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Author(s):  
Theodore Gautier Bikoko ◽  
Jean Claude Tchamba ◽  
Valentine Yato Katte ◽  
Divine Kum Deh

To fight against the high cost and the increasing scarcity of cement and at the same time to reduce the CO2 greenhouse gases emission associated with the production of Portland cement, two types of wood ashes as a substitute of cement in the production of concretes were investigated. In this paper, we substituted cement by two types of species of wood ashes namely, avocado and eucalyptus ashes following the proportions ranging from 0% to 30 % on one hand, and on the other hand, we added these two types of species of wood ashes namely, avocado and eucalyptus ashes following the proportions ranging from 0% to 10 % by weight of cement in the concrete samples. After 7, 14 and 28 days of curing, compressive strength tests were conducted on these concrete samples. The findings revealed that using wood ashes as additives/admixtures or as a substitute of cement in the production/manufacturing of concrete decreased the compressive strength of concrete. Hence, it can be said that wood ash has a negative influence on the strength of concrete. At three percent (3%) and ten percent (10%) of addition, the wood ash from eucalyptus specie offers better resistance compared to the wood ash from avocado specie, whereas at five percent (5%) of addition, the wood ash from avocado specie offers better resistance compared to the wood ash from eucalyptus specie. At thirty percent (30%) of substitution, the wood ash from eucalyptus specie offers better resistance compared to the wood ash from avocado specie. The compressive strengths increase with the increase of curing age.


2022 ◽  
Vol 8 ◽  
Author(s):  
Changyong Li ◽  
Haibin Geng ◽  
Siyi Zhou ◽  
Manman Dai ◽  
Baoshan Sun ◽  
...  

Producing concrete with large content of fly ash attracts increasing attention in low carbon building materials. In this paper, the fly-ash concrete (FAC) with a content of fly ash no less than 50% total weight of binders was developed. The adaptability of fly ash used for concrete was firstly examined by testing the water requirement of normal consistency and the setting time for cement fly-ash paste, and the strengths of cement fly-ash mortar at the curing age of 7 and 28 days. The factors of water-to-binder ratio from 0.3 to 0.5, the content of fly-ash from 40% to 80%, and the excitation measures with additional Ca(OH)2 and steam curing at initial were considered. After that, the FAC was designed by adding an excessive content of fly ash to reduce the water-to-binder ratio from 0.50 to 0.26, and the content of fly-ash varied from 52% to 60%. Results show that the cement fly-ash paste presented a reduction of water requirement and an elongation of setting time with the increased content of fly ash. This provides a foundation of maintaining the workability of fresh FAC with a decreased water-to-binder ratio by adding the excessive content of fly ash. The cement fly-ash mortar had a lower early strength due to the slow reaction of fly-ash with Ca(OH)2, which could be improved by steam curing at the initial 24 h due to the excitation of fly-ash activity. At curing age of 28 days, the FAC had the expected axial compressive strength and modulus of elasticity, but the tensile strength was lower than predicted. At the curing age of 56 days, all the basic mechanical properties of FAC reached the prediction. The resistances of FAC to chloride ion penetration and carbonization were realized at a very high level as specified in codes.


2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Lina Wang ◽  
Zhiyu Weng ◽  
Qiang Liu ◽  
Tianliang Wang ◽  
Xuemin Pan ◽  
...  

The traditional treatment of red clay using inorganic materials leads to many serious environmental problems. The study investigates the mechanical properties of red clay using an environmental-friendly material—xanthan gum—through confined compression, direct shear, and scanning electron microscope tests. At the macroscale, xanthan gum content and curing age had obvious effects on the compressibility, presenting the treated red clay was in the category of low compressibility which gradually increased when xanthan gum content exceeded 1.5%. The xanthan gum content and curing age also had significant influences on the cohesion but not on the internal friction angle. The shear strength of red clay can be improved by increasing the cohesion without obviously changing the friction characteristics. After curing for 28 days, the cohesion and internal friction angle of 2.0% xanthan gum-treated soil were effectively improved to 170.44 kPa and 20.56°, which were increased by 69.79% and 9.36°, respectively, compared with untreated red clay. Microscopic analysis indicated that the strengthening mechanism by xanthan gum was derived from changing the arrangement characteristics of soil particles and forming hard biopolymer-red clay matrices. The proper xanthan gum can effectively wrap clay particles and fill pore spaces. However, the extensive stacking of gels would also reduce the effective connection of clay particles and produce local weak points in the soil, resulting in attenuation of mechanical properties. This study enriches the treatment measure of red clay and provides beneficial experiences for biopolymer application on special clay.


