Hydration of the combinations of ground granulated blast furnace slag cements

The heat of hydration is known as a measurement of the initial chemical reactions for the hydration of cement. The heat liberated during the hydration process affects the temperature rise in concrete, which may cause an early-age thermal cracking of a concrete structure. To address this thermal cracking issue, Portland cement/ground granulated blast furnace slag (PC/GGBS) is often used, due to the low heat hydration properties of GGBS. This paper presents the results of isothermal conduction calorimetry tests performed on GGBS binary cement, Portland cement/ground granulated blast furnace slag (PC/GGBS), GGBS ternary cement, and Portland cement/ground granulated blast furnace slag/metakaolin (PC/GGBS/MK). The tests covered a range of GGBS levels, which are up to 75% GGBS level and up to 15% MK content by mass for the ternary cement combinations. For PC/GGBS cement, the total heat of hydration is lower than that of PC, and an increase in the GGBS levels resulted in a decrease in the amount of heat liberated; however, for PC/GGBS/MK, the heat of hydration generated is lower than that of PC but is greater than those of the equivalent PC/GGBS, which has an equivalent PC content

A comparative study of the behaviour of treated and untreated tyre crumb mortar with oil palm fruit fibre addition

An incorporation of waste tyre particles in concrete has been established to produce a green concrete. However, despite its advantages, strength reduction is an obvious handicap. To improve the strength, pre-treatments of the waste tyre particles and addition of Oil Palm Fruit Fibre (OPFF) were chosen and reported in this study. The addition of OPFF was to influence the internal structure in order to improve shrinkage and other strength properties. Performance of the composites in compressive, split tensile and flexural strengths, as well as shrinkage and microstructure were observed. Results showed better behaviour of the treated tyre crumb mortar rather compared to the untreated tyre, with the replacement of up to 40% by volume of the treated tyre crumb particles and 0.5- 1.0% OPFF addition by mass of cement content

Water permeability and chloride and sulphate resistance of rubberised fibre mortar

Non-biodegradable solids such as waste tyres and oil palm fruit fibre (OPFF) would cause environmental problems if not disposed properly. This research studied the water permeability and chloride and sulphate resistance of mixes with addition of OPFF and sand replacement with Treated Crumb Rubber (TCR). The mix known as Rubberised Fibre Mortar (RFM) is a composite of 10% to 30% of TRC and addition of 1% to 1.5% of OPFF. In total sixteen different mixes, with water to cement ratio of 0.48 were prepared and subjected to related tests up to 56 days. The specimens are separated to two water curing types; immersion and spraying. The results show immersion cured specimens is less permeable and more resistance to chloride and sulphate than spraying specimens. The TCR does reduce the water permeability of the mix when 20% and less replacement made, while addition of less than 1% OPFF allows medium permeability. The moderate chloride resistance is achieved in mix with less than 10% TCR replacement and OPFF is not added. While sulphate resistance of RFM with less than 30% TCR is acceptable but addition of OPFF must be limited to 1% to prevent large strength reduction. In conclusion, for indoor mortar applications such as partition wall, RFM made of less than 10% TCR and less than 1% OPFF is recommended

Waste glass as partial replacement in cement – a review

The industries of Cement and glass are dealing with a variety of demanding situations due to the excessive factories gases emissions, the extensive use of power and the intensive use of the earth's natural resources. The temporary landfills of dumping waste glass are now not providing a friendly environment, because of waste glass particle are nonbiodegradable. Furthermore, the chemical structure and the pozzolanic characteristics of waste glass are inspiring for using this waste in the cement industries and urban industries and to provide an environmentally friendly answer for the glass and cement industries. Thus, it can be used as a partial cement replacement in Portland cement concrete or as a partial replacement in the form of waste glass powder (WGP) or as waste glass sludge (WGS). The use of glass powder in Portland cement concrete does have some negative impact on characteristics of the concrete; however, waste glass in its crushed condition can be use in about 100 % and it can still be a practical applicability. This paper reviews the unusual uses of waste glass in cement and concrete and the effect of thermal and pozzolanic activity on the properties of waste glass the impact of the glass characteristics on the durability and performance of the produced cement and concrete

Study of properties and strength of no-fines concrete

Nowadays, special concrete is widely adopted in construction industry. No-fines concrete is a one of the special concrete which eliminate the use of fine aggregates in concrete mixing. The application of no-fines concrete has been introduced to construction industry especially pavement construction. Due to its high porosity behavior, the relative density of no-fines concrete is lower than normal concrete of 2400kg/m3 which also helps in reducing dead weight in the design. In term of strength, no-fines concrete also gave lower compressive strength compared to normal conventional concrete. The aggregate/cement ratio also found to be a factor affecting its strength as it is depending on the interlocking or the strength of bonding between aggregate and cement. Also, concrete with varies mix ratio gives different has been studied for its physical and mechanical properties. In addition, there are further study of introducing fiber materials to determine the chance of enhancement in no-fines concrete study. By elimination of fines aggregates, the development and application of no-fines concrete in the construction industry will be more economical than normal concrete. This paper reviews and studies the performance characteristics and strength of no fine concrete based on previous researcher's outcome

Mechanical properties of concrete with coconut shell as partial replacement of aggregates

