plain and ribbed rebars were carried out at ambient temperature and after exposure to 100, 300, 500 and 700 °C. Two batches of geopolymer concrete with compressive strength of 48 and 64 MPa respectively, and five rebar diameters (of 10, 12, 14, 18 and 25 mm) were used for preparing the test specimens. Comparative benchmark tests were also conducted on ordinary Portland cement (OPC) concrete specimens. Results from these tests show that geopolymer concrete exhibits insignificant reduction in bond strength till exposure to 300 °C, but undergoes significant degradation beyond 300 °C. Data from the tests indicate that rate of bond strength degradation in geopolymer concrete is close to that of splitting tensile strength, but higher than that of compressive strength. Also, results infer that geopolymer concrete exhibits similar or better bond properties than OPC concrete, both at ambient temperature and after exposure to elevated temperatures. Thus geopolymer concrete can be a practical alternative to OPC concrete in reinforced concrete structures when fire resistance is one of the main design considerations.

Influence of raw meal compaction pressure on OPC clinker mineral composition and heat flow

In this paper, the results of compaction pressure influence on ordinary Portland cement (OPC) clinker mineral formation and heat flow evaluating calcination temperature and duration were determined using the industrial initial mixture for OPC clinker burning. Raw meal samples were pressed to 4–20 MPa and calcined at temperatures of 1300, 1350, 1400, and 1450 °C for 20, 40, and 60 min. Raw materials and products were analysed by chemical, XRD, Rietveld and STA analyses. Heat release of the products during hydration reactions was determined by isothermal microcalorimetry. Sample pressing at yet low pressure (4 MPa) accelerates the synthesis of clinker minerals and decreases the amount of free CaO by ~0.5%. However, further increase in the pressure has no major influence on the clinker mineral formation. Hydration reactions of the pressed OPC clinker samples are slightly more intensive compared to powder ones; therefore, it is presumable that cement stone hardening processes would be intensified as well.

Strength and Porosity of Materials on the Basis of Blast Furnace Slag Activated by Liquid Sodium Silicate

This study investigates the effect of different admixtures on strength and porosity development of mortars and pastes based on alkali activated blast furnace slag (AABFS). Fluidized bed combustion fly ash and by-pass cement kiln dust were used to replace slag in the binder by 5%wt. and 10%wt., respectively. Pure slag mortar was also modified by a shrinkage reducing admixture. The use of all the admixtures resulted in a reduction in early age strength, while only shrinkage reducing admixture had significant impact on pore size distribution. Properties of AABFS based specimens were compared to those of specimens based on ordinary Portland cement (OPC).

Shrinkage behaviour and related corrosion performance of low-pH cementitious materials based on OPC or CAC

Prior to using low-pH cementitious materials in underground repositories for high level waste, the characteristics determining their long-term durability must be analysed in depth. In this sense, different shrinkage tests have been made on mortar and concrete specimens using low-pH cement formulations based on ordinary portland cement (OPC) or calcium aluminate cement (CAC), with high mineral admixtures contents. They showed similar autogenous shrinkage than samples without mineral admixtures but higher drying shrinkage when materials based on OPC with high silica fume contents were considered. Besides, as the use of reinforced concrete could be required in underground repositories, the susceptibility of reinforcement to corrosion when using low-pH cementitious materials based on OPC was analyzed, considering carbon steel and galvanized steel. In the formers corrosion was detected due to the low pore solution pH but any problem was detected when galvanized reinforcement were used.

Study on a high strength ternary binder cured under different conditions

High strength ternary binder based on ordinary Portland cement (OPC), calcium aluminate cement (CAC) and calcium sulfate (CS) is used as repair materials. However, temperature and humidity govern the strength of this binder. In addition, the proportions of OPC–CAC–CS have strong influence on the fluidity, setting time and mechanical properties of the system. The mortars with the ternary binder were cured under different conditions in this study. Then the compressive strength and the restrained expansion rate at different ages were evaluated. The results show that high strength binder was obtained using the proportion of 82%–10%–8% of the OPC–CAC–CS system. The early compressive strength under steam curing was higher than that of under standard curing, but a contrary result was occurred at 28days and the strength did not decrease under dry curing. The expansion rates of the mortars increased with the increase of time under both the standard and the steam curing, but decreased in the dry oven. XRD, TG and SEM show that a relationship between the content and microstructure of ettringite and calcium hydroxide was found when the samples were cured under different temperatures and humidity.

