ACI Global Home Middle East Region Portal Western Europe Region Portal
Email Address is required Invalid Email Address
In today’s market, it is imperative to be knowledgeable and have an edge over the competition. ACI members have it…they are engaged, informed, and stay up to date by taking advantage of benefits that ACI membership provides them.
Read more about membership
Learn More
Become an ACI Member
Topics In Concrete
Home > Publications > International Concrete Abstracts Portal
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.
Showing 1-5 of 38 Abstracts search results
Document:
SP302-28
Date:
June 1, 2015
Author(s):
Christof Schroefl and Viktor Mechtcherine
Publication:
Symposium Papers
Volume:
302
Abstract:
Water desorption from superabsorbent polymers (SAP) into cement-based pastes was characterized by neutron radiography imaging to promote the understanding of the mechanisms behind internal curing of concrete. Two anionic SAP samples were used which differed in their inherent sorption kinetics in cement pore solution (SAP 1: self-releasing; SAP 2: retentive). Portland cement pastes with W/C of 0.25 and 0.50 and a paste additionally containing silica fume (W/C = 0.42, SF/C = 1/10) were investigated. Desorption from SAP 1 initiated immediately. SAP 2 released water into all the matrices as well, even in the cement paste with the high W/C of 0.50. In the other two pastes, which require internal curing by principle, SAP 2 retained its stored liquid for as long as the dormant period of cement hydration. Intense desorption then set in and continued throughout the acceleration period and even beyond. These findings explain the pronouncedly higher efficiency of SAP 2 as an internal curing admixture when compared to SAP 1.
DOI:
10.14359/51688110
SP302-29
Serina Ng and Harald Justnes
The dispersing effectiveness of three polycarboxylate-based superplasticizers (PCE) was investigated in two blended cement systems containing entirely different SCMs; fly ash (FA) and calcined marl (CM) at replacement percentages of 20% and 60%. The methods of investigation employed include rheological studies, hydration profiling up to 24h, and packing density analysis. Generally, replacing clinker phases by FA decreased the dynamic yield stress and delayed hydration of the pastes due to increased PCE to clinker ratios, regardless of PCE type. Little variation except for cement with 60% FA replacement (FA60) was observed on the Bingham viscosity. On the other hand, CM competed with clinkers not only for water, but also for PCEs even in CM20, reducing the fluidity of the paste but maintaining a similar initial rate of hydration of the pastes. PCE possessing intermediate side chain lengths proved to be more effective for CM systems than PCEs possessing long side chains.
10.14359/51688111
SP302-25
Weishan Wang, Zuiliang Deng, Zhongjun Feng, Lefeng Fu, and Baicun Zheng
Interaction mechanisms of polycarboxylate-based superplasticizer (PCE) and poly(vinyl alcohol) (PVA) with bentonite were systematically investigated. The adsorption of PCE onto bentonite in aqueous solution was carried out, and changes in the surfaces and microstructures of the resultant PCE/bentonite complex were characterized by FTIR, XRD, TGA and HRTEM. The results indicated a large adsorption amount of PCE onto bentonite ranging from 157 mg/g to 230 mg/g. The interlayers of bentonite were intercalated by PCE molecules with some surface adsorption. PVA adsorbed onto bentonite competitively with PCE which decreased the adsorption amount of PCE drastically. Cement mortar experimental data showed ether-based PCE had better clay tolerance than ester-based PCE. PVA as sacrifice agent can enhance the dispersibility of PCE for cement with clay.
10.14359/51688107
SP302-26
Camille Nalet and André Nonat
The difference in the retarding effects induced by sugar alcohols on the hydration of pure tricalcium silicate and white cement pastes is investigated. The polyols studied which are stereoisomers (D-glucitol, D-galactitol and D-mannitol) generate a lower retarding effect on the hydration of white cement than on the hydration of pure tricalcium silicate. The presence of aluminate and sulfate phases in white cement pastes is shown to reduce the retarding effect induced by the molecules. Moreover, these alditols strongly complex aluminate in solution and adsorb on hydrating cement. The interactions of polyols with the anhydrous and/or hydrated aluminate phases and their effects on the hydration kinetics of white cement are discussed.
10.14359/51688108
SP302-27
Franz Wombacher, Christian Bürge, Emmanuel Gallucci, Patrick Juilland, and Gilbert Mäder
One of the main problems associated with supplementary cementitious materials (SCMs), which are used as clinker or cement replacement, is the slow strength development compared to pure OPC. This is especially evident in the early stages of cement hydration and may cause significant problems for the customers. Therefore, the demand for new and powerful accelerators only having a marginal influence on the workability of the concrete, is rising. These types of accelerators may find their application in normal ready-mixed concrete but, much more evident, in precast applications. In this paper, a new accelerator is presented, which can significantly improve the early strength (up to 2 days) of concrete. In addition to this, the components of this new approach do not bear any potential risk of corrosion for steel, be it normal reinforcement or prestressed steel.
10.14359/51688109
Results Per Page 5 10 15 20 25 50 100
Edit Module Settings to define Page Content Reviewer