Compressive Strength Of Portland Cement Research Articles

Effect of brick powders of various purities on hydration and compressive strength of Portland cement

AbstractThe availability of common supplementary cementitious materials (SCMs), as slags and fly ashes, is expected to reduce in the future. Among potential new SCMs, brick powders (BPs) have gained considerable attention. To study the effect of BPs as potential SCMs three BPs of different contamination were used for the experiments. The investigations included the R3 test as well as isothermal heat flow calorimetry and compressive strength measurements up to 91 days. In all tests, fly ash (FA) and limestone powder (LS) were used as a comparison. The reactivities determined in the R3 test could be explained by examining the chemical, mineralogical and physical properties of the BPs. Based on their reactivity in the R3 test, the BPs could be classified as pozzolanic, less reactive SCMs, with BPN showing the highest reactivity among the BPs. The results of the compressive strengths and the heat flow calorimetry confirm the reactivities determined in the R3 test. Based on the obtained results, BPN shows the highest potential for application as an SCM.

Influences of Accelerators on Compressive Strength Development of Composite Cements

AbstractLow‐clinker composite cements often have the disadvantage of lower early compressive strength. Hardening accelerators can increase the early compressive strength of Portland cement at the expense of reduced late strength. The extent to which different hardening accelerators influence the compressive strength development of low‐clinker composite cements containing granulated blast furnace slag and limestone was systematically investigated using compressive strength test, ultrasound transmission experiments and heat flow calorimetry.The results show that the accelerator must always be adapted to the particular composite cement in order to increase the early compressive strength. Synergetic effects of cement constituents besides clinker can partly compensate for the reduced late strength of accelerated systems.

Effect of Solvent Composition on Calcium–Silicon Ratio, Particle Size, and Morphology of C─ S─ H Nanomaterials and Cement Properties

Synthesized nanocalcium-silicate-hydrate (C─ S─ H) was successfully employed as an accelerator in portland cement. C─ S─ H nanomaterials were produced in this study utilizing a process that used separate nucleation and growth steps with varied solvent compositions. The effects of the water/alcohol volume ratio (W/A) in the combined solvent on the calcium silicon ratio, particle size, morphology of C─ S─ H nanomaterials, and compressive strength of portland cement were studied. The results reveal that when the W/A ratio decreased, the calcium to silicon (Ca/Si) molar ratio reduced, and the morphology of the C─ S─ H nanomaterials turned from micalike to mixed lamellar and granular, then to granular with a wrinkled surface, and finally to foillike. When the W/A was 3∶1, the small particles (100 nm) of C─ S─ H nanomaterials had the highest W/A, whereas the large particles (>200 nm) had the highest W/A. C─ S─ H nanomaterials offered calcium silicate hydrate nucleation sites, altered C─ S─ H gel development modes, and enhanced the number of hydration products. The composition, particle size, and shape of C─ S─ H nanomaterials all influenced the compressive strength of the cement paste.

The Effect of Calcium Carbonate (CaCO3) and Polystyrene (PS) Composition on Contact Angle and Compressive Strength of Hydrophobic Cement Mortar

In the building there are several elements such as pillars, floors and walls. The wall is the outermost part of the building that directly receives changes in weather such as rain. As a result, the walls of the building are easily fragile and make the walls damaged. To reduce damage, it is necessary to test cement that is resistant to water (hydrophobic) so that the walls of the building are not easily damaged by water and durable with the help of hydrophobic agent additives in the form of CaCO3 and polystyrene. The purpose of this study was to investigate the effect of variations in the composition of CaCO3/polystyrene on the contact angle of the hydrophobic layer and the compressive strength of portland cement. Precursors were made by varying the composition of CaCO3 1%, 2%, 3% and polystyrene/tetrahydrofuran 1:0,065; 2:0,065; 3;0,065 and the calcination temperature used was 60°C using an oven. The optimum contact angle measurement results were obtained at the composition variation of CaCO3 3% and Polystyrene 3:0.065, which was 114.986° and the highest compressive strength value was at variations in the composition of CaCO3 1% and Polystyrene 3:0,065, which was 238.10 kg/cm2.

