Use of CO2 as an Accelerated Curing Agent for Concrete Blocks

2008 ◽  
Vol 400-402 ◽  
pp. 81-87 ◽  
Author(s):  
Cai Jun Shi ◽  
Qing Yan Zou
Keyword(s):  
Curing Agent ◽  
Steam Curing ◽  
Co2 Gas ◽  
Accelerated Curing ◽  
Concrete Mixtures ◽  
Concrete Masonry ◽  
Conditioning Period ◽  
Concrete Blocks ◽  
Moist Environment ◽  
High Degree

In this project, a process was developed to cure concrete masonry blocks using CO2. It was found that the strength of concrete mixtures for block manufacture after CO2 curing was close to that after conventional steam curing. A dry pre-conditioning before CO2 curing was very critical to achieve high degree of CO2 curing. The specimen pre-conditioned in the moist environment hydrates more than those pre-conditioned in the dry environment during the pre-conditioning period. However, much less CaCO3 formed in the former that that in the latter after the CO2 curing. Thus, the CO2 curing is mainly contributed by the reactions between CO2 gas and cement clink minerals.

River Soil & Sand Solidified Blocks as Ballast in Beach Protection

2013 ◽  
Vol 779-780 ◽  
pp. 323-326 ◽  
Author(s):  
Jing Min Mao ◽  
Da Feng Gao
Keyword(s):  
Yangtze River ◽  
Setting Time ◽  
Experimental Studies ◽  
Curing Agent ◽  
The Yangtze River ◽  
Environment Protection ◽  
Time Stability ◽  
Alternative Materials ◽  
Concrete Blocks ◽  
Protection Engineering

This paper deals with the feasibility of beach protection project alternative materials - the Yangtze River soil and sand, applies PCSB curing agent to solidify it and to produce beach protection blocks. Experimental studies on the performance of strength, setting time, stability and anti-erosion have been carried out to inquire into the regularity of solidification. Using soil and sand curing blocks instead of concrete blocks in the application of Yangtze River beach protection engineering has advantages of technology, economy and environment protection etc.

scholarly journals Interactions Between Chill-Hours and Degree-Days Affect Carpogenic Germination in Monilinia vaccinii-corymbosi

2001 ◽  
Vol 91 (1) ◽  
pp. 77-83 ◽  
Author(s):  
H. Scherm ◽  
A. T. Savelle ◽  
P. L. Pusey
Keyword(s):  
Laboratory Experiments ◽  
Field Experiments ◽  
Degree Days ◽  
Carpogenic Germination ◽  
Conditioning Period ◽  
Low Degree ◽  
Heating Degree Days ◽  
Relationship Of ◽  
High Degree ◽  
The Relationship

The relationship of cumulative chill-hours (hours with a mean temperature <7.2°C) and heating degree-days (base 7.2°C) to carpogenic germination of pseudosclerotia of Monilinia vaccinii-corymbosi, which causes mummy berry disease of blueberry, was investigated. In two laboratory experiments, pseudosclerotia collected from rabbiteye blueberry in Georgia were conditioned at 5 to 6°C for 26 to 1,378 h prior to placement in conditions favorable for germination and apothecium development. The number of chill-hours accumulated during the conditioning period affected the subsequent proportion of pseudosclerotia that germinated and produced apothecia, with the greatest incidence of carpogenic germination occurring after intermediate levels of chilling (≈700 chill-hours). The minimum chilling requirement for germination and apothecium production was considerably lower than that reported previously for pseudo-sclerotia from highbush blueberry in northern production regions. The rate of carpogenic germination was strongly affected by interactions between the accumulation of chill-hours and degree-days during the conditioning and germination periods; pseudosclerotia exposed to prolonged chilling periods, once transferred to suitable conditions, germinated and produced apothecia more rapidly (after fewer degree-days had accumulated) than those exposed to shorter chilling periods. Thus, pseudosclerotia of M. vaccinii-corymbosi are adapted to germinate carpogenically following cold winters (high chill-hours, low degree-days) as well as warm winters (low chill-hours, high degree-days). Results were validated in a combined field-laboratory experiment in which pseudosclerotia that had received various levels of natural chilling were allowed to germinate in controlled conditions in the laboratory, and in two field experiments in which pseudosclerotia were exposed to natural chilling and germination conditions. A simple model describing the timing of apothecium emergence in relation to cumulative chill-hours and degree-days was developed based on the experiments. The model should be useful for better timing of field scouting programs for apothecia to aid in management of primary infection by M. vaccinii-corymbosi.

