Effect of Low-Calcium Fly Ash on the Resistance of Cement Mortar to Sulfate Attack in the Form of Acid Rain

Author(s):  
Jia Xiao ◽  
Shi Qiong Zhou
Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2694 ◽  
Author(s):  
Shansuo Zheng ◽  
Lihua Niu ◽  
Pei Pei ◽  
Jinqi Dong

In order to evaluate the deterioration regularity for the mechanical properties of brick masonry due to acid rain corrosion, a series of mechanical property tests for mortars, bricks, shear prisms, and compressive prisms after acid rain corrosion were conducted. The apparent morphology and the compressive strength of the masonry materials (cement mortar, cement-lime mortar, cement-fly ash mortar, and brick), the shear behavior of the masonry, and the compression behavior of the masonry were analyzed. The resistance of acid rain corrosion for the cement-lime mortar prisms was the worst, and the incorporation of fly ash into the cement mortar did not improve the acid rain corrosion resistance. The effect of the acid rain corrosion damage on the mechanical properties for the brick was significant. With an increasing number of acid rain corrosion cycles, the compressive strength of the mortar prisms, and the shear and compressive strengths of the brick masonry first increased and then decreased. The peak stress first increased and then decreased whereas the peak strain gradually increased. The slope of the stress-strain curve for the compression prisms gradually decreased. Furthermore, a mathematical degradation model for the compressive strength of the masonry material (cement mortar, cement-lime mortar, cement-fly ash mortar, and brick), as well as the shear strength attenuation model and the compressive strength attenuation model of brick masonry after acid rain corrosion were proposed.


2015 ◽  
Vol 14 (1) ◽  
pp. 043-052
Author(s):  
Monika Jaworska

The effects of entrained air on sulphate resistance of fly ash blended cements mortars long term immersed in Na2SO4 solution were investigated. The expansion strains and decrease in strength of air entrained mortars were faster than those of non-air entrained ones. It was found with SEM and XRD analyses that ettringite and gypsum were the main sulfate attack products. The SEM studies of mortars microstructure showed that the highest amount of ettringite observed occurred in air voids partially filled with this phase. The sulphate resistance of AE and nAE mortars containing high or low calcium fly ash blended cements was significantly higher compared to plain OPC mortar.


2018 ◽  
Vol 69 (8) ◽  
pp. 2040-2044
Author(s):  
Georgeta Velciu ◽  
Virgil Marinescu ◽  
Adriana Moanta ◽  
Ladislau Radermacher ◽  
Adriana Mariana Bors

The influence of fly ash adittion (90 % fraction [ 100 mm) on the cement mortar characteristics was studied. The XRD, XRF, SEM and FTIR determinations indicated that fly ash used has a hollow microstructure of microsphere and cenosphere whose total content in SiO2, Al2O3 and Fe2O3 is 88.63 % and that of CaO and MgO of 8.55 %. The mechanical, thermal and dielectric determinations made on mortar samples with content of fly ash in the 0-40 % range have highlighted fact that the mechanical strength of cement mortars is maximal at 20 %, the increase in fly ash content leads to a decrease in relative density and thermal conductivity as well as and to increased dielectric losses tgd.


Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 875
Author(s):  
Chenchen Luan ◽  
Qingyuan Wang ◽  
Fuhua Yang ◽  
Kuanyu Zhang ◽  
Nodir Utashev ◽  
...  

There have been a few attempts to develop prediction models of splitting tensile strength and reinforcement-concrete bond strength of FAGC (low-calcium fly ash geopolymer concrete), however, no model can be used as a design equation. Therefore, this paper aimed to provide practical prediction models. Using 115 test results for splitting tensile strength and 147 test results for bond strength from experiments and previous literature, considering the effect of size and shape on strength and structural factors on bond strength, this paper developed and verified updated prediction models and the 90% prediction intervals by regression analysis. The models can be used as design equations and applied for estimating the cracking behaviors and calculating the design anchorage length of reinforced FAGC beams. The strength models of PCC (Portland cement concrete) overestimate the splitting tensile strength and reinforcement-concrete bond strength of FAGC, so PCC’s models are not recommended as the design equations.


Author(s):  
Keyu Chen ◽  
Dazhi Wu ◽  
HaiXiang Chen ◽  
Guoqing Zhang ◽  
Ruolan Yao ◽  
...  
Keyword(s):  
Fly Ash ◽  

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 681
Author(s):  
Na Yan ◽  
Qingqing Tang ◽  
Ying Zhang ◽  
Guowen Sun

This study was conducted in order to investigate when low-calcium fly ash plays a physical or chemical effect and what is the chemical effect proportion of low-calcium fly ash. Two types of low-calcium fly ash and quartz powder, with similar fineness as active and inert admixtures, were used as materials in this study. Under different water/binder ratios and hydration ages, the effects of the different types of admixtures and their dosages on the flexural and compressive strength of the composites were studied. X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen adsorption methods, in addition to an assessment of the degree of hydration of the fly ash, were employed to observe the hydration products at different ages, the microstructures of the hydration products, as well as their surface areas and pore size distributions. The results show that during the hydration period of 28 days, the low-calcium fly ash has a micro-aggregate filling physical effect. However, after 56 days, the hydration degree of fly ash begins to exceed 1%. This illustrates that the low-calcium fly ash has both the pozzolanic activity effect and micro-aggregate filling effect. In contrast, the low-calcium fly ash hydrated for 90 days is still dominated by the physical filling effect.


Author(s):  
Chidanand Patil ◽  
M. Manjunath ◽  
Sateesh Hosamane ◽  
Sneha Bandekar ◽  
Rubeena Athani

1989 ◽  
Vol 178 ◽  
Author(s):  
Kirsten G. Jeppesen

AbstractSpray dried absorption products (SDA) having special characteristics are used as substitutes for cement in the preparation of mortars; the qualities of the resulting mixed mortars are described. Conditions are described for mortar mixes, data for which were presented at the MRS Fall Meeting 1987.The influence of the composition of the SDA on water requirement and setting time has been studied. A full scale project involving 3 precast, reinforced concrete front-elements containing 20 and 30 wt.% SDA is described. Strength development, mineralogical composition and corrosion were monitored for two years.A non-standard freeze-thaw experiment was performed which compares mortars containing SDA and fly ash (FA) and also shows the effect of superplasticizer.The possibility of improving the SDA by grinding has been tested and a limited improvement has been found. The strength of the mixed mortars seems slightly influenced by the grain size of SDAGypsum (CaSO4·2H2O), synthetic calcium-sulphite (CaSO3·½H2O) and 2 SDAs have been used as retarders for cement clinker. Mortar test prisms have been cast and comparative strengths after curing for 3 years are reported


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