The Effects of Portland and Sulphoaluminate Cements Solidification/Stabilization on Semi-Dynamic Leaching of Heavy Metal from Contaminated Sediment

Cement-based solidification/stabilization technology is widely applied in the treatment of heavy metals in river sediment because it is an effective treatment, with the advantages of saving time and being economically and environmentally friendly. In this study, the heavy metal polluted sediment in Shanghai Fuxing Island Canal was used as the raw material, the cement solidified form was prepared by adding 10% Portland cement or sulphoaluminate cement, and semi-dynamic leaching tests were carried out on the solidified forms. In this study, we compare two types of cements as metal conditioners and curing agents aiming to determine the more economical and effective way to utilize river sediments. The results showed that the compressive strength of Portland cement solidified form (PSF) increased with an increase in curing time, which could reach 0.75 MPa after 28 days and met the requirements of general subgrade engineering. The compressive strength of sulphoaluminate cement solidified form (SSF) reached 0.35 MPa after curing for 1 day, however, it decreased later. The semi-dynamic leaching test results showed that the mobility of Cu and Cd in the cement solidified form was low, and the migration mechanism of heavy metals was mainly diffusion. The mobility of heavy metals in the PSF was lower than in the SSF, thus, the PSF had a better solidification effect and was more suitable for treating heavy metal-contaminated sediment.

Hydration and compressive strength of Portland cement blended with kamafugites and carbonatites: Effect of Physical Properties

Kamafugites and carbonatitic tuffs, though not common natural pozzolans, are the main option for supplementary cementitious materials in regions surrounding the Western part of the East African Rift valley system. The tuffs are silica undersaturated, carbonatitic and largely ultrapotassic. The current study sought to characterise their physical and chemical properties and compare them with those of published works on natural pozzolans. Two samples, a carbonatite and a kamafugite, from the Toro-Ankole geological region of East Africa are investigated for their effect on specific properties of pastes and mortars when used as natural pozzolans in Portland cement. The volcanic tuffs milled to three fineness levels and blended with Portland cement at 0%, 5%, 10%, 20% and 35% replacement levels are tested for effects on hydration and compressive strength. Results show a time dependent variation in heat of hydration which increases for the first 14 hours before decreasing. The variation seems dependent on level of replacement. Compressive strength results show dependence on level of replacement and fineness which was pronounced until 90 days, peaking at 28 days. Increase in replacement level resulted in a general reduction in compressive strength. A compressive strength conversion process that peaks at 10% replacement level is observed in all blended samples leading to compressive strength results at 180 days being lower than those at 90 days of curing. Compressive strength test results, however, sustain the ASTM C618 and BS 3892 minimum requirement for pozzolanic Portland cements indicating that the carbonatites and kamafugites can be gainfully applied in cement production from the resource and energy economy perspectives.

Investigation on the utilization of coal gasification slag in Portland cement: Reaction kinetics and microstructure

Gasification slag is a solid waste generated by the coal chemical industry which has emerged in recent years. In this paper, the effect of coal gasification slag (CGS) powder content on the reaction kinetics, gel structure and the compressive strength of Portland cement was investigated for the potential application of CGS powders in cementitious materials. The reaction and gel structure of Portland cement blended with CGS was analyzed by using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy tests. The results show that the unreacted CGS power exists mainly in an agglomerated state in cement matrix, and a low dosage of CGS powder (10%) can play a role in nucleation and pozzolanic effect in Portland cement, which is conducive to the formation of hydration reactions of Portland cement, shortening the setting time and improving the compressive strength. If the CGS content is >30%, the hydration product content decreases, and the microstructure of the sample becomes loosened. The setting times are significantly prolonged with the increase of CGS content dosing and the compressive strength is considerably reduced as well.

