scholarly journals Durability and Time-Dependent Properties of Low-Cement Concrete

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3583 ◽  
Author(s):  
Keila Robalo ◽  
Eliana Soldado ◽  
Hugo Costa ◽  
Luís Carvalho ◽  
Ricardo do Carmo ◽  
...  
Keyword(s):  
Concrete Cover ◽  
Time Dependent ◽  
Sustainable Construction ◽  
Cement Concrete ◽  
Carbonation Resistance ◽  
Shrinkage And Creep ◽  
Binder Ratio ◽  
Reference Curves ◽  
Long Lifetime ◽  
Formulation Parameters

The sustainability concerns of concrete construction are focused both on the materials’ eco-efficiency and on the structures’ durability. The present work focuses on the characterization of low cement concrete (LCC), regarding time-dependent and durability properties. LCC studies which explore the influence of the formulation parameters, such as the W/C (water/cement ratio), W/Ceq, (which represents the mass ratio between water and equivalent cement), W/B (water/binder) ratio, and the reference curves, on the aforementioned properties are limited. Thus, several LCC mixtures were formulated considering two dosages of binder powder, 350 and 250 kg/m3, the former with very plastic consistency and the latter with dry consistency, which were combined with a large spectrum of cement replacement rates (up to 70%), through adding fly ash and limestone filler, and with different compactness levels. The main objectives were to study the influence of the formulation parameters on the properties: shrinkage and creep, accelerated carbonation and water absorption, by capillarity, and by immersion. The lifetime of structures produced with the studied LCC was estimated, considering the durability performance, regarding the carbonation effect on the possible corrosion of the steel reinforcement. LCC mixtures with reduced cement dosage and high compactness, despite the high W/C ratios, have low shrinkage and those with higher strength have reduced creep, however depending on W/Ceq ratio. Those mixtures can be formulated and produced presenting good performance regarding carbonation resistance and, consequently, a long lifetime, which is mandatory for a sustainable construction. LCC with 175 kg/m3 of cement dosage is an example with higher lifetime than current concrete with 250 kg/m3 of cement; depending on the XC exposure classes (corrosion induced by carbonation), the amount of cement can be reduced between 37.5% and 42%, since the LCC with 175 kg/m3 of cement allows reducing the concrete cover below the minimum recommended, ensuring simultaneously the required lifetime for current and special structures.

scholarly journals Mechanical Characterisation and Shrinkage of Thermoactivated Recycled Cement Concrete

2021 ◽  
Vol 11 (6) ◽  
pp. 2454
Author(s):  
Sofia Real ◽  
José Alexandre Bogas ◽  
Ana Carriço ◽  
Susana Hu
Keyword(s):  
Mechanical Strength ◽  
Elasticity Modulus ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Cement Concrete ◽  
Supplementary Cementitious Material ◽  
Mechanical Characterisation ◽  
Shrinkage Behaviour ◽  
Binder Ratio

This paper investigates the mechanical and shrinkage behaviour of concrete with recycled cement (RC) thermoactivated from waste cement paste and waste concrete. Overall, compared to ordinary Portland cement (OPC), for the same water/binder ratio, the mechanical strength and ultrasonic pulse velocity were not significantly influenced by the incorporation of RC. The elasticity modulus decreased with the addition of RC and the shrinkage tended to increase at high RC content. The incorporation of up to 15% RC allowed the production of workable concrete with identical shrinkage and similar to higher mechanical strength than concrete with only OPC. RC proved to be a very promising more eco-efficient supplementary cementitious material.

scholarly journals Experimental Study on Durability Improvement of Fly Ash Concrete with Durability Improving Admixture

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Hong-zhu Quan ◽  
Hideo Kasami
Keyword(s):  
Fly Ash ◽  
Experimental Studies ◽  
Drying Shrinkage ◽  
Replacement Ratio ◽  
Fly Ash Concrete ◽  
Air Content ◽  
Carbonation Resistance ◽  
Binder Ratio ◽  
Water Binder Ratio

In order to improve the durability of fly ash concrete, a series of experimental studies are carried out, where durability improving admixture is used to reduce drying shrinkage and improve freezing-thawing resistance. The effects of durability improving admixture, air content, water-binder ratio, and fly ash replacement ratio on the performance of fly ash concrete are discussed in this paper. The results show that by using durability improving admixture in nonair-entraining fly ash concrete, the compressive strength of fly ash concrete can be improved by 10%–20%, and the drying shrinkage is reduced by 60%. Carbonation resistance of concrete is roughly proportional to water-cement ratio regardless of water-binder ratio and fly ash replacement ratio. For the specimens cured in air for 2 weeks, the freezing-thawing resistance is improved. In addition, by making use of durability improving admixture, it is easier to control the air content and make fly ash concrete into nonair-entraining one. The quality of fly ash concrete is thereby optimized.

