High Early Strength Portland Cement Research Articles

Applying the Porosity-to-Cement Index for Estimating the Mechanical Strength, Durability, and Microstructure of Artificially Cemented Soil

Fine, expansive, and problematic soils cannot be used in fills or paving layers. Through additions to these soils, they can be converted into technically usable materials in civil construction. One methodology to make them viable for construction is through a stabilization process. Nevertheless, current methodologies regarding dosage based on compaction effort and the volumetric amount of binder used are unclear. Thus, this research describes cement-stabilized sedimentary silt's strength and durability properties from Curitiba (Brazil) for future application in paving. Splitting tensile strength, unconfined compressive strength, and loss of mass against wetting and drying cycles (W-D) were investigated in the laboratory utilizing greenish-gray silt (originating from one of the Guabirotuba Formation layers, Paraná) and high-early strength Portland cement- ARI (CPV). Utilized were cement concentrations (C) of 3, 5, 7, and 9%, molding dry unit weights (d) of 14, 15, and 16 kN/m3, curing periods (t) of 7, 14, and 28 days, and constant moisture content (w) of 23%. With an increase in cement concentration and curing time, the compacted mixes demonstrate an increase in strength, an improvement in microstructure, and a decrease in accumulated mass loss (ALM) and initial porosity (η). Using the porosity/volumetric cement content ratio (η/Civ), the lowest amount of cement required to stabilize the soil in terms of strength and durability was determined. The porosity/cement index provided an appropriate parameter for modeling the mechanical and durability properties, and a unique equation between the strength/accumulated loss of mass and the porosity/binder index was obtained for the curing times studied. Lastly, C = 5% by weight is the minimum acceptable amount for prospective subbase soil application. Doi: 10.28991/CEJ-2023-09-05-02 Full Text: PDF

Ultra-light foamed concrete with recycled sand

Carbon neutralization and upcycling of recycled resources in concrete and construction industry are key themes of sustainability. In this study, ultra-light foamed concrete (ULFC) was fabricated using high early strength Portland cement, silica fume, fly ash, and recycled fine aggregates. ULFC with dry density as low as 284 kg/m3 was fabricated by chemical foaming method using hydrogen peroxide (H2O2) as the foaming agent and hydroxypropyl methyl cellulose ether (HPMC) as the foam stabilizer. Thermal conductivity of the ULFC was 0.092 W/mK. The potential application of the ULFC fabricated in this study is the inorganic insulating material with low density, low thermal conductivity, and good fire resistance for fabric reinforced cementitious matrix (FRCM) building sandwich panels.

The use of rice husk particles to adjust the rheological properties of 3D printable cementitious composites through water sorption

This work presents an experimental investigation on the use of rice husk fine particles to produce 3D printable cementitious composites. Rice husk was chosen as a potential component for printable composites due to its high-water sorption capacity and its high amount of embodied biogenic carbon. These key features were used to adjust the fresh-state properties of the composites, required for the printing process, while decreasing its environmental impact. In this study, a high-early strength Portland cement was used, and the rice husk content varied from 5 to 15 %, in mass of solids. The hydration kinetics was studied using isothermal calorimetry while the rheology of the composites was evaluated using a viscosimeter equipped with a Vane spindle. The rheological parameters were used to assess the buildability and printability of the concrete mixtures. Results demonstrated that rice husk delays the hydration, but this effect can be mitigated through alkaline treatment of the particles. The rheological tests showed that the water sorption by the particles plays an important role on the fresh properties of the composites. The use of rice husk increased the initial yield stress from 176.5 Pa to 2251.9 Pa, and the structuration rate from 6.03 Pa/min to 23.4 Pa/min, when 15 % of particles were used. Finally, rice husk particles increased the maximum object height and reduced the maximum time between layers, which proved the feasibility of using high water sorption biomass particles to produce 3D printable cementitious composites.