Empirical Prediction Models for Strength Gain Properties of Fly Ash Based Concrete Subjected to Accelerated Curing

2018 ◽  
Vol 1150 ◽  
pp. 73-90
Author(s):  
Vallarasu Manoharan Sounthararajan
Keyword(s):  
Fly Ash ◽  
Prediction Models ◽  
Pulse Velocity ◽  
Hot Water ◽  
Experimental Investigations ◽  
Strength Gain ◽  
Steam Curing ◽  
Empirical Prediction ◽  
Accelerated Curing ◽  
Water Curing

Experimental investigations on the early age, strength gain properties of fly ash blended cement concretes containing low and high volume fly ash replacement were studied. Concrete mixes were prepared with two different fly ash contents and varying concrete ingredients with water to binder ratio (w/b), fine to coarse aggregate ratio (F/c) and accelerator dosage. Five different curing techniques, namely controlled humidity curing; hot air oven curing, steam curing, hot water curing and normal water curing were adopted for curing the fly ash based concretes. Test results showed evidence the influence of accelerating admixtures and accelerated curing for obtaining the high early strength properties in fly ash mixed concrete. Most notably a maximum 1 day compressive strength of 40.20 MPa and 34.60 MPa with low (25%) and high (50%) volume fly ash concretes were obtained respectively in this study. Experimental results clearly indicated that the improvements on the strength gain properties with the careful selection of mix ingredients; accelerator addition and accelerated curing in fly ash based concrete mixes. Also, significant improvements on the flexural strength, elastic modulus, dynamic modulus and the ultrasonic pulse velocity test were noticed.

Performance Study on Masonries of Different Aerated Concrete Blocks

2014 ◽  
Vol 633 ◽  
pp. 299-302 ◽  
Author(s):  
Peng Fei Peng ◽  
Xian Ming Qin ◽  
Yu Sheng Wu
Keyword(s):  
Water Absorption ◽  
Natural Condition ◽  
Crack Width ◽  
Concrete Block ◽  
Performance Study ◽  
Shrinkage Cracking ◽  
Concrete Cracking ◽  
Concrete Masonry ◽  
Concrete Blocks ◽  
Aerated Concrete

The masonries with a square of 2m×3m of 3 different aerated concrete blocks were built respectively, and plastered with plastering mortar. The shrinkage-cracking property and other performances of different aerated concrete masonries were studied in natural condition. The results showed that, there were less cracks and smaller crack width in the masonry of aerated concrete with low water absorption, the condition of aerated concrete cracking can be improved by plastering with plastering mortar; the shrinkage of aerated concrete block masonry with low water absorption is smaller, the shrinkage of aerated concrete masonry plastered by special plastering mortar is smaller.

Influence de la température minimale du cycle de gel–dégel sur la détérioration du béton par écaillage en présence de sels fondants

1996 ◽  
Vol 23 (3) ◽  
pp. 595-601
Author(s):  
J. Marchand ◽  
M. Pigeon ◽  
L. Boisvert
Keyword(s):  
Test Procedure ◽  
Air Entrainment ◽  
Freezing Temperature ◽  
Freezing And Thawing ◽  
Concrete Mixtures ◽  
Conditioning Period ◽  
Binder Ratio ◽  
Freezing Cycle ◽  
Air Void ◽  
Scaling Resistance

Eight different concrete mixtures were prepared to investigate the influence of the minimum temperature of the freezing and thawing cycle on scaling deterioration due to deicer salt. In addition to the two minimum temperatures studied (−18 and −9 °C), test variables included the type of binder (with or without silica fume), the water/binder ratio (0.35 or 0.45), the characteristics of the air-void network (with or without air entrainment), and the drying temperature during the conditioning period prior to the scaling test (20, 40, or 110 °C). The scaling resistance to deicer salt of all concrete mixtures was assessed according to the prescriptions of the ASTM C672 test procedure using a 3 % NaCl solution. Test results indicate that a reduction of the minimal temperature from −9 to −18 °C significantly increases the scaling deterioration of concrete due to deicer salt. Key words: freezing cycle, scaling resistance, minimal freezing temperature, deicer salts.

scholarly journals The Utilization of Recycled Masonry Aggregate and Recycled EPS for Concrete Blocks for Mortarless Masonry