Pomza ve Diatomitin Portland Çimentosunun Basınç Dayanımına Etkilerinin ANFIS ile Tahmini

Bu çalışmada, çimento harçlarının basınç dayanımını tahmin etmek için uyarlamalı ağ tabanlı bulanık çıkarım sistemi (ANFIS) kullanılarak bir tahmin modeli geliştirilmiştir. Bu amaçla yapılacak olan çalışmada, Portland çimentosu (PÇ) ile içerisine pomza (%10-20), diatomit (%10-20) ve pomza + diatomit (%5+5-%10+10) ikame edilmiş olan toplam yedi farklı çimento ile elde edilen harçlarının 2, 7, 28, 90. hidratasyon günlerindeki basınç dayanımları standart çimento deneyleriyle belirlenmiştir. Deneyler sonucu elde edilen 168 veri eğitim için, bu deney sonuçlarının ortalamaları olan 28 veri de test için kullanılmıştır. ANFIS modelinde eğitim ve test aşamalarında hidratasyon günü, Portland çimento, pomza, diatomit ve su olarak 5 giriş parametresi ve çimento harçalarının basınç dayanımı olmak üzere 1 çıkış parametresi kullanılmıştır. Deneylerden elde edilen ve modelden elde edilen sonuçlarının kıyaslanmasında R2, MAPE ve RMSE olmak üzere üç farklı istatiksel yöntem kullanılmıştır. Elde edilen veriler, deney sonuçları ile ANFIS sonuçları arasında uyumun iyi olduğunu ve inşaat mühendisliğindeki uygulamalarda başarıyla uygulanabilirliğini göstermiştir.

Influence of Lauric acid on mechanical properties of Portland cement

In this research we focused on use of lauric acid as an admixture in cement. The main aim of this research is to scrutinize the outcomes of LA on different properties of cement i.e. normal consistency, setting time, compressive strength and the capillary absorption. As large amount of energy has been consumed during the grinding process of clinker therefore many researchers and investigators used fatty acids as a grinding aid to reduce this energy consumption. Herein, effect of LA as an admixture has been reported. Different proportion of LA i.e. 0.25%, 0.50%, 0.75%, 1.0%, 1.25%, 1.5%, 1.75%, 2.0% of dry weight of cement has been used as an admixture to know the properties of Portland cement. To test the compressive strength of Portland cement, total of 96 cubical specimens were prepared and tested for compression strength in UTM under curing stage of three, seven and twenty-eight days. Examined results showed that LA when used in appropriate amount extends the initial and final setting time of ordinary Portland cement. We noticed the decreasement in capillary absorption as amount of LA escalates. We have accomplished in upgrading the mechanical performance of cement, including the capillary absorption, the compressive strength and reducing the amount of mixing water used while modifying the setting time according to use requirements.

Optimizing the content of nano-SiO2, nano-TiO2 and nano-CaCO3 in Portland cement paste by response surface methodology

Nano materials have become an important means of modifying cement-based materials. The excessive content of nano materials often causes some problems. Therefore, optimizing the content of nano materials in Portland cement paste appear to be particularly important. This paper mainly studies the effects of nano-SiO2 (NS), nano-TiO2 (NT) and nano-CaCO3 (NC) on the early hydration and mechanical properties of Portland cement at small dosages, and optimizes the dosage of the three nano materials by response surface methodology (RSM). The results show that the addition of nano materials can greatly promote the hydration and improve the early compressive strength of Portland cement. When the addition amount is small, the three nano materials have the best effect when added together. Compared with the blank sample, the compressive strength of 1 day, 3 days and 7 days are increased by 52.54%, 53.76% and 61.09%, respectively. In addition, adding NT, NC and NS together to Portland cement can produce more hydration products, increase the rate of hydration, optimize pore structure and reduce the total porosity from 23.2% to 16.8%. Moreover, with three nano materials adding together, the response surface can predict that when the content of NS, NT and NC are 0.86 wt%, 2.75 wt% and 0.14 wt%, respectively, it will have the best hydration promotion effect of Portland cement and it's compressive strength can reach 83 MPa at 7 days.

