重庆地区装配式建筑物化阶段节能减排效益分析

选取重庆地区量大面广的装配式混凝土建筑为研究对象,基于工程量清单数据,利用碳排放因子法,建立碳排放测算模型,分析不同类型不同装配率建筑在物化阶段较现浇混凝土建筑的节能减排情况。案例分析表明：装配式建筑物化阶段碳排放量为236.11～295.19kgCO₂/m²,较传统现浇混凝土结构体系,建筑碳减排比例为6.04%～8.79%,减排比例随装配率提升及现场预制构件应用的增加而增加;同时,发现建材生产阶段占物化阶段碳排放量最高,可达85%以上,且装配式高层建筑的节能减排效果更加突出。     

纳米SiO2改性粉煤灰混凝土力学性能及吸水特性研究

为了探索粉煤灰混凝土的高性能,开展了纳米SiO₂改性粉煤灰混凝土的力学和吸水试验,研究了粉煤灰取代率和纳米SiO₂掺量对混凝土力学性能(抗压强度、劈拉强度、动弹性模量)和吸水特性的影响。结果表明：粉煤灰混凝土的力学性能指标均随纳米SiO₂掺量的增加先增大后减小;当纳米SiO₂掺量从0%增加至2%时,粉煤灰混凝土28 d抗压强度、劈拉强度和动弹性模量分别提高了12.90%、7.53%和5.85%,可见纳米SiO₂对抗压强度影响更显著;当粉煤灰取代率从10%增加至30%时,混凝土28 d抗压强度、劈拉强度和动弹性模量分别降低了7.24%、2.61%和9.87%,可见粉煤灰对动弹性模量影响更显著;随纳米SiO₂掺量增加,粉煤灰混凝土的毛细吸水系数呈现出先下降后上升的趋势;随粉煤灰取代率增加,混凝土毛细吸水系数增大,且纳米SiO₂对混凝土毛细吸水系数影响也越显著;粉煤灰取代率和纳米SiO₂掺量对混凝土力学性能与毛细吸水系...     

不同性能再生骨料的CO2强化及其碳化率分析

“双碳”背景下，为了加强建筑废弃物的资源利用和减少CO₂气体的排放，利用CO₂强化再生骨料成为主要的措施之一，但CO₂强化不同成分组成和粒径的再生骨料研究相对匮乏。在常温、常压条件下，利用非纯浓度约20%的CO₂分别与不同成分组成和粒径的再生骨料进行碳化作用，并定量表征CO₂强化前后的表观密度、含水率、吸水率和碳化率等参数。结果表明，再生骨料碳化作用后表观密度相对增加，而吸水率和含水率明显降低，与水灰比呈正比；CO₂强化再生骨料的碳化率随再生骨料的水灰比增加而增加，但粒径影响更为显著，粒径越小，碳化率越高，碳化效果好。     

矿粉和粉煤灰对机制砂混凝土力学性能及抗氯离子渗透性能的影响研究

以胶凝材料组成和胶凝材料用量为变量,采用RCM法,测定混凝土的氯离子渗透系数,探究30%矿粉、30%粉煤灰、15%矿粉和15%粉煤灰对机制砂混凝土力学性能和抗氯离子渗透性能的影响。矿粉取代率提升幅度为15%时,机制砂混凝土氯离子渗透系数减少了0.20×10^-12 m²/s;粉煤灰取代率增加幅度为15%时,机制砂混凝土氯离子渗透系数增大了0.05×10^-12 m²/s;当胶凝材料组成为15%矿粉和15%粉煤灰时,机制砂混凝土抗氯离子侵蚀性能最好。     

天然气利用对大气环境及节能减排的贡献

通过对比发电领域、建筑陶瓷领域天然气与煤炭排放量,分析天然气利用对佛山大气环境的贡献以及预测排放量。“十四五”期间,佛山市天然气的总消费量预计为200×10⁸ m³, NO_x、SO₂、烟尘、CO₂减排量分别为20.7×10⁴、75.3×10⁴、17.8×10⁴、5 605×10⁴ t。在发电领域,与燃煤相比,每利用1×10⁸ m³天然气约可减少能源消耗(以标准煤计)5×10⁴ t,万元工业产值综合能耗可降低30%左右。天然气在排放绩效、减排成本、占地面积等方面均优于煤炭,具有较好的环境效益。     

