LWA as Internal Curing Agent to Control Availability of Internal Curing Water in Concrete

2013 ◽  
Vol 1612 ◽  
Author(s):  
Luis Emilio Rendon ◽  
Montserrat Rendon ◽  
Norma Ramirez
Keyword(s):  
Lightweight Aggregate ◽  
Normal Weight ◽  
Internal Curing ◽  
Appreciable Effect ◽  
Curing Agent ◽  
Concrete Compressive Strength ◽  
Concrete Shrinkage ◽  
Coarse Aggregates ◽  
Paste Content ◽  
High Absorption

ABSTRACTThe effectiveness of lightweight aggregate (LWA) as an internal curing agent (ICA) to reduce concrete shrinkage is evaluated for repair concrete used in cultural heritage works (RCCHW) using curing periods of 30 days. Normal weight aggregate is replaced by LWA at volume replacement levels ranging from 10 to 14%. The mixtures contain Portland cement maintaining the paste content at approximately 24.1% of concrete volume. Comparisons are made with mixtures containing low-absorption granite and high-absorption limestone normal weight coarse aggregates. At the replacement levels used in this study, LWA results in a small reduction in concrete density, no appreciable effect on concrete compressive strength, and a decrease in concrete shrinkage for drying periods up to 30 days. With a curing period of 14 days, all mixtures with LWA exhibited less shrinkage than the mixtures with either low- or high-absorption normal weight aggregates.

scholarly journals Evaluation of internal curing effects on concrete

2019 ◽  
Vol 39 (2) ◽  
Author(s):  
Nancy Torres Castellanos ◽  
Sergio David Rodríguez-Torres
Keyword(s):  
Modulus Of Elasticity ◽  
Lightweight Aggregate ◽  
Internal Curing ◽  
Curing Agent ◽  
Lightweight Aggregates ◽  
Clay Bricks ◽  
Air Content ◽  
Coarse Aggregates ◽  
Strength And Durability ◽  
Compression Resistance

The objective of the present research was the evaluation of some fresh and hardenedstate properties of concretes, in which coarse aggregates were partially replaced by lightweight ones previously saturated, in percentages of 15% and 25 %. The lightweight aggregates were calcined clays and crushed clay bricks. In parallel, the effect of an internal curing agent composed of superabsorbent polymers (SAP) was evaluated. The properties evaluated in the fresh and hardenedstate of concretes with a/c of 0,30 were: slum, air content, density, compression resistance, modulus of elasticity, initial superficial absorption and chlorine resistance. Results showed the efficiency of crushed clay bricks as internal curing, as well as the need for deeper research on the use of the evaluated lightweight aggregate as internal curing aggregate in concrete. Results indicate that the crushed clay bricks and the internal curing agent fulfill the behavior expected, in terms of strength and durability. However, the evaluated lightweight aggregate produces a reduction in the resistance and durability of the concrete. The observed behavior in strength and durability is especially variable for the age of 180 days, compared with conventional concretes.

A Study of Interfacial Transition Zone in Lightweight Aggregate Concrete

2011 ◽  
Vol 194-196 ◽  
pp. 935-941
Author(s):  
How Ji Chen ◽  
Chien Kuo Lin ◽  
Wen Po Tsai ◽  
Te Hung Liu
Keyword(s):  
Tensile Strength ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Lightweight Aggregate Concrete ◽  
Lightweight Aggregates ◽  
X Ray Diffraction ◽  
Transition Zones ◽  
Different Types ◽  
Slight Downward Trend ◽  
High Absorption

