Abstract
An estimate shows that approximately 50% of global annual construction activities account for the repair and retrofitting of structures and constructed facilities. Therefore, structural rehabilitation and repair are becoming hot topics among researchers, in order to find innovative and comprehensive solutions. Ultra-high-performance concrete (UHPC) is designed to achieve high strength and long-term durability. Such types of concrete offer a solution for complicated repair and retrofitting jobs. Although many benefits of using UHPC have been derived, many concerns have also been identified with the use of UHPC—sustainability is considered a critical concern due to the requirement of large proportions of cement, which results in an increase in cost and environmental impacts. This paper presents a recipe for UHPC that contains a small ratio of cement and a large proportion of fly ash, i.e., up to 50%, as a cement replacement material (CRM). In order to achieve long-term durability and increase bonding with old concrete or brickwork for repair and retrofitting purposes, ultra-fine calcium carbonate (UFCC) is also added. In selecting an appropriate material for structural repair, it is essential to acquire an understanding of the material behavior. Therefore, this research was focused on providing a comprehensive guide to the behavior and strength performance of UHPC. The experimental results have shown that the highest strength of UHPC with low cement content can be achieved using a binary combination of high-volume fly ash (HVFA) and ultra-fine CaCO3 (UFCC) as a substitution for cement by up to a ratio of 50% in the recipe. The UHPC with low cement content displayed excellent repair and retrofitting potential for structural strengthening in regions of high stress by developing a strong bond with the existing concrete substrate.
Highlights
The Transportation for America Report [1] highlighted that in the last four decades, a total number of 607,380 concrete bridges were found to be structurally deficient
This study aimed to develop a green, sustainable, and cost-effective Ultra-high-performance concrete (UHPC) mix for possible application as a high-performing repair material
Compressive Strength Test As the first objective of this research was to achieve high compressive strength of the UHPC using low ceAmsentht ecofnirtsetnotbajnedctiHveVFoAf tfhoirs croemsepalrycihngwwasitthothacehaisepvierahtiigohn fcoormsupsretasisnivaeblsetrdeenvgetlhopomf ethnet gUoHalPs.C HuVsFinAgwloaws sceelemcteendtbcaosnetdenotnaanvdaHrieVtFyAoffboernceofimtspelyxpinegriwenicthedthbeyamspaniryatrieosneafrocrhseursst:aiitnraebdluecdesevtheelowpamteernt degmoaalns.dH, iVmFpArowvaess stehleecwteodrkbaabseildityo,nmainvaimrieiztyesotfhbeetnheefritms aelxpcrearcieknincegdabnyd mdrayniyngressherairnckhaegrse:,irterdeudcuecses thtehechwaantceersdoefmraenindf,oirmcepmroevnetsctohrerowsioornk,aabnildityc,omntirnoilms iszuelsfathteeathttearcmk aalncdraaclkkianlgi-sainlidcaderyxipnagnsshiornin[k4a2g].e, Figure 5 shows the results of the compressive strength and pozzolanic strength index (PASI) of all concrete mixes determined at the age of 7, 28, and 90 days
Summary
The Transportation for America Report [1] highlighted that in the last four decades, a total number of 607,380 concrete bridges were found to be structurally deficient. Developing reliable and cost-effective repair materials that show high durability and comply with functional requirements is quite challenging [7]. The application of high-performance materials and innovative techniques plays a vital role in developing mechanical strength and enhancing the integrity and durability of the rehabilitated structure. For placing a concrete overlay on the old concrete substrate, concrete structures need homogeneity and continuity in the load flow pattern [20] In this case, if the new concrete overlay develops low bond strength with the old concrete, a weak link in the repaired system will form, which requires an engineered solution [8,20]. This study aimed to develop a green, sustainable, and cost-effective UHPC mix for possible application as a high-performing repair material. The principal objective of the experimental study was to determine the optimum replacement of FA-UFCC in UHPC and to assess the characteristics of the optimum mixes as a high-performance repair material
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