2021 ◽  
Vol 8 ◽  
Author(s):  
Zhihong Zhang ◽  
Jiacheng Li

The strength characteristics of cemented paste backfill (CPB) in mining areas are key control factors for the safety assessment of overlying strata. A series of experiments about uniaxial compression and triaxial compression were carried out to study the influence of cement content of filling slurry, curing age, and curing temperature on strength behavior of CPB specimens. The failure mechanism and damage feature of CPB have been investigated. The results show the following: (1) The uniaxial compressive strength of CPB specimens exhibits an upward trend with the increase of cement content and curing age. When the cement content is high, the uniaxial compressive strength increases sharply with increasing curing age. (2) The cohesion of CPB specimens increases with the increase of cement content of filling slurry, curing age, and curing temperature. The cohesion of CPB specimens with curing age 7 days and 14 days increases linearly with increasing cement content. At the later stage of curing age, the strength growth of high cement content backfill is significantly greater than that of low cement content. The internal friction angle of the filling increases slightly with increasing filling cement content, curing age, and curing temperature. (3) The shear strength of CPB specimens at curing age 7 days exhibits an upward trend with the increase of confining pressure, while the shear strength at 14 days and 28 days curing age decreases slightly as the confining pressure increases. (4) With the increase of cement content in backfill, the brittleness increases significantly when the backfill is damaged. The failure mode of CPB specimens changes from monoclinic section shear failure to X-type failure with increasing curing age, and the failure process is divided into four stages: pore compaction, linear elastic deformation, plastic deformation, and post-peak failure.


Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6813
Author(s):  
Yingdi Liao ◽  
Hongyi Shi ◽  
Shimin Zhang ◽  
Bo Da ◽  
Da Chen

In order to solve the problem of lack of natural river sand, crushed waste oyster shells (WOS) were used to replace river sand. By replacing 20% river sand, WOS mortar with different particle sizes of WOS were made for the experiment. Through experimental observation, the initial slump and slump flow loss rate were studied. The effects of different particle sizes and curing times on the compressive strength, flexural strength, static elastic modulus, and dry shrinkage of WOS mortar were analyzed. The relationship formulas between the compressive strength, flexural strength, particle size, and curing age were proposed. The results showed that the setting time and slump flow decreased with a decrease in the particle size of WOS. It was also found that the mortar with fine crushed WOS had high compressive strength, flexural strength, and static elastic modulus at both early and long-term curing age. A formula was proposed to describe the development of the compressive strength with the particle size of WOS and curing time, and the relations among these mechanical properties were discussed. Furthermore, drying shrinkage increased when WOS was used and could not satisfy the standard requirement of 0.075%. In contrast, the addition of fine WOS and double-dose sulfonated naphthalene-formaldehyde superplasticizer (SNF SP) reduced the shrinkage rate of the mortar by 8.35% and provided better workability and mechanical properties for mortar.


2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Wei Yuan ◽  
Renfeng Yang ◽  
Jianyou Yu ◽  
Xiujie Han

This article aims to improve the accuracy and predictability of rebound method in compressive strength evaluation of concrete members of the Yanchong Expressway, which is an important traffic guarantee project for the 2022 Winter Olympics Games in Zhangjiakou city, Hebei Province, China. For this purpose, concrete specimens were prepared by the mixing ratios of C35, C40, and C50. First of all, the paper investigated the effects of curing age, types, and dosage of mineral admixtures (fly ash and slag) on concrete rebound number and compressive strength. Then, the special testing strength curves of 7 d and 90 d curing age were proposed. The results showed that the average relative errors of the special testing strength curves were reduced by 35.99% and 20.26% respectively, compared with the national testing strength curve. Fly ash and slag were beneficial to the growth of concrete rebound numbers but cannot contribute to the growth of concrete compressive strength (except for fly ash single-mixed with 15% dosage). The present results can provide a significant reference for the compressive strength evaluation and later maintenance of concrete members of the Yanchong Expressway or other projects with tight construction period in this area.


2021 ◽  
Vol 1200 (1) ◽  
pp. 012001
Author(s):  
A S Nurfarhanna ◽  
A Suraya Hani ◽  
O Mohamad Hairi ◽  
J Zalipah ◽  
AH Noor Azlina ◽  
...  