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 1923 ◽  
Author(s):  
Tereza Pavlu ◽  
Kristina Fortova ◽  
Jakub Divis ◽  
Petr Hajek
Keyword(s):  
Mechanical Properties ◽  
Thermal Properties ◽  
Masonry Wall ◽  
Expanded Polystyrene ◽  
Mechanical And Thermal Properties ◽  
Concrete Mixtures ◽  
Wall Structures ◽  
Different Types ◽  
Concrete Blocks ◽  
Recycled Masonry

The main aim of this paper is to carry out the environmentally based enhancement of a concrete mixture containing recycled materials whilst considering natural resource consumption as well as mechanical and thermal property levels. The developed concrete is intended to be used in mortarless masonry wall structures. Ten concrete mixtures with different types and replacement rates of recycled masonry aggregate and recycled expanded polystyrene were prepared, and their mechanical and thermal properties were experimentally investigated. It was found that the use of recycled masonry aggregate led to better thermal properties while maintaining sufficient mechanical properties. On the contrary, the addition of recycled expanded polystyrene did not significantly affect the thermal properties of concrete, but the mechanical properties considerably declined. For this reason, the recycled masonry aggregate is suitable to use as an aggregate for concrete masonry blocks for wall structures.

scholarly journals Compressive strength of masonry constructed with high strength concrete blocks

2017 ◽  
Vol 10 (6) ◽  
pp. 1273-1319 ◽  
Author(s):  
E. S. FORTES ◽  
G. A. PARSEKIAN ◽  
J. S. CAMACHO ◽  
F. S. FONSECA
Keyword(s):  
Compressive Strength ◽  
High Strength Concrete ◽  
Strain Curve ◽  
High Strength ◽  
Masonry Walls ◽  
Strength Ratio ◽  
Stress Strain Curve ◽  
Strength Concrete ◽  
Concrete Masonry ◽  
Concrete Blocks

Abstract Although the use of high strength concrete blocks for the construction of tall buildings is becoming common in Brazil, their mechanical properties and behavior are not fully understood. The literature shows a gap in experimental studies with the use of high strength concrete blocks, i.e., those with compressive strength greater than 16 MPa. The work presented herein was conducted in order to study the behavior of high strength structural masonry. Therefore, the compressive strength and modulus of elasticity of concrete block walls tested under axial load were assessed. The specimens included grouted and ungrouted walls and walls with a mid-height bond beam; ungrouted walls were constructed with face-shell and full mortar bedding. The walls were built and tested in the laboratory of CESP and in the Structures Laboratory of the UNESP Civil Engineering Department in Ilha Solteira (NEPAE). Concrete blocks with nominal compressive strength of 16 (B1), 24 (B2) and 30 (B3) MPa were used. Ungrouted masonry walls had a height of 220 cm and a width of 120 cm while grouted masonry walls had a height of 220 cm and a width of 80 cm. Traditional Portland cement, sand and lime mortar was used. The testing program included 36 blocks, 18 prisms, 9 ungrouted walls (6 with face-shell mortar bedding and 3 with full mortar bedding), 9 grouted masonry walls, and 12 ungrouted walls with a bond beam at mid-height. The experimental results were used to determine the compressive strength ratio between masonry units, prisms and masonry walls. The analyses included assessing the cracking pattern, the mode of failure and the stress-strain curve of the masonry walls. Tests results indicate that the prism-to-unit strength ratio varies according to the block strength; that face-shell mortar bedding is suitable for high strength concrete masonry; and that 20% resistance decrease for face-shell mortar bedding when compared with full mortar bedding is a conservative consideration. The results also show that using a bond beam at the mid-height of the wall does not lead to a compressive strength decreased but it changes the failure mode and the shape of the stress-strain curve. In addition, the results show that estimating E = 800 fp is conservative for ungrouted masonry walls but reasonably accurate for grouted masonry walls and that there is no reason to limit the value of E to a maximum value of 16 GPa. Furthermore, the results show that, for design purposes, a wall-to-prism strength ratio value of 0.7 may be used for high strength concrete masonry.

scholarly journals Study on aerated concrete using steam curing test method

2021 ◽  
Vol 309 ◽  
pp. 01206
Author(s):  
Rohith Naidu T Y ◽  
G.V.V Satyanarayana
Keyword(s):  
Concrete Block ◽  
Vital Role ◽  
Test Method ◽  
Aluminium Content ◽  
Steam Curing ◽  
Dead Weight ◽  
Structural Wall ◽  
Aluminium Powder ◽  
Concrete Blocks ◽  
Aerated Concrete