杭州西站枢纽站房建筑全生命周期减碳研究

在碳达峰碳中和的时代背景下,杭州西站作为站城融合的大型交通枢纽客运站,其全生命周期碳排放计算与节能减碳技术的应用分析具有重要意义。通过计算分析,发现杭州西站站房建筑全生命周期碳排放为972.70 kg/m²,其中建筑运行占比74.11%,建材生产占比19.85%,运用节能减排技术,可以实现减碳234.49 kg/m²,总碳排放量下降24.11%,可以产生显著的减碳效果。     

新型低碳胶凝材料制备及CO2养护钙基建筑材料的研究进展

综述硅钙石低碳胶凝材料的制备过程,进而介绍CO₂养护硅钙石胶凝材料、钢渣及混凝土的碳化硬化反应机理,分析养护过程的关键因素,并对低碳、吸碳水泥及CO₂养护技术的未来发展进行展望。     

超轻质混凝土耐久性试验方法探索

干密度≤400 kg/m³的超轻质混凝土(ULWC)具有高孔隙率、超轻质的特点。外界水分、CO₂极易进入ULWC内部,使其因冻融和碳化问题而失效。基于国内外泡沫混凝土(干密度≤1 600 kg/m³)耐久性试验方法的讨论和分析,指出了现有泡沫混凝土试验方法直接用于ULWC耐久性评价时存在的不足,结合试验结果,提出了适用于评价ULWC抗冻性和抗碳化性能试验方法的改进建议。     

CO2碳化矿渣-CaO-MgO加固土效能与机理探索

CO₂碳化联合工业固废协同加固土技术是旨在替代传统水泥固化方法的新型技术尝试。以工业废料——矿渣为主要材料,辅以活性MgO和CaO形成矿渣-CaO-MgO固化体系,将固化土料均匀搅拌制样后进行CO₂碳化试验。通过无侧限抗压强度、扫描电镜和X射线衍射等试验,探究固化剂掺量、配比、碳化时间和初始含水率等因素对碳化加固土效果的影响。结果表明：CO₂碳化对土体加固具有明显改良效果,碳化24 h试样抗压强度最高可提升25.77倍;碳化试样抗压强度与固化剂掺量（6S4L0M除外）、活性MgO占比呈正相关;碳化试样强度随碳化时间先增加后趋于平缓（或略微下降）、最佳碳化时间为6 h左右,随初始含水率增加而先增加后下降、最佳含水率为16%左右;活性MgO碳化效能明显优于活性CaO,矿渣中低活性CaO并不能显著改良自身碳化性能。CO₂碳化作用促使碳酸盐晶体（CaCO₃、MgCO₃）生成,晶体发育程度与碳化时间、固化剂掺量及活性等因素有关;碳酸盐晶体有效填充试样内部孔隙并黏结土颗粒,形成整体骨架结构使试样强度得以大幅提升。     

纳米二氧化硅对橡胶粉再生混凝土坍落度和抗压性能的影响

使用质量取代法研究纳米SiO₂（取代水泥）和橡胶粉（取代天然河沙）单掺和复掺对再生混凝土经7,28 d养护的抗压强度和坍落度的影响。通过试验结果发现：单掺橡胶时,随着橡胶粉掺量增加,再生混凝土的坍落度随之增大,当橡胶粉取代率达到5%时,再生混凝土的坍落度最大;单掺纳米SiO₂时,随着纳米SiO₂取代率的增加,再生混凝土的坍落度逐渐降低,取代率为3%时,再生混凝土的坍落度最小;单掺橡胶粉时,随着橡胶粉取代率的不断增加,经7 d养护的再生混凝土的抗压强度都随之降低,取代率低于5%时,经28 d养护的再生混凝土抗压强度得到提高;单掺纳米SiO₂时,随着取代率的不断增加,经7 d养护的再生混凝土的抗压强度随之增加;两者双掺时,既能弥补橡胶粉掺入强度的降低,又能抑制纳米SiO₂掺入后坍落度变差的缺点,达到互相弥补的作用。并通过扫描电镜对混凝土的形貌、过渡区和水化产物等微观结构进行了分析。     