Re-liquefaction resistance of lightly cemented sands

The re-liquefaction resistance of cemented sands under multiple liquefaction events such as pre-shock, main-shock, and after-shock earthquakes is a complex phenomenon because the response may alter due to bond breakage. A series of multistage liquefaction–re-consolidation soil element tests under undrained stress-controlled cyclic loading condition using cyclic triaxial were carried out to assess the liquefaction and re-liquefaction resistance of cemented sands with varying degrees of cementation. Lightly cemented specimens were reconstituted using Sydney sand and high early strength Portland cement with cement content ranging from 0.25% to 1% and unconfined compression strength from 15 to 80 kPa. The results showed that the re-liquefaction resistance of cemented sands with different amounts of cement decreased after the first liquefaction event and then increased for succeeding liquefaction events. While the trend of residual excess pore water pressure ratio and cyclic stiffness degradation index of untreated sand under successive liquefaction events remained consistent, the corresponding responses for cemented sands altered for the second to the fifth liquefaction events. In fact, the residual excess pore water pressure ratio and cyclic stiffness of cemented sand increased and degraded faster during the early cycles of loading for the second to fifth liquefaction events.

The “Skin Effect” Assessment of Chloride Ingress into Concrete Based on the Identification of Effective and Apparent Diffusivity

The method of assessment of the “skin effect” for chloride ingress into concrete has been proposed, based on the inverse problem for the identification of at-surface variability of chloride diffusivity under fully saturated conditions. For this purpose, experimental results of 180-day diffusion tests of five types of concrete were used, which allowed the calculation of their chloride apparent diffusivity (taking into account the chloride binding by the cement matrix) and effective diffusivity (relating to the transport of free chloride ions in the pore liquid). The tested concrete samples with a water to cement ratio of 0.5 differed only in the type of cement (high early strength Portland, low-alkali normal early strength Portland, ash Portland, blast furnace, and pozzolanic). In order to effectively describe the chloride binding isotherm, a first-degree non-uniform spline function was used. Finally, the “skin effect” depth at the untreated outer surface of the concrete samples was estimated up to about 5 mm when analyzing space variability of apparent chloride diffusivity for four types of concrete with low-alkali normal early strength Portland, ash Portland, blast furnace, and pozzolanic cement. In this respect, the “skin effect” on the concrete with high early strength Portland cement was not detected.

Multiple techniques of microstructural characterization of DEF: Case of study with high early strength Portland cement composites

Multiple physicochemical and microstructural techniques were successfully conducted to characterize materials and cement composites induced to delayed ettringite formation (DEF). Backscattered electron diffraction, with elemental analysis by energy dispersive spectroscopy in a scanning electron microscope, showed a natural sand with strained quartz and other minor minerals. DEF was observed in distinctive behaviors for mortars and concretes regarding expansion, being quasi-linear and sigmoidal, respectively. Concrete specimens registered high expansions at 450 days (about 0.40%). The resulting effects between composites were distinctive for microstructural and mechanic evolution, especially the modulus of elasticity, with a decrease of 51%, on average.

STUDY ON POROUS CONCRETE USING ORDINARY PORTLAND CEMENT FOR EARLY TRAFFIC OPENING

In Japan, the use of concrete pavements gradually decreased since the 1960s owing to the fact that they require some days to cure. However, recent research revealed that concrete pavements are effective for the Life Cycle Cost and the heat island phenomenon. A novel method of making concrete pavements, with which the traffic can be opened after only one-day curing, has been proposed in Japan. Furthermore, authors have developed porous concrete for road pavement, which can also cure in one day. This study proposes a new design method to reduce the production cost of porous concrete. To achieve this, the high early-strength Portland cement was replaced with ordinary Portland cement and coarse aggregate of various sizes with a single-sized coarse aggregate. Various tests revealed that the concrete prepared by the proposed design method satisfies the standard values of the bending strength and the permeability coefficient for concrete pavement for early traffic opening. Therefore, it is considered that the design method proposed herein is vital in reducing the cost of porous concrete pavements.