The Accumulation of warm and moisture in building walls plays an vital role in its upkeep and power conservation. Aerated Concrete block, an environmental material gives an anticipated result to building construction. Aerated Concrete can build light weight, eco-friendly, non-structural wall, reduced dead weight concrete blocks. Aerated Concrete is developed introducing aluminium powder which reacts with the calcium hydroxide on hydration of cement. Several curing test methods are done to find out the optimum dosage of aluminium content. The Aerated concrete blocks are pre-casted by mixing Portland cement, fly ash, GGBS, quarry dust, lime stone powder, water and aluminium powder.

THE EFFECTS OF VISUAL STABILITY INDEX ON FRESH AND HARDENED PROPERTIES OF SELF CONSOLIDATING CONCRETE UNDER ACCELERATED CURING

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Mohamed Khalafalla ◽  
Joseph Owino
Keyword(s):  
Mechanical Vibration ◽  
Stability Index ◽  
Labor Cost ◽  
Visual Stability ◽  
Self Consolidating Concrete ◽  
University Of Tennessee ◽  
Class A ◽  
Accelerated Curing ◽  
Concrete Mixtures ◽  
Hardened Properties

Self-consolidating concrete, also known as self-compacting concrete (SCC), is a highly flowable concrete that spreads into place and fills formwork without the need for mechanical vibration. SCC reduces the time and labor cost needed for concrete placement. This study is part of the proposed project by Tennessee Department of Transportation (TDOT) carried out by University of Tennessee at Chattanooga (UTC) to develop four new SCC mixtures (two Class P-SCC (precast) and two Class A-SCC (general use), and insure they meet the minimum strength and durability requirements for TDOT Class P and Class A mixtures. The objectives of the study are to analyze effects of visual stability index (VSI) on both fresh and hardened properties of Class PSCC concrete under the accelerated curing condition. In addition, the relationship between VSI and fresh segregation of SCC is investigated. A total of 24 concrete mixtures varying in VSI values were produced for the study. Different sizes of coarse aggregates materials were used during the mixing process, as well as different kinds of sands. A number of fresh and hardened properties tests were performed on the concrete mixtures to assess the performance of the mixes. The SURE CURE system is used to accelerate the curing process of the concrete. Finally, the results of this study are analyzed according to the coarse aggregate sizes and evaluated to recommend performance specifications for Class P-SCC for TDOT adoption of SCC standard operating procedures of the precast elements.

Ecophysiological responses of desiccation-tolerant cryptobiotic crusts

2011 ◽  
Vol 6 (5) ◽  
pp. 838-849 ◽  
Author(s):  
Evelin Péli ◽  
Nie Lei ◽  
Tamás Pócs ◽  
Zsanett Laufer ◽  
Stefan Porembski ◽  
...  
Keyword(s):  
Photosynthetic Activity ◽  
Photosynthetic Pigment ◽  
Global Scale ◽  
Climatic Conditions ◽  
Co2 Gas ◽  
Tropical Areas ◽  
Ecophysiological Responses ◽  
High Degree ◽  
Cryptobiotic Crusts

AbstractIn our present studies, the recovery of photosynthetic activity after rehydration was demonstrated. We measured chlorophyll fluorescence, CO2 gas exchange and the pigment composition in the previously long-term air-dried cryptogamic inselberg crusts collected from two tropical areas. The cryptobiotic crusts were collected from different localities on similar ecological and climatic conditions from extreme habitats of inselbergs (outcrops). These inselbergs are characterized by a dry microclimate and are covered by scarce soil. We found that the ecophysiological responses of both cryptogamic inselberg crusts showed an extremely high degree of desiccation-tolerance due to the fast and full recovery during rehydration. The photosynthetic activity of the cryptobiotic crusts were restored and regained within 15 and 40 min, respectively, after rehydration. Photosynthetic activity of the crusts was retained at all applied light intensities when enough water was available, however the degree of the recovery was different between the crusts. Photosynthetic pigment contents were strongly and positively correlated with water content. Our results indicated that tropical desiccation-tolerant cryptogamic crusts found on inselberg rock surfaces have CO2 fixation ability in the range of cyanobacteria and lichens, suggesting that at a global scale they can assimilate CO2 in a significant amount.

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