Abstract Railway’s concrete sleepers demand high consumption of cement which generates higher energy assumption and carbon emission. Meanwhile, in Malaysia, around 100 tonnes of palm oil fuel ash (POFA) were disposed of in the landfill, which endangering environmental health. However, this POFA have pozzolanic properties that can be employed as cementitious material. Therefore, this study aimed to produce a sustainable concrete sleeper by using POFA as a cement replacement material focusing on the compressive strength and water absorption performance. Concrete samples with a strength grade of 55MPa and w/c of 0.35 were prepared with three design mixes containing 0% (control), 20%(POFA20), and 40%(POFA40) of POFA. For the compressive strength test, a compression machine was used. Meanwhile, the water absorption was measured at atmospheric pressure. Both tests were conducted at 7 and 28 days of curing age. The results show that as the curing age increases, their water absorption and compressive strength improves, indicating a pozzolanic reaction. In terms of POFA content, the water absorption increases by 14% and 54% for POFA20 and POFA40, respectively. Meanwhile, the compressive strength reduced by 39% for POFA20 and 67% for POFA40. Since POFA20 meets the standards, it is however applicable in slab tracks.


2021 ◽  
Vol 2070 (1) ◽  
pp. 012185
Author(s):  
R Premkumar ◽  
J Khaja mohideen ◽  
M Mathan kumar ◽  
T Sundara moorthi ◽  
X. Celestin

Abstract In recent years, there has been a lot of attention paid to the use of textile sludge waste-based products in the building industry to develop ecologically friendly construction materials. An experimental examination of the characteristics of bricks incorporating textile sludge waste and fly ash is presented in this work. In fly ash bricks, fly ash is used to replace textile sludge waste in the following proportions: For the blend percentage of cement, fly ash, and quarry dust, a 230mm × 100mm × 75mm sample size was used. For varying amounts of the components indicated previously, the findings indicate how compressive strength and water absorption fluctuate with curing age. Then we can cast bricks with various mixed proportions of cement, sludge waste, fly ash, and quarry dust using the 230mm × 100mm × 75mm specimen size. After that, the weight, compressive strength, and water absorption of textile sludge with different concentrations of fly ash bricks were compared. This inquiry is primarily concentrated on maximizing the compressive strength of newly produced bricks while limiting weight density and water absorption through extensive laboratory work. The recognition of elements influencing the diverse qualities of bricks is a clear purpose of pursuing this issue as project work.


Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Weidong Jin ◽  
Zhe Wang ◽  
Yongming Ai ◽  
Chenyang Liu

The unconfined compressive strength of cement-modified silty sand in Jilin Province was investigated in this study. For this purpose, various tests were conducted, including the screening test, compaction test, CBR test, X-ray fluorescence detection, and unconfined compressive strength test. Effects of compaction degree, soil quality, water quality, cement content, and curing age were considered. The results show that CBR value is positively correlated with compactness. Two kinds of different water qualities have little effect on unconfined compressive strength of cement-improved soil; with the increase in cement content, the unconfined compressive strength increases, and the power function equation established by the two is significantly correlated. The logarithmic relationship between cement-soil strength and curing age is approximately linear. Through regression analysis, the comprehensive characterization parameters of cement-soil strength, such as water-cement ratio, cement content, and curing age, are put forward. The unconfined compressive strength of cement-modified silty sand has a good power function relationship with the comprehensive characterization parameters, and the fitting degree between the strength prediction formula and the existing research and test data exceeds 90%, which verifies the effectiveness of the comprehensive characterization parameters.


2021 ◽  
Vol 2070 (1) ◽  
pp. 012244
Author(s):  
Kuldeep Kumar ◽  
Manjeet Bansal ◽  
Rishav Garg ◽  
Rajni Garg

Abstract Porous concrete is an amalgamation of coarse aggregate, Portland cement, and water, which permits rainfall water to permeate through the surface and into the ground before it runs off. Porous concrete encompasses little or no fine aggregates and adequate cementitious fixative to coat the coarse aggregate while keeping the voids interconnected. IRC 44-2017 states that range of permeability for pervious concrete should be from 0.135 cm/second to 1.22 cm/second and array of compressive strength should be 5MPa - 25MPa. In this experimental study, two properties of no fine concrete namely compressive strength and porousness at the curing age of 7th & 28rd days has been targeted. Compressive strength and Infiltration tests were conducted on the pervious concrete of grade M10 and M15 by keeping variation of fine aggregates of 0% - 5%. We observed that fines aggregate help to rise the compressive strength of porous concrete but decrease the permeability. Thus, by careful optimization of the mix, pervious concrete can be obtained for suitable use in low strength load.


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