Investigating mechanical properties and biocement application of CaCO3 precipitated by a newly-isolated Lysinibacillus sp. WH using artificial neural networks

A newly-isolated Lysinibacillus sp. strain WH could precipitate CaCO3 using calcium acetate (Ca(C2H3O2)2), calcium chloride (CaCl2) and calcium nitrate (Ca(NO3)2) via non-ureolytic processes. We developed an algorithm to determine CaCO3 crystal structures by fitting the simulated XRD spectra to the experimental data using the artificial neural networks (ANNs). The biogenic CaCO3 crystals when using CaCl2 and Ca(NO3)2 are trigonal calcites with space group R3c, while those when using Ca(C2H3O2)2 are hexagonal vaterites with space group P6522. Their elastic properties are derived from the Voigt–Reuss–Hill (VRH) approximation. The bulk, Young's, and shear moduli of biogenic calcite are 77.812, 88.197, and 33.645 GPa, respectively, while those of vaterite are 67.082, 68.644, 25.818 GPa, respectively. Their Poisson’s ratios are ~ 0.3–0.33, suggesting the ductility behavior of our crystals. These elastic values are comparable to those found in limestone cement, but are significantly larger than those of Portland cement. Based on the biocement experiment, the maximum increase in the compressive strength of Portland cement (27.4%) was found when Ca(NO3)2 was used. An increased strength of 26.1% was also found when Ca(C2H3O2)2 was used, implying the transformation of less-durable vaterite to higher-durable calcite. CaCO3 produced by strain WH has a potential to strengthen Portland cement-based materials.

Smectite clay waste as an additive for Portland cement

This study aims at investigating the possibility of using smectite clay waste, generated during the oil bleaching process as an additive for Portland cement. The smectite clay waste consists of montmorillonite, quartz, anorthite, calcium sulfate, and amorphous phase. For the regeneration of this waste, the extraction with hexane and thermal method were chosen. The results showed that the extraction of smectite clay waste with hexane significantly increased the pozzolanic activity of this waste; however, the extracted additive prolonged the induction period of Portland cement hydration, slowing down initial cement hydration, and reduced the compressive strength of Portland cement samples.The thermal activation method achieves the best results by calcining smectite clay waste at 600 °C. The calcined additive indicated the strong pozzolanic activity. However, this phenomenon is associated with the formation of the amorphous phase by activating the smectite clay with the sulfuric acid rather than the degradation of the clay minerals during the combustion. The calcined smectite clay waste (CSCW) accelerates the hydration of calcium silicates in the second period of the exothermic reaction. The results of the investigation showed that in samples with the CSCW additive proceed the intense pozzolanic reaction, which can be clearly identified after 28 days of hydration. Up to 15 wt% of the Portland cement can be replaced by the smectite clay waste additive calcined at 600 °C without reducing the compressive strength of Portland cement samples.

Assessing the efficiency level of ground basalt stone and fine sand in compressive strength of portland cement

Compressive strength of a portland cement were effected by natural mineral admixtures (PGKTN) such as basalt stone and fine sand. In general, a higher content of natural mineral admixture, a lower compressive strength of blended portland cement. Influence level depended on such as the kind and content, the fineness of natural mineral admiixture.In this paper, study results on the efficiency level of ground basalt stone and fine sand on the compressive strength in mortar PCB was introduced. Investigation results show that the higher content of ground basalt stone and fine sand in blended portland cements, the lower compressive stregth were investigated. Efficiency level of natural mineral admixture in the compressve strength of blended portland cement is different for mortar and paste cement. Study data show efficiency levels of the chemical and physical effect by the active and inert components in these admixtures on compressve strength of blended portland cement. It confirmed that the efficiency level of these natural mineral admixtures in the compressve strength ís increased with the increasing of the content and grinding of a basalt stone and fine sand.