Investigation and Prediction for Carbonation Resistance of Ready-Mixed Concrete in Qinhuangdao City

2011 ◽  
Vol 71-78 ◽  
pp. 4981-4984
Author(s):  
Xiao Hui Li ◽  
Jin Rui Zhang ◽  
Ran Ran Zhao ◽  
Wei Zheng
Keyword(s):  
Mass Fraction ◽  
Great Influence ◽  
Mineral Admixture ◽  
Carbonation Depth ◽  
Service Period ◽  
Carbonation Resistance ◽  
Binder Ratio ◽  
Water To Binder Ratio ◽  
Ready Mixed Concrete ◽  
Mixed Concrete

The carbonation resistance of ready-mixed concrete in Qinhuangdao was investigated and the predicted experimental data indicated that the carbonation resistance of concrete in Qinhuangdao was unsatisfactory. The longest predicted service period of concretes in this survey is merely 39.1 years when the carbonation depth reaches 25 mm; and the shortest is only 8.7 years. It’s awfully difficult to guarantee the durability of reinforced concrete structures for 50 years. The experiment results also shows that both the water to binder ratio and the mineral admixture mass fraction have great influence on the carbonation resistance of concrete. With the decrease of water to binder ratio and mineral admixture mass fraction, the predicted service years of ready-mixed concrete increase dramatically.

Variation of Carbonation Coefficient of Pumping Concrete with Moist-Curing Time at early Ages and Fly-Ash Content

2011 ◽  
Vol 287-290 ◽  
pp. 899-905
Author(s):  
Qing Ye ◽  
Zhi Wei Song ◽  
Guo Rong Yu
Keyword(s):  
Fly Ash ◽  
Concrete Cover ◽  
Ash Content ◽  
Curing Time ◽  
Accelerated Carbonation ◽  
Carbonation Depth ◽  
Carbonation Resistance

Based on accelerated carbonation test, the variation of carbonation resistance of pumping concrete (C40 grade) with moist-curing time at early ages and fly-ash content was studied. Results indicate that the carbonation coefficient and the accelerated carbonation depth of the concrete increased obviously with a reduction in the moist-curing time at early ages and with an increase in the fly-ash content. For example, in conditions of curing schedules with 28, 7, 3, 2 and 1 d moist-curing at 20 0C with above 95% RH at early ages and then 0, 21, 25, 26 and 27 d air curing at 20 0C with 60% RH, respectively, carbonation coefficients of the concrete incorporated with 30% fly-ash were 2.04, 2.49, 3.16, 3.86 and 5.42 mm/a0.5 respectively, and thus it can be seen that the calculated times when concrete cover (25 mm) was completely carbonated naturally in now atmosphere (0.04% CO2) were 164, 104, 66, 44 and 21 years respectively. The results suggest that for the carbonation resistance of the C40 concrete incorporated with up to 30% fly-ash, the moist-curing time of 7 days at early ages should be necessary.

Proportion Design of Autoclaved Cement Concrete Based on High Strength

2011 ◽  
Vol 391-392 ◽  
pp. 161-164
Author(s):  
Tie Quan Ni ◽  
Chang Jun Ke ◽  
Li Zhang
Keyword(s):  
Coarse Aggregate ◽  
High Strength ◽  
Orthogonal Test ◽  
Mineral Admixture ◽  
Mix Design ◽  
Hydration Reaction ◽  
Cement Concrete ◽  
Binder Ratio ◽  
Four Levels ◽  
Water Binder Ratio

According to the particularity of the autoclaved cement concrete that partial aggregate could participate in hydration reaction in the process of autoclaving, the optimal gradation of coarse aggregate and the optimal slurry aggregate ratio is studied, and the effect of water reducing agent for fluidity of cement paste is also studied. The optimized mix design of autoclaved cement concrete based on high strength (compressive strength and flexural strength) is done by orthogonal test with four factors (water-binder ratio, type of mineral admixture, amount and sand ratio) and four levels.

scholarly journals Experimental Study on Time-Dependent Changes in Rheological Properties and Flow Rate of 3D Concrete Printing Materials

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6278
Author(s):  
Hojae Lee ◽  
Eun-A Seo ◽  
Won-Woo Kim ◽  
Jae-Heum Moon
Keyword(s):  
Rheological Properties ◽  
Flow Rate ◽  
Test Specimen ◽  
Three Dimensional ◽  
Time Dependent ◽  
Flow Properties ◽  
Layer Width ◽  
Binder Ratio ◽  
Water To Binder Ratio ◽  
Over Time

Three-dimensional concrete printing (3DCP) materials require a relatively low water-to-binder ratio (W/B) of 0.3 or less to ensure their buildability and flow properties are sufficiently maintained after mixing. In this study, the rheological properties of 3DCP materials with W/B 0.28 were evaluated up to 60 min after mixing, and the yield stress and plastic viscosity were analyzed over time. A gradual decrease in flow rate with time was observed during the transport of 200 kg of material per batch through a 20 m hose. To examine the time-dependent changes in flow rate and layer volume, a 2200 mm × 1000 mm test specimen was printed. The dependence of the layer width over time during the printing process was measured and analyzed. The experimental analyses showed that the flow rate and layer volume of the 3DCP material gradually decreased with time after mixing, which was correlated with the rheological properties.