Parâmetros de resistência e de durabilidade de um silte sedimentar cimentado para aplicação em pavimentação

Este artigo apresenta os parâmetros de resistência e de durabilidade de um silte sedimentar de Curitiba (Brasil) estabilizado com cimento para potencial uso em pavimentação. A resistência à tração por compressão diametral, a resistência à compressão simples e perda de massa devido a ciclos de molhagem e secagem (M/S) foram pesquisados em laboratório usando um silte de coloração cinza esverdeado (originário de um dos horizontes da Formação Guabirotuba - Paraná) e cimento de alta resistência inicial-ARI (CPV). Foram empregados teores de cimento (C) de 3, 5, 7 e 9%, pesos específicos secos de moldagem (γd) de 14, 15 e 16 kN/m3, tempos de cura (t) de 7, 14 e 28 dias, e um teor de umidade (ω) fixo de 23%. Os resultados demonstram que com o aumento do teor de cimento e do tempo de cura, há um ganho de resistência mecânica, melhoramento na microestrutura, e uma diminuição na perda acumulada de massa (PAM) e da porosidade inicial (η) das misturas compactadas. Empregou-se a relação porosidade/teor volumétrico de cimento (η/Civ) para determinar a quantidade de cimento mínima necessária para estabilizar o solo de acordo com os parâmetros de resistência e durabilidade. Finalmente, C=5%, em peso, é o teor mínimo que satisfaz os requerimentos para uso potencial do solo em sub-base.

Difference in Strength Development between Cement-Treated Sand and Mortar with Various Cement Types and Curing Temperatures.

To improve the strength of cement-treated sand effectively, the use of various cement types was investigated at different curing temperatures and compared with the results obtained from similar mortars at higher cement contents. The compressive strengths of cement-treated sand specimens that contained high early-strength Portland cement (HPC) cured at elevated and normal temperatures were found to be higher than those of specimens that contained ordinary Portland cement (OPC) and moderate heat Portland cement at both early and later ages. At 3 days, the compressive strength of the HPC-treated sand specimen, normalized with respect to that of the OPC under normal conditions, is nearly twice the corresponding value for the HPC mortar specimens with water-to-cement ratio of 50%. At 28 days, the normalized value for HPC-treated sand is approximately 1.5 times higher than that of mortar, with a value of 50%. This indicates that the use of HPC contributed more to the strength development of the cement-treated sand than to that of the mortar, and the effects of HPC at an early age were higher than those at a later age. These trends were explained by the larger quantity of chemically bound water observed in the specimens that contained HPC, as a result of their greater alite contents and porosities, in cement-treated sand. The findings of this study can be used to ensure the desired strength development of cement-treated soils by considering both the curing temperature and cement type. Furthermore, they suggested a novel method for producing a high internal temperature for promoting the strength development of cement-treated soils.

Freezing and Thawing Durability of High Early Strength Portland Cement Concrete

AbstractHigh early strength (HES) portland cement concrete (PCC) is widely used in pavement preservation because it permits a quick reopening to traffic. However, these repairs often deteriorate fa...

Internal Curing to Mitigate Cracking in Rapid Set Repair Media

Abstract Rapid hydration and high early strength portland cement and calcium sulfoaluminate (CSA) concretes are commonly used as pavement repair media. Field trials reveal a tendency to crack along the longitudinal axis of the repair. The authors hypothesized that internal curing with saturated lightweight aggregate would prevent or delay restrained shrinkage cracking in the rapid repair media. The fresh properties (slump, setting time), mechanical properties (elastic modulus, compressive and tensile strength), and volume stability (autogenous shrinkage, drying shrinkage, restrained ring shrinkage, creep) of the rapid repair media were evaluated with and without internal curing with saturated lightweight aggregate. Despite delayed hydration and reduced early-age strength, internally cured concretes could retain the requisite minimum 4-hour compressive strength of 4,000 psi. Significant improvements in volume stability were also noted. Drying and autogenous shrinkage were reduced by factors up to 20 % and 50 %. However, detrimentally, creep shrinkage was increased by factors up to 45 %, respectively. The time to cracking in restrained ring shrinkage tests was increased by factors up to 60 %. These results indicate that internal curing can successfully improve volume stability and mitigate restrained shrinkage cracking in rapid repair media without compromising fresh properties or ultimate mechanical strength.