Synthesis, Structure, and Thermal Stability of Magnesium Oxychloride 5Mg(OH)2∙MgCl2∙8H2O

Today, low-energy and low-carbon footprint alternatives to Portland cement are searched because of huge CO2 emissions coming from Portland clinker calcination. Because of some superior properties of magnesium oxychloride cement (MOC) and the lower carbon footprint of its production, MOC became an intensively studied material with high application potential for the design and development of construction products. In this contribution, magnesium oxychloride with stoichiometry 5Mg(OH)2∙MgCl2∙8H2O (Phase 5) was prepared and characterized. The kinetics of formation and the phase composition of the material were determined using X-ray diffraction and consequent Rietveld analysis. The morphology was studied by scanning electron microscopy, and the chemical composition was determined by both energy-dispersive spectroscopy and X-ray fluorescence. Moreover, the simultaneous thermal analysis in combination with mass spectroscopy and Fourier-transform infrared spectroscopy was employed to study the thermal stability. Using mass spectroscopy, we were able to clarify the mechanism of water and hydrochloric acid release, which was not previously reported. The observed structural and chemical changes induced by exposure of studied samples to elevated temperatures were linked with the measured residual macro and micro parameters, such as bulk density, specific density, porosity, water absorption, compressive strength, and pore size distribution. The Phase 5 revealed a needle-like crystalline morphology which formed rapidly and was almost completed after 96 h, resulting in relatively high material strength. The four-day compressive strength of magnesium oxychloride cement was similar to the 28-day compressive strength of Portland cement. The thermal stability of Phase 5 was low as the observed disruptive thermal processes were completed at temperatures lower than 470 °C.

Evaluation of factors influencing the compressive strength of Portland cement statistically

One of the most effective parameters that influence the performance of concrete is the compressive strength of cement. The chemical composition and the physical properties of Portland cement (PC) can be greatly affected the compressive strength of it. So the aim of this study is to make a statistical analysis for the effect of many factors on (3, 7, 28, and 60 day) compressive strength test results. The factors investigated include the main four compounds of cement (C2S, C3S, C3A and C4AF) in addition to (CaO, MgO, SO3, loss on ignition (LOI), insoluble residue (IR) lime saturation factor (LSF), silica modulus (SM) and alumina ratio (AR)). Furthermore fineness, unsoundness and setting time of cement were also studied. To attain the aim of the present work a statistical program “Statistica” was used for the analysis. It was found that (C3S, C3A and C4AF) compounds has a good correlation with compressive strength, while (C2S, CaO, MgO and SO3) has a negative effect especially at age of 3 days, considering that (C2S and SO3) effect became positive at 7 day age onward. The effect of (LSF and fineness) was positive on compressive strength and the effect of (LOI, IR, SM, AR, unsoundness, fineness, IST, FST) was negative.

Experimental Study on the Mechanical Performance of Grouted Specimen with Composite Ultrafine Cement Grouts

An experimental investigation was conducted in order to understand properties of grouts and grouted specimens. Three different cement types, i.e., composite ultrafine cement (CUC) that was independently developed, ultrafine cement (UC), and Portland cement (PC) were injected into broken red sandstone specimens on the basis of a self-designed grouting test equipment. After the grouting test, the effects on the mechanical behavior of grouted specimens were studied using an uniaxial compression test, macroscopic failure analysis and mesostructure analysis, as well as a comparison of the mechanical and structural properties of three types of grouted specimens was presented. The test results show that the compressive strength of grouted specimens improved in comparison to the rock residual strength, and the compressive strength of PC, UC and CUC grouted specimens increased by 23.0%, 59.6% and 101.5%, respectively. The failure modes of all grouted specimens were brittle failure, but only the CUC grouted specimen was failed along the new failure surfaces, indicating that CUC grouts can better bond the original cracks. The mesostructure characteristics obtained through the Digital 3D Video Microscope reveal the superior filling effect of the CUC grouts as well as verifying the macroscopic mechanical behavior.

