International Concrete Abstracts Portal

SP-228CD This CD-ROM of Special Publication 228 contains the papers presented at the Seventh International Symposium on the Utilization of High-Strength/High- Performance Concrete that was held in Washington, D.C., USA, June 20-24, 2005. The symposium continued the success of previous symposia held in Stavanger, Norway, (1987); Berkeley, California (1990); Lillehammer, Norway, (1993); Paris, France, (1996); Sandefjord, Norway, (1999); and Leipzig, Germany, (2002). The symposium brought together engineers and material scientists from around the world to discuss topics ranging from the latest applications to the most recent research on high-strength and high-performance concrete. In the years since the first symposium was held in Stavanger, there has been worldwide growth in the use of both high-strength and high-performance concrete. In addition to more research and applications of traditional types of high-performance concrete, the use of self-consolidating concrete and ultra-high-performance concrete has moved from the laboratory to practical applications. This publication offers the opportunity to learn the latest about these developments.

The prediction of concrete properties using computer modeling is becoming widely used, and many models utilize the concept of maturity. The original maturity concept was developed empirically from the study of the temperature effect on the compressive strength of normal-strength concrete. The use of the maturity concept for estimating the development of properties other than compressive strength has not yet been sufficiently validated with experimental data, especially for high-performance concrete. This paper presents a study of the maturity method for predicting the development of key properties of high-performance concrete, such as compressive strength, splitting tensile strength, modulus of elasticity, and level of cement hydration. The derivation of the maturity method is explained and experimental evidence, collected under different temperature conditions, is presented and discussed. The results were used to study the activation energy, which is a governing parameter of the Arrhenius maturity formulation, for predicting the key properties of high-performance concrete. Recognizing the need for a more accurate determination of the activation energy for each concrete property, a new practical approach for calculating the Arrhenius maturity index is proposed.

Mix design and technology of very high strength rapid-hardening concrete (VHSC) on the base of composite cements produced by «intergrinding» (IG) and «interblending» (IB) have been developed, and their characteristic properties have been studied. The use of mechanical-chemical activation of binders in combination with both new generation superplasticizers based on polycarboxilates and traditional ones and efficient dispersed fine mineral additives (silica fume, metakaoline, etc) allows to obtain VHSC. The strength ranged from 50-80 MPa after 24 hours and 125-140 MPa after 28 days of normal curing for self-leveling concrete mixtures (slump value 22-25 cm). Intensive concrete hardening starts after either 10 hours (IG) or 15 hours (IB) from mixing time. With the increase of hardening temperature ranging from 40 to 500C, the induction period decreases by 2-2,5 times, and strength of concrete exceeds 50 MPa in 8-10 hours after mixing (IG and IB, respectively). Volumetric water absorption of coarse aggregate concrete produced with water/binder ratio of 0.24-0.28 amounts to 2.2-3.3%, and that of fine-grained concrete, with water/binder ratio of 0.32-0.39, to 3-3.4%. Waterproofness of such concrete exceeds W20 (water tightness relating to Russian standard testing of cube specimen 150 mm in diameter and 50 mm in height under 2 MPa pressure during 6 hours), and their freezing-thawing resistance surpasses 600 cycles. Physical and mechanical properties (initial modulus of elasticity, tensile strength) are in line with the normal indices for corresponding concrete classes. Shrinking deformations of heavy weight concrete after 28 days of normal curing are 10x10-2 – 17x10-2 mm/m and those of fine-grained concrete are 29x 10-2 – 48x10-2 mm/m.

Chemical attack poses a serious problem for concrete structures in severe environments. This investigation deals with exposure of high strength/high performance concrete to sulfate attack in a controlled environment. Experimental tests consisted of measuring the compressive strength, tensile strength and modulus of elasticity after 3 years of exposure to corrosive conditions consisting of chemical solutions containing 1%(NH4)2SO4 and 2%(NH4)2SO4.

Corrosion of concrete sewer pipes by sulfuric acid attack is a problem of global scope. The current paper aims at evaluating two supplementary cementing materials metakaolin and geopolymer cement as partial cement replacements for improving the ability of concrete to resist severe sulfuric acid attack. Both, metakaolin and geopolymer cement were found to significantly improve the resistance of concrete made of Type 10 and 50E cements to 3% and 7% sulfuric acid solutions (pH of 0.6 and 0.3, respectively). Maximum weight loss reduction with respect to the control for specimens made of modified Type 50E cement ranged between 20% and 37%, depending on the additive and the concentration of the acid. Maximum weight loss reduction for specimens made of modified Type 10 cement range between 10% and 42%, depending on the additive and the concentration of the acid. For this test Type 10 cement was found to perform best in the presence of geopolymer cement while the performance of the Type 50E cement was best when metakaolin was used as partial replacement for cement. The results emphasize the important role that the nature and composition of hydration products and the completeness of the hydration process play in improving concrete resistance to acid attack.