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  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

Showing 1-5 of 797 Abstracts search results

Document: 

SP-349_17

Date: 

April 22, 2021

Author(s):

Hugo Valido Deda, Leandro Francisco Moretti Sanchez, Mayra Tagliaferri de Grazia

Publication:

Symposium Papers

Volume:

349

Abstract:

Although the 28-day concrete compressive strength is often used as a quality control indicator, early-age mechanical properties are becoming more critical to optimize construction scheduling. Numerous advanced techniques have been proposed in this regard and among those, electrical resistivity (ER), a non-destructive and inexpensive technique able to characterize the microstructure development of cementitious materials has been showing promising results. Yet, recent literature data have evidenced that ER might be significantly influenced by a variety of parameters, such as the binder type/amount and aggregates nature used in the mix. These factors can hinder the practical benchmark of concrete mixtures proportioned with distinct raw materials. Thus, six concrete mixtures incorporating two types of aggregates (granite and limestone) and two ground granulated blast furnace slag cement replacements (e.g. 0%, 35%, and 70%) were manufactured for this research. Moreover, three distinct ER techniques (e.g. Bulk, Surface, and Internal) and compressive strength tests were performed at different concrete ages. Results show that the binder replacement may significantly affect ER results over time, whereas the aggregate type presented a less significant impact.


Document: 

SP-349_16

Date: 

April 22, 2021

Author(s):

Hocine Siad, Mohamed Lachemi, and Mustafa Sahmaran

Publication:

Symposium Papers

Volume:

349

Abstract:

This paper studies the use of a new preconditioning process for an accelerated testing of concrete resistance against sulfate attack. For this reason, concrete specimens were subjected to a part by part pre-saturation method using a concentrated sulfate solution drained inside desiccators. This preconditioning technique was applied before exposing the specimens to different immersion conditions in 5% and 10% sulfate solutions, and to storing at high temperature and to wetting/drying cycles. Length change measurements and sulfate penetration profiles were performed on normal and high strength concretes. In addition, SEM-EDS analysis were used to investigate the type and amount of degradation products in the core layer of samples exposed to accelerated testing. The new pre-saturation method highly accelerated the degradation of concrete samples exposed to different immersion conditions. The microstructural observations showed advanced depths and greater amounts of gypsum and ettringite within the degraded specimens subjected to the primary preconditioning stage. However, the real field observations were only achieved when combining the pre-saturation method and the immersion in 5% sulfate solution.


Document: 

SP-349_36

Date: 

April 22, 2021

Author(s):

Emmanuel Guillon and Catherine Bouillon

Publication:

Symposium Papers

Volume:

349

Abstract:

The industrialization of Super Sulphated Slag Cement requires a strict control of the activation of slag. Optimal activator content is a compromise between early age and long term strengths. In particular, an excessive activator dosage leads to a strong decrease of final strength that could lead to non-conformities. Thanks to the coupled use of mechanical testing, SEM and isothermal calorimetry, this paper provides a clearer insight on how SSSC reacts. It is shown that excess of activation impacts mechanical strength twofold. First, it is observed after one or two days of hydration a decrease of hydration kinetics that could be attributed to a denser or thicker hydrate layer around slag particles. Second, overactivated SSSC exhibit heterogeneous porosity including defects that leads to a decrease of strength and lower mechanical efficiency. Finally, this paper highlights that the increase of strength observed when using hemihydrate is mainly due to the improvement of hydration kinetics, more than a gypsum setting effect.


Document: 

SP-347_07

Date: 

March 1, 2021

Author(s):

Andrew D. Sorensen, Robert J. Thomas, Ryan Langford and Abdullah Al-Sarfin

Publication:

Symposium Papers

Volume:

347

Abstract:

The impact resistance of concrete is becoming an increasingly important component of insuring the durability and resilience of critical civil engineering infrastructure. Design engineers are not currently able to use impact resistance as a performance-based specification in concrete due to a lack of a reliable standardized impact test for concrete. An improved method of the ACI standard, ACI 544.2R-89 Measurement of Properties of Fiber Reinforced Concrete, is developed that provides a resistance curve as a function of impact energy and number of blows (N) to failure. The curve provides information about the life cycle (N) under repeated sub-critical impact events and an estimate of the critical impact energy (where N=1), whereas the previous method provided only a relative value. The generated impact-fatigue curve provides useful information about damage accumulation under repeated impact events and the effectiveness of the fiber-reinforcement. In this paper, the improved method is demonstrated for three fiber types: steel, copolymer polypropylene, and a monofilament polypropylene. Additionally, the analytical solution for the specimen geometry is given as well as the theoretical considerations behind the development of the impact-life curve. The use of a specimen geometry provides a path to generalize the test results to full-scale structures.


Document: 

SP-347_10

Date: 

March 1, 2021

Author(s):

Grace Darling, Stephan A. Durham, and Mi G. Chorzepa

Publication:

Symposium Papers

Volume:

347

Abstract:

Concrete median barriers (CMB) are installed to decrease the overall severity of traffic accidents by producing higher vehicle decelerations. In 2016, an update to the AASHTO Manual for Assessing Safety Hardware (MASH) saw a 58% increase in impact severity of test level 4 (TL-4) impact conditions when compared to the NCHRP Report 350 testing criteria. This study investigates the use of fiber-reinforced rubberized CMBs in dissipating the impact energy to improve driver safety involved in crashed vehicles. Two full-scale barrier prototypes with shear keys were constructed and tested under impact conditions in a laboratory setting. Compared to the Georgia Department of Transportation specified single-slope barrier, the fiber-reinforced rubberized concrete mixture, a design with 20% replacement of the coarse aggregate by volume with recycled rubber tire chips and a 1.0% steel fiber addition, was evaluated based on its performance in toughness, energy absorption capacity, and its recoverable deformation. It is concluded that the TC20ST1 barrier performed as well as the control barrier at the impact load of 150.0 kips (667.2 kN), with neither barrier experiencing any visible damage.


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