Reuse of iron ore tailings from tailings dams as pigment for sustainable paints

In order to minimise the environmental, social and economic impacts caused by the mining activity, this work proposes the use of iron ore tailings from tailings dams (IOT) as pigment in the production of a paint for buildings – the Sustainable Paint. The waste originates from the mining activity in the state of Minas Gerais. For this work, it was used in its raw state, subjected only to drying and lump breaking. In addition to IOT and water, four types of binders were tested: polyvinyl acetate (PVA) resin (in the form of ordinary white glue), acrylic resin, hydrated lime for painting and high early strength Portland cement. Binder contents ranged from 0% to 50% over the mass of IOT. For the evaluation of the mixtures, four main parameters were used: cost, colour homogeneity, abrasion resistance, and durability to external exposure, using the colour difference methodology ΔE (Delta-E). The results of binder evaluations were compared among themselves and with conventional paints from a brand recognised by the Brazilian Association of Paint Manufacturers. The Sustainable Paint presented reddish colour; suitable opacity; satisfactory results regarding durability at a significantly lower cost. In general, the blends with IOT, especially those using PVA as binder, have proved to be promising alternatives for paintings prepared in situ. It is noticeable the wide potential of use of this pigment by communities affected by iron ore tailings dams throughout Brazil and worldwide.

Strength development of cement-treated sand using different cement types cured at different temperatures

This study aimed to investigate the strength development of cement-treated sand using different cement types: ordinary Portland cement (OPC), high early strength Portland cement (HPC), and moderate heat Portland cement (MPC) cured at different temperatures. The cementtreated sand specimens were prepared with 8% of cement content and cured under sealed conditions at 20οC and 40οC, and mortar specimens were also prepared for reference. The results showed that the compressive strength of cement-treated sand increased in order of MPC, OPC, and HPC under high curing temperatures. It was interesting that the compressive strength of the specimens using HPC was much larger than that of the specimen using OPC and MPC under 20οC due to the larger amount of chemically bound water. Additionally, it was revealed that under high curing temperatures, the pozzolanic reaction was accelerated in the cement-treated sand; this may be caused by the high proportions of sand in the mixtures.

高炉スラグ細骨材を用いたコンクリートの凍結融解作用後の水中疲労に関する研究

Many concrete deck slabs of bridges have been deteriorated by heavy traffic, and freezing and thawing action. The water through the broken waterproof layer promotes the deterioration of concrete much more. Concrete used in replacements should have high resistance against freezing and thawing attack and fatigue in water. In this study, it is shown that the resistance to freeze and thaw attack can be improved by granulated blast furnace slag sand even without AE agent. The resistance to freeze and thaw attack of non-AE concrete with granulated blast furnace slag is almost same as that of AE concrete with the ordinary crushed sand. The fatigue of concrete suffered from freeze and thaw attack depends on the type of binder. When the crushed sand is used, the fatigue of concrete with high early strength Portland cement suffered from freeze and thaw attack is lower than that with ordinary Portland cement. When blast furnace slag sand is used, the tendency is almost same as when crushed sand is used. However, when blast furnace slag sand is used, the fatigue of concrete suffered from freeze and thaw attack can be improved with water curing period. It is also shown in this paper that blast furnace slag sand reacts with water and improve the durability of concrete.

Performance of rapid-repair concrete in an aggressive marine environment

Rapid-repair concretes are currently used to repair structures such as bridge decks, substructure elements on bridges (e.g. piers and columns), pavements, and components of buildings. Rapid-repair concretes must not only achieve a high-early strength in a short period of time (e.g. 20MPa in 3h) but must also survive for the remaining life of the structure. One way of achieving high early-age strength is the use of ettringite-based cements; in these cements early strength is attributed to the rapid formation of ettringite by incorporating, in the binder, calcium sulfo-aluminate cement or a combination of calcium aluminate cement and calcium sulfate. Although research has proven that early-strength is achievable, there exist limited published durability data for these systems. This paper presents data on the performance of a number of rapid-repair materials placed at the high-tide level of a marine exposure site (Treat Island, Maine, USA) which experiences approximately 100 freeze-thaw cycles a year making it one of the harshest environments for concrete in the world. A number of concretes were studied including an ordinary Portland cement (PC) and a high-early strength Portland cement (HEPC) as references, PC accelerated by calcium aluminate cement (CAC) with calcium sulfate (C$), PC accelerated by calcium sulfo-aluminate (C$A(2)-PC), and calcium sulfo-aluminate belite (C$A(1)-C2S) cement on its own. Reinforced concrete specimens were monitored on a yearly basis to evaluate the corrosion condition of the steel. After three years of exposure, reinforced concrete beams from each mix were returned to the laboratory to determine chloride profiles, and to conduct X-ray diffraction (XRD) and microstructural investigation using scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDS) analysis.