Calcium sulphoaluminate cement used as mineral accelerator to improve the property of Portland cement at sub-zero temperature

To avoid the harmful effect of inorganic salt antifreeze admixture on concrete in winter construction, high early strength calcium sulphoaluminite cement (CSA) used as the mineral accelerator was added in Portland cement (PC). The effects of CSA content and pre-curing time on the compressive strength, setting time, freezing point and frozen water, hydration heat, hydration products, and pore structures and microstructure were investigated. The results showed that the compressive strength of PC at sub-zero temperature was enhanced about 300% by the addition of CSA at appropriate dosage and pre-curing time (5 wt % CSA with 2 h pre-curing and 20 wt % without pre-curing). The freezing point and the amount of frozen water of paste were decreased by the addition of CSA and pre-curing. In addition, the hydration process, hydration products, and the microstructures were significantly affected by the amount of CSA and pre-curing time.

Effect of Black Liquor from Date Palm on the Workability and Compressive Strength of Portland Cement and Concrete

AbstractLignin is the second most abundant natural polymer. Due to the high content of carbon and hydrogen (C-H, C-C, C=O), it can be used as a potential dispersant for cement matrix. The objective of this study is to extract lignin from date palm and study its effect in the form of black liquor (BL) on the rheological and physic-mechanical properties of the cements and concrete. The lignin in black liquor form represents approximately 30 wt% dry weight of date palm. It is a heteropolymer composed primarily of methoxylated phenylpropylene alcohol monomeric units interconnected by a variety of stable carbon-carbon and carbon-oxygen-carbon (ether and esters) linkages. The results found show the positive effect on the workability of cement and concrete and confirms its dispersion effect by improving compressive strength of concrete during the early and the later ages of hydration.

Effect of different water-to-powder ratios on the dimensional stability and compressive strength of mineral aggregate-based cements.

The aim of this study was to evaluate the effect of different water-to-powder ratios on the dimensional stability and compressive strength of Portland cement and Mineral Trioxide Aggregate (MTA). Five different volumes of distilled water (0.26; 0.28; 0.30; 0.33 and 0.35 mL) were used for every 1 g of the cements. Twelve samples (12 mm long x 6 mm in diameter) were prepared in Teflon molds. After measuring the initial length, the specimens were stored in distilled water for 24 hours or 30 days. At the end of these time intervals, the specimens were measured again, and the dimensional change was calculated. The same samples used in the previous test were submitted to compression in a universal test machine (1 mm/min-1). Analysis of the dimensional stability results showed no statistical difference between the cements, proportions and time intervals tested, or between their interactions. After 24 hours, MTA was more resistant than Portland cement (p<0.05). At 30 day-period, both cements had similar, and significantly higher resistance than they did at 24 hours (p<0.05). The powder/water ratio had no influence on the dimensional stability of cements. Compressive strength of Portland cement was affected at the proportions of 0.30 and 0.35 mL/g.

Soundness and compressive strength of Portland cement blended with ground granulated ferronickel slag

This paper evaluates the fresh and hardened properties of cement pastes and mortars blended with a ground granulated high-magnesium ferronickel slag (FNS). The main elements of the slag are Silicon (Si), Magnesium (Mg) and Iron (Fe). Test results show that water demand and setting times were not significantly changed by use of the FNS as cement replacement up to 50%. Le-Chatelier soundness test, autoclave expansion test and accelerated curing at 80°C for 120days showed no increase of expansion by up to 65% FNS despite its high magnesium content. This is because the Mg was found to be in the form of stable forsterite ferroan that did not take part in the hydration and expansive Mg(OH)2 (Brucite) was not found in the scanning electron microscope (SEM) images of the microstructure and powder X-ray diffraction (XRD). The 28-day strength activity index of the FNS was 84%. The 90-day mortar compressive strengths were 93% and 68% of the control specimen for 20% and 50% FNS respectively. Thus the soundness and strength development of the ground FNS were found comparable to those of other commonly used supplementary cementitious materials such as class F fly ash.