Coconut shell is one of the most prevalent agricultural solid wastes in several tropical countries. For coconut shell aggregate to be used efficiently for construction purposes, the mechanical properties are essential. Therefore, this study examined the effect of coconut shell as fine and coarse aggregate replacement in concrete with respect to the mechanical properties. The coconut shell concrete was designed for the characteristic strength of 30 MPa with the incorporation of coconut shell as a replacement for fine and coarse aggregate at 10%, 20% and 30% by weight respectively. The compressive, flexural, tensile strengths, as well as densities and water absorption of 96 cured concrete samples, were evaluated at 7, 14, and 28 days. The results showed that increases in replacement of coconut shell volume fractions will increase the workability and water absorption of the mixtures but will decrease the mechanical properties of the concrete

Finite element analysis of proposed self-locking joint for modular steel structures

The intermodular connection between modules plays a vital role in the overall performance of modular structures. The separation between a column and connection is possible due to the absence of links (welding or bolting) since limited space is available between modules. This study proposed a self-locking joint to be used in a modular steel structure, connecting columns with a connection without need of extra space between modules. The behavior of the proposed connection subjected to monotonic load was evaluated using a finite element approach using ABAQUS software. The influencing factors contributed to the behavior of the self-locking connection and columns observed using a parametric study. The parametric study was conducted by varying beam thickness, bolt pretension force and friction coefficient µ. Results indicate that the proposed connection can be classified as a semirigid connection according to Eurocode 3 and special moment frame (SMF) as recommended by AISC

Evaluation of calcium carbonate precipitation by Bacillus spp. isolated from stingless bee products

Microbiologically Induced Calcium Carbonate Precipitation (MICCP) through urea hydrolysis is the most effective way to precipitate a high concentration of calcium carbonate (CaCO3) within a short time. The MICCP process is used to remediate the micro-crack in the concrete. However, limited research has been conducted to determine CaCO3 precipitation by bacteria, especially in Malaysia. Here, Bacillus spp. isolated from the Malaysian stingless bee products were evaluated for CaCO3 precipitation. Bacillus spp. were selected for further study according to their ability to produce urease enzymes. The urease-positive Bacillus spp. were screened for CaCO3 precipitation by culturing on both CaCO3 precipitation agar and broth media. The survivability of the urease-positive Bacillus spp. in various temperatures, pH values, and NaCl concentrations were tested. Seven out of 11 Bacillus spp. were found as ureolytic bacteria. Among the ureolytic bacteria, bacteria belonging to the Bacillus subtilis species complex group showed the highest number of bacteria (36.4%) that are capable of precipitating CaCO3. Bacillus stratosphericus PD6 and B. aryabhattai BD8 exhibited the largest CaCO3 precipitation zones (15 mm). Bacillus stratosphericus PD6 also precipitated the highest amount of CaCO3 (65 mg) and urease activity (0.197 U/mL). All the urease-positive Bacillus spp. were able to grow at 45 °C, pH (8 to 12), and 5% NaCl. Only B. subtilis BD3 can withstand high temperatures up to 55 °C and 15% NaCl concentration. In conclusion, Bacillus spp. isolated from stingless bee products showed the ability as the CaCO3 precipitating bacteria; suggesting its potential application in self-healing concrete

Evaluation of the compatibility of modified encapsulated sodium silicate for self-healing of cementitious composites

Healing agent carriers play a significant role in defining the performance of the autonomous self-healing system. Particularly, the ability to survive during the mixing process and the release of the healing agent when cracks occur without affecting the mechanical properties of the cementitious composite. Up to now, these issues are still a concern since glass capsules are unable to survive the mixing process, while some types of microcapsules were reported to cause a decrement in strength as well as limited strength recovery. Therefore, this study was twofold, addressing the surface treatment of polystyrene (PS) capsules and the evaluation of the compatibility of the modified capsules for cement-based applications. Secondly, assessing the healing performance of modified PS capsules in cementitious composites. Furthermore, the study also evaluates the potential healing performance due to the synergic effect between the encapsulation method and the autogenous self-healing mechanism. The investigation was carried out by measuring the changes in the pH of pore solution, FTIR analysis, survival ratio, and bonding strength. For self-healing assessment, the compression cracks on the cement paste were created at an early age and the strength recovery was measured at the age of 28 and 56 days. To identify the chemical compounds responsible for the healing process, SEM-EDX tests were conducted. Moreover, the effect of silica fume (SF) on bonding strength and self-healing was also evaluated. Based on the results, the modified PS capsules by roughing approach showed promising performance in terms of survivability, bonding, and recovery. The modified PS capsule increased the strength recovery by about 12.5–15% for 100%OPC and 95%OPC + 5%SF, respectively. The finding observed that the combining of modified PS capsules and the inclusion of SF gave high strength recovery of about 20% compared to 100%OPC without capsules. Thus, the modified PS capsule has a good potential for self-healing of cementitious-based applications

Effect of metakaolin on early strength of GGBS ternary concrete

The article reports a laboratory experimental programme that investigated effect of metakaolin on the early strength of concrete made with ternary combinations of Portland cement (CEM I) with ground granulated blast slag (GGBS) and metakaolin (MK). The various level of cement combinations (65%CEM I+30%GGBS+5%MK, 45%CEM I+45%GGBS+10%MK and 45%CEM I+40%GGBS+15%MK) was examined in comparison to CEM I and equivalent GGBS binary concretes for up to 28 days. Results show that the reduction in early strength is greater with the higher cement replacement level. However, the ternary concrete containing 15%MK has minor increase in early strength compared to those with 10%MK but a significant increase in strength is examined at later age (28 days). It is concluded that the presence of MK compensates the adverse effect of GGBS at early strength development and improves the strength at later ages