Influence of construction-induced damage on the degradation of freeze—thawed lightweight cellular concrete

During the construction of lightweight cellular concrete(LCC),material damage frequently occurs,causing the degradation and deterioration of the mechanical performance,durability,and subgrade quality of LCC.The construction-induced damage can be more significant than those from the service environment of LCC,such as freeze-thaw(F-T)action in cold regions.However,the effect of construction-induced damage on LCC during F-T cycles is often ignored and the deterioration mechanisms are not yet clarified.In this study,we investigated the factors causing damage during construction using a sample preparation method established to simulate the damage in the laboratory setting.We conducted F-T cycle tests and microstructural characterization to study the effect of microstructural damage on the overall strength of LCC with different water contents under F-T actions.We established the relationship between the pore-area ratio and F-T cycle times,pore-area ratio,and strength,as well as the F-T cycle times and strength under different damage forms.The damage evolution is provided with the rationality of the damage equation,verified by comparing the measured and predicted damage variables.This study would serve as a guide for the construction and performance of LCC in cold regions.

Quality evaluation of lightweight cellular concrete by an ultrasound-based method

The accuracy of subgrade quality evaluation is important for road safety assessment.Since there is little research work devoted to testing lightweight cellular concrete(LCC)by an ultrasound-based method,the quantitative relation between ultrasonic testing results and the quality of LCC subgrade is not well understood.In this paper,the quality of LCC subgrade was evaluated with respect to compressive strength and crack discrimination.The relation between ultrasonic testing results and LCC quality was explored through indoor tests.Based on the quantitative relation between ultrasonic pulse velocity and compressive strength of LCC,a fitting formula was established.Moreover,after the LCC became cracked,the ultrasonic pulse velocity and ultrasonic pulse amplitude decreased.After determining the lower limiting values of the ultrasonic pulse velocity and ultrasonic pulse amplitude through the statistical data,it could be calculated whether there were cracks in LCC subgrade.The ultrasonic testing results showed that the compressive strength of the LCC subgrade was suitable for purpose and there was no crack in the subgrade.Then core samples were taken from the subgrade.Comparisons between ultrasonic testing results of subgrade and test results of core samples demonstrated a good agreement.

Experimental Testing of Cellular Construction Materials Containing Flax Particles

The feasibility of a sustainable non-autoclaved cellular concrete,based on flax vegetable co-products,for the production of usable specimen in the lightweight construction field,has been investigated experimentally.The produced specimen,containing various volume ratios of flax particles with respect to preformulatd Tradical PF70 lime binder of 0,1,and 2,were lightened by creating a porous structure in the matrix through the addition of 0.3%wt.Aluminium powder(able to react with calcium hydroxide from the binder and result in microscopic air-bubbles).Fresh and hardened specimen properties,including hydration,fresh density,porosity,hardened density,compressive and flexural strengths,toughness energy,and dry thermal conductivity at different temperatures,were assessed for varying flax-to-binder ratios.Results have shown that the addition of Aluminum powder leads to restrain the setting time delay of binder-based lime.Moreover,the hardened material displays a significant decrease in specimen density,thereby resulting in a compressive strength level compatible with that required in the cellular construction materials sector.Results also highlighted the ability of added flax to induce a change in the specimen from brittle to ductile behavior.Moreover,a high degree of thermal insulation can be achieved,which makes the cellular specimen based on flax particle suitable as insulated-bearing walls material.

Effect of Active Mineral on Load-Bearing Autoclaved Aerocrete

Influence of ultrafine active mineral (DK mineral) on mechanical property of fly ash based load bearing aerocrete was analyzed. The result shows that the addition of DK mineral in a suitable amount can enhance obviously the compressive strength of aerocrete. According to the SEM EDS and X ray diffraction analyses, the crystal shapes of hydration products are well developed and interlocked for samples containing DK mineral. Its microstructure is denser than that of the samples without DK mineral. Having a good activation, the DK mineral makes both the type and the quantity of hydrated products be obviously superior to that of the contrast sample.