고로슬래그와 알칼리 활성화제를 이용한 모래 고결 및 조기강도에 관한 연구

본 연구에서는 자원 재활용을 위해 시멘트를 전혀 사용하지 않고 잠재 수경성을 지닌 고로슬래그를 이용하여 사질토를 고결시키고자 하였다. 알칼리 활성화제에 의해 경화되는 고로슬래그의 함유량과 알칼리 활성화제의 종류를 달리 하여 이들이 사질토의 조기강도에 미치는 영향에 대하여 연구하였다. 고로슬래그의 함유량을 사질토의 4, 8, 12, 16%로 하고 여섯 종류(두 종류의 천연재료, 네 종류의 화학약품)의 알칼리 활성화제를 사용하여 공시체를 제작하였다. 제작한 공시체는 3일 또는 7일 동안 대기중 양생한 다음 일축압축강도시험을 실시하였다. 알칼리 활성화제 종류에 따른 일축압축강도는 탄산칼륨, 수산화칼슘, 수산화나트륨, 수산화칼륨 순으로 높게 측정되었으며, 동일한 성분을 가진 천연재료보다 화학약품을 사용한 공시체의 일축압축강도가 높게 나타났다. 3일 양생한 공시체 중 최대 일축압축 강도가 발현된 것은 16%의 고로슬래그에 수산화칼륨을 사용한 경우로 3MPa 정도의 강도가 측정되었으며, 이는 초속 경시멘트 16%를 사용한 공시체 강도의 37%에 해당된다. 알칼리 활성화제 종류에 관계없이 고로슬래그 함유량이 증가함에 따라 건조밀도가 증가하면서 일축압축강도도 증가하였으며, 양생기간이 3일에서 7일로 증가함에 따라 최대 97%의 강도 증가가 발생하였다. 고결된 모래의 XRD 분석 결과 C-S-H 화합물이 생성되었으며, SEM 분석 결과에서는 고로슬래그 함유량이 증가할수록 생성되는 수화물도 증가하여 모래 입자를 에워싸는 형태를 보였다. In this study, a blast furnace slag with latent hydraulic property is used to cement granular soils without using Portland cement. When the blast furnace slag reacts with an alkaline activator, it can cement soils. The effect of amounts of blast furnace slag and types of alkaline activator on soil strength was investigated for resource recycling. Four different amounts of slag and six different activators (two naturals and four chemicals) were used for preparing specimens. The specimens were air-cured for 3 or 7 days and then tested for unconfined compressive strength (UCS). The UCS of cemented sand with slag increased, in the order of specimens mixed with potassium carbonate, calcium hydroxide, sodium hydroxide and potassium hydroxide. Chemical alkaline activator was better than natural alkaline activator. The maximum UCS of 3-days cured specimens was 3 MPa for 16% of slag with potassium hydroxide, which corresponded to 37% of one with 16% of high-early strength portland cement. As the amount of slag increased, the UCS and dry density of a specimen increased for all alkaline activator cases. As the curing time increased from 3 days to 7 days, the UCS increased up to 97%. C-S-H hydrates were found in the cemented specimens from XRD analyses. Cement hydrates were more generated with increasing amount of slag and they surrounded sand particles, which resulted in higher density.