Resistencia a la corrosión ácida de morteros de cementos adicionados con catalizador de craqueo catalítico gastado (sFCC)

El catalizador de craqueo catalitico gastado (sFCC) es un residuo producido por la industria petroquimica y ha demostrado una elevada potencialidad como adicion puzolanica en mezclas de cemento Portland (OPC). El presente articulo evalua la eficacia del sFCC como adicion mineral activa en morteros de cemento Portland, asi como la resistencia al ataque quimico cuando los materiales producidos son inmersos en acido sulfurico (H2SO4), acetico (CH3COOH) o clorhidrico (HCl). Se llevo a cabo una comparacion del desempeno del sFCC como adicion frente a adiciones comercialmente disponibles, tales como humo de silice (SF) y metacaolin (MK). Los resultados revelan un incremento en las resistencias mecanicas de hasta un 17% en morteros con sFCC en comparacion a un mortero referencia sin adicion (OPC). La inmersion en H2SO4 durante 90 dias condujo a la formacion de yeso y perdida de resistencias mecanicas de hasta un ~25% en las mezclas con MK y sFCC. Para las muestras inmersas en HCl y especialmente las constituidas con sFCC y MK, se identifico Sal de Friedel, como consecuencia del ingreso de Cl- y posterior reaccion con los monosulfoaluminatos formados durante la hidratacion del cemento. La inmersion en acido acetico condujo a perdidas de resistencia de hasta un 57% para OPC y 37% para morteros adicionados con sFCC. De esta manera, la inmersion en HCl promueve el mayor ataque para los sistemas adicionados y posterior deterioro, seguido del CH3COOH y H2SO4. Se destaca el mejor desempeno del mortero con 20% sFCC, en particular en presencia de acido sulfurico. Rev. ing. constr. [online]. 2015, vol.30, n.3, pp. 169-176. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732015000300002

On the Development of a Nomogram for Alkali Activated Fly Ash Material (AAFAM) Mixtures

Alkali activated fly ash material (AAFAM) has become the most promising material to substitute materials based on ordinary Portland cement (OPC). However, there is no available nomogram for AAFAM mixtures. In contrast, there are many rational methods available in the literature to make paste, mortar and concrete with OPC based materials, such as Monteiro-Helene's nomogram, which uses Abram's law, Lyse's law and Molinari's law. This paper presents a study to construct such a nomogram for AAFAM mixtures by first conducting experiments on the paste and mortar phases. The procedure of Monteiro-Helene's nomogram was adopted in this formulation. The first step in this direction was to find a close relationship between the strength and paste composition of the material that can be used as a substitute for Abram's law. The second step was to construct the equivalent of Lyse's and Molinari's relationships by varying the sand and fly ash contents. The results show that it is possible to make a nomogram for AAFAM mixtures such as the one for OPC based materials. Class F fly ash and its mortar phase were used to construct the nomogram. In addition, the mortar samples that were used to build the nomogram had similar solidification products according to their microscopic characteristics.

HYDRATION AND MICROSTRUCTURAL PROPERTIES OF CEMENT PASTE CONTAINING NANO AND MICROSILICA

The influence of nano-and microsilica addition on ordinary Portland cement (OPC) pastes has been studied in terms of hydration and microstructural properties. Three different combinations of nano-and microsilica mixes were used. A constant water-binder ratio of 0.35 was maintained throughout the experiment. All samples were tested for initial and final setting time and compressive strengths were determined at the age of 3, 7, 28, and 90 days of hydration. The hydration products were examined by SDT and XRD analysis at various curing ages. The inclusion of nano-and microsilica reduced the initial and final setting time significantly, increased the compressive strength of hardened cement paste after 7 days of hydration, and reduced the amount of calcium hydroxide in the hardened paste compared to mixes without these nanoparticles.

COMPARISON OF FATIGUE PARAMETERS OF ALKALI-ACTIVATED AND ORDINARY PORTLAND CEMENT BASED CONCRETES

Concretes used in civil structures are usually made on ordinary Portland cement (OPC) base. Alkali activated concretes (AAC) are considered as a perspective building materials. They show high strength, good durability, and good resistance to aggressive agents etc. This paper introduces the values of the basic fatigue parameters of both types of concrete; the alkali-activated concrete is prepared as a new material for the potential production of concrete elements developed by ZPSV, a.s. company. The concrete mixtures have a similar utilization and therefore the fatigue parameters can be compared. The specimens were prepared and tested under static (compressive strength) and cyclic loading (fatigue parameters Wohler curve). The experimentally obtained results (mechanical and fatigue) of both types of concrete are compared and the suitability of these types of composites for their application is discussed.