scholarly journals STUDI PENDAHULUAN BATAS MAKSIMUM KADAR LUMPUR PADA AGREGAT BETON GEOPOLIMER

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Djedjen Achmad ◽  
Desi Supriyan
Keyword(s):  
Compressive Strength ◽  
Concrete Aggregate ◽  
Fine Aggregate ◽  
Geopolymer Concrete ◽  
Test Results ◽  
Cement Concrete ◽  
Flexural Tensile Strength ◽  
Binder Ratio ◽  
The Impact ◽  
Water Binder Ratio

ABSTRACTHas been researched the impact of mud in aggregate on geopolymer concrete with studies using the cement concrete as a reference. In this study both of concrete are mixed with a variation of mud of 0%, 0.75%, 3% and 5.75% of the combined aggregate weight. Compressive strength of cement concrete is designed with a target of 300 kg / cm2 and geopolymer concrete is made with water binder ratio (w/b) 0.25, Molarity 12 M, the ratio of sodium silicate and sodium hydroxide 1.5. At the age of 3, 7, 14 and 28 day tested of compressive strength, while the spliting test, flexural tensile strength, and modulus of elasticity are tested at 28 days. From the test results, the higher mud content in aggregate , the mechanical properties of the concrete are decreased. Based on testing of compressive strength in cement concrete at 28 days, with a 3% mud content (the content of the reference mud) turns of compressive strength decreased by 77.356%. Of the percentage reduction on the compressive strength of the cement concrete, can be compared to the mud content in geopolymer concrete at 2.04%. Thus the maximum mud on geopolymer concrete aggregate is, for coarse aggregate of 0.68% and a maximum mud content for fine aggregate was 3.4%.Key words : Mud, aggregate, concrete, cement, geopolimer, strengthABSTRAKTelah diteliti dampak kadar lumpur pada agregat untuk beton geopolimer dengan penelitian menggunakan benda uji beton semen sebagai acuan dan beton geopolimer. Dalam penelitian ini ke dua beton tersebut dicampur dengan lumpur gabungan agregat kasar dan agregat halus dengan variasi 0 %, 0.75 %, 3 % dan 5,75 % dari berat agregat gabungan. Beton semen dirancang dengan target kuat tekan 300 kg/cm2 dan beton geopolimer dibuat dengan campuran water binder ratio (w/b) 0.25, Molaritas 12 M, perbandingan sodium silikat dan sodium hidroksida 1.5. Pada umur 3, 7, 14 dan 28 hari dilakukan uji kuat tekan, sedangkan uji kuat tarik belah, uji kuat tarik lentur, dan modulus elastisitas dilakukan pada umur 28 hari. Dari hasil uji terlihat bahwa semakin tinggi kadar lumpur pada agregat, karakteristik mekanis kedua beton tersebut mengalami penurunan. Berdasarkan pengujian kuat tekan pada beton semen umur 28 hari, dengan kadar lumpur 3 % (kadar lumpur referensi) ternyata beton semen mengalami penurunan kuat tekan sebesar 77.356 %. Dari persentase penurunan kuat tekan beton semen tersebut, diplot pada grafik kuat tekan beton geopolimer maka persentase kadar lumpur gabungan yang mengalami penurunan 77.356 % adalah 2.04 %. Dengan demikian kadar lumpur maksimum pada agregat beton geopolimer adalah, untuk agregat kasar sebesar 0.68 % dan kadar lumpur maksimum untuk agregat halus adalah 3.4 %.Kata kunci : Lumpur, agregat, beton, semen, geopolimer, kekuatan

scholarly journals Improving the strength performance of high volume periwinkle shell ash blended cement concrete with sodium nitrate as accelerator

2015 ◽  
Vol 6 (2) ◽  
pp. 18-22 ◽  
Author(s):  
Akaninyene A. Umoh ◽  
Anthony O. Ujene
Keyword(s):  
Tensile Strength ◽  
Sodium Nitrate ◽  
Blended Cement ◽  
High Volume ◽  
Strength Properties ◽  
Splitting Tensile Strength ◽  
Cement Concrete ◽  
Strength Performance ◽  
Binder Ratio ◽  
Periwinkle Shell

 The objective of this study is to examine the effect of accelerator (NaNO3) on the strength properties of High volume Periwinkle shell ash blended cement concrete. A mix ratio and water-binder ratio of 1:2:4 (cement: sand: gravel) and 0.60, respectively was used as the reference. The cement was then replaced with 30% Periwinkle Shell Ash (PSA) by weight of cement. Sodium nitrate in the dosages of 1, 2, and 3% by weight of cement was added to the blended mixture of cement and PSA. The strength properties investigated were compressive and splitting tensile strength tested at 7, 14 and 28 days hydration. The results indicated that the compressive strength and the splitting tensile strength generally increases with curing age, and that sodium nitrate of up to 2% dosage greatly improved the strength performance of high volume PSA blended cement concrete over that of the reference. The study concluded that the inclusion of 2% sodium nitrate by weight of cement in the mixture could be considered the optimum dosage for the improvement of both compressive and splitting tensile strength of concrete incorporating up to 30% PSA content.

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