Prediction on CO2 uptake of recycled aggregate concrete

Carbonation of concrete is a process which absorbs carbon dioxide (CO₂). Recycled aggregate concrete (RAC) may own greater potential in CO₂ uptake due to the faster carbonation rate than natural aggregate concrete (NAC). A quantitative model was employed to predict the CO₂ uptake of RAC in this study. The carbonation of RAC and the specific surface area of recycled coarse aggregates (RCAs) were tested to verify accuracy of the quantitative model. Based on the verified model, results show that the CO₂ uptake capacity increases with the increase of RCA replacement percentage. The CO₂ uptake amount of 1 m³ C30 RAC within 50 years is 10.6, 13.8, 17.2, and 22.4 kg when the RCA replacement percentage is 30%, 50%, 70%, and 100%, respectively. The CO₂ uptake by RCAs is remarkable and reaches 35.8%–64.3% of the total CO₂ uptake by RAC when the RCA storage time being 30 days. Considering the fact that the amount of old hardened cement paste in RCAs is limited, there is an upper limit for the CO₂ uptake of RCAs.     

太原市再生混凝土建筑结构碳排放研究

为了研究中国内陆城市使用再生混凝土替代普通混凝土的环境潜力以便为工程决策提供参考,以山西太原为例研究再生混凝土结构的碳排放。在确定系统边界和分析目标的基础上,根据实地调研与文献数据,确定了太原当地碳排放清单,建立了生命周期评价的基础。根据实际调研得到的混凝土配合比、原材料运输距离等参数,分析太原2个典型混凝土结构分别采用普通混凝土和再生混凝土在骨料生产、水泥生产、运输和填埋过程中所产生的等效碳排放。基于太原当地碳排放清单和选定的边界条件,以典型案例的实际数据为基础,进行运输距离的敏感性分析。结果表明:在采用太原当地碳排放清单、混凝土配合比和运输距离等数据的情况下,相比采用天然骨料混凝土,2个典型结构采用再生粗骨料取代率为100%的再生混凝土等效碳排放可分别降低3.25%和8.39%,且显著降低天然骨料开采及填埋场占用土地,具有较为显著的环境效益; 确定了采用再生混凝土取代天然骨料混凝土具有相对碳排放优势的范围; 天然骨料从矿山运输至搅拌站距离、废弃混凝土从拆除现场运输至填埋场距离以及废弃混凝土从拆除现场运输至再生建材工厂距离的临界值分别为18.3、8.5、18.8 km。     

Carbonation of concrete in the tropical environment of Singapore

The experimental investigation was performed to study the influence of unit cement content and w/c ratio on the rate of carbonation under natural exposure in the tropical environment of Singapore together with laboratory accelerated carbonation test. To represent concrete of lean to rich mixes, the cement content in a total of 21 mixtures was varied from 250 to 450 kg/m³, while the w/c ratios ranged between 0.40 and 0.70 with an increment of 0.05. After 14 years of natural exposure, the 28-day compressive strength (f₂₈) and w/c ratio (w/c) were identified as reliable parameters for estimating the depth of carbonation. However, within the range of values studied, there is no significant effect of the cement content on the carbonation behaviour. The relationship between the 14-year natural exposure and the samples from the 7% CO₂ concentration accelerated test were also correlated. Tentative recommendations on the use of the findings in durability design against carbonation for required service life in a tropical environment are proposed.     