If concrete is observed at the microscopic level, it can be seen to contain many interfacial transition zones (ITZ), resulting in the weakening of its mechanical properties; as the physical properties of lightweight aggregates (LWA), such as their high absorption, are clearly different from those of normal weight aggregates (NWA), they may lead to variations in the ITZ of lightweight aggregates concrete (LWAC), making its mechanical behavior different from that of normal concrete.This study takes three types of LWA with different rates of absorption as its subjects in order to examine the effects of LWA absorbency on ITZ. The main variables tested include water/binder (W/B) ratio, amount of fly ash substituted for cement, and the saturation states of the four types of LWA, with three different types of microscopic tests used to observe the microstructure of ITZ in concrete, and analyze and compare their differences with ITZ in concrete made with NWA. The results of the study indicate that in LWAC, ITZ with weaker tensile strength did not appear around highly absorbent LWA; only the sample group with a W/B ratio of 0.29 did not show apparent absorption due to the higher viscosity of the mortar, resulting in a slight downward trend in tensile strength, but it was still superior to the tensile strength of ITZ in typical NWA.Observation using scanning electron microscopy (SEM) found that inner pores and cracks of ITZ in LWAC were all smaller than in NWC; X-ray diffraction (XRD) tests indicated that the amount of CH crystals in ITZ was greater than LWAC; and microhardness testing found that microhardness values were higher closer to the surface of the LWA, with some even exceeding that of concrete. The increase in the tensile strength of ITZ in LWAC subsequent to the addition of pozzolanic materials was limited; their improvement of the weakness planes formed by ITZ in NWA concrete, however, was more apparent. An LWA has higher water absorbency capacity when in an absolutely-dry condition, which can markedly increase the strength of ITZ; conversely, if an LWA is in saturated surface dry (SSD) condition, its ITZ behave like those of concrete.

scholarly journals Properties and Internal Curing of Concrete Containing Recycled Autoclaved Aerated Lightweight Concrete as Aggregate

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Teewara Suwan ◽  
Pitiwat Wattanachai
Keyword(s):  
Compressive Strength ◽  
Lightweight Concrete ◽  
Value Added ◽  
Aggregate Size ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Green Technology ◽  
Internal Curing ◽  
Low Carbon ◽  
Mix Proportion

Global warming is a vital issue addressed to every sector worldwide, including the construction industry. To achieve the concept of green technology, many attempts have been carried out to develop low-carbon footprint products. In the construction sector, Autoclaved Aerated Concrete (AAC) has become more popular and been manufactured to meet the construction demand. However, errors from manufacturing process accounted for approximately 3 to 5% of the AAC production. The development of AAC waste as lightweight aggregate in concrete is one of the potential approaches which was extendedly studied in this paper. The results showed that the compressive strength of AAC-LWA concrete was decreased with an increase in volume and coarse size. The optimum mix proportion was the AAC aggregate size of 1/2′′ to 3/8′′ with 20 to 40% replacement to normal weight aggregate. Internal curing by AAC-LWA was also observed and found to provide sufficient water inside the specimens, leading to an achievement in higher compressive strength. The main goal of this study is not only utilising unwanted wastes from industry (recycling of waste materials) but also building up a new knowledge of using AAC-LWA as an internal curing agent as well as the production of value-added lightweight concrete products.

scholarly journals Use of normal-density high-absorption limestone aggregate as internal curing agent in concrete

2015 ◽  
Vol 42 (11) ◽  
pp. 827-833 ◽  
Author(s):  
Rómel Solís-Carcaño ◽  
Laura V. Terán-Marín ◽  
Eric I. Moreno
Keyword(s):  
Compressive Strength ◽  
Internal Curing ◽  
Hydration Process ◽  
Normal Density ◽  
Curing Agent ◽  
Limestone Aggregate ◽  
Rock Aggregate ◽  
Additional Water ◽  
Natural Aggregates ◽  
High Absorption

A common practice to provide additional water for the hydration process of cement is to use special aggregates that act as agents incorporating water to the concrete (lightweight natural aggregates or polymers). Previous studies have suggested that normal-density high-absorption limestone aggregates may produce a similar effect. The aim was to determine if they can function as an internal curing agent. The methodology consisted of concrete specimens employing two types of aggregates and subjected to three different curing treatments. Results showed similar values of compressive strength and porosity among the concrete cured under wet and dry treatments for the high-absorption limestone aggregate but not for the river rock aggregate. Thus, this effect was attributed to the internal curing properties of the high-absorption limestone aggregate.

Expermental Study on the Mixture Ratio and the Compressive Strength of Concrete with Recycle Crushed Brick Coarse Aggregate

2014 ◽  
Vol 584-586 ◽  
pp. 1362-1365 ◽  
Author(s):  
Qin Liu ◽  
Xiao Na Zhang
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Engineering Application ◽  
Recycled Concrete ◽  
Concrete Compressive Strength ◽  
Mixture Ratio ◽  
Coarse Aggregates ◽  
Compressive Performance ◽  
Compressive Strength Of Concrete ◽  
High Absorption