Sulfate attack on a white Portland cement with activated slag

The sulfate resistance of a white Portland cement (WPC) containing 0%, 50% or 70% granulated blast-furnace slag as a partial cement replacement was investigated. The use of Na2SO4 as a chemical activator in the 50% slag blend was also studied. The performance of the blended cements was monitored by exposing the prepared mortar specimens to a 5% Na2SO4 solution for 2years according to ASTM C1012/04 and using TG/DTA, DRX and SEM/EDX analyses of the paste samples. The same blends composed a high early strength Portland cement (PC) were also used. The results showed the benefits of slag in both cements, and an increase in its percentage increased sulfate resistance. Chemical activation reduced the expansion compared to those mixtures without it. For long-term exposure, all of the WPC blends showed less expansion than the corresponding blends with PC. A microstructure analysis identified ettringite and gypsum as the main degradation products.

In Situ Time-Resolved X-Ray Diffraction of Tobermorite Formation Process Under Autoclave Condition

Hydrothermal formation reaction of tobermorite has been investigated by in situ X-ray diffraction (XRD) using high-energy X-rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon-counting pixel array detector. XRD measurements were conducted in a temperature range of 100°–190°C throughout 7.5 h of reaction time with a time interval of 4.25 min under a saturated steam pressure. Two samples using different types of cements were compared: high early strength Portland cement and ordinary Portland cement. In both cases, noncrystalline calcium silicate hydrate (C–S–H), hydroxylellestadite (HE), and katoite were clearly observed as intermediate materials. A possible mechanism that the consumption of noncrystalline C–S–H and HE as precursors of tobermorite occurs sequentially rather than simultaneously has been suggested. Four tobermorite peaks corresponding to different reflections started to be detected at the same timing, suggesting tobermorite is formed without any preference for a particular crystal axis at the beginning. A decrease in the Bragg spacing of the basal reflection during the reaction was observed, implying the increase of periodicity along the c-axis.

Avaliação de concreto de cimento Portland contendo resíduos de PET

O objetivo deste trabalho foi verificar a influência da adição de resíduos de poli (tereftalato de etileno) - PET - sobre a resistência mecânica em concreto de cimento Portland. O PET foi utilizado no formato encontrado em indústria de reciclagem de embalagens. Os resíduos foram utilizados como substitutos de parte dos agregados do concreto e, para cada um dos resíduos, foram preparados quatro traços (10%, 20%, 30% e 40%, em volume). Para a preparação dos traços foi utilizado cimento Portland de Alta Resistência Inicial (CPV - ARI) fornecido pela Votoran. A partir de cada uma das misturas obtidas foram confeccionados quinze corpos-de-prova em formato cilíndrico conforme a norma NBR 5738. Foram preparados também corpos-de-prova sem substituição de agregados que serviram como material de referência. Os ensaios de compressão foram realizados de acordo com a norma NBR 5739, nas idades de um, três e sete dias e, em cada uma destas idades, foram testados cinco corpos-de-prova de cada traço. Para todos os traços obtidos e, em todas as idades das amostras ensaiadas, pode-se notar uma tendência de redução da resistência mecânica com o aumento da fração volumétrica de substituição de agregados. O maior valor de resistência à compressão axial com a idade de sete dias foi apresentado pelo traço sem substituição de agregados (15,38 MPa), e o menor valor, para a mesma idade, foi apresentado pelo traço com 40 % de substituição de agregados por resíduos de PET (1,94 MPa).

Evaluation of high-early strength PCC mixtures used in full depth repairs

The research described herein was conducted as a part of NCHRP Project 18-04B, Early Opening-to-Traffic Portland Cement Concrete for Pavement Rehabilitation [Van Dam TJ. Durability of ‘Early-Opening-to-Traffic’ portland cement concrete for pavement rehabilitation. Final Report, NCHRP Web Document 76, Transportation Research Board, National Research Council, Washington, DC; 2005.]. In the study fourteen different high-early strength portland cement concrete (PCC) full-depth repair mixtures (two replicates or batches were prepared for each mixture for a total of 28 batches) were designed for a 6–8 h opening to traffic window. The fresh and hardened concrete properties, freeze-thaw durability and microstructural properties of the concrete were assessed as part of the laboratory testing program. As a result of this assessment it was determined that high-early strength PCC mixtures of adequate strength could be produced, but that interactions between the various constituents could result in durability problems in some mixtures, particularly those made with Type III cement and high-range water reducers. It is recommended that durability-related testing be conducted on such mixtures to ensure longevity of the repair.