Impacts of climate change on optimal mixture design of blended concrete considering carbonation and chloride ingress

Many studies on the mixture design of fly ash and slag ternary blended concrete have been conducted. However, these previous studies did not consider the effects of climate change, such as acceleration in the deterioration of durability, on mixture design. This study presents a procedure for the optimal mixture design of ternary blended concrete considering climate change and durability. First, the costs of CO₂ emissions and material are calculated based on the concrete mixture and unit prices. Total cost is equal to the sum of material cost and CO₂ emissions cost, and is set as the objective function of the optimization. Second, strength, slump, carbonation, and chloride ingress models are used to evaluate concrete properties. The effect of different climate change scenarios on carbonation and chloride ingress is considered. A genetic algorithm is used to find the optimal mixture considering various constraints. Third, illustrative examples are shown for mixture design of ternary blended concrete. The analysis results show that for ternary blended concrete exposed to an atmospheric environment, a rich mix is necessary to meet the challenge of climate change, and for ternary blended concrete exposed to a marine environment, the impact of climate change on mixture design is marginal.     

装配式建筑施工阶段碳排放测算研究

根据碳排放系数法构建模型,结合工程量清单对装配式建筑施工阶段的碳排放进行测算, 探讨预制率对施工阶段碳排放的影响, 深入探究工程造价、总建筑面积与碳排放总量的关系。以漳州某住宅楼为例, 探讨施工阶段碳排放的排放规律并提出减排路径。 结果表明: 施工阶段的碳排放主要来自一般土建工程;单位面积的碳排放在 671 kgCO2/m2左右波动,单位造价的碳排放在 2749.33 kgCO2/万元左右波动; 混凝土工程和钢筋工程的碳排放随着预制率的升高而增加; 碳排放总量与工程造价、建筑面积存在显著的线性关系。     

青藏高原东缘水库绕坝基渗流化学溶蚀研究

研究了青藏高原东缘某大坝基础遭受渗流场与化学场破坏的过程。通过氯离子示踪、温度电导示踪以及人工示踪方法,确定混凝土防渗墙中存在缺陷,库水通过非全封闭式防渗墙绕坝基渗漏,渗水通过坝后区的反滤层排泄;酸溶解试验和X射线荧光分析证明,坝后区地表的白色颗粒物主要是CaCO_3;结合化学反应过程,确认析出物来自于防渗墙中的水泥,渗漏水中的CO_2与水泥中的Ca(OH)_2发生反应生成可溶性Ca(HCO_3)_2,然后被渗漏水带到地表,并在常温下分解形成CaCO_3。通过地表水中CO_2含量的测试分析发现,参与水岩反应的CO_2具有除大气降水之外的其他来源。结合地质构造推断来自深部碳库中的CO_2通过断裂带进入到了地下水与库水中,并参与了水岩反应,对大坝的侵蚀速度大幅度增加。研究表明深部CO_2进入地下水并参与渗流过程,对大坝及水工建筑物的化学侵蚀作用将大幅度增强。     

基于全生命周期评估与多目标优化的再生混凝土应用研究

为探究再生混凝土在经济和环境上的最佳方案以便为工程决策提供参考,基于全生命周期评估法构建了再生混凝土碳排放量和成本计算模型,并采用 TOPSIS 法对其环境和经济指标进行多目标优化,进而选出满足经济和环境目标的适配性方案。研究结果显示,在整个生命周期中,随再生骨料替代率增加再生混凝土的碳排放量与成本均显现降低态势;水灰比为0.47 再生骨料替代率为 100%的混凝土为最佳方案;若将其性能考虑在内,则水灰比为 0.39 再生骨料替代率为 50%的混凝土为最佳方案。     

CO2 emission consequences of energy measures in buildings

This paper studies the way in which CO₂ emission levels are affected by different measures to reduce energy consumption in a building. A case study is presented which deals with a residential building in Navestad, a suburb of the Swedish city Norrköping. The building is supplied with district heating primarily delivered from a combined heat and power (CHP) plant. Three types of energy measures are studied: extra insulation, new types of window and the introduction of a heat pump. The first perspective is the city of Norrköping, with the system boundary encompassing the residential building and the CHP plants. A second worst case scenario is then presented: a Nordic perspective in which electricity produced in coal condensing power plants is assumed to cover the marginal electricity production. With the former perspective, the measures extra insulation and new windows reduce the CO₂ emissions, and with the latter both measures increase the CO₂ emissions. The measures extra insulation and new windows are ranked, with respect to cost for the first perspective, using a cost reduction curve for CO₂ emissions. In the paper, costs from the ExternE research project are also used.