Considering the high absorption of water is a distinctive feature of recycled crushed bricks coarse aggregate, the mixture ratio text of recycled concrete using crushed bricks as coarse aggregate is carried out, and the compressive performance is studied.The resert indicate , the strength grade of recycled concrete which using bricks as coarse aggregate can reach C20 and C25, characterisitic value of cubic concrete compressive strength at the age of 28 days are 21.2MPa and 27.55MPa;Based on regression analysis of test data , the formulas which estimated the strength of recycled coarse aggregates concrete are given out. Calculated values are in agreement with the measurement values, which can provide a reference for engineering application.

scholarly journals Compressive Strength of Steel-Fiber Concrete with Artificial Lightweight Aggregate (ALWA)

2018 ◽  
Vol 4 (9) ◽  
pp. 2011 ◽  
Author(s):  
Meity Wulandari ◽  
Tavio Tavio ◽  
I G. P. Raka ◽  
Puryanto Puryanto
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Steel Fiber ◽  
Aggregate Size ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Lightweight Aggregates ◽  
Normal Weight Concrete ◽  
Coarse Aggregates ◽  
Steel Fiber Concrete

In the last decade, there have been many innovations developed to replace the aggregate as material for concrete, particularly the coarse aggregate using the artificial lightweight aggregates a.k.a. ALWA. In the study, the main ingredient used to develop the artificial lightweight aggregates is the styrofoam. Styrofoam has a lightweight characteristic so that it can reduce the density of the concrete. If the density of the concrete can be lighter than the normal-weight concrete then the overall weight of the structure of a building will also be lighter. Thus, the shear force due to the earthquake will also be smaller so that the safety of the building becomes better. The styrofoam used was dissolved with the acetone solution and formed into granules in which the size resembled the coarse aggregate size of about 10 to 20 mm. The styrofoam which has been formed then dried up so that the texture becomes hard. In addition, steel fiber was also used as an added ingredient in concrete mixtures so that the concrete was highly resistant against cracking and was expected to increase the compressive strength of the concrete. ALWA compositions used to replace coarse aggregates were 0%, 15%, 50%, and 100%. While the composition of steel fiber used was 0%, 0.75%, and 1.5% of the total volume of the cylinder. The type of steel fiber used was hooked-end steel fiber with the diameter and the length of 0.8 mm and 60 mm, respectively. The results showed that the concrete with 15% styrofoam ALWA and 1.5% of steel fiber were able to produce optimum compressive strength by 28.5 MPa and the modulus of elasticity by 23,495 MPa. In addition, the use of Styrofoam ALWA as a substitution to the coarse aggregate can reduce the density of concrete as much as 5 to 35%.

scholarly journals Evaluation of Self-Compacting Concrete Strength with Non-Destructive Tests for Concrete Structures

2019 ◽  
Vol 9 (23) ◽  
pp. 5109 ◽  
Author(s):  
Miguel C. S. Nepomuceno ◽  
Luís F. A. Bernardo
Keyword(s):  
Compressive Strength ◽  
Concrete Strength ◽  
Surface Hardness ◽  
Pulse Velocity ◽  
Concrete Compressive Strength ◽  
Self Compacting Concrete ◽  
Coarse Aggregates ◽  
Pull Out ◽  
Concrete Maturity ◽  
Non Destructive

Self-compacting concrete (SCC) shows to have some specificities when compared to normal vibrated concrete (NVC), namely higher cement paste dosage and smaller volume of coarse aggregates. In addition, the maximum size of coarse aggregates is also reduced in SCC to prevent blocking effect. Such specificities are likely to affect the results of non-destructive tests when compared to those obtained in NVC with similar compressive strength and materials. This study evaluates the applicability of some non-destructive tests to estimate the compressive strength of SCC. Selected tests included the ultrasonic pulse velocity test (PUNDIT), the surface hardness test (Schmidt rebound hammer type N), the pull-out test (Lok-test), and the concrete maturity test (COMA-meter). Seven sets of SCC specimens were produced in the laboratory from a single mixture and subjected to standard curing. The tests were applied at different ages, namely: 1, 2, 3, 7, 14, 28, and 94 days. The concrete compressive strength ranged from 45 MPa (at 24 h) to 97 MPa (at 94 days). Correlations were established between the non-destructive test results and the concrete compressive strength. A test variability analysis was performed and the 95% confidence limits for the obtained correlations were computed. The obtained results for SCC showed good correlations between the concrete compressive strength and the non-destructive tests results, although some differences exist when compared to the correlations obtained for NVC.

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